Surface plate

[bernard towersParticipant @bernardtowers37738]

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 SouzaParticipant @wesleysouza81216]

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.

[JellyParticipant @jelly]

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 ChithamParticipant @williamchitham75949]

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 FarrParticipant @nicholasfarr14254]

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 martParticipant @oldmart]

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

[peak4Participant @peak4]

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 martParticipant @oldmart]

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.

[peak4Participant @peak4]

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

[VersabossParticipant @versaboss]

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 SouzaParticipant @wesleysouza81216]

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 RenshawParticipant @rodrenshaw28584]

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 StevensParticipant @timstevens64731]

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 SParticipant @daves59043]

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 SouzaParticipant @wesleysouza81216]

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 GilliganParticipant @michaelgilligan61133]

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.

[Howard LewisParticipant @howardlewis46836]

So maybe the way forward is to make up an sturdy angle iron frame (With upstanding corner pieces, and plenty of reinforcing between the side) before floating a bed of plaster onto a substantial sub base. Then place a piece of polished marble or granite. The thicker the better – twice as thick is eight times stiffer. (An off cut from a local stone / funeral mason?,) onto the wet plaster.

Hopefully, this will result in a surface plate of reasonable flatness.

Ideally the angle iron frame should have adjustable feet so that it can be levelled..

A friend of mine excommunicated, (Rightly ) another friend, who borrowed his surface plate and used it lap flat the flanges of a engine manifold!!.

Howard

[Wesley SouzaParticipant @wesleysouza81216]

Posted by Michael Gilligan on 24/11/2022 21:31:37:

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.

I follow a Brazilian YouTube channel in which a user is building a homemade lathe without the aid of heavy machine tools. All based on a file, rasket and some small cutting machines. And he instructed me to start with a surface plate so that I could build the guides and every part of the lathe that required a certain precision. Using the withworth method and with three 15mm black granite slabs, he built a surface slab with an accuracy between 0.005mm and 0.01mm and I also wondered if I could reproduce this method using the porcelain tiles I already have available and then use engineer's blue to flatten the lathe guides. An accuracy of .01mm would be fine for me.

[Michael GilliganParticipant @michaelgilligan61133]

Thanks for that, Wesley … it helps a lot

If you could post a link to the Youtube channel, I think several of us will be interested to see it.

MichaelG.

[Wesley SouzaParticipant @wesleysouza81216]

Posted by Michael Gilligan on 24/11/2022 23:12:41:

Thanks for that, Wesley … it helps a lot

If you could post a link to the Youtube channel, I think several of us will be interested to see it.

MichaelG.

Here is the channel:

[Michael GilliganParticipant @michaelgilligan61133]

That’s great, thanks Wesley

Possibly the best news is that he’s not making 800mm square plates !!

I will watch it with interest.

MichaelG.

.

Link: __ https://youtu.be/htzvYEzEzjc

Edited By Michael Gilligan on 24/11/2022 23:28:28

[Wesley SouzaParticipant @wesleysouza81216]

Posted by Michael Gilligan on 24/11/2022 23:27:30:

That’s great, thanks Wesley

Possibly the best news is that he’s not making 800mm square plates !!

I will watch it with interest.

MichaelG.

.

Link: __ **LINK**

Edited By Michael Gilligan on 24/11/2022 23:28:28

I also believe that using 80mmx80mm porcelain tiles, despite using a very rigid structure, would not support it and would flex at some point. But I intend to cut it to a smaller size, something around 60×60 or 40×40. Perhaps the fact of saying that I have the piece of such size suggested that I would use the piece in its dimensional totality.

[Michael GilliganParticipant @michaelgilligan61133]

No offence intended, Wesley … but let’s try to work consistently in millimetres if we can

When your tiles are in the bathroom, centimetres are commonly used, but ‘Engineering’ doesn’t recognise that unit and we poor old things get confused.

MichaelG.

[Wesley SouzaParticipant @wesleysouza81216]

Posted by Michael Gilligan on 24/11/2022 23:45:02:

No offence intended, Wesley … but let’s try to work consistently in millimetres if we can

When your tiles are in the bathroom, centimetres are commonly used, but ‘Engineering’ doesn’t recognise that unit and we poor old things get confused.

MichaelG.

Sorry my friend, here in Brazil we don't use inches very much, if that's what you mean. Even in engineering we use the meter metric. So, I mentioned that the measurements were around 23" (60x60cm) and (80x80cm) 31".

[Michael GilliganParticipant @michaelgilligan61133]

No, Wesley … what I meant was that you first referred to your tiles as 80cm

Then I referred to them as 800mm

Then you last wrote 80mm

Over here, at least, centimetres are not a ‘preferred unit’ in engineering and science

It honestly doesn’t matter though.

MichaelG.

.

https://en.wikipedia.org/wiki/Centimetre

Edited By Michael Gilligan on 25/11/2022 00:15:16

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