Unreliable tooling is annoying - Schaublin Ep.62 || RotarySMP

Don't use triangle inserts to make a dovetail cutter. Triangle inserts like these TCMT 110202 have two issues:
1/ being 60°, they always engage, or at least rub on the bottom, sliding the insert along it's rear guiding edge.
2/ there is only one edge to locate the insert in it's pocket, and that is not rigid enough.
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____________________
00:00 - Intro
01:09 - Need more tool holders for the lathe
01:47 - Luke prepared the blanks in Malta
02:32 - Why did Schaublin do this?
03:01 - Milling the dovetails.
03:48 - Oops - it moved.
05:28 - Adjusting the dovetail size.
08:33 - Oops - ringlight fell off.
10:22 - Oops - the DIY dovetail cutter failed.
13:49 - Loctite?
15:49 - Maho montage
18:04 - Failed again
_____________
Music:
Far West - Thunder
iTMR - Get Gone
LUMINAR - Moving Slow
Philip Logan - She Was Alone
Russo - All or Nothing
sero - Letting Go
Sponj - Arnold
YAHYAH - Jupiter Calling
Ziv Moran - No Favors

[@iancrozier8068]

Someone once said "the man who never made a mistake has never made anything" So well done for the effort and the vid, I will look forward to your solution to this hiccup.

[@RotarySMP]

Thanks Ian. The next cutter will have pocket to better support the insert.

[@JustinDavidow]

Proven bad ideas are just as valuable as proven good ideas. Both are better than any unproven ideas!

[@RotarySMP]

Thanks Justin. My next one will hopefully be better.

[@hinz1]

Likely because there is no pocket for the insert, to take the cutting force. So screw gets all the shearing force during cutting. A small pocket, maybe 1/3 width of insert, on top, to take the upwards cutting force would help a lot. I'd put some copper spaceholder into insert place and make a small pocket replacement with TIG welder, so insert could not move upwards any more.

[@RotarySMP]

Yep, that is the problem. Should work much better with DCMT in a pocket.

[@hugobiddlecombe504]

That would save heaps of time to just tig on a shoulder to make an insert pocket, nothing wrong with the inserts (yet)

[@RotarySMP]

@@hugobiddlecombe504 The way I weld, that is not the most likely outcome ;)

[@chrisstephens6673]

A smaller depth of cut might have reduced the problem, but the trouble with a triangular insert means you have a very large cutter contact, don't forget the lower edge is in contact all the time. When I made one yesrs ago I angled the insert very slightly so the lower edge doesn't rub, but the problem is the dovetail isn't 60 and I couldn't be bothered to do the calculation for the offset to make it right. If you are making both male and female it doesn't matter about exact angle, but I can always use a proper dovetail cutter after bulk is removed.

[@RotarySMP]

@@chrisstephens6673 Tht is why the next one I make will used DCMT's. They are only 55° nose angle, so the bottom will have clearance, and also will make that cutter with proper pockets to support the insert on two sides.

[@philhermetic]

It looks like the insert has to fit to the shoulder with absolutely zero clearance, or perhaps even a tiny bit of interference. It is noticeable that the commercial insert pockets have two locating faces. Cutting forces on the insert are going to be large and any clearance will allow the insert to move and loosen/ shear the fixing screw. You can’t win em all! Phil

[@RotarySMP]

Hi Phil, yeah that is the conclusion I also came to... belatedly ;)

[@AJBtheSuede]

That's what I thought too, and also the seating face needs to be either ground absolutely flat or even slightly concave to make sure there's no rocking forces exerted on the insert. In any transient mechanical load, even microns of movement or rocking will kill longevity. In a home shop I'd probably try concave (a few hundredths of a relief pocket that doesn't reach the insert outside pressure edge.

[@404BYTE]

That explains why a proper TCMT holder have two side of pocket, backing the insert against the cutting force. Very informative video.

[@rok1475]

If you ever find an indexable dovetail cutter using triangular inserts with that “proper” insert seat, do share that info.

[@RotarySMP]

Yep, that is the essential design flaw.

[@steveggca]

@@rok1475 dorian d60x series dovetail cutters . of course it has an insert with a slot on the bottom and a key on the holder

[@kbye5323]

Honestly love the fact you didn’t sugarcoat the failures. Love the channel!

[@RotarySMP]

Thanks for your kind feedback.

[@alanclarke4646]

First question is easy to answer: i don't currently have a lathe, therefore i have no tool holders 😂😂 Edit: therefore the second question is also easy to answer: I have EXACTLY the number of tool holders I need. 😂😂

[@RotarySMP]

Seems like you need a lathe... or three ;)

[@christopherleveck6835]

​@@RotarySMPyou should have asked how many lathes we have ..... And how many are usable. I collect lathes. And they start out as barn finds mostly. Mostly. I have 7 projects, 5 working lathes, and 4 totally restored for a total of 16? Can't do the math. It's late and I'm sure I've forgotten a couple. My favorite is a Hendey 9" precision tool and gage lathe. The very last one EVER built. It needs A LOT of work.

[@alanclarke4646]

​@@RotarySMPI need to make space in my shed first ( on going project that started several years ago😂😂😂 )

[@Gin-toki]

I was going to comment the exact same! xD Although I would love to have a lathe :)

[@user-ru3im9rd6b]

​@christopherleveck6835 I have 5 lathes, 2 function and 4 mills, 1 functions. 3 cnc are broken, the manual mill works! I use CXA holders for my 2 working lathe. They are in different states. I have about 10 holders each. I'm not happy with my tool selection. I always seem to have the wrong insert style , especially for threading. I have more tools than I have holders, and seems like fewer tools than I need to complete a job. Doesn't help having stuff in separate states. The tool I need is always in the other state

[@vandyFixer]

You made the right choice carrying on using locktite. You now have a decent number of tool holders to be going on with while you come up with an other solution for the remainder. I'm looking forward to next weeks video, regardless of what the content is.

[@RotarySMP]

Thanks for you support.

