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Gemstone Faceting / Re: Any Graves 5XL owners in Tassie?
« on: March 23, 2019, 12:04:12 AM »
Hi Mehoose,

if you have a target dop, put it in your 45 degree dop and with the angle set at 45 degrees adjust the cheeter and angle until the target dop is flat on the lap.  This is really to get your table flat, but should help zero the cheeter.

if the cheeter is not zero, the number is zero.

there is also info on "sighting the rifle" which is worth looking up.  It looks the most accurate.

lastly, cut a row of witness facets before you transfer the stone.  After transferring, polish one.  If you have to, adjust the cheeter until the witness facet polishes evenly, then cut the crown.

The advantage of witness facets is that you don't waste tome po.ishing large girdle facets then to only cut most of them away.

happy faceting.

Gemstone Faceting / Re: TV glass toxicity?
« on: March 08, 2019, 07:52:45 PM »
I wouldnt put it in the chook run or on the vegi gardes, no point in eating glow in the dark eggs and veg.

But the flower garden, mmmm fluoro flowers may look pretty.

Hi Giel,

All machines have a mechanism that alligned the dop with the centre of the cutter so you can allign the direction of the cut to the stone and lift and inspect the work then return it to the same allignment as cutting progresses.  The VJ has a micrometer screw guage that clamps onto the swivell for the quadrant mast.  Thes system wont work for a mast machine like a Facetron.

The Polymetric uses a quill stop to achieve allignment.  Ive used something similar. 

I tried to concave the mains on an SRB on a machine where the mast base was 3mm out if allignment with the cutter but the stone was centred on the cutter, the meets didn't line up.

If the cutter gets off centre to the stone, it is the same as rotating the stone on the dop.

This is why I set out to adjust the front/back positioning of the cutter.  But you also need a stop to ensure that the Quill stays in the same side to side plane as the cutter, albeit above the cutter.

Hi All,

I had a Zircon on the dop that had a crack in the crown.  I gave up trying to recut the crown and instead opted to concave cut the side facets on the Crown to cut away the fracture.  The stone was an Old Mine  cushion cut with facets at 95, 1, 23,25, etc.

It's the first run of my concave cutter.  I found the following. 

Allignment of the cutter to the centre of the mast was critical.  Next time I'll opt for micrometer screw gages for mast alignment and mast stop alignment.

I am still learning how to accurately allign my cutter.  It seems that with close indexes, imperceptable changes (less than 0.25mm) makes a big difference to the position of the facets.  My laser level is just too course for that job.


Gemstone Faceting / Re: choosing the right electromotor, please help.
« on: February 28, 2019, 06:50:51 PM »
It sounds like you are on the right track.

I have just ordered a dial indicator on a magnetic base like you would use on a lathe to centre the job.  It is so I can use it for trouble shooting and for checking the run out on my cutting mandrels.

Gemstone Faceting / Re: choosing the right electromotor, please help.
« on: February 26, 2019, 07:20:57 PM »
Hi Geil,

Sounds good.  I used a cross slide coupled to a thread so I can manually adjust the position of the cutting mandrel so it is centred on the axis running up the centre of the quill.

I think this is what you are talking about in  relation to the cross table allowing parrallel concave facets.

55mm maximum oscillation would require rather long cutting mandrels and runout could be a problem. 

If you can adjust the length if the oscillation, that would be good.

The length of oscillation should be a couple of mm shorter than the length of your cutting mandrel minus the maximum length of the facet you will be cutting, otherwise the edge of the mandrel may run on the face of the stone and mar it.

Regards Gordon

Gemstone Faceting / Re: choosing the right electromotor, please help.
« on: February 24, 2019, 08:58:15 AM »
Hi Makky,

Do you mean that you were using linear bearings on the oscillator threaded rod?  I didn't think they would work very well with a rotating shaft in them.

The 6mm pitch threaded rod assembly I bought as a kit from Banggood has pillow block bearings at each end.  The bearings are mounted in a ball like housing allowing the bearing to be off up to 5 to 10 degrees perpendicular to the mountings. 

