Doing finish work on granite plate .....

[toolznthings]

Hi All,

A easy way to get a nice finish on parts or establish a flat surface is to use a granite plate and self adhesive " Stick & Sand " papers for palm sanders used in the wood shop. The above is a Norton product, but there are many other brands.
Shown is a small 9" x 12" plate with the paper attached to the granite so I can remove mill marks on my next upcoming engine project. Inexpensive granite plates are just about everywhere these days so no need to use the one for layout work and inspection. I have the granite on rubber matting so it will not move when moving the part back and forth on the abrasive.

[RayW]

A handy hint and one which I have employed using a sheet of plate glass and double sided tape to secure the sandpaper.
By pure coincidence, I was passing a stonemasons works today and noticed a pile of offcuts of polished granite and marble on a pallet outside so made enquiries as to whether any would be available. The lady in the office said that it was already spoken for as it all goes to a local farmer who uses it for hardcore!! When I explained that I was looking for a small piece to use as a surface plate, she very kindly let me take the piece shown in the photo. It is about 14 inches by 12 and just over an inch thick, and whilst it is a bit of an irregular shape that doesn't worry me.

[Vixen]

I bought part of a 2 inch thick black granite headstone from the local monumental mason, some years ago. The front surface is polished to a mirror finish and dead flat.

When I am finished using it has a surface plate, the family can engrave my name and dates and use it for the purpose originally interned.

Waste not want not.  A surface plate as a headstone, very fitting for an engineer.

Mike

[Admiral_dk]

Waste not want not.  A surface plate as a headstone, very fitting for an engineer.]Waste not want not.  A surface plate as a headstone, very fitting for an engineer.

Amen to that - especially if he is an mechanical engineer (there is other types that never did anything mechanical - though I should be careful here, as an engineer in Danish equals a master degree in English).

Have to agree that the gravestone shop is a source I haven't thought about - so thank you to toolznthings for that tip 

[wagnmkr]

Another source for polished granite ... counter top companies ... they all have an "oops" pile in the yard and I was told to take what I wanted.

Cheers

Tom

[Mathew28]

You can find polishing pads on eBay and diamond shapping cutters and they fit on a 5" grinder but make sure it's one you can change the speed.
Mathew

[Tennessee Whiskey]

+1 to what Tom said.  Granite counter tops are all the rage these days and have become somewhat affordable.  The cutouts for sinks and the odd drop to make a piece fit is most usually going to be trashed and if one is at the right place at the right time,  a decent surface (or lapping ) plate can be had . I actually have a pretty good size stack left over from the counter redo at the store. 

Cletus

[zeeprogrammer]

I'm interested in this. There's a couple of granite companies not far from me.
Are they really polished/shaped to that kind of tolerance to use as a sanding plate?
If so...I'm heading down there.
Could use some new friends. 

[Tennessee Whiskey]

They aren't lab quality, but, they are " close enuf " for what we do

Cletus

[Tennessee Whiskey]

Here is a shot of the counter at the pool bar. You can see the reflection of the Bud Light neon



Cletus

[b.lindsey]

I don't see any Cheerwine in that fridge Cletus. Maybe it hasn't spread over to Springbucket yet

Bill

[derekwarner]

At my place of employment many years ago  we had a largish Italian marble surface plate [approx. 3m x 5m] for re-assembly measurement of largish missile launcher components...... naturally it lived at a constant 22 20 degrees C & 16 % humidity..........the surface flatness was measured in uM [microns]

The directions  were quite clear.....it was very cold to walk on   as one had to wear those synthetic sterile bootlets over cotton socks over bare feet as worn in hospital theatres..& no  on the job.......Derek 

[b.lindsey]

That would have been a monster to lift Derek. For that large a surface area, what kind of supports did it have? Without adequate support I would think it could sag more than a few microns....just curious.

Bill

[Tennessee Whiskey]

One of the YouTube guys did a field trip to Standridge Granite. Very informative. I think all of their plates were set on a three point suspension, no matter how large.

Cletus

[steam guy willy]

I all ways work to microns...............there may be a large number of decimal points involved ...but they are still microns!!!!

