Using a drill for lapping a mold

[Charlie Two Tracks]

I just lapped one of my molds using a screw tapped into a boolit and then turning with a screw driver. The boolit is inserted into the cavity as it was when poured. Here is what I was thinking. If you just had to increase the drive band width, why couldn't a guy chuck up a boolit nose first into a cordless drill and then put the other end into the mold and turn that way? I would not be touching the crimp groove or anything else in the mold. Just the drive band. Anybody ever done this? I may try this route if I run into another mold that I have to increase dimensions on. :coffee: sometimes I think too much.

[runfiverun]

sometimes you have to modify the boolit to lap just the areas you want as the compound has an annoying habit of migrating in the mold.
grinding the nose or the g/c area off is a pita but is better than the alternaive.
occasionally you have to make a series of laps to get what you want.

[GaryN]

I think it will do a much better job in a drill press. In a cordless drill it will wobble some and cause some inconsistencies (shoddy work).

[turtlezx]

instead of a screw into the lapping boolit. i drill a hole and insert a small dia. spring
then chuck it in the varable speed drill with compound . It gives some flexability to it
that a screw doesnt

[blikseme300]

The wobble from a hand held power source can be benificial IMHO. I have revived a number of older Fe-based molds to drop suitable boolits for lube sizing. I have a number of Lyman and H&G molds that are just perfect for creating boolits once kissed and lubed through a Star. Yes, I have modded Lee 6-bangers as well and care needs to be taken when opening them up. Don't ask how I know...

[StrawHat]

Another caution when using a screw and a power tool. If for some reason the mold grabs the lapping boolit, there is the potential for the screw to drive through the lap and damage the mold. An easy solution is to clip or grind of the point of the screw.

[Mal Paso]

I sprinkled Diamond Powder on a steel plate and rolled the lapping boolit on it so just the bands were covered. There was some migration but most of the cutting was at the bands.

+1 for cutting off the screw tip, also I used the mold centerline to mark the boolit for drilling by marking , rotate 90* and mark again.

Undersized Lyman 429421 Iron Mold.

[Bent Ramrod]

I do my mould lapping like that with a variable speed drill. I drill a hole in the end of the boolit in the drill press, run a tap in until it bottoms out and then chuck the assembly in the variable hand drill. I wipe on some Clover Compound and run the lap slowly while squeezing the mould handles together. After a few seconds, I open the cavities and remove any excess Clover, then put the lap back and run it again. Always at slow speed (maybe 60 RPM), and I stop and cast a boolit at intervals to check progress.

I have selectively done bands or noses, but this requires a collet chuck and a lathe to trim off the parts of the casting you don't want to touch the mould.

When done, I put the lap in the vise, reverse the drill and back the tap out.

[williamwaco]

I use a variable speed drill turning as slow as possible. I clamp the mold around the bullet in a drill press vice before spinning the bullet.

I turn it only about five or six revolutions at a time.

I have never damages a mold.
.

[leftiye]

Drill a hole in the boolit, and make a three sided (triangular section) portion on one end of a short rod that is marginally bigger on the points than the hole made in the boolit. Drive the triangular end into the boolit - this doesn't displace much lead and keeps boolit distortion to a minimum. So long as it has parallel tips on the triangular section it is superior in keeping the boolit/shaft assembly more coaxial than screws have done for me (less wobble). Put the round part of the shaft in a drill chuck, and hone away.

[mdi]

I've always used self drilling sheet metal screws, hex head for lapping. The screw will drill just so far and the screw will jam in the lead and hold tight. Works every time and no worries about going through bullet and damaging mold, or the extra step of drilling the bullet ...

[mdi]

Drill a hole in the boolit, and make a three sided (triangular section) portion on one end of a short rod that is marginally bigger on the points than the hole made in the boolit. Drive the triangular end into the boolit - this doesn't displace much lead and keeps boolit distortion to a minimum. So long as it has parallel tips on the triangular section it is superior in keeping the boolit/shaft assembly more coaxial than screws have done for me (less wobble). Put the round part of the shaft in a drill chuck, and hone away.
An "easy-out", or broken screw remover...

[leftiye]

With a reversable drill, whus da differunce?

I've drilled holes and put screws in them, mostly they don't go straight, as lead is so soft (or sumpthin'). Tapping the hole as mentioned earlier is probly the best, but the triangular rod will keep thangs straight too. Rod is re-usable, you only need make one. Grind the flats on your grinder or file them.

[DLCTEX]

I think this http://castboolits.gunloads.com/showthread.php?17545-Sticky-Lapping-301-Changing-LEE-feature-diameters is as good as you can explain it.