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Thread: best way to drill through fiberglass?

  1. #11
    BADBLOWN572
    I never use tape. I find that it gets in the way and is pointless. An agressive hole saw will tear apart the tape anyways. What I do is to find out where you want the hole to go. Pilot drill the hole with a 1/4" drill bit. Once you get through, take a hole saw, spin it backwards on high gear. A tip is to find a mandril (?sp) that has the ability to change out the pilot bit. I always remove it and throw in a standard drill bit. The extra 1" worth of length makes a big difference. Once you get going in reverse, wait until you get completely through the gel coat and are into the fiberglass. At that point in time, you can start spinning it forward. Apply LIGHT pressure at a high rate of speed. Drill through the hole. If you put too much pressure, you can blow the back of the glass off.
    Good luck.

  2. #12
    GofastRacer
    I never use tape. I find that it gets in the way and is pointless. An agressive hole saw will tear apart the tape anyways.
    Of course it will cut the tape duhh, the idea is not to chip the gel and is not pointless, why make a no brainer thing so damn complicated!...

  3. #13
    Racey
    I'd say oh i don't know,..........maybe a 9/16 drill bit.
    Hey, you stole the words right out of my mouth.
    use pilot holes as well, step your way up to the final 9/16 with a couple intermediate sizes. You can use some masking tape on the gel to help with chipping

  4. #14
    stickmann
    Use a drill press and run the proper sized hole saw through a 3/4" chuck of plywood. Clamp this over the place where you drilled your 1/4" pilot hole. Use the hole saw with a 1/4" pilot drill blank to holesaw through the fiberglass and plywood backing in the dash. You will not chip out the gelcoat and you will not blow out the backside, if you are careful. It tends to make a hole which is square to the dash and most importantly....round. Pretty and accurate; that's how patternmakers do it.

  5. #15
    Senior Member
    Join Date
    Feb 2009
    Posts
    3,387
    You should always let the tool do the job (Whatever tool is used), however, too much pressure will cause problems (chipping cracking)!
    plain and simple!
    Hole saw, drill bit,....lol "DREMMEL"!
    I like tape, paint/gel jobs are not cheap, and use alot of it!!

  6. #16
    YeLLowBoaT
    You should always let the tool do the job (Whatever tool is used), however, too much pressure will cause problems (chipping cracking)!
    plain and simple!
    Hole saw, drill bit,....lol "DREMMEL"!
    I like tape, paint/gel jobs are not cheap, and use alot of it!!
    actaully dremil would wokr pretty dam good with thier circle cutting attachment... just take about 10 passes. I use my router and a circle cuting jig when ever I have to make a bunch of holes in stuff.

  7. #17
    BADBLOWN572
    Of course it will cut the tape duhh, the idea is not to chip the gel and is not pointless, why make a no brainer thing so damn complicated!...
    Well, he asked how to do it and I responded. No offense, but after drilling probably 10,000+ holes in boats, I would think that I might have a little bit of knowledge & experience others don't have. No matter how much tape you use, if you are using an agressive hole saw & don't spin the holesaw in reverse, you stand a good chance of chipping the gel coat.
    To me tape gets in the way if you are drilling holes. I lay out a dash on tape, drill my pilot holes, then pull the tape off of the dash prior to drilling. As long as you spin the hole saw backwards before you actually begin cutting, you won't have a problem. You can see what is going on with the gel while you are doing the task. I do not recall the last repair I have had to have done on a boat that was the result of drilling with a hole saw.
    The only time that I use tape is if I am cutting something with a sawzall, jig saw, circular saw, etc... Anytime something is going to be sliding across a finished surface. Then, not only do you tape the area you are going to be cutting, you also tape the feet on the saw. That way you are double protected. Definitely use some sort of painters tape or heavy duty tape. The $.99 tape from harbor freight probably won't work.

  8. #18
    GofastRacer
    Well, he asked how to do it and I responded. No offense, but after drilling probably 10,000+ holes in boats, I would think that I might have a little bit of knowledge & experience others don't have. No matter how much tape you use, if you are using an agressive hole saw & don't spin the holesaw in reverse, you stand a good chance of chipping the gel coat.
    To me tape gets in the way if you are drilling holes. I lay out a dash on tape, drill my pilot holes, then pull the tape off of the dash prior to drilling. As long as you spin the hole saw backwards before you actually begin cutting, you won't have a problem. You can see what is going on with the gel while you are doing the task. I do not recall the last repair I have had to have done on a boat that was the result of drilling with a hole saw.
    The only time that I use tape is if I am cutting something with a sawzall, jig saw, circular saw, etc... Anytime something is going to be sliding across a finished surface. Then, not only do you tape the area you are going to be cutting, you also tape the feet on the saw. That way you are double protected. Definitely use some sort of painters tape or heavy duty tape. The $.99 tape from harbor freight probably won't work.
    Hey, whatever works!.....

  9. #19
    superdave013
    That sanger has to already have plenty of holes drilled in it.
    Don't drill anymore in the dash is my $0.000001.
    If you must have a key switch can't you just swap put the push button that is already there? If not make a little bracket and catch a bolt on the rail kit, some place on the engine or maybe one of the many bolts by the seat / v drive.
    But for the sake of the next guy, please don't drill any more holes in the ol girl!

  10. #20
    thatguy
    Damn, He's probably scared to death now.
    I just did my first hole, 1 1/4" for a bilge pump outlet.
    Was scared because it is the nicest boat I have ever owned.
    Used a hole saw, drilled pilot hole the same size as the hole saw pilot bit.
    Taped it, but I agree the tape did nothing.
    Spun revers and LIGHTLY went through gel and glass.
    Spun forward and went Most of the way through.
    Then finished from the inside.
    Worked perfect.
    Tommy

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