Nylon screws size...

[JoseMiguel]

I have been unable to find the nylon screws locally (the ones that hold the transistors in the heatsink bar) so im ordering a big pack online, but im not familiar with bolt and screw size...

The question is simple, what size should I order?

Thanks

[jsmcortina]

The question is simple, what size should I order?

Some funny imperial size... a bit smaller than M3.

James

[subwoofer]

Isn't that 4-40? Never could figure out if there is any system to the madness below 1/4"...

[Hey_Allen]

Yep, I'm fairly sure that they are 4-40 screws.

As to the logic of the sizing, I'm not sure of the reason for the 4-, 6-, 8- or 10-, but the second number is the number of threads per inch. So 4-40 is 40 tpi, 6-32 is 32 tpi, etc...

Another oddity of the fastener world, and apparently only common in North America, according to the oh so authoritative Wikipedia article: http://en.wikipedia.org/wiki/Unified_Thread_Standard

[DaveEFI]

M3 is the size. Or rather is in most of the world. But you don't need nylon screws for most anyway. Except you must use the correct mounting kit for those devices which have to be insulated from the heatsink. The PCB is marked 'mica' underneath those. But note not for the Q16 position, which may need an insulator depending on type and use.

[cmonref]

As to the logic of the sizing, I'm not sure of the reason for the 4-, 6-, 8- or 10-,

According to ANSI, sizes 0 thru 10 have a diameter of .060" for size 0, then up .013" per size to .190" for size 10. Then 1/4" from there. Line Hey_Allen, I can't see the logic behind the .013" increment between sizes. What does a 76.923th have to do with anything?

[Hey_Allen]

I found an article that said that they were arbitrary numbered sizes up to 10- and then it went to the 1/4" and up in fractional sizing.

As to what sense it made, who knows!

Another bit of fun that I discovered by accident at work, you can cross thread a m3 screw or nut with a 4-40 screw or nut, as long as you either have soft materials, or aren't threading it too far into the nut.
Now, why our company has ONE item that is threaded m3, I have no idea. The other versions of the same part are threaded 4-40, but for some reason ONE part is m3 and was not visibly noted as such other than one foot note in an old procedural manual...

All that said, either a matching 4-40 or m3 nut and screw should work fine. They don't even have to be an inch long, unless you really like threading the nut down 3/4 of the length of the fastener needlessly.

[Ollie8974]

Obtain those small odd size fasteners at a hobby store that sells HO Trains, RC planes and cars.

[Matt Cramer]

Isn't that 4-40?

That is correct.

Never could figure out if there is any system to the madness below 1/4"...

Me neither. At least, being a Chrysler nut, I can remember that the size of the screws sounds like a big block Mopar.

[DaveEFI]

I must admit to wondering just why nylon screws are supplied? I can understand using them for the MAP sensor to avoid damage - but seems odd for mounting transistors etc. Also another moan - please change those stupid stick on resistors (R37&38) to proper TO220 cased types which use a screw fixing.

[billr]

"I must admit to wondering just why nylon screws are supplied?"

Same here. Nylon shoulder-washers with steel screws work much better.

[Matt Cramer]

I must admit to wondering just why nylon screws are supplied? I can understand using them for the MAP sensor to avoid damage - but seems odd for mounting transistors etc.

Many kits are built by people with no electronics assembly experience. Nylon screws offer fewer ways to be put together incorrectly.

Also another moan - please change those stupid stick on resistors (R37&38) to proper TO220 cased types which use a screw fixing.

The current production kits have changed over to this style. I can't promise we'll stay there - parts sometimes get discontinued without warning and force us to migrate to a different design - but we'll try.

[racingmini_mtl]

The problem with nylon screws is that anything that does generate any significant amount of heat will also likely result in a loosening of the nylon nut over the screw. That also has the effect of lessening the heat transfer to the heat sink which means more heat and more loosening and can potentially lead to failure or over-temp shutdown of components. I don't think that's an issue for the MS board components in normal operation but that's something to keep in mind.

Jean

[DaveEFI]

I must admit to wondering just why nylon screws are supplied? I can understand using them for the MAP sensor to avoid damage - but seems odd for mounting transistors etc.

Many kits are built by people with no electronics assembly experience. Nylon screws offer fewer ways to be put together incorrectly.

Also another moan - please change those stupid stick on resistors (R37&38) to proper TO220 cased types which use a screw fixing.

The current production kits have changed over to this style. I can't promise we'll stay there - parts sometimes get discontinued without warning and force us to migrate to a different design - but we'll try.

But. The fixing kits for those transistors which have to be insulated come with metal screws.

Thanks for changing the resistors though. Saves me the cost of buying them. I've never seen the glue on type in the UK.