Diamond paste sharpening ...

[bugbear]

Diamond lapping machine eh? Don't let bugbear see you're getting one of those .

Heh. I have all the flattening kit I need; 1 surface plate, some blue crud, and some metal removing tools (files, scrapers, scraps of AlZi)

It's enough to do rather accurate work, as it turns out.

BugBear

 

[Rob Lee]

Diamond lapping machine eh? Don't let bugbear see you're getting one of those .

Heh. I have all the flattening kit I need; 1 surface plate, some blue crud, and some metal removing tools (files, scrapers, scraps of AlZi)

It's enough to do rather accurate work, as it turns out.

BugBear

Ah - but ours is (will be) "sweatless"... turn it on, walk away, and come back to a 10u finish..... 8) 8)

 

[Wiley Horne]

In my experience, the surface finish of the iron plate matters, especially when you get down into the 1/2- and 1/4-micron meshes. You want smooth. How smooth?--I dunno, real smooth, about like a plane sole. Smoother is better. Price point: $50. Length: 8" real good; 10" better.

Wiley

 

[Philly]

Axminster do this plate.
Any good or too expensive?
Philly

 

[Jarviser]

BB - shame .
J - I have tried that with an old plane I already have. Trouble is it's not flat enough. And it's a lot work to get it good enough for flattening other stuff. I may try it again though - or try and pick up something flatter ...
Cheers
Gidon

Sorry I didn't respond - I'm still not getting any notifications.
To flatten other things, yes you need a surface plate.
To hone a blade it needs to be flat across the width, but in the length it doesn't have to be flat at all. You can hone a blade on a curved surface if you use any wheeled holder, the ultimate curve being a Tormek wheel. I would have thought the surface of a typical DIY plane would be flat enough for honing.

 

[gidon]

Thanks Philly - again it's that textured surface that won't be any good for the fine paste. And too big really - just need something the size of a standard sharpening stone ...
J - I never get those notifications either (well not reliable) so don't bother with them anymore. If the plane was flat across its width yes it'd be fine for honing I guess (as long as you kept your strokes straight up and down). But I still wouldn't want my nicely polished backs touching an unflat surface. As it is it's not reliably flat in any direction .
Cheers
Gidon

 

[Javier]

I think I've read somewhere that the iron plates are soft enough to allow the
diamond particles to become imbedded. Does this sound right?

 

[gidon]

Javier - I think's that's it. That's why it's quite tricky finding a substrate with the right balance. You want the diamonds to stick, but not sink! So although Maple works ok - it's still porous so you need more paste plus the cutting action is meant to be slightly less aggressive because the particles are more embedded than with say iron.
In this article, the author tried Maple, MDF and steel - and found steel gave the worst results followed by MDF. And Maple was best. She was looking at the results under an 700x microscope. unfortunately she didn't try iron. But I know for a fact that maple does give good results even if you do need more paste. But as I mentioned earlier the problem for me is ruining the nice flat surface by digging in the blade or scraping with the burr.
Cheers
Gidon

 

[Miles968]

A good source of info on lapping (for precision machining, and polishing gemstones) is Kemet International http://www.kemet.co.uk/about_kemet.html - there is a specific composite material they make that is supposed to be even better than cast iron, but CI is also on their catalogue. Lots of diamond pastes too - I suspect they would be a good choice, better than going via some non-specialist supplier. When I get a moment I'm going to try some...

On Woodcentral we had another little discussion like this, and I got a quote from Kemet - they do circular lapping plates (cast iron) for about £60, or sheets of the Kemet GP4 for £14 each but with a 10-off minimum order. Any chance that people here would want to get together and order a stack (2 sheets each I reckon, for a coarse and a fine grit)? I would do admin.

It's my feeling that getting the right grade of substrate is important if you really want to assess the performance of this technique - if ordinary steel doesn't work quite right, but CIron does, then a specialist supplier who does nthing else is at least going to supply the 'right' grade of CI which can serve as a reference for substitutes.

Miles

 

[gidon]

Miles
Thanks for the information. The paste I have is from Kemet and I have spoken to one of their chaps before. Unfortunately although he was helpful you seemed to have gleaned some more useful information from yours .
It does sound interesting. I would be interested into one of the composite plates for £14. Do you know how flat they are? And will the material stay flat? What size / shape are they - on the web they look like discs which wouldn't be so handy for sharpening. What grits are the GP4 plates intended for - I'm personally only really interested in used the finer paste (<=1 micron) on mine. Sorry for the questions but will save me finding the right person to speak to if you already know the answers.
Cheers
Gidon

 

[Miles968]

Gidon, this was the quote I had from Kemet - I think the cast iron plates are circular - probably fine for hand lapping, just have to learn a slightly different stroke - for running a jig on, not so great but of course one can always mount them in a larger area of something to run the roller on (as I already do with my DMT so I can use the full length)

I think GP4 is suitable for all grits, no info to the contrary yet, we could check. Jeff Brown was the guy I spoke to at Kemet. It's a shame they don't sell other shapes/sizes of plates - maybe they would be willing to just supply some rough cast iron of the right grade, we can machine/lap it ourselves if we want to

