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lane
01-14-2009, 09:10 PM
A 3/8 are a1/2 inch 90º spot drill makes a nice cutter for cutting a 45º chamfer on a part in the mill. Brake the edge are such.

Dawai
01-14-2009, 09:30 PM
I like a uni-bit in a lathe for starting a rough center.. it is short, don't deflect off center.. cuts without bending or wobble.. I've used it as a spotting drill too when I could not find the other.

Sometimes, close is good enough to perfect. Perfect, ain't nothing on a harley built in a tin barn perfect...

oldtiffie
01-14-2009, 10:31 PM
I use a worn out centre drill - reground to suit - worked fine. I used climb milling to finish off and to clear the cuttings away. A fairly light cut is not enough to "drag" the table. An old end mill works just as well.

Fasttrack
01-14-2009, 10:52 PM
Thanks Lane! I've got a few hangin' around somewhere. I'll have to remember that.

loose nut
01-17-2009, 11:01 PM
I got all excited about this post but was disappointed when I saw it, when I checked the title I realized it said "Tips". Oh well.

Mark Hockett
01-18-2009, 02:40 AM
To add to Lanes post, you can use the 90 degree spot drill to locate a hole position and create a chamfer at the top of the hole in the same operation. The formula for calculating the chamfer is very simple, take the desired width of the chamfer multiplied by 2, add that number to the hole diameter and then multiply that number by .5 that will give you the depth to spot drill. An example would be, you want a 1/2" hole with a .015" chamfer at the top, the depth to drill would be .265". When you drill the 1/2" hole there will be a .015" chamfer at the top, no need for a second operation or hand work.
.015 X 2 = .03, .03 + .5 = .53, .53 x .5 = .265