faceting machine digital microscope setup

[Faceting Frank]

(follows on from https://aussielapidaryforum.com/forum/index.php?topic=6785.45)

Will start a new thread on my scope.

This is the latest on my scope setup.
Made a new mast from 12mm plywood 500mm high, needed the slot to go that high. Kept the same dressed timber boom, but extended the slot. The small piece of wood under the boom is a guide to maintaining the boom angle.
The boom angle is relevant to the facet angle and to get that I put my magnetic based digital protractor on the boom and roughly set it up. Because the protractor is heavy it has to come off and the small piece of wood is set at that angle. Then I can setup the boom accurately knowing I still have the correct angle.
Made a more robust base out of aluminium for the mast, made the fine adjustment setup at the end of the boom out of an old 7mm thick chopping board. Have a mill/drill so could mill all the parts so they were accurate.
 Having it made out of light weight material makes it a lot easier to move it into position while just looking at the screen.
The white labels I’ve stuck on it let me mark homing positions for the facets and they will come off when the stone is finished.
Still using whatever I find laying around to make it.

The angle the scope is pointing inward from the boom is about 45deg, there may be a more optimal angle than that. Its to do with keeping the mast height and boom length down in size.

[Faceting Frank]

Scrapped the plywood mast and made a new one out of MDF. Everything was working fine till I changed laps, then the screen started to blur a bit at mid plus speeds. Would be fine if I held the mast, never had this problem with my old MDF mast. 

[Faceting Frank]

Thought I would add a couple of pics from my old thread to this one. These are the stone at the 1200 grit stage and polished, the stone is a C Z 11mm dia. And the cut is a standard brilliant crown.

[Faceting Frank]

The stone I’m cutting now is a much more difficult cut and the view is looking at the pavilion with a sloping girdle. This is at the 1200 grit stage. The facets A, B, C, are only one index away from each other, the same goes for the girdle facets D and E. Have cut D and cutting E to meet up with the meet point between A and B.
One of the problems I’ve had from the very beginning of using a scope to facet with is getting the light just right so I can easily see the facet edges. Experimented with a few things and this is easily the best. Rubbing the stone with a 2B pencil, no side light, just daylight and the scope light.
To give you an idea of the scale of this, the computer screen is 380mm across and you’re looking at one half of stone 13mm wide.

[MakkyBrown]

Can you turn the microscope light off and use another directional light source, that might help.
MB

[Faceting Frank]

A light coming from the side or above as you would normally have when faceting works in most cases because the index differences are sufficient to show you the facets. As in the 1200 grit picture of the standard brilliant. They clearly stand out and you can make accurate meet points.
No good when the indexes are only one apart because the light does not pick up the facet edges. I don't know why the pencil shows the facet edges so clearly, but it does and a light from the side stuffs it up. This is all new to me, so its a case of solving problems when they come up.

[Faceting Frank]

Figured out how to put my rip-off light to use and quite impressed with it now. The stone in the two pictures has a sloping girdle, the colour is the stones natural colour. Don’t know why daylight made it look purple in the previous picture.
The stone is corundum and the facets have been pre-polished with 3k on a BATT lap, the light is angled to show the scratches and facer A is to be polished deep enough for the girdle. The white dots are the 1200 grit pits under the pre-polish and the other white stuff is bits of tissue.

[Faceting Frank]

And the white dot in the polished area is the computer curser.

[MakkyBrown]

Looking very good Frank, that is about as good as you'll ever need.

MB

[Faceting Frank]

That would probably be good enough to put in a display cabinet MB. It all looks good on the screen when the end of the scope is only 20mm from the stone.
But the problem is that on the bigger facets the scope has to be far enough away to be able to see the entire facet, which on this stone is 80mm out. That way I can see that all the pre-polish scratches are removed and no added scratches from the polishing lap.
 But that’s too far out to make accurate meet points, so I will be adding to the X, Y, axis fine adjustment setup I have at the end of the boom a 100mm deep Z axis adjustment.
This will allow me once that facet is polished, to zoom in on the meet points of that facet to check them out.

[Faceting Frank]

Found that whiteboard markers are great for showing the facet edges at the polishing stage. I think the thin ink runs off the facet edges before it dries.
These facets are only one index apart.

[Faceting Frank]

My mini lamp is working well clamped to the mast, I can get the angle just right to show up the facet surfaces on the screen.
Still a long way to go with the scope fine adjustment X Y Z axis setup. When I get it sorted will make it out of ally T bar slider, plus will have to have the scope pivot 20deg above and below the facet angle. This will make it a lot easier to checkout meet points.

[Faceting Frank]

As I said in my last post once I got the fine adjustments sorted, I would build a new setup out of T bar slider. Its ideal for this application because I can slide it back and forth with my thumb while looking at the screen and lock it in position with a finger tightened nylon bolt.
Nylon because it wont damage the ally bar and because the way the slider is made it will lock solid with minimal pressure.
2/3 the way through making this and will start to post more about it in detail shortly.

[RoughCreations]

As I said in my last post once I got the fine adjustments sorted, I would build a new setup out of T bar slider. Its ideal for this application because I can slide it back and forth with my thumb while looking at the screen and lock it in position with a finger tightened nylon bolt.
Nylon because it wont damage the ally bar and because the way the slider is made it will lock solid with minimal pressure.
2/3 the way through making this and will start to post more about it in detail shortly.

Hi Frank,
This is a great topic. Where did you get the T-bar slider material? Is it re-purposed?
Thanks,
RC

[Faceting Frank]

There is, mountains of the stuff on eBay, from sellers in both Sydney and Melbourne. From what I’ve seen its mostly used on woodworking saw bench tops, with the rail set into the bench top and a stop fitted to the sliders.