Author Topic: Need a bearing option...  (Read 2473 times)

Offline SPiN Racing

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Need a bearing option...
« on: July 03, 2011, 11:07:14 PM »
Evening all,

Sooo.. I am working on a project as we all are.

I have a shaft that rides inside a steel housing.

THe shaft has a small groove in it, and the entire thing rides in a bath of oil.

The shaft itself has a bearing surface with a shaft diameter of .71" Its a turned shaft, not ground. Also there are threads outside of the bearing surface, and .71 is the diameter of the threads also. So I cant turn the shaft down to a smaller diameter.

The housing itself is 1.27" OD.

What I need to try to do.. is put a thrust bearing on each end of it. I will turn it down the thickness of the bearing and or bearings and races. AND or bore the inside and put in a bearing Inside the housing.

So my original thoughts were to use a T shaped thrust bearing, that has a thrust surface on top and a needle bearing for the shaft itself. So I am getting thrust and axial loads handled by a single bearing.

However.... I am unable to comeup with any bearings that will fit that size requirement.

Option two I was thinking of... Oilite bearing for side loads. Bore the housing out, and turn down a oversize oilite to fit in the housing, also after boring the oilite to .71. When done slip it into the housing, and the shaft has lateral loads accounted for.

Part two of Oilite, option... to buy thrust bearings, that will be at each end. THe only size I have found are 17mm which is under the .71. Or 3/4 inch, obviously larger.
SO I was thinking.. get the .75 bearing and make a small insert/sleeve to center the bearing.. Or possibly leave a shoulder on the oilite that will center the thrust bearing.

Any ideas?
I have been searching bearing suppliers.. but basically they are 20mm x 35mm. Or 17mm x 30mm.


THanks all..
Scott
SPiN Racing

Offline Lew_Merrick_PE

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Re: Need a bearing option...
« Reply #1 on: July 04, 2011, 11:02:00 AM »
Scott,

What are your loads (radial and axial)?  What is your speed (rpm)?  The ".71" dimension, is that the major diameter of the thread?  If the housing is 1.27 OD, what is the maximum bearing/bushing OD you can live with?  What is the type of oil the shaft is bathed in?

We really need this type of information to do more than wave our hands in the air for you.

One "wave my hands in the air" concept worth thinking about is pinning a threaded on journal to your shaft.  That way you could make a relatively low-friction journal with a flange that would seat your bearing/bushing and accept a snap ring and pre-load spring (I have become a big fan of the Smalley wave springs) if you only need single-direction thrust control.  This is a general concept with NO basis in whatever variables YOU are dealing with on this project.  How straight is your threaded shaft?  How consistent are your threads?

Offline jim

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Re: Need a bearing option...
« Reply #2 on: July 04, 2011, 12:05:05 PM »
if you had to remove a few thou off the thread dia it would have very little effect on the thread strength.
if i'd thought it through, i'd have never tried it

Offline SPiN Racing

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Re: Need a bearing option...
« Reply #3 on: July 04, 2011, 11:54:41 PM »
Well to wave hands in the air and magically dispense more info...

Rotary table, and the threads could be trimmed very very little if at all. The .71 is the od of the shaft, and the threads were cut into the .71 diameter. So to trim threads is not really a option.
Also having any lateral play in the shaft in either direction isnt functional at all. Its a Phase II 6" table.

The table will be run by a stepper motor, and so the speed itself will not be very high, but there will be some load against it.. as I will be doing some milling while its turning.

Scott
SPiN Racing