TECH: How to make a sand casting master in your basement

It’s easy and fun to make your own aluminum hot rod parts. You can be the next Weiand, Offy, or Edelbrock. And you can have the bragging rights that you made that cool part yourself, right in your own shop (or in my case, basement).




The Basics

To make the master for the casting, the only materials needed are wood (I used aspen), wood glue, bondo, and tools that you likely have in your shop. If you have a few woodworking tools as well, all the better.



If you have an idea of a simple sand cast part that you’d like to make, the only limitations are that the master you create for the part must be able to be removed from a two-part mold. This means, when you are designing the part, make sure there is a parting line (high spot) somewhere that will allow the master to slip out of the sand molding halves without breaking loose any of the sand. There needs to be a “slope” or draft to the walls of your part of approximately two degrees. With simple sand casting there cannot be any hollows or porting inside the part, but you can machine those later if required.

An intake manifold cannot be made this way, but a valve cover could. You couldn’t make a carburetor, but you can make the air cleaner.

I had an idea for a bracket to hold a Fram canister fuel filter. Fram supplies a simple folded steel bracket that takes up less room, weighs less, and is probably easier to install. But I thought my part would be neater, so I made one. I wanted something that looks like it could have come from the Edelbrock foundry in its heyday.

 

The Steps

The first step is sketching the bracket from a side view and a top view. Make the sketch to actual finished size.





When transferring your sketch to actual patterns, you will need to then upsize the part approximately 102%. This will account for shrinkage that occurs as the aluminum (or brass) cools in the sand mold. Making this 102% adjustment can be done by drawing the pattern with a sand casting ruler (make your own by xeroxing a regular ruler at 102%), or just xeroxing the actual size pattern at 102% before cutting up the upsized copy.

After you have your patterns, cut them out and transfer to your wood. A pencil around the outside edge is close enough. I use a bandsaw to cut the wood, but a jigsaw will be fine.









Hand sanding, or careful use of an air grinder with some 80 grit, can be used to fine tune the rough pattern parts. Cut all the pattern’s parts and you are ready for gluing.



On my part, I wanted the back panel to have some raised bosses where the mounting bolts would go, so I used a carbide tipped routing bit in my drill press as a poorman’s mill. Be careful, as the bit will grab the wood if you don’t hold on tight. Then, touch it up a bit by sanding the edges to create a slightly rounded edge.



Using rubber bands to hold the parts during gluing is a good idea if a clamp or vise won’t hold the odd shape.



After all the sides are glued together, do most of your major sanding to shape. Then add bondo to inside fillets and to create the required draft to the walls of the part.



On this part, the parting line in the mold will be the far back edge. This means that basically the whole front of the part will be in one side of the mold, and the back half of the mold will be a flat side of sand. You can see how my triangle sides are fatter at the back, and the middle web tapers toward the back as well. The wood stock was approximately 5/16 inch, and the rest was built up with bondo. This will allow the master to be removed from the sand mold without breaking loose any sand.

Using a short sanding block works well on the simple flat sides, but sometimes you need to improvise in the tight spots. A short length of pencil works better than a finger when sanding the fillet inside. Sand the parts up to a 150 grit smoothness.



I like to think that some day a future hot rodder will find these parts on a car, and read the name cast into them, wondering how he found this rare 1950’s hot rod part. I make sure to put my name on most of the parts I make. I usually put a part number on them as well, and in this case it’s the number of the Fram filter insert. I use small plastic letters from the name plates on the wall at work. I think anything similar would work as long as they have enough of a draft on the sides. I epoxy them direcly to the wood.





A test fit of the part would be good at this time, but remember that master you just made is 102% of final size.



Then prime, block, spot putty, block some more, and give a final coat of smooth Krylon. Remember that any rough spots on the master will show through on the final cast part. Sometimes the sandcast roughness of the final product may hide a bit of sloppyness on the master, but I prefer to do the work now rather than later sanding on the aluminum.



I send the master to a local aluminum foundry that does one-off and short runs of parts. They cast in many different alloys, but I had them cast this in 356 aluminum. It works well for many different general applications, and will polish up nicely, too. I would think most metropolitan areas would have a foundry willing to do this type of work. For this part, the turn-around time was about one week, and cost about ten dollars. I may be lucky and have the most friendly foundry around, but I bet most of you could find something similar near you.





