Drilling PEEK 1

[inventeer]

We're seeing a lot of tool wear using HSS jobber drills with TiN and Nitro-Carburized surface finishes to drill PEEK.

What is the recommended drill for drilling 1.25mm diameter x 12mm deep holes in PEEK with maximum precision and minimum tool wear?

I'm considering trying carbide, but haven't found a 1.25mm drill yet.

What do you suggest?

Thanks!

 

[MikeHalloran]

For one thing, you can't use them to drill anything else, even once. Tools for plastic need an edge that will draw blood.

.. which is why carbide may be a disappointment; too big an edge radius.



Mike Halloran
Pembroke Pines, FL, USA

 

[Compositepro]

PEEK should not be hard on your drills unless there is some filler or reinforcement in it. If it is pure resin then Mike is spot on. You need to start with sharp tooling. If there are fillers or reinforcement then carbide is the way to go. Look for drills designed for composite material.

 

[saberblue]

Typically the drill geometry is very different for plastics -- the specific grind will be determined by how hard the plastic is and what kind of chip is produced.You will probably want to grind your own drills once you settle on the geometry you want -- note as you change the grind you will also change the diamiter of the drilled hole - so watch your processes once you have them nailed down.

You may want to look at using a very highly surface active coolant - so that it will wet the drill - it is very difficult to get coolant to flow all the way to the bottom of a hole.

A.R. "Andy" Nelson
Engineering Consultant
anelson@arnengineering.com

 

[Zimmann]

Here is some stuff from machining Handbook that may help you, it's mainly for composite but you'll see that the faced problesm are the same.

Some general guidelines for machining of carbon/epoxy composites are the following:
Carbon/epoxy is abrasive by nature. Therefore, precautions should be taken to ensure that the carbon/epoxy particulate does not propagate into the precision machine/ground ways of the machine tool. The carbon/epoxy particulates can cause not only premature tool wear but machine wear as well.
Carbon/epoxy dust can cause electrical components to short out or malfunction. All electronic components should be tightly sealed and have filter systems installed to prevent problems. Since thermoplastic composites generally form chips rather than particulates, electrical problems have not been experienced with these materials.
The aforementioned machining processes can be completed dry (with vacuum) or wet. When machining dry, a vacuum system must be used to collect the dust particulates to prevent them from becoming airborne. The vacuum system normally used is an ultrahigh-efficiency cartridge- type dust collection system providing capacity of 8.5 m3/min (300 ft3/min, or CFM, at an external static pressure of 7.5 kPa at 20 °C (30 in. H2O at 70 °F) with an overall efficiency of 99% down to a 0.5 ?m particle size. Even with this high efficiency system, it is imperative to remain vigilant of heat buildup or baking of the carbon epoxy particulate to the cutting tool. This problem can cause catastrophic part failure due to degradation and delaminations.
Enhanced tool life results when these operations are accomplished wet. Typical coolants are tap water or Bio-Cool 500 (Westmont Products, Dallas, TX) mixed at a 20-to-1 ratio, applied as flood. Another very important point for consideration is how the coolant will be recirculated during the machining processes. If the machine is not going to be dedicated to carbon/epoxy machining, then every consideration should be given to an auxiliary tank. This will prevent contamination of the coolant tank of the machine, an important point because dust particulates and not a chip form are generated during machining. The particulates form a sludge clogging filters and impeding coolant flow.
If the machine is not dedicated and an auxiliary tank will be used, the tank should be designed to provide a sludge and filtration system that will ensure adequate particulate-free coolant to be delivered to the cutting tool. This type of system will prevent contamination of the primary coolant delivery system of the machine and will also prevent severe corrosion to internal components.

 

[powerhound]

If you try to drill acrylic with a sharp edged drill bit you will definitely have chipping to deal with, especially in the bottom edge of a thru hole.

I'm with compositepro on this one. I haven't had trouble with tool wear when drilling PEEK so I'm inclined to believe there is something mixed into it. PEEK is not brittle like acrylic so sharp edged tooling should work just fine on it.

Powerhound, GDTP T-0419
Production Manager
Inventor 2010
Mastercam X3
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

 

[inventeer]

Thanks for all the help!

It looks like in our case it boils down to having a sharp drill bit.

We're working with a carbide tool now, and getting better results. Stay tuned to see how much life it gives us. It hasn't become dull yet...

Can anyone point me towards guideline for tip geometry vs hole size if we move towards regrinding our bits?

Cheers

 

[saberblue]

If you can replicate the original geometry it will drill as before

However very small changes in drill geometry or material hardness will affect how much the drill "cuts over size"

Make sure you regrind this carbide (WC) drill with a good drill grinding machine ding it by had is at best a crap shoot.

A.R. "Andy" Nelson
Engineering Consultant
anelson@arnengineering.com