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Bill Cannon

Member
I am dumbfounded by this. I am countersinking my spars on the HS (10). I am not going too deep but the bit seems to be cutting the hole larger. The countersink is fine but the hole is coming out oblong on too many. I am using the right bit and the depth is good. I am holding it as steady as I can. Could the tip of the bit be damaged (doesn't look bad and can't think of how it could be damaged)?

Any ideas?

Thanks,

Bill
 
If the material isn't very thick, then you'll stretch the aluminum as the bottom edge of the hole becomes thinner. Use another piece of aluminum with a hole in it cleco'd to your part to back up the hole. Or, what I do is align the hole in the part with a #40 hole in my table and then countersink. The hole in the table helps keep the bit from wandering.

PJ Seipel
RV-10 #40032
 
Thanks. I will try that and let you know. I will use a scrap piece of aluminum since it has to rest on the inside of the flange.

Bill
 
Made a backer with an aileron spar from a training project. It's about 18" long so I can do a bunch of holes before moving it. Works great. Thanks again for a quick and very helpful response. I will do all my spars like this going forward.

Bill
 
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