Rick6a
Well Known Member
Tip: How to move a hole
Now you've done it. After carefully laying out and piloting all those holes, you discover the one on the very end has short e.d. Since the hole is supposed to be brought up to .1875 and filled with an AN3 bolt, you know the minimum e.d. should be no less than .38 (2 X dia.) yet the pilot hole measures only .33 to the edge of the part. What to do, what to do? Fear not. This happens all the time in a production environment and the fix is routine stuff. You simply pull the hole over! By using a drill block or bushing block fitted with an appropriately sized bushing, you clamp the setup onto the work so that it just barely picks up the outermost edge of the subject hole. It is important to clamp the tooling very securely so that it cannot move. Using a drill bit but NOT a piloted drill bit,...I like using a "gun drill" for this kind of work...make the pass. Drill blocks and bushing blocks are made in all shapes and sizes. Like cleco buttons, you can never have too many.
You can even make your own bushing block out of a thick piece of stock sized and shaped to fit a particular situation. Use a drill press to drill a hole through it to accept bushings such as commonly available hardened steel drill bushings with 1/2" O.D. Alas, matched hole quickbuilders among us have no idea how much fun they are missing out on.
This is very, very basic information but the fundamentals are the same regardless of the sheet metal situation.
Now you've done it. After carefully laying out and piloting all those holes, you discover the one on the very end has short e.d. Since the hole is supposed to be brought up to .1875 and filled with an AN3 bolt, you know the minimum e.d. should be no less than .38 (2 X dia.) yet the pilot hole measures only .33 to the edge of the part. What to do, what to do? Fear not. This happens all the time in a production environment and the fix is routine stuff. You simply pull the hole over! By using a drill block or bushing block fitted with an appropriately sized bushing, you clamp the setup onto the work so that it just barely picks up the outermost edge of the subject hole. It is important to clamp the tooling very securely so that it cannot move. Using a drill bit but NOT a piloted drill bit,...I like using a "gun drill" for this kind of work...make the pass. Drill blocks and bushing blocks are made in all shapes and sizes. Like cleco buttons, you can never have too many.
You can even make your own bushing block out of a thick piece of stock sized and shaped to fit a particular situation. Use a drill press to drill a hole through it to accept bushings such as commonly available hardened steel drill bushings with 1/2" O.D. Alas, matched hole quickbuilders among us have no idea how much fun they are missing out on.
This is very, very basic information but the fundamentals are the same regardless of the sheet metal situation.
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