Threading on manual lathe with tap in headstock

nordlichtFanuc · Mar 16, 2020

Had a discussion with a friend and Im curious about other opinions:

He is tapping on his manual lathe with the tap in a drillchuck rigidly mounted in the tailstock.

For this, he sets the lathe in very low gear with about 50 RPM, oils the ways of the tailstock very good, and lets the tap pull the (loose) tailstock to the work till final depth.

Is this wise way of doing it? It seems to work just fine.. But looks a bit dangerous and Im concerned about the lathe..
I dont think it was designed to be used like this..

What do you guys think?

Edit:
sorry, I had the wrong translation for 'Reitstock'. Please excuse. Changed all to tailstock.

JonFinn · Mar 16, 2020

If you mean the tap is held in the tail-stock, then yes we do this all the time.

EmGo · Mar 16, 2020

I think you meant tailstock (at least I hope you did) and that's very common and easy. However, I usually would not use such a low speed because it takes a lot longer for the chuck to slow down and you have a lot more torque going that slow, so if you try to stop most likely you'll break the tap instead. I put it in the highest gear I can manage to do that operation.

spinninquin · Mar 16, 2020

I'm sort of confused. You're pulling a headstock to a headstock in your example. Are you meaning he puts the tap/drill chuck in the tailstock?

If that's what you mean, then yes, I've done this many times. Usually on through holes as I get kind of skiddish with blind holes. I wanted to try this in my school courses, explained it to the instructor, and he was totally on board. Whether this is good or bad for the lathe or not, I don't see how it could be. The tailstock is meant to be moved. The lathe doesn't know it's a tap moving the tailstock instead of a human.

tft1987 · Mar 16, 2020

nordlichtFanuc said:
Had a discussion with a friend and Im curious about other opinions:

He is tapping on his manual lathe with the tap in a drillchuck rigidly mounted in the headstock.

For this, he sets the lathe in very low gear with about 50 RPM, oils the ways of the headstock very good, and lets the tap pull the (loose) headstock to the work till final depth.

Is this wise way of doing it? It seems to work just fine.. But looks a bit dangerous and Im concerned about the lathe..
I dont think it was designed to be used like this..

What do you guys think?

You say headstock, but i suspect you meant tailstock. And i have been doing it this way for years (the heavier the tailstock, the larger the minimum tap size you can do this with is...

Conrad Hoffman · Mar 16, 2020

Depending on the size of the tap, I like to put the tap in a drill chuck with a straight rod coming out the back. That goes in a close fitting hole in a block on the tool post. You hold the chuck and advance it to the spinning work. When the tap hits the right depth, the bottom or the torque just has you nervous, you let go of the chuck. It spins, tapping stops and all is well. Reverse the lathe and hold the chuck again to back it out. Almost never bust a tap this way and it's pretty fast. Works with tiny taps as well. Obviously only good if the hole is on center.

michiganbuck · Mar 16, 2020

Power tapping in a drill press chuck is good because the drill press feed is free to pull in/down. I often hand tap on the drill press with a center point on the drill press chick and a little down pressure to get started.
Tap in the lathe tail stock chuck and the head stock pulling the tail is common but tricky because the tail has to be just loose enough to slide and tight enough to not tip off angle..
Another choice for lathe tap use is to make straight shank coming from the tail chuck.. and then slide tube that has a chuck to hold the the tap straight and held from turning.
There should be some on You Tube for you/your friend to see.

Good to know the drill hole depth and then count the rotations so knowing the tapped depth / and not bottom out...many tapped hole might use 7 to 11 full turns to make good the full nut or recommend strengths..with some extra hole depth for chips and safety.

MrWhoopee · Mar 16, 2020

nordlichtFanuc said:
Is this wise way of doing it? It seems to work just fine.. But looks a bit dangerous and Im concerned about the lathe..
I dont think it was designed to be used like this..

What do you guys think?

I've done it thousands of times. It's how you make money.

nordlichtFanuc · Mar 17, 2020

Thanks alot for the good feedback.

As edited in my first post, you're of course right. I confused tailstock with headstock. Got the wrong translation.

Great, Im looking forward to using this technique then!

EmanuelGoldstein said:
I think you meant tailstock (at least I hope you did) and that's very common and easy. However, I usually would not use such a low speed because it takes a lot longer for the chuck to slow down and you have a lot more torque going that slow, so if you try to stop most likely you'll break the tap instead. I put it in the highest gear I can manage to do that operation.

Good point!

Tyrone Shoelaces · Mar 18, 2020

I've done it the same way as all the other guys on here with the tap in a drill chuck. I've also used a dead centre in the tailstock inserted into the centre hole of the tap with a big adjustable spanner on the square of the tap jammed against the cross slide or the tool post. You run the spindle slowly and follow the tap up by winding the tailstock handwheel to keep the tap firmly centred. Of course you need to be really on the ball and have a practiced engineers quick reactions, it's not a method I'd recommend for novice turners.

Regards Tyrone.

michiganbuck · Mar 18, 2020

I have done the same with tap in tail and a piece of tape on one head stock chuck jaw to count the turns.
Have also put a wrap of tape on the tap.
and just watched the tail quill length/numbers... and just following with the saddle hand wheel...and with a tail center on my tap wrench with hand turning and the head stock cross geared locked.
Guess guys have other ways...

Some taps like plug taps push the chips to the hole bottom and some like backing out a half turn or so to break the long chips.

Tyrone Shoelaces · Mar 18, 2020

I should add that if you're concerned about bottoming the tap in a blind hole under power you can always wind the chuck around with the chuck key by hand when you get near to bottoming out.

Regards Tyrone.

Big B · Mar 18, 2020

I've done it that way a thousand plus times.

Bill D · Mar 18, 2020

For male pipe tapers I have single point turned them on the lathe to maybe 30% depth with no taper. Then used a manual die and handle to finish the cut to full depth and taper.
I tapped a lot of 1/4-28 (6mm) holes on my lathe cabinet base by using a 3/8" (10mm) rechargable drill. If there was a problem the tap just spun in the chuck and did not snap. At some larger size a drill chuck will simply not hold a tap strong enough to drive it.
Bill D.

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