Granite Surface Plates For A Hobbyist's Shop

[Pylonracer]

From what I can tell the need for a surface plate all depends on the parts you are building and the the precision you need. For the parts I build I don't need a surface plate and have passed on some of the used ones I have found for sale.

If I was more into machining my own fixtures and accessories I could see how I would need a decent surface plate since measuring errors have a way of telegraphing and multiplying through the parts made on those fixtures and accessories. From what I can tell this path kind of inevitably leads to a surface grinder.

Well a surface table is used in an ideal World even for the most basic marking and scribing requirements, such as marking off an item whilst it is held up against an angle plate that is sat on the surface table, I was doing this in trade school in the 1970's, right through to complex measurements on jigs and fixtures.

Once you have one, you wonder how you got by before, well at least that is my experience.

 

[bulgie]

Once you have one, you wonder how you got by before, well at least that is my experience.

Conversely, I had one at work for years and used it plenty, but that was 35 years ago. As a retired hobbyist with little space to spare, I've never been tempted to buy one. But I don't make anything that takes high precision.

 

[GT-6 Racer]

I think that every hobbyist should have at least small plate for setup and measurements. Cheap ones from Shars, Grizzley etc. are readily available and are perfectly adequate for home shop use to a few tenths. Check this one out:

9" x 12" x 3" Granite Surface Plate, 2 Ledges

This tool room grade "B" Granite Plate has a bilateral accuracy of plus or minus .0001" total instrument runout for precision measurements from a common surface base. Granite Plates are harder than steel, non magnetic, least responsive to temperature changes, practically maintenance free and...

www.grizzly.com

For commercial work one should up the quality level a bit and at least self-calibrate local flatness. I have gathered a selection of surface plates over the years from small cast iron 12x12" and 18x18" which are great for use with magnetic base indicators and carrying to a machine for checking flatness on big stuff. A 24x18" granite plate sits on the main workbench. Its beat up but flat and was $50. used for less critical measurements, general setup and a clean place to write . A black grade A Collins Microflat 24x24" by the grinders for precision measurements and setting sine vices etc. And lastly a 24x36x6" Starrett pink granite plate for scraping and high precision work. May seem like overkill but they all have their purpose and all were bought used and super cheap at auctions or off Facebook. If you have the room the larger plates are usually pretty cheap (or prohibitively expensive, seems to go either way at auctions). I couldn't imagine not having at least one of the medium sized granite plates for general day to day work.

Just be careful and measure before you buy. There's lots of information on how to measure with a surface gage and a tenths indicator. Before you know it you will be building a Repeat-O-Meter... Big shout out to John Saunders here.

and Robin Renzetti here.

And Kieth Rucker here

Great info on measuring and lapping those used plates.
The metrology bug is a dangerous one, but a lot of fun.

 

[Dabbler]

if all you need a SP for is to do layouts with height or scratch gauge. then a float glass lapping plate is just fine. Layout lines can be +/- 3 thou or so, and it won't matter that much.

For accurately checking roundness of shafts, checking surface ground parts, etc, an inexpensive granite surface plate is way better.

 

[Advil]

I picked up a small grade A from Amazon for a specific job years ago. They still carry them. I don't know why.

The plate was surprisingly good. I think it was $70 or so at the time... shipped free. Which is absurd. The shipping has got to cost them more than the entire value of the plate. The UPS guy had to hand truck it in and I helped him move it the whole way from his truck so it didn't get dumped and broken. We both got a laugh out of it. He was like "What the hell's in there a rock?" I said, "Yes. Exactly." He couldn't believe they would send granite like that for that price.

 

[SouthernChap]

View attachment 488635

I was considering the Dasqua digital mic' but I managed to get Mitutoyo 0-25mm/0-1" and 25-50mm/1-2" combi-mikes off eBay in tidy condition.

I do have a pair of the Dasqua 25-50-75 blocks, which seem pretty spot on.

I also have one of their machinist levels but it didn't come with any instructions about how to calibrate the thing so I haven't used it yet.

 

[SouthernChap]

From what I can tell the need for a surface plate all depends on the parts you are building and the the precision you need. For the parts I build I don't need a surface plate and have passed on some of the used ones I have found for sale.

If I was more into machining my own fixtures and accessories I could see how I would need a decent surface plate since measuring errors have a way of telegraphing and multiplying through the parts made on those fixtures and accessories. From what I can tell this path kind of inevitably leads to a surface grinder.

I'm still doing some tidying and upgrading of my little Chinese 7x so that's what it would be helping with initially.

 

[verbotenwhisky]

I was considering the Dasqua digital mic' but I managed to get Mitutoyo 0-25mm/0-1" and 25-50mm/1-2" combi-mikes off eBay in tidy condition.

I do have a pair of the Dasqua 25-50-75 blocks, which seem pretty spot on.

I also have one of their machinist levels but it didn't come with any instructions about how to calibrate the thing so I haven't used it yet.

I have an Accusize Machinist level, they are not difficult. ABOM79 has a couple of videos explaining how to calibrate and use these.

 

[SouthernChap]

I have an Accusize Machinist level, they are not difficult. ABOM79 has a couple of videos explaining how to calibrate and use these.

Cheers, I just thought it might have been nice if it actually had come with a teensy bit of paper telling me which screws to turn and which way to turn them!

I'll take a look at the scary man's videos and see what I can figure out.

 

[verbotenwhisky]

Cheers, I just thought it might have been nice if it actually had come with a teensy bit of paper telling me which screws to turn and which way to turn them!

I'll take a look at the scary man's videos and see what I can figure out.

I understand.

LOL, the scary man?