Replacing the shafts of the idler pulleys
Posted: Sat May 21, 2011 3:37 pm
All,
I got the orders put in to mcmaster and Bart to continue the build. It's been a busy couple weeks with work and my mother in law being in town so I haven't had a lot of time. However, last night I found an hour or so to work and I wanted to give a report on how the shaft replacement went.
On arrival, the shafts did not fit inside the bearings that came with the kit, but I expected that. The shafts did fit very nicely inside the pulleys though (also expected). I could have forced the shafts through the bearings almost by hand. I actually planned on buying a brass spacer with my order at McMaster and using a clamp to press the bearings onto the shafts at the right position. I would actually reccomend this solution because it will help take a little bit of the slop out of the bearings too. Anyhow, I forgot to order that, so I went to plan B. I chucked the shafts into my cordless drill being careful to not tighten the chuck too much. I put the drill in high speed and held a piece of P400 grit sand paper to the shaft. Be careful to move the pinch point between your fingers evenly up and down the shaft and not hold it in one spot too long. This really isn't an ideal solution, but we only need to change the shaft OD by about 3 ten thousandths to make the bearing fit, so we aren't really affecting the accuracy of the shaft by much. It took about 1 minute of sanding or so to make the bearings fit and the shafts still felt and looked polished. I achieved a tight clearance fit. Next, I cut the shaft to length with my dremmel and cleaned up the end. I then positioned the shaft in the right orientation with about 1/8" sticking past the bearing (the opposite side of the bearing to which the pully would be mounted). The fit was tight enough that the shaft would not have moved during operation, but I decided to glue it in place anyhow. I used the trusty super glue to secure the shaft to the bearing. On the end that was left slighly protuding, I carefully used the superglue tip to apply a very narrow bead of glue in the corner where the shaft meets the inner bearing ring. I let the glue set up and afterwards, I could not move the shaft for love or money. After re-mounting the idler assembly in the laser, all of the wobble was gone and the action was clean and smooth like a professionally designed and made machine. The little section of shaft cost me about $0.75 and I think will help with accuracy and also keep wear down. It takes about 20 minutes to do each shaft. This is a solid upgrade for the motion system and I would reccomend it to anybody.
Also, I wanted to mention tha the threads did indeed cut through the tape spacer that I installed earlier so that solution i sno good.
I got the orders put in to mcmaster and Bart to continue the build. It's been a busy couple weeks with work and my mother in law being in town so I haven't had a lot of time. However, last night I found an hour or so to work and I wanted to give a report on how the shaft replacement went.
On arrival, the shafts did not fit inside the bearings that came with the kit, but I expected that. The shafts did fit very nicely inside the pulleys though (also expected). I could have forced the shafts through the bearings almost by hand. I actually planned on buying a brass spacer with my order at McMaster and using a clamp to press the bearings onto the shafts at the right position. I would actually reccomend this solution because it will help take a little bit of the slop out of the bearings too. Anyhow, I forgot to order that, so I went to plan B. I chucked the shafts into my cordless drill being careful to not tighten the chuck too much. I put the drill in high speed and held a piece of P400 grit sand paper to the shaft. Be careful to move the pinch point between your fingers evenly up and down the shaft and not hold it in one spot too long. This really isn't an ideal solution, but we only need to change the shaft OD by about 3 ten thousandths to make the bearing fit, so we aren't really affecting the accuracy of the shaft by much. It took about 1 minute of sanding or so to make the bearings fit and the shafts still felt and looked polished. I achieved a tight clearance fit. Next, I cut the shaft to length with my dremmel and cleaned up the end. I then positioned the shaft in the right orientation with about 1/8" sticking past the bearing (the opposite side of the bearing to which the pully would be mounted). The fit was tight enough that the shaft would not have moved during operation, but I decided to glue it in place anyhow. I used the trusty super glue to secure the shaft to the bearing. On the end that was left slighly protuding, I carefully used the superglue tip to apply a very narrow bead of glue in the corner where the shaft meets the inner bearing ring. I let the glue set up and afterwards, I could not move the shaft for love or money. After re-mounting the idler assembly in the laser, all of the wobble was gone and the action was clean and smooth like a professionally designed and made machine. The little section of shaft cost me about $0.75 and I think will help with accuracy and also keep wear down. It takes about 20 minutes to do each shaft. This is a solid upgrade for the motion system and I would reccomend it to anybody.
Also, I wanted to mention tha the threads did indeed cut through the tape spacer that I installed earlier so that solution i sno good.