Thick glass can substitute for granite

[hermetic]

Here's my two penn'orth
Plate glass, as in shop window or glass display shelving is ground and polished till optically flat. I have a slab about 3/8" thick which sits atop a thick baize wad on top of a slab of chipboard worktop. With the tools I have I cannot detect any area which is not perfectly flat, it therefore suits me far beyond the accuracy I wish to obtain. I use another similar set up for a lapping plate. If you drop something on a steel or cast surface plate, it needs scraping, do the same on plate glass, and it is probably in the bin! I have a close friend, ex career precision engineer, who used to make templates for a granite counter top company, and also inspect the finished work Their granite was ground flat and polished to "optical standards" as it was possible to detect defects in reflections from the granite, which used to annoy some of the wealthy clients as there seems to be a race on amongst the mega rich to have the largest single piece of granite worktop in their kitchen! Cheaper granite worktop is ground flat, but then "mop" polished which puts on a beautiful shine, but doesn't guarantee "flatness" You could of course use some bluing or lapping compound to check a piece of granite with plate glass to see if you got an even, all over "touch" but for the purposes of HM I think we are as near perfect as makes no difference. Don't sweat it, git er done.

 

[dian]

my kitchen granite plate is true to 0.015 mm over 20" x 40". if you have a 00 (din) beveled straight edge, you can find a line on the plate, that is almost perfectly flat. glass will "wrap" around the surface ist resting on. either you support it by some kind of foam or you put it on the mill table, to average out small differences.

 

[darkzero]

I'm not sure if they still go on sale but I got my import grade A 12x18 granite plate for $37 & free shipping from Enco. I was thinking that I wanted something bigger but so far I haven't had a need for a larger one. It's got ledges on the sides for easier transport but mine just sits on the bench & I keep it covered with a desk mat that was the perfect size for it.

<INPUT type=hidden name=SIITEM001 cM1="3" cM3 cM2="2"> <INPUT value=640-0422 type=hidden name=SIALIA001 cM1="3" cM3 cM2="3"> <INPUT value=1 type=hidden name=SIQTYO001 cM1="3" cM3 cM2="4"> 640-0422 12"X18" 1MP GRD A GRANITE SURFACE PLATE 1 $36.95 Y $36.95 Sub Total $36.95 Shipping $.00 Tax $3.60 P/S Total $40.55 <TBODY> </TBODY> <TBODY> </TBODY> <TBODY> </TBODY>

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[srgtherasta]

Here in lreland shipping of granite slabs is a joke so my way around this was to find a old photocopier and pinch the glass from it. Very flat but needs some support under it, cost free!

 

[Hawkeye]

I paid $20 for a 1 1/4" x 25 1/2" x 14 1/2" piece of black granite. Suits my purposes just fine.

 

[7HC]

I'm not sure if they still go on sale but I got my import grade A 12x18 granite plate for $37 & free shipping from Enco. I was thinking that I wanted something bigger but so far I haven't had a need for a larger one. It's got ledges on the sides for easier transport but mine just sits on the bench & I keep it covered with a desk mat that was the perfect size for it.

<input name="SIITEM001" type="hidden" cM2="2" cM3="" cM1="3"> <input name="SIALIA001" value="640-0422" type="hidden" cM2="3" cM3="" cM1="3"> <input name="SIQTYO001" value="1" type="hidden" cM2="4" cM3="" cM1="3"> 640-0422 12"X18" 1MP GRD A GRANITE SURFACE PLATE 1 $36.95 Y $36.95 Sub Total $36.95 Shipping $.00 Tax $3.60 P/S Total $40.55 <tbody> </tbody> <tbody> </tbody> <tbody> </tbody>

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That was one heck of a deal @ $37.
Thought I'd grab one if the price was still in that ballpark
Not only is it out of that ballpark, it's not even in the same state!
I just checked the current price and it's now risen to $113.54 :nuts:



M

 

[fastback]

Well I use granite that 12 x 18 and it has worked out well. I got mine for free from a cousin with a machine shop. This has been a good size for what I do. I also have a cast iron one I got when I purchase some machines. This one is about 18 x 24. I made wooden covers for both plates. The covers are lined with felt. As you can see I also use it to display projects I have made.

It is interesting that granite only became the material for plates in World War II when steel was in short supply because of the war effort. Because of its stability and resistance to moisture it is now the choice for plates.

 

[darkzero]

That was one heck of a deal @ $37.
Thought I'd grab one if the price was still in that ballpark
Not only is it out of that ballpark, it's not even in the same state!
I just checked the current price and it's now risen to $113.54 :nuts:



M

Holy crap! Luckily I got when I did. Just checked the latest Enco mailer & the cheapest they have now is grade B, same size with no ledges for $46. When I got mine they used to run the free shipping off $25 almost every month. Haven't seen that offer in a long time, now it's like min $50 now.

Shars offers a similar one to mine for $48, grade A, but I'm not sure how much shipping is for one.

I remember when I got mine from Enco it barely made it with a 1/4" of the plate sticking out the box & gave me a big surprise when I went to pick up the box as I had not expected how much it weighed. Luckily it did not get damaged. Someone else that ordered one around that time was not so luckily & it arrived with a piece broken off.

 

[george wilson]

Wait for Enco free shipping. Order a granite plate + whatever else you need to buy to get the minimum cost for free shipping. I've been getting heavy brass bar stock shipped for free. They may have a $100.00 min. by now. I can't blame them!!

 

[cazclocker]

Just my two cents, if you want a FLAT surface, get a granite surface plate. I got mine from WoodCraft for $36.00. But having said that, I was recently made aware of a type of glass called "Float Glass". It's manufactured by pouring molten glass on top of a bed of molten tin. The glass floats on top of the tin, and when it's cooled the glass is of a uniform thickness and EXTREMELY flat, maybe flatter than the +/- 0.0005" that my surface plate is rated.