Metal Casting Zone

Thanks for the comments on the furnace.The propane torch i am using is a 3" turbo torch thats 3" dia.as for the lid i was thinking of using one of those garden rubish burners that has a round steel lid with a 3" diamiter tube coming from the top and then fill it with refractory cement,do you think that will be suitable.You mentioned using zinc,what differences are there in the zinc to aluminium and could i not mix the two on a 1-1 ratio to give the aluminium more strength or would you just use one or the other.I will have a look on the website you mentioned. Thanks again guys Andy. p.s heres a pic of the bulldozer in mind.

you could mix your castings that is... zinc (potmetal) might be good in some areas for high detail. zinc melts at half the heat of aluminium and you could melt small amounts on just a ordinary propane stove!but its a b..... to grind off any excess which is common with casting .aluminium melts at a higher temp. its very prone to shrinkage so patterns when made are normally made a bit bigger to allow for this. due to shinkage you may lose some detail. i use a dremel and a rotary file and just carve or engrave any lost detail back in. aluminium is easier to machine than zinc. you must never mix and melt zinc and aluminium together!!!!this is a rule of thumb to stay safe!!! some zinc alloys have a little aluminium added!!! but leave this to the lab guys

Thanks for that.I was wondering is it possible to cast sprockets or would the teeth be to brittle.Its just the model needs some sort of drive system using sprockets and i dont fancy paying to have them machined as it would cost an arm and a leg.

ANDYO1 wrote:
Thanks for that.I was wondering is it possible to cast sprockets or would the teeth be to brittle.Its just the model needs some sort of drive system using sprockets and i dont fancy paying to have them machined as it would cost an arm and a leg.no problems with sprockets but..... your pattern will require draft. that is it will need to slope so you can draw the sprockets out of the sand. so your sprockets will have a slope on them which you will need to sand back and file.

study this picture of the wheels i cast and machined up with the lathe. look at the slant around the unpainted wheels...this is draft. the wheel with the red centre is my pattern and the others how they came out of the sand. the painted wheels have been turned up in the lathe. i hope this helps. i wouldnt use zinc on the sprockets. aluminium or brass would be ok!

you could all ways try casting them in lost foam, that way you dont have to worry about a draft. If you can imagine it you can probably cast it

the lost foam method would answer draft problems!im still waiting to give lost foam a go!

Thanks for that, that was agreat help.Love the casts of the wheels.You mentioned lost foam casting,what exactly does this involve and is it as easy proccess as sand casting.I think i will give the zinc a miss because of the high prices at the moment.Whats the difference between green sand and red sand.I am curentlly using red sand which cost me nearly $40 for a 25kg bag but they said it is already mixed with addatives i thought it was just a clay sand didnt know they added things to it.

You've got some petrobond. That should make some nice surface quality. Green sand isn't green, It's a clay/sand with water. It just means the bentonite clay is green as in unfired. I don't know how Petrobond would do with lost foam.