Synthetic polycrystalline diamond paste — cheap and otherwise

[David Barnett]

A couple people have asked me where to find friable synthetic diamond paste. Although you can purchase highly graded polycrystalline diamond from metallographic suppliers such as Pace Technologies' Diamat PC paste—there is none better—though 5g of 1µ will set you back $37, whereas Professional Gem Tools, Inc., through Pala International makes it easy and more affordable, offering both compound (paste) and powder (loose grit) for as low a price as you're likely to find for a premium product—$18 for a 5g syringe—and they'll gladly accept orders for just one syringe at a time.

LapidaryPro High Grade Friable Diamond Compound

0.125µ__200,000 grit
0.25µ___100,000 grit
0.5µ_____60,000 grit
1µ_______14,000 grit
3µ________8,000 grit
6µ________3,000 grit

Each 5g syringe is $18.00

So much for the higher priced spread. A still cheaper option may appeal to some. While I require painfully tight grading for polishing faceted gems, for sharpening I'm not so pernickety (that's right, not persnickety) and will accept a few outliers, especially when skewed to the smaller than nominal micron end of the curve, which brings me to THK diamond paste.

THK (Treasure Hong Kong) offers direct online sales through their website and through eBay, as well. I had heard THK's pastes were polycrystalline, had seen a rather disquieting YouTube video where this was stated in the comments* and so wrote to Teddy Lau of THK to confirm if this was so. Mr. Lau wrote back yesterday morning, assuring me that his pastes were indeed formulated with polycrystalline diamond sands while monocrystalline diamond was used for his vacuum brazed industrial products.

While I've not tried THK's diamond lapping compound—I do intend to, of course—I thought I'd pass it along to any adventurous and frugal souls who might wish to trailblaze while I endeavor to overcome my procrastinative sloth (a trait—not an unmotivated arboreal pet). Until I've actually tried the THK product I can't vouch for it, obviously, but there you have it. I can say I've found a kilo of remaindered coarser polycrystalline diamond grit for just over $100 recently, so I would suppose such pricing for PCD compound is imaginable.

What you get:

7 syringes, 5g each

0.25 Micron - Final Polish (Light Grey)
0.5 Micron - Final Polish (Rose)
1.0 Micron - Mirror finish (Light yellow)
1.5 Micron - Mirror finish (Dark yellow)
2.5 Micron - Mirror finish (Pink)
3.5 Micron - Fine Polish (Red)
5.0 Micron - Fine Polish (Blue)

PRICE:
USD 10.00

SHIPPING:
USD 4.00

SHIPPING DETAILS:
Regular Air postage with handling from Hong Kong to worldwide is US$4.00 and takes 7-10 days delivery to your home.

13 syringes, 5g each

0.25 Micron - Final Polish (Light Grey)
0.5 Micron - Final Polish (Rose)
1.0 Micron - Mirror finish (Light yellow)
1.5 Micron - Mirror finish (Dark yellow)
2.5 Micron - Mirror finish (Pink)
3.5 Micron - Fine Polish (Red)
5.0 Micron - Fine Polish (Blue)
7.0 Micron - Pre Polish, fine lapping (Purple)
10 Micron - Lapping metals (Grey)
14 Micron - Stock Removal or lapping metals (Brown)
20 Micron - Stock Removal or lapping metals (Rust)
28 Micron - Medium fast lapping (Green)
40 Micron - Fast lapping or stock removal carbide (Black)

PRICE:
USD 20.00

SHIPPING:
USD 5.00

SHIPPING DETAILS:
Regular Air postage with handling from Hong Kong to worldwide is US$5.00 and takes 7-10 days delivery to your home.

Personally, for sharpening chisels and plane blades I really only use 1µ paste, for carving tools I sometimes will use submicron pastes, so buying all the grits isn't my best option and I do find the micron increments too gradual and compressed for my use. However, Teddy Lau says you can choose any combination of grits to make up your 7 or 13 syringes—you can have 7 of 1µ if that's what you want**—so it'd be pretty hard to not to come out where you want to be.

Anyway, these approximate diamond micron to grit equivalents give a sense of the range.

0.25µ_100,000 grit
0.5µ___50,000 to 60,000 grit
1µ_____14,000 grit
3µ______8,000 grit
6µ______3,000 grit
15µ_____1,200 grit
30µ_______600 grit
40µ_______400 grit

So, while I mix my own high-concentration diamond compound and really don't need any, I'll have to try these THK compounds just to see if they're the ultimate bargain in diamond pastes, even should they turn out not to be polycrystalline. I will say I've been terribly happy with my remarkably inexpensive Asian faceting laps and gem saw blades, and quite satisfied with the Asian monocrystalline products. If anyone beats me to the punch on this, do let us know what you think.


*"There had been a number of complaints/concerns brought up by users who purchased the THK branded polycrystalline diamond compound from Hong Kong regarding it being too viscous, waxy, clingy, etc." which turned out not to be the case for the YouTube reviewer, by the way, subjective though it is.

**From the THK website: "Please let us know if you are looking for any combination."From eBay: "We are pleasure to send different assortment. For examples, you can choose 7 pieces of 0.25 micron. Please remind us when you settle the payment by Paypal (write PAYPAL message)." The same goes for the set of 13.

[Dave Cav]

At these prices I may have to give diamond paste a try. Would MDF be an appropriate substrate, or something harder?

OK, I just read a few old threads and it looks like most folks are using MDF or hardwood plywood.

[Kurt Cady]

About How long would one 5g syringe last?

[David Barnett]

At these prices I may have to give diamond paste a try. Would MDF be an appropriate substrate, or something harder?

While MDF will work it was mostly used because it was for the most part already flat, as was plywood with smooth birch or maple outer veneers. An article in FWW years ago declared solid hard maple a better substrate than MDF whereas these days balsa is favored by both the straight razor and food prep communities.

As far as hardwoods go, the substrate considered the best diamond carrier among gem carvers is pink ivory, I kid you not*, but really, I'd say for the 1µ to submicron diamond I favor for woodworking tools, carving gouges and gravers, any flat hard surface will serve. While I mostly use cast iron, others use acrylic, Corian, paper phenolic, copper, certain ceramics, horse butt and so on. If I ever met a hard cheese I didn't like, I'd likely try that, too.

But yes, MDF will get you started. Takes a bit more paste to initially charge and bring it to equilibrium, but it'll get you through 1µ.

____________________________

*In a 2004 issue of Lapidary Journal, Derek Levin rates woods suitable for charging with diamond for rotary handpiece or fixed arbor gem carving and polishing points (burrs), and has this to say:

"Pink Ivory — a wood from Africa, is Henry Hunt’s #1 choice. It’s a beautiful dark pink wood with many worthy characteristics which I’ve enjoyed having, although it is quite hard, rare and expensive. It shapes easily and holds diamond compound very well, whether the diamond is in an oil or a wax base. It also holds its shape well, and is especially useful with sharp edges for those straight line indentations."

Other worthwhile hardwoods include boxwood, ivorywood, briar and holly. There are others, of course, and I've tried quite a few. I make my points from buxus and pink ivory, mostly, and I have two excellent PI strops.

[David Barnett]

About How long would one 5g syringe last?

Years for woodworking tools. especially on cast iron. Once a lap is well charged, the amount needed to refresh it is downright picayune. I have a syringe of ½µ (60,000 grit) diamond in my woodshop that I bought in 2000. There's at least a couple more years left in it. People have a tendency to use way too much and it can be hard to disabuse them of the habit. Coarser grits do go faster than finer, but for anything 3µ (8,000 grit) and smaller, it's trivial. That said, at $2 and less per 5g syringe, it's about the cheapest sharpening consumable going, so feel entirely free to slather it on.

[David Weaver]

Another excellent line of posts, David, with satisfying detail and delivery. It should be archived. Thorough answers to any of the sharpening questions should be, as we seem to get the same ones over and over.

