By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by Allendale Jan 24th

PG Optical dividing head

Are the optics saveable?

All Topics | Latest Posts

Search for:  in Thread Title in  
Michael Gilligan21/07/2021 09:06:16
18734 forum posts
916 photos
Posted by Roger Hart on 21/07/2021 06:59:19:


From what I remember from the ATM books, a small amount of warm balsam was applied, the lens put together with no bubbles etc and then put into a brass ring to keep them centred. A small weight applied and left to cool/set. Usually the lens are same size, just a bit of tube - not too tight - is needed.



Ah but … in the best work, the lens elements are centred and joined whilst slightly oversize, and then the edges ground.

Modern tools have largely automated this process, but mid 20th Century it was very skilled hand-work.


Michael Gilligan21/07/2021 10:25:42
18734 forum posts
916 photos

I don’t think Baker had one of these : **LINK**

or these: **LINK**


William S28/07/2021 23:37:17
67 forum posts
307 photos




(quite a difficult thing to photograph)

So in the end I went the LOCA route because I'm a cheapskate!, (it was extremely simple aswell) I also didn't want a huge great quantity left over.


I went with one of the many cheap kits available on eBay, The UV torch was immediately dismantled and jerry rigged to my bench to power supply, the 3 AAA I scrounged only managed to barely illuminate 3 LEDS anyway. This also enabled me to knock up a quick tripod to hold it about 20mm off the bench.

So I experimented with some 1981NOS glass microscope slides(well that's what the boxed wrapped in cellophane said)



The result was a success and gave me confidence to risk the original! It went very well, As can be seen I just used the original brass cell as the line-up ring, the doublet was a relatively good fit anyway (they were the same dia, the lenses Michael) It also meant I didn't have to worry about peening it back it as the glue seems to be holding them in. I cleaned them, a couple of drops of LOCA, place together, wriggled them about to spread the adhesive and dropped it in the cell, lightly pressed it home with my thumb and placed under the UV light. left for about 5 mins, come back to one optically clear doublet.

Reassembly went well, I screwed the brass cell Doublet fully home as it was that way upon the initial dismantle, the glass ring was installed and then the "first" lens was adjusted until the 0.2mm markings were in focus, then the black tube was rotated to get the markings in the right place on the minutes scale, the Baker object mounting thread is off centre to the black tube. The mirrors were not disturbed when I dismantled to preserve the original setting positions, I glad I did this as I would not know where to start to get these back in adjustment!

I then following Clive's advice, "clocked" the glass ring by having it clamped very loosely just pushed it about until the markings all the way around were in the same place on the minutes scale.

Well there we go, I am now going to try and look in to rectifying the minutes scale, Graticules optics is who I will try first, Now that I know it does actually work. And see about a permanent light unit.

Michael Gilligan28/07/2021 23:51:55
18734 forum posts
916 photos

Well done, Sir !!


William S28/07/2021 23:54:01
67 forum posts
307 photos





This is a sales brochure for a 3 second version, but its exactly the same mechanically as my 6 second version, its quite interesting reading, it explains the operation better than I have in previous posts! the Internal diagram especially, this I acquired last week from eBay (again!) It has already provided the rather useful info about the lamp ,6v 18watt.

The Projectorscope 10/250 is actually something my work has on the floor under a bench in the grinding department, it hasn't been used in the 3 years since I started my apprenticeship. Hmm do I have a use for it?!


Robert Atkinson 229/07/2021 08:04:52
1073 forum posts
20 photos

Very nice work. yes

All Topics | Latest Posts

Please login to post a reply.

Magazine Locator

Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!

Find Model Engineer & Model Engineers' Workshop

Latest Forum Posts
Support Our Partners
Eccentric July 5 2018
rapid Direct
walker midge
JD Metals
Eccentric Engineering
Subscription Offer

Latest "For Sale" Ads
Latest "Wanted" Ads
Get In Touch!

Do you want to contact the Model Engineer and Model Engineers' Workshop team?

You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.

Click THIS LINK for full contact details.

For subscription issues please see THIS LINK.

Digital Back Issues

Social Media online

'Like' us on Facebook
Follow us on Facebook

Follow us on Twitter
 Twitter Logo

Pin us on Pinterest