Moulding Bench

[RobWilson]

hi here are some photos of my new moulding bench that i built this week.
I got sick of working on the floor, bad knees.

 

[Metal Mickey]

Very impressed Rob. Did you build it from scratch or 'adjust' something else? Bet its better on your knees though!

 

[xlchainsaw]

very nice rob. i see you have a good suppy of petrobond.sand. is petrobond any good for iron???

 

[RobWilson]

Hi xlchainsaw
The sand is Mansfield sand or Green sand (i know its red ;D) it's mainly used in the casting of brass,bronze and works well
with Iron , the sand holds fine detail like finger prints, letters etc. I have not tried Petrobond

 

[xlchainsaw]

thanks for the info ill check into it. there may be a similar type available over here in australia.

 

[4-6-4]

Dear Xlchainsaw. There are difficulties with what is called Green sand. and that is after you have aquired it. There is a place in Melbourne which supplies it ready for use. I can find out where if you are interested. The difficulties with greensand is after you use it. The sand is held together with clay this is burnt out when you pour hot metal into it. and has to be replaced you also lose the water content of the sand. The water content is 2 to 3 % more than this and the mold could turn into Mt Vercevious and a faulty casting resulting. The heat of the casting drys out the moisture content and the sand is lumpy and needs processing in a thing called a Muller. This is a drum with two rollers which rotate in it. The rollers are held off the bottom of the drum so as not to crush the sand
There are two plows mounted between the rollers which push the sand radially at the bottom of the drum. Operation Used sand in the top no cover required turn Muller on Bentonite (clay) added as required, after rotating untill the clods are broken up Water is applied Mix for a few minutes more sand is ready for use. to check for water content carefully grab a hand full sand and squeeze open hand a cod of sand will lay in said hand. shooing veins and the amount of sand sticking to the palm of the hand will indicate the moisture content. experience will tell if there is too much or not enough. Hand preperation of green sand is an arduous task.
I have been told that Petro Bond is OK for gun Metal and Aluminum and is a lot easier to prepare. This is an oil based sand.
Sorry if I have run off at the keyboard but it is a hobby horse of mine
yours 4-6-4

 

[oilmac]

Hi Guys,
A couple of hints from the foundry trade as a i was a greensand moulder, The correct moisture content is 4-6%water, I always tended to err on approx 5%, This was in using red mansfield sand, One soon got into a system where the feel of the sand "was just right" In the foundry i served my apprenticeship in one was left to take control over the state of their own sand I was making cast iron bronze , brass &aluminium castings
When making cast iron, the mixture was mansfield plus about 15% Scottish rock sand mixed through,, Our facing sand, was through the pan mill, or Muller
On brass bronze &aluminium, it was a straight red mansfield, Ones sand pile was used for years, and occasionally, one would add a shovelfull of new virgin sand to refresh the mix,(about once every two months) One can have the mixture too new The old moulders were meticulously careful of their sand, after casting ones moulds and knocking out the boxes, The labourer, would sprinkle some water over the sand, usually sparingly, and leave the sand for about 20 minutes till the steam permeated through the sand pile, Next the sand was flicked over using the shovel, and any lumps, were biffed with the back of the shovel, to break up the hardened /dried sand lumps, Then flicked back,
The next operation, was placing two lengths of angle iron across the bearers on the moulders sand tub, on top of these was placed a riddle with 1/4" mesh, the labourer shovelled in the sand , and yours truly or some other moulder shoved the riddle vigerously back &forward to sieve the sand into the tub This sand was left, at one end of ones tub, and one continued moulding with the sand previously left at the opposite end of ones tub till the fresh sand was cooled down (your average foundry labourer of 45 years ago, had as well as brute strength, to have a lot of common sense & skill, and a good one was a real advantage to the average moulder
Back to moulding, Ones facing sand was passed through an 1/8" sieve over ones patterns, in the moulding box, As the post has progressed on sand management, the amount of new virgin sand, is greatly dependent, on a) the metal thickness of castings being produced Heavy castings= greater sand burn as does the metal temperature
An b) some metals have a tendency to burn in to the sides of the sand mould metals such as phosphor bronze
These problems, can be greatly overcome by the application of a mould dressing, Which also gives a superior casting finish, Amongst the materials used
For cast -iron Graphite powder, or a mixture of graphite & coaldust
for bronze &brasses, peasmeal, or talcum powder
for aluminium talcum powder
Sometimes for heavy bronze greensand moulds we applied "white Blacking" No i have not taken leave of my senses! this was a mix of talcum powder &graphite powder On greensand work, all these dressings were applied by shaking the dusting powder through a muslin cloth bag, But dont go daft, Using too much.

I always used to use petrobond as a facing sand, on very delicate , &fine metal pattern moulding One application which i remember making, was the manufacture of tyre mould sections for agricultural tractor rubber tyre moulds, for the rear wheels
Unless you are making your moulds for the tiny castings a home craftsman is engaged on, a goodplan, is to scrape from your greensand mould, as much as possible when opened up,after casting Any adhering burned petrobond, as the black burned dust, forms "fines" which cloggs your greensand, and cloggs up the venting of your sand, and also repells the water for moistening.

 

[xlchainsaw]

very interesting oilmac thanks for sharing