using sandpaper on a glass sheet to sharpen chisels

[Freedom Nut]

Hi everybody,

This video

suggests using a 1/2" sheet of glass under different types of sandpaper to sharpen chisels and plane blades.

My question is about the 1/2" thick sheet of glass, because they seem to be so darn expensive. Why should it be 1/2" thick? Is it to eliminate any flex in the glass that would occur if it were less than

1/2" thick?

I ask because I have several cheap glass panes--from picture frames, mind you--that I'm willing to attach together for a TOTAL WIDTH OF

1/2". (Would this suffice?)

Is there something even less expensive than a 1/2" sheet of glass that anybody here would recommend?

[Freedom Nut]

The video is at

[CW]

The reason 1/2" glass is often recomended is so it won't flex. It won't flex anyway if you have it on a flat surface. Take your 1/4" glass and put it on a piece of mdf. It'll will work fine.

[Freedom Nut]

CW,

A-ha! I suspected as much!

The lady at the glass shop also suggested 1/4", which is about $50 less than the 1/2". They sand the edges for free, too, all for about $12. Sold.

Thanks for your help, CW, now and in the future, because you'll probably see more elementary questions with my name under them. :->

-Eric (even more of a Freedom Nut now)

[-MIKE-]

Broken off pieces granite. Check with HD, Lowes, or a local granite/marble supplier.

[MikeWhy]

How expensive? Woodcraft sells granite surface plates for $30'ish. They're unyieldingly flat, but heavy and clumsy to move around. As far as I can tell, they're as flat as real granite surface plates. I own one, and use it for sharpening sometimes, but not one of theirs.

(Woodraft is on my bad list this moment. I flushed my shopping cart contents as of yesterday afternoon. I'm more than a little peeved at the fine print I didn't notice on their promos, first last month, and again a coupla days ago. They boasted "FREE SHIPPING" last month in their before Christmas specials. So I ordered a little corner chisel as a stocking stuffer for myself. Bummer; they charged $8 to ship the $7 item and included a coupon for free shipping on the next order. For sure, I thought, this must've been on their website somewhere and I just didn't notice. No big deal. So, I slowly gathered a few items into the shopping cart over the next couple of weeks. Yesterday, I went to check out, and the coupon code was NFG. Reaching for the goggles, I can make out the small print that says "Expires 1/18". Great. So I figured out how to get free shipping. Didn't pay nothing for shipping on the empty order. F*ckers.)

[Freedom Nut]

Thanks, Mikes.

It's kind of hard to argue with a $12 glass, so I'll mount it to a board (I still need to look up "jig," and therefore not yet sure if I'm using it in sentences correctly) and reply back here to let you all know what I think. I used to use cheap glass sheets from picture frames when doing any kind of tracing, and I sliced my fingers a few times, so I'm guessing that the 1/4" glass with treated edges is going to be like a luxury.

[lenhow]

I use a few left over(discontinued) granite samples. You might check dealers in your area .... they most likely have cut offs etc. they would part with cheaply. (go at the end of the day and bring cold beer)

Lenny

[Ed Edelenbos]

Re: glass... it's possible to ease edges of glass using a belt sander with a 150+ grit belt. Just go slow and wear eye protection. It works on any glass from 1/8" up.

Re: alternative surface... I stopped in at a local tile store and bought a single 12x12 tile. They labeled it "sample" and it ran me a whopping $2.64 ($2.50 plus tax)

Ed

[-MIKE-]

Ed, are you sure those are flat enough for sharpening?

[J. Clarke]

Granite tile for five bucks or so?

[-MIKE-]

I don't know. I'm talking about pieces that break off of the big slabs sitting in those big racks at the stone suppliers. Sometimes the home stores have pieces from counter tops that have fallen down a broken.

[Maxwell Lol]

Enco has a 12x18 granite plate for $24.95, and a 8x12 for $14.95

Current coupons are

WBJ9C - 10% off purchases of $99 or more WBJ9R - free shipping on orders of $50 or more - expires Jan 31st.

You just missed the coupon for free shipping on orders of $25 or more.

Here are the plates:

[Ed Edelenbos]

I've got wet/dry paper of successive grits on the 4 corners of the tile (stuck on with 3m spray adhesive). I made some blocks at 25 and 30 degrees My chisels are the sharpest they've ever been. They cut the best they ever have, at least.

Ed

[spaco]

We had good luck many years ago getting a sample grave marker from a monument company. The samples were engraved, but only an inch or two thick. There was plenty of unengraved surface around the edges for your purpose. An engineer at our company told us that these monuments are remarkably flat due to the process used to polish them.

I think we got ours for free. We had to rebuild a heater assembly in the field. It needed to have heat diffusors recemented to a hollow faced bronze heating device and the diffusors had to be very flat. We got some funny looks carrying that tombstone into the motel room where we did the work.

Pete Stanaitis

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Freedom Nut wrote:

[-MIKE-]

Cool. I was thinking about this. I'm used to dealing with a surface that has to be completely flat across the entire surface. For the vast majority of sharpening, you're only using several square inches of surface area at a time. It doesn't matter if there's a bump in the middle, as long as the area you're using is flat.

[Bored Borg]

On Thu, 22 Jan 2009 05:52:11 +0000, MIKE- wrote (in article ):

If you want astronomy lab flatness, buy two and lap 'em face to face with abrasive paste, lifting and turning occasionally. Tedious beyond belief but you'll get a perfect surface. Don't rock over the edges!!!!

You\re getting close when the cleaned plates stick together with a drop of water, but if the surfaces are evenly matted I'd say that's "done"

Hell, just use MDF... :-)

[Limp Arbor]

Now that you have the glass this jig from Wood magazine is easy to make and works great.

sharpen side to side with it but it gets blades sharper than I was able to do by hand.

[Leon]

Snip

Why should it be 1/2" thick? Is it to

I don't use this method however I have used to use a lot of PSA/self sticking sand paper. I have to think that one of the primary reason to use thicker glass is to lessen the possibility of breaking the glass when trying to remove the old sand paper or if not used on a perfectly flat surface to lessen the possibility of breaking the glass. Some brands of PSA sand paper can be very difficult to remove. A secondary reason could be to insure a surface that stays flat however there are easy ways to insure that thinner glass remains flat, fasten it to a flat surface.

[Len]

When the local bank was redoing their lobby, a slab of polished granite that was supposed to go on the wall was dropped off the truck. I was able to get a couple of nice chunks from the remains. One is now dedicated to my sharpening station.

Len