[mrcodewiz]

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?

[loply]

Key it and then fill it with epoxy granite?

[SCzEngrgGroup]

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.

[mrcodewiz]

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.

[judleroy]

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

[endo47]

You might look at some Flat Head Cap screws for attaching the plate, if you have a countersink. Good luck. Ron

[mrcodewiz]

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

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.

You might look at some Flat Head Cap screws for attaching the plate, if you have a countersink. Good luck. Ron

I think that's where I'm leaning.

[SCzEngrgGroup]

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.

[mrcodewiz]

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.

[Hans_G]

The button head uses a larger hex wrench though so I will probably go that route.

+1

[mrcodewiz]

Would a piece of 1018 be OK to bolt in there as the filler piece?

[SCzEngrgGroup]

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.

[mrcodewiz]

Do you think any 2 part epoxy made for metal (like the loctite one shown) would suffice?

[SCzEngrgGroup]

Any decent epoxy should come with some kind of indication of it's strength. Most seem to be around 1500PSI or so. For something like this, a long work time will be important, as you MUST get all the screws in and tightened down securely well BEFORE the epoxy starts to set up. I would also use red Loctite on all the screws. Make sure the two mating surfaces are flat (you might want to check the fit with Dykem, and either machine one or both surfaces, or adjust the fit with shims as needed), then tighten the screws in an X pattern starting in the middle, to minimize any bending of the table caused by the plate.

Regards,
Ray L.

[mrcodewiz]

Sounds like a plan. Thanks for the help, Ray.

[ninefinger]

For a real bond without epoxy there is brazing as an option. I know this introduces heat and the risk of warping due to stress relieving but would provide a significantly stronger joint. On a part this size it would likely need to be furnace brazed but if it was critical that would be the way to go.

For a quick, not too worried about the outcome fix I think the epoxy and screws will be fine.

Have you checked the table for flatness? does it show any distortion right now before you try and reinforce it?

Mike

[mrcodewiz]

Have you checked the table for flatness? does it show any distortion right now before you try and reinforce it?

Mike

I have not - I'm not really sure how to do it. I have a surface plate (smaller one) but no straight edge. I will try to figure out a good way to check it. I'm guessing it isn't flat - I can't imagine taking that much metal out of it didn't introduce some sort of change.

Once I get it reinforced, would it be a good idea to get the top of the table ground?

[mmprestine]

Perhaps you considered this since you called Penn Tool but maybe one of the Grizzly G0519, PM45, WTTOOL ZX45, Enco, or Bolton tables will fit. There are enough of these conversions going on here that it might be possible for someone to measure theirs and and if it fits then see if you can buy one of those.

[mrcodewiz]

Good point. I'm trying the others just to see if they are available but so far I have only gotten a price out of Grizzly and they want $842 for their table.