Question on using lathes

Buffco · November 2018

How do you use a tap or an external thread tool (don't know what it's called) on a lathe? I'm watching folks on the Youtubes chuck taps in there and feeding it but don't know if they are manually feeding it or auto.

How do you time it so that the threads are correct?

Linefinder · November 2018

CPJ is right, but I'd add the following.......

It depends on the size of your lathe. We have a Haas CNC lathe (fantastic machine, BTW) that's tailpiece is so heavy I don't try to power tap anything smaller than 3/8". Anything smaller tends to break the tap. If your lathe is smaller, it's not quite so much of a problem.

Two things make a HUGE difference when "power" (as opposed to manual) tapping. RPM needs to be low, anything over around 75 is too fast. And the cutting fluid you use can make a big difference. For aluminum I use Relton A-9 Aluminum cutting fluid, although plain ISO alcohol will serve in a pinch. For everything else I use CimTap by CimCool.

But, when you get right down to it, if it's a one-off piece (as opposed to a high volume production run), I prefer manual tapping. Less chance of breaking the tool and ruining the part you've already invested hours in. Believe me......you have to do that only a few times until you start to consider power tapping a last resort.

Mike

Linefinder · November 2018

Another tip for power tapping. Use a drill chuck instead of a collet. Tighten the chuck only to the degree that the tap cuts. When the tap encounters resistance that's near its breaking point, it will slip instead of break. You can then finish tapping to your desired depth manually. I do this a lot.

Mike

Linefinder · November 2018

One more tip......if tapping something really hard or gummy, you can use the next larger (by number, not fraction) drill for your pilot hole. Unless you're building to a particular ISO spec, you'll be fine.

tennmike · November 2018

I guess I'm 'odd man out' as I do not power tap a hole on the lathe. I have a bunch of shop made pilots I use to hold the tap, and that is held by the drill chuck in the tailstock. The pilots hold the shank of the tap and have a spring in them to put pressure on the tap to push it into the workpiece. I also have sleeves that fit over the tap body that use a T-handle to hold to while tapping. I turn the lathe headstock by hand. With one hand on the headstock wrench and one on the tap T-handle, I don't normally have to worry about snapping a tap in the hole as the right hand holding the tap T-wrench gives me all the feedback I need to know how much force is being applied. It might not be fast, but it sure saves me a LOT of grief!

Linefinder · November 2018

tennmike said:

I guess I'm 'odd man out' as I do not power tap a hole on the lathe. I have a bunch of shop made pilots I use to hold the tap, and that is held by the drill chuck in the tailstock. The pilots hold the shank of the tap and have a spring in them to put pressure on the tap to push it into the workpiece. I also have sleeves that fit over the tap body that use a T-handle to hold to while tapping. I turn the lathe headstock by hand. With one hand on the headstock wrench and one on the tap T-handle, I don't normally have to worry about snapping a tap in the hole as the right hand holding the tap T-wrench gives me all the feedback I need to know how much force is being applied. It might not be fast, but it sure saves me a LOT of grief!

Agree 100%. Mike

Linefinder · November 2018

cpj said:

I don’t power tap because I don’t have decent taps. And breaking taps blows.

Power tapping, when it works, is a truly wonderful thing. Nothing is better. When it doesn't.....not much is worse. Manual tapping is way safer.

tennmike · November 2018

Power tapping can really make you lose it. 'When I tap this ONE last hole, then I'm done!'. SNAP! *&%^((#&#^%#$(((

Linefinder · November 2018

tennmike said:

Power tapping can really make you lose it. 'When I tap this ONE last hole, then I'm done!'. SNAP! *&%^((#&#^%#$(((

Yep. That's why 95% of the time I manually tap. I just recently bought a spring loaded tap guide. Boy...that thing is sweet!

tennmike · November 2018

Those spring loaded tap guides ARE sweet! I couldn't justify buying one, so I made my own. They sure make tapping a hole a lot more pleasant experience. That spring pressure pushing the tap into the workpiece makes the job a lot easier getting the tap started in the hole.

FFLshooter · November 2018

I made my own also. It’s much nicer to tap using the dead center and a tap handle so I can tell what the tap is doing. Nothing worse than breaking a tap and then having to use a carbide endmill to remove it.

Buffco · November 2018

Thanks guys. I don't have a lathe, nor plans to get one anytime soon, but I have been doing some metal work and watching a lot of the Youtubes.

What I didn't know was how lathes could be set up to move the carriage at the proper speed to cut the right pitch to thread stock. I thought carriages were either manually turned into the piece or computer controlled. I didn't know about the half nut to engage it.

tennmike · November 2018

Buffco said:

What I didn't know was how lathes could be set up to move the carriage at the proper speed to cut the right pitch to thread stock. I thought carriages were either manually turned into the piece or computer controlled. I didn't know about the half nut to engage it.

Some of the really old lathes didn't have the quick change gear box on the front for advancing the carriage for thread cutting. You had a whole pile of gears and a chart, and changed out the gears on the left hand end of the lathe to cut different thread pitches. The little 10-12" lathes being sold are like that now. Some one gave me one of those because it had a broken drive belt. The drive belt is a pain to change, and so is changing out the gears for thread cutting.

Buffco · November 2018

tennmike said:

Buffco said:

What I didn't know was how lathes could be set up to move the carriage at the proper speed to cut the right pitch to thread stock. I thought carriages were either manually turned into the piece or computer controlled. I didn't know about the half nut to engage it.

Some of the really old lathes didn't have the quick change gear box on the front for advancing the carriage for thread cutting. You had a whole pile of gears and a chart, and changed out the gears on the left hand end of the lathe to cut different thread pitches. The little 10-12" lathes being sold are like that now. Some one gave me one of those because it had a broken drive belt. The drive belt is a pain to change, and so is changing out the gears for thread cutting.

Yeah, the Aussie feller on Youtubes that restores old tractors has a lathe like that. He showed the chart and filmed himself changing the gears out.

tennmike · November 2018

cpj said:

Drive bets are simple to change, providing you get the link style belt.

I see you've never had to change a drive belt, UNDER THE LATHE BED WHERE THE MOTOR IS ALSO LOCATED, on one of those little mini lathes.

zorba · November 2018

tennmike said:

cpj said:

Drive bets are simple to change, providing you get the link style belt.

I see you've never had to change a drive belt, UNDER THE LATHE BED WHERE THE MOTOR IS ALSO LOCATED, on one of those little mini lathes.

Picture's worth 1,000 words...

Just sayin'

tennmike · November 2018

zorba said:

tennmike said:

cpj said:

Drive bets are simple to change, providing you get the link style belt.

I see you've never had to change a drive belt, UNDER THE LATHE BED WHERE THE MOTOR IS ALSO LOCATED, on one of those little mini lathes.

Picture's worth 1,000 words...
Just sayin'

Mini lathe is bolted to a metal table. I don't feel like taking the bolts out and flipping it on its side to take a picture. Motor and drive belt are totally enclosed under the headstock frame. Motor has to be dismounted to change the toothed belt.

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