[derekwarner]

Bill....from memory the slab was ~~ 700mm thick...so a auto calculation suggests ~~ 28000 kg [28 tonne]...the slab was lifted and installed with the aid of a 200 tonne crane

The support mechanism was based on an American military standard [MIL Spec] with multiple hydraulic load cells firstly confirming even force loading, then during each critical measurement the slab was elevated by the same load cells with load sensing software under a surprisingly low hydraulic pressure of 2000 PSI [or ~~130 Bar]

Placing a say 250 kg component on the slab did not register as any form of angular displacement measurable by any equipment available in the Naval Dockyard facility

BTW...I have corrected the controlled temperature ...it was the standard 20 degrees C

Derek

[zeeprogrammer]

I all ways work to microns...............there may be a large number of decimal points involved ...but they are still microns!!!!

 

My dimensions have the letter E (or e) in them.

[b.lindsey]

Thanks for the info Derek. That would have been fascinating to see. Here at the UNCC metrology lab with sophisticated nano scale instruments, the new building that houses the lab was in some ways designed around the lab...a separate isolated floor slab for example, and if memory serves they even took seismic measurements to determine the typical activity at various times of the day depending on interstate and railroad track activity even if a half mile or more away from the building itself. I think the HVAC system is capable of holding +/- .1 degree C 24/7.  Defnintely not your typical hobby set-up but you have to admire the technology involved in making those kinds of measurements. 

I would love to see pictures of the surface plate you describe....gosh...what a monster!!

Bill

[Dave Otto]

At my place of employment many years ago  we had a largish Italian marble surface plate [approx. 3m x 5m] for re-assembly measurement of largish missile launcher components...... naturally it lived at a constant 22 20 degrees C & 16 % humidity..........the surface flatness was measured in uM [microns]

The directions  were quite clear.....it was very cold to walk on   as one had to wear those synthetic sterile bootlets over cotton socks over bare feet as worn in hospital theatres..& no  on the job.......Derek

Do ya think they would have minded if you used it to lap your model steam engine parts on? 

I'm with Brian, I have a small Granite plate that gets used mostly for lapping parts on wet or dry sand paper. I have a small one on my bench at work for the same thing.

Dave

[petertha]

I have yet to buy a granite plate for measuring, but its on the acquisition list. I have 2 plates of glass 1 foot square x .25" thick which I tape 2 grades of wet/dry paper around the periphery just using masking tape (for example 320 & 600). Works great for finishing parts & my favorite lube is a spritz of WD40. That's what I use them for. But I'm curious, has anyone measured across a typical glass plate with DTI to see how much it deviates? Guessing to measure it properly you would need to lay the glass on the granite... so with granite you probably wouldn't have glass to begin with.. one of those chicken & egg things

[steamer]

If you have a cheap Chinese plate ( or tomb stone)  and can stand the space to store it....its fine

A nice Starrett Pink plate to 50 millionths......WE are going to have a conversation....just sayin....

A piece of countertop or sheet glass would be a better choice and less expensive .....

I used to do that on the table saw......kept the rust off..

Dave

[toolznthings]

I guess my real point was the use of the " stick and sand " papers on whatever surface you choose. Does not need to be a granite plate.

Brian

[steamer]

I guess my real point was the use of the " stick and sand " papers on whatever surface you choose. Does not need to be a granite plate.

Brian

YUP.....but try not to do this on a NICE surface plate hmmm?     Please?

Sorry....I've done too much scraping to have my surface plates un-necessary accuracy ameliorated by crocus cloth and elbow grease...

Table saws work great for that!!!!

[ShopShoe]

FWIW,

Tom Lipton ("Oxtoolco" on youtube) has a video showing his surface plates being reconditioned. The one he uses for sanding does show some wear. A very interesting process to watch. Find it by searching on youtube for "Surface Plate Calibration and Conditioning."

As a hobbyist, I don't get too worried, but I use my surface plates (Grizzly Specials) for layout and measuresment and testing and do sanding on other surfaces. Mostly I try to keep the granite plates (and the tools I use on them) as clean as I can.

BTW,

For ultra-precision geeks, the videos posted by Suburban Tool also get one thinking about ways to be more precise in every way.

https://www.youtube.com/user/SuburbanToolInc

Sorry if this post is too much off-topic

ShopShoe

[Sackett]

Off topic,but I gotta agree with b.linsey,,,if you're running a fridge , n it aint got Cheerwine in it ,you're wasti 'lectric

[b.lindsey]

I am surprised it has made it up to WV Sackett. I wasn't sure it had spread beyond the Carolinas to be honest. I am a sweet tea guy myself but Cheerwine is the only soda I will drink Maybe Cletus doesn't know what he's missing!!

Bill