The 2nd one I mounted wasn't true, but it was just a case of putting the rod into the bearing and twisting the bearing housing until it was properly aligned with the direction of the rod.


Gemstone Faceting / Re: choosing the right electromotor, please help.
« on: February 22, 2019, 09:14:58 AM »
Hi Makky,

The length of your cutting mandrels determines the distance between the max fsd and max backward stroke on the oscillator.  I have 3 settings, 30, 40 and 50mm  achieved using threaded holes on my oscillator arm at 15, 20 and 25mm from the centre of rotation.

My darkside mandrel made by gearloose is 42mm long so I'll provably have to use the 30mm setting so the dop stays under the entire facet.  But if cutting a long facet, say 15mm long, I would need to make another arm with throws of say 15 and 25mm.

Clarry Trevena makes dops up to 60mm long so the 50mm setting would be fine for facets under say 8mm long.

Stop press, I made the arm from 10x10 mild steel rod with the end cut to 5mm thick to accomodate a lock nut on the retaining bolt for the agm that pushes and pulls the assembly back and forwards.  The 5mm tapped holes are 5mm apart but drilled in a zig zag patten.  If I add a tab to the other side of the motor shaft I can add 3 more adjustments at 1/2 distances giving 6 settings at 5mm increments starting at 15mm throws.

Oscillation speed control is an advantage.  Really slow settings give you time to position the mandrel for checking allignment, etc.


Gemstone Faceting / Re: choosing the right electromotor, please help.
« on: February 20, 2019, 06:45:39 PM »
Hi Giel,

I'm envious of the mini lathe, although I don't know how precise it is.  I recommend getting a dial indicator on an arm with magnet base so you can check your work, etc. 

There are some great YouTube videos by Joe Pieczynski that talk about machining in terms dummies like me can understand.  In one, he shows you how to accurately center your job even if the chuck is off center.  He made something like a collett for the chuck.

Makky, I had discounted the extension tools for the ER11 etc as creating too much length.  BUT I hadn't thought of mounting the shaft in a sintered bronze bearing with oil hole and driving the shaft.  This would certainly get rid of the runout resulting from mounting a collet holder on the motor shaft.  But it would require a close fit with the bearings. 

Mounting the motor behind the shaft with a flexible coupling would add length, it may be better to drive the shaft with a belt like the Polymetric concave facetor does.


Gemstone Faceting / Re: TV glass toxicity?
« on: February 11, 2019, 08:57:26 AM »

Re Radium Girls,

TRUE, alpha particles were to blame.  But they were pointing their paint brushes on their lips.  As a result they ingested a fair amount of radium.

The dosage and where it is applied is the key.  Swallowing large amouts of alphs emitters will eat you from the inside, as well as poison you.

Leave same in contact with your skin, and you get burns there, as you would if you sunbaked a spot way too long. 

In both instances there's also the increased risk of cancer. 

But there is a background level of alpha particles floating around that we take for granted.

I'm not advocating we eat the dust,  but basic hygene measures, including cleaning your machine should be sufficient protection for the small amount we would be likely to cut.


Gemstone Faceting / Re: TV glass toxicity?
« on: February 08, 2019, 07:11:34 PM »
I don't think I would be all that worried about faceting lead glass, really how much contact do you have with the lead glass or its slurry when faceting.
I have seen some interesting stones cut from Uranium glass, I don't reckon I would do it though,  that's a bit risky. Swallow a speck of that and you might have Alpha particles zapping through your body, nah.

What are you worried about, our new airconditioner and ozone generators basically generate them as antibacterial agents.  Alpha particles are generally hydrogen irons wizzing through the air instead of being in solution.  They don't last long.

Its the heavy metal poisoning from uranium that is worse.

Gemstone Faceting / Re: choosing the right electromotor, please help.
« on: February 08, 2019, 07:04:28 PM »
Agree.  Preloading should also help with runout.

If I had a lathe, I would set up the motor separately from the oscillating shaft and run it via a belt.  This would allow the motor to be changed or upgraded easily.  A similar concept to the VJ but without the flex drive and using a separate oscillator driver so it cant be oscillated too fast.

