08-25-2017, 05:37 PM
Occasionally a set of transfer punches would be very handy for spotting a hole pattern from an existing part to a matching or similar part. In my situation it was locating, drilling and tapping four holes in a lathe backplate to mount a new 4-jaw chuck.
Not owning a set of transfer punches, I came up with this expedient for transferring the chuck mounting hole pattern to the backplate. (This concept was probably devised by about 3-1/2 trillion others before me, LOL.) The method is useful only when the hole pattern to be transferred consists of through holes - not blind ones.
Turn down a center punch to a convenient diameter, smaller than the hole that you will use as a pilot. Or as I did, point a cheap Chinese drift after you make sure that it is fairly hard. The drift diameter must be smaller than the pilot hole:
Turn and drill a bushing that is a snug fit with the punch and a fairly snug fit with the pilot hole. In this photo, the tailstock chuck and center drill are moved near the bushing to catch it on the center drill as it is parted, preventing losing it in the chip pan mess. Note that if desired, you could turn a "lip" on the bushing to aid in extracting from the pilot if it stuck for some reason (loose chip, etc).
The bushing slipped over the punch can now be used as a crude, but effective, transfer punch.
Finished.
A spot of glue from a hot glue gun (or other temporary adhesive) can be used to tack the bushing to the punch if the bushing tends to stick in the pilot hole. Or use the following tool, made from a "G" guitar string (or whatever size music wire is on hand, LOL). This will pull the bushing right out:
Not owning a set of transfer punches, I came up with this expedient for transferring the chuck mounting hole pattern to the backplate. (This concept was probably devised by about 3-1/2 trillion others before me, LOL.) The method is useful only when the hole pattern to be transferred consists of through holes - not blind ones.
Turn down a center punch to a convenient diameter, smaller than the hole that you will use as a pilot. Or as I did, point a cheap Chinese drift after you make sure that it is fairly hard. The drift diameter must be smaller than the pilot hole:
Turn and drill a bushing that is a snug fit with the punch and a fairly snug fit with the pilot hole. In this photo, the tailstock chuck and center drill are moved near the bushing to catch it on the center drill as it is parted, preventing losing it in the chip pan mess. Note that if desired, you could turn a "lip" on the bushing to aid in extracting from the pilot if it stuck for some reason (loose chip, etc).
The bushing slipped over the punch can now be used as a crude, but effective, transfer punch.
Finished.
A spot of glue from a hot glue gun (or other temporary adhesive) can be used to tack the bushing to the punch if the bushing tends to stick in the pilot hole. Or use the following tool, made from a "G" guitar string (or whatever size music wire is on hand, LOL). This will pull the bushing right out: