Drilling Technique- Enlarging an existing hole
- Thread starter LG63
- Start date
no, not by hand he's using a power tool
doesn't mean it won't work does it?.....i was drilling 29mm holes.....totally chatter free
the fabric damps the chatter out....
ever see what a 4 1/2" self feed bit can do in a Hole Hawg?
i'm new to the Forum......but i'm an old tool freak
Alchymist
Well-known member
when enlarging a drilled hole.....with a drill press, mill or BUX drill
fold ~6-8 layers of cloth into a square larger than the existing hole
center the drill with it off.....now place the square over the hole and and turn the drill on and drill away
the fabric stops any chattering too
1st time i saw it done was 40+ years ago in Swtizerland
PS; don't chamfer it
Have found method this to work well every time.
A Cole Drill is great tool to have for jobs that cannot be performed in a drill press, it can be used in a good many situations with a bit of ingenuity.
bad_idea
Well-known member
What is a Cole Drill? Is that a typo for Core Drill? If so, what is a Core Drill? I thought it was a fancy hole saw for concrete. Not trying to be sarcastic, honestly ignorant on the subject.
Provincial
Well-known member
Back when I worked on Caterpillar 3400-series engines a lot I made a drill jig for the exhaust studs with interchangeable bushings. I made the bushings out of Grade 8 bolts, which worked for me but would not hold up well if used often. I made three sizes of bushing, one was 3/8" for locating the tool if any of the stud was left above the surface, a pilot size for drilling out the stud but leaving the threads undamaged, and a pilot size for the Helicoil. The fixture was a piece of round bar about an inch long welded to a slotted 1/2"x 1" strap long enough reach a nearby stud. I bored and faced the round bar in a lathe to keep the bore square with the working surface.
I would have made the tool long enough to catch two studs but then it wouldn't have worked in some places because the slotted tail would interfere with surrounding obstacles. It worked very well and made it much easier to control the feed of the drill since it kept the bit square with the hole. I learned to use a toe clamp from a mill to provide a second clamping point on the "tail" that helped keep it in alignment.
I also learned to be very careful about keeping the drill in alignment with the hole. If I got any side force at all it started eating up my bushings. That problem would be fixed by buying real drill bushings from an industrial supply.
I never had to do it, but you could align the fixture over a hole with damaged threads by using the tap drill bushing and putting the shank of a tap drill through the fixture/bushing into the threaded hole while you clamped it down.
I would have made the tool long enough to catch two studs but then it wouldn't have worked in some places because the slotted tail would interfere with surrounding obstacles. It worked very well and made it much easier to control the feed of the drill since it kept the bit square with the hole. I learned to use a toe clamp from a mill to provide a second clamping point on the "tail" that helped keep it in alignment.
I also learned to be very careful about keeping the drill in alignment with the hole. If I got any side force at all it started eating up my bushings. That problem would be fixed by buying real drill bushings from an industrial supply.
I never had to do it, but you could align the fixture over a hole with damaged threads by using the tap drill bushing and putting the shank of a tap drill through the fixture/bushing into the threaded hole while you clamped it down.