Stoning mill tables, etc.

hman

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I recall seeing Don Bailey in a couple of Suburban Tool videos lightly using a stone on a machine table before adding the workpiece. This was done to knock off any raised burrs, etc. that might mess up the flatness of the table. I'm wondering ... what's the best type of stone to use for this? And can you use a freshly purchased stone right out of the box, or do you need a surface grinder (which I don't have) to make it flat/usable?
 
They have a video I'm going to go back & watch...
 
As far as I've gathered, what you want is a precision ground stone.
These make sure to only cut down on raised burrs(since you get a stronger contact on the burr than the rest of the table).
Very light pressure need to be used so you can feel through the stone when you're on a burr.
If the stone isn't flat enough it might start cutting into places you don't want.

Can't say much as to what type but I'd rather go with a fine stone as you're not really removing material.

I can't remember where but I remember seeing a guy who used a diamond stone to 'level' a regular stone so he could use it for deburring after scraping, that should work equally well on a mill bed IMHO.

With this said, I've used stones right out of the package and if you're applying very light pressure it seems to work, but not something I would do everytime I move my vice.
 
With respect to all, you don’t need a precision ground stone. While I have researched the topic and a set of them is on the list of “my must have items”, I don’t believe that there is an advantage (over my other stones) to stoning the mill table with them. Primarily I use a hard Arkansas stone with moderate pressure. Diamond stones will cut, so be careful. I have a Trend diamond stone and it cuts really well, so putting it onto the mill table is, in my opinion, a bad idea. I have used Die makers stones and found that they cut into the material so be careful there too. Hard Arkansas is a bit pricey, but you can find it on the popular sites. It lasts forever and does a beautiful job.

Good luck

Derek


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I have always used a hard Arkansas to stone a table, no need to grind or dress them as they are plenty flat enough for the job.

As an apprentice when I was learning to run a Moore Jig Grinder, I was taught to stone the entire table as this will lower the risk of stone a hollow in the table. We would also make setups in a different location around the table to avoid wearing a hollow spot from always setting up in the same area. This would also help to avoid low spots from forming in the machine's ways, again from always using the same area.

Richard
 
I was also taught to lightly rub a stone over the entire surface of a table. I used an arkansas 'black' 'hard' stone, for 27 years on my first mill, and it never scratched or deformed the surface at all - probably after thousands of light stoning operations. The key is to use very light but firm pressure, about the same pressure as holding a cup of coffee, or a little less (around 4 ounces of pressure is perfect)...

With that light pressure, you feel every bump and burr. If you use a super fine stone, you even feel bits of black iron oxide before you can see it with your eyes.

Another pointer for using a stone: use a lubricant. I use a very light machine oil like sewing machine oil, but 3-in-1 is okay, but is a little thicker. If you are going to reoil your table then varsol (especiall the low fumes type) is excellent. This keeps the stone from clogging up and keeps old tacky or greasy oil off your stone.
 
Agreed, don't need precision ground flat stones. I never heard of them until videos of them started popping up on YT. I would like a set but they sure are expensive & I don't own a SG.

People have been using non-PFG stones to stone burrs much longer than I have been alive. I also use Arkansas stones to stone down burrs although mine are probably not true Arkansas stones which I hear have been depleted. I believe mine are the ones made from leftover Arkansas particles or whatever. I have them in both soft & hard.

I also have a pair of 2"x6" Norton India stones that they use to make those PFGs but I pretty much never use them. It is true that they don't come very flat from the factory but I don't use them to stone down burrs on precision surfaces mainly cause they are so big. I prefer to use smaller stones.
 
Many thanks for all the responses. PFG stones do appear to be the "hot setup," but I don't really want to spend that much. I've sent email to two suppliers to ask for quotes on some of their products, plus any words of wisdom they might have. I'll post updates as thing happen.
 
Please do let us know....
 
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