[delraydella]

I'm looking at buying a cross slide rotary table for milling. These tables are pretty expensive, but I found one for a fairly good price. There's only one problem...a broken off mounting tab.

The picture below isn't the actual table, it's only for reference, but if you look at the very bottom of the table base, you'll see a set of tabs on either side, these are the hold down tabs that bolt to the t-slots in the mill table. One of these tabs is broken off and it no longer exists. I believe the base and the tabs are cast iron. What are my options to repair this welding-wise? It need to be strong.


The two ways i thought of (non welded) would be either to make a shim the thickness of the tab and bolt it down with a fender washer to the base and mill table...... but I'd be worried about vibration eventually loosening the shim.

Or, mill out the entire tab from the underside of the base and bolt in a new hardened steel one.

Other Steve

[Otto Nobedder]

I think I'd build something similar to a carpenter's "hold fast" to bolt in that location. I'd use a "nylock" style nut there to reduce the odds of vibration loosening the joint. I assume the other three mounts are intact?

Steve S.

[delraydella]

Yeah, that would work. The other 3 mounts are intact. Every now and then I'd have to swap out the rotary table for other fixtures depending on the project, which could make the nylock a little tedious,but it would definitely hold up to any vibrations.

[235711]

Hello delraydella

That is a nice rotary table. It looks like it is a compound sinus rotary table? Those are especially nice. I was giving your question on how to best repair the tool some though and came up with this idea. I agree that in this case there are better options than welding. And since you already have a milling machine , the battle is more or less won.
My recommendation is to machine a flat surface ( face mill ) on the side of the rotary table where the mounting feature is broken off. The surface must be parallel to the center line of the two intact mounting features and perpendicular to the rotary table’s mounting surface (bottom). The surface will provide you a flat contact face to utilize a toe-clamp for milling machines like the one in the picture I have provided (fig.1) . There are many different sizes and styles. They have a low profile and will be underneath the plane off the rotary table work face. These style clamps, are compact yet are capable of producing very high clamping forces more than sufficient for your application as the "4th hold" on you rotary table . By using the three existing mounting features plus the toe clamp as a substitution for the broken off mounting feature, I am certain the tool will remain secure for any job you can set up on it. I also think that with a milled face, the rotory table will no longer look "damaged" which is good if you ever give some customers a walk through of your shop.

If you are concerned with vibration I suggest using split ring compression washers on the bolts. Such washers are not required for the toe clamp however.
Hope this helps a little

Cheers
235711

Cheers

[Otto Nobedder]

Nice!

That's almost exactly what I had envisioned in my suggestion of building something akin to a carpenter's "hold fast".

As an ameteur machinist, I was not aware this was commercially available, T- slot base and all. A neat solution to his problem.

Steve S

[Billbong]

Hi, LOL....a toe clamp....sounds like a medieval torture device that goes with the thumb screw.

Now, that device will be handy for all those large area surfacing jobs where a vice doesn't open enough or the plate is too big for any vice, or any piece of material that needs a surface machining operation before surface grinding etc....round discs come to mind.

They could also be used to hold a job on an angle plate, provided the angle plate has T slots etc, but it looks like the T nut base can be removed, so no problem.

Hey, take it a step further and you could use them to hold a job on a face plate in a lathe for facing off without the clamps getting in the way.

With that thought in mind you could also have a very large face plate chuck with multiple jaws.

Toe clamps!!!!!......... gonna go on Ebay and see if any's being listed.

BTW, getting back to the original problem, I would make a new steel base plate from a piece of cold rolled 20mm thick mild steel, slightly longer than the existing base of the table, to span 2 T slots per side on the mill table, and screw it to the bottom of the XY slides base.

The only machining you have to do is to face both sides of the new base plate, mill out the holding bolt slots and drill and counterbore for Cap screws.....the only machining you need to do to the table is to drill and tap the XY base for the screws in a position with enough solid metal.

This could be done without dismantling the table XY slides, as it is the base of the XY slide metal that is drilled and tapped.
Ian.

[delraydella]

Thanks fellas!!! Those are some good solutions!.....I think the toe-clamp idea is a great one and should work very well for this and many other clamping problems. I really like the idea of using them in the lathe for facing off thin pieces, too. Right now i'm looking at a job that would require facing several thousand pieces of 1/2 and 3/8 inch thick aluminum rounds, so they could work well there too.

Billbongs idea of a new bottom plate was a good one, too, and i would most likely have gone that route if i didn't have to take the table off every so often. The table already weighs about 40 pounds, so i'd rather not add any extra weight that i'd have to lug around if i didn't have to. If i were still in my 20's it wouldn't be a problem, but that was many years (beers?) ago!



Other Steve

[weldin mike 27]

Hi there,

That job with all the facing sounds like it could require some specialist macinery

http://www.edgetechnologies.com/edge/edge_machines.htm

Maybe you might be able to lease a machine such as these.

Mick

[delraydella]

Mick,

Those are beautiful! If you ever get stuck for an idea of what to get me for Christmas .............

It's funny you should bring up bar feeders. Right now I'm bidding on a CNC lathe with a built in bar feeder. It would be nice to have, but i have a feeling it will get out of my price range pretty soon.

Other Steve

[delraydella]

here's a picture of it. It looks to be in good shape

[weldin mike 27]

Hey,

What the hell..... .....bar feeders for everyone. ho ho ho ho. lol. Fingers crossed about the auction, youve got to be in it to win it though. Do you know if leasing is an option?
Maybe a (well equipped) technical school might have something similar that you could sneak in and use, possibly after hours.

Mick

[delraydella]

I'm sure I could lease one, but for this job, just a few thousand, it probably wouldn't be worth it. I've got it down to where I can face about 50 to 60 pieces per hour by using a couple of different carriage stops and depth gages. The cutter is an indexable carbide one so i don't need to reset any depths, just flip it to another side if it gets dull. The thing that takes the most time now is manually opening and closing the chuck for each piece, but thats only a few seconds per piece.

....... Of course that doesn't mean that I wouldn't take a bar feeder or a CNC lathe if I should happen to find one under the tree..........


Other Steve