Cutting Left-Hand Acme Threads on the Metal Lathe

Cutting left hand, 2 TPI, Acme threads on a Monarch Model K metal lathe.
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[@johnhenderson1760]

Thank you very much, Keith, for backing out and showing how you're manipulating the controls. It adds tremendous value to your videos. I'm sure that a large fraction of your audience is like me, and does not have the means to perform machining themselves, and watch your videos to live vicariously through you and to learn how it's done. Also, I think it's time you show some love to your cherished horizontal mill and at least give it some fresh paint.

[@paultruesdale7680]

Beautiful job, great threading and machining the keyway on the horizontal was icing on the cake.

[@Mariano.Bernacki]

Next video: Inside tapered metric left-handed blind hole threads in Titanium (while blindfolded and one hand tied)

[@scottpecora371]

You forgot to add single point threading...

[@johnopalko5223]

I wish my dad was still alive. He'd have loved your channel.

[@StreuB1]

16:25 I literally clapped and said "bravo" at this point. Well done Keith, very nicely done.

[@davidmclean5067]

I said, "and...that's how it's done!"

[@douglynch8442]

Your attention to restorative detail is what makes your videos so great to watch! Thanks Keith!

[@kerrywil1]

Thank you for this video. I need to replace a cross slide lead screw on a lathe. This really helped. My wife won a USDA honors award when she worked.

[@razorworks9942]

I see you did this one a couple years ago Keith and like so many others have commented on how well your videos are done and your explanations are very through. Looks like I will be attempting to cut a new lead screw for my Southbend 16" new to me lathe that we talked about last week.. Hope your doing better my friend! Razor..

[@KensSmallEngineRepair]

Always nice to see manual machining. The new crop of young CNC machinists(using the term loosely) should have to go through a manual machining apprenticeship before ever cutting a chip on a CNC! Always good to know the basics.

[@SunnnyDay]

"Spring Pass"--Brilliant concept, thank you, I learned something !!

[@lldrabek4569]

you do a wonderful job of showing and explaining your process really enjoy watching your vids. keepem comin. thanks for the info.

[@roncartwright4092]

You make things look so Easy! Thanks for another great video.

[@WillyBemis]

Thank you Keith!!

[@hitnmiss49]

Thanks for showing us every step in the process of making this piece. We all greatly appreciate you sharing your vast knowledge us Keith.

[@donaldnaymon3270]

Great job Keith. You made that look easy. Thank you for sharing.

[@ElectraFlarefire]

Only 'issue' I have with this is I'd really like to know a bit more about the machines that these parts go in! So many interesting parts! Even a few photos of the install would be good.

[@CAPFlyer]

I'm sure Adam will post pics when he get is back on his instagram - blacksmithtools

[@michaelkenefick]

@@CAPFlyer And / or he could be a member of OWWM.org?

[@danbreyfogle8486]

What I appreciate about your channel is that you seem to know that many of us here are not machinists so when a term is used you explain it. I have heard "spring pass" by several machinists but had no idea what it meant. I knew the term was used near the end of the machining but not what it was. So I learned something new tonight as well as be entertained by someone that knows his machines and how to use them. Thank you Keith.

[@dalejones4186]

Thanks Keith. I always enjoy your videos.

[@tomnugent845]

Keith, you make it look so easy. Great job!

[@wilde.coyote6618]

This is the first viewing of your model k lathe running. I am happy to see it.

[@dazaspc]

Got to love that Free machining steel. Haven't used that since High School.

[@kensherwin4544]

We had a design engineer replace an 8620 cold-headed part with 12L14 on a screw machine. The part should have only been loaded in compression so the change was so much of a no-brainer that it didn't even need testing (or so they thought!). It turned out that dynamic inertial loading put the part in tension and they broke in the field, requiring an expensive field campaign. That experience caused the banning of 12L14 throughout the company, regardless of usage. No, I was not the design engineer that caused the problem. I was the test engineer that had to find out why it failed. 50 years later, leaded steel still causes bad memories. For what Keith was doing, it's a perfect material, making the turner's life a lot easier without compromising the actual use.

