Machining and Millling the Seat Tube

Small elaboration on the previous post, while staring at some randomly selected chunks of aluminum contemplating how to hold a thin walled tube at just the right angle and index it such that the notches were lined up correctly it occurred to me that I needed another Corona. My previous drink that I had so carefully placed on the tail stock of the lathe had fallen and shattered into a wonderful wet mess of razer sharp aluminum chips and razer sharp glass bits. Anyhow, after I solved that problem it donned on me that if I made a common OD collet with a fairly precise machined ID that matched the tubes I will be cutting I could make a single tool that would mount in place of the tool post on the lathe. This would allow me to use the angle marks on the cross feed table and hopefully make repeatable cuts.


The only problem is the very limited supply of tools. Having no way to bore a hole in a block of aluminum 2.5" in diameter on the mill I decided the best course of action would be to use the four jaw chuck on the lathe and try to dial in the part and use the boring bar to make a precise hole. I planned on machining a T slot in the base of one large block of aluminum such that it would fit in place of the tool post and then bolt a second piece of aluminum on top. Once fastened together I would try my hand at setting up the four jaw and making the hole. Sounds easy right...

Some pictures of milled aluminum tubes

On a slightly different note, I have been doing a fair amount of welding of thin walled aluminum tube which I believe to be some of the hardest welding with which I have had reasonable success. (zinc + TIG + no idea what I am doing = fire hazard and poisonous yellow gas) So when I finished Star Trek I was pleasantly reminded how nice mild steel welds especially to tool steel, in this case an old center drill. However, earlier in the day I was messing around welding copper for the first time and I am confident that welding copper, even with a piece of wire for filler, is fantastic. It is so easy! Unfortunately, copper is also a fantastic conductor of heat which became abundantly clear while holding the filler rod in my left hand, even with the glove on it gets hot in a hurry. What it doesn't do in a hurry is cool off. Wait a long time before picking up the welded copper part then wait a bit longer. Once it is cool you can amuse yourself by heating up the oxide covered metal with your finger or breath and watching it dance around and the gracefully fly off into the air. Who would want to weld copper for fun?