By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by Forum House Ad Zone

Microscope objective thread

All Topics | Latest Posts

Search for:  in Thread Title in  
John Haine02/01/2010 13:46:12
5563 forum posts
322 photos
I winder if anyone can help with a query on an unknown thread please?
 
I have a cheap microscope (from Aldi!) with a video eyepiece option which connects to a PC.  I want to cannibalise it to mount the optics on a different base with a small XY table for measurement purposes using the "Centrecam" software.  The microscope objectives have a fine thread which is 14.86mm OD, with a pitch I estimate to be about equivalent to 35 tpi.  Sorry for the mix of units but apparently it's common with microscopes to use inch threads with metric diameters!  There is a standard thread called "RMS" for Royal Microscopical Society which is 36 tpi and made in different diameters so I wouldn't be surprised if this thread is also 36 tpi.  Also apparently some lenses are made with 15mm diameter but these are usually 42 tpi!
 
So my question - has anyone else come up against a microscope lens thread of about this size and could they confirm the exact dimensions?
 
TIA, John.
mgj02/01/2010 15:56:04
1017 forum posts
14 photos
Do you have a thread gauge? Tell you straight away , and whether its 55 or 60 deg form.
Circlip02/01/2010 19:04:48
1723 forum posts
And if it's metric, it won't be TPI
 
   Regards   Ian.
KWIL02/01/2010 19:16:11
3681 forum posts
70 photos
RMS thread is whitworth form, ie 55 degrees.
KWIL02/01/2010 19:18:24
3681 forum posts
70 photos
Circlip,
 
Not always true, look at the thread on a metric Clarkson milling cutter, yes its pitch is English tpi!!
Circlip02/01/2010 20:47:24
1723 forum posts
 Yep, 20 TPI constant pitch throughout the range, And now give me the second example Kwil??
 
  Regards   Ian
chris stephens02/01/2010 23:16:23
1049 forum posts
1 photos
Hi Circlip,
I would suggest you Goggle "microscope threads" or just click on;
Sounds like Metric and TPI to me.
chriStephens
John Haine04/01/2010 21:33:18
5563 forum posts
322 photos
Thanks for the responses.
 
 As well as Clarkson cutters, microscope threads are characterised by metric diameter and TPI pitch - as in the link Chris provides.  E.g. Japanese JIS and German DIN standards are 20.1 mm x 36 TPI.
 
I guess if I had a thread gauge I wouldn't be asking...(if it had this pitch on it...)
 
Thread is certainly 55 degrees.
 
Chris, thanks I'd seen that website which got me to where I was when I posed the question....I think either I'll take a punt on 15mm x 36 TPI, or just use some araldite!
 
Of course, once I've set up the microscope I could easily measure the pitch......there's a hole in my bucket too.
chris stephens05/01/2010 02:24:18
1049 forum posts
1 photos
Hi John,
What, no thread gauge and Sandown just gone? Dear me, perhaps you should have gone shopping instead of introducing yourself.
Nice to have met you and good luck with your threading, which you will have to machine till it fits, no matter what size it actually is.
chriStephens
PS if 3BA (34.7TPI) thread is close, it will be the 36TPI option, if 5BA (43.05TPI) is close it will be 42 if that helps identify. Very short, fine threads are always a pain to identify, without very specialist equipment, which you are trying to build. Rather a "Catch 22" situation, methinks. 

Billy Mills05/01/2010 21:19:15
377 forum posts
Hi John and Gang.
Hold an etched rule against the thread then imprint the thread and rule marks onto a lump of plastecene/ staysoft/clay/whathaveyou then count the threads against the scale using the microscope. Any distortion in the media is common to the rule and thread marks so won't matter.
 
OK it's late but Happy New Year anyway.
Alan.
John Haine06/01/2010 09:10:09
5563 forum posts
322 photos
Thanks Alan, a clever suggestion!  I have tried counting the threads against a rule under a x10 glass, unfortunately the screwed section is very short, only 6 or so threads, so one can't get a good average.
 
Happy new year to you also.
John.
 
mgj06/01/2010 12:41:15
1017 forum posts
14 photos
Well the other way of course is a pencil mark and a dial gauge. Measure the travel, count the turns.
Les Jones 106/01/2010 13:04:38
2292 forum posts
159 photos
Hi Meyrick & John,
                                   Meyrick I assume that you mean to put the two threaded parts together and set up a dial gauge to measure how much one part moves with respect to the other for a number of turns rotation.
Les.
mgj06/01/2010 14:51:56
1017 forum posts
14 photos
Yes - or there may be some solid surface and one can use a set of calipers to measure the change in dimension. Or one can put a ruler up (tape it on etc just to give a reference) - any darned hting as a reference will do - edge of a screw or whatever.
 
