Sorry to repeat this but the number I quoted for the Cleveland
uni-flute was not their part number but a catalog number for
Rutland Tool Supply. Also, there's a second style of countersink that's
equally smooth . . .
>> I followed the procedure you outlined in option 2. I used a piece of
>> .125 scrap with a #30 pilot hole, and clamped it to the spar flange to
>> guide the countersink. I still had some chatter, most likely due to the
>> hole wallowing out somewhat after numerous iterations. It all came out
>> fine, however.
>When I use my airdrill to countersink I will occassionally experience
>chatter.
What kind of countersinks are you using? At RAC and in my
own toolbox, I've pitched all the hardware store countersinks
(designed originally for wood) that have a multitude of cutting
edges. The aviation industry uses single flute cutters for
most hand-held applications. Check with your local tool suppliers
for Cleveland Twist Drill uni-flute countersinks. I've used these in
my shop for years . . they're very smooth in thin sheet metal.
Anoher nice choice is Weldon high speed steel pilotless countersinks
which have the usual conical shape but replace the radial cutting
edge with a hole drilled normal to the face of the cone. The 100
degree part number is CSA-8. Either style is under $10 from most
tool suppliers.
Bob . . .
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