Bearing Replacement MArk V

[derekdarling]

Hi all...

I have a Mark V that I am refurbishing. The thing would turn on and start running, then blow a breaker. I isolated the problem to one or both bearings in the upper housing. I pulled the drive shaft (the one the poly-v belt goes around), and found that both bearings were grinding a little. I bought new bearings, the proper size, and found that they don't easily go in the hole, certainly not as easily as the ones on the ShopSmith videos.

So, the question is... is there an easy way (and accurate) to enlarge the hole so that the bearings fit without sledgehammer persuasion? I have always thought that bearings shouldn't be that hard to seat, unless it is on a car wheel!

I thought of putting the drive shaft and bearings in the freezer, then heating the head casting in the oven in an attempt to enlarge one and shrink the other. Any insight would be gratefully appreciated.

Thanks to all.

Derek Darling
Surrey, B.C.

[nuhobby]

Temperature offset is a real friend, especially the chilling of the bearing assembly.

Clean, wax and buff the headstock casting bores if not already done.

Have a Quill in place when you push in the Drive Sleeve, to help it be driven perfectly on-axis.

A "pusher" with the right dimensions for your bearings is very helpful, such as I've made here:
[ATTACH]9578[/ATTACH]

[dusty]

Hi all...

I have a Mark V that I am refurbishing. The thing would turn on and start running, then blow a breaker. I isolated the problem to one or both bearings in the upper housing. I pulled the drive shaft (the one the poly-v belt goes around), and found that both bearings were grinding a little. I bought new bearings, the proper size, and found that they don't easily go in the hole, certainly not as easily as the ones on the ShopSmith videos.

So, the question is... is there an easy way (and accurate) to enlarge the hole so that the bearings fit without sledgehammer persuasion? I have always thought that bearings shouldn't be that hard to seat, unless it is on a car wheel!

I thought of putting the drive shaft and bearings in the freezer, then heating the head casting in the oven in an attempt to enlarge one and shrink the other. Any insight would be gratefully appreciated.

Thanks to all.

Derek Darling
Surrey, B.C.

I am not going to be much help because mine came out a little hard but the new ones went in with no real problem.

I absolutely would not advise that you do anything to enlarge the hole where the bearings seat. I would not do anything to that opening other than to clean it good.

There are others who will chime in here will advise based on experience greater than my one machine.

[skou]

I absolutely would not advise that you do anything to enlarge the hole where the bearings seat. I would not do anything to that opening other than to clean it good.

Dusty, his temp offset is a temporary procedure. Once the parts reach a common temp, they go back to normal. As an aside, heating/freezing stuff is very common in aircraft construction. When I worked for McDonnell-Douglas, we'd use this very method to affect repairs. Since we had a dry ice bin in the hangar, we'd mostly just freeze stuff, and keep the main structure at ambient. If you freeze a plug at -100F or so, then just push it in the hole, when it thaws out, you can't move it.

Oh, a long time ago, I worked at a VW head rebuilding plant. We did nothing but bug heads. Almost every one had thrown the valve seats. We'd machine a new seat pocket, wrap the seat in an aluminum sleeve, cold-soak them on dry ice, and pop them in. All we used was a fixture to align the seat to the valve guide,and tap them in with a hammer. No glue, no welding, just a temp-offset press fit.

steve

[dusty]

Steve; I guess I really misinterpreted some comments. Enlarging the race way by cold soaking was not what I was warning against. When I read derekdarling's post I thought he was thinking about reaming out the hole to fit the bearing.

My error. I should have read more closely.

[skou]

[quote="dusty"]Steve]

No problem, Dusty. Myself, I've NEVER read anything wrong. (If you believe that, I've got some good cheap swampland up here in Mesa!):D Oh, it's 95 degrees INSIDE my house right now. All I've got is a swamp cooler, and the humidity is kickin' it's posterior.

steve

[dusty]

No problem, Dusty. Myself, I've NEVER read anything wrong. (If you believe that, I've got some good cheap swampland up here in Mesa!):D Oh, it's 95 degrees INSIDE my house right now. All I've got is a swamp cooler, and the humidity is kickin' it's posterior.

steve

Wow, another forum member here in Arizona. We are growing in number. Soon there will be enough of us that we could have an Arizona Sawdust Festival.

Please consider filling out at least part of your personal profile so that we know Who's Who are where they are located.

[JPG]

Hi all...

I have a Mark V that I am refurbishing. The thing would turn on and start running, then blow a breaker. I isolated the problem to one or both bearings in the upper housing. I pulled the drive shaft (the one the poly-v belt goes around), and found that both bearings were grinding a little. I bought new bearings, the proper size, and found that they don't easily go in the hole, certainly not as easily as the ones on the ShopSmith videos.

So, the question is... is there an easy way (and accurate) to enlarge the hole so that the bearings fit without sledgehammer persuasion? I have always thought that bearings shouldn't be that hard to seat, unless it is on a car wheel!

I thought of putting the drive shaft and bearings in the freezer, then heating the head casting in the oven in an attempt to enlarge one and shrink the other. Any insight would be gratefully appreciated.

Thanks to all.

Derek Darling
Surrey, B.C.

Are you absolutely sure the size is correct? Did the headstock bore get scored during removal? How did you remove/install the new bearings on the shaft?

Looking for 'clues'!:)