Granite Surface Plates, etc.

[IdahoMan]

Hi,

I am looking for high-quality, but not ridiculously priced, precision tools. Preferably certified.

For starters I'm thinking:

Grade-A Granite Surface Plate (18x24)
Straight-edge (12")
Straight-edge (24")


Thread rules: No Starrett or Snap-On please.

 

[dagofast]

I've used both of these companies with good success. http://www.standridgegranite.com And http://www.precisiongraniteusa.com

They are both in Sante Fe Springs, CA So shipping to Idaho wouldn't be horrible.

A company I used to work for was also headquartered there. I still have a little 30"x12"x3" Grade A plate from Precision Granite.

 

[tool_scrounge]

This is where I miss Enco and their 20% off and free shipping specials

 

[vavet]

Is your handle indicative of your location? Are you truly in Idaho? I have a pink granite surface plate at work that needs a new home, but shipping would be cost prohibitive...and I think it also violates the thread rules.

 

[IdahoMan]

Is your handle indicative of your location? Are you truly in Idaho? I have a pink granite surface plate at work that needs a new home, but shipping would be cost prohibitive...and I think it also violates the thread rules.

Nice, Virginia. And yes, I am in Idaho. S&H would be a problem. lol.

As for the thread rules, if your plate was new-priced then yes it would violate the thread rules.

 

[dr_clyde]

Surface plates are CHEAP at auctions and surplus houses, their value drops like a rock (haha) when used.

You can have used plates lapped and re-calibrated in your facility.

If you want new and don’t want Starrett, I’d get Standridge.

As far as straight edges, are you wanting rulers or like, camelback scraping reference edges? There are lots of different kinds. Regular rules and scales, flex rules, combination square blades, and several other uncommon styles.

I don’t know why you wouldn’t want Starrett for metal straight edges, they are the best. But if you really don’t want them, I have some Mitutoyo, Brown and Sharpe and Products Engineering rules that are nice quality. They key here is satin chrome. Whatever you get, get satin chrome finish.

 

[Steve_P]

I have an older Enco granite plate and a Central Tool (not HF) machined straight edge. Both are beyond good enough for home use

 

[Indexmill]

Ah, the days of Enco...

 

[IndyGarage]

I have a 48 x 48 surface plate I'd like to get rid of. It's a big heavy flat rock.

 

[bugnut]

As Steve P stated "I have an older Enco granite plate and a Central Tool (not HF) machined straight edge. Both are beyond good enough for home use "

A scrap piece of granite/stone from a busted or discarded kitchen counter and a good piece or precision ground tool steel from a general supplier is more than adequate for the home machinist.

 

[IdahoMan]

Surface plates are CHEAP at auctions and surplus houses, their value drops like a rock (haha) when used.

You can have used plates lapped and re-calibrated in your facility.

This was a route I was thinking of taking (I tried e-mailing a couple of local machine shops for leads. They didn't get back to me. ), but would it cost more than new to have a company come to my home and re-calibrate/certify a worn/out-of-spec plate? Also, does having it certified magically make the price jump dramatically?

If you want new and don’t want Starrett, I’d get Standridge.

As far as straight edges, are you wanting rulers or like, camelback scraping reference edges? There are lots of different kinds. Regular rules and scales, flex rules, combination square blades, and several other uncommon styles.

I have some rules, but how straight are their edges guaranteed to be? The accuracy of all things in my shop will depend on these precision, metrological tools I am asking about: Straight-edges, cylindrical squares, surface plates, gauge-blocks, etc..

I don’t know why you wouldn’t want Starrett for metal straight edges, they are the best.

I like Starrett and I understand they are the best out there, but I can't justify their prices.

 

[Stuart in MN]

Grizzly Tools has a selection of granite surface plates for reasonable prices, but they are grade B. Looking online it appears there's a big jump in price if you want a grade A.

 

[Downwindtracker 2]

Those that know more than I, say Grade Bs are adequate , as for the straight edges , those you will have to scrape yourself., even used ones are out. Depends on how they are hung them.