[@howardosborne8647]

The leaded steel is a major factor in making this kind of awkward thread cutting possible. If the specifier will permit then always choose a piece of free cutting leaded. It makes the job so much less difficult.

[@dazaspc]

@@kensherwin4544 That isn't a surprise, it was also banned in the shop where I did my apprenticeship.

[@felixgarf]

Keith, Love you videos. I've seen everyone. Your through explanations are great. My only complaint is there aren't enough more often. Also I love you appreciation for history and your work to preserve the documentation.

[@scottfarnham2717]

Well done!

[@blacksmithtools8151]

Keith! This is outstanding!! Thank you!!

[@cojones8518]

2:00 Leaded iron is handy to kill space vampires too.

[@kurtarmbrust]

Saw your post on Instagram! That is a chunky thread. Glad you were able to copy it.

[@P61guy61]

Thank you for posting another fine video.

[@KG-yn9qi]

It was your rebuild of the plainer-matcher restore that Hooked me to your Channel...

[@jerrycoleman2610]

Keith, Nice work detail, it’s always interesting watching these types of threads being cut thanks for sharing.!.!.!.

[@BruceBoschek]

Excellent, detailed video. I always enjoy hearing your thoughts about why you do something the way you do. I often try to outguess you before listening to what you have to say. I'm not always on the money! lol Thanks Keith!

[@superpedro7295]

Thanks for helping us, i am getting ready to start treading on my lathe and you been of great help

[@mikecabe6127]

Another great job......Thanks Keith!!

[@Jim-ie6uf]

Excellent, I don’t even have any machine tools but I love the process.

[@ramsay19481]

Cutting oil.. Your K&T will love you for it....Cheers; Mike in Louisiana

[@GoCreateHobbyMachineShop]

That looks like fun, really impressed !

[@unclebobsbees4899]

Keith I could hear the relief when the thread worked. Those operations, that are done rarely, still gets the sweat forming. 😁 Super nice work.

[@marknewsome9563]

Nice job as usual Keith

[@elsdp-4560]

THANK YOU...for sharing. Very nice. Watched and very much enjoyed.

[@mst1052]

You make it look easy, nice job

[@GeorgeWMays]

Great fun. Thanks for sharing.

[@perceive8159]

Not all machinists are comfortable feeding into a L/H thread without an undercut at the start. It’s far easier to pullout than feed in. If you need to cut a L/H without a undercut just invert the cutter ( adjust to centreline ) run in reverse but feed forward. This is actually a better approach to thin shafts, the cutting force pushes the shaft down instead of lifting it where the chatter will nominally occur . reverse turning on thin wall tubing that has substantial length will definitely benefit from this approach . Quite often cnc machines will use this approach to generate better work piece stability also. Not all machinists are aware of this approach or have forgotten about it’s benefits .💡

[@joegarrett7580]

Great use of the 'stop' feature in the cross-feed.

[@outsidescrewball]

great video...discussion/demonstration/build....lots of lessons..thanks

[@Just1GuyMetalworks]

What a beast of a thread! Beautiful 😁. Pretty sure that would RIP the compound right off my little lathe 🤣. Great work👍😁👍.

[@paulputnam2305]

Great Job!

[@thebear5454]

You make it look easy Keith.

[@Cromwell648]

Good video, I'm very surprised that such a course thread over that distance, didn't chatter. Great job Keith. 🇬🇧

[@howardosborne8647]

Nice one ,Keith. Them steep helix angle coarse threads can be awkward sods to cut if one isn't experienced. Also that is a crafty technique of feeding in some depth after the halfnuts are engaged. I got so busy talking about this video I almost forgot to subscribe. Its done now

[@joshwelch8288]

Came out nice!

[@carloscordero4204]

you always do great work !

[@donmittlestaedt1117]

Thanks Keith

[@toolbox-gua]

I missed the first step to establish OD. Then the nut not going in. But I’m the student and You are our teacher. Thank you.

[@bcbloc02]

65F in Keiths shop, perfect weather for doing some projects!

[@marvincarvin1846]

Most Excellent Video. Thanks!

