Drilling and Counter sinking Carbon Fibre

[bretts]

Any tips on the best way to drill and especially counter sink carbon fibre?

It's for 4-40 screws but I'm not sure of the angle, 90-100 deg I suppose.

What the best tool and what size gives the best results without it being 'loose'.

Any help with be much appreciated.

Cheers


Brett

[mattr]

100 degrees as far as I can remember.

[danielc3009]

To drill a hole I put the carbon fibre on a old block of would and use a a pillar drill (a hand drill will be fine) to make a 2mm pilot hole. Don't use too much force when breaking throught the bottom or the carbon fibre will splinter. Then I use a Dremel with a 3mm diamond covered grinding tip to enlarge the hole from both sides for a nice clean hole.

If you don't have a Dremel then make the pilot hole and use the final size drill bit from both sides for best results.

To countersink a hole use a good carbon carbide counter sink bit. You can do this with a hand drill but be careful and keep the drill straight so it doesn't wonder off centre. For best result use a pillar drill to prevent it wondering

[Essex2Visuvesi]

once completed you would be wise to seal the exposed carbon with superglue... The brush on type is perfect for this task

http://www.ebay.co.uk/itm/LOCTITE-Su...item232709acc9

no association with seller, just used as a quick example of product

[neil_p]

Head angle I'm sure is 82 degree, if you don't have that cutting tool a 90 will do, but it won't support the head well and all the pressure will be in a small area at thinnest point. If the cf sheet is not very thick, the countersink taper will be knifed edged and it will be very easy to be a de-lamination point. Probably ,ADR this sound drastic, but if the screw is done up very tight it will damage the material with a 90 degree cut.

Like Daniel said, use some wood, but if you clamp the sheet down on wood that hasn't been drilled, when the drill tip breeches thought the material it is less likely to splinter. Constant high speed and not too much pressure will also help. From memory, carbon is best drilled with a dagger type drill but at work I use normal hss and they work no problem.

[dodgydiy]

i dont use a dril, i use a handheld countersink tool as it can be much too easy to go too deep on carbon, and its really really annoying when you are nearly finished on your piece and the endstop slips on the pillar drill while countersinking............................
different makes of screw seem to have all sorts of different angles, my two hand tools match associated imperial and xray metric, but seeing as they are hand tools, others can be made to fit perfectly using deliberate innacuracy!! i always seal the holes with cyano afterwards to avoid splintering and delamination

[bricol]

As mentioned, imperial screws use an 82 degrees countersink.
Metric screws are 90 degree.

Bri

[danielc3009]

Originally Posted by neil_p

Head angle I'm sure is 82 degree, if you don't have that cutting tool a 90 will do, but it won't support the head well and all the pressure will be in a small area at thinnest point. If the cf sheet is not very thick, the countersink taper will be knifed edged and it will be very easy to be a de-lamination point. Probably ,ADR this sound drastic, but if the screw is done up very tight it will damage the material with a 90 degree cut.

I would worry about the countersink angle too much, just get as close as possible.

I made a chassis for my 1/12 car that uses imperial screws using a 90 degree countersink bit over a year ago and have never had a problem with it. I did seal all the holes and edges with super glue to prevent de-lamination.