[@helsing7423]

That ringlight situation was handled really poorly in my opinion. Grabbing a loose part around a turning, independently moving spindle is a great way to lose a finger, and not commenting on it just makes it seem normal. Not putting my hands near a turning spindle is literally the first safety rule i learned. Please just hit the E-stop the next time. On a manual lathe 5 to 6 toolholders are sufficient for me: 1 for facing and turning, 1 for chamfers, one for grooving, 1 boring bar and 2 for miscellaneous like knurling or form tools. On my CNC at work i had a roughing and a finishing tool for facing and turning, but the chamfering tool wasn't needed, so still 5-6 + 1 or 2 chucks for drills, because the tailstock was only for support.

[@RotarySMP]

Good call. It helps to have these safety inputs when working alone.

[@JaenEngineering]

I think the optimum nimber of tool holders is quite simple. Its the number of tools you currently have plus however many tools you'll think you'll need. 😅

[@RotarySMP]

Good call.

[@lumotroph]

Nice math rock at the 10-minute mark!

[@RotarySMP]

Glad you enjoyed it.

[@dougbriggs6797]

I have 10 tool holders and I need ... more.

[@RotarySMP]

Thanks Doug, that sounds familiar.

[@JCWren]

I know I have at least 6 tool holders. I found the deal of the century on a package that includes a Precision Matthews PM-1440E-L, a PM-940M-PDF mill that's been converted to CNC, MSC SGS-618M surface grinder, small tool grinder, and a granite plate. There are 7 jaws, at least 4 vises, a full 5C collet set, angle plates, an indexer, and both an imperial and metric butt load of end mill bits, side milling bits, and other stuff I haven't catalogued yet. Also about 200 pounds of aluminum plate, rod, and bar stock. Previous owner bought the lathe and mill new and it's very lightly used. He machined only aluminum, Delrin, and nylon. My effort now is finding a rigging company to move it. I'm super pumped about this :)

[@RotarySMP]

That sound like instant home shop set up. Nice find JC.

[@JCWren]

@@RotarySMP Thanks! Pure luck, and only about 50 miles from me. Next I'll have to figure out what the heck I'm doing :)

[@RotarySMP]

@@JCWren Or start a YT channel. Then there is no need to know what you are doing...look at me :)

[@dwegmull]

The correct number of tool holders is one more than you already have...

[@RotarySMP]

Yeah, that sounds familiar. :)

[@Imbmechanicaldesign]

Another option might be to re-drill the holes and tap with an STI tap and install a locking helicoil insert. Also torquing the screws will help.

[@RotarySMP]

I dont think improved fastening will be enough, as it does not address the fundamental design error of having only one edge to locate the insert, while having two edges in engagement.

[@joansparky4439]

Robrenz made a video about insert pocket design/making some years ago with all the details: "making an insert boring bar"

[@RotarySMP]

Thanks for the link Joan.

[@blunderchips]

Wow this is a great idea. I think I'll copy that.

[@RotarySMP]

You mean the cutter design? Not a great idea.

[@jeanbarbier9448]

If it were not for the fundamental sin of being 60°, I would have suggested to braze the insert on an intermediate (mobile) plate transferring the efforts into an ah-hoc pocket. As it is I agree that the only sane way is to change insert type. Thanks for showing me that it was a very good bad idea... (I thought to do the same) Jean

[@RotarySMP]

Glad to save you the effort of trying this Jean :)

[@MgBaggg]

N, and i need N+1

[@RotarySMP]

Well summarised.

[@stevensmart8868]

Same is true for motorbikes,bicycle and guitar and cameras I'm lead to belive.

[@RotarySMP]

@@stevensmart8868 My four guitars and about 10 cameras fit into that scheme :)

[@NorroTaku]

seeing a german living in ozzie landblo2s my mind every time😂😅 good on ya on leaving this hole for greener pastures

[@RotarySMP]

? I am a Kiwi living in Austria :)

[@mechaform]

Thanks for your extensive testing and honestly sharing the mode of failure. Very informative.

[@RotarySMP]

Glad it was helpful! The next one will be better.

[@steveggca]

Hi Mark, almost success ! I "believe" that the guiding principal of indexable inserts is that the screw is there just to keep the insert from falling off when sitting on the shelf😉 , and that all of the cutting forces are absorbed by the pocket.

[@RotarySMP]

Hi Steve, yeah the next one will be DCMT with a proper pocket.

[@jdmorgan82]

@@RotarySMP so something I saw when you were making the tool, and made a mental note of, was that you were using the screw to push the insert against the tool. (Maybe this has been said already) I'd make the next one centered. That's what caused your screws to break... well amongst other things I guess. But it certainly didn't help. On a different note, I don't suppose I could talk you in to doing a video on the process of machining with FreeCAD could I? Since you're designing a new tool and all....

[@MF175mp]

​@@jdmorgan82 that's how they're commonly designed. A centered screw doesn't seat the insert properly.

[@MyMiniHomeWorkshop]

You live and learn and as I've always said, if you don't have a go, then you will never know. 👍

[@RotarySMP]

Yeah, that next one is hopefully a better design, better executed.

[@andypughtube]

The answer is, if you have N toolholders, then you always need N+1. Because you can guarantee that whichever tool you take out to put in a tool for a specific job, that will be the tool you need for the very next operation. Currently I have 13 Multifix size A holders.

[@RotarySMP]

Hi Andy. Yeah, even with the 18 holders, there was always the need to change something out.

[@mandrakejake]

You seem to have a very knowledgeable viewers 😊 I'd take that as flattery since they wouldn't be interested unless your content was interesting, which it is!

[@RotarySMP]

Thanks Jake.

[@Woodnsmoke]

Your main problem is most likely not the threads coming loose but the screws stretching - hence why they break so often. All the cutting forces are taking up by the screw, scince the cutting only happens at one side of the triangle, shifting the inserts over to the center of the cutter (and down - did you check if the dovetail became lower when the inserts loosened up?) I think the Cutter would work if you brazed the inserts on - or you design one as shown with s pocket that contains the insert on two edges 😅 Thanks for sharing though, takes some courage to share the fails too! Looking forward to the next one!

