Are mower spindles hard?

Ron W · Apr 30, 2020

I have a really nice Continental-Belton mower that works great on my to-20 or 8n. The problem is that I have had it for 20 years (used) and the spindles were bad then and have gotten worse. So I am making new ones out of 4140 steel.

The question I have is that do they harden mower spindles? The 4140 is about 25 Rc, and max is 54 Rc. I was thinking of getting them 40-45 so that they are tough but not too brittle.

File hard I thought was 60 Rc.

They are about 1inch diameter swinging 21inch blades. The mower is 3 blades 60inch.

Butch(OH) · Apr 30, 2020

4140 as machined is better than any spindle I have worked in. I suspect that most of them are nothing but 1018 or a leaded version of it. I made a few that were not available from stressproof because I had it in the shop and they are working fine.

Mike(NEOhio) · Apr 30, 2020

4140 is fine without heat treating. Don't over-think it.

T.R.K. · Apr 30, 2020

I work in a mower shop. I recycle mower spindles into other useful things on my metal lathe. Most spindles are not hard. The only exception I can think of is Kubota zero turns. Those are case hardened. It was all I could do cut that one with carbide cutters. No other spindles I know of are hard or even case-hardened like the Kubota because they would rather the shaft bend than break if it hits something.

Case hardening only hardens the outer 1/32 or so of the steel, so it won't wear as fast.

Janicholson · Apr 30, 2020

Stress Proof being AISI 1144 (kind of a old name for it) but even normalized it would be tough. Jim

Are mower spindles hard?

Ron W

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Butch(OH)

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Mike(NEOhio)

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T.R.K.

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Janicholson

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