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macona
11-17-2007, 03:36 AM
I am working on a casting kit of a Fairbanks Morse 25 HP 1/6 scale engine by Tom Stuart. Good quality castings. Real nice cast iron.

For some of the parts though like the head the cast surface is removed to make the surface and does not match the res of the engine.

Any ideas on how to make machines surfaces look cast? I was thinking using a needle scaler over the surface. It gives a pretty random dimpled surface.

Get the parts to rust? Or etch them somehow?

Anyone?

oil mac
11-17-2007, 05:18 AM
Hi Macona,
Sounds really nice project, Might be possible to mask over the machined fitting surfaces, spark plug holes or whatever, by gluing on rubber or plastic, machined nylon or anything suitable to protect, and have the"cast looking surfaces " lightly sandblasted

Bguns
11-17-2007, 05:20 AM
Coarse sandblasting media should do it, mask off critical surfaces and have sandblasted. Will be ready for primer right after blasting .....

Darn fast typers beat me by seconds... :)

Ian B
11-17-2007, 07:45 AM
First thing to do is get rid of any sharp corners resulting from the machining process; castings tend to have rounded internal and external radii. File for the external, filler for the internal.

Also, castings often have a draft or taper to allow the patterns to be removed from the sand moulds. If you can imagine how the original would have been cast, can you recreate the taper of the draft by machining? 2 or 3 degrees should be enough.

Then paint it...

hth,

Ian

wierdscience
11-17-2007, 08:15 AM
Assuming you intend to paint,some fine blasting media dusted on while the first coat is tacky and then painted over with two more coats will simulate a cast surface.Try it out with different size grits on a some scrap first to get the scale right.

Your Old Dog
11-17-2007, 08:41 AM
Assuming you intend to paint,some fine blasting media dusted on while the first coat is tacky and then painted over with two more coats will simulate a cast surface.Try it out with different size grits on a some scrap first to get the scale right.

If cornmeal would work you could resize it smaller between two steel plates like a bench top grist mill :D Idea might not be so odd !!

wierdscience
11-17-2007, 08:46 AM
If cornmeal would work you could resize it smaller between two steel plates like a bench top grist mill :D Idea might not be so odd !!

That's a good idea,an if you wanted to simulate Chinese cast you just dip the part in an egg and milk mixture,then the cornmeal and deep fry:D

Bill Pace
11-17-2007, 09:27 AM
I like the sandblasting idea --- think I would try some sand in as big a grit as the gun would handle and play with distance from part, lower pressure, etc.

If no access to blasting, I like Weirds idea----in fact, ---that would be a lot simpler/easier than fooling with media changeout. (IF...youre gonna paint, that is)

Carld
11-17-2007, 09:50 AM
How about using a 4" disc grinder to rough the surface and break the square corners then using the needle slag remover to indent the surface. The combination of the two should give a texture like cast in sand.

oil mac
11-17-2007, 03:50 PM
Carld Has a point In todays"Wonderful World"__ When i see what todays workers do to reasonable castings with angle grinders and other similar instruments used in the late 20th. & start of the 21st. centuries, and these along with the far east crap, Which is past on to what remains of a great Western worlds manufacturing culture, No wonder factories are vanishing at a high rate of knots. This combined with some of the recent"developments" In the name of Casting manufacturing progress, And the results of such held up as good casting finish and dimensional accuracy, I wonder where craftsmanship & pride has gone.

Forty years or so ago, one could purchase from foundries castings made by old time moulders, using traditional methods who achieved products which were a treat to work with, This was before the growth of experts and four decades of unmitigated greed.

SGW
11-17-2007, 07:15 PM
These aren't surfaces that would have also been machined on the prototype engine?

macona
11-18-2007, 12:08 AM
Actually I was planning on powder coating all the parts. Goes on easy and is tough as nails. I think there may be some powders that do have a texture.

Yeah, the needle scaler is probably my best bet as I dont have a sandblaster.

SGQ. They would have not machined the whole casting. Just areas where they had to.

Another possibility is I might be able to save one surface of the chunk of CI I am machining the head from. That would at least be one less surface to do.

Ill post some pics later of what I have gotten finished. Just bored out the cylinder and honed.

Fasttrack
11-18-2007, 01:02 AM
Assuming you intend to paint,some fine blasting media dusted on while the first coat is tacky and then painted over with two more coats will simulate a cast surface.Try it out with different size grits on a some scrap first to get the scale right.


Every year i put together a little haunted forest/house for my sister's halloween party and all of the tombstones i use are actually made out of plywood but to get the old stone surface i sprinkle sand on the first coat of gray latex paint and then spray over with another coat of gray paint.

Actually what i have been using recently is a mixture of non-water based adhesive and kitty-litter. Water based glues obviously dont work worth a darn, but fast drying spray type adhesives, like 3M contact cement work well and the kitty litter provides the gray color - plus its not a uniform gray that way. Much more realistic... :)