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09-06-2019, 08:38 AM   #1
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Pentax 67 mount screws

I need to replace the six mount screws on a Pentax 67 lens. Does anyone know their size (so I can order some from an online supplier)?
Thanks, Rob

09-06-2019, 05:41 PM   #2
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I don't know about the SMC 67 lenses but with the MF SMC K-mount lenses the most common screw size is M1.7 (1.7mm diameter) in lengths ranging from 1mm to 3mm. If you have one of the old screws and a good set of calipers you can measure it. A good hardware store or machine shop could probably measure the screw too.
09-06-2019, 06:06 PM   #3
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Good tip. Thanks. Unfortunately, while I have a set of digital calipers, on the one P67 lens I have the screws are well and truly stuck! I also have no way to measure the thread pitch. For the lens I need to remove the mount (lens currently in transit) I will need replacements that are 2-3 mm longer. Unless someone knows, I will have to wait until it arrives and I (hopefully) can get them out -- or as you say, off to the machine shop it goes.


QuoteOriginally posted by Not a Number Quote
I don't know about the SMC 67 lenses but with the MF SMC K-mount lenses the most common screw size is M1.7 (1.7mm diameter) in lengths ranging from 1mm to 3mm. If you have one of the old screws and a good set of calipers you can measure it. A good hardware store or machine shop could probably measure the screw too.
09-06-2019, 08:26 PM   #4
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QuoteOriginally posted by rdeloe Quote
I also have no way to measure the thread pitch
With small screws like these the thread pitch is standard to the diameter so no need to measure it.

From an auto repair forum I was tipped off to a penetrating oil product called PB Blaster which is available in Canada (try Home Depot). This stuff worked like a charm to loosen a spark plug where other products I tried failed.

If the lens is used someone may have used a thread lock or other adhesive on the screws. Sometimes heating the screw with a soldering iron can loosen the - as long as the body isn't plastic. Be sure to use JIS drivers as they won't "cam out" and strip the head.

09-07-2019, 08:51 AM   #5
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That was most of my problem right there. I have JIS drivers but thought they had switched to standard Phillips by now. Nope -- they're still JIS. I managed to get two sets out with a JIS driver and lot of muscle. The other two I damaged using my Phillips driver, so they'll need some work (heat or PB Blaster).


In case this ever comes up in future... you were correct that the screws are M1.7mm pan head screws, 3.5mm in length (measured from the tip of the screw shaft to underneath the head).

Thanks for the advice -- super helpful!


QuoteOriginally posted by Not a Number Quote
With small screws like these the thread pitch is standard to the diameter so no need to measure it.

From an auto repair forum I was tipped off to a penetrating oil product called PB Blaster which is available in Canada (try Home Depot). This stuff worked like a charm to loosen a spark plug where other products I tried failed.

If the lens is used someone may have used a thread lock or other adhesive on the screws. Sometimes heating the screw with a soldering iron can loosen the - as long as the body isn't plastic. Be sure to use JIS drivers as they won't "cam out" and strip the head.

Last edited by rdeloe; 09-07-2019 at 12:34 PM.
09-07-2019, 07:32 PM   #6
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If worse comes to worst you may have to invest in a screw extractor:
Moody Screw Extractor & Screw- driver, Mini, Aluminum, 6 Pc

Micro-tools should ship to Canada. If you can determine which size you need you can probably buy a single extractor. Another forum member had to resort to an extractor. You should be able to find the relevant post through the search function.
6 Days Ago   #7
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There are several very useful threads on the forum about screw extraction. You posted in this one, which is a gold mine: Help! Destroyed screws in PENTAX-M 1:2.8 35 mm - PentaxForums.com

There's good info here on JIS screws, including an excellent suggestion that a T-Shirt should be available for members of the "I wrecked a JIS screw with a Phillips driver" club... Cross-head screws - a caution: - PentaxForums.com I should get one so I don't have to wear my "I should have left well enough alone" club T-Shirt all the time. Sigh....


At least I have a clear path forward to correct this. Thanks!
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