Lathe threading didn't work with traditional way

I was needing to make a threaded hex bolt for work, and did the setup I remember from my schooling. Check and double check the combination of gears, done. Set the crossfeed to 29.5 degrees, done. Align the cutter with a center identifier and use 60* angle carbide tool, done. Use the correct number on the gear wheel as it spins, done and used the same one each time. I tried it about 5 different times and got the same result each time. Poorly made threads that look like it was drifting to the left.

I got tired of trying the same thing each time and decided to try threading without the crossfeed and just used the infeed to .081 for a 16 thread. It looks a million times better and I can't for the life of me seem to think what I screwed up. I'm sort of worried I still did it wrong, even though it seems good enough.

Did I forget something super basic?

Put the compound so it goes straight in. The shift it to the right 30 degrees using a simple protractor. Don't look at the numbers on the compound dial.

Then, look at the graduations on the compound. It will probably read 60, then. You probably had the compound set wrong.

jim rozen said:

Put the compound so it goes straight in. The shift it to the right 30 degrees using a simple protractor. Don't look at the numbers on the compound dial.

Then, look at the graduations on the compound. It will probably read 60, then. You probably had the compound set wrong.

Click to expand...

By "to the right" do you mean shift it clockwise 30 degrees? I feel like a fool. I'd been shifting it to 30 degrees in counter clockwise. Thank you very much.

Turn entire compound rest counter clockwise 30 degrees (handle/graduated dial swung to the right), some of the imports have the degree markings placed oddly and it throws off many inexperienced operators that follow the book instructions. Take a pic of your setup and post here for critique.

Most jobs I rotate the compound counter clockwise, I think that was what Jim meant. I want the tool removing most of the material on the forward edge. I use slightly less than 30 degrees as I want to clean up a little bit of the trailing thread flank. If you shoot for 30 you may get a stair step finish on the trailing flank. Hardinge and maybe others use a different starting point on the graduations so it maybe 30 or 60 depending on who built the lathe. Whatever it is I will use 1 or 2 degrees less.

A torn or drifting thread can also be caused by the part slipping in the chuck. There is a significant thrust load tending to push the part when doing coarse threads.

You may also need to verify that the lead screw thrust bearing has been adjusted to eliminate any free motion.

Or leave the topslide parallel to the lathe axis and for every infeed on the cross slide advance the topslide 1/2 that amount, ......leaving the last 2 or 3 thou infeed just on the cross slide for the tool profile to clean up.

As others have said, you probably have a compound marked in compound angles. My Sheldon is that way and it also has the cross-slide dial marked in diameter reduction, not direct infeed.

I remember using Atlas lathes, where as to you have fiddle with the machine, and do things like keep tension on the handwheel when the tool enters the work, because there is so much flex in the machine the first couple of threads get distorted.
Sometimes, lighter weight machines work better at a higher speed, and or using HSS instead of carbide, to get a more deadly sharp edge.
If the machine is an Axelson, or other heavy weight, the above will not apply.

You don’t mention lathe type but some like Harrisons have alternative gears that fit on the shaft of the screwcutting dial, using the wrong one will effect repeatability.
You could also try leaving the half nuts engaged with the leadscrew and reversing the carriage back after each cut, in this way you will be certain that you are keeping the relationship between the church and saddle constant, if that doesn’t help you;must look elsewhere

Seaturtle said:

I was needing to make a threaded hex bolt for work, and did the setup I remember from my schooling. Check and double check the combination of gears, done. Set the crossfeed to 29.5 degrees, done. Align the cutter with a center identifier and use 60* angle carbide tool, done. Use the correct number on the gear wheel as it spins, done and used the same one each time. I tried it about 5 different times and got the same result each time. Poorly made threads that look like it was drifting to the left.

I got tired of trying the same thing each time and decided to try threading without the crossfeed and just used the infeed to .081 for a 16 thread. It looks a million times better and I can't for the life of me seem to think what I screwed up. I'm sort of worried I still did it wrong, even though it seems good enough.

Did I forget something super basic?

Click to expand...

It has been 21 years since I have run a lathe so please bare with me. If I remember correctly, you do not use the crossfeed to feed for cutting, just in feed using the compound set at 29&1/2 degrees. Monarch 10ee have a stop screw on the crossfeed dial, very helpful. I never had success using carbide, used high speed steel, old school I guess.

Seaturtle said:

I got tired of trying the same thing each time and decided to try threading without the crossfeed and just used the infeed to .081 for a 16 thread. It looks a million times better and I can't for the life of me seem to think what I screwed up.

Did I forget something super basic?

Click to expand...

Only at first.

That you were no longer at school just playin' wit' yerself!



Once you started cutting it as if you were in an industrial environment where there may BE NO compound rest?

You were out of the woods and got good threads.

Once I left school, all my threads were cut that way.

The compound was no use sitting in the back side of the chip tray 8 feet down the bed.

Foreman wudda thot I was NUTS to ask for another hand, plus myself and either foreman himself on the traveler's pendant or a third man having to stop work to run the overhead crane. We only took the massive 4-way off the topslide to mount the compound about once every week or ten days to cut short tapers.

"Straight in" is fine for threading. As you just proved.

Again.

See also CNC. Your inserted Carbide cutter was MADE for straight-in.

With HSS-Cobalt, I have to grind for it.


Here's a good ALL AROUND video in one go:

Threading on a manual lathe BEST TECHNIQUE EVER !!!! - YouTube

Joe covers the basics:

Always thread AWAY from a "feature" such as a shoulder, flat, or undercut.
Spindle is in reverse.
Tool is "upside down". (unless you have a back toolpost). LH thread is opposite.

No drama. No need of special leadscrew reverse or fancy dog-clutched threading aids or other "special features" on the lathe.

