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Key it and then fill it with epoxy granite?
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I picked up mattbesquares DM45 last week (thanks again, Matt!) and am planning on re-converting it to CNC. So far the only thing I see that really needs attention is the table.
Matt had the table milled out to clear a 1" ballscrew but I feel like it's probably a bit too thin.
Here you can see where it was milled out underneath:
And here you can see how thin the middle groove is:
I was going to try to order a new table but I called around a little and even Penn Tool said they just didn't want to mess with trying to order one.
The pocket is a little over .3" deep (.31 to .32). I am probably going to go with a 16mm ballscrew so clearance shouldn't be an issue. I thought about cutting out a 1/4 or 5/16 piece of steel to fit in the pocket and have it welded to the table but I was afraid that might cause some warping. I could also just drill and tap into the underneath of the table and bolt the steel plate to it. Probably not the best fix but it would probably be better than it is and good enough.
Any thoughts?
Key it and then fill it with epoxy granite?
I don't think you can do much more than thoroughly epoxy and screw the thickest plate you can fit into there to reinforce it. The fact is that table has been SERIOUSLY compromised, and will never again be as stiff as it once was. I would use a LOT of screws, and a THIN layer of the strongest epoxy you can get your hands on! Welding is out of the question - there's just no way you'd do that without turning it into a pretzel, and have to completely re-machine the ways and dovetails. At that point, you'd be better off starting with a new slab of cast iron and just machining a whole new table.
Regards,
Ray L.
The epoxy granite sounded promising and relatively easy but I researched it a little and it doesn't sound like it is that strong in thin slices (<1 inch from what I could find).
I think the steel plate bolted in is worth a shot. I could use a bunch of 1/4-20 or 5/16-18 low profile socket cap screws. The head heights on those are .127" and .158". It wouldn't leave much meat once I countersunk the plate but maybe if I do enough of them it will make up for it. I don't expect it will ever be like new but hopefully its better.
What kind of epoxy should I use underneath the plate?
I will try this out and just use it until the table either bends or breaks. I wonder what it would cost me to have a new table made? Maybe I could find some other table and mount rails on the saddle?
thanks for the suggestions.
Why not just use it as it is. If after your done converting the machine the table causes issues you can make a new one with your Cnc mill.
Judleroy
You might look at some Flat Head Cap screws for attaching the plate, if you have a countersink. Good luck. Ron
I certainly could. I just figured if it was going to cause an issue at some point that I could possibly postpone the inevitable by reinforcing it a little. Also, I wanted to put the brace in and then figure out how to mount the screw so I don't have to re-do that later.Originally Posted by judleroy
I think that's where I'm leaning.
For holding things securely, I would prefer button-heads over flat-heads, though full socket-heads would be my first choice wherever space permits. I've had problems with flat-heads coming loose, and for a given size, button heads seem to be capable of being tightened more.
Regards,
Ray L.
Hmmm... I was actually thinking about low profile cap screws but now that I look at the CAD drawings, it doesn't look like the heads are much thinner than a button head. only .008" lower in the 5/16-18 thread so I guess I could use either. The button head uses a larger hex wrench though so I will probably go that route.
+1
Would a piece of 1018 be OK to bolt in there as the filler piece?
I would think that would be as good as anything.... Don't forget to epoxy it.
Regards,
Ray L.
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