Author Topic: Drilling large holes in carbon  (Read 41 times)

Alex Manuel

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Drilling large holes in carbon
« on: December 24, 2017, 01:29:46 PM »
Am planning to use a 12" carbon fiber tubing for my astrograph.  Reasons for using it: rigid, low thermal expansion and low weight.  etc..  No debate on that problem imho.  However, I want to generate some large holes (3" (75mm) - 3.6" (90mm) up to 4" (100mm)) in the tubewall.  Small holes are rarily a problem.  Only use a HSS drill, drill rate really high, vacuum cleaner and you're finished.  However, with the large holes I fear for delamination of this tube.  Any suggestions of how to do this?  Let us say I have a good milling machine that can pick up the tube or a drill press.



uncritoges

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Re: Drilling large holes in carbon
« Reply #1 on: December 24, 2017, 04:35:22 PM »
Quote
Just use a HSS drill, drill rate very high, vacuum cleaner and you are done.
 
you should really use plexi pieces, pieces which have 0?? rake angle and therefore are more than the normal 135?? tip, usually if I remember properly 60?? tip.

Shane Proulx

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Re: Drilling large holes in carbon
« Reply #2 on: December 28, 2017, 10:57:55 AM »
Thanks for that hint, but let's focus on the big holes.

tiostaralzo

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Re: Drilling large holes in carbon
« Reply #3 on: December 30, 2017, 04:23:03 AM »
Contact Frank Uroda at Public Missiles, Inc., he can tell you how. I bought my 12.61" x 45" CF tube from him. Small mounting holes (like 1/4") drill with regular drill bits, but I don't know about large holes.
Mike

hoidingsikva

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Re: Drilling large holes in carbon
« Reply #4 on: December 31, 2017, 05:23:26 PM »
Diamond hole saws like you would use to cut holes in glass aquariums. You can get pretty cheap ones that will be good for a few uses.

Like this: http://www.ebay.com/...loAAOSwQJhUdOtt

Eric Mannasseh

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Re: Drilling large holes in carbon
« Reply #5 on: January 01, 2018, 05:41:43 AM »
Thanks Mike. BTW, send you a few weeks ago the design of my telescope via e-mail. Didn't get any feedback on it. Got any? (Via PM)

Elroy Stockton

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Re: Drilling large holes in carbon
« Reply #6 on: January 04, 2018, 09:30:38 AM »
if your not afraid of the rake angle of a normal HSS drill bit then the angle of the teeth on a bimetal hole saw shouldn't scare you either, just cowboy it.

adlaycomsu

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Re: Drilling large holes in carbon
« Reply #7 on: January 08, 2018, 12:51:10 PM »
It is not a matter of rake angle, it is a matter that I can spend my money once only. And I'd rather spend it on multiple small holes than on multiple large ones.

satimoja

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Re: Drilling large holes in carbon
« Reply #8 on: January 09, 2018, 11:00:49 PM »
Another option is to find a PCD coated burr that fits a dremel and use that to "route" out the hole. I have used these:
http://www.ebay.com/...zkAAOSw1KxXMoOY

Michael Shen

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Re: Drilling large holes in carbon
« Reply #9 on: January 10, 2018, 04:04:25 PM »
Anything with teeth will grab and tear at the fibers.

maulaepretag

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Re: Drilling large holes in carbon
« Reply #10 on: January 12, 2018, 04:44:52 AM »
Does anyone know if boring is possible in carbon?

spicomgeovio

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Re: Drilling large holes in carbon
« Reply #11 on: January 13, 2018, 04:21:25 AM »
Benach,

You can try a small hand-held rotary tool, such as Dremel, with abrasive disks.

Such disks will cause the least amount of edge damage.

Even with clean holes you'll still have to finish the edges with sanding blocks and sanding sheets available from speciality suppliers for that material.

For accurate cuts, a jig will be needed.

Metal tools such as saws, router bits, drill bits, etc, with will dull very quickly, even stainless steel, so they're best avoided.

Straight abrasive bits are best for cutting drills and coping or jig saws.

Regular serrated jig/coping saw blades will leave a better edge but will clog up very quickly with resin.

Wearing a respirator during the process is no-brainer.

Mladen

coatiorachin

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Re: Drilling large holes in carbon
« Reply #12 on: January 14, 2018, 04:12:06 AM »
Quote
Does anyone know if boring is possible in carbon?

Boring should be possible using a mill-mounted boring tool, but will dull bits very quickly. It may even tear the edges at the end of the hole. A 4-inch diamond hole saw may work better, but it's not accurate. It will also tear the edge at the bottom of the hole unless the bottom is somehow supported with a backing plate.

Mladen

Alex Manuel

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Re: Drilling large holes in carbon
« Reply #13 on: January 16, 2018, 05:07:18 AM »
Oh well, that solves it perhaps then. A selfmade boring tool that fits in the mill with a diamond toolbit and a huge MDF plug or similar inside the tube. At least this is worth a serious try.

housletica

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Re: Drilling large holes in carbon
« Reply #14 on: January 25, 2018, 01:34:57 PM »
They make bits specifically to cut carbon fiber composits!!!

In doing all of the CF work on building the 20 inch RC I used
bits in the CNC Router from Starlite, brand name Starbide 1/4inch
part number 452522 and they left an excellent edge and did not tear
out.

I would not use a diamond tool bit in a milling fixture!

Make a jig for a router and cut the hole with the bit above.
They are about US$20 per carbide bit and I cut all of the parts
used in the build with only one bit...it did not dull at all.

Best Regards,

Preston