Mill Tooling Question

[kochevnik]

I have some 15 inch long 2" pieces of mild steel angle iron that I am trying to get a nice mirror like finish on one of the faces. At first I used a cobalt end mill to rough mill it down and then a fly cutter to finish it off. It worked ok, but took a long time - I have a Tormach (1-1/2 HP), not a nice new VMC like a lot of you guys

Later I tried just the fly cutter, taking .005 DOC, 2 inch wide - 4500 RPM (max on my mill) and 24 IPM. This works swell but the carbide cutter doesn't last very long. This is dry milling BTW.

What I would like to do is find some good quality indexable end mills that would do the job of the fly cutter and end mill combo. Considering my situation, can any of your give me some ideas of what I should be trying ? Feeds and speeds wrong ? Will an indexable end mill give me as good of a finish as a fly cutter ?

Has anyone used these Octa-Mills from K-Tool :

http://www.ktoolinc.com/octa/octa-mills/octa-mill.html

Any and all help and advice great appreciated.

Thanks.
kochevnik

[HuFlungDung]

A face mill can do a good job. Make sure that the effective facing diameter of the mill is larger than the width to be faced if you want that 'mirror look'. Also a decent depth of cut will enhance the shine of the cut. Perhaps .010" minumum .030" would be better, but you might run out of horse before then

The workpiece needs to be well supported. A piece that long will want to vibrate if you take a heavier cut, so full length support is necessary to dampen vibration. This might involve 2 vises for example.

Do not get carried away with rpm. 400 to 600 surface feet per minute is sufficient to get carbide above the critical speed which enhances chip flow and gives you a smooth surface, instead of the torn look. For a 2.5" face mill, that would be about 700 rpm, on up to maybe 1000 rpm, depending on the quality of coated carbide insert which you should be using on steel.

Feed the tool as hard as you dare. A so called 'wiper insert' enhances the finish of the tool, while maintaining an aggressive feedrate. Somewhere between 20 and 40 ipm for a 4 insert tool might be a start.

[DareBee]

Listen to Hu he knows

The 4500 RPM is what fried your fly cutter - That is like 1700 SFM

IMO the Octo cutters are VERY nice. Super free cutting high positive geometry that give nice surface finish. The inserts are pricey though.

Correct speeds and feeds are critical to proper performance.

[kochevnik]

Thank you Mr. Hu - some good information there !

As a newbie I have a lot of things to learn - one of the hardest is the combination of feeds speeds and tooling. I am getting better tho


Another newbie question if you don't mind - I used a water based coolant and I have a cheap Chinese vise (it's all I can afford right now) - and it is rusting something fierce. If I were to spend the big bucks for something like a Kurt, would I have the same problem ? I was reading that vegetable oil based coolants might be the way to go. Anyone have any recommendations ? I would really hate to pop for a $600 vise and then see it turn to crap like this one. And I should mention that the very first thing I did with this vise is to cover it in Bullfrog Rust Preventer - guess that didnt work

Suggestions ?

[HuFlungDung]

I'm not sure of a method to prevent rust except to take the vise off every night and dry it off I think the Kurt vises are a better quality cast, but are not totally immune to the rust effect.

I may have had a small degree of success by using paste wax on the bottom of the vise and on the table top. Give the wax time to dry before flooding everything with coolant. Keep the coolant concentration up in the proper range to replenish spent anti-rust compounds.

[DareBee]

Your problem is your coolant.

Nothing at all wrong with a decent water based coolant.
Proper mixture is usually a 5% concentration (check with manufacturers specs). The stuff I use I can even leave the machine laying in it and it turns into a clear protective slime. I don't suggest leaving your stuff laying in coolant BTW.
Penetrating oil will also help keep things rust free between shifts.

[Geof]

I have found the manufacturer's specs for water based coolants will not always prevent rusting, they are designed to give the minimum concentration for the cutting function. Just increase the concentration until it is high enough that when the water evaporates off there is s film of coolant left to prevent rusting.

[msomerville]

Originally Posted by Geof I have found the manufacturer's specs for water based coolants will not always prevent rusting, they are designed to give the minimum concentration for the cutting function. Just increase the concentration until it is high enough that when the water evaporates off there is s film of coolant left to prevent rusting.

what he said