Old Prismatic faceting machine

[Debbie K]

After listening to me complain never-endingly about my more than 60 year old Graves faceting machine, a friend lent me his old Prismatic. I don't know if any of you guys are familiar with this type of machine.

Someone, not him or me, overtightened a nut at the top of the quill which made the cheater impossible to turn. I backed it off, and when I did the crack opened up. Now the cheater works, but not too terribly well.

The bearings are shot; and it's not obvious about how to disassemble the head from the mast to replace them. It takes one hand to move the head and the other to hold on to the stone.

I'm thinking about making him an offer on this machine; the protractor is huge and it has a fine tune angle adjustment which is really nice, too. The bed is pretty level, it's variable speed and overall seems like it'd be a really good machine if it didn't have these problems.

I have an idea about what this machine would sell for if it were fully functional. I don't know what he paid for it; he got it at an auction and never used it. Do you think I'd be foolish to attempt these repairs myself? If not, how much would you knock off the value to do these sort of repairs? There's a fellow here in the states how does repairs and I've already sent him an email to see what he would charge.

Here's a picture of the machine and the cheater.

Debbie K

 

[rough2cut]

You will need to send it to Horst on the sapphire fields,and have the broken part rebuilt.

 

[LONEWOLF]

Any 'Good' Engineering Shop should be able to fix it, and re-set everything... If they say 'What is it'... try another Shop...

LW...

 

[Gilly47]

WoW now that is a piece of engineering work

 

[Debbie K]

Thanks for the replies. I'm not sure if Horst is a company or a person, and what sapphire fields refers to.

In the meantime, while waiting for the guy who repairs/rebuilds these machines to reply, I loosened some more screws on the head collar and the head swings a little freer now; I can actually move it with one hand. Still feels stiff like it needs new bearings, but definitely better than before.

I also messed around with the nut that was originally overtightened, and the cheater seems to be working a little better too.

I'm going to try to cut another stone and see how it goes. I've done a pavilion already, and the cheater was erratic and difficult to control. I only needed to use the cheater when I moved the head up on the plate. When it's fixed, it's dead accurate.

Yeah, isn't it a cool machine? I hate to see things like this neglected and abused. It seems like I spend more time rehabbing and restoring machines than I do making things.

Until I hear back from the repair guy, I'm refraining from doing anything drastic. Any advice you guys have, especially if you've any experience with a machine like this, I'd love to hear.

Debbie K

 

[LONEWOLF]

With the reference to Sapphire fields and Horst(person), I think rough2cut thought you lived in Australia... Horst is a Person in the Central Gemfields of Queensland, Australia... :Y:

LW...

 

[Debbie K]

Well, it's official. The cheater is definitely an issue. I'm still waiting for the guy to email me back. I've gotten permission to attempt the repair myself but I'm holding off 'til I have more information.

If I could figure out how to get the quill and housing off, I think it would be fairly simple to fix. The right way would be to get a piece machined out of aluminum. The housing was the only piece of plastic on the whole machine, so of course it cracked. The easy way would be to epoxy it back together and reinforce it with a piece of sheet steel on the bottom; there's plenty of room and it wouldn't interfere at all with the function of the machine.

As it is now, I'm having to mark every facet to see how far the cheater is moving. I've gotten some interesting bent facets along the way, but it's too exhausting to work this way. I did manage to produce this amethyst, but I'm not real happy.

Debbie K

 

[rough2cut]

Now a few things make sense.

 

[Lefty]

I think I would probably take it to a professional to get repaired Debbie.

A faceting machine is an extreme high-precision piece of equipment and I would probably not attempt too many kinds of fixes myself, even if I were more engineering-minded. I am lucky enough to live only a few hours drive from the manufacturer of the first-class machine I own (a VJ). I picked it up from the "factory" myself and noted that the workshop where the machine was made looks more like the control panel of the Enterprise than a workshop!

