Compound Lead Screw for American Pacemaker

[@rockwell6594]

The root diameter that Adam was approaching is less than 0.55", which makes for a pretty flexible workpiece.. I think what is happening is that as the tool gets towards the mid length of the workpiece, the workpiece is deflecting upwards, which puts the tool below center, which then allows the workpiece to start to climb into the tool and thereby deepen the cut. The shallow taper on the flanks of the thread probably enhances the effect. In other words, the flanks of the thread on the workpiece can engage with the below centrer tapered tool and so make the workpiece climb further onto the tool. The effect may even be sucking the cross slide (or the topslide) forward into the cut. Some backward hand pressure on the tool post may avoid the latter possibility. A travelling steady would stop the workpiece from deflecting upwards in the first place and hopefully stop the whole cascade from starting. It is really good that Adam shares the things that don't work out as expected. That's where some of the best lessons come from. Cheers.

[@Dutchamp]

That's just under 14 mm whooo that's very thin. Think the original would be made in a different way then turning.

[@chrisarmstrong8198]

Agreed. A travelling steady is definitely worth a try, especially with an Acme thread since the top is flat.

[@jdm2651]

Clear and articulated, should make top comment.

[@kbuss10]

yea but he said he was just feeding 1/2000" ...?

[@Rorschach1024]

Agreed, perhaps a follow rest or steady rest might be in order here.

[@lqueryvg666]

This is the BIGGEST reason why I watch Adam.....he shows EVERYTHING - goods/bads/etc....my heart did sink when I heard that noise though!!!

[@xroles]

I am so appreciative of the fact that you are willing to show issues like this happening, a lot of people would not want to show problems/mistakes, This was a great thing to see that stuff like this happens to the best of us.

[@t.d.mich.7064]

The cutting pressure gets so great on an Acme thread, that it overcomes the ability of the material to maintain a true Centerline. The workpiece rides upward on the tool bit and causes the bit to be below the Centerline of part rotation. When that happens the material strenght begins to overcome the cutting force of the bit and it all comes crashing down. It's not the lathe, it's the ability of the material to resist the necessary cutting pressures. I would use 4140 H.T. and cutting oil to make that screw.

[@ramanshah7627]

Totally, every pass, the force on the work gets a bit bigger because the profile of the cut gets a bit bigger, but the part's ability to stay straight gets a bit smaller because its cross section gets a bit smaller. The part is just insufficiently supported.

[@Grantherum]

We had tons of folks have the same issue when cutting acme threads. Usually, the case was the part was slipping in the chuck. Either, it was twisting, or being pushed in/out. Not saying that's what your specific problem is but it's worth looking at. That being said, I typically will cut flats on round stock I use for acme threading... This way I get a positive hard connection on the stock, and a stop against the jaws where the round becomes flat, so that you can tell if it is trying to move anywhere on you. Never had a problem doing it this way... Acme threads push a crap ton of pressure on the part and tooling, and even the tightest jaws can have issues holding it.

[@your_utube]

I am NO Machinist, but in my little mind, this possibility came up, so I agree with you.

[@TheWrena440]

Adam, that sucks...big time, but you never edit it out. That, my friend, is another awesome part of your channel.

[@Xeddyhime]

I really appreciate when people show the projects that, for one reason or another, failed to turn out as planned. It gives hope to hobbyists like me to see that even the machinists that I look to for advice still scrap a part now and then. On the brighter side, sometimes mistakes can be the greatest teachers. Looking forward to the next video.

[@andyfields3248]

I've had that same issue, your lathe is fine . . . Your part is climbing up your tool. The part is getting less and less ridged and the insert less sharp. Your taking a bug cut even if not deep because of the surface contact of that big insert. As the part climbs its digging into the left side, the tool is aligned but the part isn't. Clock your insert to a fresh face when you're close to depth. Let part cool well and keep it cool. Use coolant or at least oil. I was told use a follow rest but I find they are more trouble than help. Don't give up on that lathe, stick-stay and make it pay . . . Except the challenge.

[@truckguy6666]

I think this makes a lot of sense.

[@jayslife775]

Was going to say the same thing.. I thought this fella knew what he was doing, but after the wheel valve video and this.. I'm not so sure now.

[@cschwad559]

He hasn’t done acme threads got awhile. I find when I go a few years from a certain job, I don’t do it very well

[@cschwad559]

For awhile

[@chrisquinn3751]

Makes a lot of sense Andy. I'd like a look at the insert under a microscope to check for wear. I'd do exactly as you suggest and rotate the insert when you start to see the chips changing in appearance. The point about decreased rigidity is also well made, there must be a point on pretty well any thread where the length of the part, the decreasing diameter of the core and the ability of the tool to cut cleanly ( it's sharpness? ) gang up on you. In some of Adam's close-up shots you can see a small burr developing on the outer edge of the thread. To me this is an indication that the tool is deforming rather than removing some of the material. Also note the chip form changing with successive cuts ( i.e 25:00 compared with 34:30 ) It's a long shot, but is the tool clamped flat to the bottom of the holder along it whole length? Even a few microns gap could allow a resonance to develop. Heat build up could also contribute as, if the part is held very rigidly, the heat could cause buckling.

