Mold Your Own . . . Valve Knob

When I was a kid my father would embed stuff in plastic . . . coins, photos, sea shells, whatever. I never thought much about it until recently. If you’ve read some of my previous posts you’ve seen that I have become interested in fixing up old stoves. The fixing up old stuff comes from my father getting my brother and I involved in old Hudsons (for those who don’t know, Hudson, Nash and Rambler merged in the late 1950s to form American Motors a.k.a. AMC, makers of Jeeps and Eagle cars, Gremlins, Pacers, etc. which was then bought by Chrysler in the 1980s), while the stove part comes from my interest in backpacking.

Well, I bought some old M1950 stove tanks . . . and windscreens  . . . and valve parts  . . . and pumps from a guy not too far from here. However, he didn’t have any valve knobs. I looked around in stores to find something, heck anything, which would work, but nothing fit. I asked around online at places where people would have such things, that is, collector’s forums, people selling on ebay, etc. but nobody had them. In fact, one guy mentioned that if I did get some to let him know as he’d like to have some. “Wonderful”, I thought, “nobody has any”. What to do? Well, why not make my own?

The M1950 stove, valve knob

The M1950 stove, valve knob

Remembering back to my youth, I recalled my father using that two-part plastic which also seems to be called epoxy. I did some research  and found a company called Smooth-On who makes pretty much everything I needed to make it happen. So, I asked a few questions about their high-temp epoxy, mold making silicones, and release agents and what follows are the results.

First, I needed to make a mold box. This isn’t for making the actual part, but instead for making the mold which makes the part. You embed the model, in this case the original valve knob, in clay and also some acorn nuts to help align the two halves of the mold. Then put it in the box, mix up some silicone and pour it on top.

This is the adjustable mold box I made with materials which were literally scattered around my garage.

This is the adjustable mold box I made with materials which were literally scattered around my garage.

After it cures for 30-45 minutes, remove the box and then carefully remove the clay from the silicone. Then put the silicone, with the model still in place, back in the mold box, spray on some mold release, add a filler hole made from clay, mix some more silicone and pour it in. After an additional 30-45 minutes remove it from the box and separate the two halves of your mold.

On the left is the clay in which the model is embedded. On the right are the top and bottom parts of the mold.

On the left is the clay in which the model is embedded. On the right are the top and bottom parts of the mold.

The front side of the knob mold came out just fine. However, the first mold of the backside of the knob had an air pocket in the screw-hole so, I remade it. It came out great . . . except . . . . . . the mold was difficult to fill and remove all the air bubbles which resulted in a less-than-full new valve knob (you’ll see this in a later photo). Bummer. So, I made a third mold, which wasn’t perfect, but I added some air vents to help remove the air bubbles. This worked better. (Third time’s a charm, I guess)

The two mold halves together, epoxy mixed and color added. 24 hours to cure.

The two mold halves together, epoxy mixed and color added. 24 hours to cure.

Here's the better knob prior to trimming the vents and pour hole.

Here’s the better knob prior to trimming the vents and pour hole.

After trimming the excess epoxy I placed the knob in a small toaster oven for 2 hours at 175F and then 3 more at 300F. This is partially what gives this particular epoxy it’s high-temp capability, which by-the-way should be roughly 100 degrees higher than the original Bakelite knob. We’ll see.

L-to-R, Original knob, failure knob, good reproduction. Also the face mold and the three molds of the opposite side

L-to-R, Original knob, failure knob, good reproduction. Also, the face mold and the three molds of the opposite side

I still need to work out the correct coloring, but it has been interesting to learn about plastics and what it takes to make your own things. I’ve got some more ideas . . . This is pretty fun!

Updated March 15th, 2015: The final version of this M1950 knob is now available at OldColemanParts.com. You can go there directly with this link: M1950 Valve Knob

Thanks for visiting my blog

Advertisements

5 comments on “Mold Your Own . . . Valve Knob

  1. […] I set out to make a reproduction valve knob last November, people asked how I could have known to do it the way I did. I couldn’t point […]

    Like

  2. wb6badstar says:

    I bought one for one of my M-1950 stoves, My first impresion was wow this looks good, Then the test fit, It was quite loose and had a fair bit of slop on the shaft, I got another stove down and removed it’s original knob and test fit the replacment on that stove, still loose. WelI I made a steel insert plate for the knob and got it to fit snug, Next to light the stove, It seems to allow for quite a bit of heat to be transfered in to the knob it seems quite a bit hotter than the bakelite ones, I wonder if it lacks the insulating properties of the orignal knob. When I turned the stove off I noticed that the knob seemed to have lost some of it’s rigidity and seemed to have a little flex in it. It returned to its original stifness after it cooled. It does make my stove look good once again and I wonder if it will hold up well enough to use the stove, or should I just display this one..

    Like

    • sklcolorado says:

      Thanks for the feedback. After the stove got hot the first time, I re-tightened the knob screw while to stove was operating. I tightened it firmly, and it hasn’t felt loose ever since. What I found was that the length of the flat spot on the valve stem can be shorter than the depth of the hole in the knob. Of course, this was true on the NOS Bakelite knob as well as it was used for the model. In fact, I could see where the valve stem chipped a little bit of the original Bakelite knob after I tightened it fully. The never used, NOS Bakelite knob didn’t fit tightly either, however, my older Bakelite knobs do fit snug. I think that both originals and my new knobs experience a little expansion when heating up, at least initially. I saw an original one for sale recently on ebay and you could see that the screw was still stuck in the knob. Try tightening it while the stove is operating. I’m wondering, are you using a 4-36 brass screw or is is a 4-40 screw? I got a 4-40 screw from a guy but it didn’t allow for the knob to get really tight. So, I found some 4-36 brass screws and it worked much better. I’ve used the knobs on two of my stoves so far, several times, and haven’t had any issues while boiling water. Let me know if you try this. Thanks

      Like

  3. wb6badstar says:

    First let me say I’m glad you are making these knobs, I was actually thinking of making my own after I found your blog. I will say buying one from MIke is way easier than sourcing the materials and making my own. I buy most all my lantern and stove parts from OldColemanParts.

    It’s funny you mention that you tightened the screw after it was running, I had done the same thing the second time I lit the stove. I did notice that I was able to get it a little tighter, I don’t want to over tighten it because I don’t know how strong the material is or if it could split from over tightening,

    I don’t know the thread count on the screw I have but I can say that I can thread it in quite easily with my fingers so I can only assume it is correct for the stem.

    I may take this stove out on a camping trip and try actually using it to make our morning coffee.

    Like

    • sklcolorado says:

      Hi,

      I’m wondering about any update on your use of the valve knob. Is it working okay for you know or are there issues?

      Best Regards,
      Steve

      Like

Leave a Reply

Please log in using one of these methods to post your comment:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s