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Getting Screwed: Finding Mounting Hardware

A project log for WITCH-E Decimal Based Computer

Document and create a modern replica of the Harwell Dekatron computer known as the WITCH

Dave's Dev Lab 09/20/2017 at 00:271 Comment

For a project like WITCH-E, it isn't always "fun and games" with the electronics and research. Practical matters need to be addressed such as: How the heck do I mount all of these PCBs onto some acrylic? From a design perspective I wanted to use some very small screws to take up as little pcb space as possible. I also needed the method to be both easy and inexpensive as I would need mounting hardware for roughly 200 pcbs. My first thought was to purchase some off-the-shelf M2 screw kits with standoffs, then I did the math! Each box only contained 10 of the screws and standoffs that I wanted to use and at a price of around $6USD, that made each standoff with matching screw cost $0.60USD. Plus I would have to purchase 80 kits! So I continued to look. I found some inexpensive teflon spacers, and some 13mm long M2 screws at a decent price and decided on using them along with a matching nut. Well that was the plan... until I actually tried to use them. Threading the screw through the holes on each pcb while holding on the other screws and making sure the teflon spacers stayed in place was nearly impossible. So once again I went in search of mounting hardware. My first thought was to visit McMaster-Carr's website to see what was available. As recently posted on Hackaday.com (https://hackaday.com/2017/09/13/noobs-guide-to-mcmaster-carr/) McMaster-Carr has just about any kind of screw, nut, and mounting known to man in single quantities, and they had what I was looking for. Unfortunately, just like the kits, the M2 standoffs and screws were WAY too expensive to consider in larger quantities, so my next step was to try Ebay. After tweaking my search key words, BINGO! The pricing was much better, around $0.10USD for two screws and a standoff. So the moral of this little post is that buying the right mounting hardware can be tricky and that you have to be careful not to get screwed while trying to buy screws...

Discussions

Grant Likely wrote 09/21/2017 at 07:52 point

Don't forget about AliExpress. I get a lot of my bits and bobs from there, and shipping has always been very fast.

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