[@Byzmax]

Correct me if I'm wrong but as I see it. The deeper the tool gets the load increases and the cross section/diameter of the part is significantly reduced. This will cause the stock to flex and the tool to dig in, Add in to that heat build up and you'll have this problem. My punt is a follower rest and coolant should see it do just fine..... I'd prefer to see this done on this machine as problem solving is all part of why I got into this stuff. Greta video as always

[@8591Steve]

Worked for a company that made lead screws and Ballscrews for 23 years, when we were single point cutting such a large acme we would rough it out with a v form tool first, then cut 5he whole form after and using a spring pass every 10 or so full cuts. Also normally would use a travelling steady to stop the work piece flexing.

[@jeremyzee]

This is more interesting to watch than when things go smooth. I love to hear you think through your troubleshooting process... there's so much to learn hearing a professional talk through what they're thinking. Thanks for the informative videos!

[@johnyarnold422]

Travelling steady rest. Your Monarch is one of the best. Please don't fault it. I use to make 2 1/2 inch 316 stainless square thread, going left and right thread Level winder screws for fishing boat drums, sometimes 6-7 feet long. With a traveling steady, never had a problem. You're a damn fine machinist and i've learned a great deal from you and really enjoy your videos.

[@bobwas4066]

Adam Your best video ever!! When a machinist of your high caliber has a problem machining a part, it reassures us amateurs, that things don't always go as planned and we should not get discouraged. Thank You

[@ram50v8]

I tip my hat to you for showing the mistakes as they happened. As many others have said, numerous variables were involved in the failure. Some in the machine and some in the operator. Not a ding by any means on your abilities, or the eccentricities of the machine, it's just some times the process gets overwhelmed by tiny compounded problems. Be thankful the dig in did not lead to a "grab and fling" (been there, not fun)

[@lnbbnj3879]

David Vic and others are right, follower rest. I worked for one of the largest North American valve manufacturers back in the 90's, I cut 1000's of valve stems all Acme. Mostly in SSTL. On an Engine Lathe ALWAYS used a follower rest. Your lead screw has a pitch to diameter ratio that leads to easy flexing given that length. Nothing wrong with your machine, just your setup.

[@ebutuoyebutouy]

Yup +1.

[@waxore1142]

Namely the cross slide angle.

[@markshort9098]

@@waxore1142 the cross slide isn't adjustable, the compound is set correctly for a left hand acme thread

[@davidmiller4594]

But that won't help if the problem is in the lead screw or the gears.

[@waxore1142]

@@markshort9098 it is adjustable. Two bolts, one on each side. Its basic geometry. The further in it goes the more to the right it goes and the more it's pressing on the right side of the thread. Until it pops out and does what it did.

[@spaight711]

Thanks for sharing your work when it goes wrong. Seeing when things don’t work out is probably more valuable than when it goes perfect, from a learning perspective.

[@jamieamelang8927]

So glad you did this video. Most would have scraped it and just shown the one that turned out perfect. Please update us on what you find out went wrong. No doubt we will all learn something new.

[@manmachinemake3708]

I'll toss my comment in as well. Others have said it and i have found the same, the work is climbing the tool, period. You've removed enough material now that 2 things are happening; 1, the work has become more flexible 2, the tool has more contact area as it gets deeper into the work. Add those 2 and you ceate a situation where the drag coefficient increases with every .002 you are moving in. Get/use the follower rest as they are designed to eliminate this exact scenario. I've ruined enough threads with the same process on my 10EE that has less than .0003 lash in the nut/screws. It's not the lathe my man. A good machinist not only makes junk parts from time to time, but is willing to be humble and ask others for advice. Sometimes we just can't see the forest through the trees. Keep making chips and keep learning !

[@trainedtiger]

Just cutting tool surface area, part just climbed the tool once it had so much traction, slower speed and coolant to lubricate and you're fine. Happens all the time with Acme thread cutting, you can cheat a little by moving half and half with the compound and the cross slide when you get over half depth to balance the cutting forces off the right side and shift some to the left side.

[@trainedtiger]

@@ralphgesler5110 Yeah it would do it just the same on any lathe.

[@Donkusdelux]

Had the part climb on a few threads I've cut, cut pallets of rods I've threaded on a manual so I'm not exactly green at it. I think it's definitely what he is having problems with.

[@easternwoods4378]

I'm wondering if the tool point is not on center with the lathe center, IE the shank is one inch and Adam normally uses a three quarter. Any deflection would then dig in.

[@Rorschach1024]

Adam, you probably know this but for the viewers at home, there is a downside to using oversized stock. the outer part of the barstock has fine grained, homogeneous crystal structure but the inner core (typically barstock bigger than 2-1/2" or so) of larger barstock will have a lot of sulfide inclusions and larger grains because it is both the last part of the bar was to cool, as well as receiving less rolling forces to break up the original cast grain structure.

[@morganspencer-churchill2136]

Useful info, cheers

[@624Dudley]

Rorschach, thanks for that comment. I had been wondering if material homogeneity might be a factor here.

[@Zircon10]

Yes, but! He was getting even chip control and smooth cutting when facing the bar, which on a gross basis would suggest fairly uniform grain structure across the diameter. I know what you are describing is real and have seen that before in mild steel cold rolled barstock, but that doesn’t seem to be the case here.

[@Rorschach1024]

@@Zircon10 this was free machining steel which is riddled with inclusions precisely to make chipbreaking easy. Free machining steels should NEVER be used on any highly loaded or critical component because it's propensity to crack anyway. I'm not sure that material was a good choice for this part.

[@Zircon10]

@@Rorschach1024 Well as a metallurgist with 35 years of industry experience I’ll have to disagree with you re strength and fatigue resistance of Stressproof. Niagra LaSalle manufactures it and here is what they have to say about it: “STRESSPROOF was designed to meet, in one bar, the need for greater strength, elimination of heat treatment, better machinability and improved fatigue and wear resistance. It has a tensile strength of 115,000 psi, yield strength of 100,000 psi and an elongation of 8% minimum (7% above 2”). It is used in many applications including: Arbors, keyed shafts, spindles, gears, pinions, piston rods, sleeves, lead screws, racks, motor shafts, splined shafts, link pins, mandrels, boring bars, collets, bushings, drive shafts, armature shafts, rotary pump shafts, gusher pump shafts, kingpins, oil and water pump shafts, wrist pins.” Notice lead screws are specifically called out as an application. Beyond that many of these parts are loaded well beyond what a cross slide lathe screw will see and applications like piston rods and wrist pins will see far more fatigue cycles than would be seen in a lathe feed screw.

[@tjnak]

I'm glad you left the mishap in the video. It speaks volumes for your integrity.

[@emilgabor88]

The problem is the small diameter screw… it is not the lathe . It is pulling it in because the screw just started going up on your tool… it usually happens on the last 2-3 passes… you need following rest . I have also Destroyed a lot of screw like that …

[@Navigator777777]

I think you are spot on! I couldn't believe there was no steady to prevent climbing.

[@theturnervem1552]

RPM reduced use coolant because final depth over load...

[@md662696]

Correct,That is the reason.

[@havokca]

It flexes away from the tool, which causes the thread walls to spread out on the far side of the tool, and to pinch in on the near side…. So it pinches the tool, and, like you said, it tries to climb up it.

[@aaronfritz7234]

I’m just a amateur but I had a similar problem with 3/4x8 tpi acme thread. I used a follow rest and the tool pressure was so high it destroyed the brass tips on my follow rest. Any ideas?

[@johnrobinson6449]

Old broke-down machinist here. How infurating! Having a part go belly-up so close to completion! I used to run a 20-inch swing 8 ft gap-bed Nardini. The lead screw was buggered in that to the point that cutting single-point threads was pointless (pun intended?) :). As far as your situation, the deeper the tool gets into the thread, the greater the tool pressure gets, as there is contact on the point and both sides of the tool. Also, the root dia is decreasing giving the part more ability to flex, thus increasing the possibility for chatter. Once the chatter starts, the chatter vibration will be conducted to both your cross and compound-slides. That chatter may cause the slides to creep into the backlash zones thus moving the tool deeper into the part. If that's the case I think I'd try using the slide-lock screws to try and prevent any creep. I think I'd also try a heavy duty cutting fluid. Perhaps Moly Dee or Tap Magic. I see the Mystic Metal Mover setting on the saddle, but I didn't see you using it.

[@PeteJ1505]

A general purpose tool, cutting at virtually a single point, will exert significantly less force on the work piece than the Acme thread tool, which has a wide cut. Once you had reduced the diameter of the work piece to the extent that it could flex in the centre due to the force applied by the tool, your problem started. If I am correct, you will get the same problem on the new lathe, if you use the same set up and lathe speed settings, feed rate, etc.

[@sandroiavazzo1112]

Hello Adam, the Monarch is ok, it's just too much tool contact for the distance away from the chuck so the material is flexing as you are getiing deeper, the material is becoming thinner so it's more flexible and riding up on the tool, this will happen on any lathe, now that you know you will figure it out......... looking foward to your solution.

[@maggs131]

This is one of those things that's always boggled my mind and something I've questioned on Keith's channel. This is a relatively short screw, how are the lead screws that a 8 feet long or longer made? This little one clearly flexed so I can only assume the larger ones are cut with a series of dies

[@strangefruit8776]

@@maggs131 follow rest.

[@maggs131]

@@strangefruit8776 I was wondering if there was such a thing and why I've never seen one used

[@aaronmcclain1279]

@@maggs131 . Where I worked at we made a 4 acme thread that was 36" long rod . You still have flex . You just to get feed and speed right . The part was made on CNC 35 y mazak. Alot of things come in to play tool pressure . A lot programers will rough the thread out with a grooving tool then chase it to the thread profile with the right threading insert .

[@IceBergGeo]

@@aaronmcclain1279 kind of like the way the tap made the nut?

[@robertclines7519]

I am glad you share all of your efforts, not just the successes

[@1911wood]

I’ve always admired your self control and your ability not to curse. So I did it for you.

[@MrDdaland]

I suspect at least one word was seen, but not heard......

