Sandpaper backing, why granite?

J

Justin King

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Nov 8, 2009
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I have heard a number of makers mention the use of a piece of flat, polished granite to attatch their abrasive paper to for hand-finishing. I am curious why some prefer granite over other hard, ridgid materials? Is it easier to remove old adhesive from?
 
Granite "tombstones" or surface plates are the standard in metal machining for a flat reference surface unaffected by heat or humidity. They are lapped to a very high standard of flatness.

http://www.starrett.com/pages/860_granite_surface_plates.cfmhttp://www.starrett.com/pages/860_granite_surface_plates.cfm

Of interest, the granite surface plate was first fashioned because of a desperate situation during the Second World War. An owner of a monument and metal working shop in Dayton, Ohio, Mr. Wallace Herman, required a flat table for checking parts, but the military was using all the metal for artillery. Thankfully, Herman deduced that granite could be used, just like metal, for a flat surface and he manufactured the first granite plate from a piece of black stone. The original stone worked, and the technologies have evolved and improved to the very precise granite surface plates that are available today.


Imports are available for $60 12 x 18" size

Don't be afraid to dive the trash bin at a local glass shop for some nice thick 12x12" bits for free.
 
Granite has many nice and useful properties, but the basic reason so many use it is because granite is the standard material that precision flat surface plates are made out of -- if you want to make something truly flat, that's what you use to back your sand paper. See http://www.starrett.com/pages/860_granite_surface_plates.cfm for more background.

edit: dang, ninja'd

Patrice Lemée;7983263 said:
I have a granite plate but no granite sanding sticks? :confused:
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Get you some granite parallels: http://www.standridgegranite.com/accessories.htm - about halfway down - they should work. ;)
 
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I picked up a black granite-like 12x12 glossy finished ceramic tile at Home Depot for under $5.00. It is flat, fairly heavy and seems to work good--a little spray adhesive and the paper sticks nicely and peels right off when you want. Not as good as the real thing I'm sure, but it is an option.
 
I don't make any folders, for fixed knife maker a thick glass or marble surface may be flat enough. I use an 8" dia 1/2" thick round glass plate...
Emre
 
Mr. Bad Example said:
I picked up a black granite-like 12x12 glossy finished ceramic tile at Home Depot for under $5.00. It is flat, fairly heavy and seems to work good--a little spray adhesive and the paper sticks nicely and peels right off when you want. Not as good as the real thing I'm sure, but it is an option.
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What was the "name" of that thing? When I go into my local Home Depot, I'd like to avoid the dumb looks/blank stares when I ask for where something is.
- Thanks!
 
Find a place that installs Granite counter tops, they will more than likely give you their drop pieces, the pieces they cut out for the sinks are perfect :thumbup:
 
Actually I have 2 pieces 4-1/2" x 12" of granite countertop back splash, and can probably get more. I just got to wondering why it was preferred, I have used wood and metal plates for this purpose with good success.
I'm not sure the human eye can tell the difference between a blade lapped on a piece of pefectly flat granite and a blade lapped on a piece of nearly perfectly flat steel, but I understand the desire to get as close as you can for the principle if no other reason.
 
Troop said:
What was the "name" of that thing? When I go into my local Home Depot, I'd like to avoid the dumb looks/blank stares when I ask for where something is.
- Thanks!
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Well, that's a good question. I just wondered around till I got to the flooring section and they had many stacks of tiles. I simply picked a nice flat, heavy granite-looking one and made sure it was reasonably priced. I think you'd call it a ceramic floor tile if you had to ask.
 
Mr. Bad Example said:
Well, that's a good question. I just wondered around till I got to the flooring section and they had many stacks of tiles. I simply picked a nice flat, heavy granite-looking one and made sure it was reasonably priced. I think you'd call it a ceramic floor tile if you had to ask.
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Thank you for the reply.:thumbup:
 
I've used glass plates for years doing gun work.

I don't use adhesive to hold the wet dry sandpaper down,
instead I use WD-40 as a lube to float the particles,
and just spray some under the paper to act as an adhesive.

If you're working on wood, that would be a different matter.

Leadfoot
 
I use the $5 Lowes granite type 12x12 tile too. I have a couple of them that I'm pretty happy with.
 
I was surprised to find 12x18 granite surface plates for $40 Canadian at the local busy bee store(Canadian) I think they weigh over 75lbs so shipping would be a killer. I bought 2 wile I was there. But I had in mind cleaning/lapping cylinder heads, ect ect ect.
 
I bought my granite plate from enco about a year ago. They still have some of them on sale, but at that time they also had a coupon for free shipping, which was a good deal considering that it weights about 70 lbs.

--
Sergiy
 
Get on Enco's catalog mailing list and watch for the above-mentioned free shipping. Does one really need a surface that's been ground to within millionths of an inch of flatness to make knives? If Bob Terzuola and Mr. Loveless think so, who am I to quibble? Are the Enco plates made by our Chinese brethren really up to NIST Grade B standards? That's a whole 'nother question. But Enco's customer service is tip top. My first one came with a chip-- they are not crated, just tossed into a cardboard box-- and Enco sent another pronto.
 
I forgot to mention the beauty part as they say in the Bronx: a measly $24 total for a 12"x18" plate 3" thick that weighs 80 pounds, delivered to your door.
 
I have been using 1/2 plate glass also, works well and if you go to the glass companies they will usually have some cut offs that they will sell cheaply. I think I gave about 10 bucks for a 1/2 inch thick piece that was 12 x 18.

Jerry Fisher
 
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