quartz
Cave Dweller
breakin' rocks in the hot sun
Member since February 2010
Posts: 3,341
|
Post by quartz on Oct 5, 2010 20:41:59 GMT -5
Here's my round rock holder. 1/2" steel about vise size, held in vise w/wood block, 1" welded to it at 90 deg., bottom 2x4 bolted to 1"; height adjustment is big lag screw w/bar welded across top, pinch rod is 1/2" threaded rod. Need to make sure saw stops before blade hits pinch rod. Cut slots in 2x4's before using. I've cut lots of thundereggs and geodes without any problems. Attachments:
|
|
|
Post by Rockoonz on Oct 5, 2010 21:02:11 GMT -5
Neat clamp
|
|
|
Post by Toad on Oct 5, 2010 21:19:40 GMT -5
BIG! And heavy I imagine
|
|
quartz
Cave Dweller
breakin' rocks in the hot sun
Member since February 2010
Posts: 3,341
|
Post by quartz on Oct 6, 2010 14:21:01 GMT -5
Sorry, I didn't add dimensions to it. The 2x4's are 7" long, rock in holder is 4 3/4" long and 3 1/2" high. "Big and heavy", not really, a little awkward to fit in the saw so we bunch up our round cutting such as we can. The saw is a 16".
|
|
|
Post by deb193redux on Oct 6, 2010 15:00:35 GMT -5
I'm not sure I understand everything about the design, but I question the overall advantage.
The only part I do not fully understand is the wood block holding the steel in the vise. It seems the vise could simply clamp down on the steel, but perhaps the issue is that the 1/2" height is not a lot for the vise to press against.
Setting that aside, you have placed the vise in front of the blade, and you have replaced the tensile strength of the vise with the tensile strength of the pinch rod.
You deal with the fact that the vise is now in front of the blade by noting the need to stop the saw before the blade advances through the rock and into the threaded pinch rod. This does seem inefficient in the increased level of attended operation required. If the alternative is using gorilla glue to glue a batch of round rocks to wood blocks that could be put in the main vise, it seems that the time to glue up the rocks might not be so bad if it permitted unattended operation.
The strength of the main vise, and the fact that the rock is held steady against the blade by the force of the back endplate of the vise, seems more advantageous than this arrangement where the limited contact of the top and bottom of the round stone with the top and bottom 2x4s are all that holds the rock and holds it steady against the blade.
Even allowing that the solidity of the 2x4s and the strength of the pinch rod rivals that of the main vise, there is still the issue of limited contact between the vise and the rock. Also, your design requires that the rock be held equally well on both sides of the cut line.
Without something solid behind the rock, it does seem like the rock might more easily slip back or turn in the clamp. Also, with only a small area of the spherical rock in contact at the top and bottom, it is very plausible that on some lopsided rocks the contact to the left of the cut is firmer than to the right of the cut. This will not matter before the rock is cut, but once the blade has advanced halfway through the rock, one half could be clamped very well, and the other half could become increasingly loose in the clamp. The potential for the rock to turn while cutting - especially near the end of the cut, seems great.
Given the cost of saw blades, the risk does not seem worthwhile given the alternatives for getting the rock into the main vise. This is all from a picture, and not a hands on evaluation. Perhaps I am being too cautious, but this is not a design I would copy while there were alternatives.
|
|
quartz
Cave Dweller
breakin' rocks in the hot sun
Member since February 2010
Posts: 3,341
|
Post by quartz on Oct 7, 2010 21:20:14 GMT -5
The reason for the wood block holding the 1/2" thick [not high] steel in the vise is to get the holder far enough back to be able to get the rock in front of the blade. Methinks you misunderstand the gorilla glue idea, it's for holding a rock for cutting after establishing a flat surface on it, generally by cutting a more or less round rock roughly in half; and the glue idea does work well. Both of our 16" saws have a settable shutoff point, thus minimizing the need for constant babysitting. Conservatively, we have cut 100 rocks with this holder, and have yet to experience slippage or pinching. I tossed this out as a possible solution to a question asked, this one works for us; always open to an improvement on my stuff. The vise doesn't operate on "tensile strength", it works on compressive strength.
|
|