[@RotarySMP]

Yeah, brazing was tempting, should have done that instead of glue. The next one will have DCMT, and proper supporting pockets.

[@alan-sk7ky]

silver solder them in with the screws in to keep the inserts where they should be.

[@RotarySMP]

That would have worked, before I broke off screws in 3 holes :/

[@OddsandEndsMachining]

I’m envious of your collection. I’ve just got one of the standard 4 tool fixed height jobbies. I keep telling myself I need to upgrade it, but I never get around to it. I would like to have maybe 6-7 tool holders minimum.

[@RotarySMP]

I got sick of the four way holder pretty quickly. Seemed to be constantly setting tools to center height.

[@cho4d]

woooh i am now a lathe owner. old harrison from the 40s. i have no quick change tool holders because i don't have a quick change tool post. but i do have a lathe. yahooo :D

[@RotarySMP]

A lathe is such a cool tool.

[@kenfarrell9531]

Tool holders are so fast. Get one as soon as you can, not too small, you want it ridged

[@MF175mp]

It's great that you can admit the shortcomings of the self made dovetail cutter. I made one too a few years back and came to the same conclusions. Most people would insist that it's good and that the operator is at fault. Same goes for the absolute cheapest and worst lathe tool sets that only seat with one side of the insert in a similar fashion.

[@RotarySMP]

I also started off with that lathe tool set. They really are crap, although last a bit longer as a lathe only has one side of the insert in engagement. Once I make the replacement cutter, hopefully implementing all I have learned, I will make a video in it.

[@endrekalvenes8460]

You could clean up all the surfaces and then silver solder the inserts in place and then if you need to rotate the inserts just desolder and solder back

[@RotarySMP]

I should have done that while I still had the threaded holes available to locate the inserts precisely.

[@martinchabot_FR]

Got 11 holder for my late asian lathe (multifix clone), but only 6 or 7 for my good old euro one, not enough. The downside of DCMT cutter is the large diameter needed and low cut height (

[@RotarySMP]

I only need a 9mm tall dovetail, and will up the tool diameter some more. Hope I can get that to work.

[@onkelhenning]

A good video. We all learned somthing

[@RotarySMP]

Thanks for your feedback.

[@loug5647]

A pin for the insert with a top clamp to hold it down

[@RotarySMP]

That would probably be required, to make triangle inserts work in this case.

[@kenthesparky178]

I don't class any of this as a fail ,you were doing R&D.😊👍

[@RotarySMP]

The painful thing is relearning other peoples learnt lessons. :)

[@kenthesparky178]

@@RotarySMP I always found that I learnt better from my own trials and tribulations.

[@RotarySMP]

@@kenthesparky178 Unfortunately, it is the same for me.

[@philip_fletcher]

I only have 9 tools holders. Of course the correct number to own is n+1.

[@RotarySMP]

Thanks Philip. That sounds familiar. :)

[@melgross]

I’m in the same boat as you’re are with tool holders. I keep buying them in packs of four. I have about the same number you have. People question me why, when I can change tools in them. But I hate doing that. So every new tool I get gets its own tool holder. Same thing for my mill and ER and DA collets. I’ve got around 100 collets and a bunch of collet chucks plus at least eight drill chucks. Same thing in lathe collets a full set of 64 5C collets. Jacob’s rubber flex collets and chuck, etc. Yeah, you can never have enough tool holders, collets, chucks, etc. I also just buy all my tooling. It really doesn’t pay to make my own. I don’t see the point. I’ve tried a number of Chinese versions and the better ones work just fine, if someone shies away from buying high quality brands. Though, used ones come on the market and are almost always just fine.

[@RotarySMP]

I also bought the AXA style tool holders, as they were cheaper than making my own. Unfortunately those old Schaublin holders are not available.

[@Sigmatechnica]

you can get brakable loctite thats designed to sheer wiith moderate force so you can get the screws out. you can also just make the thing hot and burn it out if needs be...

[@RotarySMP]

If it is liquid, it is not stuck :)

[@theromihs]

I only have 4 tool holder.. As for the dovetail cutter, I think the issues are due to the cutting forces being applied to the screws. The holder needs to be designed such that the insert is held captive in a pocket and the screw simply keeps it in the pocket. Cutting forces should be transferred to the holder via the pocket geometry.

[@RotarySMP]

Yep, that is why the replacement will have DCMT inserts in pockets.

[@rok1475]

Have you ever seen an indexable dovetail cutter using triangular inserts, with pockets? No, did not, because the pocket would have to stick outside the insert and thus interfere with the cut.

[@robertwatsonbath]

Thanks. It's Schaublin - that chamfer is probably there for a reason... we just haven't it out yet. Randy Richards (in the Shop, on YT) made his dovetail cutters with a single 60 degree insert. Only 25% of the hassle and you always know which insert is doing the cutting :) Homework problems: 1: 6 tool holders, 2: more than 6.

[@RotarySMP]

Thanks Robert. I am too impatient to wait for a single tooth cutter to slowly work its way through 12 blocks of steel :)

[@Logan880121]

I have made the same style cutter years ago never had any problem with it. But I never made so agressive cuts with it like you. You even made a wave like finish, indicating of flexing. 60 m/m and 0.03 mm per tooth sounds reasonable.

[@RotarySMP]

I found the insert edges didn't really cut unless I used closer to 0.1mm/rev. I made a bunch of small error on this one which added up. The next one will be better.

[@WalterWojcik]

#1 I have 10 tool holders for my lathe. #2 - All of them!

[@RotarySMP]

Thanks Walter. Do you find you are having to switch tools in the holders a lot?

[@WalterWojcik]

@@RotarySMP Fairly often, you can never have enough tool holders. I cope by planning the tools I need and setting them up before a project so I'm not swapping mid-project.

[@WalterWojcik]

@@RotarySMP Depends on the project. Like most people I keep the most popular ones in the holders and swap out the special ones as needed. You can never have too many tool holders!

