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Richard K.
3-Mar-2010, 09:42
OK, I have a couple of flangeless brassies and I'm wondering how to measure correctly for size. I spent a horrendous amount of money for a digital caliper (must have been $20!!!) :rolleyes: just to enable me to do this. I've been measuring flat against the threads (and getting readings like 65.4mm or an equivalent amount of non-integer inches) but am wondering if the bite of the thread needs to be taken into account - this could make a mm or so of difference? Also, was the thread pitch standard in the 1860s to 1890s or is this also something to consider? Thank you! :)

Greg Blank
3-Mar-2010, 10:27
Outer edge.


OK, I have a couple of flangeless brassies and I'm wondering how to measure correctly for size. I spent a horrendous amount of money for a digital caliper (must have been $20!!!) :rolleyes: just to enable me to do this. I've been measuring flat against the threads (and getting readings like 65.4mm or an equivalent amount of non-integer inches) but am wondering if the bite of the thread needs to be taken into account - this could make a mm or so of difference? Also, was the thread pitch standard in the 1860s to 1890s or is this also something to consider? Thank you! :)

Richard K.
3-Mar-2010, 11:16
Outer edge.

Thank you!

cowanw
3-Mar-2010, 11:24
But yes the thread pitch is not standard. And must be accounted for
Regards
Bill

drew.saunders
3-Mar-2010, 11:27
"How to Measure Screw Threads"
http://www.skgrimes.com/adapter/index3.htm

I had to dig to find it, but I knew it was on their site somewhere.

goamules
3-Mar-2010, 12:17
You are embarking on an adventure. Some of the makers were standardized, like Dallmeyer. All that means is if you need a 39mm flange for both a Dall petzval and one of their landscapes...it will fit both. Sometimes one maker's will fit another. Others, like TTH and Wollensak, had proprietary patterns. Thread pitch and size match does not mean it will fit perfectly, but it is often close enough. Good luck, I've gotten lucky about 1 out of 8 tries.

John Schneider
3-Mar-2010, 12:30
At some point, with all the possibilities of thread form, diameter, and pitch, you need to send it off to SK Grimes or another machinist. You could buy the thread pitch gauges and comparator and thread micrometer (to measure minor diameter) to fully define the thread, but that still won't help you to find a ring.

Richard K.
3-Mar-2010, 15:02
Outer edge.

Follow-up question...

So, if I measure 65mm and I find a seller on *Bay and they have a 65mm flange, do they know they have to account for the thread bite? IOW, if they just used a caliper and measured the inner diameter of the flange to be 65mm, they'll just slip through each other without engaging, no? So how can one reduce the guess-work? Should I be asking for a 64.5mm flange? :confused:

Richard K.
3-Mar-2010, 15:03
Good luck, I've gotten lucky about 1 out of 8 tries.

:) man, I feel confident now! :)

Richard K.
3-Mar-2010, 15:07
You are embarking on an adventure. Some of the makers were standardized, like Dallmeyer. All that means is if you need a 39mm flange for both a Dall petzval and one of their landscapes...it will fit both. Sometimes one maker's will fit another. Others, like TTH and Wollensak, had proprietary patterns. Thread pitch and size match does not mean it will fit perfectly, but it is often close enough. Good luck, I've gotten lucky about 1 out of 8 tries.

But what do you mean by a 39mm flange? One whose I.D. was measured to be 39mm? Or one that will engage a 39mm (outer edge) thread?:confused: If so, its I.D. would actually be less than 39mm but it would still be called a 39mm flange? Do the sellers on *Bay know this? :eek:

Richard K.
3-Mar-2010, 15:12
"How to Measure Screw Threads"
http://www.skgrimes.com/adapter/index3.htm

I had to dig to find it, but I knew it was on their site somewhere.

This is helpful, thank you.

GPS
3-Mar-2010, 15:24
This is helpful, thank you.

