Worn MP brass mold

[dearslayer]

I have 3 MP molds and love them, however I was casting some 9mm last night and noticed the cavity furthest away from the handle was leaving the boolit a little proud of the surface of the mold once the sprue was cut resulting in a sort of “Flange “ at the base of the boolit. At first I thought the top steel plate was bent so I sanded it completely flat using a piece of of flat steel plate as a sanding surface. Got it completely flat and put it back on the brass mold only to notice that light was still showing through the plate and mold surface once I tightened the screw. Then I noticed the Brass surface was worn around the the area where the screw is tightened to hold the plate. So I tighten the screw and as a result the front of the plate rises at the front and the boolit won’t be cut level with the surface of the brass block. I assume my only solution is to get the brass surface machined flat again??

[ACC]

I would think that if you have it machined flat that you will loose some bullet weight. But machining may be your only choice. I would question what you use to knock the sprue plate off the bullets and how hard you have to hit it to cut the sprue. I use mainly LEE molds but I have learned that you don't have to hit the sprue plate very hard. If you do your alloy is way too hard.

ACC

[dearslayer]

I would think that if you have it machined flat that you will loose some bullet weight. But machining may be your only choice. I would question what you use to knock the sprue plate off the bullets and how hard you have to hit it to cut the sprue. I use mainly LEE molds but I have learned that you don't have to hit the sprue plate very hard. If you do your alloy is way too hard.

ACC

Cutting the sprue is only difficult the first 2 or 3 tries at the beginning of the casting session but as soon as the hot lead heats the mold up to temp cutting the sprue becomes extremely easy. The amount of machining need would be minimal at best to make it completely flat. Even a paper thin shim might work to bring the height back to normal in the worn area around the screw hole. Think I might shop around for a machine shop near me on Monday to get their opinions as well.

[Delkal]

That wear seems minimal compared to the galling on some of my used Lyman molds and I doubt it is enough to let you see light under the plate. Is your mold warped?

First thing I would do is to LOOSEN the screw tension and see if that fixes your problem. If not I would lightly sand the top of the mold on a flat plate like you did with your plate. Use 350 grit, or a course stone and just a few full length passes. Just to flatten any high spots and do not try and get all of the burrs.

[country gent]

first with a good straight edge check the blocks top and bottom to ensure they havent warped.

I would try the flat steel and sand paper on the top of the mould. Use a fine sand paper with water to keep it cutting even. ( i would go 400-600 grit as Id rather spend a little more time than go to far to fast). I would also ink the top of the blocks with a marker or lay out ink to track show progress. Long straight even strokes with light even pressure. Let the paper and weight of the blocks do the work.

The area around the hole could be replaced with a threaded in brass bushing then worked down to the existing surface and re drilled and tapped. A lot more work and would require a drill press at the minimum. You would need to frill the hole out 2 sizes bigger then tap and screw the new bushing in. work down to blocks surface and tap for existing thread. Be sure to grind the drills for cutting brass ( much less relief) so they dont grab. Going this way I would set up the blocks and align in a good vise locked down to the table. Drill out the hole and tap. Then run the bushing in with red or green locktite to close to the top surface. let cure then drill the side screw thru and tap. The locktite is only for this operation as the set screw will anchor it after its in. then work the bushing down. This method replaces the worn surface with out taking the blocks down as much. For a longer wearing surface a steel bushing could be used.
a light coat of heavy oil on the plate then smooth the paper down will hold the paper in place and allow it to be changed easily.
When done be sure to break the sharp edges.

[dearslayer]

That wear seems minimal compared to the galling on some of my used Lyman molds and I doubt it is enough to let you see light under the plate. Is your mold warped?

First thing I would do is to LOOSEN the screw tension and see if that fixes your problem. If not I would lightly sand the top of the mold on a flat plate like you did with your plate. Use 350 grit, or a course stone and just a few full length passes. Just to flatten any high spots and do not try and get all of the burrs.