[@dazaspc]

Without being to difficult the problem is the screws are taking the cutting load. They should only ever hold the tool down never in. The screws stretch after a while and even in a proper tool holder they should be replaced after every tip change. Thats anything with a 2.3 ~2.7 mm thread. You could save it by using a dowel in place of the screw and a clamp style on the back. Alternatively in the past when new cutters were not available I have converted to a 3mm standard cap screw and a machined bush to fit over the screw and into its screw seat area. The bigger screws hold up remarkably well and whilst they still stretch lasted longer than the 2.5. These were used in high volume production machinery that often had to deal with inconsistent cuts and chunks of metal floating around the tool. If you make a new tool it might be worth considering changing the tip style from a TCMT style to a VNMG style. It would cut the 60 deg when set to the correct angle and because it would use a sweeping cut at the end of the tip to cut a flat bottom. A VNMG would be well supported and would comfortably get by with the standard screw for attachment. You could just copy the nest from a turning tool. Another option could be add some support for the top edge of the tips in the cutter. A few blobs of weld or braze and machine just to give some support in a third axis. You would loose a little cutting depth but it would work. You could even get cheeky and drill and tap for a screw and have its head supporting the third axis of load. Good Luck Cheers

[@RotarySMP]

Thanks. The next version will have DCMT, with a proper pocket to support the insert on two edges.

[@stuartmorris4694]

I think the the tapped holes are not square to the inserts and are putting a slight bend on the 2.5mm screws or offset to the insert centre.

[@RotarySMP]

Could be Stuart, but I think the basic design is wrong, as the triangle inserts have only one should to but up against. A DCMT could be restrained by two shoulders.

[@emilgabor88]

Hi. On one lathe I have like 13 tool holders and it’s ok. On another lathe I have like 20 , and it’s not enough. And on my cnc lathe 8 post turret seems enough. Most tools for one job was 8 tools on a manual lathe, all saved in the DRO . More is definitely better not to always change them around

[@RotarySMP]

Hi Emil, I also want to have all the standard tools loaded, with thier offsets in the tool table, and then a few spares for special tools which get loaded for single jobs.

[@brendanshorter5550]

5 and 3 Morse taper ones. 4 more in the mail, 2 Dickson I need to modify and a chunk of steel I need to turn into more. I think so where in the realms of 40 tool holders would suffice, until I need 50.

[@RotarySMP]

It starts to become a space problem eventually.

[@jasonhull5712]

Well I think I have 12 tool holders for my multifix “E” size tool post on my Clausing Metosa C1330S manual lathe. but I’m absolutely certain that I need 12 more !

[@RotarySMP]

I see a pattern here Jason :)

[@jasonhull5712]

@@RotarySMP yes! An expensive pattern! 😂 And to make it even more interesting I’ve just finished making and installing a rear mounted BXA tool post. So that tool post I only have the standard handful that comes with your average eBay kit. And of course I should probably start with at least 12 or so for that tool post as well right ? 🤷‍♂️ 😂🤣🍻

[@RotarySMP]

@@jasonhull5712 It is nice that Aloris/Dorian style is the easiest to get tool holders for. I never bother making any for the AXA on the Boley, as they are cheap and easily available.

[@gertjevanpoppel7270]

Its not a problem to use loctite on the little screws in if your cutter. If you want to change the inserts just heat up the tool to 150 to 200 celsius and the loctite will disintegrate . This temperature will have no effect on your tool. I have done this many times in my 25 years of machinist work. The best is Offcoarse to make a new cutter and use a correct size tap for the screws. When you made the cutter and you pre drill the holes for the threads you probably used a wrong drill or a dull drill and the hole for cutting the thread ended up to large. And now you have loose threads because of this. Specially for these small threads it can be tricky to end up with a correct size hole after pre drilling. For the smaller threads i drill the holes slightly under the recommended pre drill size and use a watchmaker hand reamer to sneak up on the smallest hole size that allows you to cut the threads. And this way end up with "tight " thread that is less likely to come loose when vibrating under cuts 😀

[@RotarySMP]

I did use the correct 2.1mm drill for M2.5 and it was new, but you are right that tolerances get pretty tight down there. But the real root cause is having the insert engaging on two sides, with only support on one. My version 2 cutter will include all the lessons learned.

[@mrtnsnp]

I think I would start with blue loc-tite. That will stop the vibration issues, but still can be removed with some additional force.

[@RotarySMP]

I think it needs a different insert and better pocket to support it on two sides.

[@mrtnsnp]

@@RotarySMP Yes, if the pocket supports the insert and prevents it from moving about, that reduces the forces on the screws. Broken screws aren't going to be remedied by better glue. Still, the blue stuff is useful to have around. It isn't as strong, but will prevent a loose screw causing trouble.

[@RotarySMP]

@@mrtnsnp I have green and red at this stage. Blue is the medium between them right?

[@mrtnsnp]

@@RotarySMP Not sure. The blue is typically used on bicycles to prevent bolts coming loose because of vibrations. The bond can be broken without heat and a bit more force than a bare bolt. Certainly less strong than green, not sure about red, thought that is more a gap filler to make a connection airtight.

[@Paul-FrancisB]

I only have 6 CXAs so far for my old Harrison. My solution for the inserts will be to use my little Elliott shaper. More toolholders are on the to do list 😀

[@RotarySMP]

A shaper is a very cool tool. Shame I dont really have space for one.

[@Paul-FrancisB]

@@RotarySMP it's very therapeutic, I guess space is a choice between more than one lathe or a shaper.

[@RotarySMP]

@@Paul-FrancisB I need to sell off the Boley and the Minilathe, but next I would love to get a surface grinder. :)

[@Paul-FrancisB]

@@RotarySMP ah so many choices, I would love to find a space for a surface grinder but that would probably mean giving up a motorbike, which is too high a price. 🤔

[@andreblanchard8315]

Yep, the insert screw should be pushing the insert into the pocket. And the cutting forces should be in the same direction, into the pocket. Bought a used LS Okuma, it come with a QC tool post and one holder, purchased 2 more holders. No matter how many, i will likely always need more.

