alloy casting - best finish

[eskimo]

what does one use to get a smooth finish on a alloy casting?

Is standard Petrobond that RayG refers to in casting101 ok? or is there something else/better that ensures best finsh.

I guess a finer sand would give a better smother finish than a course sand..is that right?

Just how smooth can one get a alloy casting?

Would lost foam give a smooth cast?

[Oldneweng]

Based on YouTube video's only, finer sand and careful packing/ramming. I am not sure about lost foam, but I suspect it would not be ideal because it is soft and that limits the rammimg. It would still depend on the sand anyway.

Dean

[bob ward]

As you surmise eskimo, using finer sand gets you a better finish on your aluminium alloy casting, petrobond sand is reputed to provide a finer finish than green sand. I use petrobond but I've never used green sand so I can't offer a comparison from personal experience. The lost foam process is just another method of sand casting.

If you look at old Australian made hot up equipment e.g. EH Holden twin carb manifolds, the surface finish on those is about the best you are going to get from sand casting.

Lots of home casting info here AlloyAvenue network (http://www.alloyavenue.com/vb/forum.php)

[ratters]

Hi Eskimo, I have not tried this myself yet but in a YouTube channel I follow called 'Makercise (https://www.youtube.com/channel/UCZnQYVCCnNnwqiJRIYQuYdA)' he was able to get a very smooth surface finish on his aluminium parts by painting his lost foam with plaster of paris. I was impressed enough that I intend to give it a shot myself.

[Oldneweng]

That sounds like a good idea. The trick would be to get the foam to the right pattern shape first. I was thinking of lost foam as a way to get rough shapes for later machining. That would be my main reason for casting, just to get the right size material to machine something. If only other jobs would not keep coming up taking my time.

Dean

[eskimo]

Hi Eskimo, I have not tried this myself yet but in a YouTube channel I follow called 'Makercise (https://www.youtube.com/channel/UCZnQYVCCnNnwqiJRIYQuYdA)' he was able to get a very smooth surface finish on his aluminium parts by painting his lost foam with plaster of paris. I was impressed enough that I intend to give it a shot myself.

I think he got a reasonably good finish partly because he used a hot wire cutter when cuttting the foam which leaves a good finish. The plaster is there to stop the molten alloy to contact the rough sand????

[ratters]

I suppose the plaster reverses the surface finish from the sand mould to the lost foam instead? I think you need to have a go and show us all how it went :2tsup:

[eskimo]

I suppose the plaster reverses the surface finish from the sand mould to the lost foam instead? I think you need to have a go and show us all how it went :2tsup:

now I gotta make a hot wire cutter..bugga

[China]

You may want to investigate "Delft Clay"

[Oldneweng]

You could also try investment casting although the cost may be a bit high to get started initially.

Dean