Surface plate

[Wesley SouzaParticipant @wesleysouza81216]

hello friends, trying to recreate that famous method of flat surface plates and I was wondering if I could use that porcelain tile that is used for covering floors and walls. I have some left over from my bathroom remodeling and they are 80cm x 80cm. I've heard that ceramics are used as an alternative, would porcelain tiles also be possible? Has anyone thought of this or done it?

[Wesley SouzaParticipant @wesleysouza81216]

[Thor 🇳🇴Participant @thor]

Hi Wesley,

Welcome to the forum. Are the porcelain tiles flat? Or do you intend to use the 3 plate method? I know some use plate glass as a cheap surface plate, usually they are made from Cast Iron or granite.

Thor

[BazyleParticipant @bazyle]

Really you can only use cast iron because of the way it can be scraped. I'm not sure how other materials would respond. You can grind glass and therefore probably porcelain. Generally tiles of various sorts are gong to be thin and hence flexible so you would want to laminate a few together first.

Another possibility is to find a kitchen fitter and see if they will give you the bits they cut out of granite worktops for the sink. These are still too thin to use as is.

[Master of noneParticipant @masterofnone]

Posted by Bazyle on 22/11/2022 19:25:33:

Really you can only use cast iron because of the way it can be scraped. I'm not sure how other materials would respond. You can grind glass and therefore probably porcelain. Generally tiles of various sorts are gong to be thin and hence flexible so you would want to laminate a few together first.

Another possibility is to find a kitchen fitter and see if they will give you the bits they cut out of granite worktops for the sink. These are still too thin to use as is.

I agree. Kitchen worktops are probably too thin to give you a relaible surface plate. I can measure slight curve in my granite worktop.

See Robin Renzetti's Youtube for lapping a granite surface plate.

[Wesley SouzaParticipant @wesleysouza81216]

Posted by Master of none on 22/11/2022 19:35:32:

Posted by Bazyle on 22/11/2022 19:25:33:

Really you can only use cast iron because of the way it can be scraped. I'm not sure how other materials would respond. You can grind glass and therefore probably porcelain. Generally tiles of various sorts are gong to be thin and hence flexible so you would want to laminate a few together first.

Another possibility is to find a kitchen fitter and see if they will give you the bits they cut out of granite worktops for the sink. These are still too thin to use as is.

I agree. Kitchen worktops are probably too thin to give you a relaible surface plate. I can measure slight curve in my granite worktop.

See Robin Renzetti's Youtube for lapping a granite surface plate.

Thank you very much for your reply. It's just that I have some very thick porcelain tiles and if I'm not mistaken, the thickness is very similar to the thickness of the granite. I was thinking about it!

[Wesley SouzaParticipant @wesleysouza81216]

Posted by Thor 🇳🇴 on 22/11/2022 18:39:15:

Hi Wesley,

Welcome to the forum. Are the porcelain tiles flat? Or do you intend to use the 3 plate method? I know some use plate glass as a cheap surface plate, usually they are made from Cast Iron or granite.

Thor

Hi Thor, thank you very much for your reply. I was thinking of using the 3 board method. I saw that they are using ceramic and I wondered if I could use porcelain. It has a very similar thickness to the thickness of the granite and I thought I could save money on this step.

[Mark Davison 1Participant @markdavison1]

A granite surface plate of that sort of size would be at least 4" thick, probably more. Even my 8"x12" is 4" thick.

[Wesley SouzaParticipant @wesleysouza81216]

Posted by Mark Davison 1 on 22/11/2022 22:37:49:

A granite surface plate of that sort of size would be at least 4" thick, probably more. Even my 8"x12" is 4" thick.

sorry, I mean the thickness of the granite used in kitchen sink countertops, which, by the way, I've seen used for surface plates. of course, a ribbed bed of flat bars of common steel was used.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Wesley Souza on 22/11/2022 23:08:04:

Posted by Mark Davison 1 on 22/11/2022 22:37:49:

A granite surface plate of that sort of size would be at least 4" thick, probably more. Even my 8"x12" is 4" thick.

sorry, I mean the thickness of the granite used in kitchen sink countertops, which, by the way, I've seen used for surface plates. of course, a ribbed bed of flat bars of common steel was used.

