Guess the M3 screw?

[canidoit]

I keep buying the incorrect M3 screws for my Lindell 506 Chassis.

Does anyone know what exactly is the specs of their screws judging from this pic? I put it side by side with other M3 type screws.

 

[soapfoot]

When you say "incorrect," what isn't working?

Is it not threading properly (i.e. "not M3")? If so, could it be an SAE #4-40, perhaps?

Is it not sitting flush? If that's the issue, the one on the right is clearly a countersunk head (as opposed to the "oval head" or raised countersink of the API 6B, or the pan head of the hard drive).

Is it too long and bottoming out, or too short and not threading deeply enough? If that's the issue, measure the length and purchase screws of the desired length

 

[Ilya]

Judging from the photo, the screw on the right has finer thread pitch. If both other screws are M3, then the one in question probably has imperial pitch.

 

[canidoit]

Hi Ilya, I was told too that it might be M3 fine and not course. I bought metric M3 from various stores online, not knowing there were different versions. I had a friend who works with tools and he told me it was M3 standard and gave me the correct screws. Standard M3 meaning course from my understanding.

@soapfoot, sorry for not being descriptive enough. It does not fit in the sense where I can screw it in a little bit and then I can feel the tension where it is about to damage the threads of the mounting hole if I screw further, so I stop.

I thought the API 6B was course and thought maybe the Lindell screw was fine but I was wrong.

Thank you all!

 

[soapfoot]

It does look to be a finer pitch (the screw on the right), unless that's an illusion.

4-40 SAE would be a good guess, but Lindell is in Sweden (thanks Google) so that seems unlikely, too. Hm.

 

[Ilya]

On the photo, there are API and HDD screws. API is an American company, and HDDs often also have imperial screws.
So it’s probably the other way around. Two screws to the left are imperial, the right one is M3.
Different pitches on M3 are very rare and chances to meet such screw are slim.

EDIT. Never mind. I reread your first post. If you tried M3 and it didn’t work, than it’s probably either imperial or different pitch.

 

[Khron]

What sort of "hard drive" is that first screw for? 3.5" drives have #6-32 (imperial) threads; 2.5" ones have M3.

If it's the former, API one may well be #4-40 (coarse), major diameter about 2.8mm (across the tips of the thread form) and 0.635mm thread pitch, which would make the mystery screw actually a normal M3x0.5.

Later edit: here's some screws i had around - 6-32 and 4-40 (out of a MOTU made in USA audio interface), and an M3.

 

[PermO]

On the photo, there are API and HDD screws. API is an American company, and HDDs often also have imperial screws.
So it’s probably the other way around. Two screws to the left are imperial, the right one is M3.
Different pitches on M3 are very rare and chances to meet such screw are slim.

EDIT. Never mind. I reread your first post. If you tried M3 and it didn’t work, than it’s probably either imperial or different pitch.

From the looks in the picture, I agree with you, I'm in Europe and the bolt (screws have a point) on the right seems to be a standard M3 metric bolt.
The ones on the left you'll find in computers and DB style sonnectors, those are not metric M3.

 

[canidoit]

What sort of "hard drive" is that first screw for? 3.5" drives have #6-32 (imperial) threads; 2.5" ones have M3.

If it's the former, API one may well be #4-40 (coarse), major diameter about 2.8mm (across the tips of the thread form) and 0.635mm thread pitch, which would make the mystery screw actually a normal M3x0.5.

Later edit: here's some screws i had around - 6-32 and 4-40 (out of a MOTU made in USA audio interface), and an M3.

The first one I think are the screws for mounting kits for drives either 3.5 or 2.5. I tried several versions of those that I received but to no avail.

You may be right about the API 6B screw, it looks slightly thinner. I thought it would be M3 as it fits the Lindell but just screws partially before jamming.

Also maybe right about the Lindell screw(right), 0.5 is standard(course), is that correct?

 

[Khron]

That's safe enough to assume, if only going by the (even relative) pitch of the screws in your photo.

Slight correction though (minor lapse of judgment) - 2.5" computer drives have M3 threads on the bottom, and M2.5 on the sides.

 

[mad.ax]

Assuming the screw diameter is 3mm, I set my screen ruler accordingly and it looks like a standard M3 with 0,5 pitch.

Measure over 10 threads in millimeters. Divide the result by ten gives you the pitch. Here we see 5mm over 10 threads. 5/10 = 0,5 which is the standard M3 pitch.
Fine ISO pitch is indeed extremly rare, but would be 0,35 for Ø3. If it was a fine you would measure only 3,5mm over 10 threads.

Hope this helps,
Axel

 

[kags]

API uses 4/40 screws in their gear, so if it fits API it’s not M3.

I bought M3 nickel thumbscrews for my Lindell rack and they fit well, but should not be used for the API rack.

I like the thumbscrews so I don’t need a screwdriver or hex key to swap out modules. I keep one rack in my studio and occasionally take one with me, so thumbscrews are easy and look cool.

 

[john12ax7]

I thought all 500 series was 4-40 screws. Does Lindell actually use M3?

 

[Clintcleveland]

I can confirm that the Trace Audio M3 thumbscrews work on the Lindell rack.
https://reverb.com/item/60310031-trace-audio-500-series-thumb-screws-12-pack-m3-threads-black

 

[CJ]

I hate when that happens, sometimes I just grab a tap and make my own darn threads because I country.
Are you country?

 

[Doug_]

The length of a countersunk screw is measured from the top of the head, non countersunk from the shoulder.

 

[kags]

Lindell says they chose the M3 because it is more common and easier to find than 4-40. Maybe that’s the case in the EU?

Probably not a wise idea to change a standard (VPR Alliance) that has been around for decades.

 

[Khron]

Lindell says they chose the M3 because it is more common and easier to find than 4-40. Maybe that’s the case in the EU?

That most definitely IS the case.

 

[ruffrecords]

Maybe this will help?

M3 : Thread Data Sheet (Machining Doctor)

Cheers

Ian

 

[canidoit]

@kags, nice idea on the thumbscrew. I usually place a nylon washer on the non-counter screw as I hate to make round scratch marks bigger than the hole mount.

@Clintcleveland, I wish those were selling cheap on Ebay!

@mad.ax, clever deduction and good tips!

Thanks All for the replies