 

[rlitman]

...A scrap piece of granite/stone from a busted or discarded kitchen counter and a good piece or precision ground tool steel from a general supplier is more than adequate for the home machinist.

The precision ground tool steel blank may indeed be acceptably straight, but you'd be surprised how much waviness you can find in a stone kitchen countertop.

At least if you're going to go that route, pick a piece of stone that has no striations in it.

But for a small area, a thick piece of glass from a tabletop is probably flatter.

For my own purposes, my blanchard ground tablesaw top is acceptable. I have a Starrett pink surface plate, but really don't use it for it's intended purpose.

 

[MoonRise]

OP,

Do you really have a temperature and humidity controlled metrology room, maintaining 68-72 F and 40% RH and air filtration to remove dust and such from the air? With no sunlight shining on it (thermal differential again)?

If not, then you probably don't 'need' an A (lab grade) or AA grade (inspection grade) surface plate and a B-grade (tool room grade) plate will probably be 'enough'.

Then you need the actual stand for it. The one with the 'correct' three point mounting/support arrangement for the surface plate. No, you can't just plop a precision surface plate on top of your 2x workbench and still expect or get 'precision' from said surface plate. The stand in the 'smaller' sizes is about the same price as the surface plate itself.

No affiliation or endorsement for or against, just a quick web find. 18 x 24 x 3 surface plate, with optional stand available. Grade A is $36 more than Grade B for this one, the 95 lb stationary stand is $407.

https://cnc-specialty-store.com/mea...ranite-surface-plate-18-x-24-x-3-grade-a-or-b

Brief article about surface plates:

https://www.qualitydigest.com/aug03/articles/03_article.shtml

 

[matt_i]

If you get a good surface plate you can scrape (learn to scrape) a cast iron straightedge as good as the plate is. Just saying in the absence of any other precision devices it takes a set of 3 cast iron surface plates which are printed against each other and scraped into the best possible match in a set of tiring iterations, when the print is matched across the set then they are as flat as can be done.

In modern days light-based devices for inspection are used which are less work They identify areas of the granite which are "high" and need to be lapped down in a similar iterative process.

What is the exact intended use here?

It does set a flag when looking to calibrate a surface plate but not wanting to find the highest possible starting point because of initial cost. Most granite surface plates, in "whatever" condition are good enough for the home shop user as long as there aren't obvious visual pocks out of the surface.

 

[rlitman]

My metrology room is climate controlled. It matches the temperature of the local climate.

About the stand. I can't speak for others, but my Starrett came with three feet mounted on the underside. So long as these three feet are on a level surface, I don't see how any stand would improve its performance. Now if you just have a polished piece of rock, then yeah, you'd need a 3 point suspension, but I'm not even sure how you'd locate these points yourself if they're not marked by the manufacturer.

 

[matt_i]

but I'm not even sure how you'd locate these points yourself if they're not marked by the manufacturer.

If the feet are off, the Airy Points for minimum deflection of the plate surface under its own weight are best approximated by a 1/3-1/3-1/3 grid arrangement, obviously the single foot has to be on the centerline. But the rock is pretty stiff stuff. Most people without the tools to inspect the surface plate couldn't tell if it was slapped down on a couple of sawhorses.

 

[dr_clyde]

Good precision tools are very much a "pay to play" arena.

Pretty much anything will do for a home shop, but if you want nice tools brand new, you're gonna have to pay the piper.

Starrett isn't much different than most other makers price wise, they're just the most well known. Brown and Sharpe, Mahr-Federal, Interapid, Mitutoyo, Scherr-Tumico, Helios-Preisser and Lufkin are all in my box, and they are just as expensive as Starrett if not more.

I find Mitutoyo gear to be the best balance between price and quality. Not cheap, but not outrageous. Sill very nice quality.

As far as surface plates, you really don't need anything more than a grade B for general shop use.

Challenge, Rock of Ages, DoAll, and lots and lots of others made surface plates, they go for almost nothing at auction around here. A local machinery dealer made a patio out of them he had so many.

 

[PugetDude]

I've used a small 3" Toolroom Grade Surface Plate from Grizzly for the last 10 years.
(home hobby machining only) At my level of precision it's more that adequate.

