Carbon fibre threading improvements?

hi all, We make many carbon fibre components, some with around 80 tapped holes blind and through in a range of sizes. these are currently thread milled with ticn-coated treadmills.
This works well but is very very time consuming keep adjusting cutter comp to size them.
~Also puts all the pressure on the machinist to keep adjusting cutter comp as you know one digit wrong and the part is scrap. One of our ops is around 30 mins to run the whole thread milling program, then adjust and re-run, hours of work...

Are there any taps out there for rigid tapping in carbon fibre that produce a good thread and not de-laminate the top few layers of carbon.
We have tried with many different taps but find they always slightly de-laminate the top skin, on safety critical areas in our industry this is not acceptable.


any help or experience would be great

Countersink the first few layers with a diamond abrasive countersink first. Then try to run a tap. But it seems to me the nature of laminated carbon will not lend itself to using regular taps since it will just delam the fibers rather then cut them.

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always slightly de-laminate the top skin

just delam the fibers rather then cut them.

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hy k-turner :) warenb's idea about the countersink seems nice; even so, a countersink could lead to same delamination; carefull with not visible delamination

is one thing to plunge a countersink/tap, and another to interpolate the chamfer/thread, thus there is a balance between cutting forces and time

to make that tap work with less delamination, it has to be more sharp, have longer entrance ( conical zone ) and less calibration teeth ( cilindrical zone ); you could take a tap and grind it so to have a single helix, thus it's cutting force will be as low as possible, but you may not be able to guide it if there is overhang

to make your process work, you simply need to find a tool that has cutting force as close as your actual method of intepolation :) you will have to test many taps

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Also puts all the pressure on the machinist to keep adjusting cutter comp as you know one digit wrong and the part is scrap

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i suggest :
... checking the consistency of the process, and mapping things as needed, so to identify & eliminate time waste
... avoid error related to inputs, by using a macro that checks offset deviation, and an incremental aproach for final finishes, that simply increases the toolpath radius, without requiring the operator to always modify ++++ then ---- at a new part; if process is stable, is possible to bound it's corections, and speed up or at least partially replace operator's actions

such actions can ease the operator, and works as long as deviations follow a previsible pattern; there may be burs, lack of thread rigidity

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some with around 80 tapped holes blind and through in a range of sizes

One of our ops is around 30 mins to run the whole thread milling program, then adjust and re-run, hours of work...

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at 1st glance, time seems fine

you can boost feed by adding one more tooth, thus instead of experimenting with taps, simply use denser threadmills, at least for orughing

consider also finish with different tool / kindly :)

Hi KT - Do you have design input to the parts? If so consider using a CF veil or glass veil on the top layers. This will produce a layer that has less chance of delaming. Veils come in 25gsm thru to 100gsm and can be very useful for this sort of thing.... Peter

This gives me an idea. I have a whole box of form metric mills. I'll get some scrap and see how it works.