Correct Method for Drilling Fiberglass

[Ranman]

Would somenoe tell me the correct way to drill a hole through the cockjpit liner? I have new grab handles coming for the rear seat passengers and need to know how to get a clean mounting hole. Last time I drilled into the cockpit liner
(small hole). The gel chipped away quite a bit and did not leave a nice round hole. I have acces through the speaker openings so the handles will be thru-bolted with backing plates. Do I put tape over where I'm going to drill? Do I start with a pilot hole and then go larger (5/16 hardware)? Driull speed fast or slow? Thanks for the help.

[Greg K]

Tape helps, but run the drill backwards first to elimanate the chipping.

[Tom Davis]

Randy,

Real simple answer to this question! There are drill bits that you can buy that cut from the outside in. They have a small pilot in the middle to get started then instead of a convex taper the lead cutting edges start at the outside and are concave to the center pilot. I have used these to drill all the gel and glass work I have done and they don't chip. Give me a call or an e-mail if you have any questions.

Tom Davis
Winni Bandits

[Greg K]

Those bits would be similar to the Black & Decker Bullet bits.

[MOP]

The bits Tom is talking about are the best thing since sliced bread! If you do not have them what you can do is to sharpen the drill at at very shallow ramp angle, this and very very light pressure and tape will work. That was all we had, a lot of the not chipping is in the feel.
I know you will be bolting but when using self tapping screws once the holes are drilled take a counter sink and again with very light pressure cut away the gel just until you hit the glass underneath. Failure to do so it will chip off big chunks from the screw pushing the ridgid gel outward.

Phil

[Bob]

Use sharp brad point bits, slow speed, scrap wood behind the hole to minimize chipping.

[KRAVEN]

Start dill in reverse until thru gel,then finish hole in forward.Finish by countersinking gelcoat this will eleminate future stress cracks.Don't forget the 3M 4200 fast cure. :kaioken:

[Brad Lyon]

Randy! Half of the fun of owning these boats is watching your rear seat passengers holding on for dear life. Why on earth would you want to put grab handle's back there.

:eek!: :eek!: :biggrin.: :eek!: :eek!:

Brad

[harbormaster]

They are probably for the new in-laws... :biggrin:

[Ranman]

Thanks for the replies. Does anyone have a link to the recommended bits? If I can find them, I'll use them. If not, I'll go with the "reverse" method.

It should be a crime to allow people to ride in the back seat of these boats with nothing to hold on to. I'm sure the future passengers will thank me. :wink: :wink:

[Tom Davis]

Sure Randy,

It is a standard DeWalt product # DW1956 (16 piece pilot point drill set). Well worth having in your shop if you do any work on fiberglass.

Tom Davis
Winni Bandits

[RickR]

Like Kraven said ,countersinking and the correct size drill bit are VERY important to prevent gel coat and fiberglass from cracking!

For small holes I countersink with a phillips bit in a drill.

[Lenny]

Randy, use taper bits. I use them for drilling FINISHED WOOD doors and drawers from the outside in and they DO NOT blow out or chip, or fuzz anything. The hole is perfect. The tip is tapered at the start from quite a sharp point, (can cut you on touch) to the required dimension of the drill bit. They come in all sizes. The only thing to be careful of is they have a lot of grab once they clear the taper part. Have some restraint handy. They will NOT hurt or chip or cause you any grief on the gel-coat. 5/16, or 3/8 is no problem. They start very small in diameter in availability and go to 3/8 I believe. I have most of them. They are made by Fuller.

http://www.jamestowndistributors.com/eserv/eclipse.ecl?PROCID=WEBDISP.WOEB.MAIN&ID_1=5&ID_2=1466&ID_3=1588&ID_4=1602&CLEV=4&TRACKNO=J8949869281

http://www.amazon.com/exec/obidos/tg/detail/-/B0000224EN/002-5678580-0568008?v=glance&s=hi&me=ATVPDKIKX0DER&vi=pictures&img=14#more-pictures

I buy them loose in all sizes. You don't need a fancy kit. Noe the countersink in your case. Just a 5/16 taper bit by Fuller.

http://www.jamestowndistributors.com/decoder_csink.asp

[Ranman]

Thanks again for the replies. I have a couple more questions.

The monting hardware is 5/16. My drill chart tells me for a clearance hole to use a letter Q drill (.332). The Dewalt kit has nothing even close to a Q drill and only offers a 5/16 bit.

The Fuller taper point bits don't seem to offer a letter Q bit either, but they do have a 21/64 (.3281). I assume a 21/64 bit would make an OK clearance hole for the hardware, right? Also, I have a standard set of machinist's countersinks. Will these be OK to use? Thanks again.

[Brad Lyon]

Randy,

The 21/64 drill will be fine, you could even go up to a 11/32 (0.3437).

Brad

[Lenny]

Randy, they have countersinks of various sizes, I didn't know you needed that as well. These bits are SHARP. The countersinks come in #6, #8, #10 etc. They are set with an allen key wherever you want on the bit itself. Be careful if you use these bits/ countersinks as they will go through quickly and cleanly.

[Ranman]

The fuller countersinks that attach directly to the bit are expensive. I have a standard set of countersinks. I think those will work fine. Thanks.

[MOP]

Randy another thing that works nice for counter sinking is couter sink stones, they do not hop or grab.

Phil

[DonCig]

I picked up these Hitachi countersink drill at Lowes.

I have drilled over 32 perfect holes with them. The technique that I use is as follows:

1. Put painters tape on the fiberglass where you want to drill. I prefer blue painters tape over duct tape. No sticky residue and a cleaner cut.
2. I start the drill bit in reverse until I have cut thru the Gel about 1/8".
3. Switch the drill into foward and finish the hole and then push down smoothly so that the single countersink cutting edge can cut thru the gel to the wood or fiberglass below. See photo below.
4. Remove Tape.
5. I like to smear a little bit of a hard hand soap bar on the screw threads before installing the wood screw. It makes it go in smooth and easy.


DonCig

[joseph m. hahnl]

Thanks again for the replies. I have a couple more questions.

The monting hardware is 5/16. My drill chart tells me for a clearance hole to use a letter Q drill (.332). The Dewalt kit has nothing even close to a Q drill and only offers a 5/16 bit.

The Fuller taper point bits don't seem to offer a letter Q bit either, but they do have a 21/64 (.3281). I assume a 21/64 bit would make an OK clearance hole for the hardware, right? Also, I have a standard set of machinist's countersinks. Will these be OK to use? Thanks again.

.004 smaller wont make a difference. althoe the smaller the hole the more precise the hole location must be.

joe