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Surface plate

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Nicholas Farr23/11/2022 13:37:19
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3988 forum posts
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Hi, I suppose it really depends on how flat you need a surface to be for your needs. I bought this first table shown below, from a car boot sale about twenty years ago, for very little money. It wasn't exactly flat, as it had a very slight bow in the mid-section, about a quarter of the length of the long side. This is 6.9" long by 3.9" wide, and for many uses it was good enough. Not so long ago, I decided to mill the surface, which I'd often though of doing, but couldn't think of a suitable way to hold it on my old Chester Champion milling machine, as any vice I have would not allow full coverage of the cutter. However, I do have a large vice for my Warco Major machine and was able to true up the sides and then hold it just above the vice jaws and just gave it a cut a few thou deep. checking with my straight edge on it in various directions showed an enormous improvement to the whole surface and using my mini surface gauge holding a DTI while moving it over as much of the surface that I could, the needle only moved a whisper away in either direction from the 0 point. OK, it's probably not a super precision way of checking flatness, but it is good enough for what I need.

sp#1.jpg

This other table I bought from a stand at the recent Midlands exhibition, again at a very reasonable price, it had a few slight rusty areas on it, but these were cleaned off with some fine scotch bright and fine metal polish. This one is about 6" across the flats, using my straight edge, shows a tiny bit of day light in various places, but again not any real amount for me to worry too much about, Using the same method as before, it was found that most of the surface was below the top left side edge by about 1/2 of a thou and only wavered a whisper each way.

sp#2.jpg

Both these are cast iron and have three-point level positions on their underside, despite their small size.

Regards Nick.

Rod Renshaw23/11/2022 15:01:51
438 forum posts
2 photos

Jason makes a valid point ( as usual), about some porcelain tiles being hard.

Porcelain is a ceramic and ceramics vary a lot in their properties, so some harder porcelain tiles, some of which will be flat enough, will be fine for a marking out surface. Certainly they will be much cheaper than a commercial surface plate and will probably be satisfactory for the kind of purpose most of us here would use them for. One would be best to take a steel rule to the shop to check for flatness and perhaps to tap the tile, I suspect a hard tile would ring more than a softer one.

Rod

Jelly23/11/2022 15:30:45
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Posted by Rod Renshaw on 23/11/2022 13:35:30:

...

If I wanted a surface plate I would buy one.

Could not agree more!

I was looking to get my cast iron surface plate re-calibrated after some damage which meant it needed to be reground, and the chap quoting me said:

"I can sell you a newly calibrated Granite Surface Plate for less than the cost of me reworking your Cast Iron one. My suggestion is let me sell you a granite one, then when it comes back from the grinding shop drill some holes in the existing one for clamping accessories and you'll have a really excellent fixture table for welding!"

I think a 600x600 surface plate, Grade 1 would have set me back just over £200, which is not nothing, but is a lot less than the time, equipment and opportunity cost of trying to make (or remake in my case) such a precise surface.

Edited By Jelly on 23/11/2022 15:31:05

Bazyle23/11/2022 16:02:59
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Jelly - perhaps buy the new one then scrape your old one against it? I just had a look at a bit of granite worktop 18"x 18" I have just as a solid base for small machine and thought of checking it against my actual granite lump but one attempt to lift a corner quickly changed my mind.
I do have a long strip of epoxy stone worktop that came with some loco frames for setting them up without twist. It may not be precision but it feels like an effort is being made.

Are ceramic tiles hard all the way through or could it be porous with a hard glaze?

bernard towers23/11/2022 16:05:23
1221 forum posts
161 photos

Sorry Nicholas but your bit about your straight edge showing a bit of light is a bit non technical as , how good is your straight edge and also light will be visible even if its down to a millionth of an inch?

Wesley Souza23/11/2022 16:12:45
15 forum posts

hi guys, I am very grateful for all the contributions, but from what I could see my idea is not usual. I only suggested such a procedure, because in my country the price of a surface plate is not very attractive. The currency is 5 times less than the value of the dollar and our friend the government still charges 60% for imports. Thank you for all your help and I will look for another method or alternative.

Jelly23/11/2022 16:15:53
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Posted by Bazyle on 23/11/2022 16:02:59:

Jelly - perhaps buy the new one then scrape your old one against it?

It was a consideration at the time but for precision purposes I want one which is calibrated to a known standard, so buying new covers that off...

I think I'm actually going to end up re-using the reground cast iron surface plate as a machine table in an upcoming project, in which case scraping it in would be excessive, especially considering I expect to have to do a fair bit of scraping on other parts...

William Chitham23/11/2022 16:16:12
156 forum posts
56 photos

The three plate process is fascinating and one day maybe I'll get around to having a go but in the meantime I bought a decent 24"x18" granite plate second hand for £40 or so which good enough for me. There are plenty of videos on YouTube as has been mentioned, definitely worth looking at Oxtools and Robin Renzetti (ROBRENZ) for cast iron and granite but you might find this a bit nearer to what you are contemplating: Shed Dweller . He is using granite floor tiles but the principles might be applicable to porcelain.

