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The Fine Art... of Parting Off :: Blog Post

Jerry

Radial Skybolt Builder: 220.45% completed
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Drove over to Whitey's airport to ask if I could use his lathe to do some work on the Torque Tube Controls. (If you recall... I tried using my micro lathe and it was micro small for the job... doesn't happen that often that it's too small)


Arrived at the airport and didn't see his truck at the hangar. Waited a few minutes then started driving back down the dirt drive to get back to the main road and in doing so pass around the back of his house. Just so happens Whitey saw me drive past the first time and was waiting there to wave me over on my way out. Pulled off to the side and got out. I shouted out a hello, and he said to come on in. Ended up talking planes for the next hour and a half. 'Bout that time it was lunch and Whitey, Bob (the resident milling expert) and myself grab a bite to eat at a sub and pizza shop down the road... talk more airplanes.


Back to the airport and Whitey shows me the basics of running the lathe he has and I have at it. Plan for the day was to square off and cut to size the three collars that I cut off with the chopsaw the other day and to square up and cut off six collar stays (only need two collars andtwo stays... the rest are for that learning I've been so use to seeing lately)


Let me tell you now, as I've mentioned in the past... the right tool for the job makes the job enjoyable. Using that lathe to make a pile of short tubes nice and square was a joy. Loved doing it. An hour and a half later and I had a pile of short tubes that didn't look like much... but when I'm flying this Skybolt with it's silky smooth controls I'll think back to today.


As I'm there working at making these small tubes, Whitey and I are talking about the Jacobs I'll be hanging on the front of the Skybolt. Some how we got to talking about the starter, which is an inertia starter (crank it to get the gears going and then flick a switch to start the engine.) He says, ya know Jerry, I think we can set that up to run off a battery and you won't need to get out and hand crank it. Set it up so that you have a lever that engages a gear that is connected to a small moter. A switch on the lever to start the motor. Lever forward, start the motor which in turn cranks the inertia starter which eventually starts the engine. BRILLIANT !


In addition to being a prop head... Whitey is a motor head from way back. He wrote an article for "Contact" magazine a few years back. Has a Ford V-6 in his homebuilt Bellanca CruiseAir.


Next time I'm over, he said to bring the inertia starter by so that he could look at it and start working on the set-up. sweet...


Oh, wait... back to the lathe. Whitey mentioned it, and JimW told me once, there is an art to parting off a piece from the lathe. Something that is learned from doing it. I'll give you a heads up on a little secret that I found when parting a piece. (worked for me at least)


Working on the lathe you take it slow and steady... all the time. But, when you are getting close to parting off that piece, real close to severing it from the main piece, the material starts to get real thin. At that point it won't be cutting through the material, it is, from my observation, actually pushing the thin wall of the remaining material in and not cutting it. Keep going slooooow and steady, even slower than before. If you make the mistake of feeding the bit into the piece faster, because you think it's not doing it's job, at a point, not too far in the future, that bit is going to catch and jam, with a good possibility of ruining the piece you've been slowly working on.


How did I discover this ? By almost screwing up the third piece I cut. I guess I got a little over confident with the lathe, since the first two were cut off without a problem. (thought I was a natural) The third, I'm going along and all of a sudden the bit jams in the tube and I'm fighting to pull it out. I get the bit pulled out and stop the lathe only to find an elongated hole in the place I was cutting. Figured I was that far into cutting it so I eased the bit back onto the piece, finished the cut and it turns out that I was able to save the piece.


I took it slower the next time; observing myself and what the material was doing. Go slower as you reach the "parting" point, ever so gradual, and the piece will literally roll off as it parts ways. It took my about an hour and a half to square up and cut nine sections of tubes. Might not look like much, but I learned a lot and it's what I needed for the project at hand. Can't ask for anything more than that. Edited by: Jerry
 

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