Right Bit For Sherline Mill

I need to do a side cut on a tube of nickel and make it into a octagonal shape. I have a mitre attachment for the sherline mill and I will be doing 45 degree cuts 17 mm in length. What is the best tool to make the cut? Right now I am using a 1/4" end mill to do the cut but it is rough. I use the middle part of the end mill.

Another question, I have a Chinese metal lathe which works good. When you turn a piece of steel round stock at what point should the cutting edge contact the round stock? Should it be in the middle of the piece or a bit above or below. I'm going to turn down some 3/4" stainless round stock, what would be the proper cutting bit to use?

Thanks for any help you might be able to give me.

I am not familiar with a mitre attachment for the Sherline mill. Could you post a pic?

The larger the end mill the less deflection so use the largest end mill you have; 3-4 flutes would be preferable.

For turning, the cutting tip of your tool should be on center. You can use brazed carbide, inserted carbide or HSS/cobalt - your choice. If the lathe is a light one, HSS or cobalt will work best and give you a better finish. Stainless steel likes a lot of relief angle at the side cutting edge.

I'd like to see the meter attachment too...I have a sherline 2000...it's handy dandy...but its tiny

As is often the case the tool that works is the correct choice regardless of what may be considered conventional practice, change your approach until it works.

As far as lathe tools you will not go wrong holding the tool on the spindle center line, you may or may not give up some speed and finish but you will never know this until you try different methods on your machine and particular application, conventional practice is a starting point not to be confused with "must be done this way".

Do whatever works for you.