William.

Nicholas Farr23/11/2022 18:54:09
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3988 forum posts
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Posted by bernard towers on 23/11/2022 16:05:23:

Sorry Nicholas but your bit about your straight edge showing a bit of light is a bit non technical as , how good is your straight edge and also light will be visible even if its down to a millionth of an inch?

Hi Bernard, well I did say it was a tiny bit of light, however the straight edge in question is a M&W 6" Toolmakers No. 315, it's not absolutely pristine but it is in very good condition and no deflection can be seen when the edge is passed from one end to the other under a 0.0005" resolution 0-1" DTI.

Regards Nick.

Edited By Nicholas Farr on 23/11/2022 19:03:04

old mart23/11/2022 19:05:08
4655 forum posts
304 photos

The first plate that we had at the museum, still used for some jobs, is a 12" square of thick float glass from a glass merchant. It's at least 1/2" thick and sits in a wood frame with a lid made by one of the volunteers. For small jobs, it is excellent and might be very cheap, depending on whether the glass originated from a damaged shop window, and cut to measure. It has many scratches, but could be turned over to the new side if necessary. The scratches do not affect its flatness.

I bought a low grade 2 foot square cast iron table on ebay for about £55 and together with the seller, just managed to get it into the back of my Corsa D upside down. Fortunately there were four holes through the top tapped 3/8 UNF, and when I got it to the museum the next day, a Sunday, I was able to make a couple of lifting eyes to use the engine hoist to get it out. I needed it out as it was on top of my spare wheel.

Edited By old mart on 23/11/2022 19:13:41

peak423/11/2022 20:30:39
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2207 forum posts
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Posted by Wesley Souza on 23/11/2022 16:12:45:

hi guys, I am very grateful for all the contributions, but from what I could see my idea is not usual. I only suggested such a procedure, because in my country the price of a surface plate is not very attractive. The currency is 5 times less than the value of the dollar and our friend the government still charges 60% for imports. Thank you for all your help and I will look for another method or alternative.

I'm not sure where you live, but how about this for a suggestion as a development of a conversation I had with a friend some time ago.
This friend, before his retirement was heavily involved in calibrating surface plates, the methodology, and the documentation, at quite a high level nationally.

His suggestion was that for most home workshops, and indeed some commercial ones, the most cost effective solution is a sheet of new good quality float glass, at least 6mm, and maybe a bit thicker if you can get it.
Ideally as fresh from the factory as possible, as an older new pane might have taken on a bit of a bend if it's been leaning against a wall for years.
The glass itself will flex, or distort according to how it's supported.
As mentioned by a poster above, a good way of supporting it horizontally, is to make a frame, and fill it with normal common plaster, as used on walls. The pane of glass is then floated on the plaster whilst it's still wet, so will be fully supported when the plaster cures.

The problem might be how to get a frame base, which won't bend with time, or warp if it's made of plywood.

You already have some fairly stable tiles, though they may not be flat enough to use as a proper surface plate.
Maybe use one, or more, of those as your base laminated together with plaster, frame it, fill the frame with plaster and float your glass on top.
That should prove both rigid and flat enough for most uses; I did try something similar, and it was fine for marking out and checking flatness etc, but it wasn't that good at retaining engineers blue for transferring onto other items.

The other consideration will be having a long flat strip of something along one edge to run a surface, or height gauge along.

On my normal workbench I have a 0.5m square of granite work surface, 40mm thick.
It's fine for rough and ready marking out, but it does have a dip of about 3 thou, so not good enough for blueing components.

Bill

old mart23/11/2022 21:03:46
4655 forum posts
304 photos

One reason why the 12" square glass plate has not neen turned round yet is because I used about 20 of those square sticky fixers to hold it onto the wood backing. Rather hard to remove, it might need a thin wire to cut through them, or a pallette knife.

peak423/11/2022 21:08:18
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2207 forum posts
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Posted by old mart on 23/11/2022 21:03:46:

One reason why the 12" square glass plate has not neen turned round yet is because I used about 20 of those square sticky fixers to hold it onto the wood backing. Rather hard to remove, it might need a thin wire to cut through them, or a pallette knife.

How about a hot wire, similar to that used for cutting foam etc.

Bill

Versaboss23/11/2022 22:56:19
512 forum posts
77 photos

Maybe a bit late in this discussion, but there are some things which I find hard to believe.

Mr. Souza wrote in his first post that he has porcelain tiles"...from my bathroom remodeling and they are 80 cm x 80 cm..." In another post, he wrote that his tiles have the same thickness as a granite kitchen top.
Now in my kitchen I have a granite top, and it is 30 mm thick, or if you like 3 cm. I can stand on it no problem (well, I'm not unduly heavy). So the volume of such a tile is 80 x 80 x 3 cm^3, and when I guess that porcelain has a specific weight of at least 2, that would result in a weight of nearly 40 kg, or maybe even more.
Pity the tiler who has to glue these monsters on a bathroom wall...

