What Material to use for Casting Pattern

markz528 · Feb 12, 2019

I need to make the alternator bracket for my 65 Fury cop car as I have been unsuccessful in finding one (see picture of my first prototype pattern). It will be sand casted out of ductile iron. I have never had anything cast before.

Made the first prototype from oak. That did not go too well. Oak seems to be quite porous after machining, and it actually pulled some material in spots.

Made some adjustments to the shape and made the next prototype out of poplar. Again the finish is not great but no pulling and I would like to use a better material that will finish better.

Someone suggested Maple. I can get Maple but not that easily. Is Maple the right choice or is there a better material to use for a sand casting pattern that will be used to make 2 castings?

adama · Feb 12, 2019

Honestly why not just machine it either out of Alu or a block of steel? Will be way cheaper than a 2 of casting cost.

johnoder · Feb 12, 2019

There is more to a pattern than making a non metal look-alike

Like draft and shrink

After doing all that machining, why not just metal ones???????????

jdgoguen · Feb 12, 2019

My grandfather ran a pattern shop. All the patterns were made with straight-grainad mahogany and finished with lacquer. Draft and shrink are critical. Was fillets were used to avoid sharp corners.

Jon

markz528 · Feb 12, 2019

adama said:
Honestly why not just machine it either out of Alu or a block of steel? Will be way cheaper than a 2 of casting cost.

Price is not bad. Local foundry will cast 2 of them for $100.

The car is an anal restoration. Its a 1965 Plymouth 2 door cop car that my great uncle bought at auction in 1966. I am going through great pains to make the car as original as possible. It's sentimental to me. In my opinion a non cast bracket would just look out of place in the car. Unfortunately my great uncle converted to power steering and when he did he moved the alternator and threw the brackets out. Fortunately I have the alternator and a couple of the brackets.

I like the thought of mahogany.

markz528 · Feb 12, 2019

I have minimum of 1/2 degree draft everywhere. Shrink will not be a problem with the tolerances I am dealing with. I did make a slight adjustment for shrink.

Mark Rand · Feb 12, 2019

The other woods would do the job with filling and varnishing.

Don't forget the correct shrink allowance!

TDegenhart · Feb 12, 2019

Hard maple is a favorite.

Tom

Bill D · Feb 12, 2019

I thought apple wood was the best?
Search the site for casting with ice patterns from Russia or Ukraine. How about lost wax?
Bil lD.

tomjelly · Feb 12, 2019

3d print in PLA and burn it out for casting. This guy has some great videos of the process he used.

YouTube

L Vanice · Feb 12, 2019

jdgoguen said:
My grandfather ran a pattern shop. All the patterns were made with straight-grainad mahogany and finished with lacquer. Draft and shrink are critical. Was fillets were used to avoid sharp corners.

Jon

The pattenmakers where I worked usually used an imported wood that looked similar to mahogany, but was from southeast Asia. I have a few pieces, but I have forgotten the actual name. I have used maple for patterns.

Separately added fillets are usually made of wax or leather.

Wood patterns need to be sealed with lacquer, varnish, enamel or similar. The mold maker will also dust it with mold release powder before adding the sand.

Larry

Shaybuilder · Feb 12, 2019

I don't think 1/2 degree is enough draft especially on the deep section, too much chance of tearing the sand when pulling the cope & drag. I make a lot of patterns for a iron foundry and I try to keep a 3 degree taper.

motojoel1 · Feb 12, 2019

L Vanice said:
The pattenmakers where I worked usually used an imported wood that looked similar to mahogany, but was from southeast Asia. I have a few pieces, but I have forgotten the actual name. I have used maple for patterns.

Separately added fillets are usually made of wax or leather.

Wood patterns need to be sealed with lacquer, varnish, enamel or similar. The mold maker will also dust it with mold release powder before adding the sand.

Larry

Jelutong, if I spelled it right.

Spruewell · Feb 13, 2019

The wood you carve your pattern out of is immaterial. Especially for a run of 2 parts. Just fill the porous grain with putty or Bondo and varnish the heck out of it until it’s smooth. The most important thing you will need to consider using green sand is draft angle. 1/2 degree is not nearly enough unless you are using resinated sand which uses a resin binder to “glue” the sand together and create a much more stable mold. Typical green sand will require a minimum of 2-4 degrees of draft angle.

Peter from Holland · Feb 13, 2019

Draft angle depend on the hight
A draw spike tool is used for rapping the pattern gently the loosen it from the sand to assure a clean draw.
So if its low like half a inch you can even do with no draft
And for smaller items that will also compensate for shrinkage
For a run of 2 any wood will do if properly sealed
All patterns are sealed anyway AFAIK

Peter

Mikel Levy · Feb 13, 2019

markz528 said:
...made the next prototype out of poplar. Again the finish is not great but no pulling and I would like to use a better material that will finish better...

Are you sure that was poplar? Poplar is a close-grained wood (which is preferable for a pattern) and should present no problems in achieving a smooth finish with common oil-based varnishes.

--Mike

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What Material to use for Casting Pattern

markz528

Hot Rolled

adama

Diamond

johnoder

Diamond

jdgoguen

Aluminum

markz528

Hot Rolled

markz528

Hot Rolled

Mark Rand

Diamond

TDegenhart

Diamond

Bill D

Diamond

tomjelly

Stainless

L Vanice

Diamond

Shaybuilder

Cast Iron

motojoel1

Cast Iron

Spruewell

Hot Rolled

Peter from Holland

Diamond

Mikel Levy

Aluminum

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