[@alistairpowers8129]

Keith, Good job, nice to see how it is done, last time I used a tool with a Acme thread was on an Oilfield Drilling Sub (Tubing Hanger) it was a little finer than that one though.

[@turbocobra]

Awesome video, course threads for sure. I have limited experience with single point threading but what i do know is that its pretty time consuming and requires patience. Nice work!

[@apachesmokemachining6487]

Great job mate 👍🏻

[@SciPunk215]

Good job!

[@LincolnSP150]

Nice Job, ..... excellent video too.

[@umahunter]

Nice job man 👍👍👍

[@kerrygleeson4409]

Thanks Keith always very interesting 👍🇦🇺

[@fengelman]

the huge ly coarse thread really makes clear the usefulness of a stop/start" gutter

[@bsteleven]

nice job!!!

[@douglaspierce316]

nice cut

[@jeffanderson1653]

Just whipped up that 2 TPI shaft there Kieth. Made it look so easy. How the heck did you feed in like that to start the cut ever pass? never seen that before. No relief area to start the next pass at depth. I still don't know how you find the time to work in that beautiful shop, volunteer at the museum, edit your many videos and work on that scientist job during the week?? Oh and all the meet and greets you go to. Busy man, I love it!

[@Blackcountrysteam]

Nice job

[@OldtimeIronman]

Ah, now I get it, you're moving the compound in first. Gonna have to remember that trick, thanks!

[@meduffer]

Boom! It fits.

[@piotrlenarczyk5803]

Thank you for video. For fine tuning of any turned surface you can use shot peening via burnishing. It is obvious technique - just make rounded, lapped tool bit with needed shape (it is very similar to cutting tool bit), burnishing feed must be very slight (detail diamater depended), and rpm's must be higher. Such burnishing tool bit is not pulled by malleable steel during last, light passes like cutting tool bit. For rods, soft-soldered, hardened spheres (ball from different ball bearings/balls for hardness testing) are general, burnishing shapes. But this is just a theory, I didn't verify it in real world practice (especially during threading:).

[@Conno9220]

Depth stop on the cross slide is nice. Wish mine had that..

[@railfan439]

Thanks for the video, Keith. See you at the Bar-Z. Jon

[@WaltSorensen]

Someday I've got to do some internal ACME thread for a leadscrew nut to repair an old 1920's era artisan lathe... it has a similar odd ball ACME thread 3/4"-2TPI-LH double start and seems like a stub as it's not full height. (Although, I don't have the ACME thread gauges to do all the checks you have done)

[@rodneycassidy6037]

Thanks

[@mikeysgarage3697]

I guess cutting threads like that one is where the idea for the quick retract or retractable tool holder came from.

[@JIMMYBUSHIDO]

Reminded me when I had to screwcut a 10 start Acme on a shaft. 1.660 lead, 0.1666 pitch Had to Really concentrate , and allow for the 6 tenths if a thou as I cut each thread.. Nightmare, but a really satisfying job when finished.

[@KathrynLiz1]

Nice work.... :-)

[@ChuckRoss77]

I love turning leaded material...12L14 preferably.

[@JT-ci5mi]

When you started, the cuttings were only on one side of the rod, so, when you are done, your threads will be deeper on one side and shallower on the other, which will cause fitting problems.

[@ThePottingShedWorkshop]

The thread makes contact on the flanks. There is clearance between crest and root so the runout will only vary the clearance, not affect the fit.

[@dlewis4647]

Love the channel! Can you share more info about the "stop" you mention? Maybe you already have?

[@ccrider5398]

Thanks for the detail on the horizontal versus vertical mill for cutting the keyway. Did you have to file the threads?

[@harlech2]

"Today we will be cutting a 2 TPI left-hand stub upside-down inside out thread"....... Keith Rucker.... like a bawss

[@leebarnhart9725]

Thank goodness for Leadloy. Any courser thread than that would be called an auger I guess.

[@billcodey1430]

New camera or new lighting? This video looks great.

[@shadowfox929]

Love watching you work Keith, but at 3:38 you confused the heck out of me. You said it was14 1/2 included angle and half of that is 12 1/4????? I am a novice and never cut acme threads so what am I missing?

