Find the right bolt for PCB spacers / stand offs

[Spork Schivago]

Hello,

I've successfully soldered all the stuff for my UV Exposure unit and now I need to start building the enclosure that will hold it all. I have 12 circuit boards that have LEDs on them and each circuit board has 4 holes, around 2.5MM in diameter. I'm thinking of using stand off's and attaching them to maybe a piece of aluminium or something. 6 boards to the top piece of aluminum, 6 boards to the bottom. I was thinking of using these stand-off's:
http://www.mouser.com/ProductDetail/...4qnTnAu7KrY%3d

They're 4mm long. I don't know a lot about bolts. I would need a total of 48 stand-off's and a total of 48 bolts. Could anyone help me find out what bolts I could use with these stand-offs or if anyone has a better suggestion, I'm down for that as well. I really want bolts that have a flat head on them so they don't interfere with the UV LEDs so much. I think flat ones would look nicer. Thanks!

[stj]

Re: Find the right bolt for PCB spacers / stand offs

if the holes are 2.5mm diameter then you cant use M3 spacers.

M3 = Metric 3mm

[Spork Schivago]

Re: Find the right bolt for PCB spacers / stand offs

Isn't the 3mm the diameter of the whole thing, just not the bolt hole? The copper on the board that's around the hole measures 6mm. Thanks for explaining what the 3M meant. If I'm wrong in thinking the 3mm is the diameter of the whole stand, not just the whole, could you recommend a good size that would work? Don't really know diddly squat about these stuff here. I also made a mistake. The holes are 3mm wide, not 2.5mm

[Spork Schivago]

Re: Find the right bolt for PCB spacers / stand offs

Looking at the data sheet: https://cdn.badcaps-static.com/pdfs/...e7401a85f3.pdf
It looks like I'd need M2.5 stand off? I don't understand the diagram fully. The width for the whole stand off seems to be listed as:
5.0
A/F
4.8

When it says M3 x 0.5 that means the largest diameter is 3mm and there's a thread every 0.5 mm? How do I tell what the pitch is? You know, is it coarse or fine thread?

These are the ones I would want, right Stj?
http://www.digikey.com/product-detai...795-ND/3511496

[stj]

Re: Find the right bolt for PCB spacers / stand offs

the M number is the thread diameter.
why are the holes 2.5mm? are you sure - m3 is pretty standard.

for spacers, you have the thread, the outer diameter, the outer shape - round or hex, the length.
and if it's a studded spacer, the length of the threaded section.

[Spork Schivago]

Re: Find the right bolt for PCB spacers / stand offs

the M number is the thread diameter.
why are the holes 2.5mm? are you sure - m3 is pretty standard.

for spacers, you have the thread, the outer diameter, the outer shape - round or hex, the length.
and if it's a studded spacer, the length of the threaded section.

I edited the original post. The holes are 3mm, not 2.5mm. I just made a mistake. So the original M3 ones I linked to would work? What does studded spacer mean?

[Spork Schivago]

Re: Find the right bolt for PCB spacers / stand offs

These are probably the ones I'm going to go for:
http://www.digikey.com/product-detai...787-ND/3511465

I just need to find the bolts that I can use now and some nuts. The aluminum trays that I'm going to mount these PCBs too are only 1mm thick. Even if I had them tapped, I don't think that's long enough for the standoffs to catch and not strip the thread. So I'll probably use locktight and some nuts on the bottom side and tighten them down nice and good. Any idea what type of screws I would use for them Stj?

[stj]

Re: Find the right bolt for PCB spacers / stand offs

I edited the original post. The holes are 3mm, not 2.5mm. I just made a mistake. So the original M3 ones I linked to would work? What does studded spacer mean?

a threaded spacer has a hole on both ends,
a studed spacer has a threaded stud on one end that you put a nut on.


either way, you need m3 full-nuts, m3 screws, maybe m3 washers
the screw length needs to be the total thickness of what it's going through plus 4-5mm to go into the spacer.


i have loads of m3 stuff, i just strip everything i throw away!

[Spork Schivago]

Re: Find the right bolt for PCB spacers / stand offs

a threaded spacer has a hole on both ends,
a studed spacer has a threaded stud on one end that you put a nut on.


either way, you need m3 full-nuts, m3 screws, maybe m3 washers
the screw length needs to be the total thickness of what it's going through plus 4-5mm to go into the spacer.


i have loads of m3 stuff, i just strip everything i throw away!

Thanks! So I just search for M3 screws, nuts and washers, and I'll find compatible ones? Good to go. I understand what you're saying about the bolt length = total thickness of plate + 4 - 5mm. Thanks for the help!

[redwire]

Re: Find the right bolt for PCB spacers / stand offs

Small metric bolts are hard to find in America, I usually order them off eBay; M2.5's for small LCD displays and M3's for PCB standoffs.

You could instead find (ANSI) #2-56 hardware (2.18mm). 4-40 is the next size up, (I think 2.85mm dia.) and easier to find at fastener or hardware stores.
Spacers (round/hex) have a bigger O.D. and careful metal ones don't short to the PCB traces. Plastic spacers are cheaper and you don't have to worry about shorts.

[Spork Schivago]

Re: Find the right bolt for PCB spacers / stand offs

Small metric bolts are hard to find in America, I usually order them off eBay; M2.5's for small LCD displays and M3's for PCB standoffs.

You could instead find (ANSI) #2-56 hardware (2.18mm). 4-40 is the next size up, (I think 2.85mm dia.) and easier to find at fastener or hardware stores.
Spacers (round/hex) have a bigger O.D. and careful metal ones don't short to the PCB traces. Plastic spacers are cheaper and you don't have to worry about shorts.

Okay, thanks! I've been trying to use metric more than the SAE. The rest of the world seems to use metric. Thought it'd be nice to learn the metric system finally. I noticed the math is a lot easier! 5cm + 10cm = 15cm vs 1/4 + 1/8 = 3/8. Well, that was a bad example because 1/4 + 1/8 we can easily do in our heads. Anyway, thanks for the info, especially on the plastic ones. Not 100% sure what I'm going to use yet. I'm thinking of making the unit out of wood first and then when I get it looking good, working on purchasing the aluminum and everything. That way if I make something a certain size and then decide I need to change the size, I don't gotta pay the money for more aluminum, just for some extra wood.

[stj]

Re: Find the right bolt for PCB spacers / stand offs

just go look around some industrial area's,
you can find all the sheet metal you want and loads of other stuff too.

[Spork Schivago]

Re: Find the right bolt for PCB spacers / stand offs

just go look around some industrial area's,
you can find all the sheet metal you want and loads of other stuff too.

Right, but I think I'm going to go a bit fancy with this and try to get some black anodized aluminum for the bottom part or whatever it's called and maybe some of that brushed aluminum for the top part of the enclosure. We got a few machine shops around here and it's not too pricey to have them do various things. I was thinking maybe I'd check to see how much some gorilla glass would cost. Gonna need to use some sort of glass to hold the circuit boards I'm making.