Rock Clamps for Slabbing

[Rockoteer]

I posted a pic of my 'Comet' vise a few weeks ago asking what it was and how to use it.  Everyone was very helpful.  I did bolt it to the sled directly but that as not good as I had to remove it to much for other slab cutting.  Then, I think it was Bob who suggested I use a 2x4 under the vise as I was having clearence problems laying it on its side.  Well that worked slicker than slick.  Here are a couple of pics of the slabgrabber and my Comet which looks almost identical to it.

tks
Rockoteer

[Rockoteer]

I tried four times to post three pics so cut the last one off at two pics.  Here is the other pic I wanted to share with the 2x4 under the Comet SlabGraBBer.

Rockoteer

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[hulagrub]

Gary, since you have a Lortone like me, There is also another way I use the slab grabber. Since we clamp down on material with the two bolts,  when you clamp the edge of a rock it wants to pop out. Use the clamp as a leveler on the other side of the vise and wallah, the rock won't pop out.  

[Rockoteer]

Dave, I'm not seeing in my minds eye exactly what you mean.  Any chance you can take a picture?

Sorry..brain not functioning.

Gary(Rockoteer)

[hulagrub]

Will try to find a rock I need to slab like that!

[Rockoteer]

   Great Dave.

Rockoteer

[39don]

I'm attaching a few photos of my rock grabber that came with my saw......the first photo shows the one who made it as LTA Industries Fresno, Ca. I checked them out and they have a 2 person work force. It apparently must be a Mom & Pop operation but the grabber works really well.

I have no idea of the going price or if it can be purchased......

Don

[S/T]

Looking through this thread I’ve seen some pretty good ideas.  I hope that some of you don’t mind that I made a couple of my own and added a couple of modifications that I think may be a little useful.

First of all, I really liked the idea of beginning with the ½ inch cold rolled steel.  The reasoning behind this is that when you cut the grove on the ends, you can leave more material (steel) on the clamp itself.  Looking at the clamp that was made of ¼”, it appears that you would only have about 0.125 to 0.100 of an inch of thickness after you grooved the ends.  That may be adequate for smaller rocks but if you need more clamping force for the larger ones, I think that thicker may be a little safer.  (Just my opinion)

I decided to make a double end clamp or combination clamp, grooving the clamp differently on each side, thinking perhaps one style may work better for a different type or shape of stone.



 I particularly did not think that the sharp, pointed chisel design was the best idea for clamping rock, this design, in my opinion would leave the pointed edge weak and would eventually dull out in different areas quicker and not have as much “holding power”.  Mild steel is still pretty malleable and can deform easily when ground so thin as in a knife edge or chisel edge.   So as you can see, I decided to cut one end with a 3/8th end mill to make a square grove 1/8th of an inch deep and leaving a 1/8th inch X 1/8th inch square end step.

The other side I used a 3/8th ball end mill bit and went 1/8” deep, thus leaving a simi-chisel point and rounded the edge.  Thus leaving the narrowest thickness of the clamp at 0.375” ( 3/8th of an inch)

The other benefit of using the ½ inch stock is that you can tap threads in the bottom clamp and still have a very good thread retention.  With ½ inch all thread @ 16 threads per inch, this gives you 8 threads of retention allowing you to clamp down as much as you like with less chance of you stripping the threads out.
  By threading the bottom clamp, this allows you to illuminate the lower nuts and gives you a clean smooth surface so you can mount the clamp either standing up or laying down on its side.   

 

I have seen these double grooved clamps.. Seemed like one was a bit deeper than the other on them.. Maybe for better grasp on some pieces ??

Went to price these after seeing them again in this thread. Can't seem to find one for under 40.00 with a 5" max capacity..

Seems sorta steep.. ?

Another benefit from this design is that you can always “custom cut to length” any all-thread to your desired length.  In these photos, I used ½”X16 all-thread cut at 8 inches, this length gives me a clamp that can be used to up to 6.5 inches



I also decided to use locking-flanged nuts for stability, and the locking function of the nuts without having to use any additional washers.

[Rockoteer]

I have since took the standard vise out and bolted in the 'Comet' vice.  I do like it for getting the very last out of a slab.  I started doing this after I got the 10 inch Lortone up and running.  I may remove it from time to time.

TOG

[bobby1]

I have been making and using my version of the slab grabber noted in the first few posts on this topic for about 30 years. I find that it is quick, easy and cheap to make, the sharp "V" wears a long time and works very well for me. I use larger holes for the jaws because it allows the jaws to tilt slightly to accomodate those times that I don't get the slots in the rough perfectly parallel to each other. I use only two bolts for the same reason and only two nuts, one on opposite sides of the jaws so I can get a very strong leverage grip on the rock. It is very fast and easy for me to clamp the rock in the gripper, usually 15 to 20 seconds, no precise adjustments with multiple bolts and nuts. I don't paint mine because it is immersed in oil and will never rust. I believe in keeping it simple and very versitile and cheap.
The only time that I have had to replace the jaws is when I'm trying to get that one last slab and as I'm eyeballing it in the saw I misjudge how close I'm trimming the rock and I end sawing the tip off the jaw. I make the ends of the jaws long enough so  that I just mill the end of the jaw flat and add a new groove. Another quick, easy fix.
Bob

[RoyKims]

i've been looking at these and one thing i noticed on the smaller clamps is that both the adjustment screws work in the same direction. they both close. if you make the rear screw to open the clamp you will get a thighter clamping action on the front. many of these you can prove this just by putting your wing nut or nut on the inside of the clamp. after you do this get your jaws about even(maybe a little loose on the rear) and tighen your front screw tight. now open(expand the jaws ) with the rear adjustment screw. this will put a whole lot more pressure on the front of the jaw..
ck it out. you'll be surprised..