Unfortunately, Mr. Grimes is confusing the thread and the pitch in his metric screws description. The letter M means Metric and the number after designates the Major diameter (the outer diameter) of the screw, not its pitch. If you have so called "normal" (= coarse) pitch it is then not mentioned in the screw description at all. The other kinds of pitch (e.g. 0.75) are often called with names such as "fine", "optical" etc. So M4 screw is the designation of a screw with 4mm O.D (Major Diameter) and a coarse pitch etc.

Richard K.
3-Mar-2010, 15:33
Epiphany! :eek: People that SELL flanges should be measuring minor (female) diameter and people that BUY flanges should be measuring major (male) diameter. And they both call it the same flange size. It would be nice (necessary?) if both had the same T.P.I. (threads per inch). Sorry to be so dense...but at least I learned something!

It turns out that I was measuring flange diameter incorrectly, just using the calipers to measure I.D. but flush to the threads not to the cut. I don't think my calipers will allow me to measure female diameter directly but I can add the pitch count, no?

GPS
3-Mar-2010, 15:50
Epiphany! :eek: People that SELL flanges should be measuring minor (female) diameter and people that BUY flanges should be measuring major (male) diameter. And they both call it the same flange size. It would be nice (necessary?) if both had the same T.P.I. (threads per inch). Sorry to be so dense...but at least I learned something!

It turns out that I was measuring flange diameter incorrectly, just using the calipers to measure I.D. but flush to the threads not to the cut. I don't think my calipers will allow me to measure female diameter directly but I can add the pitch count, no?

Basically, you always measure the diameter that is easier to measure with a normal caliper...

Richard K.
3-Mar-2010, 16:16
Basically, you always measure the diameter that is easier to measure with a normal caliper...

But then won't they pass through each other instead of engaging? :confused:

Maybe I should just have one made! BTW I measure 65.5mm for my thread diameter (Ross Rapid Symmetrical 16 f/8 1878), so I look for what size flange? Any idea of what the minor diameter might be? It looks like 24 TPI but how do I utilize that to get minor diameter?

GPS
3-Mar-2010, 16:29
But then won't they pass through each other instead of engaging? :confused:

Maybe I should just have one made! BTW I measure 65.5mm for my thread diameter (Ross Rapid Symmetrical 16” f/8 1878), so I look for what size flange? Any idea of what the minor diameter might be? It looks like 24 TPI but how do I utilize that to get minor diameter?

No, because even if they have the same designation (e.g. M40) they don't have the same measured diameter - because once (for a screw) you measure the easy O.D. and then (for a nut) the easy minor.D. which is de facto the I.D of the screw. They have the same designation (M40) but not the same measured diameters...
Oh boy, I hope I'm not making you nuts with all this...:)
There isn't any ISO M65.5 thread... So it's either a different thread (American thread?) or an old artificial non standard thread.
Yes, you should have one made, the easiest solution, I think...

Richard K.
3-Mar-2010, 16:45
No, because even if they have the same designation (e.g. M40) they don't have the same measured diameter - because once (for a screw) you measure the easy O.D. and then (for a nut) the easy I.D.

But the easy I.D. should be the MINOR diameter, no? I guess I'm worried about buying it on *Bay and the seller just measuring the I.D. (major diameter!) with caliper...


They have the same designation (M40) but not the same measured diameters...
Oh boy, I hope I'm not making you nuts with all this...:)

Yes you totally are, thank you!! :rolleyes: :) But I think that I'm getting closer to sussing this all out and I'll be a better person for it...:rolleyes:


There isn't any ISO M65.5 thread... So it's either a different thread (American thread?) or an old artificial non standard thread.
Yes, you should have one made, the easiest solution, I think...

Well Ross is British so it's probably inches? But how does one measure the inner MINOR diameter - can't do it with calipers! Man, I think I'll rest my percolating brain and dumb out for a while and watch Idol...

Thanks for your help, GPS!

