How to fixture a stack casting?

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johnpenn74
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How to fixture a stack casting?

Post by johnpenn74 »

How does one fixture a smoke stack to machine it?
John Pennington

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Builder01
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Re: How to fixture a stack casting?

Post by Builder01 »

Here's how I machined my smoke stack and outer steam dome casting. The bottom radius was cut using a boring bar between centers. The outside was done by finishing the inside first. I held the outside by using a split wooden ring to hold it in the 3 jaw. No photo of this. After the inside was done, it could fit on an expanding mandrel to finish the outside. The outside bottom "curvy" part was done with files and emery cloth. The last photo is of both painted. The steam dome outside was finished by pushing it onto a tight fitting wooden mandrel. The outside bottom was finished in the same way as the smokestack. Files, emery cloth and a bit of elbow grease. - David
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KarlKobel
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Re: How to fixture a stack casting?

Post by KarlKobel »

John,

Here are some pictures of how I fixtured my stack for various machining steps.

http://www.karlkobel.com/unsorted/Stack/index.html

Karl
jscarmozza
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Re: How to fixture a stack casting?

Post by jscarmozza »

Great techniques, thanks for sharing your methods.
John
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cbrew
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Re: How to fixture a stack casting?

Post by cbrew »

great ideas, thanks for sharing :)
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Rwilliams
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Re: How to fixture a stack casting?

Post by Rwilliams »

Stack castings are one of the more difficult castings to deal with as there are no flat surfaces to take advantage of during the holding of the stack. Seems like I have done more than a few stack castings in the past and each one presented different problems.

One time the stack was wrapped in some small diameter copper tubing and then chucked in a 4 jaw chuck to make it run true for the machine work. Some areas were cleaned up with files and a stone in the Dremel tool.

Another stack was cleaned up with files and the Dremel tool at both ends and then plugs were installed so it could be set up between centers on a mandrel.

Another stack, a Gene Allen Ten wheeler stack was bored out for a stack extension while clamped to the mill table. The stack was then clamped to the mill table using a table stud down the center of the stack. Then the smokebox radius was cut with a fly cutter on a horizontal mill.

A final sandblast or bead blast job is always nice to help remove any tool marks or file marks and help to blend any small problem areas into a more perfect paint ready surface. Some small problems can almost vanish before your eyes in the bead blast cabinet. Do not be afraid to take your time in the bead blast cabinet to achieve nice results.

My most recent stack job was a vintage Winton Brown 2.5 scale casting in iron. It had some hard spots where the petticoat extension had to attach. Not even carbide tooling would cut through the hard spot. Had to spot grind the problem area after each cut. The parting line was a real mess as the foundry guys had been too aggressive in removing the parting line of the casting. I cleaned up the area as best I could but one side never did offer enough material to clean up to my expectations. It was an easy decision to put the parting line grind issue to the rear of the stack so most photos taken would never show the grinding room flaw. It is for this reason that I always tell my foundry guy to make sure and not get too aggressive when grinding materail from my castings. I will deal with the bit extra material and never go too deep. Some people should never be allowed in the grinding room of a foundry based on all the damage I have seen over the years.

In all cases the final outside shapes were cleaned up with files and plenty of emery cloth. Try to fix the biggest problem areas first and then work towards the smaller areas. Wait a day or two and and review your work to see if the stack still passes the visual test. Looking at a part with compound curves too much at one time can be brain overload. The day or two of visual rest will allow one to see things that may have been overlooked during the first work sessions. A well executed stack is a work of art. Take a look at what others have done or not done to their stacks and learn from their efforts.

Robert
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FLSTEAM
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Re: How to fixture a stack casting?

Post by FLSTEAM »

Here is the setup I used.
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Bill Shields
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Re: How to fixture a stack casting?

Post by Bill Shields »

many ways to skin a cat
stack and petticoat finished.jpg
finished stack in place.jpg
Too many things going on to bother listing them.
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