Hey guys,
Working on the resto still and need some advice from the people that know best. I'm wanting to drill holes into my fiberglass in order to install a luggage rack but don't want to take any chances on ripping or cracking the area in the process. What do you all recommend as far as drill bits go? Also your experiences will be great. Thanks once again. Hope you are all having a wonderful Christmas time.

 

If I was going to drill any holes in the fiberglass, especially where you would not want any ragged holes. Get a high speed drill bit " New" and as sharp as it is ever going to be , not some old worn out drill bit, as they will rip through instead of "Cut cleanly" through.
2nd thing and very important too. Where you will not have "Tear out" on the back side or very possibly crack the fiberglass. Take a piece of wood and apply an upward pressure to the underside where you are drilling the holes. This might be a two person job and very careful not to drill a hole into the hand holding the piece of wood underneath. The bit will go into the piece of wood but the piece of wood will help you get a clean hole on both sides. Another thought! I believe I would first drill a small pilot hole through the very center of the holes, (Wood underneath used here too!) to make sure the drill bit you actually need to use makes the hole exactly where you want it to be. Especially the first hole. You might be able to use your rack as a guide to drill the holes after you get the first hole, put the bolt in, set the rack exactly where you want it, then one at a time. Make sure the bit is long enough, where the drill don't tear into the rack. Take your time and plan out every thing you are planning on doing where you don't end up with extra holes where they can't be covered up and it looks like a professional did the job. Also make sure the drill you are using is charged up. If you where close by I would let you use my Hitachi 18 volt drill. It would do a great job. Again take your time and plan every move before you drill holes in your car. The piece of wood will not only support the fiberglass but will help if not prevent all tear out underneath. I usually use scrap piece of a 2"x4", and let the bit go into it, instead of ripping out the bottom side of the hole. Do not jerk and ****** on the drill and drill bit if it were to hang up while drilling the holes. The easier you are with the fiberglass the better it will look when you are finished.

hope this helps,
Have a great day,
Ray/aka/Pa

 

use a unibit.
its what we use to mount the race spec fiberglass to our trackbikes.

they have a sharp tip to bite immediatly and the hole gets bigger as you drill deeper.
it makes a perfect hole.

 

When I mounted my luggage rack I had the same concerns. I ended up using a forstner bit instead of the regular drill bits. The forstner bit cuts from the outside in instead of from the inside out. It made perfect holes without any tearout.

 

Would you mark and drill through masking tape too?

 

Any time you use a drill bit on plastic you need a negative rake this will stop all pulling and will stop any damage to the area around the hole.
(Rake is the inside of the cutting edge, it is curved use a grinder and make it flat note the drill will only be good on plastic.

 

thanks alot guys. For those of you who have mounted the racks before, how did you prevent damage to the gas tank directly beneath the rack when drilling? Thanks again.

 

Hi J2,
There are about 2 inches between the fiberglass deck and the top of the tank. Where I mounted my tank the rear 4 holes were just to the rear of the tank and the 2 front holes were just to the left and right of the tank
I used an old fashion hand drill that you crank yourself. I put masking tape over the spot. And, the original rubber well nuts have a little shoulder on them that hides the cut edge of the fiberglass and about 1/8" of the deck around the hole.
Good Luck, it's pretty easy if you're careful.
Regards,
Alan

 

I would use some heavy duct tape, it'll help with the chipping. The glue that is left behind comes off with rubbing alcohol.

 

Safest way to drill into any brittle material is to drill a small pilot hole and then enlarge with a good step bit. Always go slow with the step bit and know (mark it) which step you're stopping at.

 

Use a unibit, with good 3M masking tape on the spot to be drilled. If you can get to teh back side of the hole area, put some kind of a backing materal, a hammer handle, a wood block, rubber block, ets. You should be using a high speed drill and bit. Use light pressure and let the unibit do the work.


BBTank

 

For what it is worth, Use light pressure, the masking tape,the pilot hole, and something for backing material, at least try to tape up the back side and if you are concerned about going to deep. You can get a "Collar" and set the depth that the bit will go. You can very simply take some tape and wrap around the bit about an 1/8"to a 1/4" out from the side of the bit to set the depth and stop it from going to deep and ventilating your gas tank. Use light pressure and a sharp bit.

Ray/aka/Pa

 

Looking back I "Babbled" to much on that other reply Sorry!

Ray/aka/Pa

 

Yes, that's a drill stop.

 

That's how I'd do it, high speed with gentle pressure.

 

I wasn't going to chime in here until I saw this one.....fiberglass gets VERY hot when you drill through using too much speed; it and will INSTANTLY take the edge off a new bit. SLOW speed with light pressure is the key with glass. Sorry to stomp on your post SH-60B (I spent some years on '60s myself)-hope I didn't hurt anybody's feelings!

 

I know I'm not a very popular person on this forum, and that's my fault, not the topic at hand.

I started doing this stuff in the USAF in 1975, I really do have a few small skills.

 

Slow speed will tear the fibers in the glass. If it's a good unibit, which I refered to, it won't harm it at all. If it's a garbage (harbour) freight one, yep, it will. Light pressure will not generate that much heat, slow or fast speed. Try it.
Use tape on the drilling side, tape, hammer handle, wood, rubber block, etc on the back side.

BBTank

 

Actually BBT I was kinda hesitant to post that.....I made that accidental discovery when drilling and countersinking fiberglass 'milk stools' for the space shuttle (really!!!) when working at the Late Great Convair in 1980. When I splained the problem to one of the old coots (grrrr....now I'm one myself!) he told me to slow my motor way down and I'd quit burning up all those bits. Of course, the glass used on those things was a little finer than the stuff Vette bodies are made of...

 

LOL!You didn't hurt my feelings, but I disagree. I work with a lot of composites today, even good old fashioned fiberglass. When a bit breaks through the back side at low speed it will screw itself into the material, and maybe draw the chuck into the work surface. If the fiberglass gets hot while you're drilling it, you have started with a dull bit to begin with. High speed steel bits are cheap and better suited to wood shop. Use cobalt bits with a drill stop and you'll not have problems. Carbide is great and should always be run at high speeds, but it's brittle and can ruin your work if it breaks.