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View PeteK's profile

Question about granite for flattening

by PeteK
posted 09-06-2016 12:40 AM

18 replies so far

View Luthierman's profile


225 posts in 1933 days

#1 posted 09-06-2016 12:48 AM

That stuff isn’t that flat. While technically, it would work, there are better options. Try and see if there are sink cutouts from granite installers. That will be better for sure.Often times they are even free.

-- Jesse, West Lafayette, Indiana

View PeteK's profile


50 posts in 1487 days

#2 posted 09-06-2016 01:02 AM

So if I go with the glass option, is just any old piece of plate glass flat enough? I asked a friend who works at a glass shop. She said plate glass and float glass are the same thing. She didn’t know about the flatness though.

View Luthierman's profile


225 posts in 1933 days

#3 posted 09-06-2016 01:08 AM

If you went the glass option, it would have to be some pretty thick stuff, and that aint going to be cheap. Regular single strength stuff moves, a lot. Plus, god forbid you aren’t super careful with setting something on it. Really, even the tile would be flat enough, its not like you are running a machine shop. Tolerances don’t matter as much as guys like to think in woodworking. The tile just isn’t very big. You will quickly realize that more space is desired for flattening surfaces.

-- Jesse, West Lafayette, Indiana

View canadianchips's profile


2632 posts in 3843 days

#4 posted 09-06-2016 01:22 AM

I used the glass from an old oven door .

-- "My mission in life - make everyone smile !"

View TheFridge's profile


10861 posts in 2332 days

#5 posted 09-06-2016 01:38 AM

Not regular glass. Float or plate glass.

Personally, I have a sink cutout from a granite countertop. I got the same scratch patterns when I tested all around the piece.

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

View JAAune's profile


1885 posts in 3163 days

#6 posted 09-06-2016 01:44 AM

It depends upon how precise you need to be. If you’re planning on slicing 2” wide shavings at .001” thickness, you’ll need to get those soles and blades very flat. If you’ve got .002” variations in your plane setup, those .001” shavings aren’t going to happen.

I just use my jointer table for my flattening surface. Since I mostly use planes for the occasional quick job, I’m not concerned about getting that perfect setup. My shavings are a little thicker than the ideal for a proper smoothing plane.

-- See my work at

View TarHeelz's profile


69 posts in 2927 days

#7 posted 09-06-2016 01:51 AM

If your have a Habitat for Humanity ReStore location near you, just pop in there and pick up a chunk of granite countertop. Super cheap and if you get lucky, it might be of a shape that you could turn into the top of a worktable of some sort in the shop.

-- Tar Heelz, Durham, NC USA

View nightguy's profile


213 posts in 1508 days

#8 posted 09-06-2016 02:17 AM

How about your cast iron Table Saw top if you have one.

View TheFridge's profile


10861 posts in 2332 days

#9 posted 09-06-2016 02:23 AM

People swear by their cast iron tops. Cast iron is a live material that can change shape when subject to stresses. I found that out first hand with my unisaw top. Looked a potato chip because the previous owners didn’t support the extension table or 52” fence.

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

View Aj2's profile


3319 posts in 2644 days

#10 posted 09-06-2016 02:36 AM

Even if you found a piece of 1/4 glass that was free or flat.It will only be as flat as the surface you place it on.You will have to push down and it will bend enough to make a difference.
If you want to play you got to pay.
Where I live there is lots of machine shop coming and going.
Granite surface plates are cheap compared to what a new costs.


-- Aj

View DirtyMike's profile


637 posts in 1748 days

#11 posted 09-06-2016 03:03 AM

Fridge nailed it on the flatness of cast iron. I use a big chunk of 2 inch thick granite from a counter top. Took it to the machine shop and they said she was flat as a fritter. another plus for granite is taking pictures with it as a background..

View BurlyBob's profile


7836 posts in 3111 days

#12 posted 09-06-2016 03:09 AM

I’m on board with Jesse. I found a granite shop that will let me poke thru their scraps so they don’t have to pay the garbage dump. I’ve got 4 long narrow pieces for plane flattening and one set up with 6-7 grits for chisels and irons. I’ve got no complaints about the results I get with it.

View realcowtown_eric's profile


638 posts in 2783 days

#13 posted 09-06-2016 03:34 AM

you’d be likely money ahead to go to the local granite countertop folks and buy a 24” sink cut for less money


-- Real_cowtown_eric

View MaurerPower's profile


21 posts in 1496 days

#14 posted 09-06-2016 03:48 AM

I haven’t gotten a chance to use my granite yet, but what others are saying is true. Glass is expensive! Especially a piece big enough for a no 8. The tiles are small and the ceramic tiles that are long are not flat at all (I used a straight edge from the tool section at lowes to check). The counter tops also aren’t perfectly flat though. Some light was showing under my straight edge when I checked it over a length of 24 inches. However, the straight edge might also not be perfectly flat because it is made in China. If you want to go the counter top option call around to some local marble and granite installers, and they will have a big pile of cut offs to choose from for a very cheap price. My piece was $12 for a 6”x36~” piece.

View PeteK's profile


50 posts in 1487 days

#15 posted 09-06-2016 04:17 AM

So the concensus is granite is ok unless it’s not. Same for glass. Lol

View mandatory66's profile


202 posts in 2976 days

#16 posted 09-06-2016 04:26 AM

Iv’e been using a 12×12 piece of marble tile I got from Home Depot seems flat enough for plane blades. I can get .001 shavings from any plane I own. I use the top of my table saw to flatten the sole of a plane. If the sole is really bad I use my large Grizzly belt sander & finish up on the saw table.

View HokieKen's profile


15038 posts in 1984 days

#17 posted 09-06-2016 01:09 PM

I used 12” granite tiles from the big box store for scary sharpening and flattening short planes for a long time. Still use it for dressing the back of chisels and flattening planes. Here’s the trick… buy about a dozen of the tiles. Pick them at random from as many different boxes as you can. Take them home and use a straight edge to find the flattest one. If you can’t find a flat one, do it again. Now just return all of the ones that weren’t flat.

The reason for picking from different boxes is so hopefully they were processed from different slabs. If all of them you buy came from one dished slab, they’re all gonna be dished to some degree.

-- Kenny, SW VA, Go Hokies!!!

View PeteK's profile


50 posts in 1487 days

#18 posted 09-06-2016 10:34 PM

I got a 12” by 12” piece of 3/8 float glass for $15. I will use that and see how it goes.

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