Cast iron or mild steel for an overarm?

Posting here in the SB forum, because I'm going to have to make a new overarm to adapt a Porter Cable milling head to my Burke #4 horizontal mill, and I'm going to be doing it on my SB9A. There is no Porter Cable forum and no Burke forum, and this seems to be the forum to go to for answers and opinions. So here goes.

I need to make a new overarm shaft to adapt my Porter Cable Mark II vertical milling head to my Burke #4 horizontal mill. Finished dimensions will be 2" diameter, about 16" long and will need to be bored for the milling head's 5/8" drive shaft and bearings.

Question is, would it be better to make this shaft from mild steel, cast iron, or something else. The mild steel would be easier to machine on my SB9, but what about vibration and stability for milling with the vert head? Would cast iron be better? Cost is about the same. Other options?

I'm also going to have to extend the 5/8" drive shaft, but I'll cross that bridge when I get there.

The easiest thing, if you have a local supplier, would be to buy a length of turned&polished (TP or TGP) 2" 1045 so you can start with the finished OD.

Grey cast iron does a better job than steel for vibration dampening, but iron is probably the better choice for rigidity and is the hands-down winner for strength and resistance to shock.

Yep, I agree. Twer it mine I would go with a heavy wall steel tube.

Pete

Are you really able to drill 8 inches deep from each side of the work piece on your lathe? you would need a long bed for that. I would buy heavy wall tube as well.

allan

Speedy Metals has 2.25 OD X .500 wall DOM. It would still be 3/8 wall if finished 2.000 OD

johnoder said:

Speedy Metals has 2.25 OD X .500 wall DOM. It would still be 3/8 wall if finished 2.000 OD

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That sounds plenty heavy enough to me. I have a Benchmaster vertical mill that's about the same size. They made a horizontal
version where the horizontal spindle replaces the arm for the vertical spindle. Finding the horizontal is difficult and expensive so
I've contemplated making one. The mounting is very similar to yours. I would use that tube for mine!

Pete

discountsteel.com has that DOM in almost every size you can imagine. OD is pretty good, ID may need some work.

Here's a forum I've used for years on Burk/Millrite machines:
https://groups.yahoo.com/neo/groups/BurkeMills/info