Resurfacing benchstones

[copper_head]

heh all,
Got myself an arkansa tri stone from knifeart.com a few years back. great set of stones but has now got a couple of chips in it and has started to bow, mr Mears says you can regrind a flat surface with a pane of glass, washing up liquid and something called 'piston carbondrum grinding paste' any ideas what this stuff is and where i can aquire it? cheers

 

[beach bum]

I think you'll find that's valve grinding paste you should be able to get from any motor factors. Years since I've used any (on valves) used to come in a double ended tin with fine in one end and coarse in the other.

Probably get the same result using coarse wet and dry.

regards

beach bum

 

[copper_head]

cheers mate ill google it up!

 

[demographic]

Yep, sounds like valve grinding paste to me.

The last lot I bought (course and fine containers bought for lapping my tapered crank end into my motocrosser flywheel) cost something like £1.75.

Didn't exactly break the bank and its a lifetime supply for me.

 

[Draven]

yup, valve grindin compound 'tis.
Fun stuff for whatever reason... I'm strange that way... and as demographic said, it's cheap and will last a while.

 

[Tadpole]

heh all,
Got myself an arkansa tri stone from knifeart.com a few years back. great set of stones but has now got a couple of chips in it and has started to bow, mr Mears says you can regrind a flat surface with a pane of glass, washing up liquid and something called 'piston carbondrum grinding paste' any ideas what this stuff is and where i can aquire it? cheers

When resurfacing anything, be it a bench stone or a grinding wheel, great is needed to be taken to not to make things worse.
The stone may bow or dip towards the middle, and re-grinding it on a flat surface, a proofing staff or for example 6mm flow glass, will take out that bow, but it will, unless great care is taken, distort the stone making the two faces but totally out of parallel.

Not much of a problem if you are aware of it, but if you are new to sharpening, any unevenness will just make your job harder. I’d personally suggest that you flatten the least bowed side first making sure that you keep checking that the sides are parallel to the face. Once one side is flat you can them mount the stone so that the opposite side is upper most.
If possible you should try and keep the back of the stone parallel to the glass, that way the stone will be even and flat.
I know it is a pain to keep checking that the stone is parallel to the glass, but will be worth it in the end when your stone is restored to use, as flat and true as it was when you got it.

 

[copper_head]

Hmmm... I figured is was done by using the flatness of the glass panel to achieve a flat edge. Is there something I missed?

 

[copper_head]

This is my benchstone that needs work...

 

[Tadpole]

Hmmm... I figured is was done by using the flatness of the glass panel to achieve a flat edge. Is there something I missed?

one flat edge is ok on a single grit bench stone, but a combination stone you’d need two parallel surfaces, or everytime you changed from one grit to the other you run the risk of undoing all the hard work you've just done.

 

[C_Claycomb]

Tadpole, you have me confused.

There are several things about what you are saying that have me puzzled. The first is that it sounds like you are talking about the kind of combination stone that has say 1000 grit on one side and 6000 on the other, like this:

It seems to me that all your descriptions about keeping opposite faces parallel does not really apply on the kind of combinaiton stone that Copper_head is using.

but a combination stone you’d need two parallel surfaces

umm...but this is a tri hone, each grit is mounted to the central block independent of the other. It is not possible to grind any two working faces parallel, and no two faces on the same stone without unmounting the stones from the wood base.

Next, while I can understand that it is ideally desireable to maintain a stone so that all opposing faces are prarallel, and all adjacent ones are perpendicular, I don't see that it would cause any great problems if, on a dual sided combination stone, you had the opposing faces out of parallel. On all but the most friable of stones it would take a long time to get more than a couple of degrees of error, and even if you did, sharpening action is relative to the working surface of the stone, not to the surface of the bench/table.

On a tri-sided stone, if you really messed up and made all the stones taper in thickness along their length, or across their width, the real problem would be that the three sided assembly would no longer sit firmly in the base unit. I have only used hard Arkansas stones, but that wears so slowly that I can't see this happening. Even if the stones on the tri-hone are as soft as, say, 800 grit waterstones, I wouldn't worry about it since if worst came to worst a little packing with tape would make the whole lot sit firmly again.

I hadn't thought of using valve paste, I have some really old tins of carborundum grit, but other than going through Axminster tools I wouldn't know where to get more. When my Arkansas eventually needs attention I will give the paste a go.

 

[copper_head]

thanks chris, cleared that up for me. I thought I was being really dim! Got myself some course/fine valve grinding paste of the net... Should be delivered on tuesday I'll let peeps know how I get on. It'll be nice to have clean flat stones again...

 

[Tadpole]

Tadpole, you have me confused.

There are several things about what you are saying that have me puzzled. The first is that it sounds like you are talking about the kind of combination stone that has say 1000 grit on one side and 6000 on the other, like this:

On a tri-sided stone, if you really messed up and made all the stones taper in thickness along their length, or across their width, the real problem would be that the three sided assembly would no longer sit firmly in the base unit. I have only used hard Arkansas stones, but that wears so slowly that I can't see this happening. Even if the stones on the tri-hone are as soft as, say, 800 grit waterstones, I wouldn't worry about it since if worst came to worst a little packing with tape would make the whole lot sit firmly again.

I hadn't thought of using valve paste, I have some really old tins of carborundum grit, but other than going through Axminster tools I wouldn't know where to get more. When my Arkansas eventually needs attention I will give the paste a go.

Ok not being able to see the restricted site he used, meant that i could not see the tri stone. what I said still stands for a two side combi stone.