[@johngreenwood5434]

A travelling steady / follower rest will fix the problem, that deep thread is weakening the work piece too much and its flexing. I was surprised you got as far as you did before the problem started! Great videos Adam, many thanks for sharing your hard-earned expertise.

[@biggothkitty]

Adam, some days you teach, and some days you learn. We appreciate you showing us what can happen. Anyone can do the job when it all goes easy, the good people can find a solution when goes wrong, the really great people can teach someone else how to work through a problem when it goes wrong. You are firmly in that last category, and we enjoy the learning.

[@dwhighsmith]

Adam, thank you for showing when things go wrong. Machining can be a delicate dance. I spent 15 years working as a Machinist for a large slurp pump manufacturer. I chased Stub Acme threads in cast Iron, white iron, 4150, 4340, & 316SS. These were LARGE Single, & multi start threads. Here's what I think your problem is. The diameter of that shaft with the length from the chuck caused the part to start chattering. Once you get chatter into a peice that small and long, you can't get it out. My suggestion for the next peice is to turn your compound 180 degrees so that it's parallel with the ways. Use a insert that's half the nose with of the one needed. Chase the thread to depth by feeding in with the cross slide not the compound. Once to depth, restart at the starting point on the cross slide but advance the compound and chase to depth again. Repeat that until you get the width of the thread you need. The chatter comes from the tool pressure on the nose of the tool. The tool nose width coupled with the diameter and length from the chuck caused it to fail. Lastly, use some better material (4140, 4150). It's not the lathe. Good luck.

[@havenisse2009]

I am impressed on your filming, editing and skills in general. And also that you have the manliness to admit and include failures in your videos. Every master of something has propably failed thousands of times, but it's the brave ones that show fails. Look forward to continuation.

[@jdavidkatz]

The old-style Abom79 video. Technical, frank, honest. More of these videos and less of the others, please.

[@keithhansen3963]

Nothing wrong with that Monarch. Just needs a follow rest. The Diameter of that minor and that shaft length is flexing half way. Damn close to the finish line. I was hoping you would make it.

[@tombirkle6288]

My sense is the problems you hare seeing is the result of thermal expansion: 1) Problem occurred on the final passes when heat has accumulated in the part. 2) The location of the bad cut is in the center of the part. Since it is confined between centers, the thermal expansion is causing the workpiece to bow - with maximum deflection in the center. 3) Cutting on the left edge of the tool also suggests thermal expansion. As always a great video Adam.

[@kw2519]

Gotta keep in mind, you’re turning something that’s 30-40x the diameter. With a very blunt tool nose. Not the machine, you need a follow rest. The part is climbing up the tool tip. Maybe even less SFM? Chatter is usually related to speeds and feeds. It’s a harmonic vibration.

[@greenseed666]

never seen someone fail a job in machining! I suppose they too shy to show it :) thanks! It was a valuable viewing for me :)

[@royflores4766]

The material is getting so small on the minor dia for its length. The material is flexing and trying to climb over the tool. Trust me, the machine is fine

[@rocketman475]

I tend to agree with you. My understanding is like this - "While the tool is normally cutting, it is pulling the rod towards itself. / By default the rod always wants to roll up on top of the cutting tool. When the rod becomes thinner it is less able to resist that pulling action and so it moves toward the tool which results in excess material being removed. When the rod was thicker it was better able to resist deforming towards the tool. The work piece has a changing resonant frequency so be sure to listen to it when it starts to appear. It's telling you that vibrational waves are present and they can rapidly get into phase with each other to sing loudly together to vibrate the work piece violently. "~ original answer by RocketMan.

[@joselucca2728]

Like your honesty, no hiding the problem or making excuses. I am not a machinist, but I've been watching your channel for over three years. Keep up the good work.

[@td5disco965]

Hi Adam from the UK. It’s really good to watch the old style machining content on your channel again. I’ve watched your channel for a number of years and was getting worried you were taking it in a less interesting direction. New machines are great but I doubt most of your viewers can relate to it as well as the home shop you have. I’ve read a few of the comments and I agree the tool pressures being generated are too great and the shaft is flexing. As it climbs the tool the pressures increase and so climbs more and more. As it’s a left hand thread the unwanted cut will be on the left of the tool. I know you’ll get it sorted and I wait with interest to see the resulting video. Great work Adam, love the old shop and the machines within.

[@1ginner1]

Hi Adam, I know you know all the things I am about to say, but here goes anyway. 1st, coolant always, 2nd I always cut with a square thread tool and then come in with the ACME tool to do the flanks. 3rd, I always ( on an old lathe) leave the leadscrew engaged and reverse the feed, taking all the issues with a worn halfnut out of the equation. And finally, that 1/2 deg on the compound could be making a difference. Best of luck on the next one. Mal.

[@bdove7939]

You are an honest man and craftsman.

[@Jondamnit]

Thank you for not hiding this issue from your viewers. I know you never have in the past but it is good to see the experts run into problems.

[@dbriggs1689]

This was one of the best videos I've seen in a long time. I know its extremely frustrating when things go sideways but I can't remember the last time you have been challenged like this on video. Thank you for showing it and I'm looking forward to watching the solution.

