Will 2mm stock work for 91mm SAK center pins?

[hsherzfeld]

I'm looking to do some more 91mm SAK modding. Last time I did, I sanded 2.5mm stock down to (roughly) 2.25mm for the center pins. I'm definitely not looking forward to doing that again; the less time I have to spend in my un-air conditioned garage in Houston, the better!

I've ordered a pack of 2mm brass rods from Amazon, and my question is whether anyone knows if 2mm pins will work in the center (2.25mm) holes? The fact that the backside tools appear to have 2.5mm holes makes me concerned that those tools will be loose on 2mm pins.

[Poncho65]

Wished I could answer you but I really have no idea if it will work I am thinking it should but you will have a slight bit of wiggle

I haven't modded a SAK in a while with pin stock. I have modded one lately but was able to reuse the stock as the build was thinner than what I started with

Best of luck with it though

[hsherzfeld]

Thanks. I figured that it's worth a shot.

[SAKTaschenmesser]

I have a few 2.2mm pins left over, if you want them, even just for comparison, send me your address by PM and I’ll Air Mail them from un-air conditioned, grey (with an E), wet England.


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[tattoosteve99]

It will but the tools will be loose :/. Standard brass rod works at 3/32 but you will need to file/sand it down.

[hsherzfeld]

It will but the tools will be loose :/. Standard brass rod works at 3/32 but you will need to file/sand it down.

That's about what I figured. I'll probably end up filing down 2.5mm rod.

[Begin rant]: Why can't Victorinox just use a commonly-available size of rod for all of their pins? The backside tools already have 2.5mm holes, so their 2.25mm pins are undersized to begin with! [End rant].

[hsherzfeld]

I decided not to use the 2mm stock for pins in my latest SAK mod. Instead, I ground down 2.5mm stock by spinning it by hand against the bench grinder wheel, then sanded it smooth. It actually worked really well and was much faster than trying to reduce the diameter with sandpaper alone.

[kamakiri]

[Begin rant]: Why can't Victorinox just use a commonly-available size of rod for all of their pins? The backside tools already have 2.5mm holes, so their 2.25mm pins are undersized to begin with! [End rant].

A few reasons I’ve guessed at are:
 

• common dimensions with 84mm frame backside tools since c. 1951
• maximize liner material surrounding the 3rd/center pin (which were already prone cracking over time or when oxidized)
• minimize spring material when needed to wrap the 4th pin
• maintaining backward compatibility with scales

I decided not to use the 2mm stock for pins in my latest SAK mod. Instead, I ground down 2.5mm stock by spinning it by hand against the bench grinder wheel, then sanded it smooth. It actually worked really well and was much faster than trying to reduce the diameter with sandpaper alone.

It’s too much work to do by hand alone! I only turn pins when I need nickel silver, since I can’t find a source. But there are a few ways to get brass rod in 2.2mm at reasonable prices.

[ComboTool]

Not exactly the question, but I recently made a 74mm mod which mixed old parts (with 1.6mm pins) and recent ones (2mm). I was lazy and decided against redrilling everything to 2mm, so I used 1.6mm pins and it worked like a charm.

[hsherzfeld]

It’s too much work to do by hand alone! I only turn pins when I need nickel silver, since I can’t find a source. But there are a few ways to get brass rod in 2.2mm at reasonable prices.

To be clear, what I mean is that I hold the 2.5mm rod against the spinning grinder wheel and turn the rod between my fingers as I move it back and forth. This method does leave a slightly uneven surface, but some quick sanding with medium grit paper evens out the surface to a level that I find acceptable. It's not a perfect method by any means, but it was good enough to build this:

[Vidar]

An option might be drilling electrodes. Try googling "Single Hole Tubing EDM Tube". Add brass, copper or tungsten copper to the search as needed. Typically available in sizes down to every 0.01mm so you might want a tiny bit smaller than 2.25mm for easier fit.

0.25mm is a lot of slack for fitting metal applications. There are industrial standards for various kinds of fit though. If you want a tight but freely rotating fit after lubrication you can try to keep to similar slack as those. An example of a calculator for standard ISO fits and tolerances are at https://amesweb.info/fits-tolerances/tolerance-calculator.aspx. To get an idea of the tolerance range for a hole of nomimal size of 2.25mm with free but tight fit try putting in nominal size 2.25, hole tolerance H7 and shaft tolerance g6. (Or H8 and f8 for a somewhat looser but still close fit - good enough for this application I'd think).

[tattoosteve99]

A rougher surface actually works better in some cases. Oil will actually stick to it. And once it works in sometimes it catches the oil really well. I’ve heard some people say to polish it up, I tried that once, and only once. It galled up and I had to remake it.

[kamakiri]

To be clear, what I mean is that I hold the 2.5mm rod against the spinning grinder wheel and turn the rod between my fingers as I move it back and forth. This method does leave a slightly uneven surface, but some quick sanding with medium grit paper evens out the surface to a level that I find acceptable. It's not a perfect method by any means, but it was good enough to build this:

Understood. I mean that I only fabricate/turn nickel silver because I can’t buy it in 2.2mm or 2.25mm. I buy the brass because it is available, but typically from overseas.