New Granite Surface Plate

[jimmy bParticipant @jimmyb]

It’s a waste of time supporting it “properly” if wasn’t made on them exact locations. Mine is square so I get a one in 4 chance….

Jim

[Michael GilliganParticipant @michaelgilligan61133]

Posted by jimmy b on 20/01/2018 11:29:14:
It's a waste of time supporting it "properly" if wasn't made on them exact locations.

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+1

MichaelG.

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

[jimmy bParticipant @jimmyb]

Posted by Michael Gilligan on 20/01/2018 12:13:15:

Posted by jimmy b on 20/01/2018 11:29:14:
It's a waste of time supporting it "properly" if wasn't made on them exact locations.

.

+1

MichaelG.

.

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

Thank you!

Jim

[MuzzerParticipant @muzzer]

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

[Pete RimmerParticipant @peterimmer30576]

Posted by SteveI on 19/01/2018 23:48:04:

Posted by Pete Rimmer on 19/01/2018 22:55:57:

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.

Good evening Pete,

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

Steve

It was a 600×400 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.

[Ian S CParticipant @iansc]

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

[jimmy bParticipant @jimmyb]

Posted by Pete Rimmer on 20/01/2018 19:09:47:

Posted by SteveI on 19/01/2018 23:48:04:

Posted by Pete Rimmer on 19/01/2018 22:55:57:

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.

Good evening Pete,

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

Steve

It was a 600×400 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 plate should show the points it was located off. At least on expensive ones….

Jim

[Pete RimmerParticipant @peterimmer30576]

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

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Pete Rimmer on 21/01/2018 18:23:57:

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

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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.

[jimmy bParticipant @jimmyb]

Jim

[Neil WyattModerator @neilwyatt]

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).

[Pete RimmerParticipant @peterimmer30576]

Posted by Michael Gilligan on 21/01/2018 18:52:29:

Posted by Pete Rimmer on 21/01/2018 18:23:57:

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.

I won't argue with that. Everyone knows what their own standards are. For some the theoretical problem problem of standing a plate on the airy points is far greater than the practical one.

[Michael GilliganParticipant @michaelgilligan61133]

Pete,

If you're not familiar with it already … You will probably enjoy reading this: **LINK**

https://archive.org/details/whitworthmeasur00whitgoog

MichaelG.

[Pete RimmerParticipant @peterimmer30576]

Thanks Michael I will add that to my book collection. I find lots of great texts on archive.org – far more than I'll ever have time to read but sometimes I do refer to them.

[jimmy bParticipant @jimmyb]

I was talking to a mate yesterday, he's after a surface plate. He tells me that the one I bought is now £106.80, seeing as I paid £78, even happier with it!

 

jim

Edited By jimmy b on 02/02/2018 07:46:20

[Ian S CParticipant @iansc]

Bottom right is a quite nice surface table (Starrat I think), it was bought Govt Surplus in the 1950s (ex RNZAF), cost about NZ 5 pounds, the workshop was Rex Aviation (NZ) ltd at Dunedin in the mid 60s.

Ian S C

[Howard LewisParticipant @howardlewis46836]

Just look at the table on which the surface plate stands! Not a lot of deflection there, if is flat.

5NZ£, What a bargain.!

Howard

[Mark RandParticipant @markrand96270]

Posted by Neil Wyatt on 21/01/2018 19:14:07:

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.

My second hand 36"x48"x6" surface table was a grade 1 when it left Crown's works and also when it was later calibrated in 1998. Trouble is, even ignoring the wear since then, that's worse than the error I need to scrape out of the table on my surface grinder when I start rebuilding it. Luckily, via the gods of the interweb. I've got an autocollimator, mirrors, diamond dust, lapping plates etc. and a workshop that only changes by 2°C per day if I leave the A/C off.

So I have the fun of trying to make a surface table flatter than it is at the moment. I get so much fun out of rebuilding my toys that I sometimes wonder if I'll ever live long enough to make anything with them.

[Author]

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