What is the procedure for beagling a mold? The mold I have was supposedly made to be at dimension casting linotype. At one area, it casts small. I would like to hone a little at this area to open it up some.
Printable View
What is the procedure for beagling a mold? The mold I have was supposedly made to be at dimension casting linotype. At one area, it casts small. I would like to hone a little at this area to open it up some.
Beagling a mold is using small strips of high temp. flue tape on the inside of a mold to make the two halves stay slightly more apart when closed. This will cause the boolits to cast 2 or 3 thousands bigger. You can also make it cast larger at the top or bottom by only putting a small piece of tape at the top or bottom face of the mold. Beagling will sometimes cause the boolits to be slightly out of round, but I have found that as long as the boolit casts large enough the out of round will be taken care of in sizing. If the mold is already prone to finning it will make it worse. Also, if you are using an alloy with a lot of tin you can get finning since it will flow into the vent lines more easily. You also should check regularly to make sure the small bits of tape have not fallen off while you are casting.
Beagling and honing are not the same. I recently got a LEE 6 hole 44 mold - all holes cast small (0.427-0.429", and yes it was a 44 mag application), and as a side note dropped bullets w/ difficulty.
I cast several times from each hole to measure so I knew what I had measurement wise, took a representative bullet from each hole, cut a slot on their base w/ a hacksaw, mixed up some 600 grit lapping compound and light machine oil, coated the bullets for each hole lightly w/ the lapping compound & oil, inserted in the mold, closed the mold, spun the bullets by drive groove cut by the hacksaw and a standard bit powered screw driver, cleaned the mold, cast 4-5 more from each hole (segregate, keep track) and did this 2-3 times until I got the cavities where I wanted and cast at sufficient size.
Side benefit was all burrs are gone, and bullets fall out on opening the mold.
Another way beside slotting a bullet would be to put a screw in it and cut off the top. You can then attach the drive chuck to it or leave the head on for a screwdriver.
I've used this method to increase the diameter of driving bands while leaving the rest of the cavity the same. I cast several bullets then just added abrasive to the areas I wanted to enlarge. Works very well to increase the diameter. 002" or so. Clean often so the abrasive doesn't get into areas you don't want to enlarge.Quote:
Originally Posted by MT Gianni
Beagaling a mould you use hi temp tape and all cavities dimensions get increased. Lapping a mould you can change just 1 cavity but seldom just 1 area of a cavity. Lapping can not only increase size but also improve concentrically.
I spot the bullets thru the sprue plate and drill them, size is so a piece of 1/8" keystock fits in snug. I then epoxy a piece of 1/8" keystock in the hole this gives a stem that a tap handle can be used to drive. I "load" the bullets by rolling between 2 plates with the compound. Insert in the cavity with a drop of light oil. Carefully close blocks and work the bullet back and forth like tapping a hole forward and back thru a few rotations then move to next cavity. This will tru the cavity and increase size. Remember to go slow and check often you cant lap smaller only bigger. The biggest thing is choosing what grit to start with. to coarse and size jumps to fast to fine and the process takes a long time. When lapping once you start the compound naturally breaks down getting finer and finer as you go. Dont add more compound just a light oil to keep it sharp and cutting. This is why starting to coarse is a problem the compound dosnt get a chance to break down and finish suffers.
Lapping a hole or cavity is 2 for 1 for every thousandth you remove you get 2 thousandths on size.
When I lapp a mould I normally start with 320-400 grit. I check size by heating the mould and casting some bullets then measure them when cool. If more is needed these bullets can be used
Machinists hand book (especially earlier editions) have very good sections on lapping and finishing. The earlier editions also have the how to on grading your own lapping compound from the grinder ash around your pedestal grinder. Lapping compound can be expensive and a can can be a lot . this allows you to make and grade small amounts cheaply.
I would be looking to lap, not add a spacer between halves. I had thoughts of taking a cast bullet and drilling and tapping a hole and run a headless screw in as a means of turning the bullet. I like the key stock idea too! Makes sense to use a fine compound first, clearance would be tight.
I just recently polished out some cavities thusly:
Insert bullet into cavity and close mold.
Clamp mold into drill press drill a pilot hole in the center of the bullet.
Use the drill press to push a 1/4" drive hex/Allen bit into the pilot hole.
Coat bullet with lapping compound and slowly turn.
Not sure how long that's going to take to actually up the diameter - I was polishing to improve bullet release.
Bigslug, did you use the same alloy as you usually do? Since I use lino, I was thinking of using pure lead for the lap, should be a tad smaller and turn easier.
No special cast done for the laps. I used my "working bullets" cast out of #2. You can use your handles to alter closing tension on the mold as you spin the lap by hand, or back off the tension of the vise you held the mold in while drilling the bullet.
I have put a rubber band on the handles to maintain tension easier.
When drilling in the mould make sure and have the depth stop set so you dont drill thru the bullet into the mould.
Make your lapps as you go with the bullets cast to check size.
Anyone tried a bore brush (loaded with an abrasive) in an electric drill for the initial metal removal?
Be careful not to take down the face of the blocks beneath the sprue plate.
Rather than fool around drilling for a screw, I have:--opened the sprue plate, placed an appropriate size nut over the cavity, filled to the top of the nut with lead. This makes a lap that fits and can be turned using the right size nut-driver or socket. Read about it somewhere, maybe on this site, anyway it works.
Enlarging the initial cast bullet diameter to be oversized enough to get a desired 360 full contact sizing is a slow process, requiring several pours to the bullet size as changed to further increase the size a small increment each time, at a full 360 with evenly mod.
Done it both ways and bugling generally is much faster, however, the tape only lasts for so many cycles. If testing, I usually bugle first then if the test turns out OK, then alter a mould that is made, to one that is not available, that fits an odd groove diameter.
I once got a SBR 44 with a 10" bbl in a trade that had a .4325 barrel. Got it to shoot well, then traded it off with the modified 240 SWC Lyman mould, full disclosure. Traded it for a Seville, the fellow could not get it to shoot.
Attachment 324951Quote:
Originally Posted by PopcornSutton
Some heat resisting self adhesive aluminium tape on one side should increase the bullet diameter by 0.002/003