.

May I just insert a note of semantic clarification here ?

… call it pedantry if you must !

There is [was] [should-be] a distinction between a Surface Plate and a Marking-out Table

On a forum such as this, it is perhaps inevitable that the use of the terms will be ‘fuzzy’ but it doesn’t really help in a discussion like this one.

MichaelG.

.

Edit: __ this might be useful:

https://digital.library.unt.edu/ark:/67531/metadc710079/m2/1/high_res_d/650156.pdf

Edited By Michael Gilligan on 23/11/2022 06:21:44

[Wesley SouzaParticipant @wesleysouza81216]

Posted by Michael Gilligan on 23/11/2022 06:06:56:

Posted by Wesley Souza on 22/11/2022 23:08:04:

Posted by Mark Davison 1 on 22/11/2022 22:37:49:

A granite surface plate of that sort of size would be at least 4" thick, probably more. Even my 8"x12" is 4" thick.

sorry, I mean the thickness of the granite used in kitchen sink countertops, which, by the way, I've seen used for surface plates. of course, a ribbed bed of flat bars of common steel was used.

.

May I just insert a note of semantic clarification here ?

… call it pedantry if you must !

There is [was] [should-be] a distinction between a Surface Plate and a Marking-out Table

On a forum such as this, it is perhaps inevitable that the use of the terms will be ‘fuzzy’ but it doesn’t really help in a discussion like this one.

MichaelG.

.

Edit: __ this might be useful:

**LINK**

Edited By Michael Gilligan on 23/11/2022 06:21:44

I don't know if I made myself clear, but my question is about the 3 withworth slabs method and whether porcelain tiles could be used in its construction instead of granite. I am aware of the thickness of the tile and that it could warp and lose precision, but I could use a ribbed metal base. I just wanted to hear the opinion of someone with more knowledge.

[Wesley SouzaParticipant @wesleysouza81216]

*withworth 3 plates method

[JasonBModerator @jasonb]

If you do start with three tiles your frame would only be supporting the one at the bottom, what about the one being held above it while they are lapped? What sort of size are you thinking of as the amount of flex on a 200mm plate will be a lot difference to a 450 x 600 plate of the same thickness

Me I just use a tile as it is for marking out on which seems to give me working models which is what I want. It also gets used as a surface plate.

Edited By JasonB on 23/11/2022 08:02:42

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Wesley Souza on 23/11/2022 06:51:58:

*withworth 3 plates method

.

Yes … I know it well [so I guess mine is ‘the opinion of someone with more knowledge’]

And I also know that it would be futile to attempt this with anything that was insufficiently stiff to produce a set of three plates as its end result.

MichaelG.

.

Edit: __ I suggest you start your journey here:

.

.

It is available on archive.org 

and I have recommended it on many previous occasions.

.

P.S. __ You have two unread ‘personal messages’ from me, Wesley

Edited By Michael Gilligan on 23/11/2022 08:20:04

[Michael GilliganParticipant @michaelgilligan61133]

Allow me please, Wesley, to make an entirely practical suggestion:

If [as I presume] what you really want is a decent ‘marking-out table’ of 800mm square … Just use Whitworth’s logic to check all of your available tiles and find the flatest one. Stone-down any obvious high spots on the best three but, for the sake of your sanity, please stop way short of trying to make a ‘surface plate’ out of a tile.

MichaelG.

[Howard LewisParticipant @howardlewis46836]

Whatever form of table is used, to maintain flatness, it must not be stressed.

At work, an expensive 6' x 4' x 6" granite table was ruined by being left leaning against a wall. It sagged and bowed!

In the Standards and Calibration rooms, the tables were massive cast iron, and carefully levelled, on equally massive cast iron frames.

For The WaterWorks Museum, I made a 18" x 24" table from an off cut from a grave headstone )

The supporting frame was 2 x 2 " angle iron, with the table bedded onto wet plaster on plywood..

