Pentax 21mm F/3.2 AL Limited - Screws behind front trim

Pentax 21mm F/3.2 AL Limited - Screws behind front trim · 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.

View image in gallery

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.

**aslyfox** · 06-06-2018, 10:41 AM

Originally posted by house

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.

View image in gallery

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

house · 06-06-2018, 11:47 AM

I know the type of head, I'm wondering about the threading, dimensions length etc.

Not a Number · 06-06-2018, 12:23 PM

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.

house · 06-06-2018, 12:24 PM

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.

Not a Number · 06-06-2018, 12:38 PM - **1 Like**

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

house · 06-06-2018, 01:03 PM

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

**clickclick** · 06-06-2018, 07:13 PM

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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06-06-2018, 10:41 AM	#2
aslyfox Seeker of Knowledge Join Date: Aug 2016 Location: Topeka, Kansas Photos: Gallery \| Albums Posts: 24,583	Originally posted by house 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. View image in gallery 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.

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06-06-2018, 11:47 AM	#3
house Pentaxian Join Date: May 2015 Photos: Albums Posts: 3,306 Original Poster	I know the type of head, I'm wondering about the threading, dimensions length etc.

06-06-2018, 12:23 PM	#4
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	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
house Pentaxian Join Date: May 2015 Photos: Albums Posts: 3,306 Original Poster	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
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	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
house Pentaxian Join Date: May 2015 Photos: Albums Posts: 3,306 Original Poster	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
clickclick Loyal Site Supporter Join Date: May 2016 Location: East Coast Posts: 2,904	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.