The Stovebolt Site Forums The Shop Area Interiors Here is the step by step guide to casting knobs

I have successfully cast a new knob for my heater, so I thought I would show you you how it is done. It is not hard and it only takes about an hour of work. It takes about 8 hours for the rubber to cure so the entire process will take about 24 hours. The resin hardens in 5 minutes, so once the mold is made you can make parts quickly.

http://moldingheaterknob.blogspot.com/

That's very cool - I like your inventive use for Lego's, too.

Time to put an ad in the swapmeet section and let the orders start rolling in.

I've used the same product for making parts for model cars. Good stuff. A tip for those that want to try this, go to the local Hobby Lobby. They carry Alumalite. Not necessarily the full line, namely the tan resin, tinting dyes, and 2 different types of mold making silicones, plus kits (large and small) that have all the supplies. For making knobs, I would suggest the small kit (about $30) for the average truck restorer. And to make it even more economical, go to their website and check out the weekly coupon. Most of the time, it will be a 40% off any 1 item in the store, which can save you some $$. There is also another product by the same company called Amazing Casting Resin and Amazing Mold Putty. A little easier to use, but the mold putty is better suited to 1 peice molds, and may not be good for making knobs.

I don't get it Jeff, the article stops at step 6 and I can't fine any way to go to the next page.
Denny Graham
Sandwihc, IL

Click on step 7 in the right hand column.

Then step 8

And so on...

You can also click on "older posts" on the bottom of the page to go to the other steps.

Cool, nice job Jeff and that is, the recycling at it best, using the kids Lego's for a mold.
Now how are you attaching this to it's mate?
Denny Graham
Sandwich, IL

This resin is tough stuff and they can be drilled so they can be attached with screws.

Jeff, nice write up with pics! I do molding on the side as well. I use smooth-on's product line http://www.smooth-on.com/ They have a good vareity of urethanes, silicones and resins. I mainly use their 300 hard plastic or 326 fexible plastic products. Molding is fun! I am working on a vent cable sheath right now. But it is tricky because one half needs to be rigid and one half needs to be flexible, but its all one peice! I am using a metal dam in the mold and will pour both the hard side and flexible side at the same time. Then when both are the same level before curing I will pull out the dam and let them mingle in the center

Denny, After you pour the resin into the mold stick it under that bell jar of yours and pull a vacuum on it to suck out all the air bubbles. Resin castings are prone to having trapped air bubbles that invariably wind up next to the mold resulting in holes in the cast part.

Yeah Woody, I'm aware of that. I used to do a bunch of resin casting and carbon fiber work when I was a tech at the lab. We had some real fancy vacuum equipment, ovens, pots and autoclaves. I'ze just interested in seeing how the other guy does it, ya just never know, they might come up with some trick that you never would have thought of.

Generally epoxy resin is quite brittle even with fillers added; but the urethanes can be formulated as hard as a rock or soft as a baby's butt. And they are very tough and not prone to cracking.

Many epoxy resins under vacuum will continue to outgas bubbles till they cure, it's because your boiling off the volatiles with a low vapor pressure in the resin. The absolute best way to get a solid casting in an epoxy is to cure it in a pressure pot, but most people don't want to spend that kind of money.

Denny Graham
Sandwich, IL

By the way, how’s that truck coming along? You orta be bout ready for paint, no? I’m helping out a buddy on his ’50 and we just got into the floor boards the other day while working on the parking brake system. Where did you buy your sheet metal from, it looked like most of it was pretty good? No surprise but he’s gonna need to redo the front cab mounts also. But it doesn’t look like he’s gonna have to go through as much as you had to endure. You can bet, we’re gonna be studying your album pictures when we get into it.