Dumb question

[GWB]

Need to drill through the cabin top to mount t-track for my staysail. The cabin has ash tongue and groove on the ceiling and plywood between that and the top which is glass.
I'm afraid that when I start drilling from the outside the holes will blow out on the inside. Is there anything I can do to prevent this?
Thanks for any help

[floatingkiwi]

It's me mate from Oregon.
You could take a small length of pipe, with a bigger I.D than the bit, and place it over the bit when drilling so that it stopped against the chuck disallowing any more depth than necessary.
There are vaious drill depth guides available but I like to make my own.

[GWB]

Cheers Kiwi - but I do need to go all the way through.

[TerryLL]

Drill a tiny pilot hole, say 1/16-inch, to locate the exit hole on the inside. Then drill the finish hole while your helper holds a hardwood block against the exit hole to prevent tear-out. If you have no helper, then drill half way in from both sides so the holes meet in the middle.

Those fine-point taper drills leave a clean exit hole and I often use them for drilling blind through-holes. Brad-points leave a clean entrance hole but can blow out the exit side if not backed up.

[Lew Barrett]

Tery pretty much has the "drill." If you have someone back up the exit point with a hunk of 2X4 (or whatever seems appropriate) you should do fine. And take your time letting a nice sharp drill do the work.

[2MeterTroll]

drill it from both sides.

[floatingkiwi]

Cheers Kiwi - but I do need to go all the way through.
Oh, right, Duh. I was thinkin it was a bit easy.That pilot hole of Terrys is a good thing eh?Even it that tears a bit it guarantees marksmanship and gets oversized anyway from the inside.

[GWB]

Thanks all