Basically 2 linear bearungs holding a tube bearing which osillates using a yoke that pushes and pulls a flange or tab on the tube.  A keyed pulley mounted between guide bearings to keep it stationary with respect to the base and a shaft running through the pulley with flanges each side of the tube so the tube bearing   pushes and pulls the central shaft.


Gemstone Faceting / Re: choosing the right electromotor, please help.
« on: February 08, 2019, 08:57:49 AM »
Hi Giel,

I dont have the specs on gand, but the more info tab under the picture of the motor on Banggood gives these specs.

Torque is also a function of motor speed, so you need one with good torque for cutting at low speeds.

Noise will also be a factor.  Motors for battery drills are quite noisy, too noisy for faceting.

The worm wheel drives the output shaft of the gearbox.  On my gearbox the shaft is 6mm od with a flat.  I drilled a 6mm hole in the end of a 10x10x60mm piece of mild steel, rotated 90 deg and drilled an offset hole for a tightening screw and split the end so it looks a bit like a battery terminal. 

Next time I wont do this, it requires too much pressure to clamp the arm to the shaft. Instead I'll just drill and tap a hole in the end, so I can screw a bolt straight down onto the flat on the shaft.

Then I split the rod so ut was 5mm wide except for the end with the hole, it stays as a 10x10x10mm bloc, and drilled and tapped 3 holes for 5mm bolts at, 15mm, 20mm and 25mm from the centre of the 6mm hole. These are mounting holes for the 5mm tie rod ends I use as a shaft.   They give a throw of 30  40, and 50mm respectively.

The tie rod ends are from Banggood, 1 male and 1 female + a tightening nut so I can adjust the length and position the end point of the oscillation.  They have a swivvel bearing at their end.

I'm wondering if bush bearings would be better than ball bearings when accuracy is required,  a small amount of oil on the bearings would remove the play.

Motion Dynamice make

Gemstone Faceting / Re: choosing the right electromotor, please help.
« on: February 06, 2019, 07:06:41 PM »
Hi Makky, I would first check the motor is wired for 50hz.  At one point the Gyroc burnisher/vibratory tumbler was sold with a 220v 60hz motor.  They ran so hot the thetmal cut out would trip.

Regards Gordon.

Gemstone Faceting / Re: choosing the right electromotor, please help.
« on: February 06, 2019, 09:02:19 AM »
Hi, just saw this post.

Have finished my machine, the little chinese 12v, 3500rpm fan cooled 775  motor from Banggood is quiet and draws no more than 3 amps.  My 25 amp power supply is a  it of overkill but can also br used for other projects as well.

The 30rpm worm drive motor is small but does the job. It is quiter is turned down, and I think this will make it last longer.

I have only been using the dial indicator on my faceting machine so the readings are in knotches, because the 0.00005 inch grads are not calibrated.

I was getting 5 graduations run out on the mandrel with the ER11A collet holder sitting straight on the shadmft of the motor.

An engineer I know suggested sleaving the ER11A and shrinking it on the motor shaft., but there may also be runout in the cone that holds the collet.

Not having a lathe I milled some copper shims until they fitted between the ER11A and the motor shaft.  The copper was about 0.025mm by this time.  E.g. there is about 0.05mm difference between motor shaft and the hole it fits in.

The hole narrows enough to stop the shaft going all thecway home when a tube of the shim is inserted all the way into the hole.  I cut the shim so it stopped just before the narrowing, meaning the shim tube was amout 9mm long.

I also placed the collet on a dop in my quill, wrapped 1200 sandpaper around it and at 90 degrees, ground the inside of the taper with the motor running, oscillator off, to smooth it.

This reduced the run out to 2 graduations on the dial indicator, about the same run out when sweeping a worn lap.

Am now waiting on some cutting mandrels to be made.  So I can start cutting.

Long story short.  I'm pretty happy with the result since including the 2 Darkside polishing mandrels I bought for about $100 with postage it has cost me under $500 to make.


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