question about tap life

[dielant]

Can anyone tell me how many times I can use a TiN coated 0-80 hand tap (working length 1/4") before I need to worry about wear and/or weakening (assuming I only use it on aluminum)? Thanks

[djr76]

Normally you wouldn't use a tin coated tool for aluminum since the material easily welds to the tool itself. Hard to say really, there are lots of variables to consider. SFM, lubrication, material of tap, material you're cutting, coatings, style, manufacturer ect. ect. I guess best person to ask would be tooling supplier and/or manufacturer of the tap.

[fizzissist]

First, I wouldn't use TiN on aluminum. Second, 1/4 is awfully deep. You sure you need that kind of depth? There's some serious design issues with that.

Third, hand taps suck.

Now, what alloy of aluminum? Floating holder, rigid tapping, lead screw tapping, or are you actually doing it by hand? How accurately can you control the tap drill diameter?

One serious thing to consider would be a thread forming tap, and a metric sized tap drill (for an easy 65% thread) if you really need that kind of depth.

[mc_n_g]

I would doubt the tap will last long enough to wear enough...you will break it first.
I second the forming tap suggestion but with one caveat, if you do not have a good set of drillbits that hold size you will not be able to do it. Another large factor in this is the quality of your drill press spindle to stay centered (runout) with very little play.
If you do not have a good set of drillbits buy the individual drillbit sizes you need. Form tap holes are not the same diameter as regular holes for cut taps.