[@Bluswede]

Thanks, Adam, for showing this! Those mortals of us out here learn WAY more from a professional having an issue than from a professional having an issue, chucking the part in the bin, and glossing it over!

[@jimkramer]

Thanks for showing your failures/troubles as well as all your successes. This is why you are my favorite machinist channel. I have complete confidence you'll figure it out!

[@RookieLock]

Thank you for showing this Adam.. most people wouldent want to show their problems.. I appreciate that.

[@MatthewQuigley]

Great video! it's even more interesting if something doesn't work out as it was planned!

[@davesmith8936]

Oh thank God! Adam IS human! LOL! I have watched a TON of your videos and I think this is the first time Ive seen you have a failed part. That gives me hope that I too can do this! Keep the great content coming!

[@larrymashburn7789]

This was my thought. I don't wish for Adam to struggle, but it was humanizing and might have lifted him up a little higher to see how he handled it. Me personally, part ruined=cussing and breaking more stuff.

[@wilsonlaidlaw]

Many years ago my father's engineering works in the north of Scotland, used to cut very long acme threads for a piece of whisky distillery machinery. Initially we had the same chattering and digging in problem that you have had Adam. We cured it with a travelling steady rest. Our lathe was a lot more worn than your Monarch.

[@richardandrews6754]

Hi Adam, I am sure you have thought of this but if you are still looking to understand why the thread tool started digging in I would suggest the following may give you a clue. 1. It is an old lathe and the lead screw is bound to be worn therefore only engage the half nuts on the same number each pass, will take longer but should at least repeat every time. 2.use a travelling steady to take the spring out of the job in the centre part of the run, at the length you are cutting with this type of thread form the job is bound to deflect away from the tool a little more with each pass as the core diameter reduces and the stock looses stiffness. this builds up until you end up with such a big cut it results in a tool dig in.usually half way along the pass. 3. change out the tool bit. 4. check the centre height is spot on. 5. Try taking only cuts which cut the centre area of the thread for a few passes until you have got the thread depth down in the center area of the pass to match the far ends which I expect are smaller due to the better support. in other words work the barrel shape out of the piece. I hope this may help find the problem. Great video as always. I agree with you your new lathe would be better but only if you have a travelling steady to stop the deflection along the pass. you can test this just set up a dti near the chuck against the work and try to deflect it towards the dti , then try the same test in the middle of the bar you will be surprised how much more it deflects. also remember this gets worse with each pass of the cut due to the reduction in core diameter resulting in a thinner bar with less rigidity. stay safe

[@ctrchg]

Thanks for your comment. I am new to machining and now I am going to research a traveling steady, etc.

[@richardandrews6754]

@@ctrchg Hi glad it was of help the fixed steady only has two fingers contacting the work, top and rear it bolts to the carriage and travel's with it thus supporting the work against the tool pressure from the front.

[@rustyanvil51]

I appreciate that you show the things that don't turn out so well along with the things that do. That's how everybody learns. I've been a machinist for 35+ years now and have had my fair share of jobs that didn't go well, as has every tradesman. Great video as always

[@houndog7882]

Adam, I love watching you work and how you are always interested in helping new machinists. This film was particularly helpful in that you showed that even super machinists have things go wrong. Thank you.

[@TgWags69]

I'd say it was tool pressure causing the work to bow. As it bows it tightens the shoulders of that deep thread onto the tool causing it to dig in and trying to ride up on the tool. Probably need a follow rest to keep it from bowing. Don't think it was entirely the lathe's fault. Backlash would contribute for sure but probably a secondary issue.

[@Bob_Adkins]

I think you nailed it, the piece is long and whippy with deep threads, a recipe for pinching. At first I thought the tailstock may not be good and tight causing the piece to ride up.

[@ajmann1187]

I never saw anyone cut threads without locking down the compound or using cutting oil until I started watching videos on here but that's two things I always felt was important. Seems like once the chatter starts there's no stopping it.

[@johnlloyd2390]

I suspect that, with the loss of material from threading, the piece is bending, turning a catenary. (Bent like a two-person jump rope.) That would make it behave like it's "thicker" in the middle; it would account for "the tool getting sucked in" and "cutting very heavy," etc.

[@jaguar36]

Thanks so much for posting this and not hiding it. It makes the rest of us who have difficulties feel better to see experts run into issues sometimes too.

[@MartinInAmsterdam]

That smile at the end though :) Despite all the adversity. 😊😊

[@The_Gun_Room]

Love seeing this failure, mainly becuase it shows how transparent you are and how dedicated you are to teaching these things instead of just showing them

[@kennethskirvin469]

I really like that you shared this with us. It's too easy with video to only post the successes. Every working man knows that not every job goes according to plan!

[@martyb3783]

I am always amazed that in 2022 machinists in the US still use inches as a measurement system. Very interesting video. Thanks for taking the time to make it.