[@RotarySMP]

Okuma makes nice lathes. Thanks for your comment Andre. The next cutter will have a proper pocket to support a DCMT insert.

[@bobvines00]

I was going to recommend "Loctite® Threadlocker Blue 242®" to secure the screws, but leave them removeable with hand tools. However, if you're going to redesign the dovetail cutter, you may not need any type of threadlocker. Are the screws that kept breaking from an insert holder manufacturer? If not, the screws you used may be the wrong alloy/heat-treatment. I'm looking forward to seeing how to solve this "dovetail/dovetail-cutter" problem. Thumbs up!

[@RotarySMP]

Thanks Bob, I am going to address all these points, but have a couple of other projects to do first before I make dovetail cutter V2.0.

[@MikelNaUsaCom]

NEVER enough tool holders... lol... but I also never have enough tools in general. It looks like you have a direction for the future, but I do agree with the consensus here. Still, it was great that you brought back all that treasure from Malta! what will you make with all the tool holders? more toolholders? How's the bandsaw going?

[@RotarySMP]

Hi Mike, the band saw works well enough to not be my most urgent job, but jumps out of gear often enough to drive me nuts :) I will try to have all my standard roughing and finishing tools, threading and cut off tools loaded and dialed in on the tool table, so I dont have to keep touching them off.

[@MikelNaUsaCom]

@@RotarySMP thx for the videos. I could offer all kinds of suggestions, but nothing I've tried... the closest I will get to this is a reverse chamfer and then finishing by hand with a file. =D

[@uncleheavy6819]

Maybe try reducing the feed rate? Try reducing the d.o.c , too. Each tooth would take a smaller bight and therefore reduce the loadings. This may, or may not work, but it's worth a try.

[@RotarySMP]

This cutter is getting retired. The next one will have pockets fr DCMT inserts to give them more support.

[@uncleheavy6819]

@RotarySMP fair enough. It was just a thought. The problem seems to overloading the fixing screws. So, what's the simplest way to address that. Maybe you're hitting the job too hard on each pass with the dovetail cutter. What would be the downside of giving it a try? Nothing to stop you making a different cutter if that doesn't work or if you have to go painfully slowly with the current cutter.

[@RotarySMP]

@@uncleheavy6819 I suspect that slowing down, means more vibration cycles, as it take longer to cut the dovetail. I really think this design is a failure.

[@RickRolling-tc7vb]

Well done Mark, we have all learned today and he world is a better place for it. Sorry your dovetail tool holder prototype doesn't yet meet industry standards, but it took Sandvik a few goes too and they started a bit earlier than you did. For my lathe, an 8mm Lorch that I try to learn watchmaking on, I have one tool holder: Me! I'm the tool holder. For the tiny forces involved in making watch parts we often use a hand held graver on a tool rest. I have got a cross slide for it but no tool post, so it's a really cool paper weight for the moment.

[@RotarySMP]

I am always in awe at Clickspring shaping metal with a gravor on a watch maker lathe, like a a wood lathe.

[@624Dudley]

Now that I understand the design weakness, I’m impressed that the tool got through as many parts as it did 🧐. Not so bad! 👍

[@RotarySMP]

Hi Doric. Yeah, I was also amazed how long, loose 2.5mm screws "retained" the inserts.

[@beartastic-ftw]

Thanks, entertaining _and_ educational as pr usual! Great stuff!

[@RotarySMP]

Glad you enjoyed it!

[@TheUncleRuckus]

Can't win them all, but it's a learning experience. Looking forward to seeing the next iteration. 👍👍

[@RotarySMP]

You and me both!

[@7LegSpiders]

Thanks for sharing a lesson learned!

[@RotarySMP]

Glad it was helpful!

[@TrPrecisionMachining]

very good job RotarySMP

[@RotarySMP]

Thanks.

[@craigbossard399]

I’ll be interested in how you make a two-sided pocket. The corners are pretty tight.

[@RotarySMP]

I am curious about that as well. Will need a pretty small end mill, with a 7° chamfer.

[@chumbuddy100]

threaded fastener clamo force is related to bolt stretch. i'd counter bore the bolt hole and maybe redesign the cutter to add threads thar are bored away. we used to use a min 1.5x bolt diam for min thread length,

[@RotarySMP]

I thought anything beyond the sixth thread carries no load?

[@chumbuddy100]

@@RotarySMP most bolt failures that I've seen are around the first thread above the nut threads. I think that is where the cyclic stresses are greatest.

[@greglaroche1753]

Maybe tighter threads would help. The screws probably broke after they loosened. How hot was your cutter getting? Heat may have compromised the Locktite. Also, I like the threaded hole drilled all the way through. It make it a lot easier to clean out chips and may make it easier to remove a broken screw. Thanks for the video.

[@RotarySMP]

I don't think better fastening would be enough to address the basic design failure of only supporting the insert along one edge, while two edges are engaged.

[@Mrtrationcrafter]

At the moment I only have 2 Multifix toolholders for my lathe. I normally need around 5 to 6 tools. But that would be a bit expensive.

[@RotarySMP]

Those multifix are a wonderful tool, but you need a wire EDM to make your own holders :)

[@TheKnacklersWorkshop]

Hello Mark, Good days, bad days in the workshop... We all enjoy the good days and learn from the bad days... See you on the next one... Take care. Paul,,

[@RotarySMP]

Thanks Paul.-

[@TheDistur]

Well right now I don't have tool holders. Haven't made the upgrade yet on my little lathe. Guess this week was for learning! I'm sure you'll get this dovetail business sorted soon.

[@RotarySMP]

I sure hope so.

[@DieterTheHorst]

I currently own 15 regular and two round shank toolholders for the Multifix on my Weiler, and I could easily make use of twice that amount. Luckily, buidling a tool height gauge, setting up cutting edge height is no longer the painful process it used to be. Still, I try to pick up additional used holders wherever they are available for cheap.

