Making pogo pin test jig - what to use for guide rails?

Thread Starter

seanspotatobusiness

Joined Sep 17, 2016
190
I would like to make a jig for testing LCD character displays. I imagine using some springs on some smooth metal cylinders to return the jig to the open position when the clamp is released. What can I use for these smooth metal cylinders? Please see this sketch to see what I'm talking about (I highlighted one of the cylinders - it has a blue outlined box around it). Thanks.

I'll be using laser-cut 3 mm acrylic, Pogo pins Veroboard and a toggle clamps to make the jig.

 

Wolframore

Joined Jan 21, 2019
1,254
How many cycles do you want. Hardened tool steel for high cycle. Bronze is pretty high cycle too. Brass won’t last as long but easy to machine. Aluminum galls not recommended. Plastics have come a long way. Recommend different material for plate and pin. For instance. Bronze and tool steel is a good combo and will reduce galling as well.

Just reread try brass if you’re using acrylic.
 

Thread Starter

seanspotatobusiness

Joined Sep 17, 2016
190
My question was not so much about the material but whether there were mass-manufactured articles that would serve this purpose, perhaps with screw threads allowing them to be screwed into the plastic or something? This is just for hobbyist use and will see <1000 cycles.
 

Wolframore

Joined Jan 21, 2019
1,254
I would use threaded sleeves and screw them in from the bottom. Locating the holes will be another challenge. They’re usually done with what’s called transfers. But maybe you can figure that out. It takes a lot of tool to do even simple machining especially when it needs to be precise. Threading directly into plastic won’t last long.
 

jpanhalt

Joined Jan 18, 2008
7,879
Have you considered simply hinging the pogo pin mount? Piano hinges or even separate hinges can give accurate alignment and mounting can be through-material screw and bolt with slots for adjustment.

upload_2019-5-22_6-28-11.png
 

Thread Starter

seanspotatobusiness

Joined Sep 17, 2016
190
Have you considered simply hinging the pogo pin mount? Piano hinges or even separate hinges can give accurate alignment and mounting can be through-material screw and bolt with slots for adjustment.

View attachment 177955
Thanks but unfortunately I can't really use a hinge because the jig needs to press against two different sets of pogo pins that are aligned perpendicular to each other. I want to be able to use with LCDs with different pinout arrangements.




Shafts and linear bearings are cheapish and would last indefinitely. It you prefer, you can use bronze bushings.

https://www.amazon.com/dp/B01MTLSZFQ/

https://www.amazon.com/Uxcell-a14021800ux0723-Steel-Turning-6mm200mm/dp/B00LUSVKVY/
Would the shafts be attached to the bottom and the bearings attached to the Pogo pin mount? How would you mount the bearings?
 

Wolframore

Joined Jan 21, 2019
1,254
I would just turn some stainless or even brass if it's low cycles on a lathe for this..... you can put steps in it for washers and spring load it.

Do you have room to place them next to each other? The hinge idea is the simplest and very repeatable... I'm sure you need 0.5mm tolerance to make this work correctly.
 

Yaakov

Joined Jan 27, 2019
1,536
Would the shafts be attached to the bottom and the bearings attached to the Pogo pin mount? How would you mount the bearings?
The bearings would be press fit into the moving part of the device, flush with the bottom surface (or slightly proud).

The shafts would be press fit into the bottom. If the thickness of the bottom isn't enough for mechanical integrity, they could be reinforced with something, even adhesive.
 

Wolframore

Joined Jan 21, 2019
1,254
For press fit you need about 0.001" tolerance.... can't do that with a drill, ... you need a mill or at the very least an accurate reamer. Might be better to go with a bearing mount that can be mechanically attached to the stage.
 

Thread Starter

seanspotatobusiness

Joined Sep 17, 2016
190
I'll be using a laser cutter to make the holes but I don't know how accurate it is. I have a tap and die set so I could thread the bottom and the shafts and I do have some 1 cm thick acrylic I could use for the base.

Maybe a hinge would work okay, though. I'm not very good at modelling mechanics in my head!
 

Yaakov

Joined Jan 27, 2019
1,536
For press fit you need about 0.001" tolerance.... can't do that with a drill, ... you need a mill or at the very least an accurate reamer. Might be better to go with a bearing mount that can be mechanically attached to the stage.
In acrylic you've got more latitude since it is far more easily displaced. Even nylon bushings would probably work in this application.

In any case, a close press fit hole with adhesive would work.
 

Wolframore

Joined Jan 21, 2019
1,254
It can also crack easily... but I still like the linear bearing idea it's better design... bushings and glue would work.

Lasers can make out of round holes and have divergence issues at the bottoms of the holes... Glue is one method. Perhaps best is to drill undersized holes with laser then get them to final size using a reamer. Duct tape and glue method might work... as long as there's not heavy load on this joint.

I have been known to over build things.
 
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