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Old 10-03-2012, 07:40 PM
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Default No Keyway? No Problem!

We've talked about cutting your own keyway on this forum before. I just ran into exactly the right situation to address this. I know that others have done it, but not much has been written.

Unfortunately, the PTO shaft on my trusty (and becoming notorious) H60, did not have a standard 3/16" keyway cut along it's length. What it did have, was a Woodruff keyway. A woodruff key is a half-round piece of a specific length, rather than a basic rectangle of variable length. What it means to you, is that no regular shaft components will fit. you're either off to a machine shop to have a standard keyway cut, or you're doing it by hand. So I did.

I used a length of 3/16" rectangular key stock and a hardened steel scribe to mark the location on the shaft. Then, I put a thin kerf cutting wheel in the flexible shaft extension for my Dremel. Using the cutting wheel, I "traced" the scribe marks into the shaft, to the approximate depth required. I took off the cutting wheel and installed a grinding wheel that was a little less than 3/16" thick to remove the centre of the keyway. Carefully and gently, I ground the keyway, pausing every couple of minutes to check my progress and let the shaft cool. To check progress, I used a 3/4" bore LoveJoy coupling and the same key I used to mark the shaft. Once I reached the point where the key would just fit between the shaft and coupler, I cleaned it up a bit and called it done. I apologize for the dark, crummy pics. I used my phone, and I was racing dusk.

The first pic shows the shaft in an unaltered state with the Woodruff keyway. Second pic is after tracing the lines with the cutting disc. The third shot is a progress pic, about halfway, checking with the key. Fourth pic is very nearly finished. It was too dark for a picture after I cleaned it up and called it finished.

Start to finish, including very carefully measuring and marking the location, was about 40 minutes.

DIY, baby, DIY!

EDIT- Upon request, I have added a pic of the "Dremel" and accessories I used. In this case, the tool is a Dremel-like mini electric die grinder with a 1/8" collet. Accessories include a flexible extension shaft which you hold like a pencil and allows excellent dexterity. The cutoff wheel is a 1.25" diameter fibre-reinforced abrasive wheel with a very thin kerf. The grinding wheel is an abrasive type, 3/4" diameter, and about 5/32" thick. Not shown are a sharp carbide scribe, a 3/16" x 2" key, and a small square.
Attached Thumbnails
key1.jpg   key3.jpg  

key5.jpg   key4.jpg  

dremel.JPG  
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Last edited by Doc Sprocket; 10-08-2012 at 11:10 AM. Reason: tool pic added
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  #2  
Old 10-03-2012, 07:49 PM
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looks good! Good step by step as well.
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Old 10-03-2012, 08:04 PM
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thanks! ill remember this for when i need to cut a keyway
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Old 10-03-2012, 08:36 PM
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Nice cutting job
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Old 10-03-2012, 08:41 PM
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Why wouldn't a woodruff key fit in a straight keyway clutch or sprocket?
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Old 10-03-2012, 08:59 PM
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First, the location may not be appropriate for the specific part. It is very restrictive. Second, a large number of clutches and CVTs have the key cast right into the bore, so it will not work at all. This was my motivation, here- the clutch I needed to mount had a cast-in key- so you can't even get it ON the shaft, much less locate it correctly.
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The Manual- "Just the manufacturer's opinion of how to put this together."- Tim "The Tool Man" Taylor
Put down the wrench, and come out with your hands up!- Me!
Wrench, Wheel, Wreck, Repeat...
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Old 10-04-2012, 02:36 PM
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Finding a way to fit a clutch on my Sachs engine's 15mm shaft is turning out to be a lot more difficult that I thought it would, as it too has a woodruff keyway. The 5/8" clutch I already have has a built-in key. I guess I will either have to find a clutch without the key in it, or use your Dremel method, toystory.
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Old 10-04-2012, 03:33 PM
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Thats nice there!
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Old 10-04-2012, 04:57 PM
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Default Woodruff keys

Industrial woodruff keys are mildly hardened and are size-for-size on the pockets they are to be installed in. They are extremely robust for their size; and having 2/3 of their height press fit into the shaft they are mounted in, they are extremely difficult to lose from an assembly. That being said, if the location of the key isn't right for your application, your options are limited.

Toystory's solution is a good one; just be aware that you need to approach this operation like just that: a life threatening operation. Done right, the patient lives; done wrong...... you'll need to break out your purple stoll and the holy water, so you can administer last rites.......

Hope this helps.
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Old 10-04-2012, 06:41 PM
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Quote:
Originally Posted by machinist@large View Post
Industrial woodruff keys are mildly hardened and are size-for-size on the pockets they are to be installed in. They are extremely robust for their size; and having 2/3 of their height press fit into the shaft they are mounted in, they are extremely difficult to lose from an assembly. That being said, if the location of the key isn't right for your application, your options are limited.

Toystory's solution is a good one; just be aware that you need to approach this operation like just that: a life threatening operation. Done right, the patient lives; done wrong...... you'll need to break out your purple stoll and the holy water, so you can administer last rites.......

Hope this helps.
Absolutely right on all counts! It was useless as it was, so I finally bit the bullet and did it. It needs to be noted that I was working slowly, gently, and carefully. I was nervous.

I run a very tight budget on my projects, and a new crankshaft was not in that budget... No pressure...
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Wrench, Wheel, Wreck, Repeat...
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Old 10-05-2012, 04:14 AM
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yeh i use the little lawnmower woodruff key to turn the pully on my motorbike and it works sweet
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Old 10-05-2012, 06:02 AM
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Wow, that looks great! Nice job mate!
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Old 10-08-2012, 03:20 AM
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Good job Chris. A bit of time and patience can save a person a whole bunch of money. Some people would immediately go run out and buy a new crank, or a new engine. All that is really needed is a small amount of savvy and some elbow grease.
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Old 10-08-2012, 10:14 AM
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Chris,

Would it be possible to see some pictures of the dremel tools you used to cut this?
Thanks in advance,
Alex
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Old 10-08-2012, 10:23 AM
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Absolutely! I had intended to include pix in the original post, but it got a wee bit dark. I will shoot and insert the pix within hours.
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The Manual- "Just the manufacturer's opinion of how to put this together."- Tim "The Tool Man" Taylor
Put down the wrench, and come out with your hands up!- Me!
Wrench, Wheel, Wreck, Repeat...
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Old 10-08-2012, 12:31 PM
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Picture is added! Thanks!

Will have to try this on my 8hp Kohler engine too. We'll see how it goes.
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