Lapping Arks

[KW Driver]

mine's just a little bitty thing, 1x4 but I'm having trouble with lapping it. I've got SIC from 80 stepped up to 12 micron. both times I've lapped it I've dished the center as the sic breaks down to dust and packs into the center area that doesn't get pushed outside the ark's surface area, with long axis ellipticals primarily.

how much SIC do you lay down, and how do you spread it out? I'm taking a smallish pinch and trying to essentially "salt" the surface as best I can, but it clumps.

and if there's any other threads with pictures or better descriptions, I'd love to see them, I couldn't find them.

 

[kcb5150]

How far out is it? You could try lapping it dry on fixed grits

 

[KW Driver]

not too much out, but it's there, to the point that I'm essentially honing on the outer edges of the stone. it really only shows when trying to burnish it. I tried getting it down with some 12m lapping film but basically burned through the film. looks promising as a burnishing technique though.

 

[eKretz]

What are you using as a lap? Did you check to make sure it (the lap) is flat to begin with? The most likely problem is that your lap isn't flat. How far out of flat was the hone when you started? It should be cake to flatten a 1" x 4" stone.

The amount of loose grit you'd want to use will depend on the size of your lap. On my 6" x 12" lap I use about ¼ - ½ teaspoon per recharge, and rewet the lap as necessary. Just sprinkle it on the surface somewhat evenly - it doesn't matter if it's perfectly even. You shouldn't be getting clumping though, that's odd. Is your loose grit wet?

Also, don't keep lapping after the grit breaks down to where it feels way finer, you will just be spinning your wheels and not getting much done that way. When it starts to feel like the grit has broken down into much finer particles, recharge the lap with another ¼ teaspoon of grit and a splash of water and continue lapping.

 

[Jayber Crow]

I've always started lapping with 220 grit SiC powder and find it works pretty quickly; then I finish with 500 grit. I tried using 80 and just didn't like the way it performed; I abandoned it pretty quickly.

Yes, and make sure your lapping surface is flat as eKretz mentioned.

 

[kelbro]

Wet or dry? I now prefer to lap with dry grit. No clumping.

 

[tetraodon]

mine's just a little bitty thing, 1x4 but I'm having trouble with lapping it. I've got SIC from 80 stepped up to 12 micron. both times I've lapped it I've dished the center as the sic breaks down to dust and packs into the center area that doesn't get pushed outside the ark's surface area, with long axis ellipticals primarily.

how much SIC do you lay down, and how do you spread it out? I'm taking a smallish pinch and trying to essentially "salt" the surface as best I can, but it clumps.

and if there's any other threads with pictures or better descriptions, I'd love to see them, I couldn't find them.

i use a spoon to help spread it, and i add a tiny bit of water, what are you lapping on? i use a granite tile and havent had clumping issues

 

[KW Driver]

yes, my lapping plate was flat, I lapped dry. the 500 I have is a powder anyway. based on the volume, I guess I didn't have enough SIC under the stone. I also tried to spread it with finger taps. may try a spoon with more volume of SIC if I do this again.

got it done on 800 then 2000 wet/dry (what I had here with me) and working on burnishing it.


but thanks for the help, gentlemen

 

[Gamma]

SIC will find it's own equilibrium if you let it. You have to keep it moving and you can't use too much and rinsing it off repeatedly helps assure even cutting.
I pretty much lap all Arks or very hard stones with it - here's a clip of me lapping an Apache but it's the same thing as an Ark for the purpose lapping with SIC powder.

 

[KW Driver]

thanks Gamma, I was working dry because I'd read it was cleaner/easier. wet in the sink looks a whole lot easier than what I did.

 

[H Brad Boonshaft]

Get a steel cookie sheet from the dollar store, and buy a progression of Silicone Carbide grits from GotGrit.com, about $15 for 60-500 ¼ oz each.


Start with about a half a teaspoon, plastic spoon and sprinkle on a wet cookie sheet, on a flat cement floor, (Garage). Mark a grid with a sharpie, pencil will wash off with the slurry.


Now use your body weight and work it. You can get to flat in 10-15 minutes with an Ark. Stay on the 60 grit until flat. Add more grit when you feel it stop cutting.


Once flat, you can run though the grits quickly, finish on Wet and Dry, on a clean Cookie Sheet as high as you want to go, usually 2k, for me.