GPS
3-Mar-2010, 16:56
Well, better is if we say the Major and the minor diameter, on a screw or a nut, because what is outer on a screw is inner on a nut but one could easily mistake the inner for the outer on a nut... ;-)
Easier is to measure on a screw - the Major diameter, on a nut - the minor diameter.
Yes, the 65.5mm could probably be the British Whitworth thread (2 1/2in)? Or a Unified Thread Standard for the US? Who knows, if you get crazy from it have it done and keep your head...

Richard K.
3-Mar-2010, 17:10
Well, better is if we say the Major and the minor diameter, on a screw or a nut, because what is outer on a screw is inner on a nut but one could easily mistake the inner for the outer on a nut... ;-)

OK, I wasn't even close to going nuts but that line above...:eek:
I have a graduate degree in theoretical physics but this stuff is really straining my brain! :confused:


Easier is to measure on a screw - the Major diameter, on a nut - the minor diameter.

Really? Doesn't the straight edge of my calipers abut the outside of the threads when measuring the I.D. of a nut? What am I missing (now!!)?


Yes, the 65.5mm could probably be the British Whitworth thread? Or a Unified Thread Standard for the US? Who knows, if you get crazy from it have it done and keep your head...

What's a Whitworth?!? :)

Well, I'll look for a little while and then have one made...ooh my head my head...
Thanks again GPS!

John Schneider
3-Mar-2010, 17:15
But how does one measure the inner MINOR diameter - can't do it with calipers!

As I said before, you need to get a thread micrometer or at least a micrometer with 30deg pointed anvil, at $200+. And because each micrometer measures only the range of an inch, you'll probably need 2 or 3 for all your lenses.

Just have a flange made already.

GPS
3-Mar-2010, 17:25
...

Really? Doesn't the straight edge of my calipers abut the outside of the threads when measuring the I.D. of a nut? What am I missing (now!!)?

...

Oh, - I probably made myself incomprehensible, again... But I even don't understand your sentence now... :) I'm soo sorry, I'll keep shut now...:eek:

Richard K.
3-Mar-2010, 17:27
Oh, - I probably made myself incomprehensible, again... But I even don't understand your sentence now... :) I'm soo sorry, I'll keep shut now...:eek:

LOL time for Idol ....and a few beers...:D

GPS
3-Mar-2010, 17:29
...
Just have a flange made already.

Yes, for the good of humanity, please!! :D

GPS
3-Mar-2010, 17:30
LOL time for Idol ....and a few beers...:D

Finally we understand each other!!:)

Richard K.
3-Mar-2010, 17:32
Oh, - I probably made myself incomprehensible, again... But I even don't understand your sentence now... :) I'm soo sorry, I'll keep shut now...:eek:

I guess my question is:

How can one measure or calculate the MINOR diameter when *measuring the I.D. (MAJOR) of a flange?
*(calipers can easily measure the MAJOR diameter but not the MINOR directly?)

Richard K.
3-Mar-2010, 17:34
I didn't mean to post that last post....finished one (Canadian) beer; next bottle and TV coming up...good night!!:D

Richard K.
3-Mar-2010, 17:36
A

Just have a flange made already.

Yes yes yes :D Somehow I missed this sound advice in my exciting exchanges with GPS!

GPS
3-Mar-2010, 17:45
I guess my question is:

How can one measure or calculate the MINOR diameter when *measuring the I.D. (MAJOR) of a flange?
*(calipers can easily measure the MAJOR diameter but not the MINOR directly?)

don't start again!:) For calculations it is " easy" - if you know the thread norm, that is. Then there are simple equations for that. That is not your case, unfortunately.
For the rest I'm not sure if you speak about a bolt or the nut... For me flange is the big ring nut but that doesn't go with what you say... it just doesn't make much sens to me (something is contradictory in both frases)... so I don't venture into it (you won't get me off my beer soo easily!) :confused:

GPS
3-Mar-2010, 17:47
I didn't mean to post that last post....finished one (Canadian) beer; next bottle and TV coming up...good night!!:D

Thanks!!!:)

Richard K.
3-Mar-2010, 20:22
Um...OK after 3 more beers (Mill Street Wit, yum!) and a bout of Idol, I think I have figured out what caused my confusion :o ...APPLAUSE...

