A new Diamond Cabochon machine part 1

The Cabing Machine shaft full view
Full view of shaft

Just thought I would let you all know that we are building a new cab machine, this one will be a lot different to our first creation of a few years ago as it will only use diamond as the cutting medium.

It will have four rubber expanding drums which are 8” diameter and 3” wide, these will be fitted with REZ belts, to all intents and purposes they are the same as the silicone carbide belts that you would use, except they are impregnated with resin instead of silicone carbide. The resin “holds” the diamond onto the belt which is applied as a paste and you use lapping fluid to thin the paste to help spread it over the surface of the belt.

Details view of cabing machine shaft showing threaded end with nut
End view of shaft

We have found this very cost effective when compared to buying a set of diamond wheels simply because when the cutting action becomes dulled, you just recharge the belt and don’t have to change an expensive diamond wheel.

As out original machine will do all the rough work through to 600 grit silicone carbide, the new machine will follow on from there and in many cases I don’t think that polish will be required, it certainly wasn’t on some Lapis we did as we got a mirror finish straight off the Rez belt.

Cabing machine shaft showing flanges in detail
View of the flanges

This will also be a “clean” machine as does not require water, instead you occasionally give the wheels a burst of lapping fluid to keep things lubricated and as you don’t hold the stone against the wheel for as long as you would with a wet machine, things don’t get too hot.

The stage we find ourselves at right now is that we have a shaft which is 24” long and 1” diameter. It has a left hand thread on one end and right hand thread on the other, a 2,3,4 pulley fitted, two ball bearing sealed pillow blocks and 4 pars of 3” flanges, so it’s just about ready for assembly. This assembly was machined and supplied by Andrew at ABC Polishing so thanks Andrew a great job.

Cabing machine shaft showing 2,3,4 pulley and bearings
View of the 2,3,4 pulley

We have just received the four expanding drums from the USA and we already have the REZ belts and diamond paste.

Next job is to make the supports for the bearing blocks and a base for it all to sit on. This machine doesn’t need hoods over the wheels and pans to catch the water as there will be none, so we plan to sit it on a base and make a cover to go over the whole machine for when it’s not in use to keep dust out.

I also had a single phase motor that I was going to use for this machine, but it died so have to order a new one soon.

I will keep updating as the machine progresses through the build and report on its performance once it’s operational.



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A new Diamond Cabochon machine – conclusion

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  1. Well in your message of March 26th I didn’t see a question to answer! In your latest question I see no please or thankyou, which is customary in my part of the world. Kindly rewrite your question and I will answer it, thankyou.

  2. What size electric motor do I need and I asked a question march 26 th with no answer, as to other people got their questions answered

  3. I bought everything I needed for the conversion, the shaft is smaller with two wire wheels on each side, at a garage sale $75,00 all I have to do is get a longer shaft, thank you so much for posting that information, a cabbing machine is $1400 thanks again

    • Dave
    • March 22, 2022

    Hello Paul,
    thanks for getting in touch, unfortunately the company I got them from are no longer in business, I would suggest having a look at EBAY US sellers, or approach a local engineering company to see if they can some up for you.
    Best regards

    • Paul Green
    • March 21, 2022

    Hi, where did you get your flanges from I need a pair of 1/2 in inner diameter 2 inch overall size

    let me know


  4. Hi Stuart, thanks for dropping by, to answer your question I could have given you this list when I built the machine but sadly ABC polishing who did the machining on the shaft for me and also supplied the flanges are no longer in business. The expanding wheels were obtained from https://lapidarytool.com but I don’t see them on the site anymore. I guess you will have to do some research on the net to find suppliers and look for a small engineering firm local to you who can machine your shaft for you.
    Sorry I couldn’t be more helpful

  5. Hi Dave,
    I am Stuart can you give me a list please of materials for the machine and where can i purchase them please.


    • Dave
    • August 2, 2017

    Hi Kim,
    thanks for dropping by, to answer your question, the pulley has a grub screw fitted in it which bites into the shaft to stop the pulley slipping, I have inserted an image to show it. The shaft itself is just a round shaft over its whole length apart from the threaded ends.
    Picture of the grub screw in the pulley:
    picture of pulley showing grub screw

    I hope this helps, any other questions just give me shout, and good luck with your build

    • Kim Fulk
    • August 2, 2017


    My name is Kim and am planning a DIY cab machine build. I was wondering how do you keep the pulley from slipping on the shaft, is there a set screw on the pulley and is the shaft a D shaft, or shaft with a flat side to it. Any help and more detailed explanation would greatly help.


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