I need tap holding advice for the mill

thank guys. That's a lot to take in.
My mill is a PM 940 V. It has an R8 spindle.
I looked for R8 collets for tap holding but didn't see any.
I did try tightening using all 3 holes and even used a cheater pipe on my chuck wrench. No good.
These are blind holes and I fill them up with Tap Magic cutting fluid.

The fact that my drill bit slips too makes me think , maybe I need to try a different chuck?
I liked the tap holders in the picture that had the nubs for putting in a chuck.
They would keep it straight but I don't think the nub would hold the torque. It gave me an idea though.
Maybe I could modify one and make that part longer?
 
Better off using collets for tapping . Make up a split sleeve for the tap and use a 3/4" or whatever size for the tap shank OD . Use dark oil if you can .
 
scattermaster said:
thank guys. That's a lot to take in.
My mill is a PM 940 V. It has an R8 spindle.
I looked for R8 collets for tap holding but didn't see any.
I did try tightening using all 3 holes and even used a cheater pipe on my chuck wrench. No good.
These are blind holes and I fill them up with Tap Magic cutting fluid.

The fact that my drill bit slips too makes me think , maybe I need to try a different chuck?
I liked the tap holders in the picture that had the nubs for putting in a chuck.
They would keep it straight but I don't think the nub would hold the torque. It gave me an idea though.
Maybe I could modify one and make that part longer?
Click to expand...
Blind holes for pipe tap? …….
A good sulferized cutting oil helps.
 
Tapping a a tapered thread is torque demanding as the entire length of the thread is being cut. I would drill the hole out in the mill and without moving the table, use a tap follower and a tap wrench rather than attempting power tapping.

You mentioned that the holes are blind. Are they deep enough to allow for fully tapping? What is the tap material? Carbon steel taps aren't recommended for tapping new threads. Is your tap new? A dull tap will require higher cutting torque and produce a poor finish. What is the material you are tapping? Some steel alloys are notorious for poor finishes..
 
Pipe taps are hand taps, they're not designed for power tapping. They need to be backed off to break the chip every half to full rotation. There's a good chance the threads will strip out otherwise.

I have had good luck with these piloted spindle tappers.
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+1 on the tap wrenches MrWhoopee showed above. I suspect your pipe tap has a square end on it in anticipation of needing more torque than you get from holding it in a drill chuck. The tap wrench won't slip, the piloted center keeps you straight too. They're my go to on the lathe. I power tap on my Bridgeport using a drill chuck on 5/16"-18 (in aluminum) and smaller like you did. I go to the piloted tap wrench for anything bigger.

Bruce
 
ER tap collets. They engage the square on the shank. Morse taper tap drivers are also available.
Reaming to the correct taper also helps.
 
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