[How do I?] What's Wrong With This Table Lock?

[leeko]

Hi all,

I'm working on restoring a 10" rotary table for use on my Gorton 8-1/2D vertical mill. It's almost there - one of the last things to do is make up a table lock clamp. This afternoon, I cobbled something together as a proof of concept, but it doesn't work as well as I'd hoped.

The clamp engages the slot around the periphery of the table, and tightening the 5/8 nut *should* clamp the front down hard. The heel of the clamp is sitting on a shim which raises it slightly higher than the front, similar to how milling hold-downs work. There's sufficient gap under the clamp for the nut to be tightened completely without interference.

With all that said, I'm able to tighten the nut down fully as expected. But, I'm still able to turn the handwheel and make the table turn. It's a good bit harder than when the clamp is not tightened, but it's still mobile.

Is this expected, as a result of the 40:1 gearing? i.e. the clamp will be sufficient to withstand milling forces, even though the worm can still turn the table? Or is something wrong with my design?

Thanks in advance for any advice,

Lee



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[Bill Gruby]

Sounds like and looks like the clamp is not engaging on its entire. Raise (shim) the back a bit more. Another 2 0r 3 thousandths might do the trick.

"Billy G"

 

[4GSR]

Lee,

I think you are getting a little over concern there. Yeah, the mechanical advantage of the worm and wheel may/will move the table even when clamped. It should be sufficient to hold the table without moving while milling.

 

[leeko]

Ken, that's what I was thinking - thanks for confirming. Does that happen on commercial units too?

Billy, thanks for the input but I don't think that was the issue. I tried it anyway, but it didn't help.

In fact, I ended up taking a little off the shim, to reduce the amount of daylight I can see (see pic)

Lee



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[TOOLMASTER]

this...

 

[TOOLMASTER]

...........

 

[rock_breaker]

Does the bolt interfere with the clamp when tightened? Tool master has a good point to increase the clamping contact area.
Have a good day!
Ray

 

[leeko]

I don't think so, it seemed like there was plenty of clearance. I can take another look this evening.

Toolmaster, could you explain the second set of pictures please? I'm not sure I understand what I'm looking at. Is that looking end-on at the clamp?

Thanks again!



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[TOOLMASTER]

when your piece get tightened and tilts the only contact will be on the round edge....by adding that groove it will grab the whole way across

 

[rgray]

Put some blue or felt tip on the underside. Bolt it down and turn the table then remove and see how much was actually making contact.