Hardened ground brass washer in place of a thrust bearing?

[drozovs]

Does anyone know what the tradeoffs are (beside cost) between using a hardened ground brass washer (low cost) vs. a thrust bearing (high-cost) for a low-speed application? Im working on my dissertation and the cost delta is $2,450 for four bearings vs. 4 washers. Thanks!

 

[MikeHalloran]

Perhaps you skipped the metallurgy elective.

Steel can be hardened and ground, if it has enough carbon.
Low-carbon steel can be carburized, hardened and ground.

Brass is a generic term for literally thousands of copper-zince alloys (browse copper.org), which have varying degrees of hardness as supplied, but cannot be 'hardened' in the same sense that steel can, nor to the same degree.

I'm pretty sure that brass can be ground, but it's got to be as difficult as grinding aluminum, what with clogging the abrasive and all. Diamond machining can give a better finish anyway, and cutting with a good steel tool can do pretty well.

You haven't given enough detail to actually get close to the proper set of tradeoffs to be considered >for your specific problem<, but I'm guessing you're looking at a fairly large load if four thrust bearings cost more than two large, so plain bearings may be entirely inappropriate anyway.

To be of any help, we'd need to know at least the speed ('low' is not a number, and means different things to different people), the load to be transmitted, how many rotations the bearing need to survive, what constitutes failure (yield, fracture, or deflection limit for starters), and what sort of environment surrounds the bearing.

If some local expert told you to consider 'hardened and ground brass', you need to find a different expert.







Mike Halloran
Pembroke Pines, FL, USA

 

[diskullman]

BRONZE thrust washers are quite common. Don't be fooled by the similar colors.

Russell Giuliano

 

[drozovs]

Sorry, This was the psychologist major in me writing the first post. It was bronze, not brass and the low rev was < 120 rpm. The max load was 2.2 lbs per foot torque.

The company we are going to use sells 1 bearing at $550 or or 10 at $650 so I and since I need 8 at least I am just gonna buy 10.

My main concern was that the bronze thrust washer would change the "feel" of the rod rotating.

 

[imcjoek]

Selling thrust washers on a scale to handle 2 lbs for $550+?

I am in the wrong business.



I still don't get what you are tying to do. 2.2lbs per foot torque? Please translate that into something that makes sense. Do you mean 2.2lbs*ft. That is a torque, yes. But A torque does not help you to size for a *thrust* load.

 

[drozovs]

sorry, the thrust washers cost 5 dollars, the bearings cost $550 if you buy one, $50 if you buy in bulk but the minimum order is 30,000 units. So since I only need 10 I am going to machine them with out the groove. I figure it will be smoother then a bronze thrust washer and at 2 lbs wear should not be a huge issue. Sorry about the confusion on all of this.

 

[MikeHalloran]

Uh, 30,000 is a distributor lot.

Are you aware that there are people who buy truckloads of bearings on speculation, and have them available on a shelf when you need them on short notice in small quantities? They usually choose a business name with 'bearings' in it, and advertise that big yellow book you should find near the telephone. Look under 'bearings'.







Mike Halloran
Pembroke Pines, FL, USA

 

[drozovs]

Mike,

We only were able to find one company after days of searching who carried the bearing we needed. When I wrote them for the lead time they stated I needed to purchase that quantity even though they sell them in single units. The specs were:

Rotating Bore (d1) (mm): 10.000
OD (D1) (mm): 15.300
Thickness (T) (mm): 6.500

We have not been successful finding one with an OD of the same size.

 

[MikeHalloran]

Have you got room for a larger diameter bearing that's just a whisker thicker?

http://www.mcmaster.com/#6655k55/=4t06p7

Mike Halloran
Pembroke Pines, FL, USA

 

[drozovs]

The thickness isnt problematic but the OD is. The only one we can accommodate is 15.3 or smaller. Maybe a smidge larger. Ill take recommendations if anyone has them though

Best,

David

 

[unclesyd]

For light loads and low speeds either of these materials should do the job. I would query both Metcar and Graphalloy about your requirements,

http://www.metcar.com/standardproducts.htm

http://www.graphalloy.com/html/bushlist.htm

Last but not least is ToughMet from Brush Wellman

http://www.brushwellman.com/Alloy.aspx?id=278&id2=1352