What is needed to machine a crank?

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solomon

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Well i want to turn my tapered shaft (10hp Tecumseh crank) down to 3/4" and 3/16" keyed. What tools will be needed? I have a brother in law who is a machinist and he said his buddies could do it for free. All he needs to know is what machines are needed, And how long it will take. Thanks
 
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solomon

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okay cool, so how long do you think it would take? setup time and all. Because my brother in-law just pushes buttons lol, so he has to set up a time and date with his buddies. Thanks again.
 
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solomon

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Okay cool. Just talked to my brother in-law and we are going to machine it down on Friday.
 
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solomon

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Well my brother in-law said it sounds pretty simple. And his shop is more than capable of doing it and wouldn't mind one bit, since on Friday everyone their just makes stuff for themselves and does projects and what not.
 
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solomon

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haha yea its a cool place, i brought my 5hp flatty down thier a few months back and had the head milled and the ports ported out and what not, all really nice people
 
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VoodooChild

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I work in a machine shop, and i would bet that would take 1.5 hours to 2 hours. Set up time usually takes more time than the actual cutting. And if you know any machinist's, then you'll know they don't move fast. Measure twice cut once, do it once do it right, etc. etc...
 
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Yea i'd say 1-2 hours, depends on how many finish passes/if its a cnc or manual lath. Cutting the keyway afterwords would take half hour or so, maybe 45 minutes.
 
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solomon

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haha no way cutting the keyway would take that long! We could just throw it on the manual mill and use a 3/16" bit couldn't we?
 
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VoodooChild

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As long as you know its perfectly parallel to the cutting surface, which is part of the set up time. Then you have to touch off, and you can't just plunge the 3/16" bit all the way down in there, you do it in passes (less stress on tool, less heat etc.. etc..), and as you get closer and closer you have to measure after every pass. Machining is an art
 
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solomon

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i saw the dimensions on another forum here, i will be sure to bring the with me
 
Kaptain Krunch

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solomon said:
haha no way cutting the keyway would take that long! We could just throw it on the manual mill and use a 3/16" bit couldn't we?
Click to expand...

Go try it, its not just something you slap on and cut. You could probably do it in 3 passes (including a finish pass). But, you have to get it in there, make sure its level with a dial indicator (5 minutes if your lucky), then you have indicate on one side of the shaft with a wiggler, go to center, switch tool for a third time, touch off on shaft lightly, first pass, second pass, measure, third pass, measure, fourth if you messed up, take it out of the mill, de-burr with a file, or india stone or similar, check one more time, then your done.

Why do you think machinists charge so much?
 
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solomon

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well hopefully it wont take too long, i will see what they say when its looked at
 
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VoodooChild

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Kaptain Krunch said:
Go try it, its not just something you slap on and cut. You could probably do it in 3 passes (including a finish pass). But, you have to get it in there, make sure its level with a dial indicator (5 minutes if your lucky), then you have indicate on one side of the shaft with a wiggler, go to center, switch tool for a third time, touch off on shaft lightly, first pass, second pass, measure, third pass, measure, fourth if you messed up, take it out of the mill, de-burr with a file, or india stone or similar, check one more time, then your done.

Why do you think machinists charge so much?
Click to expand...


Yep spot on, if you throw it in there and make a pass, you'll get exactly that. A crooked, angled keyway that's the wrong size. Strong materials like crankshafts, you want to take only about 20-30 thousands off at a time.

And i'm not sure what you consider very much money, but the machine shop i work at (state college, physics and chemistry department instrument shop) charges 20 dollars an hour, which when you compare that to a mechanic shop is pretty cheap. But like i said, even drilling a and tapping the end of a shaft takes minimum an hour (maybee less if we get away with using a collet, and not having to indicate in a chuck)

Russ i'm confused by your statement that the keyway is half the size of the width, which if the keyway is 3/16" would mean that the distance from the top of the shaft toward the center would be .09375". But then you said that there square, meaning it would be 3/16" x 3/16"
 
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