Where do I download a free manual for my 16 inch craftsman variable speed scroll saw?

I never tried changing motor but have you contacted a Technical Rep already? or looked on the manual?

Try this link. The part has been substituted.
http://www.searspartsdirect.com/partsdirect/part-model/Craftsman-Parts/Saw-Parts/Model-113235501/0247/0744440?blt=05

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Manufacturer authorized substitution: 22256 may differ in appearance, but is a functional equivalent to prior parts including 9-22256.

I have one. E-mail [email protected] and I will copy and send one, no charge.

The tube can be replaced with the plastic tubing used for aquarium air pumps that you can find in most pet stores. Unfortunately you have to disassemble the scroll saw arm to replace it. Remove the 6 screws at the back of the arm assembly, then the 4 bolts that hold the arm to the base. This will allow you to split the arm and you will find a plastic bellows that the hose connects to.

Try retightening the tension knob...not sure exactly hows its hooked on,but sounds like you may have backed it out too far.If simply turning the knob to tighten does'nt work,try either pulling up on knob a little while trying to tighten..or opposite-push down on it while trying to tighten...the idea with both is to get the threads on the tightening knob to catch the nut inside...my guess is it came off.

here's the link for the manual:
http://www.hammerwall.com/Download_Manual/17858/

Unfortunately it looks like you'll have to order it from Sears. And I don't know what the difference is between the 2 listed.

They are at the very bottom of this page.

http://www.searspartsdirect.com/partsdirect/getSubComp.pd?modelNumber=137286050&productCategoryId=0744440&brandId=0247&modelName=SCROLL-SAW&diagramPageId=00001&documentId=P9020197&pop=flush

It would have cost more to have Sears fix the saw than I paid for it, so I got my meter out and by checking the voltage drops across all of the electrical connections in the saw , I determined that the on / off switch was defective. This switch is the same switch used to turn the lite on and off, so I took the switch out of the lite and used it in the saw. I ordered a new switch for the lite and will install it when the new one comes. Thanks for your interest and help. fletcher1

Go to www.searspartsdirect.com and search by model number.