A new Diamond Cabochon machine – conclusion

The finished cabochon machine
The finished cabochon machine

Over the last two days I completed the build of this new machine. As it’s a clean machine as explained in my last post, it won’t need drip trays to collects water or anything like that, so it was decided that the machine would be mounted direct to the bench in a static position. This cut down on material costs as I didn’t have to construct a top, back and base for the machine as the bench top would be the base of the machine.

Note: in case you missed part 1 of this build you can find it here:


Bearing mounting blocks
Bearing mounting blocks

The first job was to cut two blocks to mount the bearings on which I got from my scrap wood pile which would otherwise have been destined for burning next winter in the fireplace.

The two blocks were positioned on the bench top and then wood glue was applied for extra strength and a couple of screws were put in from underneath the bench to pull the joint nice and tight and hold the blocks in place.

The next job was to place the bearings and shaft assembly on the blocks and position them, these were temporarily held in place with four long wood screws. Now I slackened off the grub screws in the bearings and the pulley, so I could get the shaft in the correct position, i.e. equal lengths on each side, once that was right the grub screws were clamped up.

Now I removed one of the four wood screws, leaving three in to hold everything in place while I drilled the first hole for the bolt that would go from underneath the bench top up to the top of the bearing, I did these one by one, fitting a bolt as soon as a hole had been drilled. By doing it this way everything stays in place and you can’t end up with a hole drilled in the wrong place. Yes it could be argued that by measuring everything accurately the same result could be achieved, but I believe by using the method I did then there is no chance of an error occurring.

Bearing mounting bolts
Bearing mounting bolts

So now we have the bearing and shaft assembly firmly secured to the blocks, at this point I realised my first mistake, I had forgotten to fit the V belt, but fortunately this was an easy omission to fix by simply unbolting it all, fitting the V belt and then bolting all back up again.

Aluminium shaft spacer tube
Aluminium shaft spacer tube

Next up was to make the spacers between the wheels, to do this I fitted all of the flanges and wheels and spaced them out how I wanted them, once I was happy with the spacing I marked the shaft against the edges of the flanges with a marker pen. Now all that remained was to remove all the wheels and flanges again and then take some measurements. The first measurement was between the face of the bearing and the first mark on the shaft, this would be the size of the first spacer.

Now I have got my spacer measurement, I went and cut the first two spacers, one for each side. I have used some aluminium tube for the spacers, it has an inside diameter of 26mm with a wall thickness of 3mm, so the dimension are pretty near perfect.

Aluminium end spacer tube
Aluminium end spacer tube

Right back to the shaft now and fitted the first two spacers, one each side butted up against the bearing face, then slid a flange on each side and then a wheel on each side, followed by a further flange. Now I took the next measurement for the next spacer which would go between the flanges. With next two spacers cut they were fitted onto the shaft on each side, followed by a flange each side then a wheel each side and then the final flange each side, and now it was time to measure the final two spacers. These I made a couple of mm longer than the measurement as I wanted to make sure everything gripped properly once tightened up.

Next I tightened the nuts at each end of the shaft and that was that stage of the job complete.

The next stage was to make the motor mount, this is just a lump of scrap wood again which the motor is bolted to.

Cabochon machine motor mount
Cabochon machine motor mount

When I built my first machine a few years ago I spent quite a while working out how I could make a motor mount that was adjustable to take account of any belt stretching that might occur and still be able to maintain a good belt tension. The result of deliberations again came from my scrap box which can be seen in the photo. I think this metal is called Dexion, but the fact that it has long slots in it gave me the answers to my initial problem.

So as you can see, the metal is screwed into the wooden block that the motor is mounted on. Then I placed the motor in position and put the V belt round the motor pulley and got everything lined up and then marked four holes in the bench top. These would be for the four blots that would go through the long slots in the metal. With the holes drilled, the bolts were glued in place from underneath and then the motor was put in place and wing nuts screwed onto the blots, and there you, my simple adjustable motor mount and it really works!

Now I took the time to check everything was secure and tight before firing the machine up for the first time. I almost forgot to mention that you must never run expanding drums without belts fitted.

So here we go, with on time and blast off, I was horrified to see that the whole thing vibrated like mad on initial power up.

I soon realised it wasn’t the machine that was at fault, it was the bench, it was too flimsy, the bench top was bending under the inertia of those wheels spinning up.

Bench stiffening blocks
Bench top stiffening blocks


So now the bench had to be stiffened up considerably, back to the scrap wood were I five lengths of wood, two of these would be screwed under the bench top as close the bearing bolts as possible, once theses were fitted the bench top was much less flimsy. But, and there always is a “but” isn’t there, I realised that the bench legs were not secured to the floor of the workshop and that this would allow some vibrating so that would need addressing too.


