grit size for slip stone

I have a few very minor marks on my mill table that I want to stone flat and was looking on ebay for a suitable slip stone. I soon discovered that there is a range of grit sizes for these stones and am unsure which grit size to pick for the minor remedial work I intend to do.

The most common size seems to be 1000, but 2000, 4000 and 8000 grit sizes are also available. Does anybody have practical experience of particular grit sizes to give me a pointer as to which size to pick.

Doug

Hi,

You've got two or three choices really, an oil stone, which tends to be softer but cuts faster, a water stone, which is harder but cuts slower, or a diamond stone which is probably the most convenient but on the expensive side.

traditionally in the west oil stones were used and you only tended to need a single, double sided stone to do the majority of sharpening. However, some will swear by moving up through all the grades.

The choice will ultimately come down to you but i think somewhere around the mid mark would be good enough for damage repair, if you choose one too fine you'll be there for a long time.

Michael W

Douglas -

My inclination is to go coarser than 1000 grit - you don't want to polish the table, just clear a high spot out of the way. So it is actually a metal removing action, 400 or 600 grit feels about right for me.

Think of it in terms of the grit size of wet or dry paper.

Rgds Simon

These are the ultimate as they will not remove any material off a flat surface - only the high spot , you can buy them but they are not cheap ! I end to use a finer stone (i think around 600 grit and fairly blunt ) to show up any high spots then work locally on any shiny spots that appear .

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

Edited By XD 351 on 27/08/2018 20:06:22

Thanks for the replies, it would appear to be a trade off between speed of metal removal and collateral damage to the area of the table surrounding the ding. I wonder if wet and dry paper with a flat backing would work just as well as a stone.

Doug

Hi Douglas I have always used a Norton IB-24 combination India stone 100mmx25mmx12mm size for rubbing over any mating surfaces like the bottom of a vice or just a rub over the bed of my mill to make sure any lumps are removed. I also have the same stone in a bigger size but rarely use it but it comes useful on larger pieces or pieces with a gap.

David

Edited By David George 1 on 27/08/2018 21:19:45

Removing a raised burr on the machine table or any other metal surface is a two part process for me, first i very gently tap it down with a hammer and a small hardened and ground face steel block, This will push back some of the raised metal rather than grinding it off.

I then use an old well worn dead smooth file with the convex "belly" side against the work, used gently with your finger held directly on the back of the file directly over the burr the file will just cut the high spot leaving the surrounding areas untouched.

I prefer this method to a stone because a stone will remove metal from the entire surface it touches. If I do use a stone it will be as a last step only to blend in the remaining mark.

Regards
John

Edited By John McNamara on 27/08/2018 23:37:44

Have you considered using a small scraper to take the 'hump' off then finish up with a small fine slip stone ?

George.

Yes George I have tried using a scraper but found it difficult to just remove the raised metal without taking too much of the surrounding metal away. Not having had much practise with a scraper probably did not help. I do like John's method of tapping down the burr then stoning, I must give that a try.

Of course the best answer is to prevent the dings in the first place, but with all the care in the world you just can't avoid them completely. I often cringe when looking at some youtube videos where machine tables look like the surface of the moon.


Doug

Plus 1 for John McNamara's method.

With a used file you can go over the whole table surface and the sound it makes will alert you to tiny protuberances that you were not aware of.

'go over' in this case is without applying any force other than that needed to slide the file across the surface.

Ian P