[@RotarySMP]

Thanks Dieter. Those multifix are really nice.

[@lukerickert5203]

It is a cool project for sure but I haven't had much luck with insert dovetail cutters (even with special inserts). I would suggest either solid carbide or brazed carbide cutters. (even the Chinese one seems to work ok) Having more cutting edges also really seems to help everything run smoothly. You might need a shaper or if you can lock the you could use the mill as a shaper. then you could have a CNC shaper (or I guess maybe planer depending on how you set it up)

[@RotarySMP]

Good point Luke. Do you mean like these ones? www.amazon.de/Rankomu-Schwalbenschwanzfr%C3%A4ser-60-Grad-Schwalbenschwanzfr%C3%A4ser-6-schneidiger-Hartmetall-Schlitzfr%C3%A4ser/dp/B0BGLCB6VL/ref=sr_1_5?__mk_de_DE=%C3%85M%C3%85%C5%BD%C3%95%C3%91&crid=1DSLARWXG8CNA&dib=eyJ2IjoiMSJ9.8WzPYC3r7G6O8gFi_ke5i5Fj599SnibgzCk_aT0SXgzFuMsFnPfydojVE9eI4LnSSB5nhy7BZNQz55KUSfAQWEkTIlBZ_cjvMst5XbiTjJwlR-27T-kFFx0tSDMJZ4t3Trtei9EBQpXwAl9kiyMAR0gRoJCBrPpGJpdc0UTL6v30i7H6JNUHK7WQr_EkLC2vB9WL-WWc7s4o2RXC-nXfXvDSpCCzDz4zHGjxtp6QK_wjiWDSisTgD8F3JbloJSF_Km1NDNQf2tQPDu556OK4-33uX5PGtanVhXLJl0GuQo0.Gp76sz4RLngJhN9Tp5YkVxUBteYzYpxrAO61qPzugfY&dib_tag=se&keywords=hartmetall+dovetail+cutter&qid=1713947713&s=industrial&sprefix=hartmetal+dovetail+cutt%2Cindustrial%2C145&sr=1-5 It looks terrible, but I guess i could tune it up on the Clarkson before use. I even have the shaping head for the Maho, and have almost never used it.

[@Agnemons]

"Suck it and see" engineering usually generates the most interesting results and the most lessons. Those lessons and results often lead to less suck and see.

[@RotarySMP]

Yeah, sometimes these things work out. This time, less so :)

[@BenMitro]

I own as many tool holders as I have lathes. Precisely zero.

[@RotarySMP]

Sounds like you need a lathe or two ;)

[@stephenperry5849]

It was worth a try. You live and learn. Better luck next time. Thanks for the video!

[@RotarySMP]

Thanks Stephen. The nxt one will be better.

[@chadstrand7868]

thanks for the video

[@RotarySMP]

Thanks Chad.

[@user-xk2ny1vh5h]

High tensile screws needed

[@RotarySMP]

I think 2.5mm screws are probably already 12.9, but threading into an unhardened DIY shank, stronger screws wont change anything.

[@NexusTrimean]

I would make sure the Screw holes are fully through and threaded all the way, so theoretically you could drive a screw in from behind to dislodge a stuck or broken screw.

[@RotarySMP]

Not sure if an M2.5 pushing up against a loctited broken off screw would impart enough friction to rotate the broken bit. More likely just break off another screw.

[@WillemvanLonden]

I have 19 tool holders (Multifix). Can need some more (dedicated).

[@RotarySMP]

Hi Willem, with 19, do you keep all of them set all the time, or do you tend to keep a couple open for special jobs/tools?

[@WillemvanLonden]

I have a couple unused. Like my wife used to say: do you need another guitar? Well,....yes!

[@julias-shed]

Probably about a dozen or so tool holders. Could always use some more 🤣

[@RotarySMP]

Hi Julia. The 18 on the Boley was a pretty good number. I had all the main ones loaded and never needed to change them.

[@julias-shed]

@@RotarySMP I generally only need to change if I’m single point threading. Really need to finish the rack for them 🤣

[@RotarySMP]

@@julias-shed You are right on that. I always meant to for the Boley. That cardboard box was as close to the rack as they got.

[@davidsamways]

Is there a specific reason you were climb milling the dovetails? I've only ever done manual milling and was trained to always avoid climb milling, but perhaps with CNC the problems are avoided? Anyway, I take your point about triangular inserts, but my thought was that the climb milling could have been creating vibration and chatter which was loosening the inserts.

[@RotarySMP]

Hi David, as the mill has nice tight ballscrews, climb milling is preferred as you get better chip clearance.

[@davidsamways]

@@RotarySMP Not thought of that - thanks.

[@MatthewTinker-au-pont-blanc]

How many tool holders is a how long is a piece of string question

[@RotarySMP]

Yeah, never enough?

[@ozgurgulderen]

I had a similar issue with a homemade cutter where screws were getting loose. I realized that it is due to using 2 surfaces of carbide insert getting irregular contact for cutting. Your dovetail cutter is always under pressure on the bottom end while surfacing. Sides of the carbide gets in contact for a short time when the carbide hits to side profiling while spinning. So bottom pressure and side pressure is not constant on the carbide bit and it wiggles the screw. I really needed to seat the carbide like the one you show on 14:42 of your video. Fyi😊

[@RotarySMP]

Yeah, I came to the same realisation. I have ordered DCMT inserts and will make a new cutter.

[@machinists-shortcuts]

Try using the grease that comes with some toolholder on the screw threads. This will help you apply much more torque to the insert screws in the dovetail cutter. This is the purpose of supplying the small tubes of grease with some new insert tooling.

[@RotarySMP]

Thanks for the tip. I really need to get a small torque wrench to get the torque right in these tiny crews as well.

[@machinists-shortcuts]

@@RotarySMP You may also like this tip to eliminate all the trig calcs for matching dovetails. Search for - no trig matching dovetails??

