Acceptable castings from Kit suppliers.

[Basil]

Being very new to this field I would like to know what do you consider is acceptable quality when receiving castings. I returned the top casting that was generally not bad but had some porosity in the barrel area which I was worried that after machining it could break through. I returned it and was sent this. Am I being too picky?

 

[TonyM]

IMHO you are not being topo picky. They are all poor quality castings.

 

[Charles Lamont]

This looks like a Seal or Seagull carburettor casting (from Hemingway)? With the first one I can see some kind of problem but the photo resolution is not good enough for me to work out what.

Looking at the blue one, greensand castings this small are rarely going to be pretty and will need a lot of hand fettling to look nice. You are lucky to get one in which the two halves of the mould seem to have been very well aligned. It is important to thoroughly measure the casting to make sure it is possible to get the finished part out of it. If in doubt I draw the surveyed casting in CAD and superimpose the finished part drawing to work out the best compromise. With my Seagull I decided the carb casting was just too much work to get it to my cosmetic standard. I have made a temporary, even uglier, rectangular carb body from solid, and as I have no CNC, I will eventually either fabricate a gunmetal one, or perhaps even try my hand at gravity diecasting.

Minor porosity is also to be expected. Even high quality castings are often vacuum impregnated as a matter of course. From your pix the blue one looks to be sound.

 

[Cogsy]

Charles has much more experience with this casting so I'd take his advice and all I can give is my impression - The surface finish on the first, except for the defect, looks good, but the blue one looks like something I would cast in my back yard (and then promptly remelt and try again).

 

[Basil]

Thanks for the replies, I am going to work on cleaning up the blue casting and hopefully the porosity is not too deep.

 

[deverett]

I had issues with castings for a Robinson hot air engine from a UK supplier. Blowholes, undersize castings, cylinder base nowhere near perpendicular to the link anchor on the top of the cylinder.
It took 3 replacement flywheels and cylinders to make anything anywhere near acceptable. In the end, I still had to use a fair bit of JB Weld to get an acceptable result.

Dave
The Emerald Isle

 

[vederstein]

The blue castings look about what I do in my garage. But then I'm a hobbyist with a crude set up. (My green sand is play sand, water, and pulverized kitty litter). Here's a picture of my latest. (Poured about two weeks ago). The part is about the size of a small apple.

Based on the experience of my castings, the outside can look rough, but generally porosity is minimal. I believe if I had some other, better sand (e.g. petrobond), there wouldn't be near the flash and the finish would be better.

I would expect a commercial vendor to have quality better than what I can do. But as others have said, sand casting doesn't do small parts well.

...Ved.