Filter thread measuring gage?

Donald Qualls · Oct 20, 2020

I've got a Welta Weltini with f/2 Xenon lens, and I want to buy filters for it. Problem is, I can't find any reference that says for sure what filter size it is -- and I have other cameras in the same situation as well -- no marked size, no ready references (because not very common cameras).

Is there a made-for-purpose tool for measuring filter thread diameter? Assuming so, where might one buy it and what's it likely to cost? If not, is there a sensible way to improvise one? It needs to read to at least half-millimeter accuracy below about 45 mm, because of sizes like the 40.5 on my Kiev's Jupiter lenses, and the good possibility that the Weltini's Xenon is 29.5 same as a Retina with that lens.

Mainecoonmaniac · Oct 20, 2020

I have an inexpensive digital caliper from Harbor Freight. It measures inner and outer diameters. It’s good enough for filter threads. For me, it’s handy to have around the house anyway.

Donald Qualls · Oct 20, 2020

I've got the all-mechanical dial version of that somewhere (all my machine shop stuff is stored, too). Worst case, I guess I could buy a new digital one at HF or off eBay. And I can compare it on known threads to verify if they're using the inside diameter (peaks of the threads) or the 60% height like they should...

Pentode · Oct 20, 2020

I use an inexpensive dial caliper, but the digital ones Mainecoonmaniac mentions are a little easier to read. Either way, you'll want to add around 1mm to your dimension when you measure inside threads to compensate for the depth of the threads.

This is not the model I have but it's comparable:
https://www.leevalley.com/en-us/sho...MI3JPaoarD7AIVhZOzCh10RAklEAQYAiABEgJZPPD_BwE

Pentode · Oct 20, 2020

Donald Qualls said:
I've got the all-mechanical dial version of that somewhere (all my machine shop stuff is stored, too). Worst case, I guess I could buy a new digital one at HF or off eBay. And I can compare it on known threads to verify if they're using the inside diameter (peaks of the threads) or the 60% height like they should...

It slipped my mind that you're in the tool repair business and you have machine shop experience. The one you have (if you can find it) should work fine. I find that thread depth varies widely from piece to piece both on lens threads themselves and on filter rings of various manufacture. I've found that adding between .75mm and 1mm, rounding to the closest available size, has never let me down when measuring inside threads.

Donald Qualls · Oct 20, 2020

Okay, looks like I get to dig through the shed again to try to find my dial caliper, and failing that, I'll drop $20 at Harbor Freight for a new digital one. One set of wrong size filters avoided will pay for it...

runswithsizzers · Oct 20, 2020

To completely describe a threaded part you need two measurements - the diameter and the thread spacing.
You can find calipers marked in both inches and metric, but you will need two screw pitch gauges to cover both inch sizes and metric:

Pentode · Oct 20, 2020

Donald Qualls said:
....failing that, I'll drop $20 at Harbor Freight for a new digital one. One set of wrong size filters avoided will pay for it...

If this is the only purpose you're getting it for I propose a modification: Since a $20 caliper is basically a sacrificial tool anyway, you could grind the inside measuring blades so they're blunt rather than pointed and then notch them 1mm from the blunt end and file the nib at the end to a point. As long as you're careful not to cut the material beck from the measuring edge, you would have custom measuring points that would fit between the threads and give you a 100% accurate measurement of inside threads. No compensation needed. It might be a little excessive but it sure would be convenient once you'd done it.

Mainecoonmaniac · Oct 20, 2020

Donald Qualls said:
Okay, looks like I get to dig through the shed again to try to find my dial caliper, and failing that, I'll drop $20 at Harbor Freight for a new digital one. One set of wrong size filters avoided will pay for it...

I used my digital caliper to calibrate my f stops on my old Kodak 8x10 lens. The origins f stop label fell off.

BobD · Oct 20, 2020

This worked for me:
Use calipers to measure the inside diameter of known filter threads and compare the measurement to the known size. Then measure the unknown lens and adjust accordingly to get the unknown filter size.

Donald Qualls · Oct 20, 2020

BobD said:
This worked for me:
Use calipers to measure the inside diameter of known filter threads and compare the measurement to the known size. Then measure the unknown lens and adjust accordingly to get the unknown filter size.

This is what I plan. I have a number of Jupiter lenses (-8, -11, -12) all of which use 40.5mm filters, and I can calibrate against those lens filter threads to know how much to add on the Weltini and other subsequent cameras.

Ian Grant · Oct 20, 2020

Just a thought but most cameras of that era actually used slip on filters, I have Zeiss, Rodenstock, and Rollei slip on filters.

Alternately there were "Clip on" filter holders that could fit a variety of lenses and also take interchangeable glass filters. I've just bought one as I have a near complete set of pre-WWI filters including a graduated yellow. The holder I've bought goes to 37.5mm OD.

