Talk Composites - The Forum for Advanced Composites

Drilling through multimaterial complex holes

http://www.talkcomposites.com/Topic31775.aspx

By Jones - 1/22/2019 9:56:06 AM

I'm looking to join two matching 3d shaped carbon fiber sheets together with M4 screws and threaded inserts (the threaded insert can't stick out on either side) and I need a few hundred of those holes...

The stack I will drill through is:
one sheets is 1mm carbon and glass and the other is 1.5mm carbon, 5mm solid epoxy (core), 1.5mm glass.

The shape is not flat so a drillpress is not an option. The space for a drill cup is also probably to small. But on the other hand perfect 90 degree holes are not necessarily needed. It might also be hard/inconvenient to strap a waste board on the backside to prevent chip-out/blowouts because of the shape

So my question is how do I tackle this the best possible way?
I guess making a jig to locate and clamp down the two pieces in place.
Find a suitable M4 drillbit that lasts, ideally one that doesn't produce blow-outs and is self starting
Drill through both sheets.
Enlarge the hole in the thicker carbon piece and find a suitable threaded insert.
Hum...

 
By Jones - 1/23/2019 1:33:54 PM

 
scottracing - 1/23/2019 1:24:36 PM
ideally you need to be looking at PCD or carbide cutting tools for this, especially with the amount of holes you are producing.
What inserts are you using? are they parallel bushes or top hats? and what are you using to bond them in?



Are they robust enough to be used in a regular hand drill?
The core is just 5mm solid epoxy and 3-4 600 gram plies top and bottom. Well it can't be sticking out either side and most M4 inserts are longer then the 8 mm plate, so I'm not sure what is best or how to get around it...