Appropriate steel for a spacer?

[Siggi]

Hey y'all,

I'm restoring an old 14" Rockwell/Delta metal/wood cutting bandsaw, which has a crack in the casting. After some consideration, I've figured that the safe thing to do is to machine a new spacer for the one I believe is short to protect the casting from getting crushed (again) when the wheel is tightened up.
I have a PM1236 lathe in my basement, but I'm a rank beginner, and so I'm pondering this very basic question of what sort of stock would be (most) appropriate for the application. This spacer rests against two inner bearing races and rolls with the shaft. The cavity in the casting has oil in it, that'll splash around when the big gear wheel spins.
So, can y'all elucidate me as to the whats and the whys?

Siggi

 

[dlane]

A pic would help, of casting crack and where spacer will go, also the saw.

 

[Siggi]

A pic would help, of casting crack and where spacer will go, also the saw.

The original thread has a picture of the crack, which I've now sealed with JB weld to prevent oil leaking out at least. Here's the shaft with the full stack-up on it, the existing spacer is poking out of the end by the gear wheel.

I believe the casting cracked because the spacer is about 65 thou short, and so when the wheel is tightened up with the nut that goes on the left side of the shaft, the shaft ends up pulling on the casting from the snap ring on the right-hand bearing. When I dry assemble this, I get about 65 thou axial play on the big gear wheel, and at one end of travel it'll rub against the casting.

Here's a couple of pictures of the spacer.

I essentially need to reproduce this piece about 65 thou wider.

 

[Nogoingback]

What's the old spacer made from? If it's steel, I imagine anything would work: 1018, 1144, whatever. If the spacer just locates the inner
races of the bearing relative to one another, I doubt Rockwell used anything exotic.

EDIT: I was typing while you were posting your pics. It looks as though your spacer has a shoulder, or am I seeing it wrong? Is the spacer
located between the two bearings? It's not completely clear how the assembly goes together. But, again, if the spacer is simply located
between the bearings and rotates with the inner races on the shaft, the material probably isn't critical. Or, is there more going on here?

While taking up some play in the shaft may be needed, it may not be a good idea to spacer it to the full distance of .065" . Most assemblies
require some end play to allow for expansion due to temperature change during operation.

 

[markba633csi]

Hi Siggi I feel your pain, JB weld is a good remedy for the moment until you are able to have the crack veed out and brazed for
a more permanent repair
For a spacer any mild steel would be fine- even aluminum would work also I think
Mark

 

[francist]

Wonder if you could just make a washer of the appropriate thickness to use along with the existing spacer? Might be less effort and you could try one or two different thicknesses if you were uncertain about the take up distance required.

-frank

 

[f350ca]

If you can find heavy wall pipe or DOM tubing it saves having to remove as much metal from the center.

Greg

 

[mikey]

I would use 12L14 - cheap, easy to work, more than strong enough for the application, bathed in oil so rust is not an issue.

 

[pacifica]

I also would use 12L14 or 1215, free machining and great for a beginer since it cuts like butter but still is strong, especially compared to 6061 aluminum.You can find both at MSC. Look for free shipping since metals are expensive to ship.

 

[Ray C]

In all honesty, I cannot visualize how that part fits (or mis-fits, as the case may be) to cause the housing to crack as shown in the pictures related to this thread.

The big gear has helical teeth and such a gear will always place an axial thrust on the shaft it spins on. Are you absolutely certain that the cracked housing is because of the deformed or altered spacer you intend to make? Is it possible the axial forces are excessive for some reason? Are you certain this was assembled properly? Maybe something is in there backward...

My thought is to proceed cautiously until you absolutely understand the failure mechanism.

If you proceed on making that part, since you probably cannot measure precisely how big you want it to be, I'd recommend making it more than 65 thou bigger. This way, you can trim it down if necessary.

Ray