The bench legs
The bench leg modifications

So take a look at this photo to see what I did, the white bit of wood was screwed into the floor, and then the legs were cut to fit. The legs and the wood on the floor are screwed together from underneath and then more screws go into the legs from the top of the bench and now I happy to say that there is no vibration at all when the machine is started up.[benchlegs]

The four wheels are fitted with REZ belts, these are resin impregnated belts which have the diamond paste applied to them.

We will be using the following grades of diamond on the belts 28, 7, 2.5 and 0.5 micron which should give us a good coverage to follow on from the 600 grit silicon carbide belt on the other machine.

We got a very good result on a piece of lapis last year when we used the 0.5 paste, a result I couldn’t get with cerium oxide, so maybe we won’t be using cerium oxide very much in the future.

Our next job will to be to build a similar machine, but this will be a wet machine for the silicon carbide belts, but we will have to save up again to afford the expanding drums!

I hope you have enjoyed this

All the best


A new Diamond Cabochon machine part 1

A new addition to our stable of homemade Lapidary machines, this one will be a 4 wheel cabochon machine using for rubber expanding drums fitted with REZ belts which will be charged with diamond paste of different mesh.

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.



Evans CR2 Tumbler Cleaning

We have been running 2 Evans CR2 tumbling machines for almost a year now, but we have had a few problems with them in that they would stall and stop without warning.

We have been running 2 Evans CR2 tumbling machines for almost a year now, but we have had a few problems with them in that they would stall and stop without warning.

We followed the instructions to the letter regarding oiling and cleaning but that still did not sort out the problem.

Eventually the machines were returned to the manufacturer for repair and they seemed fine after we got them back, but then the old problem arose again.

I spoke to the manufacturer again and it was during this conversation that I learned something vital relating to the cleaning and oiling process.

He told me that the idle shaft, the non driven shaft should have some play in it, meaning that you should be able to move it back and forth when its fitted, our had no movement at all and the shaft was very stiff indeed so it was effectively acting as a brake.

The manufacturer told me how to remove this shaft and how to clean it properly, information that didn’t appear in the instructions.

This is what I learnt from him:

At the opposite end to the motor box is a mounting flange, you need to gently pull this backwards which will allow you to pull the shaft out along with the bearing:

Removing the tumbler idle shaft from the main chassis

Once you have the shaft removed pull the bearings off each end, they may be difficult to get off so a squirt of WD40 helps with this:

Pull the bearing from the shaft

Once you have got the bearing you may well find a lot of muck on the end of the shaft, this needs to be thoroughly cleaned as must the inside of the bearing as well.

Once you have done this put a good bit of oil into the bearing and then refit the shaft.

We find we need to repeat this process on a fairly regular basis to keep the machines running properly

Lapidary Workshop Rebuilt

We have been talking for quite while now about rebuilding our Lapidary workshop in order to make it more efficient

Lapidary Workshop Rebuilt

We have been talking for quite while now about rebuilding our Lapidary workshop in order to make it more efficient and get it all into one area so we finally did it over the last bank holiday weekend, it took about 2 days to complete.

The other reason for doing this was that we wanted to have the workshop enclosed so that the warmth from the wood burner won’t be lost and we will then be able to work out there during the winter as well.

All of the worktops are made from 12mm marine ply which have had numerous coats of clear varnish applied.

So here are a few pictures of were we live!

The rock drill area:

We use a fordom SR series felxi shaft set up which serves our needs admirably, our drill bit are triple ripple bits for the smaller holes and then we use diamond coated bits to open the holes up to about 2.5mm which is fine for threading leather thong through.

This is our rock drilling area, we use a Foredom drill imported from the USA

The rock tumbler area:

Our tumbling equipment is made by Evans and Beech in the UK, the larger ones are the Evans CR2 tumbler machines and all of the barrels ae now rubber, made by Evans, it’s great now we have switched to rubber barrels and got rid of the plastic barrels, we can now hear ourselves think!

The rock tumbling area

Busy Rock Tumblers:

Here are both of the tumblers in action

Here are the four rock tumblers doing their stuff

The cabochon machine and polishing area:

This is our homemade cabochon machine and polisher, the polisher shares the saw.grinder motor, we just swap the drive belts, works just fine. We use cerium oxide polish on a felt pad and it works fine almost all our rocks.

Cabachon machine and polishing area

The rock saw area:

This is the rock saw and grinder combo machine, built way back when by PMR, it was bought second hand from Ebay about 2 years ago and has served us well, it has an 8″ saw blade and a lthal 8″ silcon carbide wheel which really eat finger ends if you are not careful!

This is the rock saw and grinder combo machine



Our Home Made Cabachon Machine

Welcome to our article abut how we built our homemade cabochon machine, in all it cost about £250.00 including wheels, motor and shaft and everything else that went into it.

Here is a picture of the complete machine as you can see it’s relatively compact, none too pretty but it does the job.

our home made cabachon machine

The whole thing is made of marine ply, we used a 4’ x 2’ x ½” sheet.

First we cut a 2’ x 2’ piece to make the base, then used the rest to make the back and top.

We used two wooden blocks to raise the shaft sufficiently to allow for clearance when the wheels were fitted to the shaft.

Here is a picture of the shaft as supplied to us

Picture showing the shaft and pulleys

The frame is made from bits of wood we had lying around in the workshop mainly 2” x 1/2”.

Next we cut a hole in the back sheet to allow for the drive belt to pass through to the motor , once this was done we made a frame across the base to secure the back sheet to.

The hole for the drive belt

Next we mounted the shaft in place on the base sheet, all marking out and measuring was done using the mark1 eyeball, nothing technical here!

Once this was mounted we constructed a box type arrangement around the pulley area on the shaft to protect it from all the water and muck. (see the preceeding picture)

Then we mounted the motor at the back of the base on rails to allow for belt tension adjustment, this can be clearly seen below:

The motor mount

Now to the boring bit, we gave it many coats of exterior paint and after they had fully dried we applied a coat of plastidip wherever we could, just to make everything waterproof and completely seal all joints.

We have two wheels mounted on the shaft, one is an 8” x 2” 100 grit diamond wheel, this thing is ferocious, and really shapes rock quickly, also does a good job on finger ends as well if you are not careful!

The diamond grinding wheel

On the other end of the shaft we have mounted an 8” x 3” expanding rubber drum,

The expanding rubber drum

We slip silicon carbide sanding belts over this covering all the various grits that we need (belts pic)
We opted for the 8” diameter wheels simply because we wanted the maximum grinding area width that we could get, this set up would work equally well with 6” wheels as well.

Ongoing things to sort out with the design:

1. a good water supply set up that wets the whole width of the wheels
2. should have made the lower splash tray at the front a few inches bigger so that it catches all of the spray from the wheels.


Sources of supply for the major components:

The shaft was purchased from ABC polishing, it’s called the polishing spindle and can be found at:


The motor was purchased from Tony at Goldcrest Technologies, you can find his shop on E-bay here:


And the motor description is as follows:

Electric Motor Single Phase 0.25kw 1400rpm (Made in EU)

Note: these motors are really good, when we are cutting and polishing they run for a good 8 hours a day with no complaints.

The expanding wheel cam from Manchester Minerals who can be found here:


The drum we used is part number on the above page: Ref: 17-047

The belts also came from this supplier and can be found on the same page under part number: Ref: SiCBelts

The diamond wheel came from an Ebay seller in the US, but you could also use a silicone carbide wheel which are supplied by Manchester Minerals as well on the same page under ref no: Ref: SiCWheels

The Plastidip paint we used can be found at http://www.plastidip.co.uk

Here are a few pics of how I have mounted the motor, byt using Dexion plate it allows me to move the motor back and forth to get a good tension on the pulley belt:

Alan asked if I needed to modify the spindle to accept the wheel, well there was no modification needed, I hope the pictures below help in understanding:

This is the spindle I purchased from ABC Polishing:

Cabochon Machine Spindle
Cabochon Machine Spindle

A Close up of the Left Wheel:

Close up of left wheel spindle
Close up of left wheel spindle

A close up of the Right Wheel

Close up of right wheel spindle
Close up of right wheel spindle

Homemade Lapidary Equipment

The cabachon machine has seen quite a lot of service since it was built last summer and has stood up to the test of time so far

This weekend I will be taking some pictures of our homemade cabachon machine and writing an artcile on how we made it. This will also include details of Uk suppliers where I managed to obtain the parts to make the machine.

The cabachon machine has seen quite a lot of service since it was built last summer and has stood up to the test of time so far, we have ground, shaped and polished many types of semi-precious gemstone on the machine, including amethyst, sodalite, rose quartz, petrified wood, pebbles found in the fields and many more varieties with a large degree of success.

We also use the diamond grinding wheel on the machine to make pre forms for the tumblers.

It’s not a particularly pretty machine to look at when compared to the commercially available machines, but what we have lost in looks we have saved in terms of costs and nothing in functionality.

I will get the details posted over this weekend, plus make a start on cutting some of the black flint I recently found, it should polish up really well for use in the jewellery.