Source for single point diamond dressing tool

Any suggestions for a decent quality one of the above at a sensible price? Ideally on a 3/8" UNF a couple of inches long but I can die the thread on if
not. I'm having a bit of a mare getting a good finish on valves in my B&D valve refacer at the moment and the very rounded off diamond tool might be the reason. I suspect I'm smearing the wheel more than dressing it and the result is lots of chatter on the valve seats.
Also is there much difference in quality between cheap and expensive? A diamond is a diamond after all and I can't imagine some are harder than others. The one I have doesn't seem to have done that much work before ending up looking like a ball bearing though. Ok so it's ten years old but all it has to do is dress a 1/2" thick 5" wheel every few months. I think it was only a few quid from a model making exhibition and maybe has a very crappy diamond in it. Things like camshaft and crankshaft grinders with 1" wide 3 foot diameter wheels must require a huge amount of grit dressing off and I'm sure the dressing tools don't only last 5 minutes. How long do your ones last? I can only use mine dry although wet would perhaps be better if I could rig a coolant feed up.
Final question. Resetting an existing one. I tried on a diamond lap wheel but couldn't touch the diamond in the dressing tool. However my lap wheel is a little plastic impregnated one built in to my engine boring bar and possibly not the right thing at all for dressing another diamond. Anyone succeeded in resetting one and if so how? -- Dave Baker - Puma Race Engines (www.pumaracing.co.uk)
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On Thu, 20 Jan 2005 22:11:16 +0000, Dave Baker wrote:

Not really addressing the above, and with the caveat that I really don't know what I'm talking about, but I've read that a diamond should only really be used to true up a wheel. To dress it, i.e. open up the grain, you use a dresser (one of those star wheel things).
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On Thu, 20 Jan 2005 22:11:16 -0000, "Dave Baker"

Had the same trouble until I discovered multipoint dressers. These have hundreds of tiny diamonds embedded within a block of sintered steel(?). Before a diamond gets blunt enough to matter it's torn away and a fresh diamond takes over. These tiny diamonds are more "pointy" than even a slightly worn single point dresser. Diamond usage rate is very low and my single sample is looking as if it will well outlast any of my previous single point dressers.
I got mine years ago from Gurney Engineering (01205 355998). A similar item is now sold by Arc Euro Trade but judging from the illustration it uses a single layer of diamonds rather than a sintered block.
I believe the standard method of refurbishing single point dressers is to reset the diamond by melting out the spelter and then reinstalling the diamond with a different point showing. I tried to do this with mine - with total lack of success!
Jim
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