Honing Carbide Sizing dies??

Hi,

Anybody have any experience or advice honing carbide sizing dies so the I.D. of sized cases is a little larger?
Far too many carbide sizing dies seem to be undersized. That might be OK for some folks loading magnum loads and/or using jacketed bullets.
But, my loading practices are for standard/target velocities, often using "as cast" lead bullets, ie: .432-.433" for .44 cal, .359-.360" for various 38s, and up to .455" or so for a couple old-timers.
Thank you for your help. This forum is fantastic!!!! :smile:

A tight felt wad with diamond grinding / polishing paste works for small adjustments. It's a slow process. Be conservative with grit size or polishing it smooth again will take a very long time.


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If your concerns are about swaging the cast bullets, I’d consider Lyman M dies or getting some NOE inserts for a Lee die. Although this would add an extra step to the loading process.

The ideal way is to turn up a brass or lead slug and lap the die with diamond compound starting with a coarser high concentration compound and working to finer grits. For more than .002-.003 I would recommend setting it up and grinding it to size.

Normally the carbide rings arnt vey thick or heavy so I wouldnt try to to remove a lot.

I have a set of Acro Brass Laps now but I've used hobby brass tube before. I used the expander to make the tube the right size, charged it with diamond and lapped to the new size. I used Pin Gauges to check. Arrowhead Lapidary is a good source for diamond for quality and price. First test I was shaving cartridge brass so I flared a tube, charged it with diamond and broke the inside edge of the die. I had removed the bevel when I made the hole bigger.

I thought the RCBS Cowboy dies were small and worked the brass more than I needed. I've done bullet sizing dies too.

I bought a full set of Acro Laps for $150 but if you can find the correct size for you in stock somewhere they are about $15-20 ea.

Looking at the pictures, I think the reason for the tube inside a tube was to clear the inside die threads. K&S Precision Metals makes the tube.

Greetings,

This is what I use to enlarge 32 Long dies.

https://www.mcmaster.com/4544A34-4544A343/

I chuck the die in my lathe and dial the Carbide ring true.

With the brush mounted in a chuck in the tail stock, I move the tail stock forth and back.

Be sure to use a honing oil or good cutting oil.

Run the spindle at 1000 RPM.

I will take a lot of strokes to enlarge the Carbide ring 0.0002" (two tenths of an inch).

The advantage to the Flexible Hone is that it follows the profile of the Carbide ring.

Cheers,

Dave

Hi everyone,

Thank You for all of your great replies!
I'd heard of Acro laps and the flexible lap from McMaster-Carr. For whatever reason, I wasn't sure of their application with tungsten carbide.
Previously, I'd been successful in opening up a Redding steel 44 spl die. I made a brass lap on my lathe, attached a handle to it, then worked that by hand. It was a good bit of work, but worth the effort. The same approach seemed like it might be a real slog with carbide!

Again, I appreciate your expert opinions and the time y'all took to write.

Best Regards,
Jim

Once the lap is made and impregnated it carries the medium or compound this is what does the actual work. Using the right compound and starting with a coarse enough grit for the job being done speeds things up a lot.

This seems like a great skill to develop. All of my 45 Colt sizers are ridiculously tight.

Diamond cuts carbide fast enough with a drill that you won't get bored. I use a battery drill at low speed.

The quality of diamond varies greatly. I wasted money on some from amazon. Arrowhead Lapidary has good quality at decent prices.

#320 is a good first cut and is smooth enough for finish on some things.

Mal has it right on all counts.

For something as hard as carbide, the lap has to be brass or even steel or cast iron. The grit will sink into a lead lap too fast.
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I've used brush hones since the 1960s, but I can't recall any that would cut carbide.

Thanks!
This is some great info. Reading up separately, sounds like the diamond lapping compound is much harder than silicon carbide or even boron carbide.
For this intended purpose, that seems like a very good thing!

For deciding on the exact size for a lap, how close to finished diameter do you want to go?
Do you allow some "play" to account for the lapping compound?
Perhaps I'll need to make up a couple and do it progressively?

A lap for a round hole is almost always made so it can expand to maintain fit as the hole diameter enlarges. Adjust so there is always some drag.

https://www.mcmaster.com/laps/?SrchE...rt_InpBox=laps

Thanks! It sounds like the 7/16" adjustable lap from McMaster Carr is a good way to go.
As it turns out, they also sell lots of O-rings in a variety of materials. Just what I need for some airgun rebuilds!

If they don't have it, you don't need it. Not cheap like Amazon, but all of it the best quality available anywhere on the planet. With overnight delivery to boot.

20 years ago when my team was prototyping automation equipment for GM and Ford, we placed at least one order per day with McMaster.

Our T&D shop used a Hardinge Tool room lathe (dove tail) with an electric grinder set up on the compound. Diamond coated tooling rotated at a high rpm while the carbide draw die was spinning in the collet. Once it was close to size, diamond paste was used to polish the die to a 2 mico finish and to within +/- 0.0001". Initial polishing was done using a rosewood stick with coarse paste on it to get the diamond tooling marks out then cotton wrapped brass rods were used to obtain the final polish. This was all done dry, one guy did this 12 hrs per day for at least 30 yrs. Once he was finished the ID of the dies looked like liquid mercury an absolutely smooth uniform shiny surface. Even 30 yrs ago there were all kinds of warnings on the boxes that the carbide blanks came in warning not to inhale the dust. If using different sized grit clean your die and use a new stick before going to a smaller size paste, or keep sticks dedicated to the particular sized grit. I was tasked with looking for outside vendors to make our carbide tooling since we had only one guy that really knew how to do it. Some of these shops were able to hold a tolerance of 50 millionths of an inch on diameters.

I'm surprised nobody mentioned taking it to a Shop with Sunnen Hones and getting it done right the first time for a lot less $ and sweat. Opening up a carbide die ring .001-.002 will take a lot of work and then if you don't get it right ( IE; Tapered or belled) it will take a lot more work to fix it.

The place I worked at we did carbide a lot, but we were getting paid and it didn't matter if we took longer to do it. We had guys who had literally years of experience grinding and lapping Carbide and Aluminum Oxide and were considered to be one of the most experienced Companies in the world in this technology. In Fact,,, We were bought by Coors specifically for that technology.

You can probably get what you need done right for $25.

Randy