Trick to lapping blocks???

[GRUMPA]

I've read up on some of the threads here on some of the folks lapping blocks. But either I'm not understanding something or I haven't had my normal 2 pots of coffee. My own (%%$ blocks need to be opened up at least .001 and from what I've read I think they just cast as normal use a lapping compound and spin the bullet for a few minutes and they're done.


What details I think I'm missing are, 1 since lead being as soft as it is is it worth the while to heat treat the bullet? 2 What kind\type of lapping compound is good to use? Been looking around the house an all I have is diamond lapping compound, is this good enough or not good enough? 3 is it better to spin the bullet by hand or set it up in something like a drill press on slow speed?


I really don't want to find out the hard way I'm doing something wrong. Most of my blocks are lyman molds and those are the ones that need the most fine tuning. [smilie=b:

[chboats]

GRUMPA - I used lapping compounds that I got from the auto parts store I believe they are Clover brand. Started with 220 grit. Found the best way for me was to cast a normal boolits, you will need several. Drill a hole in the base and tape a torx bit into the hole. I use a hex bit handle to turn it with to start and then an electric screw driver. It is very important to keep the block faces clean so that the mold closes completely. I even go so far as to clamp the block in a C clamp. If you don't, more will be taken out near the mold line and less in the bottom. To start with don't put a lot of torque on the bit or it will strip out the hole

Carl

[dragonrider]

Grap a regular hex nut, 5/16 works well on mold of 30 can and smaller, bigger than that use a bigger nut. center the nut as best you can over the cavitie, no sprue plate. Pour some lead in it making a good puddle on top of the nut. let cool. Roll some lapping compound on it, put into the cavity and using a wrench of proper size rotate the boolit while squeezing the handles lightly. rotate until the boolit turns freely and then clean and cast and check size. Repeat as needed.

[GRUMPA]

Carl you stated that you started out with 220 grit. When all is said and done did you end up with a different grit when finished?

[HORNET]

I usually use a 320 grit or Fine Clover (I've got both, don't see much difference). It gives a reasonably good finish and seems to cut fairly well. I didn't like the way the 220 grit cut. Use VERY SMALL amounts of lapping compound, it'll spread out much more than you'd think. You might want to review the discussions on Lee-menting in the stickies at the top of the forum for this topic. Clean between the blocks frequently, check and change the lapping boolit as needed. I usually find that I can open things up about 0.001"using up 2-3 boolits and then have to cast more 'cause they won't cut anymore. Need to recheck the size about then anyways. YMMV. Good luck, the first time is the hardest...

[stainless1911]

Can you lap brass molds? Can you lap a Lee push through sizer die?

[Ben]

GRUMPA

Take a look at this...............


http://castboolits.gunloads.com/showthread.php?t=47669

[RobS]

Can you lap brass molds? Can you lap a Lee push through sizer die?

Yep to both

[sgabel1]

I had a Lyman 358242 mould that was small and out of round by .0015" and cast small overall at 0.3575. I used the technique in the attached article. After about 8 bullets cast at 4 different intervals the mould casts 0.3595 and is out of round by .0005 so the bullet measures between 0.3595-0.3600. Not too bad. I would have preferred a good mold from Lyman to start with. This one was old new stock. The secret is to cast two bullets lap. Cast two more bullets lap. Once you use the compound plus the diameter of the bullet there is no meat left for cutting. Cast new bullet frequently and things will work more quickly.Note this was on a steel mold.

http://www.lasc.us/Brennan_4-0_ModifyCastBullets.htm

[chboats]

GRUMPA - I like 220 grit to start for faster cutting and finish with 320. I don't know if 220 really cuts any faster but it make me feel like I'm doing more.

Carl

[cajun shooter]

The Lee sizing die is only using a very narrow strip of metal for sizing. If you look inside the die it is not the same as other sizing dies. Star dies are the same internal diameter for the length of die or very close to it. That is how Lee cuts cost and as far as I am concerned they are not meant for sizing good bullets as to being concentric.

[nanuk]

I just had a thought

(scarry)

do you just rub the compound on indiscriminately? or do you roll boolit b'tween two steel plates so as to just embed in the lands.

that way you do not make your GG less deep, but only enlarge max diameter.

[GRUMPA]

OK I 'll give a little update here. Called all over the place looking for valve grinding compound at the auto stores and all they had was 150 grit. So for me just to get that would be a 62 mi. round trip (I'm rural). So I thought about it a bit and realized I have a sand blasting cabinet in storage and scooped out some very fine media from it. It more than likely would be equal to 300-400 media. Now all I need is some sort of a paste to kinda hold it together, went to the house and got some toothpaste, mixed it up and not only does it smell good it rinses right off.

I have a 2 cavity mold and cast out 6 for each cavity thinking that should be enough. The first one I did I just put some on the boolit put it in the mold and noticed it will not close all the way on account of now its way bigger from the paste and grit combo. So I filed a small flat on the boolit and put that media right on the flat and when I put it in the mold it closes right up. Now I got out the variable speed drill out and spun it just for 10 seconds on high to sling the media away from the boolit and slowed it way down after that. You would be amazed at how you can feel the resistance at first then disappear really fast.

This kinda stuff took me a better part of a day between cooling the mold and casting to find out how much I took out. I went through 6 each per cavity and opened it up only .0005 and am really impressed with the amount of out of roundness it took out. But this really takes time to do right, its really important to squeeze an those handles when your doing this, and cleanliness between the mold halves is important. And my mold is metal and NOT aluminum so I kinda figured this was going to take me some time. OH before I forget THX Carl for replying with that little note.