342743 6" Cast Iron Plate £51.00
342705 8" Cast Iron Plate £61.60
E04069 Kemet GP4 Sheet 6" x 2" x 18mm Thick £14.38 Each
Please note item 3 has a minimum order quantity of 10

A 'full sharpen' for me (new primary bevel) means I go from 80grit on a belt sander (not a worn belt) to a 15 micron (red) DMT (quite worn now) to blue compound on leather - gets a fine polish in only a few minutes start to finish. I sometimes use an oilstone instead of DMT but DMT is usually faster, and seems not to cause any problems. Now I'm honing at the end I am finally getting 'shaving sharp' edges much better than without. The very slight rounding towards the edge from honing is probably a good thing for edge life (the back is still as flat as I can keep it, I can hone on a hard surface like MDF).

Using loose diamond rather than DMT will just mean never having a worn-out middle stage abrasive in this sequence...

happy sharpening

Miles

 

[gidon]

Thanks Miles. The 6x2 inch plates sound ok - although a little small for my plane blades. I still favour Rob's plates to be honest - but from his earlier comments they could be some way off (do you have a ball park figure Rob if you were to go ahead with them?)
Could they send you a sample piece of this GP4 before comiiting to an order. Even a small piece would confirm (or not) its suitability?
Cheers
Gidon

 

[Alf]

On WoodCentral Rob gently chastised me for getting folks' hopes up (in a very roundabout way) and pointed out they were only doing next Christmas's stuff now, so presumably not until next year at the earliest?

Dunno if you got my email, Miles? Anyway, I'd be willing to give the 6x2 plate a shot - it'd be nice to know which grits it's suggested for, though. If it's across the board then two would make sense, as you say, for the highest and lowest grits I have and use most.

The cast iron is really a bit steep for an less than optimum shape for our purposes, IMO. I dunno, what are the varieties of cast iron? If anyone has access to a means of flattening it, is the stuff offered here (for example) any use?

Cheers, Alf

 

[bugbear]

If anyone has access to a means of flattening it, is the stuff offered here (for example) any use?

Ooh, ooh! Flattening! Ask me, ASK ME!

BugBear

 

[Alf]

If anyone has access to a means of flattening it, is the stuff offered here (for example) any use?

Ooh, ooh! Flattening! Ask me, ASK ME!

BugBear

Let me re-phrase that. #-o

A means to flatten economically and reasonably quickly without having to learn a whole new skill or technique....

Yes, the BugBear at the back of the class? You think you have the answer? Alright, put you hand down, lad, before you pull something. :roll: :lol:

Cheers, Alf

 

[Miles968]

Alf's source looks very economical, and we should make the link between the type they are supplying and what Kemet say is preferred for lapping.

Once we have N plates, then it should be possible to either have them machined and polished (or we polish them against each other in the classic A/B/C method until they are fine enough for use, or get BB to scrape them all in his spare time for the next couple of years).

The key point for me is to get an economical source without having to go with something of unknown character. Is there something special we need to know about or will 'any old iron' perform well in this application? Once we know this, the maddening confusion will be forever reduced!

Alf, can you ask your source for the grade/source/type of material they are selling? We can then check it and go from there.

I would be willing to buy up to 4 Kemet composite sheets, if we can find volunteers to take on 6 between them then we can have a go with this alternative. 3 each, Alf and Gidon, what about you BB?

Miles

 

[Alf]

...or get BB to scrape them all in his spare time for the next couple of years

Gets my vote... :wink:

Alf, can you ask your source for the grade/source/type of material they are selling? We can then check it and go from there.

Not likely. "Guv, there's some daft bird asking what kind of cast iron it is" "Women. :roll: Tell her it's the heavy sort". I can see it all too well. I need to have a vague idea what the hell I'm talking about first! :lol: I just thought cast iron was cast iron, to be honest.

Cheers, Alf

 

[gidon]

OK Miles - please put me down for one if you go ahead.
From most of the posts I've seen I think any bit of cast iron is ok. What I'm not sure about is how smooth it needs to be. I think for the fine grits the answer must be smooth - the roughness can't be proud of the embeded diamonds?
Maybe we should be speaking to Axminster? They should be able to knock this sort of thing up (or source it at least) I would have thought if they think there is demand?
Cheers
Gidon

 

[Miles968]

Gidon, thanks for stepping up to the plate.... (I can't belive I wrote that before realising what a bad pun it is!) - Alf, are you game too? BB, can we persuade you to chip (in)?

I will try to get Kemet to ease up on the minimum order - can't really see why they shouldn't, it's not a complicated one to process. If I can find out more about 'good' and 'bad' cast iron (e.g. how modern ductile iron compares to classic cast iron) as far as a lapping substrate goes, I'll pass that on as well.

Seems to me that we could do with a few of the metallurgists who hang out on the knifemaking forums, endlessly discussing steel and edge holding properties, to tell us more about cast iron and diamonds - presumably knifemakers also sharpen from time to time?

cheers

Miles

 

[DaveL]

Miles,

I probably don't need one, but am hopelessly on the cast iron slope, put me down for one. :roll: