Monday, August 12, 2013

Bench Grinder Fan Repair

I bought a bench grinder from a garage sale for a low price, but like they say, the cheapest things cost you the most.  I tried it before buying it and the shaft would slide back and forth by at least 1/8" which is a major inconvenience when trying to grind something.  I took it apart and the problem was really obvious.  There had been a plastic fan on the shaft, and its hub was also a spacer to prevent the shaft from sliding.  The fan was split in two pieces just sitting in the grinder housing.  It seemed like too much to ask for a plastic part to do both of these functions anyways, but this is a cheap grinder.

The snap ring to the right of the bearing prevents the shaft from sliding left, but once the fan was gone (and the missing snap ring), nothing was stopping it from sliding to the right.
I could've just made a collar to go on the shaft to take up the space where the fan was, but then there would be no fan.  I decided to make a fan to avoid overheating risk.  I drilled a 1/2" hole in some aluminum sheet and cut the circle out with aviation snips.
When cutting the fan blades and twisting them, I accidentally broke one of them off.  Since the balance of this fan isn't nearly as critical as my foundry blower, I figured no damage would be done.  I then rubbed both sides on sandpaper to make the thickness consistent.
In order for the new hub to fit, I had to sand and file off the serrations that the old plastic fan was being held on by.
Fan location
The hub was turned from 9/16" aluminum.  I had to do some math to ensure the fan would be placed in relation to the grinder housing correctly.
Here the 1/2"-20 threads are cut to secure the fan on. Afterwards, a 3/8" hole was drilled through and the hub was parted off.  Then, I drilled and tapped a #10-32 hole for a set screw.
As planned, it fit in the grinder perfectly, all it took was a little bit of bending to get the fan to run relatively true.  Since I didn't do that good of a job removing the serrations from the shaft, it took some force to get it to fit on.  With that in addition to the set screw, I may not even need to replace the missing snap ring.  The 1/2" nut I used was actually a bit cut off a plastic heim rod end, I made sure to add thread lock to it so the vibration doesn't make it come loose.

1 comment:

  1. Since I didn't do that good of a job removing the serrations from the shaft, it took some force to get it to fit on.


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