Design question

[Lo/Rez]

My question is with regard to structure/strength. I'm in the process of building my 2nd friction folder. I was going to use titanium for the handle but didn't have any so I figured I might as well use stainless (1/8") instead of messing up more expensive material. I have 3/16ths pivots that I will also be using for the stop pin and stand offs/spacers. Would it be better to counter bore the inside of the handles and recess the barrels and have the hardware exposed on the outside, or trim the barrels to length and counter bore the outside of the handles and have the hardware flush (my preference). Or does it make a difference? Thanks in advance.

 

[Mike Read]

Not sure why you would want to counter bore on the inside?

If you counter-bore on the outside to make the fittings flush you will not have a lot of thickness left to support the pivot.

I personally wouldn't want the hardware exposed either so I would go somewhere in between. Counterbore 1mm to 1.5mm deep (40 to 60 thou) and dome/bevel the screw head. This way the screw will be slightly exposed but in a smoothed out way and you still have plenty of space for your pivot barrel.

I am pretty sure you are using the same pivots I have been using and it works a treat.

 

[Lo/Rez]

I was thinking there would be more strength structurally with the counter bore on the inside (with the barrels left full length and not trimmed to 0.165"). I'm not an engineer though.

 

[Mike Read]

The normal way to use those pivots would be to drill and ream a hole, the size of the pivot barrel, right through both scales and the blade. The screws then tighten up against the outside of the scales or a suitable counterbore. The barrel length would probably need to be shortened until blade play can be adjusted out with the screws. You can decide how much you want to shorten the barrel and how deep to make the counterbore, the deeper the counterbore the shorter the pivot barrel.

You could drill a smaller hole through the scales to fit the screws and then bore out from the inside for the pivot barrel, but I cant see any advantage in doing so and have never seen it done this way.

A shallow counterbore on the outside and bevelling the screws gives the best compromise of strength, ergonomics and ease of manufacture. That's my opinion anyway

 

[Mike Read]

If you are using pivots for the stand off/spacer you can do it the same way as the pivot but will need something to tighten up on. Either a spacer or some collars for stand offs.

It would make some sense to conterbore these fixings on the inside but you will probably find it much harder to do correctly.

Hope this makes sense