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Where to buy shaft key stock, and what to buy?


BakingDude

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BakingDude

I have a Landlord System 7010, and way back (it feels like it) in 2008 the kind people here helped me through rebuilding the 3-speed transmission and the BGB.  I use it for mowing and plowing, and it is has been a workhorse.  Having put the effort into rebuilding, I am aware of the wear points such as the axle tubes and various keys and keyways.  I had a donor transmission, and was able to save only a few leftover parts from it - one is a key that is about 3-3/8" long, and does have wear.

My property is quite sloped, and wooded, and was formerly a pasture.  So there are roots and other things I have hit over the the years with the mower.  I am actually on my second deck in 22 years.  I have worn out a few center arbor shafts, which is my current replacement project.  This style has one woodruff key for the spindle pulley, and one square key for the drive hub.   Years ago, I bought 1/8" square stock from a small independent old time hardware store, hoping I was getting quality.  Unfortunately, I did not know what I was buying.  It is possible I bought "undersized" stock (as it is slightly smaller than the stock keys), and it has a shiny appearance and appears softer and less dense than the stock material.  As a result, I believe I have had premature wear of the arbor (and of course the key).  I will not represent that I have hit no branches or roots - this is a rough service environment, though I try not to abuse it.

I was tempted the last time I did this same service to use the worn key from the donor transmission, which is perfect on the two faces perpendicular to the wear faces, to make the square key.  Both have been NLA for a long time.  I can't imagine ever tearing apart my transmission, like I did previously.  So I am between using the worn transmission key, which would likely be an excellent donor for stock, or sourcing new material.  After my experience buying stock the first time, I would need advice what and where to go for stock.  I see that Grainger has Low, Medium and High carbon steel stock, and stainless.  I am assuming I want one of the carbon steel variety, but which?  They carry undersized, oversized and bilateral tolerance key stock.  Which of these would I want for new shafts, pulleys, etc?

If I can source material similar to that used in the OEM keys, I would have no problem using the key from the donor transmission now which I am confident will be suitable, and in the unlikely event I ever service the transmission, I could get new stock for that.  But if someone could give some advice on what kind of material I should be seeking, and where I might get it, I would be greatly appreciative.

Don

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steve-wis

Hi,

Key stock is made to be a bit softer, you want the wear to be on the key and not in the keyway of the shaft or pulley.  There are two types of actual key stock that I am aware of.  Either cold finished or zinc plated.  We always used either cold finished in standard size, or zinc plated in oversized.  The plated keystock can be easily filed to fit tightly into your keyway, it takes a bit of time but you are assured of a tight fit that way.  With standard you take your chances on fit depending on what kind of wear you have in the keyway.  You should NEVER put hard stock in for a key unless it is specifically called for, you will destroy the shaft or whatever you are keying to the shaft that way.

McMaster-Carr

Steve

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I agree with Steve, but would add the only place I have seen hard keys used on a regular basis is hydraulic motors (usually come with new motor). 

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steve-wis

I worked for alot of years in a job shop where we made parts for various manufacturers of different products.  We made hard keys for a couple of them for very specific applications, usually where a very high degree of accuracy of fit had to be maintained, usually when a keyway was used in the design of gages, or fixtures.  Also, there are some hard keys in paper machines.  I don't know if I have ever seen hard keys anywhere else.  I do know that aluminum keys are used in alot of flywheel applications so that the key will shear before damage is done to the crankshaft keyway.  also, the key on a flywheel is used only for alignment at assembly, the taper is what holds it in place.

Steve

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3 hours ago, steve-wis said:

... the key on a flywheel is used only for alignment at assembly, the taper is what holds it in place.

An interesting note.  I have found the Kohler/Briggs cast iron engines have flywheels that are VERY tight on the crankshaft and are difficult to pull.  The Kohler Command flywheels come off quite easily even though torqued to spec.  Different interference angle I suppose?

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steve-wis

Carl, to be honest I haven't had enough experience with the commands to have noticed, but I would imagine the taper angle, length of engagement, and finish would all affect how tight the flywheel would be on the crank.  Guess I will have to pay attention next time I do a command.  I do know that on the older briggs it can be quite a chore if you don't have a good puller, and sometimes even with one to get the flywheel off.  I can say that I worked on a guys toro push mower a while back, and the key was shot.  I bought a new one and their keys are aluminum, and also are offset about half the width to give a smaller cross section of material that needs to shear.

Steve

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BakingDude

I appreciate all the replies.  I believe now the main issue I had was the arbor I installed the new key into a few years ago had a worn keyway.  It was not new.  so the fit was very slightly loose from the start.  There are references to "hard" material above, which I am guessing is high carbon content.

Perhaps I have zinc plated here - the shiny stock I bought and still have a piece of.  I received a brand new B&S arbor today, and it has what appears to be a thick black paint on it.  So I can't tell yet how this will go once that coating is removed during installation.  I will try that first, and keep the transmission key as backup.

 

Don

Edited by BakingDude
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steve-wis

Higher carbon doesn't necessarily mean harder.  Steel carbon content does determine how hard it can be heat treated to, with higher carbon being able to be hardened to a harder state.  Higher carbon does make the steel a bit stronger, if that makes sense.  Also, different alloys in the steel will make it either harder or stronger depending on the alloy.  Alloys such as nickel, chrome, etc change the structure of the steel.  Usually keys are made from 1018 cold rolled steel.  The 10 indicates a plain steel without alot of alloys, and the 18 means it has .18% carbon content.  A 1045 steel is the same but can be heat treated to a higher hardness because it has .45% carbon.  

Hope this gives you an idea of different steels and their uses.  Here is more info if you like.

The Effects of Common Alloying Elements (wieland-diversified.com)

Steve

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BakingDude

I am too distracted here.  First, the keyway is 3/16", not 1/8".  I have a caliper (which I had not thought to use), and the OEM key from the transmission measures 1/1000 over 3/16", and the hardware store stock measures 3/16" to the thousandth.  I don't know what is considered "oversized" (1/1000 or more than that), but my temptation is to use the OEM stock if I can get it into the keyway.  Should be able to with patience.

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BakingDude

After making a new key, I found that the new B&S shaft when unboxed came with the NLA straight key.  Doh!  All that fuss for nothing.  Sorry to bother people for nothing.  I have a new issue which I created a new post for.  Always something.

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In the past, when I needed to repair a key and shaft, I have done something that has worked quite well.  I have rotated the shaft 180 degrees and cut in a new keyway.  I did not have mill to do this, and instead took a lot of time and patience and used a drill bit and Dremel tool with a steel cutting disc, ever so carefully and slowly until I could just barely tap the key into place.  Worked like a charm.  And in that case, I didn't need to split the transaxle case and all to remove and install a new shaft, I did the work with it still right in the transaxle.  Cut a "V" in a 2x4 and laid the axle right in it, setting right on the floor, the weight of the tractor keeping the shaft firmly in place while I worked.

Edited by Brettw
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