OP, what are you going to be using this for? Big difference between home use and high-precision lab work.

 

[MushCreek]

I'm curious what you're going to use it for. I've worked on plastic injection molds with tolerances down to .0001", and B-grade plates are generally fine. You only need a super accurate plate for stuff that is both big and accurate.

 

[mowkep]

We got ours, years ago, at Enco. There should be plenty of used machine tool dealers in your vicinity. They sell a plethora of different tooling, machines,...etc

 

[IdahoMan]

Here's what I imagine my uses will be:

Checking tools (ex: squares, straightedges, parts, etc.) before I use them.
Using surface/height gauges, layout work.
Metrology curiosity.

I don't think I would like to use one with sandpaper for sharpening things like wood-planes and chisels. A scrap piece of granite will do.


Disclaimer: I am not a machinist, this is for home shop use. Basically just need a trustworthy reference.

 

[MoonRise]

Not a 'machinist' and just "for home shop use"?

Grade B (tool room grade) should be just fine.

(remember that the overall flatness tolerance for a Grade B surface plate of 18x24 inches is 320 MICRO inches, or 0.00032 inches)

3 ten-thousandths of an inch is still a pretty small dimension (for anything other than precision machining or optical type things).

And the 'local' flatness tolerance for that size Grade B plate is half of that number, or 1.6 ten-thousandths of an inch.

That roughly 40x smaller than the diameter of a human hair. RCH not included.

 

[PugetDude]

Here's what I imagine my uses will be:

Checking tools (ex: squares, straightedges, parts, etc.) before I use them.
Using surface/height gauges, layout work.
Metrology curiosity.

I don't think I would like to use one with sandpaper for sharpening things like wood-planes and chisels. A scrap piece of granite will do.


Disclaimer: I am not a machinist, this is for home shop use. Basically just need a trustworthy reference.

Here's an 18x24x3 Grade B plate for under a hundred bucks delivered to your door.

https://www.ebay.com/i/350268478822...zw4cXeCusHbd__qCS-6UtVrlopSbktjxoCFxcQAvD_BwE

 

[MushCreek]

In some ways, a new B plate might be better than a used, non-certified A. If plates are used a lot, they tend to get low spots where they are used a lot. I worked on extremely precise molds, and we used to have the plates checked and lapped every year. The last place I worked at abused their plates, they were heavily used in one area, and hadn't been checked in 10 (?) years!

If you're going to be doing that sort of precision inspection, you're going to need a GOOD dial test indicator that reads in .0001". I've been using a Brown & Sharpe indicator professionally for about 30 years.

 

[PugetDude]

OP, too bad you're not closer. I just ripped out a 24"x45" 3CM black granite countertop. Would probably be more than adequate for your requirements.

 

[Whitworth]

Here's what I imagine my uses will be:

Checking tools (ex: squares, straightedges, parts, etc.) before I use them.
Using surface/height gauges, layout work.
Metrology curiosity.

I don't think I would like to use one with sandpaper for sharpening things like wood-planes and chisels. A scrap piece of granite will do.


Disclaimer: I am not a machinist, this is for home shop use. Basically just need a trustworthy reference.

The machined flat bed of a jointer would be sufficient for all the above.

I have two surface plates, 12 by 12 and 18 by 24. The small one I use occasionally for lapping, the other never gets used. For home shop use they'll gather dust.

 

[Marctrees]

If the feet are off, the Airy Points for minimum deflection of the plate surface under its own weight are best approximated by a 1/3-1/3-1/3 grid arrangement, obviously the single foot has to be on the centerline. But the rock is pretty stiff stuff. Most people without the tools to inspect the surface plate couldn't tell if it was slapped down on a couple of sawhorses.

Interesting read link.

Marc


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

 

[sberry]

The machined flat bed of a jointer would be sufficient for all the above.

I have two surface plates, 12 by 12 and 18 by 24. The small one I use occasionally for lapping, the other never gets used. For home shop use they'll gather dust.

I go with this.

 

[Marctrees]

somekinda Glass would be flat enough ?

could be almost free, second hand.

Dunno, just asking.

Marc