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RE: Difference #30 drill bit v. 1/8" bit? 100deg countersink supplier?



> From: CBrock5000@aol.com [mailto:CBrock5000@aol.com]
> Subject: Difference #30 drill bit v. 1/8" bit? 100deg countersink
> supplier?
>
> The plans call for a #30 drill bit in many places for a 1/8" pop
> rivet, but
> what is the difference? Also, do you know where I can find a 100 degree
> countersink? Aircraft Spruce shows one for $46!! and what attachments are
> needed to complete this tool, thanks in advance, chris brock.

1/8" rivet clearance requires a #30 bit (0.1285"). You could drill with the
1/8 bit, and wiggle it around some, but you probably wouldn't have a round
hole when you were done. You will also need other numbered bits for the
various holes you will have to tap. Don't know where you are in the country,
but there always seems to be one old-time hardware store in every area that
carries numbered drills and many of the other oddball things you'll need
along the way. The back page of Freeman Aviation's catalog has a great
conversion table for drill sizes, millimeters, and decimal inches. (Freeman
always has a tent at OSH and Sun 'n Fun, and his number is 770/227-2602.)

Here's a quick table for most of the bits you'll need:

Nmnl		Bolt		Rivet		Bolt		Fine		Coarse	Pipe
Size		Size		Clrnc		Clrnc		Tap		Tap		Tap
1/16				#51
3/32				#40
1/8				#30								11/32
		#6								#36
5/32				#21
		#8				#19
3/16		#10		#11				#21
1/4		AN4		F				#3				7/16
5/16		AN5						I,17/64	F
3/8		AN6						Q
7/16		AN7						25/64
1/2		AN8

As far as the 100 degree countersinks, I buy mine from J&L Industrial Supply
for under $10. They have retail stores in many areas, and they ship
nationwide. Phone is 800/521-9520. Their really, really thick catalog is
free, and they have more tools than you can imagine. One of the neat things
they carry is bottoming taps, which let you clear out the epoxy from any
holes you pre-tapped in your seat and seat belt hard points without fear of
penetrating the skin.

 - Chuck