My GO Post

I originally posted this review of the Omni Faceting Machine on the GemologyOnline Forum on January 4, 2008. This is before I started working on aligning my Omni. You can tell I have a different opinion of the Omni at this point.

Based on what I have discovered since this post during my disassembly of my Omni Faceting Machine, I retract my final comments.

I would NEVER buy an Omni Faceting Machine again nor recommend it to anyone.

You can read the original post here.

Posted: Fri Jan 04, 2008 3:09 am

Post subject: First-hand Omni-E Experience

I own an Omni-E and have had it for about 6 months. I have not cut a huge number of stones on it, but I have cut at least 15 in that time. They have ranged from a couple of matched pairs of 3.5mm Peridot, to a 10mm blood-red Pyrope garnet, to a large 15mm+ Citrine.

As a disclaimer, I do not have any financial interests in any faceting company, I don’t sell any faceting machines or accessories, and for the record I’m machine-agnostic. I just want something that does what I want it to, and to do it well for a reasonable price. I do not want to start the “machine wars” here!

I formerly had an old MDR 102 from the early 80s. I had every index wheel I needed (32, 64, 80, 96, 120) and at least 40 different dops in brass and aluminum. I bought this machine used from an old acquaintance and used it for a number of years with reasonable success. I finally realized that I was spending at least as much time fighting the idiosyncracies of the machine as I was cutting stones, and wanted something that was newer. I am not knocking the MDR – that machine served me well over the years and I learned a lot about faceting during that time. And there are times when I miss it and wish I still had it around. Before that I learned on one of the original hand-faceting units built by a fellow down in Seattle – can’t remember his name but I remember my parents driving around all day trying to find out how to find him so I could buy one!

I also have tried out a Facetron and handled a Fac-ette (but not cut a stone on a Fac-ette). First impressions:

• compact. Amazingly compact, probably 1/3 of the volume of my old machine.
• low to the work surface. My old machine was on at least a 5″ base which meant I had to sit in a tall chair and put a phone book or two beside it to rest my elbows on.
• simple rack-and-pinon lowering system with coarse and fine height adjustment. It was more positive with less slop that my old machine, but then again that machine was 25 years old.
• smaller splash pan than I was used to. This one only has about 1″ extra room around an 8″ lap, and is only perhaps 1″ higher than the lap surface. I find it sprays a bit more than I like and I’ve added some plastic sheeting to catch most of it. The smaller diameter is a pain when trying to switch laps though.
• the index pointer is on the BOTTOM of the quill, meaning you must raise the quill to see or adjust what index it’s on. An inconvenience.
• an unusual 45 degree adapter. It’s like a really fat dop with a hole drilled in it at 45 degrees, looking something like half a dumbbell. A allen-key set screw is used to hold the stone dop in it.

What I Like

My first use of the Omni were a joy compared to my older machine. All parts were tight and well-fitted, and cutting an SRB really became one of cutting by sound and moving on to the next index. The depth of cut was repeatable and very accurate. The only time it wasn’t was when I was a bit heavy on the hand and causing some flexing of the quill/head/mast. However I did run into alignment problems when cutting long stones, step cuts, and large stones (as discussed later).

I was wary of the keyed dops, as they system seemed rather primitive. There is a angle sliced out of the back end of the dop, and this butts up against a pin placed appropriately at the back of the quill (and on the transfer jig). However it works well and does not require excessive cheating to be on facet.

The way the quill itself holds the dop was also a bit sketchy to me – it’s a friction-fit of the dop sliding into a precisely-drilled hole in the quill. The dop is held in place by a nylon set-screw. However after using it, I’m satisfied as it is machined to tight tolerances and holds the dops on center, it’s easy and simple to use. I’m not sure how this will continue to work over time as rock dust and grit slowly grinds away at the fit, but we’ll see. So far so good.

And lastly, the digital angle readout and adjustments are clear and work well. Theoretically you can get to 100th of a degree, but in practice I think it’s probably closer to 2 or 3 1/100ths of a degree. I don’t bother trying to cut that accurately as I find moving between laps is enough to disturb the angle, and when polishing some cheating is necessary anyhow.

The Strange

First off, I don’t like the 45 angle dop. It’s heavy, it’s ugly (a minor point) and unlike others adapters, it doesn’t have a 45 degree face to rest on the lap to check if your angle calibration is correct or not. It’s not bad, it’s just different. I personally don’t like it and will probably get someone to machine me a replacement.

