Hollow grinding question

M

Michael Minto

Guest
I'm a flat grinder, but have an interest in doing some hollow grinding. Now, with flat grinds, it's east to use a file and sanding block on a blade to smooth out and polish up a knife. How do you folks, who hollow grind, do it? All on the machine (I doubt that, but who knows)? Thanks for any info. Mike
 
I have blocks of wood that I've ground to have the same radius as my wheels (8" & 12") with leather glued to them.

These are my main backers for sandpaper but I also have dowels of different diameters to use in tricky spots like the plunge.
 
Another option is if you know someone with a 3d printer, it would be pretty easy to print a sanding block in whatever radius you want. They are getting really common nowadays!
 
Some use if you hollow grind on a 10 inch wheel, they then lay sandpaper on an eight inch wheel to clean the hollows up.
 
thanks all, for the info. think i'll give it a try.
 
Michael Minto said:
I'm a flat grinder, but have an interest in doing some hollow grinding. Now, with flat grinds, it's east to use a file and sanding block on a blade to smooth out and polish up a knife. How do you folks, who hollow grind, do it? All on the machine (I doubt that, but who knows)? Thanks for any info. Mike
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Sorry for the late reply on this. I didn't see the thread until I was looking for something else.

I do a majority of my work with a hollow grind and like it for certain blades. When I grind I'll go through the grits down to a 200g or even 400g. Then put a ScotchBrite wheel or a "deburring wheel" on the arbor of my polishing motor. You can get a nice finish in a few minutes. I have a number of sizes that I've modified the shapes to fit the need but you really don't need the size of the wheel you grind on. Most of mine are 4" and 6". The motor runs at a 1725rpm and is just the broken down motor from my old Grizzly g1015 I first had. The wheels will do a great job of getting a satin polish on the steel without needing to do a bunch of hand sanding. The only caution is to make sure you don't over heat the steel and ruin your temper.

If you are going for a mirror polish, I'll take the grinds through a 1200g belt on my grinder and then start with polishing wheels and the various rouge grits. This is all done before any guards or bolsters are added. I'm pretty OCD so I tend to have a near perfect mirror finish with a "scratch" or imperfection that you'll have to search to find in the right light.

Hope this helps.
 
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