Grit comparison to waterstones, a bit long

Re: Grit comparison to waterstones, a bit long

steve knight

>what your seeing is the result of two different abrisives. most waterstones of the lower git don't make the steel look shiny. sandpaper tends to do it more then stones do.

so don't worry about it.

Re: Grit comparison to waterstones, a bit long

joel

>The problem is you are comaring apples and oranges.

When you buy anything at a particular grit you are getting an abrasive than depending on manufacture, chemistry, etc has a particular average grit size, a typical sharness to the grit, a typical resistance to being pulverized, a typical wear pattern, and finally in the case of waterstones in particular - a friability which means in this case how long the abrasve will last before it's replace by sharper, larger abrasives.

A few examples - Typicial wet or dry sandpaper has a fairly weak adhesive holding it to the paper, and isn't grated very carefully. So wehn you use it the larger chunks of abrasive do most of the work, and they wear off the backing and break sonner. Others have also commented on how SC vs AO pulverize with wear differently.

Lapping film on the other hand will be much tigher in spec on the grits so more of the grit will get used, so it will cut faster and smoother, and it has typcially a stronger bond with the film backing so it lasts longer.

SC powder on the other hand is getting crushed to a fine paste as you use it and there is a lot more total abrasive than a single sheet of lapping film.

THe waterstone on the other hand (foot I'm out of hands) is intentially friable so as the grit wears it is washed away and is replaced by new larger grits below it on the stone.

So depending on the material you get different cutting characteristics and polishing.

And in addition Japanese grit sizes are different than the US and even Japanese factories have tighter or looser specs depending on the stone and how they want to market it.

SO all bets are off.

Incidently what you can do is after you are basically done with a grit on a waterstone let the surface of the stone start to dry out. THis will keep the finer, pulverized adbrasive paste on the stone to leave a finer polish instead of being washed away.

a bit more information

bill tindall

>To elaborate some on what Joel already stated.......

The finish(appearance), as well as sharpness, will depend largely on the depth of the scratches. The depth of scratches will depend on the size, hardness, and shape of the abrasive grain, how the abrasive grain wears, hardness of the abrasive grain binder and grinding pressure, So you can see that the grit size is only part of the story. And, there are a variety of conventions for describing abrasive grain sizes such that grit 500 in one convention will be a different size in another convention.

Silicon carbide is very hard and this property would suggest that it could be good for grinding very hard tool steels. However, it is also very brittle, so that it is easily crushed by moderate grinding pressure. I suspect that the better apparent finish your are observing with the loose silicon carbide is a result of the silicon particles crushing to yield a finer abrasive than the original.

If you are going to use loose silicon carbide, charge it onto something flatter, harder and more durable than paper. The substrate requirement is that the particles must embed such that the abrasive is relatively fixed while the tool slides across it. I have not tried all these substrates but you might investigate any sort of plastic sheet (Plexiglas, Mylar, Lexan), aluminium or even wood or MDF. Any of these choices will be better than paper. Silicon carbide lapping compound (Clovite) is available from any machine shop supply in grits as fine as you could possibly want to go. Having been hooked on this cheap, fast way to sharpen you will soon want to move on to diamond lapping compound to take advantage of its even cheaper and faster attributes.

Re: Grit comparison to waterstones, a bit long

Alan Womack

>Robin Lee's sharpening book has approxiamate tables.

To hijack a thread, what's a good method to flatten a flattening stone? I bought two ice bear stones which are WAY out of flat themselves. 180 grit wet dry has about 1.5 hours in it, so I tried a 80 grit CZ belt sander belt, that curled.

Then I bought a 3M brand 80 grit wet which made it about 5 minutes and completely feel apart. The water destroyed it which is odd for a wet/dry paper.

Thinking of buying some lapidary supply powder and trying it on some glass.

Alan

Re: Grit comparison to waterstones, a bit long

Bill Lowrance in Geneva

>Could micro-burnishing explain the differences in the apparent shininess one sometimes sees with roughly equivalent grits?

Lexan

Bob Hackett

>In an effeort to find a better(faster)way to flatten chisels and plane irons I tried charging a 3/4" thick Lexan plate with 14 micron diamond paste.It cut very well for about 15 minutes.I charged it again and got another 15 minutes from it before the cutting action tapered off.After recharging a third time with the same results I am less than impressed with Lexan as a substrate.The diamond stays in place it just seems that Lexan is too soft and allows the diamond to sink in further and further till it stops cutting.

How about sharing your thoughts on Acrylic Bill.I remember you mentioned some research using it as a sustrate for diamond powder.

Also I have heard some folks recommend 30 micron diamond as a good place to start flattening,how about some guidance on initial grit size?Thanks.

Mainely,Bob

Re: Grit comparison to waterstones, a bit long

Gil

>Try the sidewalk in front of your shop. There was a thread on this a while back I believe.

-Gil

Re: Grit size equivalents *LINK*

paul womack

>However. as well discussed by Joel, grit size is not the whole story.

BugBear


http://users.ameritech.net/knives/grits.htm