[Chris Hachet]

Another excellent line of posts, David, with satisfying detail and delivery. It should be archived. Thorough answers to any of the sharpening questions should be, as we seem to get the same ones over and over.

Yes, please archive this. I am not ready to buy this yet, I have been using Diamond stones and Oil stones and just bought my first water stones yesterday. I want to get used to trying water stones before I try diamond. And thanks to David B for the link...I am learning more here at the creek every day!

[Jessica Pierce-LaRose]

Any comments on diamond for sharpening profiled edge tools? I'm thinking gouges and molding plane irons (particularly hollows), and more curious about slight restoring over final honing.

While on the few profiled tools I have I keep the edge working order with a strop, I feel like eventually it's goings to need something more. I can probably rig together something for grinding with the tools that I have, if I pick up something used that needs a lot of attention, but part of what's held me back from getting more tools of this sort has been not having any slip stones, and not being terribly thrilled with using sandpaper on shaped substrates - it seems to me that shaping something and applying diamond seems less expensive than picking up slip stones for those medium steps between grinding and stropping.

It makes me wonder though about how to choose something that's easily shaped for use a substrate yet would hold it's shape enough in use.

[David Weaver]

Hard maple is cheap and makes decent shaped slips with compound, etc.

one or two pieces of profiled hard leather wheels work well, too, and you can make those or buy them (feeding something to them always has the chance of launching, though).

[David Barnett]

Hard maple is cheap and makes decent shaped slips with compound, etc.

I have so many carving tools and so many shaped strops I've started storing them with the tool/gouge for which they're intended. I have trays instead of racks so this is doable and often the tool rests on its dedicated strop. Miniature chisels, gouges, and knives I store in smaller boxes with their strops. It's the only way I can keep up with all the blocks, half-cones, sanding sticks, dowels and whatever else I once made and forgot about. Not every tool has its own strop of course.

Anyway, I now only have two tool rolls and those hold stonecarving and lettercutting chisels apt to get used on the lanai. I leave a box of honing materials in one of the lanai closets.

While maple's my mainstay for hand carving tools, the larger gouges and allongees get horse butt for both diamond and oxides. So many substrates work for diamond paste, loose grit, sprays, though—wood, acrylic, polycarb, nylatron, vinyls, leathers, felts, fibers, woven goods, hard machinable microcrystalline waxes, zinc, copper, cast iron, thermoplastic resins, ceramics—just to name a few. And for metals, they can be scraped, frosted, smooth, roll printed, scored, mezzotint rocked, sanded and so on. There's even clay—or rather plastiline, if you don't want to shape all those slips and strops.

Take a slice of firm plastiline (I like the sulphur-bearing extra-hard Roma Plastilina), work in a whole lot of loose diamond grit, press it to fit a particular gouge's sweep and it will work very nicely until pressed to fit another tool or an otherwise contoured metal for cleaning or polishing. Tweak it with oils and waxes to soften its consistency or add kaolin to stiffen. It's great for cleaning and polishing metals and other hard surfaces, too. Years ago I actually thought about selling the stuff. Turns black really fast.

One or two pieces of profiled hard leather wheels work well, too, and you can make those or buy them (feeding something to them always has the chance of launching, though).

Wheels—felt, paper, other fibers, leather, wood, whatever—and ensuing excitement is another post altogether.

[David Barnett]

It makes me wonder though about how to choose something that's easily shaped for use a substrate yet would hold it's shape enough in use.

Joshua, I've made shaped diamond-carrying substrates of various kinds, such as thin copper over wood, machinable and castable microcrystalline waxes, other casting RT resins and thermosetting resins, such as Jett-Set. All work, of course, so it comes down to practice and preference. The resins generally work better with a layer of loose diamond affixed by the setting resin or other coatings, whereas the wood, metal or fiber products perform better with pastes.

[Jim Koepke]

Yes, please archive this.

At the bottom of the page is a very useful tool:

Picture 1.jpg

This allows people to insert search terms to find a thread in the future.

