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Precision ground flat stones in UK?

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Diy Addict28/02/2022 10:36:03
25 forum posts
5 photos

I've heard a lot about precision-ground flat stones for removing dings and raised scratches on finely ground flat surfaces without damaging them. But no-one seems to sell them in the UK. I know I could order from the US, but it's a minefield for extra handling & customs charges and delays.

If I've understood correctly, anyone with a decent surface grinder and a fine diamond wheel could make them, but I don't have access to one.

Has anyone tried this approach? If not how do you get around this problem?

Would anyone who has the requisite machinery be prepared to make and sell some? I think there could be quite a few interested buyers.

bernard towers28/02/2022 10:43:45
612 forum posts
109 photos

Couldn’t you use a lapping plate for that?

gerry madden28/02/2022 10:46:24
252 forum posts
132 photos

When I looked at buying some from the US they were eye-wateringly expensive too. Once my J&S 540 is fully restored and tested, flat-stones are one of the first things I will attempt make

Gerry

Andrew Johnston28/02/2022 10:49:10
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6601 forum posts
701 photos

I use a very fine Arkansas stone to remove dings on my milling machine tables, and elsewhere, without damaging the surface. Any professional tool supplier will stock them. Can't see the point in trying to make one.

Andrew

Brian Wood28/02/2022 10:53:51
2566 forum posts
39 photos

You can make your own from readily available stones. You need three of them and some fine sand made into a paste.

Lap 1 and 2 together, then 2 and 3 and finally 3 and 1. Repeat the lapping sequence twice more, wash the stones thoroughly and you will have three precision lapped stones to use as you wish..

It is the same process that gave the world truly flat cast iron surface plates in the early days.

Regards

Brian

Hopper28/02/2022 11:00:46
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6392 forum posts
334 photos

For most practical purposes the as-bought slip stones are all that is needed. They will take burrs and dings off flat surfaces in the workshop just fine, including ground bed ways etc. Providing of course they are used judiciously. Rub the same spot for an hour and it will turn into a hollow of course.

Any precision ground stone is only precision until the first time you use it. Then it's a piece of stone that's been rubbed on a surface and subject to reshaping by that surface.

Unless your intended use is something special?

Mike Poole28/02/2022 11:04:04
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Moderator
3335 forum posts
73 photos

I would think that unless you have the means to maintain a flat stone then it will become just a stone fairly quickly, they seem to be used for rather high quality toolmaking and if you are in that line of work then a surface grinder will be available. It may be more realistic to look for a tool room who use these and see if they could do your stones when they do theirs, I would imagine that a surface grinder will not have a diamond stone mounted all the time and they would set up to do a batch now and again. A poor man’s version could be a sheet of fine wet and dry paper on a surface plate but that would be difficult to handle if you just wanted to check a machine table or indeed the surface plate itself.

Mike

Simon Williams 328/02/2022 11:26:17
654 forum posts
82 photos

I think some of the science of flat stones has got lost.

Not only do the stones have to be flat, but also blunt so they DON'T cut the bed being stoned. They only cut the projections, elsewhere there isn't enough down pressure to get the stone to cut the wider area of the bed.

So the stone floats on a film of oil except where there is a raised ding. This creates a local pressure spot enough to get the stone to cut.

The theory is that a truly flat bed won't suffer local abrasion from having the stone rubbed over it as the stone doesn't contact the surface.

The function of using a grinder to run over the flat surface of a new stones is to knock the aggression out of the abrasion. It doesn't need a diamond wheel to do this, a stone wheel will do the job just fine. A new oilstone as supplied is pretty much flat from new though to get the "floating" effect it needs a dust over to even up the thickness of the oil film against the machine bed being stoned.

I think I recall that Don Bailey of Suburban Tools covers this in detail in one (or more) of his YouTube presentations. Ditto Adam Booth (Abom79).

Rgds Simon

pgk pgk28/02/2022 11:59:40
2563 forum posts
293 photos

Posted by Simon Williams 3 on 28/02/2022 11:26:17:

. A new oilstone as supplied is pretty much flat from new though to get the "floating" effect it needs a dust over to even up the thickness of the oil film against the machine bed being stoned.

I bought a couple of silicone carbide stones with the hope that I could use the fine surfaces as above - but placing one against the other shows a visible gap due to curvature of both stones. Perhaps if they had been older style oilstones I'd have had a go at flycutting them but silicone carbide? Could a holder for a norbide stick work?

Japanese type fine water stones are a consideration.. the small ones I have do seem to be very flat

pgk

Pete Rimmer28/02/2022 12:11:37
1233 forum posts
65 photos

I make them from time to time. Takes a few minutes to grind a normal stone flat on a surface grinder I don't know why they should cost so much extra. I saw some report of high cost due to the wear rate o the CBN wheel but I've gorund perhaps 12 or more and my wheel is still going strong. For sure it does wear the wheel because you can see the material in the grinding dust on the guard but it hasn't been as drastic as folk were making out.

Martin Kyte28/02/2022 12:15:46
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2751 forum posts
48 photos

I bought a couple of SHAH stones last year to experiment with as replacement for Water of Ayr stones. They are nice and gentle and certainly work well on brass. I used water as a lubricant and to wash away the dross. In clock making the stones were used to reduce bushes to the surface level of clock plates and remove scratches. I flattened mine on a diamond whetsone (I have 3 for wood chisels and the like). As to grit sze my estimation by comparison test is somewhere between 20 to 30 micron. They are available on eBay for not much money.

regards Martin

peak428/02/2022 12:24:21
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1712 forum posts
183 photos

For anyone curious, Robrenz has a quite a good video on the subject.

As mentioned above, Don Bailey also covers them very well.
Stefan Gotteswinter, has a video, and also supplies them, but no longer to the UK post Brexit ( It looks like he's struggling to get the base stones at the moment anyway).
https://gtwr.de/precision-benchstones/

Bill

Diy Addict28/02/2022 12:32:23
25 forum posts
5 photos
Posted by Simon Williams 3 on 28/02/2022 11:26:17:

Not only do the stones have to be flat, but also blunt so they DON'T cut the bed being stoned. They only cut the projections, elsewhere there isn't enough down pressure to get the stone to cut the wider area of the bed.

Yes, that's how I understood it. That's why I'm hesitant to get a pair of new stones - presumably they've been ground with a wheel of similar grit. But to properly flatten and smooth the peaks you'd need a much finer wheel.

Diy Addict28/02/2022 12:35:16
25 forum posts
5 photos
Posted by Pete Rimmer on 28/02/2022 12:11:37:

I make them from time to time. Takes a few minutes to grind a normal stone flat on a surface grinder I don't know why they should cost so much extra. I saw some report of high cost due to the wear rate o the CBN wheel but I've gorund perhaps 12 or more and my wheel is still going strong. For sure it does wear the wheel because you can see the material in the grinding dust on the guard but it hasn't been as drastic as folk were making out.

Pete, have pm'd you.

Pete Rimmer28/02/2022 12:36:47
1233 forum posts
65 photos

A truly flat stone is very easy on flat surfaces and tends to only take off high spots anyway. It's the non-flat ones you need to take care with. Lubrication is key if you want to aoid clogging or gouging the stone.

For raised dings you could make a burr file as I was advised to yers ago and it worked. Take a reasonably fine file and rub a stone on the face. Now it will slide over a flat face but cut raised sections down to the face. You might heat and bend the ends up to get good purchase on it when pushing it along a the face but I never did when I made mine.

John P28/02/2022 13:31:28
406 forum posts
257 photos

Here are some flat stones that made some time ago ,as Brian Wood has
said they can be easily formed by rubbing in three's to eventually get to
a flat condition, two of these three i already had but were badly hollowed
the third i bought from a second hand shop in much the same condition.
Using two concrete slabs that are fairly flat to start with and some sharp sand
they can be conditioned to bring them to a flat surface and from
there on the oil stones can be flattened to take out the dips,it is a long
process and best done in short sessions,Final finish using wet and dry
paper on a surface plate with paraffin as a lubricant and then lapping them
together.

You can not get to the same finished edges as described in
Robin Renzetti's video here

https://www.youtube.com/watch?v=DVLXsq7pi9Y

but they work well enough on just plain flat surfaces, not worth doing
if you don't have a surface grinder to finish work in the first place.
Johnflatstones.jpg

Pete Rimmer28/02/2022 15:01:28
1233 forum posts
65 photos

They are most certainly worth having if you do any amount of scraping. You can bring in a scraped surface much more quickly with a very (I'm loathe to use the 'precision' buzzword) flat aggressive stone.

Dave S28/02/2022 17:10:11
367 forum posts
90 photos

I made my scraping deburring stone from a old chunk of dual grit oilstone in an afternoon with a diamond “drone” much like the one Ketan sells. Might even have been one from there, but numerous suppliers have them.

Took an afternoon because this was a well used and consequently quite “hollowed” from axe sharpening.

Dave

Neil Lickfold01/03/2022 08:57:42
860 forum posts
195 photos

I have put a Norton stone on a surface grinder and ground it flat. I was not that impressed by it's lack of cutting. I preferred the cutting of the stones that were lapped or re cut on a flat cast iron plate with fine grit. I rework the stones dry. They work very well. The finer the grit the finer the cutting of the stones to a point. 60 grit from a sandblaster will restore the stone to the sharpness or cutting rate of a near new stone.

Robin01/03/2022 11:21:57
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551 forum posts

So they buy cheapy Chinese stones, give them a quick whizz on the grinder then sell them for hundreds of bucks apiece to dupes who saw their favourite YouTube machinist use one he got for free.

Of course, if they paid the Chinese a bit more they would grind them super flat. They are doing 99.9% of the manufacturing anyway and are much better equipped wink

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