Focus block on ebay

ChrisR · Post by **ChrisR** » Wed Feb 17, 2010 3:14 am

I have one of these from ebay

I believe it's an Olympus BH focus block as seen eg here

The small divisions are 2 micrometer(2 micron) movement.
I notice it's grey instead of pale mustard colour, which may give a clue to someone.

Edit...

2 not 1

augusthouse · Post by **augusthouse** » Wed Feb 17, 2010 4:20 am

Yep,

That's a BHMJ focus block.

I'm still confused about the 1 micron division. The manual indicates 2 microns per division? We have discussed that matter before; but I can't recall the conclusion....

Craig

ChrisR · Post by **ChrisR** » Wed Feb 17, 2010 6:01 am

I believe some have 100 divisions, this one has 200, per rev. It's the same "knob" as on an Oly CH. With glasses on you could manage say quarter micron steps.
Small difference, there's no clamp on what would be the right hand side of the microscope.
It does have 3 grub screws to adjust the lateral squeeze on the ball-slide though.

augusthouse · Post by **augusthouse** » Tue Feb 23, 2010 8:33 pm

The focus block on eBay went for a respectable amount. USD $305.00.
A similar item, previously sold by the same seller, went for approx. USD$159.00.
I've always associated the gun-metal grey to earlier versions; the beige versions coming into to vogue in more recent times.

Craig

Planapo · Post by **Planapo** » Wed Feb 24, 2010 2:17 pm

Could anyone of you who's got such a block at hand, tell me how much travel (preferably in mm) its fine focus provides?

Thanks!

--Betty

JB · Post by JB » Wed Feb 24, 2010 2:59 pm

Perhaps the confusion about 1 or 2 microns division comes from the fact, that the numbering on the BHMJ focus block gives the illusion of 200 divisions - but actually there is only 100...

Jörn

ChrisR · Post by **ChrisR** » Wed Feb 24, 2010 4:40 pm

Jörn, are you telling me I can't count ???

That would be silly

OOOOOOPS!!:smt100

Somebody somewhere said 1 micron, and it stuck. Well spotted!

Betty - it's the full travel, of approx 30mm. The fine knob drives the coarse one, rather than a separate mechanism like some microscopes.
(I had to use my toes and borry my wife's fingers for that one)

Charles Krebs · Post by **Charles Krebs** » Wed Feb 24, 2010 5:09 pm

Chris

Somebody somewhere said 1 micron, and it stuck. Well spotted!

Yeah, that could've been me.

But it was quickly corrected to say that is was calibrated in microns... two microns per "tick"

rjlittlefield · Post by **rjlittlefield** » Wed Feb 24, 2010 5:20 pm

The labels on these things get pretty confusing. My CH, also giving 200 microns per turn, is labeled by 20's with 8 ticks between, so 2.5 microns per tick.

On quick glance it looks just like ChrisR's, but on careful count there are only 4 intervals in each smallest group instead of 5.

Betty, the total stage travel on my CH is just over 30 mm. It can move that whole distance with the fine focus knob, given enough patience to make 150 turns.

--Rik

Planapo · Post by **Planapo** » Fri Mar 12, 2010 1:38 pm

Thanks guys, for your replies with the data on the travel of the various Oly focus blocks.
I want to apologize for my late thanks. Family "business" got in the way, and hence I am very short of time lately and lost the thread.
But a friendly member's PM has reminded me of it.

--Betty

augusthouse · Post by **augusthouse** » Thu Apr 22, 2010 1:58 am

There's another one out there....

Craig