About to hole saw, any tricks ?

[Sven]

I'm probably doing something fundamentally wrong. I have never had a hole saw not bind when cutting a hole.

Tomorrow we hope to start cutting the 3.5" hole in the stern for the Cape Horn and I really want to avoid the binding problem.

http://www.grenander.com/Senta_II/Blog/Entries/2012/3/29_Pilot_hole_drilled_(Sven).html

Right now I'm just hoping that the suggestion that we just run the saw at a high speed and not put pressure on it is the approach that solves the problem, but I have my doubts.

Any suggestions would be welcome, even the ones we might ignore



-Sven

 

[seajunkie]

Gel Coat

Chipping the gel coat is always concern. You might try going through the gel coat in reverse. After making the hole bevel the gel coat to keep it from crazing. I'm no pro for sure, but I did that at the direction of others.

 

[mherrcat]

I would think the hardest part would be drilling into that angled surface; once you break through on the bottom you'll only be cutting a small surface on either side of the hole, which could be tricky and might cause chatter. The hull is probably not thick enough to cause binding, but you will most likely get tear-out on the inside.

 

[exoduse35]

To help keep the gel coat from chipping, tape the area and drill through it. Cut at moderate speed, with light pressure especially at first. and gently rotate the angle slightly as you cut so it is cutting only a small part of the circle at a time and channels the dust out. also make sure the pilot hole is all the way through before the saw starts to work. Good luck, Edd

 

[Dan Morehouse]

Oooooh, a Cape Horn. Wish I was getting out the hole saw for one. Good suggestions so far. If your drill has an attachable handle, use it. And try to get into a position where you are solidly braced. If your transom has much angle at all, (enough so the pilot bit can't engage before the saw edge does) it will help to cut a hole thru an angled block first and then attach the block to the transom to act as a guide for the hole saw. And no hard pressure until the saw is well engaged, if then. Having a hole saw bind and turn your wrist into a pretzel is like falling off a horse. You just have to get right back on.

 

[DanielW]

Oh how I hate drilling holes in my boat! A cape horn is on my shopping list for the "big cruise" so I'm keen to see how this one progresses.

 

[MarkA]

+1 on taping the area, moderate, not high speed, light pressure. Make sure you use a drill with a side handle.I just enlarged instrument holes in my bulkhead from 2.75" to 3.5", and experienced no chipping or binding. Since the edges are covered by new instruments, I did not bother to use tape.

 

[MarkA]

WAIT!I just saw your pics. If you intend to use that cordless drill, with no side handle, you're asking for trouble. Also, that long pilot bit is going to flex and give you even more trouble. You need the drill and shaft to be extremely stable--especially since you won't be cutting the entire circumference at once, but only be cutting the bottom arc at first.

 

[Glyn Judson]

Cutting a hole.

Sven, Mark makes a good point about the pilot drill. You can readily get 1/4" twist drills that are 6" long which might be a great help. Glyn

 

[Sven]

Worked like a charm !

Pictures and description later ... after we vacuum up the stuff before it blows into to water !

:clap::clap::clap::clap::clap::clap::clap::clap::clap::clap::clap:

 

[MarkA]

Whew!

Pictures and description later ... after we vacuum up the stuff before it blows into to water !:clap::clap::clap::clap::clap::clap::clap::clap::clap::clap::clap:

Well done!

 

[Sven]

We put the pictures on the blog http://www.grenander.com/Senta_II/Blog/Entries/2012/3/30_We_have_a_hole_in_the_boat_!_(Sven).html

But here is the hole itself



Glyn had suggested privately that we use a small drill that would stall before it tore something if it started binding. What we did was set the Dewalt on a screw driver setting that would slip if the torque got too large and that worked great ! Thanks Glyn.

We also took Yves Gélinas' advice about the long bit. Instead of using a long drill bit we used a 3' long plain steel rod once we'd drilled the pilot hole. The long rod gave us much better control over the alignment of the drill and I think it also helped prevent binding because we'd keep aligned better than we would have with a short bit. Since we were running at low speed there were no vibration problems but Mark was right that it was a concern of mine too - it just turned out not to be an issue.

We did bottom out the hole saw without realizing it ... too focused ... but we recovered from that.

All in all it worked out beautifully !!

We are much relieved



-Sven

 

[Sven]

25 minutes compressed into about 3

It is a really boring (not sure how to avoid that pun ?) video unless you are trying to bore a huge hole in your boat.

[video=youtube;q-cBhM_DJEQ]http://www.youtube.com/watch?v=q-cBhM_DJEQ[/video]



-Sven

 

[Maine Sail]

The secret is to start in reverse and cut through the gel coat before swithiing to forward....

For Small holes;

I use bradpoint bits but start in reverse and then switch to forward once through. I've drilled literally thousands of holes this way with zero chipping..

You'll want a good set though. Many bradpoint sets are meant for wood only and are soft steel. You want a good high speed steel set. Rockler has a decent set and is what I am currently using.

If you countersink the hole after drilling, to create a good seal for your sealant of choice, it also limits crazing from starting.

You can see the holes they make in this article:
Potting Deck Penetrations To Prevent Core Rot

HSS Brad Point:

Clean Holes:

Done right and started in reverse a good set will even make near perfect holes in PAPER..

Starting in reverse is also a key trick with hole saws too. You can drill clean holes even though headliner fabric & vinyl by beginning in reverse. Once through the gelcoat, which is easy, flip it to forward..

While installing a battery monitor on a customers boat I remembered to take some pics. Measuring for it took far longer than the act of drilling..

The only reason for tape was to mark my hole center, I get holes just as clean without tape:

I then drilled a 1/4" pilot hole, the same size as my hole saws arbor drill, using a brad point drill bit. The brad point prevents wandering on surfaces not good with punches.:

Started in reverse with the brad point and once through the gelcoat I switch to forward:

Then I busted out one of my Lenox hole saws and drilled through about half way in reverse before switching to forward:

Hole done, no chips and perfectly clean:

I saved the plug to show how easy this is:

The right tools and the right technique make for easy work..

 

[adam]

I wasn't the original poster, but I wanted to thank everyone for their sound advice anyways.

I just cut a 3.5" hole in my deck for the anchor line and the process went very smoothly with your help.

Cheers,
-Adam