Is it possible that for a bolt the major diameter is the O.D. thread edge to thread edge and for a nut (or flange) the I.D. thread edge to thread edge is the MINOR diameter. I, for whatever weird reason, was thinking that in the flange case the thread edge to thread edge I.D. was the MAJOR diameter. Hence the incredible confused presentations in my posts in the thread. Now, If I'm wrong about being wrong then I'm confused about being confused :confused: and no amount of beer is going to help.

BUT, am I right that an *Bay seller's flange that measures 65mm I.D. thread edge to thread edge (and isn't that the measurement that they are most likely to state as the flange size?) will not fit my thread edge to thread edge O.D. of 65mm? (and, just checking, are those measurements Minor diameter and Major diameter respectively?)

And what's the part of the lens that the flange attaches to called?!?

Thank you. Thank you very much. :rolleyes:

GPS
4-Mar-2010, 03:04
Um...OK after 3 more beers (Mill Street Wit, yum!) and a bout of Idol, I think I have figured out what caused my confusion :o ...APPLAUSE...

Is it possible that for a bolt the major diameter is the O.D. thread edge to thread edge and for a nut (or flange) the I.D. thread edge to thread edge is the MINOR diameter. I, for whatever weird reason, was thinking that in the flange case the thread edge to thread edge I.D. was the MAJOR diameter. Hence the incredible confused presentations in my posts in the thread. Now, If I'm wrong about being wrong then I'm confused about being confused :confused: and no amount of beer is going to help.

BUT, am I right that an *Bay seller's flange that measures 65mm I.D. thread edge to thread edge (and isn't that the measurement that they are most likely to state as the flange size?) will not fit my thread edge to thread edge O.D. of 65mm? (and, just checking, are those measurements Minor diameter and Major diameter respectively?)

And what's the part of the lens that the flange attaches to called?!?

Thank you. Thank you very much. :rolleyes:

Oh, it's me who thank you! The first part is right! -the beer helped! The second part, about the *Bay seller's flange is, in my little head, right too.
When it comes to the part the flange is attached to I would call it simply a lens thread, don't know a better name for it - surely not a lens stump...
Still, if you can, have the flange made for you...;)

c.d.ewen
4-Mar-2010, 06:11
Richard:

I've followed this thread with detacted amusement, as I can recall the difficulty you face while accumulating flangeless lenses. Long ago, I solved the problem by buying a lathe. Don't run out and pick one up, though, without realizing that that's another long learning process.

It might help if you tell us what lens you have. Maybe someone here has the same lens and can measure their flange.

If you invested in a caliper, you might also invest in a thread guage. Get the US set first, as for the scale of objects that we're talking about, i.e., lenses, you'll rarely run into a metric thread besides M0.75. That's the thread on filters, for instance.

If you want to know about threading, go to the library and read the bible - "Machinery's Handbook". It will authoritatively tell you more than you ever wanted to know about threading.

You asked about depth of threads, didn't you? The basic formula is Depth = 0.866 X Pitch. Pitch is the distance the screw moves in one revolution, and is the reciprical of the threads per inch (TPI). A metric M0.75 screw will move 0.75mm per revolution. A 40 TPI screw will move 0.025 in. per revolution.

If you measured the male threads on the lens (we'll call this the Major Diameter, although the Threading Nazis would object) as 65.4mm/2.575 in, and we assume a coarse thread of 26 TPI (Pitch = 0.03846 in), then I'd expect a Minor Diameter aomewhere around 2.575 - (1.083 x 0.03846) = 2.533 in. In real life, it'll undoubtably be a bit wider than this, but I'll let the Threading Nazis worry about that.