NO NEED to even care what angle the compound is set to. It is not used.
Cross slide only.
Straight in for each pass.
Any thread form, any included angle in degree the insert was made for.

I say again. No need to MESS with the compound.
You do not even need to HAVE one mounted.

And then.. Joe even goes through use of thread wires.

Bottom line?

-You don't NEED a compound rest.

- You don't NEED Monarch's "ELSR", Hendey's (and many top-end Euro lathe's) one -tooth dog clutch.

- You don't NEED Cazenueve's "special apron" threading system.

- You don't even NEED a modern lathe.

You can do what Joe just demonstrated on any lathe that will not shed-chuck (or collet) when run in reverse.

War One era Niles cone heads with 4-Ways that needed a traveling crane to swap, most of all.

Nothing "special". Works for internal threads to a blind hole's bottom even BETTER. Start down-hole, thread OUTWARD, not INWARD.

Every card-carrying oscillating Richard on the clock did it this way "back in the day" of clumsy old lathes.

"Hobbyists", amateurs, however talented, (or not-so-much?) and their "compound rests" were under some OTHER roof!

The "shoulder" we ran up against if we were distracted cutting a fresh chaw of Union Leader, Red Man, dipping Copenhagen snuff, or lighting-up an Old Gold straight or a Camel?

Ignorant free air.. TS end of the workpiece! No harm done.



That simple.

From the "straight in" position (your compound could read "0" or "90") move it 29 1/2 deg ccw. It should read 29 1/2 deg if you started
at "0" and 60 1/2 deg. if you started at "90". Now set your tool bit at 90 deg. to your work using a 60 deg. fishtail gage.
Feed in on your top slide only. Not on your cross feed. That stays set at "0" after touching your work. You pull out at the end using the cross feed, return to your starting position and reset your cross feed to "0". Feed in on your top slide.
Yes - picture would help.

juergenwt said:

From the "straight in" position (your compound could read "0" or "90") move it 29 1/2 deg ccw. It should read 29 1/2 deg if you started
at "0" and 60 1/2 deg. if you started at "90". Now set your tool bit at 90 deg. to your work using a 60 deg. fishtail gage.
Feed in on your top slide only. Not on your cross feed. That stays set at "0" after touching your work. You pull out at the end using the cross feed, return to your starting position and reset your cross feed to "0". Feed in on your top slide.
Yes - picture would help.

Click to expand...

Not doing it the hard, slow, carrot-peeler way as if all you had for rigidity was one of what's-his-face's beloved "Alas" lathe shaped objects or a spaghetti-bed South Bent would help even better.

See Joe's video.

Threading on a manual lathe BEST TECHNIQUE EVER !!!! - YouTube

Ignorant "white bread" lathe. Nothing "special". No BS there.

More than one part to thread? You can use hard stops on the longitudinal for START point, and a hard stop on the cross for final DEPTH.

Fast and easy, not slow and complicated.

It IS what "JFW" - his tiny sample.. or four threads to the inch in high-alloy steel.

termite, you fake fuck! Lying about cutting threads is what got you caught lying on the forum in the first place.
Wow termite, lying about being a cop, and stalking me and my family, is why I am on you!
Someone has to be responsible for you here, it looks to me it is the supposed real cop on the sub forum. Since that hero protects you, and attacked me personally, I think that fuck from Texas should control a fake cop like you "yes"
Ha Ha flooding the forum to reach your 20000 post goal, I dont know if you are going to make it without blowing a gasket!
Fake cop, fake machinist, and troll, that is a heavy load!

https://wewilliams.net/docs/1936 - How to Cut Screw Threads in the Lathe - Bulletin 36A.pdf

Page 8 is important.

Good to buy the book, but one can right-click on and save it to their computer.
Good to cut threads by the book until it is easy before trying all other methods.
I grind a positive side and back rake to my bits for mild and tough steel.
I don't see 3 wire check in this book so look that up.

A 3 wire instruction:
Measuring Pitch Diameters using Three Wire Method | Engineers Edge | www.engineersedge.com

For non-spec threads, I just use a high-grade store-bought nut that I have measured for good size, as a gauge..yes watching to see that it does lose size.

The upsidedown bit is Ok on a larger tight lathe but can lift the tool holder on a sloppy lathe. I think it is good to master normal before trying other methods.

michiganbuck said:

The upsidedown bit is Ok on a larger tight lathe but can lift the tool holder on a sloppy lathe.

Click to expand...

Take note that Joe intentionally left his Aloris & toolholder so it COULD lift if over-stressed.

That's a feature. Not a bug.

As mentioned before, set the compound so the dial is pointing straight out at you. Then grasp the handle and move it to the *right* through a 30 degree angle.

Viewed from ABOVE this causes the compound to move in a counter-clockwise direction.

There are excellent reasons to do threading in this manner, as opposed to the straight-in approach. They're documented elsewhere on this forum by
folks a lot smarter than me. Which as termite will tell you, is everyone.

jim rozen said:

As mentioned before, set the compound so the dial is pointing straight out at you. Then grasp the handle and move it to the *right* through a 30 degree angle.

Viewed from ABOVE this causes the compound to move in a counter-clockwise direction.

There are excellent reasons to do threading in this manner, as opposed to the straight-in approach. They're documented elsewhere on this forum by
folks a lot smarter than me. Which as termite will tell you, is everyone.

Click to expand...

The HELL I will!

More fun they discover it on their own hook!

termite, what happened to the BS story about you cutting threads on a 50hp Niles lathe with a 50" swing making spring cuts, in 1959!
That was the statement that made you the king troll of the forum!
Funny, you would post on threading again! And where is your bully projection The drunk hick in the barn? That act is more you... With the Yuhs,Yahs and Yurs, come on fuck head perform!