Sunday, January 20, 2013

Cast Iron Rotisserie Repair

My neighbor brought over a fancy antique cast iron nail dispenser the other day. This is the guy that travels to France a couple of times a year and comes back with a container full of eclectic and mostly broken items. This particular piece got dropped or damaged in shipment and snapped off part of the casting. Fortunately for my neighbor he lives across the street from a machine and welding shop. This is where I come in.
Here is the dispenser as he brought it over. You can see the pedestal is snapped off and whatever was sticking up is missing. A new one needs to be created.
Classic cast iron fracture. There was a tiny radius at the root of the shaft but the fracture started on a score line from machining. The boss was cast into the base so I don't really know how much material I have to work with through the stem.
The first minor challenge was determining what the thread in the top finial was. Automatically I assumed it would be metric because of the country of origin. After fussing around for a while it turns out the closest match was 5/8-18. This is pretty close to M16 x 1.5 so I really looked at it closely. The bore on the compartmented casting would not accept 16mm so it was confusing for a minute. The thread was also pretty chewy looking down the bore. My 18 TPI thread gage fit better than the 1.5mm so 5/8-18 it is.
The casting is pretty interesting. I will give my neighbor credit he has a pretty good eye. Not something I would buy but I can appreciate the workmanship.
Nothing ever goes as smoothly as you see it in your mind. The four jaw will not close done far enough to hold a 5/8 diameter so I decided to remove the four jaw chuck and put the 5C collet closer on the machine. One bonus was at least I had a 5/8 collet on hand this time. The chuck removal took longer than it normally would. I decided to make a spud to clamp in the chuck jaws to help with removal. At the same time I also needed to put some decent index marks on the camlock locking screws. For some reason the spindle nose didn't have any index marks from the factory. After the chuck removal delay I cut the thread on the finial end of the new shaft using the finial itself as my thread gage. This is the first time I have threaded with the new lathe and I'm happy to report it works great. Some lathes have a little trouble when you engage the half nuts but the Yam seems to slide right into the leadscrew without any bumps or jams.
Before I did any threading on the opposite end of the replacement shaft I wanted to see what thickness was I would have to work with. The base casting is fairly light so I was worried that the thickness through the neck was marginal. This is a perfect job for the mini strap clamps and base plate.
I really wanted to avoid putting any clamping pressure on the casting across the diameter. Holding it down was the only real option. The little 10-32 strap clamps can put serious pressure if needed. I indicated the OD of the neck instead of the broken spud. There was a slight visual mismatch between the broken spud and the OD. Because I wanted the two diameters to be concentric I indexed on the OD.
Fist step was to flatten the broken area so I could  get a drill started. I poked through with a small drill to see what the thickness was. It looked like I would have enough for a decent sized stud to attach the new shaft.
I was able to get a 3/8-16 through the neck with plenty of meat. Instead of single pointing the 3/8-16 I just tapped the new spud shaft the same and bottomed a nice strong set screw in the new shaft.
The set screw is 150kpsi strength and I get good full threads all the way up to the shoulder.
The new spud shaft. This is one French antique that has been thoroughly Americanized. Time to assemble the dispenser.
I left it in the machine to tighten the spud shaft into the base. I used my copper jawed vise grips to secure it.
These are one of the best homemade tools I have made. The copper jaws are silver brazed onto the smoothed down stock vise grip jaws. This is the second set I have made because they get so much use. It grips the shaft better than a strap wrench and leaves no chowder marks.
Final tightening of the finial. No tools just hand tight with the secret gloves.
Done. I imagine some wealthy yuppy will have this in the hallway filled with keys or candies. It would also make a nice paper clip and thumbtack holder. I know, it would be an awesome baked potato prep station. You could have all the condiments in the pockets, sour cream, bacon bits, green onions and the potato being prepared in the finial cup.

A fun little Sunday afternoon repair job. Thanks for looking.

2 comments:

  1. I found this site a few months back and I try to check in once a week or so just to see what you are doing for the next project. I have to say you get into quite a range of projects. I want to make one of those mini-tables with the small hold down clamps. That looks like a tool that would get used often.
    Mike

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  2. Hi Mike,

    You should make one of the mini tables. Once you have it I'm sure you will find many uses for it. Thanks for posting.

    Tom

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