Ian

Donald Qualls · Oct 20, 2020

OD checking also worth note -- I used to have a Series VI adapter that slipped onto the focus grip on a Pony 135 Model C. Used it with a close-up diopter.

Ian Grant · Oct 20, 2020

Donald, we thought Cokin were innovative in the mid to late 1970s however the idea was around by 1910 OK glass filters not CR39.

Sanger and Shepperd's 1910 advert. It's possible this was connected to GEK Mees and Samuel Sheppard of Wratten and Wainwright who later joined Eastman Kodak. SAnger's were the main distributors for Kodak minilabs in the UK decades later and for a short time Kodak's UK wholesale distributor after the company closed it's own UK sales division, they quickly went bust

Ian

Pentode · Oct 20, 2020

Donald Qualls said:
OD checking also worth note -- I used to have a Series VI adapter that slipped onto the focus grip on a Pony 135 Model C. Used it with a close-up diopter.

I'm often surprised at how few people seem to be aware of Series filters today. I use Series V, VI and VII filters routinely with both slip-on and screw-in adaptors (and hoods) for a variety of oddball lenses. They can, at times, be a vignetting hazard with wide lenses but, at other times, they're a life-saver.

eli griggs · Nov 6, 2020

I've seen cheap sets of threaded lens adapters, both up and down, on eBay/Amazon that seem to run in a pretty complete range, so if you're bring in new cameras, lenses fairly often, I suggest you invest in a set of step ups and use those as a first resort, and keep picking up Series slip-ons when you find them.

I do no feel I have nearly a complete enough set of those, but a good series filter and adapter is always a good thing to be looking for and using, and the quality of some of that old glass is quite nice.

IMO.

Whatever you do, good luck,
Eli

StanMac · Nov 23, 2020

A plug for filterfind.net, when you’ve determined what filter size you need for those old lenses, Donald.

Stan

Deleted member 88956 · Nov 24, 2020

While caliper is going to give you an idea, it is not all sugar for odd sizes. I had a problem with thread size in a Lordomat lens. But found that cheapest way to get there was to get step up ring in guessed size, then another as it turned out, before I landed on right size. It was an odd one and I had found no filters in that size, so step up ring was needed anyways. A lot of older cameras had push on filters, so not all were covered with screw ins to begin with.

AgX · Nov 24, 2020

Next to calipers there are thread profile gauges. I assume every serious tinkerer has such in his workshop. They are cheap.

But filter threads can be tricky... I got a mint 3-filter stack from KMZ that cannot be screwd together in certain arrangements. Most puzzling.

Donald Qualls · Nov 24, 2020

AgX said:
I got a mint 3-filter stack from KMZ that cannot be screwd together in certain arrangements. Most puzzling.

Tolerances. Same reason Jaguars from the '80s and '90s were known for spending more time in the mechanic's garage than the owner's.

AgX · Nov 24, 2020

Yes, but cutting a thread is basic lathe-work, moreover these threads most likely were cut on automated lathes. These filters had been sold as a kit. And I made stacks out of dozens of filters randomly picked out of rummage boxes and never had issues attaching them.
I put this example up to show that even measuring might not help.

eli griggs · Nov 24, 2020

Buying 'trashed' filters, glass or glassless, that have different threads might just be the way to go, in building a reference 'library' for the lenses you have now, or want to have in the future.

I see eBay sales of mixed lots of blemished or cheap, used filters, for no much money, and suggest this as a way to actually know what you need in a step-filter adapter.

Let us know if you give this a shot, and if it works for your needs.

IMO.

Donald Qualls · Nov 25, 2020

eli griggs said:
Buying 'trashed' filters, glass or glassless, that have different threads might just be the way to go, in building a reference 'library' for the lenses you have now, or want to have in the future.

I've been getting brand new filters off eBay from China, paying $3 to $4 each with free shipping. Hard to imagine buying old ratty ones would be cheaper than that.

AgX · Nov 25, 2020

eli griggs said:
Buying 'trashed' filters, glass or glassless, that have different threads might just be the way to go, in building a reference 'library' for the lenses you have now, or want to have in the future.

All my glass filters I bought used. They are so cheap locally that for me it makes sense to have same filter in several sizes in storage for apt fit than to down-adapt one large filter sample to the camera threads as needed.
Of course this is a great way to pile up stuff...

As alternative I also have packed in a bag a set of most used ones in the small Cokin form added with adapters, ready to take.

Deleted member 88956 · Nov 25, 2020

@Donald Qualls let me add to my Leidolf Lordomat story. I don't recall exact numbers, but after I measured inside diameter I looked for step-up ring in guessed size and ordered one. It did not fit. But I knew how little I was off and started digging available sizes in the range. Got it right on my next order, difference in stated thread size was ... 0.5 mm from first guess. I used the step-up ring route because in the end it is not all lost, as I could use it with more common filter sizes

Filter thread measuring gage?

Deleted member 88956

Deleted member 88956

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