Sharpening using valve lapping paste

[graduate_owner]

Hi all,
Another question about sharpening tools. I have some valve grinding paste, the sort that was used for lapping in engine valves in the old days, when cars had engines that diy people could work on. My question is, would this paste be of use in sharpening chisels and plane irons. If so, would I just put some on a sheet of, say, glass? Also does anyone know how the grits ( coarse and fine ) compare with sharpening stones?

K

 

[NazNomad]

You can get different ''grits'' of valve grinding paste, so I suppose it all depends on what you have there?

 

[graduate_owner]

Wow, fast reply. I don't know what type this paste is. It comes in an orange metal container about 1 1/2" diameter and 2" tall, with blue metal caps. Fine one end, coarse the other. Whenever I went to buy lapping paste this is the stuff I was sold, seemed to be the standard stuff for the job. I didn't even know that there were other grits available. Not very clear I'm afraid.

Apart from grit size, would I be correct in using it straight on glass?

K

 

[NazNomad]

Looking at this, for example - http://www.lapmaster-wolters.co.uk/cons ... fault.html

Course is 80-120 depending on the size of the abrasive grain.
Fine is 280-320 grit.

I suppose you could do a side-by-side comparison with a known grit and compare the scratches?

 

[MusicMan]

Yes to straight on glass.

Keith

 

[Peter Sefton]

I have tried a similar process in the past with diamond pastes on cast plates, it works but is messy.

I used to stock the Veritas lapping plate and grits but found I never recommended them to customers and eventually we stopped having them on the shelf.

Cheers Peter

 

[ED65]

Can I come at this another way and ask straight out why you'd want to bother? If it's just in the nature of wanting to experiment then fair enough, but TBH I think you'd have to be fairly unsatisfied with your current sharpening solution(s) to want to investigate this option.

Now this could highlight a genuine failing in your sharpening gear, which would be worth looking into. But it may simply show up a "grass is always greener" attitude, something that is very prevalent when it comes to sharpening these days; and it's something that active effort should be expended to combat

 

[bugbear]

Looking at this, for example - http://www.lapmaster-wolters.co.uk/cons ... fault.html

Course is 80-120 depending on the size of the abrasive grain.
Fine is 280-320 grit.

At those grits, it's more grinding than sharpening. But then, that's what they're for, otherwise seating in a valve would take forever!

BugBear

 

[thick_mike]

A flat piece of mdf works reasonably well with polishing compounds. It tends to hold the abrasive rather than let it be pushed around. I find the blade acts as a squeegee when using polish on glass, and the compound gets pushed in front of the blade rather than acting on the surface

 

[graduate_owner]

I have been sharpening using diamond grit stones but I am not really sure what grit they go up to. I think my finest was described as very fine - whatever that means. Then I hone on leather with a green soap. I seem to get reasonable results but I am no expert, not really even competent, but I am trying to learn, so that is why I was wondering about different methods. Can't say I have ever got to the stage of being able to have hairs off my arm yet.

K

 

[powertools]

That's a good question. Having spent many hours of my life grinding in valves and still having 3 tins of the paste sitting on my shelves I will give that ago.

 

[bugbear]

I have been sharpening using diamond grit stones but I am not really sure what grit they go up to. I think my finest was described as very fine - whatever that means.

If they're one of the well known makers, tell which ones you've got and we can look up the particle size.

There are several charts like this on the 'net.

http://sharpeningmadeeasy.com/grits.htm

BugBear

 

[ED65]

I have been sharpening using diamond grit stones but I am not really sure what grit they go up to. I think my finest was described as very fine - whatever that means. Then I hone on leather with a green soap.

That's a reasonable setup and many have something similar or equivalent.

Although getting an edge to shave arm hairs isn't necessarily the test for sharpness you want to use it is a good indicator of progress, and what you have there is capable of getting edges that good or better with the right technique.

What you're probably not doing is fully removing the rounding of the edge (the 'wear bevel') when you hone, or you're not fully removing the burr/wire edge created by honing which leaves a little curl of steel at the edge rather than the bevel and the back meeting at a sharp apex.

If you're leaving some wear bevel you should be able to see a glint of light from the edge when you're finished honing. A sharp edge is so thin there should be no reflection.

If you're leaving a trace of burr it can be too small to easily see but you should be able to feel it with either your fingertips or by flicking the edge with a nail (always do this by stroking away from the edge, not along it or towards it).