[@steveggca]

@@RotarySMP have a look at the bike sauce channel . he did a test of a few torqkey bike t-handle fixed torque drivers turns out that even the very inexpensive ones are very repeatable and accurate to the set point. might be one suitable for your needed torque

[@tosu4684]

Hi, i own 11 tool holders (Dixon Style) for my old lathe. 5 of them i build my own with my Klopp shaper. If you had one, the dove tail would have been easy (just a joke)

[@RotarySMP]

Yeah, you are right. A shaper would have made a nice job on them.

[@brendanshorter5550]

That's my plan with my Rapide style. One day.

[@RotarySMP]

@@brendanshorter5550 Please make a video of that job Brendan.

[@brendanshorter5550]

@@RotarySMP sometime in the next 2 years. Bought a house with a 14 week old. Much to do.

[@Rustinox]

It's a bit strange that the screws become loose. Maybe give it a try with finer threat screws.

[@RotarySMP]

Hi Michel, I think the single guiding surface at the back, combined with the insert cutting on two edges, or at least rubbing on one, makes is vibrate back and forth along that rear edge, loosening it.

[@HeimoVN]

I currently have 7 tool holders for my lathe, but it is not nearly enough.. I tend to buy a additional tool holder every time I order tooling for the lathe from a certain supplier I use.

[@RotarySMP]

Seven is certainly too few.

[@willemvantsant5105]

Climb milling maybe less aggressive? I copied RR dovetail cutter but i found the HSS dovetail cutters cut more freely with less vibration. I have some brazed carbide cutters, not tried yet.

[@RotarySMP]

It was climb milling. I should have brazed in those inserts while I could.

[@dimtt2]

I also made a tcmt dovetail insert holder a few years ago and had problems with it. My cutter was a single insert one. At first the screw also got loose but at the same time I realised that the thread I cut was stripping due to weak steel selection. I made another one from 1.6582 HT aka 4340, which is plenty strong and hard at HRC 48ish. Then I notic3d that the surface finish was not good and traced it to the trailing edge of the insert rubbing. I guess I chose a small outside diameter for the cutter which combined with the small 7° rake of the insert caused it to rub. So not having any TPG* inserts which have 11° rake and would clear I just lapped a small secondary clearance angle on the slow turning diamond lap I have for scraping inserts. And it worked. Now I don't know if it would survive cnc use and climp cutting cuts. I only have used it in a manual mill with conventional cuts, taking small depth cuts so my experience and lessons may be very different from other people. My advice would be to use a higher rake angle insert regardless of whether you go with an 60degree, or 55degree. Instead of TCMT go with TPG* or TPM*, instead of DCMT choose a DP**

[@RotarySMP]

I already order DCMT. I am pretty sure I have back clearance on this one (35mm dimater), but will increase the diameter on the next one to about 40mm , so I am not too concerned with back clearance. If necessary, I could tweak that on the T&C grinder. This was some pretty tough steel. 6150 iirr.

[@rallymax2]

It’s a bad idea, I think your screws are just not a high enough grade to take the load. They seem soft. The fact that they shattered mid thread while being locked out so I suggested they’re more cheese than iron.

[@RotarySMP]

I don't think better fastening would be enough to address the basic design failure of only supporting the insert along one edge, while two edges are engaged.

[@GeoffTV2]

Oh no! That looked like such a great cutter. At least you got some use out of it. I'm learning with you on this, as I had no idea whether it was a good or bad plan. To answer your question, I have 12 'proper' tool holders. Plus a 3D printed one that holds a dial indicator. I made an aluminium experimental one to try out my dovetail cutting. Then finally I made a steel one for general purpose. I would like to make one for holding a drill chuck and would also like another two or so for different sized boring bars. - Heather

[@RotarySMP]

Hi Heather. Yeah, it was pretty. I should have put it on the shelf instead of traing to use it :) The next of will be better. How happy are you with the 3D printed indicator holder?

[@GeoffTV2]

@@RotarySMP Yeah it seems to work well. I have to go easy with the clamping force (Aloris style) but it's reasonably tough and chunky. I grabbed a design off Thingiverse but it didn't suit my DTI size. I ended up using Fusion 360 to muck about with the mesh. It was a bit of a pain but I got it nice in the end.

[@millwrightrick1]

One thing that could be an issue is the number of the cutting edges. With 4 cutters sympathetic vibrations could be set up in the cutter, loosening the screws. I suppose you could go with a prime number of cutting faces such as 3 or 5 but that would be harder to machine.

[@RotarySMP]

It could have an effect, but there are bigger problems with this design that I need to address. I'll make a new one and try to address all the good inputs people have given.

[@joell439]

Good to know - 👍😎👍

[@RotarySMP]

Hi Joel. The next one should be better.

[@kv4302]

a single insert DCMT dovetail cutter wouldnt be the worst idea, figuring out the pocket is more involved, but you only need one and the accuracy requirements are way lower. with 2 they gotta be pretty close to symmetrical, and what do you even gain? twice the feedrate, and does that matter that much? a DNMG cant work because to get the clearance on the side itll definitionally have to protrude from the bottom. even VNMG cant do that. i think, if my spatial reasoning isnt failing me!

[@RotarySMP]

I was planning to go for a four insert DCMT. Guess we will see how symmetric it turns out with my indexer and mill.

[@kv4302]

@@RotarySMP another way would be to make a boring bar holder (like a boring head but stationary) that holds a SDUCR boring bar at the correct angle to make the dovetail.

[@kv4302]

@@RotarySMP those SDUC boring bars are 3 degrees from the face, so you need 2 more from a wonky drilled spacer bushing to put the boring bar in a weldon holder and you got your 60 degrees on the side. the smallest boring bars that use the 11m insert are 20mm, so thatll fit easy in a 32mm weldon. does that make sense?

