Circuit Board Standoffs

Ed NutterFebruary 2, 20183 comments

If you are unable to find a circuit board mount in the size you need, there is an alternative.  You could make them from tubing, like steel brake line, with a bolt in the middle.  You could use plastic tubing with a bolt.Using a solid rod is also an option.

If you opt to use some type of rod, there are some things to keep in mind.  Drill rod is very tough, but could be hard to thread smaller bolts.  Mild steel rod isn’t quite as tough, but it easier to thread.  Brass isn’t as tough either, but is easier to machine and thread.  Solid nylon or plastic would be even better.  Not having nylon, I used brass.

First, you need to measure how tall the stand-off needs to be.  This can be done with a ruler, a depth micrometer for really precise measurements, or calipers.  For this project, the measurement was 23/32".

Make sure the diameter of the material you choose doesn’t contact any part of the circuit or components.  Metal contacting circuits can cause a short.  Large diameter material may have to be turned down for component clearance.

Then, you need to cut the material to length.  You can use power tools, like a parting tool in a lathe, or you can use a hacksaw.  With small materials I use a fine-toothed blade in the hacksaw.

It helps greatly to be able to cut uniform pieces.  The pressure applied by sliding the material through the hole and tightening the thumbscrew holds the material securely for cutting in this temporary jig.  

Don’t forget to add the thickness of the hacksaw blade, and enough so you can face off the ends without making it too short.

A lathe is needed for the next steps.

If the edges aren’t flat, chuck the road in the lathe, and face the ends off.

Take a center drill, which doesn’t flex, and start the hole in the end.

Switch to the proper size drill for the tap you are using, and drill the hole.  Drilling metal requires the use of oil on the drill bit.  The 4-40 machine screws I used needed a #43 drill bit.

Lincoln Machine Tap and Drill Chart

Starrett Decimal Equivalent Chart


Put the tap in a tap handle, with the centering tool, and use it to form the threads.  

Drill HQ - How to drill and tap metal

Cut the threads, clean the oil off, remove any loose shavings from cutting the thread, and you have the standoff.

If you want to screw the standoff into the chassis, you would need to turn one end down to the proper diameter, and use a die to thread it and a tap to thread the chassis.



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Comments:

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Comment by antedeluvianFebruary 5, 2018

This seems to be quite intricate and requires some specialised equipment. It all depends on the standoff distance that you need- McMaster-Carr carry standoffs in mm lengths. 23/32" is 18.26mm. Could you have worked with 18mm?  perhaps add a washer?

[ - ]
Comment by EdNutterFebruary 5, 2018

A washer would have been needed to raise the standoff, because of the way the display is set up.

It does require specialized equipment.  Companies that produce standoffs would have a much faster production method.  The lathe and tooling would be the most expensive part.  I make other things, so I keep taps, dies, and handles on hand.  The hardest part is keeping the tap from breaking in harder metal.

Another thing to consider is SAE vs metric.  I choose 4-40 hardware because it and the taps are easier to find locally.

Can you wait for the hardware to arrive?  A regular production company may not have to worry, they probably have inventory or the ability to have next day shipping.  If you're making a prototype, you should take into account the availability of the hardware you need to complete the project.  Do you have time to wait for it to arrive?  Can you buy it off the shelf?  Can you make it or pay someone to make it?

[ - ]
Comment by EdNutterFebruary 6, 2018

No lathe?  Try a drill press.


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