Float glass or similar

[transatlantic]

Are you looking for cheaper alternatives, than from the likes of workshop heaven?
£30 is probably a bit expensive for 470x220x10mm,
The trouble is you need a straight edge to check any alternatives like granite offcuts, and a ruler won't do.

I was just wondering if someone had come across something the size I was after. The glass shelf is a good call. I had of course thought about going to a glazier but don't have one local, so thought I'd ask first.

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[Terry - Somerset]

I used a granite floor tile approx 300 x 300.

To check flatness I looked to see whether reflections on other straight edges were distorted. May not be precise to within 0.001 but for the work I am capable of seems fine for sharpening chisels etc.

 

[Phil Pascoe]

If you can't sharpen something without a substrate flatter than a piece of machine polished granite I feel sorry for you. You really need to get a life.

(Sorry, Terry, that wasn't aimed at you.)

 

[Ttrees]

Another good way to check for flat is to get the closest thing to a 123 block or square thing
with a small footprint and say a 6" square.
With the granite offcuts I found translated to an error of about 1mm over 3 or 4 inches tall.
Get a light behind the square and push the block to watch it dance about.

If its just for lapping the odd plane iron or garden tool then I would have no bother getting it close working on the convex side of a granite plate as it wont dub any edges as easily.
I have my cheap diamond hones glued to the convex side of the plates for this reason.
Tom

 

[MikeG.]

... - it is stronger, for a given thickness, and breaks safely (two key advantages IMHO) - just one reason why it's used in windows (house and car) and kitchen/bathroom shelves (including mine!).

Apparently now they insist upon laminated in doors and windows below a certain height (800mm? iirc) as it doesn't shatter like toughened.

No, not so. Laminated and toughened are both considered "Safety Glazing" for the purposes of the Building Regulations. So too, believe it or not, are leaded lights.

 

[Eric The Viking]

The big, thick piece I use is from an old B+W TV where it was in front of the tube, partly to increase the contrast, and partly to block x-rays*. It's about 10mm, and I can have several strips of different grit W+D on it at the same time, which is very handy.

I also have the top of a set of bathroom scales, and recently two pieces of toughened glass from the middle of drop-down oven doors.

These are long and narrow (from the grill oven), flat and tough. They are also thin (6mm), and can flex slightly, but this doesn't matter, as when sharpening I don't use a lot of downwards pressure (let the abrasive do the work!).

All of them would smash if dropped on the workshop concrete floor, but take scratches and abuse on the actual bench with no problem.

It's pretty obvious from this thread that lots of different things work well, glass being just one of them.


*possibly. Technically the accelerating voltage might not have been enough to generate them in the first place - it might just have been a design feature.

 

[TheTiddles]

The glass doesn’t need to be flat to any high degree, you are using these tools on wood so sharp enough is... sharp enough.

Toughened or laminated glass isn’t necessary, so why pay more for it? A piece of 6mm glass enough to get all your abrasives on should be a couple of quid, round the edges and sit it on a piece of ply to protect it and off you go.

Aidan

 

[MusicMan]

More important than toughened glass is to get the glazier to grind and polish the edges (which is cheap) or buy something like a ready-made glass shelf. Sharp edges are the most dangerous bit in normal use.

Float is easily flat enough. And hough it does refer to the manufacturing process (floating on molten tin) this method gives remarkably flat surfaces - as good as polished plate glass used to be.

 

[Phil Pascoe]

Wipe the edges with a diamond plate.

 

[Fidget]

In a bit of synchronicity I see that Wood Workers Workshop are selling 12mm Acrylic sheet for just this purpose

 

[TheTiddles]

Polycarbonate, quite different! Still not convinced it’s better than glass

Acrylic comes in rolled and cast form, they look similar but rolled has a lot of residual stress in it, but is more dimensionally accurate. Cast has less stress but less accurate.

 

[sammy.se]

Would it also get gauged easily, if you accidentally angle up too high, for example?

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[powertools]

Personally I would forget all this stress and would recommend that for accurate problem free sharpening just buy a set of 8x3 diamond stones from ITS problem solved.

 

[Rorschach]

Float glass has a curve to it, a radius of 6371000000mm, I mean that's not very flat is it!

 

[novocaine]

Depends who you ask. But there is a movement that suggests your number is wrong.

Flat earthers are a weird bunch.

 

[transatlantic]

In a bit of synchronicity I see that Wood Workers Workshop are selling 12mm Acrylic sheet for just this purpose

I linked that in the original question

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[Fidget]

Oops!