[@mungtor]

I'm always amazed that somebody can't conceptualize that a measurement system originally based on fractions (1/2, 1/4, 1/8) was the prevalent system for a very long time. The idea of having a "base 10" with an equally arbitrary standard measurement is not really any better. Show me where on the dial exactly 1/3 of a cm is... :)

[@mulletjocks]

@@mungtor Totally pointless point to make. On the handwheel or digital readout a third of an inch is going to be .333333 repeating or just about as close as you can get it....

[@GEFanuc21t]

No big deal. We just convert from inches to MM or MM to inches for fun when we get bored.

[@martyb3783]

@@mungtor Ever heard of Millimeters or Microns? I agree that the old fraction system has been around a long time...too long. Answer me this, which value is greater, 17/64 or 9/32? Then answer the question, Which one is greater, 12 or 13? If you HONESTLY answered the first question quicker than the second one, then you should stick with the arcane measurement system used only by US, Liberia and Myanmar. By the way I am not being critical of the video, on the contrary. I was just making an observation. I once thought as you do. I am a 60 year old American who decided to think critically, and change (in my opinion) for the better. Old ways are not always the best ways.

[@incubatork]

@@mungtor At least they are part way to changing over, when they use a micrometer they mesures in DECIMALS of. The power of 10, tenths, hundredths and thousandths. Originally from UK I was taught imperial at school (long forgotten)but now changing over to decimal I find it much easier, logical and faster to use. Needless to say I hated fractions at school and still do.

[@andycannarella]

I was sitting here being mesmerized by how well the threading operation was going knowing you have done it many times in the past. I then though does anything ever go wrong, then that happened. I feel your pain when something doesn’t go the way you plan it but it’s great to see that we all have those situations and as long as nobody got hurt it’s not the end of the world.

[@1956Taz]

Hi Adam again I'm watching that's what happens sometimes with carbide versus high speed Steel. One thing you can do is put the tool slightly above Center, that'll keep the shaft from climbing up. A thread like that I've always used high speed Steel with arcs on the top of the flanks for chip flow. Also you're probably didn't use coolant or cutting oil for the video but that would help you greatly also

[@jameskilpatrick7790]

That Monarch has been fed more than a few hot suppers, as AVE would say.. This might be the signal to take the old fellow down for some maintenance, give everything a once-over and address things that need it. Lord knows that with a little TLC, that fine old lathe should last another lifetime or two. Great content! It's really good that you take us along with you when things go wrong, and we get to see the frustration that even a pro experiences from time to time. This channel has always been about integrity and hard work above all else, and nothing has changed there. Cheers!

[@johnmccallum9542]

x2

[@ellieprice363]

I’m pretty sure as meticulous as Adam is that Monarch has been well maintained.

[@RickRose]

Lots of comments below on how you could have done it differently. As a novice, I'm just thankful you showed that *#@$@#$ happens, even to the pros!

[@seancollins9745]

I have the same problem with my monarch 20c, the tool post height was designed for positive rake tools, and most tool posts and tool holders wind up below center line with negative rake tools and a bit of flex and then the part rides up on top of the insert

[@Cowboy-pb3mt]

That tool box takes me back those were the days. I'm 81 now. Never seen a 6jaw self centering chuck.

[@dangodbout7818]

I ran Monarch lathes for years and I have run into that problem before. It could be the split but suspect backlash in the lead screw in your lathe. You have a lot of tool pressure with that insert and when you get to that sweet spot the shaft rides up over center and sucks up the backlash and all hell breaks loose. You might try pulling back on your tool holder with your free hand.

[@steveb9270]

Hay mate , , I cut acme threads nearly every day have done for years and I have never turned the top slide around to 14.5 degrees . There's no need to as it will always want to pull in the back lash just go sideways a bit on the final cut and run a bit of black oil on it better luck next time. Cheers

[@itsverygreen532]

I don't think it was the lathe that moved, I think the bar flexed.

[@TheCuriousOrbs]

Like the fact that Adam proceeded with uploading this as a "what can go wrong" type video. It is no less entertaining to watch from the viewers perspective, despite the heartbreak it obviously caused him at the time of filming. Look forward to seeing the PM lathe put through the same task.

[@thomaschandler8036]

Good to see professionals showing things that go wrong, whatever or whoever the problem. Enjoy your videos and like it better with your new video photographer...Keep up the good work .

[@peterhladky5481]

You and your wife are just the loveliest of people. Great channel!

[@dennissmith8199]

While I'm not a professional machinist, I thought you would provide some sort of support to the middle of the screw. After all, the piece is only going to have a 1/2" diameter cross section when you get the threads cut, and a piece that diameter and over 10 inches long is going to be about as rigid as a wet noodle. I don't think there is a problem with the lathe, the problem is that the work piece needs to be supported in the middle. Frankly, I was surprised you got as far along as you did before the lack of support bit you on the behind.

[@chuckthebull]

Think its great that you show these problems instead of just everything going good..these are the things we get to learn from..

[@SimonPilepich]

Good video! So glad to see you return to your classic content style. Strait to the point and full of good tips

[@LazTLaz]

I'm thinking it's a resonance issue - mainly because I don't want there to be anything seriously wrong with that beautiful Monarch! Kudos for showing us the issue Adam, looking forward to seeing you solve it.

