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Pentax 21mm F/3.2 AL Limited - Screws behind front trim
Posted By: house, 06-06-2018, 10:34 AM

Does anyone know what type the screws are? I stripped the heads of two of the screws... now wondering if I can get new ones. See image below which screws I'm talking about.


The lens works fine and the screws are in position. I'm just considering replacing them as I might want to re-grease it later. I used the correct JIS screwdriver but external circumstances (I have two small kids...) made me rush a bit and damn those screws are soft.
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06-06-2018, 10:41 AM   #2
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QuoteOriginally posted by house Quote
Does anyone know what type the screws are? I stripped the heads of two of the screws... now wondering if I can get new ones. See image below which screws I'm talking about.


The lens works fine and the screws are in position. I'm just considering replacing them as I might want to re-grease it later. I used the correct JIS screwdriver but external circumstances (I have two small kids...) made me rush a bit and damn those screws are soft.
if they are original they are JIS

I suggest you review this thread

Cross-head screws - a caution: - PentaxForums.com

Last edited by aslyfox; 06-06-2018 at 11:50 AM.
06-06-2018, 11:47 AM   #3
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I know the type of head, I'm wondering about the threading, dimensions length etc.
06-06-2018, 12:23 PM   #4
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The only way to know is either find the parts list for the lens or take one out and measure it. The old Asahi pre-AF lenses liked to use M1.5 or M1.6 screws. No telling what FA and DA/DFA lenses typically use.

06-06-2018, 12:24 PM   #5
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On a hunch I took the smallest screw from a pair of unused glasses and they fit! This suggests it's a common type of thread, unless there was a mismatch I couldn't sense whilst tightening the screw very carefully. The screws from the glasses were longer so I might not use them but at least there's some hope of being able to source the correct dimensions. Still interested in finding out the naming/threading/dimensions of this type of tiny screw.
06-06-2018, 12:38 PM - 1 Like   #6
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With those size screws they only come as either self-tapping or machine thread. There is a standard thread pitch for each given diameter so no thread pitch is specified. Specs will be given M(diameter) × (length) e.g. M1.6 × 2 = Metric 1.6mm x 2mm. You probably want a pan or wafer head screw. The originals don't look like countersunk flat heads. Measure the length of the original screw.

I don't know if these guys sell direct to end-users. You can always contact sales and explain what you need. They may send you some free samples that just happen to be the size you need:
EJOT® Micro screws ? | EJOT Sverige AB

This place probably has what you need but I don't know if they will ship overseas. You can probably find a source much closer. Try searching on "micro screws" or "precision screws"
Metric Screws
06-06-2018, 01:03 PM   #7
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Great info about the threads and dimensions makes it all less complex than I feared. I just need to get a caliper, I'm tool poor after a mobile life.

Edit: The originals are actually countersunk flatheads. I think the shadowing and the countersink is creating a false impression, I can see why you'd think they werent countersunk. Just posting this for anyone else reading this tread in the future

Last edited by house; 06-06-2018 at 01:14 PM. Reason: futureproofing
06-06-2018, 07:13 PM   #8
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I've recently needed some screws on older lenses and even though probably over priced, you can find some interesting assortments on Amazon and eBay. I found I needed M1.7x4 on an old Takumar 500 - that was a harder size to find and went with M1.7x5 - had the room for the longer screw to protrude without hitting. Here's an example of an assortment on Amazon that covers a variety, but not the M1.7:

amazon.com: HVAZI 12 Kinds M1 M1.2 M1.4 M1.6 Small Screws Assortment Kit: Home Improvement?tag=pentaxforums-20&

If you're trying to match a specific head style for appearance, it can be more difficult, but poke around and you'll find stuff.

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