Power tapping in the lathe

[Davidhcnc]

When power tapping in the lathe I would put the tap in the drill chuck, add a squirt of oil and with slowest speed get started and let it draw itself in, then reverse out.


Trouble is the chuck soon runs out of grip. Hard steel against hard steel.

Then I have to resort to the handle to complete.

So what do you use to hold your taps when power tapping....up to M12 or 1/2" or even bigger?

Thanks

[airsmith282]

i dont do power tapping on the lathe, i have a little jig i built from one i had seen and it works perfect to get things started so its all lined up on the lathe then once ihave a few threads in i take it out fininsh by hand, , that or i just do it manuley from the start never fails me ,,

[PaulT]

Trouble is the chuck soon runs out of grip. Hard steel against hard steel.

As you've discovered, drill chucks and taps are not that good of a match.

I use ER collet holders for taps in both my lathe and mill. You can get ER chucks with MT shanks on them.

Paul T.
www.power-t.com

[macona]

I have had good luck using albrecht chucks. I power tapped 5/8-11 the other night. Though when you reverse the chuck will come loose. At that point I just use a crescent wrench to pull it out.

[squirrel]

All we use are Bilz tap collets and a holder with a 1" shank. You will ruin your drill chucks from the tap slipping. The Bilz tap collets have a square hole that prevents slipping, that slippage can break the tap.

[becksmachine]

When holding a tap in a Jacobs chuck, I always used the "spin factor" as a poor man torque limiter. Now, this is using a ball bearing style Jacobs chuck, tightened about as hard as I can twist the key.

It seemed to work out about right that when the tap starts spinning in the chuck, I am doing something wrong; pushing too hard, not pushing hard enough, flutes packed full, dull tap, hole too small etc.

If I really need to twist the tap harder for 1 or 2 holes, I will start the tap with the chuck to establish alignment and then finish with a tap wrench.

Dave

[BadDog]

I bought some Jacobs collet chucks off ebay (and the first from a local friend). They are intended for tapping machines. They have an appropriate sized Rubber Flex collet to hold the tap coaxial, and a clamp arrangement to hold/drive the square drive of the tap. These work great when held in my 18N (3/4" Super Chuck) and can easily handle large taps. I think the largest I've run is 5/8, which is at the upper range of the largest chuck I have. Larger than that and I generally single point it, too cheap to buy taps.

Smaller taps I just use my one of my smaller Super Chucks. Gripping taps is where the ball bearing chucks really excel. And I don't allow them to spin, I've rebuilt several that were ruined by allowing it to do so. For actual drilling, I prefer the plain bearing Jacobs (from before Danaher killed the quality) or Albrechts.

[MotorradMike]

When holding a tap in a Jacobs chuck, I always used the "spin factor" as a poor man torque limiter. Now, this is using a ball bearing style Jacobs chuck, tightened about as hard as I can twist the key.

It seemed to work out about right that when the tap starts spinning in the chuck, I am doing something wrong; pushing too hard, not pushing hard enough, flutes packed full, dull tap, hole too small etc.

If I really need to twist the tap harder for 1 or 2 holes, I will start the tap with the chuck to establish alignment and then finish with a tap wrench.

Dave

I agree, but what do I know?
When the tap slips in the chuck, hand turning the chuck in neutral, I know it's time to back out, clean out the chips and go in again with the tap handle.
Thanks Dave for articulating this. If my chuck grabbed the tap hard enough, it might break. New problem.

[Evan]

The tap won't break if it is of good quality and the hole is the right size and the material is within the capability of the tap. You need to make some tap holders like this:



The hex shaft is just an old screw driver bit driven into a slightly undersize hole in the short piece of mild steel bar. The tap has a small flat ground on it opposite the markings. I wouldn't be without them in the common sizes. Great for freehand drill tapping too.

[8ntsane]

Evan, that is a slick tool you made up.
I now have a new project this weekend, thanks for showing.
Allways things to learn from you!

Paul