Tuesday, February 11, 2014

Yannick's Forrester mod.

A few weeks ago, a guy called Yannick, contacted me about a modification he wanted to do with his 111mm Forester and after some mails we agreed that I would post his report on the Blog. Here's the result...

Customization of my Forester 111mm

by Metalu

Hi ! I wanted to tell you a few things about the customization I have done on my Forester.

In a few words, the Forester is like the new 2008 Swiss Army Knife, with a corkscrew instead of the cross screwdriver, and red bi-material scales.

I wanted to test the “one hand” blade. After a few weeks of daily use, I find it wonderful and I can’t do without, now.

But the serrated blade is still a problem. It cuts very well, but it is difficult to make a straight cut, and fine work is impossible.

So I found a Sentinel with a non-serrated blade and did the exchange.

I also wanted to change the can-opener which I find useless, for a small blade that I want to keep very sharp.

Here are a few notes that I took during the disassembly:
the2 main rivets are Ø3.0mm. the 2 rivets on the rear are Ø2.5mm.
Here is a drawing of the rivet head (that we sometimes call « rosace » in french):

So I wanted to try something : instead of making new identical rivets, why not making screws with the head the same shape as the rivet heads?

That’s what I did. I machined them on my toolmaker’s lathe, and so the nuts, with the same head profile. My plan is to secure the thread with Loctite threadlocking glue. The glue can be desactivated by heating at 120°C (for exemple with a small blaze) If I want to disassemble the knife again.

This solution enables me to fine tune the rivets’ thightening and go backward if needed.

OK, the change of the can opener for a small blade is not obvious:

The root of the blades have the same profile. Starting well. But the thickness is 0.8mm less. A small Thickness shim should do the trick!

But the samll blade from a 91mm Victorinx SAK is done to cross the long blade on the left. And here, on the left there is the screwdriver. So I have to cheat to make it go on the right. Otherwise the blade’s tip is touching the screwdriver.

After taking the dimensions, I calculated that I needed 2 shims with 2° tilt.
assembly test: the blade is over-tilted and is touching the stainless steel liner.
try again ! new shims with 1.5° tilt (thank you my milling machine with tilting table)
Perfect! The blade is touching neither the screwdriver nor the liner.

Ho ! I forgot to say: rivet for a 91 SAK = Ø2.5mm
rivet from my 111 SAK = Ø3mm
So I had to drill the small blade to Ø3.
A high quality HSS drill-bit failed. I needed to use a tungsten carbid bit.

Time has come to do the assembly with my specially developped assembly tools : a normal screwdriver ! and for the nuts I found a bit that fitted perfectly after grinding it to the thickness.
On the following picture we can see the 2 thickness shims on each side of the small blade, and it’s alignment along the central liner, with no contact.

after that I fine-tune the tightening of each “rivet”, then secure them with the threadlocking glue, then put back the scales. I use a black scale for the corckscrew side in order to have a slot for the tooth-pick (no slots on the bi-material grip scales!)
and her it is! My wished ideal swiss army knife!
concerning the Sentinel, I assembled it with the serrated blade and the rivets from the Forester.

thank you for your attention