While it can get frustrating at times, faceting should be a fun, enjoyable and rewarding experience overall. What you're having to do at present doesn't sound like much fun Get a pro to check it out.

 

[Debbie K]

Lefty:

Looked at VJ's website; what an interesting machine! The big protractor is great, and also being able to go from girdle to table.

I got impatient, still haven't heard back from the professional, and decided to try again to disassemble the quill from the head to get at the cheater worm gear housing. I have had it dripping Liquid Wrench for over a week and a lot of nothing was happening. I got to looking at it and something that I thought was a rivet was actually a Allen screw which had been filled in with epoxy. After using an eyedropper with acetone because I didn't dare soak it because the fumes would dissolve the plastic housing, after about an hour or so I was able to break the screw loose.

Interestingly enough, that wasn't how it came apart anyway. The whole thing was held together by a locking spring washer at the top of the quill mast under the index and a collar. It was so black with gunk I didn't notice the washer the first time around.

I got the housing off, epoxied it and reinforced it with a 18 gauge piece of sheet brass and reassembled it. When I tightened it up, it cracked again. So, I guess I'll be milling a housing myself, either out of aluminum or nylon. The housing also acts as a clamp so it must have flex and strength. Do any of you know if the nylon is able to be tapped and have allen screws used without stripping out? I have some steel, but I think the extra weight on the head would be a bad idea. For that matter, so was the plastic that was originally used.

Bored with it for now, and think I'll take a day or two off. I have a baby drill press and a mill base, and if I can figure out how to put them together, I'll be trying again. The guy it belongs to says I can have it, otherwise he was going to sell it for parts, so I may as well try to fix it. The good news is that I now know a lot about this assembly so if anyone else has a problem with a similar one I can tell them what I did.

Debbie K

 

[Lefty]

Not too sure about tapping nylon Debbie. But at least you're having a go - hopefully you can get it working yourself but if it continues to give trouble I would look for a professional as something might need to be re-calibrated.

Yes, the VJ is an excellent machine with some interesting concepts such as the platen that your cutting and polishing laps sit on raises up and down rather than the cutting head sliding up and down a mast. You can make accurate adjustments to the "height" of the cutting head relative to the lap to within 1/50th of a millimetre while using one hand. The really big protractor is the only downside - it's great in itself but as I get older and my midriff grows "more generous" the end of the protractor can get in the way at low angles. I have bumped it on my belly, snagged it on my shirt sleeve, elbow, forearm, hand and even my little finger. That's the only complaint I have though, everything else is spot on. It has a digital angle readout as an accessory but I don't use it - I get power fluctuations in my area and that interfered with it. The manual protractor is accurate and repeatable to easily within 1/10th of a degree and very close to 1/20th. I personally don't believe that there is any noticable difference between say 42.25 degrees and 42.26 degrees - these increments are in practical reality so tiny that any difference is going to move during polishing anyway. If you have a good, accurate manual protractor, the digital readout is unnecessary.

Don't get me wrong, there's nothing wrong with having the electronics as long as they're reliable - I saw a commercial cutter over your way who had a machine with a depth gauge that beeps, allowing him to facet very quickly to what he says is a reasonable degree of accuracy.

Mr Magoo had a really good idea as well - a microphone attachment to amplify the sound of cutting for those who cut by ear (such as myself) and whose hearing is no longer what it once was.

So don't feel that a machine is inferior just because it doesn't have any electronic components - a good cutter will still turn out excellent stones on a precisely-built and calibrated manual system.

Cheers

 

[Debbie K]

The Prismatic has a fine tune adjustment knob for the angle, along with the big protractor. I've already marked it in pencil for 1/10's of a degree. This is one of the reasons I'm so interested in this machine. If it were working properly it would be extremely accurate. The bed seems pretty level; much better than my Graves. The up/down dial for height adjustment is really accurate, too. And, it can be adjusted for left/right shift.

The mast arrangement makes for very little flex. When I cut this amethyst, it was almost impossible to press it past the set angle. The Graves would allow me to press down on the stone to cut a little further, but not this machine. I have to lower the mast.