Second, the platen which the laps sit on is very large, probably 5.75″ in diameter or so. This means it’s too large to put a 6″ saw blade on for a quick way to cut rough like I did on my old machine (it had a 2″ base for the laps). 8″ saw blades are too thick for my liking and there isn’t enough clearance to the side of the splash bowl anyhow.

The swivel arm takes some getting used to. It doesn’t have a locking mechanism and so you have to be careful not to bump it when you’re cutting, but unless you’re reaching through the machine for something (don’t laugh, I managed to do it a couple times in the beginning) it’s not a big problem. And apart from people speculating that it’s not accurate or will fall out of alignment, the swivel seems pretty sturdy so far.

What I Don’t Like

First off, the machine comes with a very thin manual and not much explanation of what is where. It also does not come with any instructions on how to do more than the basic alignments. This is probably a good thing for most as it prevents them from screwing up their machine… but I’m used to my old MDR which came with detailed instructions of how to align it and so on. An maintenance and adjustment manual would be nice.

The motor is small and not as powerful as I’d like. It takes a while to get to full speed when started, and will definitely slow down when cutting a large stone or polishing a large facet.

Most irritating is that the lap speed adjustment is non-linear. Meaning you turn it on and at the lowest speed (for example, I don’t know the real rpms) you get around 2 rpm, moving it to 50 percent you get say 300 rpm, moving it to 80 percent you get 500 rpm, then 90 percent gets 700 rpm, and finally 10 takes you to 1000 rpm. Takes some getting used to. And since I cut mostly at the fastest lap speeds, it’s irritating as I’m adjusting the speed between 9 and 10 on the dial. It isn’t that hard to create a linear speed control where 1=10%, 5=50% and 10=100% of the speed (I know, I’m a former electrical engineer. Wish I’d paid more attention at university so I could fix the controller).

The laps are held down with a right-handed screw. The screw goes into the top of the spindle that extends perhaps 1/4″ above the surface of the platen. I cut mostly running clockwise, which means if you accidently touch the screw it comes loose. Even if you don’t touch it but it either works loose or you didn’t tighten it enough, it will come flying off and bounce around the lap. Irritating! Why they don’t just use a threaded 1/2″ post with a big nut or quickie-nut is beyond me. I ended up putting a 1/2″ nylon plumbing washer on it to both allow better tightening grip and also so it would hold down an old 1/4″ thick steel lap I have. Without the washers the screw was too long and wouldn’t screw far enough to hold the lap down.

That spindle is a hair thinner than the 1/2″ threaded spindle I used to have. This means my laps don’t sit centered and unless I get lucky, they cause vibration (especially my heavy steel and Batt laps). This is really bad at higher speeds and certain speeds which hit the mast’s resonant frequency.

The swivel arm for the most part is pretty good, except when the machine is vibrating due to the above problem. Then it slowly moves out or in depending how I’m cutting (usually out). This then affects the alignment of the stone to the lap (I’ll elaborate more later). I wish there was a way to lock the swivel arm in position until you are ready to move it.

When the machine vibrates due to off-center laps, the machine can reach a resonant frequency where the head and mast begin to vibrate and sway to the point where the cutting angle changes due to mast flex. Mast flex in general seems to be an issue if you’re heavy-handed, so use a light touch. It’s a precision instrument after all. But the mast flex does rear up due to the vibration problem I’m having.

The transfer jig is sloppy. It’s not overly precise and poorly designed, so if you’re not paying attention, you can move the slidey part up and down and thus put your stone out of center on the new dop. I much preferred the MDR transfer jig and would appreciate any suggestions of others that will work with the Omni dops – they’re 5/16″ rather than the standard 1/4″, so that makes things a little more difficult. And they have that keyed end.

The splash pan is too low and small in diameter for my tastes. It’s more difficult that it should be to get a lap on and off the machine. If it were 1″ larger in diameter it would make a huge difference. Also cost more too, but I’d pay for that.

Lastly, this one seems to be common to all faceting machines so take it for what it’s worth: when cutting girdles the spray reaches the faceting head and everywhere else in the general vicinity of the girdle cut-out in the splash pan. I made a little plastic shield that I slip over the dop which helps but it’s not perfect.

Quality and Service Experience

When I received the machine, the first thing that happened was I found the head to be very stiff when adjusting the angle. I mean REALLY stiff – so stiff it took two hands, one to hold the head and one to move the quill up and down. My first response from the manufacturer was that I was tightening the head too much or forcing it — I wasn’t. (the MDR had an incredibly easy to swivel head, and I don’t believe that precision machinery should need huge force to adjust). I finally ended up having to ship it back to Jersey instruments to have it fixed (round trip of about 3 weeks and $20 shipping). No explanation other than when they opened it up and put it back together the problem was solved. Now the head swivels as I expect.