Note the flashing on the fresh part. I usually request the foundry to NOT sand this off, just to make sure they don’t sand too much and get into the part. Some of the things I make are delicate, and if they sand too far I don’t have any room to smooth it out. I think you may want to do the same. You can grind the flash with a fresh 36 grit disc, then block it with 80 grit.

I took this part to a friend with a mill where we bored the through-holes and counter-bored those holes on the drafted surfaces. Wish I had milling equipment at home, but he thinks it’s fun to help make hot rod parts.



After a cleanup sandblast, much sanding and buffing of the sides, and mounting, this is the final product.






Thanks to Madison for the camera and extra hand, Kloppenborg for the casting, Gary for the milling, Chris for the blasting, Dad for the buffer, and Mike for the editing and posting of this thread.

 

i like it very cool , i would have been lazy and tig welded one out of stainless steel though lol

 

You make it look so EASY!!! NICE work.

 

Now that is just too cool!

 

Nice job. Casting is fun!

 

Very nice! I need to find letters for a project I have to make.

 

Here is one of mein. A 2x4 lid for a Wiend 440 Superstock bottom. Nice tech and this stuff is fun.Thanks for the post.
Don
Still have the master in the basement.

 

Very nice piece!

 

That is very cool. Thank you for posting this. Definatly opens some eyes to what can be done.

Jeff

 

You knocked me right out of my chair dude!!!!

 

Way too cool tech! I have been wondering about some of this and this thread has answered quite a few questions I had. The 102% was one of them as I knew it shrank. I also have one of those filters I need to mount and this has got the wheels turning. There's a lot of possibilities. Thanks for submitting.

 

Impressive....

 

Nice job, I just don't get into wood work not my bag, I am looking for someone to make patterns of some rather large window frames here on the central coast if anyone knows of somebody.

 

Very nice, great tech! I had a complete casting setup from a high school shop, but didn't have room for it in my garage, so I sold it to a friend who expressed an interest in it, for what I paid. He turned around and sold it for a profit.
Anyway, if anyones interested in setting one up, talk to the metal shop teacher (if your school has one) at your local high school.
I got mine at scrap value because he said he couldn't trust todays kids around anything like that anymore.

 

That's a great looking part. Thanks for the tech.

 

Great tech post, thanks.

 

That is a piece of art to bad it is hiding next to the frame.

 

great post indeed!! i know we all have a part somewhere on our car that would just look cool like that

 

That's awesome!!! $10 is a steal ! The minimums required around here make it too expensive to cast anything. Nice tech article!

 

Awesome idea and execution! Very thorough and well written post, I really enjoyed the read.

 

Super Tech spot. Thanks. So what would it take to cast the part yourself? I understand that for $10 it's not worth your effort but I'm curious. I assume getting Aluminum molten would be one issue.

 

Awsome tech. This is something allmost anyone could do and it would really class up a car.

 

Thanks for sharing! Way too cool.

 

You win.

Maybe you could post up the name of your foundry... and guys could easily mail something to them to cast up... even if you add shipping costs to the part, it's still hecka cheap for a one off that nobody else has.

Awesome idea... great execution.

Sam

 

That rules, I just wish I had the talent & patience to make stuff like that.

 

Very impressive! Especially like the detail of the lettering.

 

Real nice work. The best part will come in future years when on some board the "Experts" will be telling everybody about the company responsible for making the parts. And they will post their evidence to back themselves up to.

 

looks great ..love the keen attention to detail and $10 is the right price

 

Re foundry finding. I have discovered that there is hardly a decent sized town without being someone casting aluminum. Like here I know of 5 with in 25 miles of me. If I know 5 there are probably ten. I found one factory that uses aluminum to clean their foundry stuff so if you need something small the night shift guys will do it to keep themselves awake while doing their alumnum pour. I get the impression the boss there doesnt care as long as it doesnt interfere with their work as they are learning skills that they would not have and it is costing little or nothing for them to learn.
I got these done that way but I was not told who did them and told not to ask. Just a friend of a friend. I made the master (left photo) from an old carb bottom and lots of JBweld , some lathe and filing work and paint. I have tried casting at home. The melting and pouring is easy but making mold boxes was not my thing.
Your filter bracket is a work of art. Very nice professional looking piece.
Don