New Granite Surface Plate

One of the guys brought a brand new in the box plate to the recent scraping class. We set it on three points at 1/4-1/5 spacings and checked it with an autocollimator/repeat-o-meter, and it was as close to perfect as you could measure in the home shop. Not even a tenth variation.

A note on Selvyt cloths, they must be washed often and by doing so become lint free. washing them you should use one of the soap solutions used for woolens. Mainly used for polishing/cleaning optical lenses and prisms.

A Jeweler will polish gold and silver items with one but he will load it with Jewelers Rouge, this will then retain any gold and over time the cloth can become quite loaded with gold. The cloth is then burned in a crucible and the gold recovered. Remember this is your gold that the jeweler has polished off your gold items.

Clive

Good evening Pete,

Did you measure it when it was not correctly mounted on 3 points? What was the size of the plate?

My Chinese granite tri-square is square to better than I can measure. In that sense it compares favourably with a British made product. However perhaps I got lucky.

As far as I know this is the last UK manufacturer of granite surface plates and standards:

**LINK**

are there others?

Although my overblown sense of civic pride would ensure any tool from eleymet would give me great satisfaction to own and use in practice I agree that there are more affordable good enough quality deals out there.

A little googling has dug up: BS 817:2008 Specification for surface plates, which replaced the BS 817:1988.

If anyone has a copy of either of those for purely educational purposes please do get in touch.

Michael -- I've sent you a PM.

Thanks,

Steve

Edited By SteveI on 19/01/2018 23:48:47

jimmy b I can see you are as happy with this plate as I am mine was also shipped in a box but I discarded it because it smelled of ebola. These granite surface plates wont deform, bend or distort to any degree that will prove problematic, it's just not the characteristics of granite to do so unless they are of a large size and then mishandled. These 450x250x80 plates will be more than stable enough.

Clive Hartland good to see some talk about the selvyt cloth. I am an ex Goldsmith as it happens thanks for the info on washing powder! there are many different selvyt cloths, some impregnated with different polishing compounds and some not. Mine is just a basic soft selvyt cloth, here is a link to the cloth should anybody wish to purchase one: **LINK**. I have many other selvyt cloths which I use to remove polishing compound with cellulose thinners off the brass and aluminium musical instruments I manufacture before I clear lacquer them. I use buffing mops on a polishing motor first with tripoli and blue and red "rouge" for final mirror finishing.

When I was a Goldsmith we used them after polishing, ultrasonic cleaning. We used the cloths only for handling purposes and to remove greasy fingerprints once the polishing process was complete.

I'm far from worried about it moving! I've checked it as best I can with a 2 micron clock, seams perfect. Easily worth the money, (to me!).

My day job is more precise than I will ever get close to at home.

My comment about the plate not indicating its mounting points, was to show that it won't matter. It will have been made simply placed on something. It was only £78 (delivered) after all.

They now show as out of stock, so I'm happier than ever now.

I had kept the box with my previous surface plate, the Axminster one, to keep it covered, but this box was very bad!

Not sure if it smelt the same as yours did James

JIm

I made a cotton cover to try and keep dust off it.

It fits well over the "Trimos" height gauge.

Mrs Jimmyb won't notice the spare bed is missing a sheet for ages ......................

Jim

Some time ago I was doing a lot of work with making cabinet drawers in wood and obtained a piece of plate glass 800mm square and 12mm thick to lay out the drawer sides for glueing.

​ On checking the flatness of the plate I was very surprised to find it was anything but flat. Over the 800mm width it had a bow of at least 1mm. I later discovered that the glass had been toughened and I believe this involves heating the glass in some process, and I suspect this could have caused the warping.

​ A lot of people use plate glass as a surface plate, and a lot of modern glass will have been toughened to make it safer to use and as a result may not be suitable as a good flat surface. Just something to be aware of.

Doug

James I thought Ebola was a virus, how can you smell it?

Dave W

There’s a diagram near the bottom of this page showing how to support a granite surface plate.

It’s not difficult so why do it any other way?

**LINK**

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+1

MichaelG.

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P.S. ... I do like that 'tent' of yours.

Thank you!

Jim

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Edited By Muzzer on 20/01/2018 14:37:54

It was a 600x400 from Insize.

No, we didn't measure it before mounting on 3 pads. The repeat-o-meter was a great tool for checking the flatness of plates and the only one which tested truly flat was the brand new one. All the others checked has some small amount of variation (but they still produced fairly consistent scraping prints).

As far as 'setting it on the points it was ground on'. You're never going to know how it was held, so even if that were a verified true statement it makes for a futile debate.

The smell of the oil reminds me of a story in ME, probably in the 1990s, someone bought a bit of gear from the east, and when he got it home the cat was rather interested in it, it was eventually considered that it was Peanut oil that had become rancid. The oil had been used as a rust inhibiter.

Ian S C

The plate should show the points it was located off. At least on expensive ones....

Jim

Everything bends, it's how much that matters. Where we're talking about here is not something that's enough to matter.

.

Pete,

It's not enough to matter to you ... that's fine.

It may, or may not, matter to me ... that's for me to judge.

It certainly matters to the people who make AA grade surface plates.

MichaelG.

Jim

Without wanting to judge peoples' views one way or another, I have observed over the years that a LOT of companies make a LOT of money selling people things made to higher standards than they actually need.

A factory may need AAA garde measuring equipment in its temperature controlled toolroom, but that doesn't stop some hobbyists (and some small companies) from thinking they need the same in their workshop.

In astronomy I come across people who desperately worry about improving the 'guiding accuracy' of their telescope mounts, despite it already being better than the resolution of their camera/telescope.

Neil

(NOT a dig at Michael because I do think he is able to judge what standard of equipment he needs, rather than wants).