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17-12-2010 #1
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17-12-2010 #2
Can you think of anything better to use that's not too expensive? Maybe plywood, but I guess that's not much better. Vacuum table isn't much good for metals. Bear in mind it needs to be about 800x1900mm ... so clearly I can't afford a nice piece of tooling plate that size!
I'm not sure about the epoxy idea either, wouldn't it just crack/crush?
Making collets for router:
http://www.youtube.com/watch?v=m98fPg-_vUU
Not quite sure with what you mean by exiting the belt through the outer wall, diagram?
I agree buying one is probably the safest option! If you're after a really big reduction then perhaps several timing belts and pulleys could work. If each one gives 1:4 (feasible I think) then you only need 2 belts to get close to 50:1. Timing belts don't have backlash, but I'm not sure about stretching. Why do you want such a high ratio anyway? My rotary table is 1:90 and it takes forever to rotate, even with the 70v stepper drivers.Last edited by Jonathan; 17-12-2010 at 01:11 PM.
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17-12-2010 #3
Jonathan any type of wood table is going to fail to sufficiently clamp metal to it
Whatever you are machining/clamping to the table has to be weaker than or equal strength to the table itself. So the minimum would be ali but it would be cheaper to use steel.
A steel plate with 50x15 bars with 70x15 bars mounted on top to form the tee slots your require, and steel would be my preferred material.
Steel wont warp when wet/different humidity you would have to set your X & Y Axis to run parallel to the plate, now you might think this is a disadvantage not being able to machine the bed to suit the X & Y
But you can only get a flat surface this way if the material is thin as a very thick piece will show any misalignment.
Phil
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17-12-2010 #4
Surely it all depends on what size cutter / feedrate I'm using - if the cutting forces are not to high etc. I was thinking more using the T slots for clamping wood, and using them to clamp my large milling vice (6" jaw, opens up to about the same) to the table for when I want to machine metals. That's still limiting me to only relatively small bits of metal though. If I want to machine a big sheet of aluminium then it's not going to be more than 8mm thick (cost again), so a 6mm cutter would suffice. What's the cutting force on a 6mm end-mill on aluminium at a decent feedrate? Surely not so much that lots of clamps on MDF won't hold it?
I agree putting steel strips on the bed is a good plan, but again very expensive - unless you know of a better supplier than me! I could skim the existing 18mm MDF bed with the router before putting the steel on top. That should get it reasonably parallel. I guess I could afford to make a smallish steel bed.
(Sorry I probably could have made this post a bit less rambling, I'm just thinking aloud.)
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17-12-2010 #5Whatever you are machining/clamping to the table has to be weaker than or equal strength to the table itself
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17-12-2010 #6
Sorry, I had not read the whole thread, I assumed that with a bed of the size you have, you would be machining wood etc. Phil, there are plenty of machines out there using an MDF surface, the MechMate springs to mind and that is one serious machine!! Others use the threaded inserts in the lower board and epoxy to secure them with a drilled replaceable spoil board above. However I guess to machine metals you will be using some form of coolant in which case MDF is a total NO NO.
Tim G-C
“I disapprove of what you say, but I will defend to the death your right to say it.”
(attrib. Voltaire but written by Evelyn Beatrice Hall "The Friends of Voltaire" 1906)
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17-12-2010 #7
The point is, this type of clamping just will not work for a machine vice 4th Axis etc.
The Tee Slot nut will just pull straight out through the MDF or you only clamp with finger pressure:rofl:
Phil
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17-12-2010 #8
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17-12-2010 #9
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17-12-2010 #10
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