Can anyone tell me how to access the optical plummet's?ÿreticle adjustment screws on a Sokkisha AP41 rotating tribrach adapter? It looks like the large focus knob doubles as the screw cover, but I'm not seeing how to remove it. It doesn't seem to want to unscrew if I turn it all the way counterclockwise to the end of the focusing range and then try to gently keep turning it.
Thanks!
The fine threads can seize after excessive tightning.
A ring of crud can build and holdfast.
Some caps have set screws installed to prevent over tightening and other have none.
If you ever get it off, clean regularly and thoroughly as any little speck or burr can cause the situtation again.
Righty tighty lefty loosey. It get tight because of grime and dirt. Sometimes I will hav e to use a flat nose plier to remove the cover.?ÿ
Thanks for the responses, @a-harris and @sireath, but I'm still wondering specifically how the AP41's knob / cover is supposed to come off. It would be great if someone could show a photo of an AP41's plummet with cover removed. Looking at the photo I'm attaching now, going from left to right, there's the small-diameter knob for focusing the reticle, then the large-diameter knob for focusing the station, and then a tube extending into the body of the AP41. The tube's diameter is a little smaller than that of the large knob.
The large knob has a smooth section (which happens to be over the reticle screws) and a knurled section. It looks like these are one piece of metal; I don't think the smooth section is supposed to unscrew from the knurled section. The tube turns with the large knob. My guess is that the entire large knob is supposed to unscrew from the tube, but I'm not certain.
Perhaps instead, the tube is supposed to unscrew from within the body of the AP41, bringing the large knob with it. However, I'm not sure that the diameter of the tube is large enough to clear the heads of the reticle screws.
There are three set screws. There aren't any on the large knob or on the tube, but there's one in the knurled section of the small knob; you can just make it out in the photo. I doubt it has anything to do with accessing the reticle screws. On the grey body of the AP41, you can see two set screw holes, one oriented vertically and the other horizontally. They are radial to the axis of the plummet's eyepiece. I suppose they could be locking the tube, and the large knob with it, into the body, but I'm dubious of that, and I'd like know more about what's inside before I start unscrewing them.
I'm feeling like I need an extremely narrow strap wrench to grab the tube while I try to unscrew the large knob from it ?? but I've never seen such a narrow strap wrench.
Thanks for any further help!
Optical plumb on Set 4 with two piece knob
put eyepiece back in place to use while adjusting
Thank you @a-harris for taking the time to make all those photos. The plummet reticle screw cover on your Sokkia SET 4 is essentially the same as on my Topcon total station; it's a separate piece from the large focusing knob (and doesn't even rotate with that knob) and is easy to unscrew. Unfortunately, on the AP41, it really looks like it's one piece (the "cover" is just the front portion of the knob), with no good way to grab hold of the tube onto which I suspect the knob is threaded. I've had no luck finding a manual or instructions for the AP41 on the web.
It does look like a one piece knob, however
you must turn the big knob to the left till refusal
then grab only the front smooth part and rotate left and the cover will seperate from the knob.
A belated follow-up: @a-harris ?? After your last reply, I was visiting Urs Reinhardt of Swisstek (having fun with antique Kern theodolites). I had the AP41 with me, and Urs happened to have some strips of rubber in his shop that were the right size and thickness to improvise an appropriate strap wrench. The screw cover came off easily, in just the way you described.?ÿ