Jigsaw eccentric mounting tubes

peterm · Post by **peterm** » Sun Feb 21, 2010 7:09 am

When I went to mount the jigsaw I recently bought for my Shopsmith Mark V 510, the drive shaft did not line up with the headstock drive by about 1/4 inch horizontally. A look at the owner's manual revealed that I was supposed to use a pair of eccentric mounting tubes.

I tried to get a pair quickly, from various sources here and there and the dealer in Toronto without success and being impatient to get on with using the jigsaw, I decided to make a pair. I bought some 1-1/4" o.d. steel tubing from a local supplier. I had to reduce the tube diameter where it enters the Shopsmith sockets using my Southbend 10k metal lathe. I consulted a retired machinist friend and came away with some good advice on how to go about fabricating it and the result is seen in the attached photos. The end caps are brass. I countersunk the nut into the cap that goes up into the saws base in order not to shorten the engagement much. Cost was $8 for the tubing and I had the rest in my stores (junkpile).

The saw now can be lined up perfectly and runs ok, but the white plastic piece on the scotch yoke in the crankcase (part of item 16 in the parts diagram in the manual) is very tight and makes it difficult to turn the drive shaft by hand. Does anyone know of a source for those?
Peter in Dartmouth NS

dusty · Post by **dusty** » Sun Feb 21, 2010 7:49 am

I know of no source other than Shopsmith to purchase one new. These are sometimes available on eBay.

JPG · Post by **JPG** » Sun Feb 21, 2010 2:02 pm

Are you referring to the plastic piece that rides on the crank pin and connects to the vertical 'shaft'? If so it is 'probably' an out of production part. A call to ss would verify this. Bill Mayo may be of help.

My older manual does not have an item 16. I believe you are referring to the yoke bracket assembly. pn 612300 in my ancient manual.

I am curious why it is 'tight'.

peterm · Post by **peterm** » Sun Feb 21, 2010 2:37 pm

JPG
The plastic piece has two through holes at 90 degrees to each other. One rides in a bar across the yoke and is free moving on my jigsaw, as are the bearings, but the other hole rides on a pin on the crank and grips the pin tightly. I think it might have shrunk during the years since Magna made it. Initally I could barely turn the jigsaw over so I carefully ran a drill bit 2.5 thousands bigger through the hole, which improved it but I think the plastic deformed rather than be drilled out and shrank back some on the pin afterwards. Anyway, the saw can now be rotated by hand with some difficulty, and while the SS drives it ok, it seems to me it should be free turning. The plastic is quite thin and I am reluctant to try a bigger drill.
Peter in Dartmouth NS

JPG · Post by **JPG** » Sun Feb 21, 2010 2:47 pm

prmindartmouth wrote:The plastic piece has two through holes at 90 degrees to each other. One rides in a bar across the yoke and is free moving on my jigsaw, as are the bearings, but the other hole rides on a pin on the crank and grips the pin tightly. I think it might have shrunk during the years since Magna made it. Initally I could barely turn the jigsaw over so I carefully ran a drill bit 2.5 thousands bigger through the hole, which improved it but I think the plastic deformed rather than be drilled out and shrank back some on the pin afterwards. Anyway, the saw can now be rotated by hand with some difficulty, and while the SS drives it ok, it seems to me it should be free turning. The plastic is quite thin and I am reluctant to try a bigger drill.

If you can see some 'out of round' protrusions, a tube of sandpaper(roll one from a flat sheet) may burnish them away! Worth a try, since very little material will be removed. It is probably nylon(or similar0 and will not grind away very fast. A sharp reamer may be useful(drills do not make round holes)! Wrapping the sandpaper around a smaller bit(single layer)(use it like a hand file) may help insure a rounder hole.

I agree it should not bind, but you do not want slop either!!!

peterm · Post by **peterm** » Sun Feb 21, 2010 4:30 pm

JPG
Thanks for the sandpaper idea. I can't see any protrusions but will try the sandpaper.
Peter in Dartmouth NS

billmayo · Post by **billmayo** » Mon Feb 22, 2010 2:01 am

prmindartmouth wrote:JPG
The plastic piece has two through holes at 90 degrees to each other. One rides in a bar across the yoke and is free moving on my jigsaw, as are the bearings, but the other hole rides on a pin on the crank and grips the pin tightly. I think it might have shrunk during the years since Magna made it. Initally I could barely turn the jigsaw over so I carefully ran a drill bit 2.5 thousands bigger through the hole, which improved it but I think the plastic deformed rather than be drilled out and shrank back some on the pin afterwards. Anyway, the saw can now be rotated by hand with some difficulty, and while the SS drives it ok, it seems to me it should be free turning. The plastic is quite thin and I am reluctant to try a bigger drill.
Peter in Dartmouth NS

The plastic like piece gets deformed from a lack of oil. I just obtained a Mulit-Craft (clone) machine with a jigsaw. The plastic like part was replaced with a nice square piece of brass that looks like it would be easy to reproduce.

Shopsmith still lists this item as a replacement part: 502275 Yoke Bracket Assembly $27.73. Contact me by Email.