Making a diamond burnishing point

SShep71 · Jul 16, 2021

In my attempt to pass this trade off to the "younger generation" I wound up with a casualty of the tool cabinet. The diamond point of my diamond burnishing tool got ripped off, I am trying to source a replacement (although that is proving hard enough). My alternative is to try to remake the diamond point, but I am not sure if this can be simply done. Where I have my doubts is the shape of the diamond point, is it a specific design or shape? Can I source a generic industrial diamond (such as a wheel dressing point) to lap flat and use? Can a replacement diamond insert be cemented in? I am in uncharted waters here and I was hoping to get some help.

eKretz · Jul 16, 2021

That is a good question. If I recall correctly I have seen some literature that suggested that the diamond points for burnishers are polished to a specific hemispherical radius. That can be done with a jewelers type setup for diamond cutting - those use loose diamond grit on a lap to cut the gem being shaped - or something similar. I know of no other way to do it. New diamonds can certainly be soldered in (this used to be done regularly back when reconditioning diamond dressers), but I suspect they'd probably need shaping afterward. Shaping a nice even hemisphere might be a little challenging.

SShep71 · Jul 16, 2021

That is what I am finding in my research, a .4 - 1.0mm radius is polished on the diamond points from what I am able to find. I never soldered/brazed a diamond before, I am kind of curious as to how this works. I have a local jeweler in town that may be able to help figure this out. I still don't mind the input, and if I figure anything out will surely past updates.

jccaclimber · Jul 16, 2021

I'm mostly tagging along for the ride here, but I'm also curious how they are brazed in. One of my jeweler friends has mentioned that diamonds aren't exactly their favorite gemstone to work close to despite being a large portion of his business. Being carbon they have a habit of turning to CO2 if overheated in an oxidizing atmosphere.

gbent · Jul 16, 2021

The mackle used for diamond dressers can be reset easily when dull. Heat the diamond dresser with a OA torch to melt the solder. At temperature a slight tap and the mackle will fall out.

Diamonds are set in a mixture of silver solder and steel powder. To set a mackle drill a hole where you want the diamond just large enough to hold the diamond and about 1/16 to 1/8 deeper than the diamond. Bed the diamond with fine iron or steel powder so the desired point is up. Cover the mackle with the metal powder. Now heat the diamond holder to silver brazing temperature and fill the cavity with silver braze. When cool the steel can be dressed away to reveal the diamond. The points for fussy applications, such as radius dressing diamonds are lapped after being set.

redlee · Jul 16, 2021

You say you cant find a replacement tip ? What brand is yours, Cogsdill has replacement tips available.

SShep71 · Jul 18, 2021

@redlee: Mine is an Elliott. I was able to get ahold of a sales rep for Elliott and I was told that Elliott burnishing tools are sold through Monaghan, I did see some email traffic between the Elliott sales rep and the Monaghan sales office. Hopefully this replacement diamond isn't ridiculously overpriced, but in case it is I want to have a plan in place.

@gbent: I am going to have to look into all the information you set us up with, I know a good amount about silver soldering and bedding gems for jewelry, but never for an application with this level of pressure applied.

Marty Feldman · Jul 18, 2021

gbent said:
The mackle used for diamond dressers can be reset easily when dull. Heat the diamond dresser with a OA torch to melt the solder. At temperature a slight tap and the mackle will fall out.

Diamonds are set in a mixture of silver solder and steel powder. To set a mackle drill a hole where you want the diamond....

"Mackle" is an unfamiliar term to me, although a nice industrial sounding word. About the best I can find is a definition denoting a printing error, the blurring or doubling from incorrect impression alignment.

-Marty-

eKretz · Jul 18, 2021

SShep71 said:
@redlee: Mine is an Elliott. I was able to get ahold of a sales rep for Elliott and I was told that Elliott burnishing tools are sold through Monaghan, I did see some email traffic between the Elliott sales rep and the Monaghan sales office. Hopefully this replacement diamond isn't ridiculously overpriced, but in case it is I want to have a plan in place.

@gbent: I am going to have to look into all the information you set us up with, I know a good amount about silver soldering and bedding gems for jewelry, but never for an application with this level of pressure applied.

Kind of funny. Elliott has a shop right down the street from me. I know a guy that used to work there.

gbent · Jul 18, 2021

Marty Feldman said:
"Mackle" is an unfamiliar term to me, although a nice industrial sounding word. About the best I can find is a definition denoting a printing error, the blurring or doubling from incorrect impression alignment.

-Marty-

Macle

A term used in the diamond trade for a flat, triangular, rough diamond, which is a twinned crystal of the spinel-twin type (in which the twin plane is parallel to an octahedral face, with one side appearing to have been rotated 180 degrees with respect to the other). It is more difficult to fashion than most other crystals because of the differing grain directions caused by the twinning. Due to their odd shape, macles are often used for fancy cuts.

eKretz · Jul 18, 2021

eKretz said:
Kind of funny. Elliott has a shop right down the street from me. I know a guy that used to work there.

After a little Google sleuthing, it would appear that they are different Elliotts. The one down the road is "Elliott Group" who work on turbines and turbomachinery. The one who makes the burnishers is "Elliott Technologies" and they don't appear to belong to the same conglomerate.

I figured they did since the guy that used to work there had showed me the diamond burnishers they used, and I thought I remembered him saying they made them. Guess they aren't the same company though.

SIP6A · Jul 18, 2021

SShep71 said:
. The diamond point of my diamond burnishing tool got ripped off.

Is this a burnishing tool for use on a lathe?

SShep71 · Jul 19, 2021

Sip, it is for my lathe. I use it for working on hard materials on my manual 17x80" lathe. I tried to use one on a smaller bench type lathe once but the machine didn't have the rigidity to get a good surface finish. I just got a quote from Elliott Technologies, a new diamond tip is almost 200.00 for a replacement. Time to look at what I can make, before I ask for permission to spend that cash.

redlee · Jul 19, 2021

SShep71 said:
Sip, it is for my lathe. I use it for working on hard materials on my manual 17x80" lathe. I tried to use one on a smaller bench type lathe once but the machine didn't have the rigidity to get a good surface finish. I just got a quote from Elliott Technologies, a new diamond tip is almost 200.00 for a replacement. Time to look at what I can make, before I ask for permission to spend that cash.

IIRC the Cogsdill tip was about the same. They are pricey.

gbent · Jul 19, 2021

Please put up a few good pictures of the diamond when you get a new one.

CarbideBob · Jul 19, 2021

This is like new to me.
4 and under finishes are not but have not experienced this so eye opening.
So many questions in how a true surface is formed or cut at the mirror level.
I hate to say this but seems like a band aid on top of a cut. A patch or a fix.
Bob

eKretz · Jul 20, 2021

I've done a little reading on this, and it's pretty simple really, a relatively large, super-smooth, highly polished diamond radius is pushed into the workpiece with a specific pressure, then the work is rotated and the feed engaged, and the surface is burnished to a super-smooth finish. There are prerequisite levels of finish required as well as specific lubrication and speed necessary.

In summary, the process works through plastic deformation at a very small level, and also improves surface hardness slightly through cold working a thin layer of the material. It works better on medium to high carbon steel with a little hardness. Roller burnishing works a little better on low carbon softer steels, but doesn't improve surface hardness as much. Roller burnishing will give a little more surface finish improvement from an equal starting point in either case.

A big benefit of the pressure burnisher is that it can be used right in the lathe, with no other additional equipment necessary. This is good for very large stuff especially as there's no need to transport the work to somewhere with huge specialized grinding machines if all you need is a good surface finish.

Mike1974 · Jul 20, 2021

Those diamond burnishing tools are spendy for sure!

Precision Tooling by Cogsdill - Specialists in Hole and Surface Finishing

I want to say when we got a quote for an 80mm tool it was somewhere around $5k.

Mtndew · Jul 20, 2021

SShep71 said:
Hopefully this replacement diamond isn't ridiculously overpriced

Replacement diamonds for the Cogsdill is a little over $200. I would assume the Elliot to be a little cheaper.

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