Proper Order of operations

[JWB_Machining]

Hey,

I need to take some aluminium bar stock and make compression test samples. The samples need to be twice as long as the diameter. I'm starting with 1" stock so I need to clean it up then face the ends till I reach the correct length. What's the best order of operations? Should I use the band saw to cut the stock into small lengths then turn them down n face them? Or is is better to turn down the stock then cut them then face them? Also would it make sense to cut the stock with a cut off tool or no?

On a sort of related note I was attempthing to turn down a 15" length of my bar stock. I center drilled on end and then used a tail stock to support my length. When i was turning it down however towards the middle my finish went from beautiful to wavy n started not sounding all the right. Is my stock just too small (1" Diam) to suspend that long or was my depth of cut just too much or too little?

Thanks.

[gene rhodes]

"Should I use the band saw to cut the stock into small lengths then turn them down n face them? Or is is better to turn down the stock then cut them then face them? "
To answer this question, in my experience, facing is usually the predecessor to any operation...allowing you to attain a "known" dimension from which to get your needed length

Is my stock just too small (1" Diam) to suspend that long or was my depth of cut just too much or too little?
This question sounds as though there could be a myriad of different problems here....feedrate too slow/fast per RPM's, both of which will cause this "vibration", chuck pressure, quill stop pressure, tool holder type, etc. Depth of cut, unless too deep, is usually a secondary issue unless your going for an extreme amount/cut. this is determined by the type of insert you are using.

[Geof]

How many are you doing?

For one I would turn it to size and face from a length of stock just held in the chuck; no tailstock because the maximum length is 2".

Following turning I would cut it slightly long on the band saw and then face the other end freehand; i.e. face, measure and then face again to get the required length.

For doing ten or more I would part them off after turning and facing and would rig up a stop inside the chuck so they could be turned to length without constantly checking once the first one was done.

Regarding your vibration problems with 15" of 1" diameter aluminum it is a combination of length, flexible material, depth of cut, feed, speed and tool nose radius.

For best results grip the stock in the chuck and support it with the tailstock center do not do it between centers. Gripping it in the chuck improves the stiffness.

For roughing with a largish nose radius you could take a decent depth of cut around .05 to 0.1 and a feed of 0.005 or more running your machine as fast as possible.

For finishing use a small nose radius, maybe .02" depth and a feed of .003 or so depending on the finish required. Again you should be able to go at full rpm.