[@alansliski2497]

I know exactly what happened because I've done it before. I have a Monarch 10EE, same issue. The explanation is that the thread stop engages the dial. The handle is attached to the leadscrew. The dial is locked to the leadscrew with a separate knob on the dial near the handle. If this isn't tight, the leadscrew can be advanced after the dial stops if you slam into the stop, or turn the handle hard. The key is to keep the dial-to-screw knob tight when threading.

[@1956Taz]

Hi Adam! I really praise you for showing mistakes mess up shows that this does happen. Not every video wonderful wonderful, so kudos to you! I ran six different monarch lathes and being a lathe Foreman at Atlantic Tool & Die in South Plainfield, New Jersey. I know what you're going through, but I always use high speed Steel. It probably is pulling up over the Centerline what I have done is lifted tool slightly above Centerline but I always use high speed Steel. This is an inherent problem with carbide. If you change the carbide insert you get a fresh Cutting Edge and you might correct a problem like this in the future also follower rest but shouldn't have to do that.

[@andrewvida3829]

I certainly concur that the moment the edge dulls on carbide even just a little, it loses all its appeal in short order. OTOH, that small amount of work on an ostensibly free-machining material should not have resulted in any measurable wear. As for a follow rest, I think you might very well have to. As depth of cut increases, decreasing the minor D, rigidity falls off significantly and, I've found, often rather suddenly in the span of a cut or three. Add to that the increased cutting pressure due to the increased area of the cut as the tool goes deeper into the work and you end up with a whippy workpiece being pressed ever harder by the tool as each new cut removes more material than the previous, depth for depth. 3/4" bar, annealed, isn't going to offer up that much resistance to tool pressure at ~10" between centers, most especially with a form tool.

[@theessexhunter1305]

It is the back lash in the compound, also having the compound set at 14 deg it wants to travel in the fwd direction. I was taught @ a UK toolmakers starting in 1977 and what Harry showed me was to set the compound at 90 and move it a few thou back and fwd on the compound. And do the depth on the cross slide. Your way (the usa way) has twice the dials and back lash to keep control of. 😁

[@ellieprice363]

Either way will work if the stock is heavy enough not to flex. If the cross slide is used for threading depth you cannot use a follower rest which is needed for support on this job.

[@theessexhunter1305]

@@ellieprice363 Yes it is a small diameter to flex, but how I was shown you where only taking the metal of one face at a time so it was slower also this nonsense of no coolant is just to get a good picture. As I pointed out to Adam a long while ago make parts or make TV as spinning plates on sticks is not easy. while you are looking at the camera angle your mind is not on the job I worked in a top end UK toolroom and the only thing above the machines was one or two lads singing short bits of songs not filming.

[@maxpro9346]

Thanks Adam to share your issues as well as your success stories. It is very important for newbies as me, to understand processes and avoiding mistakes. Hope you can bring explanation and solution to that. Enjoyed by your smile at end of the video !

[@russkepler]

I think a 3/4-5 ACME would flex up, particularly after a lot of the thread was cut. A follower rest would help with that. I'd also get some cutting lube in there, I prefer sulphurated oil but most anything would help.

[@yz250a]

It's not the machine, Adam. As the minor diameter gets smaller, the workpiece is deflecting, then being gouged toward the bit at the resonant frequency of that section. A follower rest and cutting oil wil help.

[@realfixesrealproblemssewel82]

A following steady rest is what you need. As another gentleman mentioned in the comments

[@geniuspharmacist]

I'm not a machinist and never will be one but I still spend hours watching machining videos. There's just something magical in machining..... If forging got us out of the stone age, machining took us the rest of the way to where we are now.

[@danav3387]

The rod is bending and binding on the threads. its squeezing the cutting tool between the threads.

[@GameBacardi]

long rod is getting thin from threads, it bends easier.

[@Caughtitoutdoors]

That makes a lot of sense. Since the minor dia. is getting thinner with every pass. And the problem seemed to get worst with every pass.

[@noellwilson1273]

Thanks for showing the Bad and Ugly parts too! That makes us mere mortals feel better about our own experiences. I see “take 2” waiting. It’ll be interesting to see what happened.

[@ls2005019227]

I wouldn't blame the machine just yet.... As the cut continued & more material was removed, the rigidity of the shaft was reduced..... while cutting forces were increasing rapidly (as you approached full depth)- -confirm *on center* tool height -follow rest -oil I had a similar experience cutting splines in a 17-4 SS shaft on a shaper; the tool would want to dig in (because of the large amount of engagement). In that case, the solution was nibbling the bottom, left/right sides independently (which reduced tool pressure). Unless you've now chattered the lead screw undersize, calling this a failure is premature. It's just another challenge that's popped up; adapt & overcome. That's what machining is all about.

[@alancharie9608]

Hi Adam, my expierence cutting Acme or square threads is that square was easier , when cutting Acme with full form tool the deeper you get the greater the load on the tool and part , When I had to cut large acme thread best way I found was keep top slide at 90 not at thread angle , make square tool to relieve the centre of thread then use top slide to go side to side cutting each side in turn , use crossslide for depth of tread , plus cutting oil/coolant

[@davidprovan2250]

Heat from the cut, thin workpiece, pressure increasing from the tailstock causes it to bend away from and try to climb over the tool. Use coolant and a travelling steady. Nothing wrong with the lathe as everything up to that point was fine. Best regards.