[@hodgepodgeenginerd1258]

Dave Calabretta confused the hell outa me too.

[@jeffryblackmon4846]

@@hodgepodgeenginerd1258 Same here.

[@chrispfeffer1106]

I also agree that was confusing. Would like to know how those numbers were arrived at.

[@edo8697]

I will be cutting an acme thread for a restoration, really like the acme fishtail gage, but do not understand the comment about 1/2 the included angle being 12 1/4 deg. Thanks for your great video!

[@hfdzl]

Great vid as always, Question, what is the fixture or type of vice used when cutting the keyway ?? Thanks

[@glenndavis4825]

Hi Keith, Another great video. While turning threads do you feed in using the compound slide and what's your favorite cutting oil?

[@BWOUTRAGE25]

It looks like you are using one of your Monarchs to cut the threads. Would you demonstrate how you setup the cross-slide locking screw to bring your feed back to "0" on each pass? I don't remember seeing the V-block vise jaws that you used on the horizontal mill before. Are they shop made? As always, another great video

[@wi11y1960]

Nice canon adjuster

[@MartsGarage]

Excellent work, Keith. A very interesting video. I was particularly interested in how you fed it in at the start of the threads. i would imagine cutting a clearance groove would have weakened it too much. the start on the original piece looked quite abrupt. Do you think the original part may have been milled? Mart.

[@chrisbartolo4308]

Fantastic work Keith. Any info the vise/jaw setup you used on the horizontal? I looked for a prior video that mentioned it, but couldn't find one. Thanks!

[@4speed3pedals]

Hi Keith. Another good video and it makes me feel a lot more comfortable about acme threading. I have a question. You said that you set a stop for the carriage feed (y-axis). Is that an integral feature of your lathe or is it something you devised? Could you give a quick explanation or possibly show an amateur like me how it works? I am wondering if I could come up with something like that for my small lathe. Thanks.

[@ronaldcrowder404]

You amaze watching you machining threads and I have a question. Can you machine threads with a separate and independent power feed on your leadscrew that in no way is connected to your lathe motor? Is there a formula or old timers trick ?

[@darrellblanchard2362]

Did you have the compound set at 7° or 14° . Sounded like a little chatter last couple of inches. Nice video!😁

[@CatNolara]

Very nice, hope it doesn't matter that much that the thread is a little off center, as you can clearly see on the first pass

[@paulcopeland9035]

Nope.

[@djorges]

Is there a reason for not truing up the stock before cutting threads?

[@kensherwin4544]

I'm badly confused. At about 3:30, the included angle on the thread is 14-1/2 degrees so half of that is 12-1/4 degrees on the compound. My arithmetic says it is 7-1/4 degrees. What am I missing?

[@littleworkshopofhorrors2395]

Acme included angle is 29 degrees, so half included is 14.5. .i am confused too.

[@kensherwin4544]

@@littleworkshopofhorrors2395 That makes sense. The HALF angle is 14.5, making the 12.25 on the compound correct.

[@paultopolski1978]

I think Keith meant to say 14.25 degree, not 12.25 degree. That would be 14.5 degree minus .5 degree. If you are cutting a 60 degree included angle thread, you set the compound to 29.5 degree.

[@BillySugger1965]

Paul Topolski Nope, 14.5 minus 0.5 is 14.0. I’m confused too.

[@andyZ3500s]

@@paultopolski1978 I had to watch it twice. I think you are write and it was just a slip of the tongue?

[@Justone177]

You mention a stop on the carriage, is that something integrated into the lathe, or something you added/built?

[@Grandpa82547]

I just noticed your Wilton vise. I'v been wondering why you machinists are so excited to find an old, broken, rusty one. Then I saw them for sale new at a parts store. EXPENSIVE1

[@jamesallen712]

When I did lathe work as school, back in the 1970's, we always had a liquid pouring onto the work where you have a pot and brush. Is that just for filming or a prefered method?

[@DavoShed]

How does 12.25 = 1/2 of 14.5 ? I don’t want to sound picky but I want to learn how to do acme threads correctly and this is a bit I have always wondered about.