Tension/compression tap holders

[Caprirs]

I rigid tap small holes in aluminum often. Typically only a few holes per part and maybe a hundred parts per week. Normally, the threads are 4-40 and I drill with a .101 drill then use a form tap GH6 (the parts get anodized so I go big) held in a DA collet and spindle speed is 1000rpm. Flood coolant is always used.

If I go faster than 1000rpm, the threads get stretched and I increase the frequency of tap breakage. Running the spindle in air above the part and slowing the rpm, I can see that the rotation isn't exact by the "bottom" of the hole. Maybe off by a few degrees. I'm guessing a tension compression tap holder would be beneficial. Any recommendations on brands? I've never used anything but a rigid holder and have no experience with the flexible gizmos. Thanks.

[HuFlungDung]

Here is a manufacturer that I have become aware of lately. His pricing seems very competitive, but I already had enough toolholders by the time I heard of him.

http://www.maritool.com/floatingtap

[Eurisko]

We used to use tension-compression holders, tapping blind holes in cast iron.

The problem we had was that as the tap wears, more force is required to cut the threads.

This caused the holder to compress more.
Couldn't maintain the thread depth.

Roll tapping requires quite a bit of force, since the threads are being formed by pressure.

I'm just not sure how the TC holder would work in your application.

Alternatively, you might try a tension-only holder.

[Caprirs]

The Maritool one looks very nice. Similar to the ones in MSC and US Shop Tools catalogs. Unfortunately, it has 1" shank which is huge for my machine which uses CAT30 tool holders. Are you aware of any similar tools with a smaller shank?

Aluminum is the bulk of the parts I make by far so I don't worry about much tool wear. What is the advantage of the tension-only other than likely to be less expensive?

[dfstrasser]

In my opinion, tension only is the way to go. I have had instances when using tension/compression holders, where the tap does not immediately start, the unit compresses, and the thread depth is reduced.

I have had very good success with ER style tension only tap collets. I know Techniks has them in quite a few sizes. They are very durable and work great. I usually program the pitch 95-98% of the actual and allow the holder to float while going in. I retract at 100%.

[cdlenterprises]

Generally anything from Parlec is good but $$$. What about a tapmatic tapping head?

[Caprirs]

I perceive the Tapmatics to be overkill for the parts I'm making. Here's some examples of the parts I make: http://evlgt85.com/gallery/MC_Machine_Samples/ Quantities are 50 pieces at the most with 4 threaded holes in each. What I'm concerned with is thread accuracy and not breaking the tap.

Someone local to me recommended the tension compression holders as an option.

[dfstrasser]

The best solution is to find out why spindle/axis position is off and fix it if possible. Then you can continue to rigid tap and don't have to spend money on tooling.

If you can't find or fix the problem, Tapmatic makes a holder called "Synchro-Flex". It's basically a helical coupling between the tap and spindle that allows for minor differences in the speed and feed. They are expensive, but work as advertised and last a long time. You can find info. on their website that explains everything. You may be able to get them to give you a performance guarantee where you can return if if it doesn't work to your expectations.

I have bad experiences with tension/compression holders. They may work great in you situation, but I had lots of problems in high volume applications. I spent thousands and thousands of dollars before I switched to tension only ER tap collets. The collets held up very well and the quality issues were gone. Every application is different.

[newguy81]

One thing to remember with the tension & comp. holder is the length. Bilz and Lyndex have short one's. Longer ones get in the way more and seem to give more in the comp. end.