I mean its not as if it has to be that accurate - if we get a figure of 31.9TPI  after all the calculations, its a fair stab that its actually 32 TPI? Or metricate to suit. People don't often make metric threads with a pitch outside whole fractions. (.5, .25 etc)
 
I though we were in danger of getting a bit  bogged down in technicalities, when all we want to do is measure a pitch which shouldn't exactly strain the grey cells.

Edited By meyrick griffith-jones on 06/01/2010 14:53:37

Circlip06/01/2010 15:12:45
1723 forum posts
The trouble is, you are trying to find a "Standard" for something you are only assuming to be made to a standard. Sadly, the far easterners have been applying their own standards to home manufactured goods for a number of years, it may well be to a western size, but dont bank on it. 14.86 dia.? hardly a "Standard" metric one, close to 14.9 which would be more in line with 15mm on a metric pitch thread, but why not 0.585 or 73/125" dia.
 
  If you're sure about the 55deg. angle, the fact that you're only cutting 6 pitches leaves a lot of alowance to make the threads fit. The afore mentioned 20TPI for the Clarkson auto lock cutters meant that when I cut some adaptor spigots to screw into the largest metric OR imperial Aouto lock collets I have, to enable the use of the three flute "Throw away" SKF cutters, although cut on a fully Metric machine, 1.25mm pitch fits in 20tpi.
 
    Regards   Ian
Martin W06/01/2010 16:18:59
940 forum posts
30 photos
John
 
Dropped you a message re a microscope, offer still there if useful and when weather relents.
 
Or how about turning a mount that is a snug fit to the objective lens thread that you have and then secure with grub/set screws. Alternatively, as you have the imaging system, you could make a new tube with a standard RMS thread and purchase a cheap second hand standard RMS threaded objective lens from ebay. That way you can select the magnification factor to suit and if you wanted to change it at a later date it would be simple. One can get good quality lenses for about £5 - £10 as single items, makes such as Lomo, Watson, Vickers, GS etc are always available. Should you go that way then steer clear of Infinite Focus lens these are speciality items.
 
Cheers
 
Martin

Edited By Martin W on 06/01/2010 16:33:24

Peter Tucker06/01/2010 19:13:39
185 forum posts
John,  I have examined the thread of an objective from my German made microscope,  and found it to be 36 TPI  OD 20.17mm. Viewing with the sterio micrope shows a Whitworth type thread form.
I do know one Japanese made objective will fit my microscope.
Good luck
 
Peter.
John Haine07/01/2010 21:31:01
5563 forum posts
322 photos
Thanks again to all, and especially to Meyrick for his very practical suggestion which I just carried out.  Mind you it wasn't easy, but it looks like the thread is about 0.6 mm pitch.  Given that its diameter is just under 15mm and .6 mm is 42.222 TPI, looks like this is an example of that last microscope "standard" I referred to in my initial post.  The fit of the lens in the turret is disgustingly sloppy anyway, so I don't think it's too critical, as Ian says.  Turning the thread will be a good test for my lathe CNC conversion.
 
John.
 

mgj07/01/2010 21:50:42
1017 forum posts
14 photos
Cut it mandraulically John - more of a challenge than letting the machine munch away while you slurp coffee with confidence!!
 
Actually there is a slightly serious note. If the thread is a bit erratic, doing it manually means you can find the standard as you proceed. ie bodge it a bit to fit fairly well. CNC machines don't think that hard?
Nigel McBurney 112/01/2010 15:19:12
avatar
1101 forum posts
3 photos
HI objective thread is 36 TPI  Whit form, dias were given in decimal imperial But its 40 years since I worked as an instrument maker and I cannot remember the exact dias,Most instrument making was make to a good fit rather than precise dimensions,but the objective threads were always made to gauge as they had to be interchangeable.

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

Sign up to our Newsletter

Sign up to our newsletter and get a free digital issue.

You can unsubscribe at anytime. View our privacy policy at www.mortons.co.uk/privacy

Latest Forum Posts
Support Our Partners
cowells
Sarik
MERIDIENNE EXHIBITIONS LTD
Shopping Partners
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

 

Donate

donate