I could cast a housing in bronze, but I think it would be too heavy. I suppose that's why they went with plastic, which is why I'm thinking aluminum or nylon. I am determined to get it fixed; it's just too nice of a machine to be sold for parts. The only thing really poorly designed is the light; there's no way to place it where it does you any good. It needs to be moved to the other side of the machine entirely.

I've heard about the Beale/Woolley Depth of Cut Indicator which can be retrofit on these old machines, but until overcutting seems to be an issue I'm holding off. Right now I'm more concerned about accuracy of angle and looking at the digital readout options to retrofit on this machine. There's a faceting group in my city that meets once a month, and I plan to go to ask about how I might do this. I haven't gone yet because I don't know what I'm doing and it's kinda embarrassing to go somewhere and not even know what questions to ask with ill-cut, poorly polished stones. There is one older man who goes who said he'd help me, and I think I'll go to their next meeting with the machine and ask what he'd do.

Another friend has a Ultra Tec fantasy concave cutter, and we plan to make some stones. I'm trying to cut some large amethyst as a base to use on this cutter. I've made my own manual version of an x y z axis cutter, but I need to work on it's accuracy. I'm not smart enough to incorporate all the electronics, but I'm good at figuring out purely mechanical things.

I'm getting older, and always figured that when my hands get too arthritic to carve I'd take up faceting. Most of my rough is facet grade already, and I have enough to work on for 2 or 3 lifetimes. Folks think that rough that isn't good enough to be facet grade is good enough for carving, but that is not the case. You can't have cracks or too many inclusions, just like faceting. I'm still able to carve, but the writing's on the wall.

Thank all of you to helping this newbie. I'll keep you guys posted on the progress of the restoration process.

Debbie K

 

[Debbie K]

Just to let you guys know, I havent given up on faceting. I live in Houston, Texas, and we had a hurricane that came thru about 3 weeks ago and flooded much of the city. Between water in my studio and my best friends house getting 2 feet of water, Ive been too busy to work on my machine. Its depressing around here, and difficult to get motivated with any new project. Every time it rains we all are collectively holding our breaths hoping that we dont get an apocalyptic flood again. They say we got 51 inches in my part of town; some got as much as 57. Im so lucky that I didnt get water in my house; it came all the way up to the front and back doors but not in.

The man that was going to help me with his milling machine had problems, too, so I decided to go ahead and make a replacement part out of Delrin plastic. All I had to work with is a borrowed bandsaw and a baby drill press and a Foredom and hand tools. I also had a 4 mm tap, so decided to make all the allen screws the same size.

It looks like crap but it works like a dream. When I took the broken piece off it didnt appear that the tolerances were critical, except the distance between the worm gear and the gear on another piece. Even that part had a little play, as there is a spring that pushes the worm gear up to engage the teeth on the other part with the gear. I took a cigarette lighter apart and got the flint spring out and cut off a piece to use and it seems to work fine.

I faceted a stone yesterday, and although the cheater works now, it became apparent that the brake is slipping almost every time the quill was lowered to it's fullest extent. I can get it to hold my using pliers and tightening the heck out of it, but that's not really practical in use. I think that the circular clamp that is the brake is worn down where it holds to the quill shaft; hence the overtightening. It seems to me that it's not really a very good design in the first place, and I'm thinking about making something like what my Graves machine has where the break is part of the protractor.

Here's a picture of the old part, the new one on the machine and my latest stone. The pavillion angles are off on the stone because: a. I couldn't find my notes, b. I was using and different index, c. I'm just not that good of a facetor. But my polishing is getting better! I've found that on the quartz I've been doing I can go from 600 to 3000 and then to cerium and it looks better than what I was doing before.

I post all of this so folks who have a machine like mine won't be so afraid to do something with it. I figure if it's already broken and unusable I can't really make it worse, if I'm careful.

Debbie K

 

[LONEWOLF]

A Very nice way to help you get over what has happened to you over there. :brokenh: .. Mother Nature can be Cruel sometimes. 8.( . We All feel for you... Us Queenslanders Know how Devastating such a powerful thing Hurricanes can be... We call them Cyclones in the southern hemisphere and have had a few in the past few years.. Cheer up and get into your Faceting... The stone you cut looks good to me, but I have never faceted, so anything looks good to me. .. Glad you have sorted out your Machine... And looking forward to seeing more of your work on here... :Y:

LW...

 

[Debbie K]

It turns out that the brake was fairly easy to fix. I got the shop foreman at my local gem and mineral club to help me analyze how best to fix it, and we tried the simplest things first. I got a large thumbscrew which enabled me to apply a little more torque to tighten it, and we roughed up the shaft that the brake rotated on with a nail set which raised and lowered the metal on the mild steel shaft. Now it's possible to tighten it without it slipping.

Debbie K

 

[NeilM]

Hi Debbie K.

Great work. Persistence paid off.
It is not just the gemstone faceters interested in your story.

Keep the piccies and story going..

Neil

 

[johnful]

Interesting project.

I too have an old Prismatic Accura-flex very similar to the one in the picture. I inherited it some years ago. The motor finally gave out. The motor had no markings, but I was able to deduce from the motor driver that it was a 90v DC PM TENV motor. The two choices I could find were an exact fit:

Dayton 3xe22

Leeson M111014

The Dayton is 1800 RPM and the Leeson is 3500 RPM. I'm able to get the Dayton next day locally, so I'll try that first. The motor driver is a Minarik MA652. It's an older style SCR variable speed motor driver. Mine is 110v, and the one pictured in this forum is likely 220v. You can, however, start with the part numbers here to get to the 220v (for the motor driver) and 180v (for the motor) equivalents.

Other than that mishap, the machine is in pretty good shape. I have faceted probably 200 stones on it. Recently there seems to be a little play in the height adjustment at the top of the mast, but nothing appears to be outright broken. I'll get a chance this weekend to disassemble and inspect closely.

Also, about 2 years ago, I was hunting for the tapered rubber drive cone. It turns out that Zane over at Polymetric used to apprentice for Prismatic years ago. He sometimes has spare parts or can point you to where to find them. I got the drive cone and a full set of index gears from him.

I'll post some pictures as soon as I get the new motor installed.

J

 

[Debbie K]

J:

Zane's dad was the maker of the old Prismatic machines. He still makes and stocks many of the old parts. I just couldn't afford the new cheater at the time which is why I made one. If anyone every needs to get in touch with him, call rather than email. He's a nice guy and helpful.

Mine's a 110v too. Not sure what kind of motor; since that was working well there was no reason to unbolt it and turn it upside down, but good to know that the motor can be replaced.

Odd about the slop with the height adjustment. Mine is very solid. Have you tried tightening the allen screws on the all thread side of the mast?

By the way, the brake for the protractor issue is not resolved; the dimples on the axle worked for a while but as I continued to use it they worn down. The larger thumbscrew interfered with tilting the head back to view the stone, also. So the next thing I'm going to try is replacing some of the worn down aluminum with a really thin coat of JB Weld, the metal epoxy stuff that we use to repair radiators and metal things. I'll let you guys know if it works.

Debbie K

 

[johnful]

Hi Debbie,

The motor was the Leeson one. Zane said it was used as a replacement for the original, so this must be the third motor for this old machine.

This is a picture of the mast.

 

[Debbie K]

I'm having problems having anything I submit posting, so if the others show up, forgive me for the repetition.

Please post photos when you replace your motor. I'm hoping that this thread will help others in the future repairing their Prismatics. There's very little information about these faceting machines.

Have you tried tightening the two allen screws where the head hooks into the all thread? I had the opposite problem, practically every screw had been overtightened and nothing would move freely except the broken cheater and the slipping brake.

Good luck!

Debbie K