Once sited, it was carefully levelled on a purpose made steel bench.

Howard

[jaCK HobsonParticipant @jackhobson50760]

My experience of tiles is they are not flat, not hard, and not stiff. Not a good place to start.

'Granite' is not all the same.

A bit of float glass is probably better… just use as is for layout and sharpening.

8×12 granite plates are dirt cheap for what you get.

Want to save money? I'd probably investigate restoring a worn out one first before going from scratch.

As an experiment/just for the experience – I would not start with tiles.

[SillyOldDufferModerator @sillyoldduffer]

An advantage of Granite being hundreds of million of years old is it's effectively time stable – better than cast-iron, and probably much better than tile. Granite can also be cut into much thicker slabs than tile, making it much less likely to flex under load.

I don't know how flat tiles are. Fairly good I expect, because they're made in flattish moulds, and then glazed. The molten glaze would tend to flatten under gravity.

I believe the flattest cheap material available is modern sheet glass. It's made by floating molten glass across a large tank of molten tin, effectively producing a product of constant thickness with an optically smooth surface. The disadvantage is it bends under weight, and I suspect a tile would distort in the same way. However, I use a sheet of glass for marking out and – supported on a stiffish bench – reckon it's good enough for measuring not too heavy objects within my practical limit, i.e. no better than about 0.02mm (1thou). However, the accuracy is low by real surface plate standards, and wouldn't do if I was working within tolerances. Does anybody on the forum work to tolerances?

On a practical note, I worry that tiles being hard and bendy might make Whitworth's method difficult to apply. Whitworth's plates were made from stiff slabs of cast-iron, which is considerably easier to hand-scrape than a ceramic. I fear a set of 3 tiles would bend and move the blue whilst being compared, so confusing the high and low points. And then, the force needed to scrape a tile seems likely to flex it, again confusing the process. Someone needs to try and report back!

Dave

[Peter Cook 6Participant @petercook6]

Just a thought!

Are the porcelain tiles glazed or unglazed. Unglazed porcelain is fairly soft – probably too soft even for a marking out table. If they are glazed, the hard glaze layer will be fairly thin and rubbing down high spots will potentially break through.

[JasonBModerator @jasonb]

Porcelain tiles are not soft and seldom glazed. You need diamond drills to drill them and if not snapping a diamond saw to cut them.

Sounds like you are thinking of ceramic tiles Peter and Dave which are more like a glazed porcelain cup or plate.

Typical surface flatness of vitrified porcelain tile is within +/- 0.2% of thivkness 

Edited By JasonB on 23/11/2022 13:10:41

[Rod RenshawParticipant @rodrenshaw28584]

Making a surface plate of any size to a reasonable standard by the 3 plate method is said to be a very longwinded, soul destroying and physically hard thing to do. And that's using cast iron.

Many of the posts above make valuable points about the probable unsuitability of a porcelain tile. eg Peter's question about glaze or no glaze. The "glaze" on porcelain is a layer of glass, and it's just too hard to scrape and too thin to "adjust" it's flatness by abrasive means without going through the layer. And if no glaze the tile is too soft.

Some granite tiles and chopping boards are flat enough to make a marking out surface, take a steel rule to the shop and test. Many "Granite" kitchen worktops are moulded or rolled from a mixture of granite particles in a matrix of synthetic resin plastic or similar, and they won't all be hard, flat or stable.

So, my bottom line would be, If I wanted the experience of trying the 3 plate method I would start with cast Iron. If I wanted a marking out table I might try a kitchen shop. Or go to a glazier for a piece of float glass, and support it on a bed of plaster of paris if the work to be done is heavy. If I wanted a surface plate I would buy one.

Rod

[Nicholas FarrParticipant @nicholasfarr14254]

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.

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.

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

Regards Nick.

[Rod RenshawParticipant @rodrenshaw28584]

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

[JellyParticipant @jelly]

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 600×600 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

[BazyleParticipant @bazyle]

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?

[Author]

Posts