Spacers with 2 different thread types
Spacers with 2 different thread types
(OP)
Hi,
At the moment we have a process where a spacer is screwed on to a stud (stud is through a metal sheet) and then a tray is located onto the spacer using a standard screw. However we have an issue where the tray needs to be removable and when we go to undo the screw holding the tray in place we find that the spacer unscrews from the stud as well. We have resolved this by putting glue into the stud end of the spacer but this is creating quality issues of its own so we are looking for another soloution.
One thing we are looking at is placing standoffs in the part instead of the stud + spacer, however there is an issue sourcing standoffs in the lengths we need.
I was thinking about getting a spacer where one side has a reversed thread and one standard so unscrewing one side wouldn't undo the second, however i cant seem to find any spacers that have this after my morning of searching. Does anyone know if these do exist? Is there a term i should be using in my search? Would this work as I envision?
Can anyone think of other soloutions that could be used.
Thanks for your help
At the moment we have a process where a spacer is screwed on to a stud (stud is through a metal sheet) and then a tray is located onto the spacer using a standard screw. However we have an issue where the tray needs to be removable and when we go to undo the screw holding the tray in place we find that the spacer unscrews from the stud as well. We have resolved this by putting glue into the stud end of the spacer but this is creating quality issues of its own so we are looking for another soloution.
One thing we are looking at is placing standoffs in the part instead of the stud + spacer, however there is an issue sourcing standoffs in the lengths we need.
I was thinking about getting a spacer where one side has a reversed thread and one standard so unscrewing one side wouldn't undo the second, however i cant seem to find any spacers that have this after my morning of searching. Does anyone know if these do exist? Is there a term i should be using in my search? Would this work as I envision?
Can anyone think of other soloutions that could be used.
Thanks for your help





RE: Spacers with 2 different thread types
Check out PEM's website for self clinching standoffs. This is the best way to attach PCB standoffs to sheet metal. Another solution is to specify thread-locker, a high strength screw and the highest possible screw torque on the standoff screw, and a softer screw (mild steel, brass or nylon) on the PCB side.
--
JHG
RE: Spacers with 2 different thread types
I get the spacer onto a stud but don't understand "a tray is located onto the spacer using a standard screw." or how you can have "a spacer where one side has a reversed thread and one standard" eh??
Where is this screw in relation to the stud or the spacer?
What does the spacer look like?
Are there any other nuts on the stud?
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Spacers with 2 different thread types
But you just create a different problem.
With opposite hand threads on each end tightening one loosens the other.
What do you mean by "glue"? I was going to suggest Loctite.
If you have quality problems at assembly then perhaps a pre-applied thread locker.
https://www.vibra-tite.com/product-category/thread...
http://www.longlok.com/s.nl/it.A/id.42696/.f
RE: Spacers with 2 different thread types
Thank you for your link, unfortunately the standoff we'd need would be up to 70mm in length and PEM seem to end at 25mm.
Hi LitttleInch,
Ive attached an image, sorry its a bit terrible but hopefully helps explain it. At the minute we use a self clinching stud which is pressed into the metal sheet and then we screw the spacer onto that, then a bolt is screwed through the tray and into the spacer and this holds the tray the correct distance from the sheet. Does that help?
Sorry explanations are not my greatest skill.
For the spacer I was looking for it would look similar to the image attached, however the end going to the stud would have the right handed thread and the end with the bolt would have left handed so in theory unscrewing one side wouldnt undo the other.
Hi Mint Julip,
Thanks, I never thought of how Id manage to tighten the bolt, that does definitely raise an issues. We use locktite at the moment but I will look into the threadmate link you sent! Should help with the control of it
Thanks
http://files.engineering.com/getfile.aspx?folder=1...
RE: Spacers with 2 different thread types
So you have a few mechanical options.
Can you / have you space or time to insert a grub screw into your spacer to grip / lock the stud?
Could you insert a pin through the spacer and nut?
Could you not just extend the stud but with an internal threaded hole for the screw and then have a thin nut to hold it to the sheet?
Solder / CAD weld the stud to the metal sheet? they do this a lot for cathodic protection studs onto pipelines and similar example - https://www.erico.com/category.asp?category=R2721 or search CAD weld
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Spacers with 2 different thread types
If the fixed bolt was drilled then a cotter pin trough the red box would fix in place.
another day in paradise, or is paradise one day closer ?
RE: Spacers with 2 different thread types
Look at my second suggestion. Use a high strength screw, like an alloy steel cap screw. PCB standoffs are made of soft material, so you will need a lot of thread engagement. Maybe PEM studs are strong enough. Specify thread-locker and high screw torque. The thread-locker can be permanent! Use a softer screw and lower torque to attach your PCB. Stainless steel screws are soft, and easily acquired. Now, you can take your screw on and off without disturbing your standoff.
--
JHG
RE: Spacers with 2 different thread types
many ways to skin cats ...
another day in paradise, or is paradise one day closer ?
RE: Spacers with 2 different thread types
RE: Spacers with 2 different thread types
RE: Spacers with 2 different thread types
BTW you didn't use the term "spacer" properly. A spacer is just a hollow cylinder. A standoff is a cylinder with internal or external threads.
ElectroMechanical Product Development
(aka Electronic Packaging)
UMD 1984
UCF 1993
RE: Spacers with 2 different thread types
Kyle