Dividing Head Question (lose, slop in worm gear)

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UMDJesse

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I bought a $200 ebay BS-0 head and have some questions. I broke it down and cleaned it, it was surprising clean actually. I've watched several youtube videos where this head is broken down and reassembled, but everyone kind of speeds based the section on getting the worm gear setup properly. If you look at my picture below (taken from the grizzly manual) Forgive me if im naming these parts incorrectly, but...

The PLUG in the GREEN circle appears to center the worm gear
The CAM in the RED circle rotates about 90 degrees to lock/release the worm gear
The SCREW in BLUE limits the rotation of the CAM.

I can adjust the plug screw in and out several rotations and the mechanism still functions smoothly, there doesn’t appear to be one sweet spot. My issue is this, no matter how I adjust the PLUG, my CAM seems to be either too lose or too tight. If I tighten the SCREW too much, the cam is difficult to lock and release. If I keep the SCREW lose, the operation is smooth, but when I rotate the handle, the cam will quickly slide down to the unlocked position. I kind of have to use two hands, one to hold the cam up and one to rotate the handle. I cannot seem to get any improvement regardless of how lose or tight the screw is, and no matter how much I adjust the PLUG in out out. It may also be worth noting that my CAM has only one position screw, and not two like in this picture (part #36)

Can anyone assist?
 

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I don't know anything about dividing heads yet, but I think I would run it on the tight side. Unfortunately, the lack of proper adjustment might just be the nature of the beast on the cheap units. When you have it too tight just tap it ever so slightly to the loose side, but keep it just a tad tight.
 
It should be loose enough to not feel draggy. A little slop is not a bad thing, as long as you turn the crank in the same direction all the time, or back up a bit and then go to the desired hole if you happen to overrun the hole occasionally. If you are unable to achieve a satisfactory setting, you must not be understanding how the adjustment is supposed to be done. I see a screw hole in the circled part at the right side that I think is where the engagement adjusting screw is, this screw would restrict the maximum engagement of the worm into the worm wheel, once adjusted properly, there would be little reason to make further adjustments, unless there is a lot of wear, unlikely for hobby usage.
 
am I generally only supposed to turn one direction? Its generally ok if Im doing this, its when I turn back that everything moves and loosens up.
 
It is a good habit to turn only in one direction, I turn clockwise mostly, to avoid errors in indexing due to backlash in the gearing. If resistance is different going one direction or the other, there is something wrong.
 
Theoretically you can adjust it for zero backlash but it may not be possible in practice depending on the quality of the gears and bearings
You may have to accept a tiny bit of play
 
Play in the order of 1/4" or so on the periphery of the dividing plate would be quite acceptable, so long as the arm is rotated in one direction only when dividing.
 
UMDJesse, from your description, it sounds like you are experiencing backlash. Rule of thumb for every moving thing is to feed in only one direction. Mill, Grinder, Lathe, Dividing Head, RT, ETC. All measurements and calculations are done with backlash eliminated. Not unusual for a crank handle to show .020-.030 play in the gears.
 
Huh, it's been a couple years since I re-re-built my yellow iron dividing head, but... isn't there a spring between the plug #15 and shaft #40 on the print? I know my RT has one. My dividing head backlash must be completely sublime compared to what you're getting. I just don't recall having any trouble with this guy. I did replace the chinesium bearings with German bearings, as I tend to do. But that couldn't be it. Odd.
 
Chewy said:
UMDJesse, from your description, it sounds like you are experiencing backlash. Rule of thumb for every moving thing is to feed in only one direction. Mill, Grinder, Lathe, Dividing Head, RT, ETC. All measurements and calculations are done with backlash eliminated. Not unusual for a crank handle to show .020-.030 play in the gears.
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Yeah, its definitely smoother in one direction. The biggest issue is when I just barely miss the mark and need to go back. However after MUCH tinkering, I think Ive gotten the unit running much better since posting this yesterday. It just seems to be a lot of trial and error to get there
 
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