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Fractional for a #10 drill bit

mvidalr

mvidalr

Well Known Member
Hello my fellow builders,

Which would be the fractional equivalence to a #10 drill bit used to enlarge the prepunched holes for the stall warner vane in a RV-8? Same applies to the -7 & -9 for what I understand.

I don't have this drill bit, and just like the famous #40 is a 3/32", and the #30 is a 1/8", i was wondering which would be the #10 required in the manual.

I know that according to the Aviation Standard book is (in decimal) .1935 but this does no good from the vast array of fractional drill bits that I have.

Thanks for the input!
 
My advice: buy a complete set of numbered and lettered bits. You will use them in various places of the build (holes for tapping, holes in UHMW plastic, slightly smaller ones for drilling out rivets, etc.).
I found a complete drill bit index set at Costco a few years ago. A quick google search shows you can buy one for about $60.
If you really just want single bits, you can find these at most industrial supply shops. I've had to replace a few bits that met an ugly demise. :)
 
I second the move to buy a number drill set. No number drills exactly match fractions- and that is for a reason. If you use fractions for rivets the rivets will fit tight in the holes or not at all. Trying to put a 3/32 rivet in a 3/32 hole= 0 clearance, whereas a #40 will get you about .004 clearance. Same applies to 1/8 and so on. If you use the proper number drill the rivets fit properly. Same goes for screws and bolts. The metal world works in decimal- i.e. number and letter drills.
 
Individual sizes needed

If you buy individual number drill sizes, the contents list of the Plane Tools full RV tool kit gives a good list of the sizes you need -

#40 Aviation Cobalt Drill Bits for 3/32" rivets, 8 each
#30 Aviation Cobalt Drill Bits for 1/8" rivets, 6 each
#27 Aviation Cobalt Drill Bit
#21 Aviation Cobalt Drill Bit
#19 Aviation Cobalt Drill Bit
#12 Aviation Cobalt Drill Bit
1/4" Aviation Cobalt Drill Bit
12" Aviation Extra Long #40 Drill Bit
12" Aviation Extra Long #30 Drill Bit

Note that a #12 drill is called up for use in making an AN3 bolt hole. It will give a better fit than a #10 drill you originally asked about.

However, buying a full number drill set is still a good idea.
 
mvidalr said:
and just like the famous #40 is a 3/32", and the #30 is a 1/8", i was wondering which would be the #10 required in the manual.
Click to expand...


Don't be mistaken, a #40 is not a 3/32, nor is a #30 a 1/8 bit. When it comes to drilling for a rivet. The difference is larger than you think. The numbered bits you should be using are cheap. Think about what you're building and please don't cut corners.
 
Menards

I found that my local Menards, here in Illinois, has numbered bits from 1 to 60. Nice when you find that you need a special size and need it now. Not sure if all Menards carry them!

Michael
 
Jasonm said:
Don't be mistaken, a #40 is not a 3/32, nor is a #30 a 1/8 bit. When it comes to drilling for a rivet. The difference is larger than you think. The numbered bits you should be using are cheap. Think about what you're building and please don't cut corners.
Click to expand...

Thanks for the advice. I think I didn't choose my words correctly when I mentioned the relationship of a #40 with a 3/32" rivet or a #30 with a 1/8" rivet and so on. All I was asking for, was the relationship between a #10 drill bit and the fractional counterpart, if any.

I won't discuss whether or not my tools are cheap or aviation approved, which is simply an understated assumption, to say the least.
Rest assure the airplane is being built with certified tools and hardware. I would never compromise the construction of a flying machine in which I'd fly my family with.
This was just a little lack of information. Thanks again
 
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On a side note to this ... I have always wondered who came up with the numbering system ... # 30 or #40 .. based on what ?? Inches and ft I get and decimal of an inch .... but numbers and letters ... who came up with that idea ! ;-)
 
JanRV6UK said:
On a side note to this ... I have always wondered who came up with the numbering system ... # 30 or #40 .. based on what ?? Inches and ft I get and decimal of an inch .... but numbers and letters ... who came up with that idea ! ;-)
Click to expand...

Probably from here -

Stub's Steel Wire gauge
Used for drill rod and tool steel wire. It is the basis of, though not identical to, the numbered sizes of American Standard twist drills.

You can blame the UK in 1884...:)

http://en.wikipedia.org/wiki/Stubs_Iron_Wire_Gauge
 
Numbering System - wire guage

As I understand it, (and I have been spectacularly wrong in the past!) the number refers to the number of times wire stock was pulled through the forming dies. Hence - the confusing relationship between the number and the physical size of the wire. I.e. - more times through the die, smaller diameter. YMMV!
 
Gil,

For sure the Norwegians had noting to do with it !! :) .. I am not going to ask why a US Gal is smaller than a Imp Gal !!
 
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