Author Topic: Rotary table tweaking.  (Read 3556 times)

Offline websterz

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Rotary table tweaking.
« on: November 11, 2009, 07:28:40 PM »
I have a little 4" Grizzly rotab that I bought a couple years ago. I knew before I ordered it that it was not top quality but it came with a set of dividing plates and I figured "How bad can it really be?". Well...today I finally found out, and did something about it. I don't have pics as my camera was AWOL today. Sorry guys.  :bow:

Tearing the rotab down into bits and pieces I was not terribly disappointed with it. The critical areas of the casting were well machined and free of voids and defects. The worm and gear seemed well made and meshed tightly. This model has an adjustment that allows the worm to fully disengage which is nice...saves a lot of cranking on non-critical parts.  :dremel:

Where it was really lacking was in the bottom of the table where the two nuts held the table in place. I presume it is intended as a jam nut arrangement with 3 tapped holes thru both nuts and 8-32 screws holding them together. I really don't see how this was supposed to work as there was no room to adjust the nuts in relation to one another, they just moved as if they were one solid nut. The underside of the rotab was machined well enough for a bearing surface so I dug out a thrust bearing I had bought for use in a ball turner and made up a spacer to adapt it to the rotab's shaft. The two nuts went on the surface grinder and I took them down in thickness by .050" giving me .100" total clearance for the thrust bearing and washers. Rather than screwing the two nuts together to lock them I set them up so I can wedge them apart...the usual way these things work. I opened up the little 8-32's to 1/4-20 and cut down 3 set screws to length. Now I can make small adjustments to the table, tighten the set screws to wedge the nuts in place, and not have to deal with the nuts loosening over time.

While I had the table off the casting I cleaned up the #1 Morse taper in the center and chucked the table stem up in my lathe. DTI showed less than .001" run-out in the taper. I'm happy with that!  :thumbup: Now I can make a morse taper adapter for mounting my 3" 3 jaw chuck and be able to get the table on center much easier.

Digging through my toolbox I found an old 4" 4 jaw chuck that my former employer threw out, and I snagged from the chip hopper. At some point in it's life it gave up the ghost and cracked. Not just once, but through the back at all 4 jaw screws. Someone has pressed a heavy sleeve over the chuck body which is doing a good job of holding it all together. I would never run it under power but for a manual application like a rotab I believe it will be just fine. I made up 4 1/4-20 t-nuts for the table slots, cut down some grade 8's to length, and bolted the chuck to the table. It took about 5 minutes to get the chuck body within .003". Dialing a part with the jaws took about a minute, and was true to .0005".

Tomorrow, if the BBT makes it I will get my webbed angle plates from Enco and I can make a horizontal mount. I have already keyed the end so I can stand the rotab up but it has no provisions for bolting it to the table in that orientation. After that I am going to start working on a tailstock. I have a block of 12L14 I have been saving for just such a project.  :proj:
"In the 60's, people took acid to make the world weird.  Now the world is weird and people take Prozac to make it normal."
 :med:

Offline cedge

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Re: Rotary table tweaking.
« Reply #1 on: November 11, 2009, 08:21:35 PM »
 :worthless:
First time I've had real need of that darned emoticon... LOL

Steve

Offline dsquire

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Re: Rotary table tweaking.
« Reply #2 on: November 12, 2009, 02:55:06 AM »
Cedge

This is like the good old days before windows and digital cameras. Think of it as a walk down memory lane.  :lol: :lol:

Cheers  :beer:

Don
Good, better, best.
Never let it rest,
'til your good is better,
and your better best

Offline websterz

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Re: Rotary table tweaking.
« Reply #3 on: November 12, 2009, 08:33:43 AM »
:worthless:
First time I've had real need of that darned emoticon... LOL

Steve

I need to disassemble the rotab to drill and tap for the horizontal mount...I will take pics and explain the mods then. My camera was in the desk hiding under some junk but it's ready to go now.  :thumbup:
"In the 60's, people took acid to make the world weird.  Now the world is weird and people take Prozac to make it normal."
 :med:

Offline cedge

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Re: Rotary table tweaking.
« Reply #4 on: November 12, 2009, 05:12:17 PM »
Don
You have memories.... some of us have to settle for flashbacks....(grin)

Steve