[@MickHealey]

Hi Adam, I'm not a machinist, but I am a pedant. Before the cutting all went bad, I noticed something that I thought was odd. If you freeze frame at 31:13, the bottom of the thread seems to have a small step on the left shoulder. Initially, I thought the tool had chipped, but you would notice that. So, I agree with your diagnosis, that the Monarch is not cutting the same path every single time. In the example at 31:13, I would say the tool is under a lot of stress on the right side, and none on the left side. I guess at some critical point, you are going to get oscillation at the resonant frequency, and boom, it all goes bad. Just a thought. I'm an electronics engineer and software tester in my day job :-)

[@Azmodon]

Aside from any other possibilities from wear etc., half a degree of additional cutting is being put on the left side of the cutting tool due to the 14 degree cross. Uneven loading on the opposing cutting faces will cause tool chatter if the torque applied exceeds the rigidity of the holding assembly, hence it happening at depth. Same issue any V cutter has without enough rigidity, or with one slightly more worn face, the pressure on one side is greater causing deflection (if the forces exceed the tool holder + the work pieces deflection at distance from the head), which makes the other side bite more, which pushes back - setting itself up as an oscillating gouge machine due to the harmonics. A quick fix without changing setup is to increase rpm slightly (sometimes lowering, but usually an increase works better given the relative SFM is reducing as you cut deeper), can be enough to keep the cuts out of the resonant frequency range.

[@AnyMajorDude-et2ub]

Really enjoyed the video. I was told in my younger days that the difference between a novice and a master is how many times they have stuffed up a job, and learned from their failures. I know it's disappointing when these things happen so close to a finished run, but the are valuable lessons that turn you into a master at your craft.

[@Universal_Craftsman]

Try setting the tool height higher next time, the shaft climps on the tool and lifts itself up, then the tool has too much relief and starts to chatter and the backlash gets pulled in. A live rest is also recommended and helps with heavy threading.

[@mark..]

Thank you for always showing when you run into problems like this. One of the best things about this channel!

[@camillosteuss]

In my view, as someone who owns a lathe or two, is that you simply need a follow rest... The tool pressure is too high for that diameter at that length between the chuck and the center... As you said, its the rigidity, but its not the lathe`s fault, its more of a lack of proper approach... In my view, acme threads should always have a follow rest, as should any longer threads done on a lathe... It simply avoids you a lot of trouble with deflection and climbing parts and what not... Hell, a follow rest is a great side kick for parting off some rudely unpleasant materials... Sure, it may be a bit tough on the bronze jaws, but just freshen them up with a mill every now and again, they are expendable bearing surface... All the best! P.s. you said that you checked it before the screw up pass with a nut, and i think i saw a wiggle in the tailstock ram when the shot was happening, its entirely possible that you didnt fit the center snug enough and that allowed for chatter which turned into an instant disaster at that diameter without a follow rest...

[@deedeeindustrialsuperprecision]

This is what I have do on difficult materials. There is too much force, so take a narrow profile tool and get to the root of the thread first then try the full profile tool, if that is not working go back to a narrow profile tool with the compound parraell with the ways and shave the flanks of the thread after you reach depth. I notice the lathe has leadscrew reverse, it would be to advantage using that to avoid error from camming in the half nuts and if there is a problem of the piece work hardening always take a cut, no spring passes or that will add chatter. Often working out acme treads in stages like getting a groove to depth and then shaving the flanks to gain the needed width, alloys can be cut in light weight machines. Good luck!

[@o0ThunderGod0o]

Maybe a follow rest would help on such a small shaft?

[@kensmedberg1130]

Thanks for showing this . It's much more educational to show a job going awry than to edit out what has happened . We have all had those mystery gremlins take over our hard work .... and right at the most critical part of the job. Yes, I could make my many guesses, but all but one, or maybe two would be wrong . Good luck on the re-work, and let us know when you find the most guilty of the suspect gremlins .

[@simonsallen]

I think the rod has become thin enough to flex and it is riding up on the cutter. Could you add a back and top rest to take out the whip?

[@2oqp577]

Here is my two cents of opinion; every machining operation creates vibrations even when it seems smooth. They are tiny and until we don't hear them, we don't realize the unset of chatter. So the diameter of the stock was massive enough to absorb those vibrations to the point of stopping the build up of any harmonic vibrations in the work piece, until it wasn't anymore. A mix of the diminishing size of the diameter and its increased flexibility in the middle, permits those vibrations and their harmonics to augment and vary the depth of cut at high speed, creating this pattern on the left side of the thread. It is entirely possible, as Adam proposed, that any slack/backlash in the cross slide or leadscrew, acerbated the situation. Also, one might consider that in an operation like this one, heat will tend to stay in the middle of the work piece, as each ends have a good dissipation mass(head-stock and tail-stock). The suggestion of a follow-rest by Abdul Abbas is a good one. I would add the use of a high viscosity cutting oil, that will not be shaken off easily.