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Trimming techniques

Posted by Ron Layton  
Ron Layton March 15, 2012 12:11AM
Does anyone want to share some "tricks" they use when trimming specimens with a hydraulic or mechanical trimmer? I just bought a new one from Ann Meister and its a solid performer. The only techniques I know are two that I learned from David Shannon: put the specimen in a zip lock lunch or snack bag or wrap the whole set up with a big sheet of foam rubber. Both of these tricks work well to minimize loss and the danger of hi speed mineral bullets flying recklessly about.
Michel Ambroise March 15, 2012 08:31AM
Hello Ron,

For very hard matrix, it's sometime very good to "precute" the stone with a electrical saw.
Then the trimming is easier and normally break where you want.

Make sure that the twochisel are really "press" against the stone, then you can pump...

Good luck and don't forget to start with some non "valuable" specimens to make your experience.
Every place where you collect, the matrix change, so it's always a new experience.

Rock Currier March 15, 2012 11:43AM
I think the larger and stronger and over built a trimmer is, the better it can break tough rocks without the somewhat explosive results that you sometimes get when trimming them. For these tough customers I think the cause most trimmers to "bulge" or "bow out" as the pressure is increased and when the rock finally does break they act a bit like a bow releasing an arrow causing the rock to seemingly explode. Really big beefy trimmers seem to lessen this effect. The main impediment to rapid trimming of specimens is caused by the time necessary to adjust the cutting blades/chisel points to snug up against the rock. Almost every specimens is different and you spend most of your time getting the cutters snug up against the specimen. Some trimmers, namely some of those used to trim bricks have a little gear/screw crank driven mechanism that allows you to quickly raise and lower the cutting blades to where you need them and then a few quick pumps on the hydraulic jack will break the rock. If you have lots of rocks to trim, you will save yourself hundreds of hours of lowering the cutters and then snugging them up against the rock.

Rock Currier
Crystals not pistols.
Ron Layton March 16, 2012 05:24PM
I should clarify my post. The Meister trimmer is a screw type. I fell victim to one of those little "C" clamp jobs and a Chinese hydraulic back in the late 90's at the Denver show. Both were sad excuses. Even though the Chinese one had been worked over by a dealer, it still didn't make it to a year of normal use. It would have been a nice trimmer if it were engineered correctly. I won't even bother talking about the "C" clamp. The best part about using the baggies to hold the specimen is not only do you get to see everything that came off during the trim but you keep dust out of the screw which to me is a major pain. Here are a few photo's of the Meister trimmer.
Anonymous User March 16, 2012 06:43PM
Hi guys

Please could any one tell me
How can I get my hand on one of these?


Steve Hardinger March 17, 2012 12:22AM
I prefer the Zuber trimmer. I've had my for a few years. It is constantly abused, and still works well.
Michel Ambroise March 17, 2012 12:58PM
Ron Layton écrivait:
> I should clarify my post. The Meister trimmer is a
> screw type. I fell victim to one of those little
> "C" clamp jobs and a Chinese hydraulic back in the
> late 90's at the Denver show. Both were sad
> excuses. Even though the Chinese one had been
> worked over by a dealer, it still didn't make it
> to a year of normal use. It would have been a nice
> trimmer if it were engineered correctly. I won't
> even bother talking about the "C" clamp. The best
> part about using the baggies to hold the specimen
> is not only do you get to see everything that came
> off during the trim but you keep dust out of the
> screw which to me is a major pain. Here are a few
> photo's of the Meister trimmer.
> ning/100_0695.jpg
> ning/100_0690.jpg

Unless for soft matrix and to prepar final micromount, i don't see any use for this type of trimmer......

It's totally unusable because you need your two hands to be efficient.
On a classic one it's good to keep one hand on the specimen in order to make sure to keep all the pieces if you make micro.
Luca Baralis March 17, 2012 06:05PM
Sometimes time is the secret.
On very hard cristalline matrix the time between pressing and cracking can be quite long (ten or more minutes, too).

Luca Baralis
Don Saathoff March 17, 2012 06:26PM
I've built a heavy canvas tent to enclose my trimmer (homemade & hydraulic) and have, on occasion, left specimens under stress overnight. The heavy canvas tent also absorbs some of the noise of the explosion when the stress finally does its job!!

