Advice Needed, Drilling A Hole On The Edge Of A Piece.

T Bredehoft

T Bredehoft

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This is a .038 dia drill, trying to drill a hole .100 from the center of a .250 piece of 6061 aluminum.. If you do the math, I have .005 between the outside of the drill/hole and the edge of the piece.
As soon as the drill touches the work, it walks to the outside. See the first piece for an example.
Do I need to spot the hole with a #0 ctr drill? I may have been trying too many shortcuts.
 
A screw machine, i.e. a shorter drill bit might make it easier. If there is a slope to the part, then a spot face with a tiny end mill might be necessary to keep the bit from deflecting.
 
I'll try spotting it with a center drill, then drilling the hole, shortening up on the drill. I only need .300 of drill bit.
 
OK, spotting just barely worked. I couldn't get the full diameter of the tip of the spot drill (#0 center drill) else the chamfer would hit the hub. Peck drilling that .038 drill through .175 of aluminum isn't fun, either. Oh Well, 2 holes per piece, times 80 pieces....that's going to take some time. Its sure a good think I like working.

Thanks, GS for responding.
 
Try spotting the hole with a spotting drill rather than a center drill.
Spotting drills do a better job of centering a drill bit.
 
I currently have kind of the same problem. The difference is that I'm drilling a 9.8mm (0.386 in) , 3.750 deep in UHMW and drill actually breaks through the edge by 0.004. Even with a good pilot hole and really sharp drills, it still walks to the outside edge 0.050 over the length. I'm working on a solution.

This is really an order of operation issue, I should not have turned the OD to size before I drilled the holes. OOPS!:confused 3:
 
Plunge with an endmill. Do it in 2 passes, first slightly undersize , then to size to eliminate walk.
 
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