I find it quite handy.

jtk

[Jim Neeley]

Has any one tried the DMT Wave diamond sharpeners for profiled tools? The widly ranging radii available looked like it might be a good tool.


If nothing else, perhaps a choice to re-charge with diamond paste?

I have yet to venture far down the path of sharpening profiled tools (or own that many either) for this very reason.

Advice and experience appreciated.

Jim in Anchorage

[David Barnett]

Another excellent line of posts, David, with satisfying detail and delivery. It should be archived. Thorough answers to any of the sharpening questions should be, as we seem to get the same ones over and over.

Of course, as I was simply offering sources for friable diamond paste, I didn't state my reasons for preferring friable and polycrystalline synthetic diamond over monocrystalline for most sharpening in the woodshop. My main reasons, as you know, are twofold:

Firstly, each polycrystalline diamond particle has many more cutting points than monocrystalline diamond, leaving shallower troughs in the metal being sharpened, cutting faster, embedding securely in substrates and presenting fresh cutting points, as, unlike monocrystalline diamond's adverse cracking and splintering, polycrystalline diamond, having no cleavage planes, fractures far more advantageously.

Secondly, due to its friability, it continues to cut longer and more consistently than fractured monocrystalline diamond*, progressively cutting ever more smoothly, linearly easing and blending the scratch pattern into a refined result or transitioning to subsequent abrasive media should that be required.

I like that I can get to a desired surface refinement endpoint, an optimal degree of polish on a tool edge, with fewer grits, hence fewer steps and do so with acceptable rapidity.

Although polycrystalline diamond is usually, initially more expensive than monocrystalline per weight—never mind what is erroneously stated in some woodworking product descriptions—it amortizes favorably in the amount required on a given substrate once charging has reached a point of sufficiency and equilibrium.

Compared with monocrystalline consumables, depending upon the application, substrates and amounts required to achieve a target surface refinement, polycrystalline may be more cost effective than monocrystalline, but not always, and must be determined through actual use.

For rapid and frequent refreshing of grit and very specific scratch pattern uniformities, monocrystalline diamond may be preferred. The exceptional crystal size and shape uniformities, highly-aligned distribution of monocrystalline 3M diamond lapping films, such as those sold by Lee Valley, are an excellent example of how these features can be exploited.

So while I prefer friable polycrystalline diamond for many sharpening and polishing applications, monocrystalline diamond does much of the grunt work to get to the point where polycrystalline's best advantages are realized. For example, I'd generally choose monocrystalline diamond for rough lapping such as flattening chisel and plane blade backs on exceptionally tough, hard tool steels, as CBN is more expensive and silicon carbide would break down too quickly.

I'd likely lap backs to 30µ (600 grit), or maybe even 15µ (1,200 grit) or perhaps all the way to 6µ (3,000 grit), depending on the tool, before switching to polycrystalline for a bit of polish. For day-to-day chisel and plane sharpening, though, I mostly go from a 7" bench grinder to the 600 grit Eze-Lap, hopping to 1µ (14,000 grit) polycrystalline paste on cast iron, sometimes finishing with a ½µ diamond or oxide charged strop. Thing is, when the last charge of 1µ poly's settled in on the cast iron, I don't notice a lot of refinement beyond that unless I'm stropping carving tools with very low, thin bevels

Anyway, I guess I'm thinking my poly post isn't really robust enough to archive without mono content, but what do I know? At least those who want to try polycrystalline paste can get their hands on some (or vice versa) for not a lot of spondulicks.

*Why so many monocrystalline electroplated sharpening products give up the ghost fairly early and rapidly.

[David Barnett]

Has any one tried the DMT Wave diamond sharpeners for profiled tools? The widly ranging radii available looked like it might be a good tool.

Advice and experience appreciated.

It's a cool product, Jim, but it's maybe more fun to look at than use, as the area that isomorphically fits any given tool cutting edge contour can in practice be a fairly small, short region, especially for fishtails and spoons. But maybe that's just my gouges or my sharpening style.