Slit sawing a shaft question

[Forty Niner]

I want to make a replacement shaft for a carburettor butterfly valve.
The engine is from a real vintage aircraft - so much regrets.

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No offense intended, but if that vintage aircraft is meant to fly again I would think long and hard about making that shaft to anything less than perfect. No jury rigging, no Dremel, no hand holding, no guessing. That butterfly must perform a critical function. I wouldn't fly that plane unless that shaft and butterfly was made to original blueprint sizes and fits. Get it done professionally if you don't have the right tools and experience.
This ain't no lawnmower engine.

My 2 cents.

 

[Dave Smith]

just because we use the tools we have and make many parts by hand doesn't mean we compromise on the desired result of our work---we give advice to those who ask and I'm sure we all understand they want ideas to help them do the job to solve their problem with the tools they have.---not all projects have available blueprints---a carb butterfly is not that complicated---I'm sure he will do a good and rewarding job of making his part to work as needed---Dave

 

[12bolts]

All good now

Next reaction was "Duh - yeah! That is how we don't spell "shaft" in the title, and don't know how to edit it". Sorry about that!

And nothing to be sorry about. It may be hard to believe, but even machinists make mistakes. Or so somebody told me once Not sure I ever did though....

 

[Billh50]

Whether this engine is to fly or not. When someone is taking the time to rebuild something vintage, they try to make it exactly the same as it was originally. The part in question is not an easy one to make without a miller. The slit must be located on center. That aside. I would make the slit first. Do the turning and threading on the one end in a collet with a shim cut to fit the slot. Leave the shim in the slot to drill and tap the cross hole and again hold in a collet to drill the pin hole in the end. When done remove the shim.
Of course making a print of the original would be nice but it may be difficult to figure out how much that twist has shortened the rod.

 

[brino]

Hi Graham,

There's been lots of great advice above, so I've just been following it quietly.

Bill struck on one key part:

The slit must be located on center.

That made me picture how I'd do it........and since you say you do not have a mill and that you're a beginner, I thought I'd add this thought.

If I was setting this up on the mill, I'd mount the cutter on an arbour in the spindle, and hold the part to the table. To get the slit on centre, I would bring the part towards the side of the saw until it just kisses it and call that "zero", then knowing the thickness of the blade and the diameter of the rod, you can use the table feed dials to get it on centre.

How do you do that on a lathe since the carriage movement left/right likely does not have a dial?
I had two thoughts:
1) fix a dial indicator to the lathe ways to indicate the carriage position, there are several examples of that here. If you cannot find one, let me know and I'll dig some up. (or of course use a DRO if you have one on the lathe!)
2) you could turn your top-slide to be 90 degrees to the lathe axis, that is parallel to the ways, then you can use the graduated top-slide dials to move the part exactly.

Good Luck, and please let us know how you make out.

-brino