Rock Currier March 18, 2012 04:18AM
I have sent Annie Meister an email to see if these are still available. Her father used to run a machine shop and he was interested in gems and minerals to the extent that he he eventually became president of the American Association of Mineralogical societies and manufactured his own brand of faceting lap and these trimmers as well. If they are still available, Ill put you in touch with her.

Rock Currier
Crystals not pistols.
Ron Layton March 18, 2012 05:49PM
I just got this trimmer in the mail from Ann a week ago. She has more and they are still being made. Base price without postage is $250.00 Worth it in my book. I've used screw type trimmers for 40 years and this one is the best I've owned. I have not had any trouble with screw type trimmers being "useless". Here's Ann's email address as shown on her flyer: Here's a copy of the flyer she puts out at the shows recently.

Edited 3 time(s). Last edit at 03/18/2012 08:13PM by Ron Layton.
Rolf Brandt March 18, 2012 06:33PM
Hi, I had a trimmer built some 30 years ago with a 50 ton hydraulic pump for the really big stuff. Talking about explosions. My colleagues in nearby offices jumped of their chairs when I cracked a big boulder. To be safe while pumping I put a perspex sheet on hinges in front of the rock. Worked quite well. Regards Rolf
Luca Baralis April 01, 2012 12:13PM
About tricks, any advice on trimming triangular section hard specimen?
Under my trimmer the chisel slide away, so I'm thinking about a V-shaped basement.

Luca Baralis

Edited 1 time(s). Last edit at 04/04/2012 10:46AM by Luca Baralis.
Ron Layton April 12, 2012 02:08AM
Perhaps you should cut a notch in one of the corners with a diamond blade. I've had to do this with some specimens and it works great. It gives the chisel somewhere to gain a foothold. Dremel has a variety of diamond blades and there are a lot of knockoff's from different manufacturers. My chisels are adjustable and can be removed so maybe having a "V" bed built is a good idea if the notch doesn't work.
Luca Baralis April 22, 2012 01:17PM
Yes, It can be a good way. I'' give a try.

Luca Baralis
Tim Jokela Jr May 31, 2012 03:54PM
I can recommend the small horizontal-style trimmer (lever moves up and down, jaws move horizontally) from Zuber. Ideal for micromounters, and built like a tank. But limited to small stuff; though you can crack 3-4" rocks if they have a thin edge that will fit btw the teeth.

King of the trimmers is your basic core splitter. You lower it to the rock and then thwack it with a hammer. Apparently more are becoming available as mining co's go over to sawing core instead of splitting; keep an eye out if you frequent mining or coring operations, you might pick one up for a hundred or even free. Can't tell you how much I love these things; I've kicked the crap out of mine and it's still functioning ok, though the spring's gone, bolts are falling out, and the top hammer bit doesn't go down on it's own anymore lol. Definitely need to luck into another one. Has only been defeated by a fist sized piece of pectolite-fibre-included marble from Saint-Hilaire, that stuff is the devil, worse than the silicified dolomite of Herkimer, NY.

Flying chip retention is accomplished by sticking rags or gloves over the rock. Box in the back to catch stuff. Nothing fancy is needed.

Anything fragile, like a nice fluorite crystal, should be sawn out, there's no excuse for not owning some tool that can cut rock quickly, be it a tile saw, diamond blade in a skill saw or angle grinder, small handheld glass cutter, or full on concrete saw. Your average hardware store should have one option or another, for under $100. An inch deep cut combined with skinny wedges makes perfect breaks.

When in doubt, don't risk it, saw it!
Anonymous User June 05, 2012 04:48PM
What is the problem with your Chinese trimmer and where are you located?
They are usually an easy repair to the pump.
The Chinese trimmers had the advantage of size and a stout build. The problem of designing one and manufacturing is a lot of money.

I use a thick clear plastic sheet cut to fit around the shaft of the lower chisel and draped over the bottom beam to keep grit out and provide a soft landing. The trimmer is set unattached in a cardboard box cut low in the front and angling up to a high back to keep flying debris in.