In short, I can't believe that until I can see it, and I wonder why not one of our usual sharp eyes took notice of that.

Regards,
Hans

Edited By Versaboss on 23/11/2022 22:57:23

Wesley Souza23/11/2022 23:19:02
15 forum posts
Posted by Versaboss on 23/11/2022 22:56:19:

Maybe a bit late in this discussion, but there are some things which I find hard to believe.

Mr. Souza wrote in his first post that he has porcelain tiles"...from my bathroom remodeling and they are 80 cm x 80 cm..." In another post, he wrote that his tiles have the same thickness as a granite kitchen top.
Now in my kitchen I have a granite top, and it is 30 mm thick, or if you like 3 cm. I can stand on it no problem (well, I'm not unduly heavy). So the volume of such a tile is 80 x 80 x 3 cm^3, and when I guess that porcelain has a specific weight of at least 2, that would result in a weight of nearly 40 kg, or maybe even more.
Pity the tiler who has to glue these monsters on a bathroom wall...

In short, I can't believe that until I can see it, and I wonder why not one of our usual sharp eyes took notice of that.

Regards,
Hans

Edited By Versaboss on 23/11/2022 22:57:23

Hi, here in my country we don't use such thick granite slabs to build sinks or even floor slabs. It is customary to use the 15mm measurement, I believe it is to save raw material. And the porcelain tiles are in a measurement range of 12mm.

Rod Renshaw24/11/2022 17:36:31
438 forum posts
2 photos

We don't know where Wesley lives or what accuracy he needs from his "Surface plate", but we now know that he will not find it easy to just "buy a plate" because of import restrictions.

So I wonder if we can apply some lateral thinking and suggest something he might find easily in his location that would be flat enough? What about a brake or clutch disc from a car or commercial vehicle? Might such be flat enough? Any other ideas?

Rod

Tim Stevens24/11/2022 17:49:25
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There is a simple way to check - in the shop - how flat a tile is. Hold it about horizontal and look at the reflected view through a bright window. Move the tile around a bit and look for wiggles in the reflection. With no wiggles, and a view that in all respects stays constant - no distortion - you can be fairly sure that the surface is flat*. Ceramics will only be flat, though, if they are ground, like granite always is. That doesn't mean, though, that granite tiles are always flat, they still need to be checked by the same method. It is more difficult to do this test with a surface plate, whether granite or iron, as holding them up at arms length is jolly hard work.

*It could, though, be part-spherical, domed or hollow, but this is not likely with normal surface grinding.

Cheers, Tim

Edited By Tim Stevens on 24/11/2022 17:51:28

Edited By Tim Stevens on 24/11/2022 17:52:31

Dave S24/11/2022 20:35:31
433 forum posts
95 photos

When I did the kitchen worktops in our old house I used granite floor tiles. I still have some off cuts in the garage.

That same kitchen also had porcelain floor tiles as it happens

Both tile types were roughly the same thickness, around 15mm

I can tell you that the granite tops looked spectacular, and were *considerably* cheaper than getting a kitchen fitter to put in a “solid” granite worktop.

The floor tiles had a perfect reflection, so were quite flat, but I wouldn’t like to use them as a surface plate - too thin.

Wesley Souza24/11/2022 21:17:08
15 forum posts
Posted by Rod Renshaw on 24/11/2022 17:36:31:

We don't know where Wesley lives or what accuracy he needs from his "Surface plate", but we now know that he will not find it easy to just "buy a plate" because of import restrictions.

So I wonder if we can apply some lateral thinking and suggest something he might find easily in his location that would be flat enough? What about a brake or clutch disc from a car or commercial vehicle? Might such be flat enough? Any other ideas?

Rod

Hi Rod, thanks for your reply and for your concern. So, I live in Brazil and here imported products are very expensive, very expensive. That's why we try to build things because that's the only way it becomes reality. It is very common here, lathes, milling machines and all kinds of homemade tools. Sometimes it's a little embarrassing to ask questions about how to build something, because people uninformed about the reality I live in always answer: " hey, why don't you buy it?" and "Hey, I went to the used trade and paid cheap" I don't have that cheap option. I went on a website the other day to get answers and an OP started saying about his "amateur" shop.- "I have 3 lathes, 2 milling machines...." I got embarrassed and gave up asking. This is my story😂

Michael Gilligan24/11/2022 21:31:37
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No need to get embarrassed here Wesley … just ask straight questions, with as much background detail as you can, and someone will answer appropriately.

My question to you is about your motivation

I am still not sure whether you mostly want the end-product, or the exercise of personally demonstrating Whitworth’s process.

… I suspect it is a bit of both, but please tell us

MichaelG.

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