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(06-20-2012, 03:18 PM)doubleboost Wrote: Hi
Tee bolts well not snap or break the slot lifting this way
The lifting load is nothing compared to the normal clamping load
The best way to break a tee slot is to use a nut and screw the bolt through it down to the base of the slot
John
I know the clamping load is greater but the clamping load is also perpendicular to the table, not pulling on the T-bolts/nuts at a 30 degree angle. Now if you were to somehow arrange for the force on the bolts to be straight up or close as one can, I would have no concerns with it.
Yep, I may be over-cautious but that's also why I tend to over-engineer things.
-Ron
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I don't think one would have to go to such a wide angle/stance in order to achieve the load balance required. Sure there'd be a bit of tilt but if you watch it while begining the lift you could set it back down and adjust.
I was also thinking that the eyebolts would be just short enough to go through the countertightening nut, washer and adequately unto the tee nut so as to leave clearance from the bottom of the slot.
Also, if employing one of those screw type load leveling devices such as used with engine hoists the angle of the chains (or whatever) would be further reduced.
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06-21-2012, 07:18 PM
(This post was last modified: 06-21-2012, 07:18 PM by arvidj.)
If an engine hoist is being used then I would think that the ubiquitous load leveler would be near by. That would allow the eye bolts to be spaced far apart ... as far part as the load leveler is long ... the draw on the eye bolts to be perpendicular to the table ... and the load to be leveled as it was being lifted.
But then again I may just not understand the real issues.
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(06-21-2012, 07:26 AM)stevec Wrote: I don't think one would have to go to such a wide angle/stance in order to achieve the load balance required. Sure there'd be a bit of tilt but if you watch it while begining the lift you could set it back down and adjust.
I was also thinking that the eyebolts would be just short enough to go through the countertightening nut, washer and adequately unto the tee nut so as to leave clearance from the bottom of the slot.
Also, if employing one of those screw type load leveling devices such as used with engine hoists the angle of the chains (or whatever) would be further reduced.
That all sound pretty reasonable to me.
-Ron
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If you were using two 1/2 diameter forged steel eyelets, the yield strength combined for these two eyes is around 25,000 pounds. Now I am not suggesting you can safely lift that much, but I reckon no hobby machinist has a machine that weighs anywhere near that and the point being that one eyelet would safely lift a cross slide table, let alone two and you could always move them closer together so the lift angle was not so acute.
Many years ago I worked in a testing laboratory and did many test on tensile strengths of various materials. Standard off the shelf 1/2" diameter course threaded all thread rod (from back then) would yield at nearly 10,000 pounds. If you use a 75% safety factor, then 1/2" all thread would be adequate for a 2,500 pound tensile load (remember tensile load, not shear load). Interestingly enough, about this time was when some of the early synthetic materials came to the market and I was amazed at how strong some of the tiniest fibers were. The machine I used was able to exert up to 300,000 pounds of force in 1 pound increments. Some of the biggest challenges was to figure out how to fixture the material in order to pull on it!
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Well I pulled the screw out today but other things getting in the way of moving any further. Thanks for the discussion so far.
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(06-22-2012, 06:12 AM)Mayhem Wrote: Well I pulled the screw out today but other things getting in the way of moving any further. Thanks for the discussion so far.
Good! There's still time for THE warning.
Watch your fingers and toes!!!
-Ron
11" South Bend lathe - Wells-Index 860C mill - 16" Queen City Shaper