Motorized scroll saw repair

[tucsonguy]

My scrollsaw (555252) was a motorized version. It has the same issues as jpgs version - worn bushings and so on - but it had a particularly knotty issue: the pulley on the drive shaft that connected the motor to the first gearshaft was ovalled out, and the shaft itself was badly worn. No amount of playing around could get the pulley straight enough to keep the belt on at anything over a hundred or so rpm.

ShopSmith does not carry a replacement pulley. However, I measured the original pulley and shaft and found fairly close replacements at McMaster-Carr. The pulley is a flat belt toothed pulley that has very close inner dimensions to the original pulley. It is however, not recessed on one side as was the original pulley; and it has a lip around both sides of the pulley; the original had a lip only on one side.

I wanted to keep, if possible the lips on both sides of the pulley, thinking that it would help keep the belt from slipping off.

The shaft was a 6 inch shaft with multiple grooves already cut in it for a circlip.
I went to a machine shop and with the help of a friend, a torch, a very heavy vise, and an air hammer, was able to get the weight off the original shaft. Then I cut the new shaft to the same length, making sure that the outermost groove matched the position of the groove on the original shaft.

The hardest work was altering the pulley. I have a sherline microlathe, and I mounted the pulley on the shaft and put in in the lathe. I proceeded to carve out the interior of the flat side of the pulley to the same depth (a little over 2/10 of an inch). Then I trimmed the outer lip down a little, maybe 1/16 less than the other side.

Then I installed shaft on the weight, added the gear, and slowly assembled the sequence from below - collet (to hold inner bearing in place, originally there was a spacer but there was none on my machine, so I replaced with a collet), pulley, and then slid the shaft through the outer bearing. (I forgot to include the belt on the first time around, so I had to undo and redo the whole process, ha ha) To get the belt on both gears I now had to undo the motor housing and then seat the belt on the motor gear, then slide the motor back in place, stretching the belt as I went, until I could insert the two bolts that hold the motor in place. I think that's why they had the lip only on one side of the pulley, it makes it easier to remove and replace the belt - but I'm happy to have both lips to make it track better.

I had to be careful to make sure that the weights were correctly aligned, with the pointy bits pointing at each other.

Then I tightened everything up, locked the pulley in place with the two set screws, and the collet in place with a single setscrew, and I was done.

It works perfectly! I ran it at all speeds (holding the arm as it cycled up and down) and it ran smoothly and the belt looks like its a perfect fit, no alignment problems.

The remainder of the refurbishment - the shafts and bushings on the arms - will wait until Shopsmith eventually gets around to sending replacements to me (They sell the shafts, but not the bushings, I have ordered ones like jpgs which will require cutting down the flange, which is about 1/16 too thick.)

But if you have a motorized version of this saw, and the motor drive assembly fails on you - it CAN be fixed!

Parts from McMaster Carr:
#1304N12 - L Series timing belt pulley for 1/2 belt
#2025K11 - 1/2 rotary shaft with retaining ring grooves, stainless steel, 6" long
#9414T11 - set screw shaft collar for 1/2 diameter shaft

[tucsonguy]

For some reason I can't add the last two photos, it just gives me an error. Oh well, they showed the pulley collet and shaft in place, as well as a closeup of the pulley showing one lip had been reduced.

[jsburger]

For some reason I can't add the last two photos, it just gives me an error. Oh well, they showed the pulley collet and shaft in place, as well as a closeup of the pulley showing one lip had been reduced.

The error message will tell you what is wrong. There is a 2MB file size limit and for pictures an X x Y pixel size limit. The error message will tell you which one or both you violated.

[tucsonguy]

For some reason I can't add the last two photos, it just gives me an error. Oh well, they showed the pulley collet and shaft in place, as well as a closeup of the pulley showing one lip had been reduced.

The error message will tell you what is wrong. There is a 2MB file size limit and for pictures an X x Y pixel size limit. The error message will tell you which one or both you violated.

It didn't give a file size error but it said the lmits were 0 px x and 0 px y.

[tucsonguy]

For some reason I can't add the last two photos, it just gives me an error. Oh well, they showed the pulley collet and shaft in place, as well as a closeup of the pulley showing one lip had been reduced.

The error message will tell you what is wrong. There is a 2MB file size limit and for pictures an X x Y pixel size limit. The error message will tell you which one or both you violated.

It didn't give a file size error but it said the lmits were 0 px x and 0 px y.

[jsburger]

For some reason I can't add the last two photos, it just gives me an error. Oh well, they showed the pulley collet and shaft in place, as well as a closeup of the pulley showing one lip had been reduced.

The error message will tell you what is wrong. There is a 2MB file size limit and for pictures an X x Y pixel size limit. The error message will tell you which one or both you violated.

It didn't give a file size error but it said the lmits were 0 px x and 0 px y.

This is what the complete error message says.

"The image must be at least 0 pixels wide, 0 pixels high and at most 2050 pixels wide and 1180 pixels high."

Notice the numbers following the words "and at most".

You need an editor to change the the pixel size. I use MS Office picture viewer/editor and change the size to 1024 X 768. That also reduces the file size below 2MB. There are other free programs that will do the same. irfanview is a favorite by some here.

[tucsonguy]

trying to add photos again!

[tucsonguy]

closeup of pulley

[JPG]

That all looks very good!

Thanks for posting!

You are fortunate to have small metal lathe. That should make modifying the bushings a breeze.

[tucsonguy]

That all looks very good!

Thanks for posting!

You are fortunate to have small metal lathe. That should make modifying the bushings a breeze.

Yes, I love it. I've made all kinds of parts for my 1951 MG with it, and now I get to make stuff for the Shopsmith! It's great!