View Full Version here: : Pentax XL threads question

02-01-2007, 02:44 PM
I recently picked up a 7mm Pentax XL. I know that with the XL's and XW's that you screw the eyecup up or down to get just the right eye relief. Mine does screw up or down but it is quite loose.

I just recently discovered that I can take the rubber eyecup off and unscrew the aluminum piece that the eyecup sits on. What I need to know is what I should use to make the threads a bit tighter and smoother for better action when screwing the eyecup up or down.
Attached is a pic after removing both parts. I have since put it all back together for now until I find out the correct way of rectifying this minor problem.

Does anybody know what I should do?

Thanks in adavance;


02-01-2007, 05:24 PM
Maybe there is a use for sticky Chinese grease after all :lol:

I have two XL's a 10.5 and a 14mm. The 14 has a much looser action but as its not going to move on being bumped like Televue retractable eyeguards, is it really an issue?

02-01-2007, 05:59 PM
That's not exactly the answer I was looking for :whistle: Thanks anyways :eyepop: :lol:

I'll figure it out sooner or later :thumbsup: When I said "loose" I meant really loose. The eyecup moves at the drop of a hat, and I wouldn't mind some nice action on the eyecup when screwing it up or down. Makes for a pleasurable experience at the scope!

02-01-2007, 07:04 PM
It sound like you need a thread filler of some description. Perhaps some of that thin white tape that plumbers use to waterproof threads with might be the go with a smear of silicon grease.

By the way , could you tell me how to take the eyecup off?

02-01-2007, 11:09 PM
Geoff, here is how to take the eyecup off. I got this from a fellow Cloudy Nighter, (Amalia). It's really easy after you try it once. To take it off , use your nail ,( if you have any), and gently pull the rubber up from underneath. Here is a German link, with pics. Here is an online translator below the first link as well.
After you pull the rubber eyecup off, make sure to unscrew the aluminum *DOWN* away from the eyelens and toward the table or whatever the EP is sitting on when you do this.



I hope this helps...and YES I am going to try that Teflon tape that plumbers use :D Thanks for the tip!!!

In case you were ever wondering, a lot of people take the rubber eyecups off to use two Pentax XL's for Binoviewing. :thumbsup:


03-01-2007, 06:39 AM
I have the 10.5mm pentax and it is the same as yours. Very loose!

You could try smearing a little vaseline on the thread, that should give you enough friction to tighten it up.

Or possibly putting the tiniest layer of loctite on the thread, letting it dry, and then assembling.

Good luck!

03-01-2007, 05:17 PM
Geoff, and anyone else that needs something on the threads of their Pentax XL's, I just applied a small amount of vasoline to the threads of my 7mm Pentax XL and the motion is now smooth!!!...I used a small amount with a very small model paintbrush and applied it sparingly to the middle of the threads of the EP after dissassembling it.

It now turns like a factory pentax XW :thumbsup: Give it a go, you'll be surprised ;)

03-01-2007, 08:10 PM
Thanks for the info Mark, and Im glad you're now happy with yours :)

04-01-2007, 11:02 AM

The LAST" thing you should have put on the eyepiece is "VASELINE".

Vaseline has a variable melting point between about 35 deg C (95F) and 41 deg C (105F). The 1st time your eyepiece case is exposed to temperatures "APPROACHING" 35C or 95F (hot car, hot house etc) the vaseline is going to start melting and run everywhere. Likely, all over the Pentax eyepiece in question and over 1/2 the other eyepieces in your case. The problem is, being hydrocarbon based it is not easily cleaned off. It can be cleaned with turps, benzene or chloroform, none of which are likely to do the rest of your eyepiece a lot of good.

I suggest you try to remove as much of it as possible with tissues and the point of a thin nail inside the fold of a tissue.

I try not to "grease" my eyepieces but if you must do it, I suggest you use a grease designed for boat trailer wheelbearings. It is waterproof, chemically resistant,very thick and will stiffen up the movement of the eyecup and most importantly has an extremely high melting point as boat trailer wheelbearings get extremely hot and get dunked in saltwater regularly.


Please don't ever ask to borrow one of my eyepieces :)

CS-John B

04-01-2007, 12:28 PM
Jon, I just read the same thing on CN. I took your advice and cleaned the miniscule amount of vaseline that was on the threads of the EP. I barely put any on, I would *NEVER* slop that stuff all over the EP :scared:

The eyecup now turns like it did before and after wiping the vasoline off, there isn't enough there now for it to run or seep anywhere, in fact it is 99% gone from all the wiping on both the eyepiece threads and the aluminum piece with my fingernail and some soft paper towels,(very carefully of course). I *NEVER* leave my eyepieces in a hot car or even in a hot house for that matter. I do 95% of my observing from my yard, and we have the air conditioner on all the time when it is hot in the house. :thumbsup:

I also want to mention that when I *DO* borrow eyepieces from club members, I treat them as "theirs" with utmost care, and not "tamper" with them.

I want to thank you for the advice however, it is always great to learn new things that may be bad for equipment.

04-01-2007, 09:00 PM
Point noted however we are not talking about huge globs of the stuff. Only the tiniest of amounts. I put some on my 10.5mm a year ago and never had any problems even in the heat as the amount used is miniscule.

11-01-2007, 10:19 PM
Agreed, I never used much either :whistle: