sbalmos

sbalmos

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Yesterday I was having one of those brain-blanking moments that you're not supposed to have at my age. :)

I was drilling the #8 screw holes for the fuel tank access hatch into the ribs. I did it first with a #30 bit, as I know that's the right size for the pilot hole. What's the right size for the final hole? #19?

As a side note, for final-drilling the tank-to-spar skin screw holes, where the manual says use #19, I got slightly impatient and just bought a 5/32" bit from Lowes Aircraft. According to my conversion charts, it's around a #22 bit. I also got a 11/64" bit, but that's between a #18 & #17. I'd rather be the hole be smaller than larger. Is/was this okay to use the 5/32" bit, and if the final hole size for a #8 is a #19 bit, I'm guessing using this bit would be fine?

Thanks. The brain just wasn't working yesterday.
 
I've never forgotten some early drilling mistakes and now use my drill gauge obsessively. Got mine at Avery years ago and it lives in the middle of my workbench. Great for checking the drill size for screws and bolts quickly.

1515gauge.jpg


http://www.averytools.com/prodinfo.asp?number=1515
 
Yeah, I searched here, and some of the links from years back were broken. And then there are the charts that are off just enough to bring up the possibility of sloppy holes, as Gil mentions.

Looks like I'll send an order over Mike & DJ's way. I'll drill with my 5/32" bit from Lowes for now this week, and go back over everything with the #19 when they get here.

Thanks! I'd rather endure an eyeroll emoticon than a screwy screw hole (hah).
 
sbalmos said:
Yeah, I searched here, and some of the links from years back were broken. And then there are the charts that are off just enough to bring up the possibility of sloppy holes, as Gil mentions.

Looks like I'll send an order over Mike & DJ's way. I'll drill with my 5/32" bit from Lowes for now this week, and go back over everything with the #19 when they get here.

Thanks! I'd rather endure an eyeroll emoticon than a screwy screw hole (hah).
Click to expand...

This old posting of mine is still intact and accurate.

http://www.vansairforce.com/community/showthread.php?t=26759&highlight=drill+sizes

It talks about reaming holes to size, but reamers and drill bits use the same sizing numbers.

In general we usually use #8, AN3 (#10), AN4 srews bolts on our RVs.

The larger bolts tend to be special cases.
 
Memory aid

As a memory aid and segregation trick, I made a drill guide out of a piece of wood. Screwed it to the wall and used it for the whole build.
It held the relevant size drills (both jobbers with drill stops and threaded bits) labelled with drill size and noted for screw size.

It also had enough holes that it held a "sharp" bit and another one that had been through steel or fiberglass.

Picture on this page, near the bottom
 
Last edited:
larrynew said:
I've never forgotten some early drilling mistakes and now use my drill gauge obsessively. Got mine at Avery years ago and it lives in the middle of my workbench. Great for checking the drill size for screws and bolts quickly.

1515gauge.jpg


http://www.averytools.com/prodinfo.asp?number=1515
Click to expand...

I have a gauge like this that I use obsessively. Even when I'm certain I have the bit I want, I'll check it in the appropriate hole just to make sure I don't do anything stupid.
 
N546RV said:
I have a gauge like this that I use obsessively. Even when I'm certain I have the bit I want, I'll check it in the appropriate hole just to make sure I don't do anything stupid.
Click to expand...

I used my drill gauges *constantly*.

Get that, plus the same thing for fractional sizes, plus a drill index set 1-60:

hu60.jpg


plus a bunch of spare #30s and #40s.
 
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