[kmetzger]

I recently bought the Lee Valley double-ended mandrel http://www.leevalley.com/US/wood/page.aspx?p=32960&cat=1,43072,45939
to set up a slow-speed grinder. It looks like nothing could be easier, but I just can't get it to work. I'm using a 1 hp motor, 1720 rpm. I'd like to post a photo but can't figure out how to resize it to meet site requirements.

The instructions for aligning the mandrel state that "if the drive shaft of the power source turns counter-clockwise, position the RIGHT-hand threaded end of the mandrel on the same end and parallel to the drive shaft." I positioned the right-hand threaded end of the mandrel on the right side because my motor runs counter-clockwise. But after running the motor for a few minutes, the wheel locks up and the mandrel pulley slides to one side even though I tightened the pulley with the set screw. When I switch the mandrel end-to-end I get the same problem, no matter whether I place the wheel on the left hand side or the right hand side.

I'd appreciate any ideas you might have to fix this problem.

Kim

Here are the photos: https://skydrive.live.com/?cid=717E...#cid=717EC8BC45EC3D14&id=717EC8BC45EC3D14!347

 

[Alchymist]

Can't access your pictures - you linked to your account ...needs a password....:no:

 

[kmetzger]

Grinder set-up

Does this work?
http://sdrv.ms/1aduSiF

 

[woodnthings]

you may have 2 problems

If the wheels are rotating correctly that part is done. If not you just mount the motor on the opposite side of the belt OR change the wiring so it rotates opposite.

If the wheels/arbor seizes up, that a BAD thing, and shouldn't be.
There is no reason for that for a new arbor. The pulley must be in the center or within an inch of center. The arbor should spin freely without the belt on. If when it seizes, you can't spin it with the belt on if may be the motor...has seized not the arbor? See if the motor will spin after running for several minutes. Check back in.

 

[kmetzger]

Grinder

The motor works fine. The wheel seizes because the nut gets too tight after running it for a few minutes. I've tried turning the mandrel around and putting the wheel on both ends. Same problem. I think it's the right-hand vs. left-hand thread issue.

 

[firemedic]

Is it "seizing" or is the motor just stopping?


Here's my thoughts.

If the pulley is moving the belt or belt tension is incorrect and they are not aligned.

If the motor is stopping - I'm guessing you are using a "fan motor" like one for ventilations. If they over-spin, which equates to over heating, the internal breaker trips. For ventilation fans the pulleys have to be sized to keep the load within a specific range. ie to much load or too little load causes the breaker to trip.

Have you looked into a variable speed controller? That would allow you to slow it down a bit while also keeping the motor cooler - it's like turning the electricity on and off REALLY fast.

I'm not an electrician, but I have a basic working knowledge of some of it so I'm sure there are others who will explain better and slap my hand.


EDIT

The motor works fine. The wheel seizes because the nut gets too tight after running it for a few minutes. I've tried turning the mandrel around and putting the wheel on both ends. Same problem. I think it's the right-hand vs. left-hand thread issue.

Oh... Well IDK then.

 

[woodnthings]

I checked out mine

The motor runs CCW, and is on the left side of the belt. The left hand thread nut is also on the left side of the belt.

There must be a shoulder on the shaft to which the inside washer rest on. I didn't take mine apart, but I can if you need to know.
Without out a shoulder or if the washer's hole is too large it would seem to want to tighten up as you are experiencing. :blink:

 

[kmetzger]

Grinder

There must be a shoulder on the shaft to which the inside washer rest on.
Without out a shoulder or if the washer's hole is too large it would seem to want to tighten up as you are experiencing. :blink:[/QUOTE]

The inside washer rests against the mandrel bearing block. When I position the mandrel with the right-handed threads on the right, the wheel locks up. When I reverse the position of the mandrel (with left-handed thread on the right) the wheel loosens up and falls off, no matter whether the wheel is on the left or the right of the mandrel.

 

[Dave Paine]

The inside washer rests against the mandrel bearing block. When I position the mandrel with the right-handed threads on the right, the wheel locks up. When I reverse the position of the mandrel (with left-handed thread on the right) the wheel loosens up and falls off, no matter whether the wheel is on the left or the right of the mandrel.

Options to prevent the nut from moving :
a) Use Locktite or a locally available thread locking product. Locktite available in different colours which denote how difficult it is to break the joint. Get the one which needs small amount of heat.
b) Use a nut with a lock collar. Typically a plastic or nylon collar.
c) If you have enough threads, use two nuts and tighten against each other.

 

[kmetzger]

Grinder

Well, it's working fine now. I hope it stays that way. The solution was to place the wheel on the right-hand side of the mandrel with the right-handed thread on the shaft AND to remove the washers and nut from the left-hand side of the mandrel. When I had them screwed on, the wheel locked up.

 

[woodnthings]

bearing block?

There must be a shoulder on the shaft to which the inside washer rest on.
Without out a shoulder or if the washer's hole is too large it would seem to want to tighten up as you are experiencing. :blink:

The inside washer rests against the mandrel bearing block. When I position the mandrel with the right-handed threads on the right, the wheel locks up. When I reverse the position of the mandrel (with left-handed thread on the right) the wheel loosens up and falls off, no matter whether the wheel is on the left or the right of the mandrel.[/QUOTE]

What you should have is a small washer on the shaft OR a protrusion on the larger washer that ONLY rides on the inner bearing race. That way the inner race, arbor and the wheel can rotate independently of the housing. You can not have the wheel or the large washer riding directly on the arbor housing. Here's some photos of what I mean. There must be a gap between the inner washer and the arbor housing, except where the protrusion meets and rides on the inner race:

 

[woodnthings]

more photos

There is a small gap on the right side of the arbor shaft between the washer and arbor housing. This is created by the protrusion of the washer. I believe I made these washers out of aluminum on the metal lathe.

Notice how the large stamped washer tapers down to just ride on the bearing race on the left side of the arbor shaft:

 

[kmetzger]

Grinder set-up

Thank you very much, woodnthings, for taking the trouble to help with this issue. Yes, it's all about the "shoulder." I also wrote Lee Valley for help and they confirmed your theory:

"The theory is when you turn the mandrel in the direction your motor spins, your grinding wheel should tighten up. What it sounds like is that when it tightens up the black backer washer is bottoming out on the pillow block instead of the shoulder of the shaft. There is two collars on the inside of your pillow block and these should be set so that the collar with the backer washer sits proud of the pillow block. You might need to move one of the wood blocks if you have them two far apart and you cannot adjust it as we described."