David Zimmerman (2) June 22, 2012 01:51AM
I've got a question that is mostly on topic: On larger pieces, say a squarish-bowling-ball size, what would be the best way to free a 5 inch x 5 inch plate of garnets on one surface. I typically would get out the 14" demolition saw and take one single cut on it and the piece will display beautifully with no signs of cutting (viewed from top, sides, or front), but recently a friend, whom many of you know, was just over and said that this drastically reduces the value and that I should've left more matrix on the backside to possibly abrade with a blaster. I'm a little uneasy about trying to crack a piece this size, as sometimes the garnets are not too firmly attached to the matrix. My main question is approximately what percentage of price reduction occurs when there is a saw-mark on the back of a piece? My secondary question is what tool(s) and/or techniques would you use to extract the plate described above? Retail on the plate would be about $4,000....hence I want to do it right.
Rock Currier June 22, 2012 07:51AM
There is no set percentage reduction in value that I know of that a specimen looses if it has "saw marks". Usually if the saw marks are offensive they can be removed with little pneumatic air hammer/ chisel tools. Where is your garnet from? Usually the risk of breaking and trimming such specimens is so high that it is better to say them and then use air hammer tools to remove the saw marks and shape the specimen to the desired shape.

Rock Currier
Crystals not pistols.
Bart Cannon June 22, 2012 11:44AM
I have little to add, but I will confirm that the Zuber hydraulic and Zuber lever action trimmers have never failed me and I bought the year they were introduced. That might have been 1986. The Chinese copy of the hydraulic Zuber had flawed seals, and maybe inferior framework.

I will also confirm that a core splitter is an excellent option with a less explosive rupture. They have square shouldered threads and are completely indestructable.

There are other methods I use. For boulders, the Micro-Blaster can be used with good precision. For smaller, but very large pieces, drilling holes and filling the holes with expansive mortars can work well, with luck.

And then there is a monument company in New Englad that sells tiny plugs and feathers. Drill a row of holes and enjoy the ping, ping, ping and then the lovely pop when the boulder splits. No flyrock whatsoever.

And sometimes there is no option but the diamond saw for getting the specimen into the jaws.

This is not even my job anymore. I hope none of my clients are reading my posts and getting annoyed at why I am not on their project.

Harold Moritz (2) June 22, 2012 02:49PM
Three different splitters available (as well as repairs, and great refurbished microscopes) from:

I use the mid-sized one all the time with great success. Difficulty stems from when the sides of the specimen are not very parallel, so piece tends to slip out. I like the idea mentioned above about cutting some slots in the piece for the chisels to sit in, thanks for that!
Regarding the comment that one needs two hands to use this type of splitter, generally you must bolt or clamp the unit to a big table, then no problems. Once the specimen is set in the chisels, you can use two hands to advance the screw. You cant physically tighten this unit enough to explode a rock, so very safe. Overtightening will ruin the threads anyway. Everything has its limitations!
David Zimmerman (2) June 23, 2012 04:22AM
Hi Rock,

The hessonite garnet plate is from Jeffrey's Mine, Asbestos, Quebec, Canada. Would you mind dropping the name of the air chisel that you think is the best? To clarify your answer on value: While I know there is no industry rule, is it pretty factual to state that saw-marks on the backside do significantly reduce the specimen's value?
John Lichtenberger June 23, 2012 05:31PM
33 tons of splitting power...:-D and surprisingly delicate... useful when not splitting wood

Edited 1 time(s). Last edit at 06/23/2012 05:32PM by John Lichtenberger.
Rock Currier June 24, 2012 11:08AM
Try Chicago Pneumatic for a selection of sizes. Also I believe there is a fossil dealer that sells a variety of these tools. Perhaps someone where will be able to give is the name of that company.

Rock Currier
Crystals not pistols.
Robert Farrar June 24, 2012 01:10PM

The company that has designed and is manufacturing pneumatic tools geared toward fossil preparation is PaleoTools of Brigham City, UT. We use their tools for projects of all scales - for detail work under the microscope as well as to remove limestone matrix from ammonite fossils. There should be several tools in their line applicable to working matrix on mineral specimens.

David Zimmerman (2) June 24, 2012 02:07PM
Thanks Bob and Rock for the details about the pneumatics. I'll definitely add that to my growing wish list....and I thought a Porta-Power was going to be my next purchase!

John....that's too funny! :)-D I've been wondering about doing that for a long time now, but since I don't burn wood, it would only be used for rocks. What kind of rocks have you split with that? I'm sure sedimentary rocks, but do the harder granites and such also split? I would assume there is a safety pressure blow-back valve on those when overloaded, which is normal on most pneumatic cylinders...but a verification would be great to know. I'd love to hear some of your "log" splitting stories about applications.
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