How Would You Fabricate/Manufacture Two Chainsaw Parts - One Aluminum and One Rubber

Fellas -

I collect and refurbish old chainsaws in my spare time, and sometimes you run across parts that are super difficult to find on a fairly common saw. That's what we have here -- the Stihl 1111 series saws were big beastly saws from the 1970's - either 89cc or 111cc. They are a professional grade saw that was often used commercially. Collectors are starting to pick them up now. See picture of one (minus handle) next to a normal-sized 62cc saw.

Anyway, I have 7 or 8 of these, depending how you count. And they came with both a half wrap handle (for your left hand, it's on the flywheel/left side of the saw) and a full wrap handle (wraps around to the clutch/PTO side of the saw). Full wrap handles are actually fairly plentiful and not very expensive ($50 or so for a decent one), but there are two specific pieces that are needed to mount the full wrap.

First is the mount, which is part 1111 791 1907, or part 37 on the attached screenshot. It's either aluminum, magnesium, or an alloy with both. Reproducing in aluminum would be fine.

The other is the sealing ring, which is rubber with an embedded metal ring (I'm not going to worry about the metal ring at this point).

I have attached a few pictures of each. The mount is slightly chewed up because of where it's mounted - if the chain comes off, these catch hell.

I'm not worried about something being correct for a restoration. I just want something that will work.

So, how would you reproduce the metal piece? I know it can be CNC carved out of aluminum, but that might be cost prohibitive. I'd like to have some to keep and some to sell. I wouldn't want to pay more than $20 each if I'm going to re-sell these at about $30 each. Is 3D printing in a composite an option?

What about the rubber piece? Seems like this can be made using a mold or on a lathe. It's made of the same rubber that chainsaw anti-vibration rubber isolators are made from (or at least it appears to be).

Thanks in advance for any input!

Scott

Pics of the rubber piece.

For the metal piece it looks like a cast piece to begin with and you could look into trying to cast another one. Given the chain whip aspect replacing metal with metal makes more sense as opposed to a 3d printed replacement. If you wanted something to look right you may be able to get close with 3d printing to make silicone molds and then cast metal parts from them.

Unless you needed a ton of these I think any cnc work to get to that shape would be cost prohibitive as there are a lot of shapes involved. If you just needed a functional piece you could probably get something done for cheap, local fab, buddy welder, send cut send etc.

For the rubber piece start hunting vibration isolators or find some equivalent durometer rubber tube for the o.d. and drill a hole through the middle for the i.d. or maybe you can find an exact piece in those dimensions at McMaster carr or something like that.

Any chance of a similar sized part on a current production saw?

You might talk to these guys about the rubber part: http://www.jbmindustries.com/index.html

I have no affiliation, other than hearing about them on a Yamaha XS650 forum. I have no idea what a minimum quantity might be...but if it's in the hundreds it might be feasible. The rubber part with a metal ring seems to be in their wheelhouse.

I could see doing the metal part as a steel fabrication for low quantities. I would turn the round bit on the end on the lathe, and do the half round saddle by splitting a piece of tube the appropriate size. Connect the two with a tab and add a couple of weld nuts for the threaded part and it would be a workable piece that is likely stronger than the original.

You can lost wax cast it using a 3D printed part that has been designed with the shrinkage built in ,

you can also make a silicone mold from a modified original to make waxes to cast ,

There is a small book titled "How to cast small metal and rubber parts" By William A Cannon. Mine was printed in 1986. ISBN 0-8306-0314X and the paper back is 0-8306-0414-6.

I found my copy several years ago on ebay, and since it wasn't written by suess I imagine it to still be found if you put it on you notification list.

The rubber part is very suitable to be cast in a two part aluminum mold turned on a lathe(techniques in the book).

The metal part would be suitable to be cast in bronze or aluminum. Its small enough you could either make a tiny electric furnace or even heat the metal with a large rosebud in a small steel crucible. A 3d printer would be nice to make the pattern as you could design in Cad and then just scale it up 2-3 percent to account for shrinkage

It'll be hard to machine 15 or 20 of the metal parts at $20 each if you're paying somebody to do it all. An hour or two of design time to reverse engineer and simplify it (remove the ribs, fill in those areas, if you don't want an exact copy), an hour to either program it for CNC or make a 2D drawing for a manual job, buy a piece of 2" round rod, and you're already at your $300-400 budget without turning on a machine. And it'll probably take a 4 axis mill to do it efficiently in one setup w/o custom fixtures. Unless you've got a hook-up, that's $100/hr if done @ US labor rates (I'm in CA, and pay more than that, but we're $$$ out here). 3D printing in metal will also be over budget if contracted out.

Doesn't mean it's not worth doing--just means it's a labor of love, not a profit making deal. If you got somebody to draw it, you could probably get them machined overseas (eg Taiwan, to avoid the tariffs) for $20 ea @ qty: 50.

For the rubber parts, you can cast silicone in 3D printed molds. Lotsa videos on YouTube. Under $100 in materials (two part silicone, release agent, some cups and sticks). That's a simple part for which a mold can be CAD'd up from a hand sketch in 30-45 min, then 3D printed for cheap in PLA plastic. Only question would be if you can match the stiffness/hardness of the original part with the available silicones.

You could try making a silicone mold then making the piece from Devcon or JB weld. For the rubber bushing I would go through the Thomas Registry for bushing or seal manufacturers. Use or modify something similar.

https://www.thomasnet.com/articles/top-suppliers/manufacturing-companies/

Appreciate all the input. I found someone who made the aluminum pieces at $45 each, which I thought was quite reasonable.