Stoning mill tables, etc.

I don’t stone! That process removes material. I take a large, heavy and flat cast iron object and run it across the table. I’m trying to burnish the high spots, not remove them.
 
I bought a set of the Norton stones to surface grind, they were shaped like a boomerang.
Well, that may be an exaggeration.
Take a straight edge to your stones. Any light coming through?
 
Yeah did that check before I used the ruby stone to fettle. Surprisingly true, for the price - but then again, these are synthetic stones, presumably sintered synthetic ruby, so probably come pretty true straight out of the press.

While we're talking' stones, has anyone used the Shapton glass stones? Japanese, ceramic bonded to a glass base.

As for burnishing vs stoning: yeah, stoning removes metal, specifically the metal that sticks up. I could stone that table every hour until I die and there would still be plenty of metal atop the T-slots.
 
I could see stoning a table maybe once per new owner but what are you doing to your table that requires frequent stoning? As fas as i can tell, wiping removes everything that could affect results.
 
I think the idea is that you may kick up a burr when mounting something heavy like the vise or a rotary table. That makes it advisable to stone the table when removing one of these, which usually coincides with mounting a different one. if you use tooling plates, or if you never remove the vise from the table, then stoning is going to be a very rare activity.
 
Take a look at Shark River Machine sharkrivermachine@gmail.com, Steve is a great guy and I will be placing an order for my stones from him.

4”x 1 ¾: x 5/8” ground on 4 sides Made in the USA they run $125.00 per pair shipped in the USA.
6”x2”x1” run $160.00 per pair shipped in the USA.
4” round x 1” thick and they run $180.00 per pair shipped in the USA.

The reason you use two is to maintain the flatness of the stones. Just like any other precision tool we have, as they are used and these are not hard steel, they can wear from hitting burrs, excessive pressure, edged of work piece etc. You rub them together before use to ensure maintain the finish. Also, is is good to clean them periodically to remove the dirt and debris that builds up.

As for the need for precision stones, Steve uses Norton stones. If you look up the 6"x2"x1" stones, they run $42 each. Then he precision grinds them. The added cost of $38 each seems very small compared to what we spend on our hobbies.

It is no different than would you buy a HF dial indicator or a Starrett?
 
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The best machinist I know would laugh at the idea of harming a mill table by stoning. He uses whatever stone he grabs first and uses it daily. Most often it's the flat side of a round 8" grinding wheel with the label removed. He vacuums the T-slots, runs the stone once over the table in a circular motion, wipes it with an oily rag and then does more work in a day than most of us do in a month.

jack vines
 
Quick update - I bought the Grainger 6160A41 2"x4" hard Arkansas and medium Arkansas stone, $32.16 + shipping. See earlier post. Flattened/conditioned it a bit by rubbing on a very fine 2x8 diamond plate. Very nice feel on the mill table; no scuff marks produced. Did learn something about oil - way oil is way too thick! Some relatively thin "honing oil" from sharpening kit worked very nicely.

Thanks again to all who've responded!
 
Like Packard Jack says - I can't see a little thoughtful stoning harming a mill table. I just use a regular 2x8 oil carbrundum (dark grey) stone every once in a while. I do the entire table - I really, really doubt the table is getting all wavy because I'm taking so much metal off.

The precision ground stones are great for cleaning/deburring gauge blocks and any serious precision items (perhaps depth mic bases, precision squares, sine plate, your special set of 123 blocks) - places where part of a tenth would matter.

On a mill table - I suggest there would be any number of other issues that are more significant than what type of stone is used on the surface. Things such as how well the slides are looked after, if they are worn in spite of good care, table distortion because of how it is loaded (which can become permanent) etc. are a bigger issue than using whether I do/don't use a PGS stone.

I suggest using PGS stones for mill table care is an example of an overblown concern. Keep the machine clean, properly serviced, don't drop things on the table (or otherwise abuse the machine) and the mill will provide great service for many years.
 
@Chipper5783 - please never make the mistake of taking any stone to a gauge block. Once, and only once and the gauge block is ruined.

On a surface grinder magnetic chuck you can ONLY use a PGS. I would never stone a precision square or depth mic base.

-- if anyone can afford it, and has that option, a PGS is desirable to any other stone for taking burrs off any flat suface (with the above exceptions)
 
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