[@johnhawkinson]

What number and kind of Loctite did you use (green…290 wicking?)? Normally you should be able to remove even the strongest Loctite by heating the tip of the screwdriver (propane, &c.), so you shouldn't regard Loctite as preventing you from indexing the inserts. It seemed kind of like maybe you "glued" the inserts in with Loctite, rather than only on the threads? But also that the Loctite worked well (too well?) on the deepest screw threads, but not on the screw threads nearest the head…perhaps the hole was bell-mouthed before tapping? All this suggests changes to the screw could help a lot. Perhaps a stronger material (alloy steel?) and maybe a finer thread. Or greater % thread engagement (i.e. smaller tap drill). I'm not sure it's worth giving up on this and starting afresh, though, I would start with red loctite on the threads and maybe CA glue underneath the triangular insert. Drilling out the screw threads and putting in a helicoil or a steel pin to rethread a tighter pitch does seem like it might not be worth the effort, but I'd still watch a video about it! :)

[@johnhawkinson]

But reading more comments, yeah, the fact that the screw was doing all the holding for the insert was the real problem, all the stuff above is just band-aids over that problem. Still, I'd be curious to see attempts to save this tool!

[@RotarySMP]

The next attempt will use DCMT inserts, so they dont engage on two edges, and will have a pocket to support the insert on two sides.

[@flikflak24]

always clean where the inserts go in so there is absolutly nothing in then ( not even a speck of dust ( same goes for the back on the insert as well ) and always use a torkrench ( most is good at about 2.5 newton meter in my experience though some you need 9 newton meter ) since if its not torked down propperly the screw start to vibrate lose and then the insert starts moveing ang banging around witch can easily snap a tiny screw like that. but to much tork just destroy the screw head seat and the tool used to screw it in i know garant make make some pretty nice tork handels for a okay price also that with where it was 33.30 and you then moved it 0.14 and it hit 33.61 is the tool beding slightly sideways under the cutting pressure and deflect and then after you compensated there is less pressure so the tool dont deflect less as well and make it bigger . that why we always do a spring pass or two before the compensate ( and the roughing and finishing by themself so if we only need to run the finishing part we go straight to that ) but if we need to make more then one part we note the missing amout down and compensating in before we run the secend one so it comes out to spec from the start ( aka. you make the first one first run. note down the missing about. finish the first one. move back what you compensated to finish the first part. then compensate with the number you noted down first and it should be to speck or at least super close ) also personally for roughing out that big pocket i would use a ramp toolpath instead of a dynamic/optirough ( dynamic might have slightly less cutting force on the tool but it wear out the ways and screw of the machine way faster. and most of the time the ramp toolpath is faster also saw that your dovetail cutter only have one register side face so it can move up and down way to much ( unlike on the picture you showed in the video and even your high feed cutter that you used witch both have to sides that it register the insert up agenst) if you dont need the whole length then make so it also regiser up around the top of the insert. maybe even use bigger inserts so its possible ( maybe even do big insert with dual side register with screw and a small clamp down arm so we really can't move at all )

[@RotarySMP]

I need to look into ramp toolopaths, I don't know them. The next cutter will have DCMT, and a pocket with dual register.

[@flikflak24]

@@RotarySMP thats what i like to see. are you also gonna get a torque handle so you dont over or under tighten the screws ? most of the manifacturs for the insert screws also say on there website how much torque you should use on that model of screw

[@RotarySMP]

@@flikflak24 Yeah, good point.

[@theafro]

With a triangular insert loaded like that, it's not the body of the cutter that supports the insert, it's just the screw. Hindsight's always 20/20! So now we know!

[@RotarySMP]

Yeah, a lot of dumb design decision sin this one.

[@LCalleja]

Grate work on the tool holders! That steal is quite tough to machine but should make decent tool holders :) Why not try brazing the inserts in now as it is still not any good at the moment? Hope its not a competition but just counted my tool holders I have 40, 23of them have my most used tools

[@RotarySMP]

Hi Luke. I would need the screws to align the inserts for brazing, but the screws are broken and jammed in the threaded holes.

[@LCalleja]

Might make an interesting video getting them out :)

[@RotarySMP]

@@LCalleja I'll probably make a video on paint drying first :) That cutter can be retired, or kept as a emergency flycutter dovetail cutter for aluminium.

[@LCalleja]

@@RotarySMP well paint stripping got in there might as well put paint drying:)

[@michaellinahan7740]

I have 18 but only regularly use 8 (I got a job lot from Mau's empire of dirt) Could you use a longer screw and have a nylock on the back side?

[@RotarySMP]

No, as the back side is out on the cutter radius. It needs an insert which can be supported in a pocket on two sides. DCMT should be better.

[@michaellinahan7740]

@@RotarySMP ah yes I see.

[@ashreid20]

Time for P2 🥕

[@RotarySMP]

Yeah, the next one will be a better design.

[@gorak9000]

My Grizly G0602 came with about 4 AXA holders. I ordered 20 more import ones from ebay that should be delivered in a couple of days. If I had a functional mill, I'd consider making some, but my mill is still torn apart.

[@gorak9000]

To your credit, there are indexable dovetail cutters, but they all use TDEW or TDEX inserts, not TCMT. I have to look up how those geometries actually differ.

[@RotarySMP]

Thanks for the tip.

[@bheckel1]

have 26. need 260 more. Like the numbering. how do you set 0 for the library?

[@RotarySMP]

I haven't really done that much with that Mini-Lathe, and just set tool one and touch off with it.

[@big_bad_lynx]

I've got exactly 0 of those tools. saying that - I have 6 sash clamps for wood and bought 8 more pipe clamps. It's very unhealthy for your state of mind to have less of whatever. Great job as ever

[@RotarySMP]

Never enough clamps for sure.

[@heronguarezi6501]

Make to mounting systems for the inserts. Leave the screw in the middle and add a clamp to the back of the insert. This will reduce the lever on the screw and make it only guide de insert laterally

[@RotarySMP]

Thanks, but I think I'll switch to DCMT so I can locate it more positively in a pocket.

[@rok1475]

The root cause of the inserts coming loose is that the side of the insert seat was cut at 90deg instead of 97 deg. At 90 there is only a very small contact point between the insert and the side seat. After a while the hard edge of the insert touching the cutter body will wear out the holder and come loose. Commercial cutters always have the side of the seat cut to match the insert angle.