Mould base-band enlarging?

[.22-10-45]

Who would you recommend for enlarging base-band dia. .004"? Thanks!

[country gent]

.004 out of an existing mould is going to be a job, not in the removal but in the set up ( everything will need to be perfectly lined up) Then the touch off of the cutting tool will be critical. WHile your saying .004 out of the mould that's .002 on a side.

You could lapp it out with out to much trouble. Lapping would just the base band would require only impregnating the base band with compound and leaving rest bare.

A couple flat plates 1 1/2 wide 3-4" long and 1/4"-1/2" thick Put a shallow rail down the long edge of one 1/8" above surface. This is the rail to align the bullet on location.
Cast a couple 3 good bullets from each cavity
Drill a hole centered on base a piece of 1/8"X 2" key stock just fits into, and glue a piece into each bullet. Epoxy works very good but I have used super glue also.
put a very light smear of compound along rail as wide as band. lightly finger roll 1st bullet thru this and move over and roll between 2 plates to literally press the grit into the bullet making your lapp.
start with a grit around 280 to rough with. remember you only need to remove .002 on a side.
Gently insert lapp into one half of the blocks and close tightly. I clamp them in a small drill press vise.
A T handle tap handle and work bullet/lapp in a tapping motion back and forth 3-5 times 3/8-1/2turn rotate 1/4 turn and repeat this thru 2 rotations. check progress here at this point. Open and remove lapp, clean blocks. Visually inspect the cut if bright shiny area is close to 100% measure it or better warm it up and cast a few bullets measuring them.
Here its a judgement call to work closer with the coarse grit or go finer depending on measurements sizes.
Next grit would be some thing 320-400 to just barely under size or to size Again casting a few bullets and measuring is preferred
My last run once very close to size or to size is 1 full rotation cycle with flitz or shimichrome polish. Tooth paste will also give this fine polish. Here you can either do the compete cavity or just the band.

Some tips to help the lapping process go smother.
A small drop of light oil on the lap helps the compound to cut cleanly and evenly. Here a light drop on a q tip and wiped into the cavity before inserting lap.
the back and forth rotation maintains cavities location and makes a very round cavity.
Having a small lead pot up to temp at the bench speeds checking sizes up. Clean and dry mould sit on top of pot to warm for 4-5 mins dip corner till lead dosnt stick and cast a few 8-10 good bullets cool and measure. I prefer to ladle cast for this but that's me.
Lapping is done with the softer material cutting the harder material. The soft lap impregnates with the abrasive and becomes a cutting tool the soft material then cuts the harder material with the abrasive since its holding it.

[beagle]

Any good machinist with a CNC mill can do that in about 10 minutes. Square mould, dial in outer edges and make .001" cuts until you get what you want. Basically the way we remove GC shanks./beagle

[longbow]

It could be even easier depending on caliber. You can likely buy a reamer to suit if you look at standard sizes, metric, decimal and letter sizes. A little larger won't hurt anything (like a thou or two). all you need is a drill press to line things up then turn reamer by hand. Chucking reamers should be pretty inexpensive... like $15 to $20.

[oldhenry]

The information by county gent is excellent.

Henry

[ulav8r]

The information by County Agent is excellent.

Henry

Spell his name right so he gets proper credit, I'm sure country gent would appreciate it.

[toallmy]

I spoke through PM with a member Willicd76 about a bit of work on a few molds I want to play with , and his price seamed very reasonable . I haven't done it yet so I can't really say how it worked out but this thread reminds me to get them in the mail . Send him a private message and ask .

[oldhenry]

ulav8r,

Done. Thanks for the heads-up.
Henry

[john.k]

I cut the gas check groove from all my iron moulds............simply set up with a dial gauge,and skim.The first one was a Lyman 427215,and I overdid it ,ended up about 434,after that I got the hang of the light touch needed,and did a dozen two cavities in a couple of hours..............A friend had done Lee 2 cavities by cutting the handles ,rather than punching out the pins....he also turns the 458HB into a smooth PP 462 or a single groove 472 FB.

[longbow]

I should add that the reamer idea assumes a PB mould. Otherwise you are into precision machining or lapping the mould per country gent's post.

Looks like you may have it under control at this point.