Nuts!

I’m using PC board to construct some custom enclosures. The materials and construction techniques will be the topic of a future posting here.

But in working out all the details, there’s an interesting challenge to bolting the box shut.

Specifically, you can’t cut threads in PC board material, nor can your fingers hold a nut in place inside the box while bolting it shut from the outside.

At a recent meeting of the local QRP ham radio club where I was first inspired to try this construction technique, I had looked at just such a box that had been made by Ken Lo Casale (WA4MNT). His solution was to solder the nut permanently in place inside the box inline with the through-hole. Remember we’re working with PC board material here so the inside of the box is all copper-clad. All you need is a soldering iron with enough heat to solder the nut in place. And that lets the nut “stay put” and accept the bolt from outside.

Looking at Ken’s handiwork, however, I had objected that steel nuts, the common type, wouldn’t take solder.

And I said that I doubted that Home Depot, Lowes or Ace Hardware would carry the brass ones in the small 4-40 pitch that was suitable for these small boxes.

Ken listened patiently and smiled. When I was finished, he said I should look at McMaster-Carr (on the Web). Not only do they have these specialty nuts, he said, but I also might find their web interface fun to use (in a nerdy sort of way).

And Ken was right. It is fun — and impressive!

So, if you’re the nerdy type and you’re looking for a very special type of screw, nut or bolt, or you just want to see how a company with a lot — and I do mean a lot — of variety in their inventory makes things easy to find for their customers, you can “follow the paths” I detailed below for what I purchased.

Brass Nuts

Machine Screw Brass Hex Nuts

First, the brass nuts:

  • Start at http://www.mcmaster.com/;
  • When their web page is loaded, click the picture of Nuts (not the one here in my blog);
  • Then click Hex Nuts;
  • Scroll the thread size box slightly and checkmark 4-40;
  • Just below the thread size box checkmark Brass;
  • On the right, click Machine Screw Hex Nuts;
  • Click the part# 95130A110.

On the left, I bought one bag (100 count) for $3.83.

Steel Bolts

Pan Head Steel Bolt

Next, I needed the matching bolts but went with steel since they didn’t need to be soldered — Note that I’m ignoring Galvanic corrosion which could be a mistake. Time will tell.

Here’s what I ordered:

  • Go back to http://www.mcmaster.com/;
  • Click the picture of the Screws & Bolts;
  • Click Machine Screws;
  • In Material, click Steel;
  • Scroll down to thread size and click 4-40;
  • Choose Drive Style of Phillips;
  • Choose Pan Head;
  • Choose 1/4″ length;
  • Select Pan (no washer);

I bought one bag (100 count) for $1.22.

Knurled-head Screws

Knurled Head Brass Screw

But initially, I will be using knurled-head screws since I plan to be putting them in and out a lot as I adjust things, show off the work and so forth:

  • Again, start at http://www.mcmaster.com/;
  • Click Screws & Bolts;
  • Scroll the right-side down to Thumb Screws (and click it);
  • Scroll down again and select 4-40;
  • Click Knurled;
  • Click With Shoulder;
  • Click Brass;
  • Where it lists the 1/4″ length, click the part# 98816A216;

I bought a dozen at $2.62 each (expensive devils!).

By the time I had completed my order (and explored a bit just for fun), I was really impressed with McMaster-Carr. I could only imagine the ocean of bins they must have with only one containing my 1/4″ knurled-head 4-40 brass screws.

Thanks, Ken!

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