It’s worn enough that when I put a small straight edge across the blocks there is a very small gap around the area where the screw hole is. The brass has worn away just enough that even barely tightening the screw results in the plate being pulled down in that area thereby lifting the front of the plate creating the large gap at the front. Loosening the screw doesn’t help at all unfortunately. I’ll have to pull the plate guide pin ( not sure what that pin is called) if I decide to sand it down.

[dearslayer]

first with a good straight edge check the blocks top and bottom to ensure they havent warped.

I would try the flat steel and sand paper on the top of the mould. Use a fine sand paper with water to keep it cutting even. ( i would go 400-600 grit as Id rather spend a little more time than go to far to fast). I would also ink the top of the blocks with a marker or lay out ink to track show progress. Long straight even strokes with light even pressure. Let the paper and weight of the blocks do the work.

The area around the hole could be replaced with a threaded in brass bushing then worked down to the existing surface and re drilled and tapped. A lot more work and would require a drill press at the minimum. You would need to frill the hole out 2 sizes bigger then tap and screw the new bushing in. work down to blocks surface and tap for existing thread. Be sure to grind the drills for cutting brass ( much less relief) so they dont grab. Going this way I would set up the blocks and align in a good vise locked down to the table. Drill out the hole and tap. Then run the bushing in with red or green locktite to close to the top surface. let cure then drill the side screw thru and tap. The locktite is only for this operation as the set screw will anchor it after its in. then work the bushing down. This method replaces the worn surface with out taking the blocks down as much. For a longer wearing surface a steel bushing could be used.
a light coat of heavy oil on the plate then smooth the paper down will hold the paper in place and allow it to be changed easily.
When done be sure to break the sharp edges.

Thanks for the in-depth instructions on your recommended method. I checked the blocks to ensure they weren’t warped. I do like this idea even though it’s more labour intensive. I don’t understand what you are referring to regarding the end of your post referring to the paper?

[SODAPOPMG]

three ways to fix this are
1 machine the entire top of the mold however this will reduce the bullet weight and length
2 bore out the hole and install a larger dia bolt into it then machine it level with the top of the mold then drill and tap for the plate bolt
3 last but not least and probably the best is to counterbore the area around hole and install a hardened steel washer that sits even with the top of the mold blocks

[Bazoo]

three ways to fix this are
1 machine the entire top of the mold however this will reduce the bullet weight and length
2 bore out the hole and install a larger dia bolt into it then machine it level with the top of the mold then drill and tap for the plate bolt
3 last but not least and probably the best is to counterbore the area around hole and install a hardened steel washer that sits even with the top of the mold blocks

No.3 is an idea that I wouldn't have thought of, thank you for sharing.

[Delkal]

That about putting some kind of shim / washer on the block without counterboring? Would a tin can be thick enough? You will eventually need to replace it but once you find the correct thickness you can punch one out in a few minutes.

[Rickf1985]

I agree with the shim method, cheap and easy to make, modify or reverse with no change to the actual mold.

[country gent]

Wipe the flat stock with a coat of oil this will hold the sand paper in place and flat with out the pains and build up of glue.

He probably only needs .002-.003 build up at the screw a shim that thin would be delicate and may not hold up to the sliding twist of the sprue plate.

Dearslayer, where are you located Im in Northwest Ohio. If close you can come over and we can do the repair in my shop. I have a full machine shop. This repair will be easy with my equipment

[dearslayer]

Wipe the flat stock with a coat of oil this will hold the sand paper in place and flat with out the pains and build up of glue.

He probably only needs .002-.003 build up at the screw a shim that thin would be delicate and may not hold up to the sliding twist of the sprue plate.

Dearslayer, where are you located Im in Northwest Ohio. If close you can come over and we can do the repair in my shop. I have a full machine shop. This repair will be easy with my equipment

Damn … thanks for that awesome offer but I live in Ontario Canada.

[dearslayer]

three ways to fix this are
1 machine the entire top of the mold however this will reduce the bullet weight and length
2 bore out the hole and install a larger dia bolt into it then machine it level with the top of the mold then drill and tap for the plate bolt
3 last but not least and probably the best is to counterbore the area around hole and install a hardened steel washer that sits even with the top of the mold blocks

I like this idea but I don’t have the precision equipment to do this job. I do have a floor drill press but I think with the .002-003 that would have to be drilled out would require precise equipment. I purchased some 0.1mm washers from Amazon but they are just a tad too thick.

