Polishing a carbide sizing die? Problem solved!

[Butcherbill]

Has anyone tried to polish a Lee carbide sizing die, if so was it successful? My Lee 9mm sizing die leaves light scratches at the case mouth, I’ve contact Lee Lee about it and they are sending me a replacement. Just wondering if polishing the carbide sizer is possible, I’ve taken it apart and cleaned it with a nylon brush and run a steel wool wrapped bore brush on a drill through it but that did nothing.

It doesn’t affect anything with function of loaded ammo, plainly a cosmetic issue. Thought about using a dremel felt wheel and polishing compound to see if I can get rid of whatever tool marks or machining burrs are causing the scratches, would be nice to have a spare sizing die to process 9mm cases.

What’s the best way to polish carbide, cleaning mop or dremel felt wheel and compound, fine wet dry paper and oil, vibratory tumbler? Could Chuck it in the lathe while polishing as well.

 

[Potashminer]

I have no experience to polish tungsten carbide, but I believe it can be done - in old days, our mining machines underground had bits (teeth) on front end that were tipped with tungsten carbide - after some hours cutting, would see how the leading bit edges would be worn and polished - no longer "sharp" like new ones. We were cutting in potash ore - so maybe consistency of green concrete - not near as hard as the tungsten carbide was.

 

[4n2t0]

I've used metal polish and man power successfully. If it isn't some type of burr then it's probably embedded brass.

 

[Butcherbill]

I've used metal polish and man power successfully. If it isn't some type of burr then it's probably embedded brass.

It’s been like this from new, so it’s likely a burr or some other machining imperfection. Running steel wool on a drill should’ve cleaned any brass or dirt out. I’ll have a go at it with compound once the replacement shows up, would be nice if I can clean it up. Worst case I have spare parts and a die body I can use for some project.

 

[BattleRife]

Tungsten carbide is routinely shaped in industry, by grinding with diamond abrasives. You are not going to get anywhere with alumina or SiC, but a diamond paste I would expect to do the trick. 6-Micron would probably get rid of your scratching issue, while going to sub-micron can give a truly mirror-like finish.

 

[Butcherbill]

So I pulled things apart and there’s no brass build up or any visible marks to the wall of the carbide insert, ran a brass .410 brush through it for good measure.

I did notice a bit of a burr/rough edge on the top edge of the carbide ring, could feel it with a flathead screwdriver. Less scratching visible on cases after I cleaned the edge a bit. Will spend some time on it in the shop and see if I can eliminate it, with the decaping pin removed and the die in the press I can see the case protrudes past the sizing ring about as far down as the scratches go. So it at least I know where the problem is, if it’s fixable remains to be seen.

 

[Ganderite]

My 308 Lee did that. It was 20 years old, so did not owe me anything. I bought a new one.

Let us know if you find out how to clean it up.

 

[Butcherbill]

My 308 Lee did that. It was 20 years old, so did not owe me anything. I bought a new one.

Let us know if you find out how to clean it up.

Figured it out, took some small dremel sized diamond grinding bit’s I forgot I had and manually spun the die body with one hand and held a med and fine diamond bit against the upper inside edge of the carbide insert with the other. Once the edge was smoothed out I wrapped some 800 grit wet dry paper around my .410 brush and polished up, it visually shined up nice. Here’s a test case, not completely mar free but a big improvement over before.

 

[4n2t0]

Nice, good job.

 

[Potashminer]

Figured it out, took some small dremel sized diamond grinding bit’s I forgot I had and manually spun the die body with one hand and held a med and fine diamond bit against the upper inside edge of the carbide insert with the other. Once the edge was smoothed out I wrapped some 800 grit wet dry paper around my .410 brush and polished up, it visually shined up nice. Here’s a test case, not completely mar free but a big improvement over before.

....

You will be in a balance act - when you polish, you are removing material - making that hole bigger - so will not want to go more than you "have to", else will not re-size to spec?

 

[Butcherbill]

You will be in a balance act - when you polish, you are removing material - making that hole bigger - so will not want to go more than you "have to", else will not re-size to spec?

Yes of course, but all I did was break a rough edge. 800gr will not remove any noticeable amount of carbide anyway, just a little shine is all it will do. When I run it through the Lee factory crimp die in station 4 it isn’t touched by the sizer ring, so it’ll chamber fine.