Thread: Lapping Carborundum-Style hones

I was the recent beneficiary of several carborundum hones. I've been working on a big 8" x 2" monster all night and have left nary a dent in it. I only have sandpaper at my disposal, as my meager means do not allow me to purchase any lapping plates...

Any tips on getting these buggers lapped, or is there anyone out there who I can pay to lap these stones? If I continue to go through sandpaper like this, I'll likely use $30 of sandpaper on this one hone...

I'm hardly any kind of expert here, but I've just lapped a surgical black Arkansas stone using silicon carbide grip powder. If it can cut through that Arkie, I bet it'll cut most anything else flat as well. I bought it based on other people's recommendations from other threads on here, it wasn't expensive and worked like a charm. Worth giving it a shot if you don't want to keep running sheets of sandpaper.

If you are using ordinary sandpaper it is softer than Carborundum. You need wetndri which is SiC, same as your stones, or try the powders as above.

I just did a few hard novaculites with Silicon Carbide powder 80 grit. I used a 12X12 in marble tile and made a ¼ in dam around the perimeter with clear silicon.
I only used a teaspoon of Silicon Carbide to do 4 stones. For a single stone ¼ - ½ teaspoon should be plenty. I finished them with a 60, 80 and a 120 grit Silicon Carbide stones. It took me about 20-30 minutes to get the worst stone flat. Here’s a couple of tips I learned and/or would do the next time.

1. Use a large plate at least 18X18 in, if not a large stone will hit your silicon dam and then it leaks. You can buy a chipped or discontinued 18X18 marble stone for a dollar or two.

2. Mark the bottom of the stone with a water proof Sharpie, chisel point. Pencil comes off in a few stokes and is useless.

3. Make a mound of Silicone Carbide powder with a well in the middle then add water slowly. A thick slurry works best, add water as it dries out, I used a soapy water mix that I was soaking the stones in, worked well.

4. Keep a bucket with clear water handy, use this with a scrub brush to clean the slurry from the stone and see your hash marks and progress. I also used a piece of flat plastic as a squeegee in an attempt to keep as much Silicon Carbide on the plate.

5. Spin the stone after a while, to even the grind on the stone. I did 50 laps, circles alternating direction and figure eights.

6. Spin the plate ¼ turn to use all the plate and keep from making a depression in the plate and convexing the stone.

I bought mine from “Got Grit.com” along with a bunch of other grits I purchased, but you can purchase valve grinding compound for in various grits locally for around $6.

You will get a workout.

Originally Posted by onimaru55

If you are using ordinary sandpaper it is softer than Carborundum. You need wetndri which is SiC, same as your stones, or try the powders as above.

Sry...I should have stated that. I thought it was a given that it would be wet dry sandpaper.

I try not to assume