Drilling and Counter sinking Carbon Fibre

bretts · #1 10-02-2015

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 · #2 10-02-2015

100 degrees as far as I can remember.

danielc3009 · #3 10-02-2015

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 · #4 10-02-2015

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 · #5 10-02-2015

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 · #6 10-02-2015

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 · #7 10-02-2015

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

Bri

neil_p · #8 10-02-2015

Quote:

Originally Posted by 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

Don't think anyone mentioned using a drill bit to countersink, that really isn't a good idea, for example a hss drill is 135 degree. To do a perfect job every time use a countersink cage.

http://www.aetools.co.uk/categories-...g-tools-16.php

mattr · #9 11-02-2015

Funny, the only drawing I could find of a 4-40 had a 100 degree countersink.

danielc3009 · #10 11-02-2015

Quote:

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.

bricol · #11 11-02-2015

It’s true – there is a 100 degree countersink (well, 99-101 degree) but it’s not exactly common. In 20yrs of working in engineering, including 5 years in the US, I’ve never used it.

Not impossible though, but I’d hazard a guess as more unlikely than the more common standard of 80-82 degrees for Ansi standard screws. If you get bored, google ANSI B18.6.3 for specifications of both types.

You can buy 100 deg countersink bits in the UK – but probably only from proper engineering suppliers – and they won’t be too cheap. Mind you, proper 82 and 90 (90-92 deg) ones aren’t either.

Bri

androo · #12 11-02-2015

get yourself a carbide drill bit and diamond coated countersink.
Any new HSS bit will be blunt in a matter of minutes. I've always used a pillar drill to drill and countersink parts as you can go in square to the part and can control the depth you require by setting a stop on the drill or by eye.

good luck with your project

Essex2Visuvesi · #13 11-02-2015

http://www.ebay.co.uk/itm/4PC-COUNTE...item4ab5ee99b2

I normally use a hand held countersink.... far more controllable

neil_p · #14 11-02-2015

Quote:

Originally Posted by mattr

Funny, the only drawing I could find of a 4-40 had a 100 degree countersink.

Yeah just as funny, thought I would confirm with a google search and the entire first page results said 82 degree.

100 degree heads are more common in riveting, and you can buy pilot 1 piece cutters for this head angle. Never checked if you can get them in 82 degree.

As the other guys say, use a pillar drill, especially if your not used to drilling a lot. If you comfortable then it's not an issue to go through by hand. You really cannot go wrong with an adjustable guarded cutter, you will get exactly the same depth cut each time. with drill bits, if you use Dormer or Presto bits and don't put too much pressure on the drill they will be fine, also a cutting fluid should help. Hope I haven't over complicated this for you and good luck with your build.

bretts · #15 11-02-2015

This is great & very useful, thanks.

I've only 4 new holes to drill and sink, but want a tidy job.

Time to get some new bits & sinks, a piece of wood and Bobs Super glue to hand!

Thanks again.

Mike2222 · #16 12-02-2015

and maybe use threadlock to keep the screws in place....

bretts · #17 12-02-2015

Quote:

Originally Posted by Mike2222

and maybe use threadlock to keep the screws in place....

ho ho yeah ok mike sorry....that wasn't my car tho, I was just trying to drive it

. it can happen to anyone....Clicky

joolstacho · #18 25-02-2015

+1 to use cyano after drilling. Depending on the CF you use, it will probably be porous after drilling. Use THIN cyano to 'wick' into the drilled/cut edges to seal them.

bretts · #19 25-02-2015

All done, and pleased with the result.

Drilled with 2mm bit first and then 3mm bit, then used 3 diffent sizes of counter sink to get the perfect fit by hand.

Finshed by a bit of bob's glue to seal.

Glad I only had a few holes to do as it took a bit longer than thought.