Tip: How to pull a hole

[Rick6a]

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.

[alpinelakespilot2000]

Good tip, Rick. I've moved holes slightly before just by angling the larger bit to move the hole the right direction, but your way would allow it to move so much more, and more precisely. Where do you get a set of drill block and bushings like that?

[Rick6a]

Originally Posted by alpinelakespilot2000

.........Where do you get a set of drill block and bushings like that?

Steve,

No one particular place. I've gotten some from the Flymart, eBay, Brown Tool, a machinist friend, flea markets, etc. Once you know what to look for, they just seem to be out there. Here are a few links to new stuff if you are so inclined. At the Brown Tool link, check out the BAT-DBK14, the BAT-70 and the BAT-54SBK "Snatch Block." With this stuff, widely used in the aviation industry, you can do a lot of repair work precisely and professionally.

http://tinyurl.com/ygrd7x

http://www.allamericanproducts.com/bush/bush.htm

[az_gila]

One other way....

Use a round needle file and "push" the hole in the direction you want it to go, making an elongated hole - but take care not to exceed your final diameter.

Use a regular drill, slightly undersize from the final size, to drill this elongated hole round.

Use a reamer to make a nice, clean hole the final size. This will clean up any chatter, tool marks form the previous step.

OR...

Try and drill all large holes #40 or #30 initially so you get them centered correctly...

gil in Tucson

[PCHunt]

Your tinyurl link below didn't work for me

Originally Posted by Rick6a

Steve,

No one particular place. I've gotten some from the Flymart, eBay, Brown Tool, a machinist friend, flea markets, etc. Once you know what to look for, they just seem to be out there. Here are a few links to new stuff if you are so inclined. At the Brown Tool link, check out the BAT-DBK14, the BAT-70 and the BAT-54SBK "Snatch Block." With this stuff, widely used in the aviation industry, you can do a lot of repair work precisely and professionally.

http://tinyurl.com/ygrd7x

http://www.allamericanproducts.com/bush/bush.htm

[pgroell]

The tinyurl link is for the http://www.browntool.com/ website.
Just search the website for the references given by Rick.