Hope this helps. I should probably stay away from the keyboard after early morning caffeine ingestion. This is just too much verbiage.

Charley

GPS
4-Mar-2010, 06:28
Richard:
...

If you invested in a caliper, you might also invest in a thread guage. Get the US set first, as for the scale of objects that we're talking about, i.e., lenses, you'll rarely run into a metric thread besides M0.75. That's the thread on filters, for instance.

...
You asked about depth of threads, didn't you? The basic formula is Depth = 0.866 X Pitch. Pitch is the distance the screw moves in one revolution, and is the reciprical of the threads per inch (TPI). A metric M0.75 screw will move 0.75mm per revolution. A 40 TPI screw will move 0.025 in. per revolution.
....
Charley

But that formula for the depth is valid only for Metric screws... His lens is a British animal, and the formula for Whitworth threads is different...
Not that I would like to make it worse for Richard again, heavens forbid...:)

GPS
4-Mar-2010, 06:39
Richard:

...
It might help if you tell us what lens you have. Maybe someone here has the same lens and can measure their flange.

...
Charley

He said that - see the post n.15...

Richard K.
4-Mar-2010, 07:33
GPS and c.d. thank you for your posts. You have made this a most enjoyable thread for me! AND, I learned something. I might invest in a thread gauge since I anticipate probably buying a few more such lenses (the one discussed here is a Ross Rapid Symmetrical 16 f/8 #33540 1878). But even then it is not a parameter that sellers have ever mentioned. But, for my own amusement, if they're not too expensive... I've been buying caps too (as you can imagine) and been very successful there since there is no pitch to worry about except pitching the cap if it isn't quite right. Even there, I had to tell a big seller (hundreds of caps listed) about how cheap digital calipers are now and that it might help them (they sent me a cap small by 2mm), fior which they thanked me profusely (I guess they were using a mm ruler which with caps I guess is close enough!). I've also even seen sellers list the outer diameter for caps!?!


I solved the problem by buying a lathe. Don't run out and pick one up, though...

Words to live by!!


When it comes to the part the flange is attached to I would call it simply a lens thread, don't know a better name for it - surely not a lens stump...

Lens stump...LOL... well...it stumped ME!

In the end I think GPS is right: "Still, if you can, have the flange made for you..." :D

Thanks guys!!

c.d.ewen
4-Mar-2010, 10:26
But that formula for the depth is valid only for Metric screws... His lens is a British animal, and the formula for Whitworth threads is different...
Not that I would like to make it worse for Richard again, heavens forbid...:)

The formula works for metric and US threads. I had forgotten that Richard had mentioned it was a circa 1870 British lens. The formula for Whitworth threads is: Depth = 0.64 x Pitch == Depth = 0.64 / TPI.

Formulas, of course, only work in theory:)

You can take your chances buying an online flange. As GPS suggests, you're probably better off having a flange made, if you can withstand the expense. Alternatively, I know a number of photographers who have lenses jammed onto flanges with incorrect threads. I cringe at this, but they, oblivious to their error, happily take pictures with the resulting frankensteins. YMMV.

Charley

Richard K.
4-Mar-2010, 11:07
Alternatively, I know a number of photographers who have lenses jammed onto flanges with incorrect threads. I cringe at this, but they, oblivious to their error, happily take pictures with the resulting frankensteins.

Charley

It makes me nervous when about half a turn (or way less!) is engaged - I'd be waiting for it to fall off! :eek:

Robert Hughes
4-Mar-2010, 11:48
I solved the problem by buying a lathe. Don't run out and pick one up, though...
True. I once helped a friend move one - it was a heavy muthaf#kker, I tell you! :eek:

c.d.ewen
4-Mar-2010, 11:53
It makes me nervous when about half a turn (or way less!) is engaged - I'd be waiting for it to fall off! :eek:

Get a bigger wrench and swage it!:D

Charley