[Delkal]

Does the plate at least sit flat with the oversized washers? That looks like an extreme amount of bend for the plate to be so high off the block and I don't see how the mold is that worn. From the pics it looks like there is still some anodizing on the worn spot. If it is wear from what I see you would have had years worth of bad bullets as the mold slowly got worse.

Did this happen all of a sudden? When you sanded the under side of the plate flat was the corner near the whole (bottom of pic #2) flat with the rest of the plate or is there a bend that stoped it from touching the flat surface? I have had some used Lyman molds that got bent there and it was relatively easy to tap and rebend that area flat again.

[country gent]

Be a long drive.
While the wear is only .002-/003 at the bolt the original surface on the blocks creates a step and cocks the blocks up at an angle growing as it gets longer and farther from the pivot point.

Your drill press will do the job but you cant hold them by hand, you need to clamp them in a good vise then the vise to the table in alignment. It would be good to check the table for square to the spindle, especially if it swivels to different angles.

Put the plate back on the blocks loose and with a feeler gauge try different thickness leaves just under the far corner this will tell you what you need. Im betting .002" gets it real close to flat again.

[dearslayer]

Does the plate at least sit flat with the oversized washers? That looks like an extreme amount of bend for the plate to be so high off the block and I don't see how the mold is that worn. From the pics it looks like there is still some anodizing on the worn spot. If it is wear from what I see you would have had years worth of bad bullets as the mold slowly got worse.

Did this happen all of a sudden? When you sanded the under side of the plate flat was the corner near the whole (bottom of pic #2) flat with the rest of the plate or is there a bend that stoped it from touching the flat surface? I have had some used Lyman molds that got bent there and it was relatively easy to tap and rebend that area flat again.

It will sit almost flat if I don’t tighten the screw at all and use the set screw to hold it in place. I can still cast good boolits but a lot of variables need heeding. One being I just barely tighten the screw and the also when cutting the sprue I have to make sure the mold is at a proper angle so when I tap the plate I have to do so whereby I’m tapping it TOWARD the top of the mold in one quick cut. This insures it cuts close to the surface of the mold. I did about 300 last night and only had to toss about 20 back in the pot because of the Flange at the base of the boolit furthest away from the screw. If I’m not paying close attention then others will also sit proud of the surface of the mold. Not exactly fun doing it this way but no choice at the moment till it’s fixed.

[dearslayer]

Be a long drive.
While the wear is only .002-/003 at the bolt the original surface on the blocks creates a step and cocks the blocks up at an angle growing as it gets longer and farther from the pivot point.

Your drill press will do the job but you cant hold them by hand, you need to clamp them in a good vise then the vise to the table in alignment. It would be good to check the table for square to the spindle, especially if it swivels to different angles.

Put the plate back on the blocks loose and with a feeler gauge try different thickness leaves just under the far corner this will tell you what you need. Im betting .002" gets it real close to flat
again.

You’re hitting the nail right on the head my friend in your understanding. I’ll check that this evening for sure. Perhaps I’ll give things a go once I figure it out. If all fails I still have some tool and die friends where I worked for 32 years that I’m sure wouldn’t hesitate to help me out.

[country gent]

In a mill with an endmill it would be quick and easy to cut the surface down. the drill press will do it but requires more careful set up and care.
A piloted counter bore ( used for recessing cap head screws and bolts.) in your drill press would cut the pocket you need to have. About .090" deep you might get away with .060 then .093 or .062 thick washer and finish down.

[dearslayer]

I purchased washers on Amazon that were M8 X 14x 0.1mm and 0.2mm thick just to see if they would work but both are too thick so if I counter bored the area for say the 0.2mm I would need a 14mm counter bore? But then would the same bit have the correct size bore guide on the end. Sorry for these stupid questions but I’m not well versed on the tool and die tools etc. why would I need to go 0.90” deep?