The second problem was that the 45 degree angle dop was out of alignment. It was roughly 2-1/2 index points off (96 index). After cutting two stones I realized it wasn’t me and again had to send it off to get it fixed/replaced. This time it took several weeks (and $10 shipping), during which time I couldn’t cut anything as I had no way to cut/polish the table.

And my current problem is two-fold: there is a hop in the platen, so when I put a lap down (ceramic, steel, steel-capped aluminum) there are high points. These high spots change in location on the lap when I rotate it on the platen. I used a dial guage on the lap and found over 1-1/2 thousands of up-down travel depending on where I spun the platen to. This causes unnecessary vibration and worries me as it’s in essence acting like a mini jack-hammer on the quill and head. Not to mention being bad for the laps and stones.

The second problem I noticed when cutting long/large stones and step cuts is that as the head is swivelled across the lap the stone does not travel parallel to the lap – but it sweeps at an angle that changes, depending on how much the swing-arm is moved in or out. I took the head and mast assembly off the swing arm and rolled it on a granite counter-top — the base of the mast is a brass bushing, and that bushing is not 90 degrees to the mast. These things made it very difficult to cut step cuts (long stones) or large stones.

I reported these problems to Jersey Instruments in an email, and was surprised to get a phone call back within a few hours (on a Sunday at that!). After a quick discussion I agreed to send the machine back to have it looked at. I didn’t have all the original packing and packed it as best I could, which in hindsight wasn’t the best job — I forgot that it’s in essence a 40 lb chunk of metal in a cardboard box, bounced around in trucks and warehouses for 2500 miles ($100 shipping). I also left it disassembled for easier packing.

Anyhow I’m not sure whether he misunderstood what I was talking about or what, but the reply was that a bearing was flooded at one time and replaced, and that the platen was within 0.05 degrees of horizontal. And that as the mast was disassembled they couldn’t tell what the original condition was but it was restored to factory standards. And I was charged for the servicing and return shipping ($235). They enclosed the flooded bearing which does show signs of water. I suspect the water hit it when I was flushing the splash pan to get rid of all the rock dust prior to shipping it out…

Using it since then, I still have the platen hop issue. And the mast not being 90 degrees to the swivel arm, which means that the quill does not swing parallel to the lap but at an angle that changes depending on what position the swing arm is in. By rotating the mast I’ve managed to reduce it but it’s still there, and makes it very difficult and irritating to do step cuts or larger stones.

I’m not going to bother trying to get this fixed again. The cost and bother of shipping the machine back is not worth it. I know what the problem is with the mast and will get it fixed at a machine shop locally for less than shipping the machine back.

The other problem of the laps not sitting centered I’m confident I can find a solution myself. I think it can be resolved with a small rubber gasket on the spindle which will center the laps but compress enough to be out of the way when the screw is tightened. The platen hop will take some more thinking and possibly another trip to the machine shop.

Final Thoughts

I’ve been waiting for more dops (different sizes, emerald dops) to be manufactured. So far I’ve been waiting for at least 3 months since I last inquired (I got the same response – they’re coming soon). I’ll probably get those made locally to my own specs. Being 5/16″ instead of 1/4″ means they’re probably stronger, but at the same time it means you’re stuck until Jersey Instruments gets going.

I’ve also been waiting for a 120 index (I like it for bigger stones). So far same response as the dops.

Overall I think the Omni is a reasonable machine. There are several improvements that can be made (I’m going to get a taller mast made, adding about 1″ to the height so larger stones can be cut) but for the price it’s fair. It’s repeatable, it’s precise, and if it’s a concern, it’s the most compact faceting machine you’re going to find.

Quality-wise it’s also fair. Not sure if I’ve had bad luck or what, but I’m mostly satisfied now that I know what I can count on the manufacturer for and what I need to do myself.

Would I buy one again? For this price – yes. If I had more money, I’d probably explore the Fac-ette as it’s built like a tank and has a couple of interesting features. I haven’t had a chance to work on an Ultratech but I’d work on that too before making a decision either way.

What it boils down to is that for this price I’m happy with what I got. If I had more money to burn I’d go and try the other machines out (at the local clubs) and then choose which one I like the best. Regardless of price. Availability of additional dops and indices would play a small role. Mostly I’d consider repeatability, construction and ease of use. I’m not sure what the service of the other companies is like but I’d assume I need to be self-sufficient to make minor adjustments and fixes myself.

I hope this helps. If you want pics of the machine or more details let me know.

-Al