The Magnum Super Premium drills will substantially outperform cobalt drills in work hardening stainless steel applications. This performance advantage is the result of construction differences between the two types of drills. Cobalt drills, manufactured to Type J NAS907 specs, has a very thick web. This web is necessary to limit breakage of the brittle cobalt steel. Magnum Super Premium drills are made of special Hi-moly tool steel, which is much tougher than cobalt steel. The web on a Magnum Super Premium drill can be thinned considerably due to the toughness of the steel.A Magnum Super Premium drill with its thin web will penetrate the work hardening stainless fast enough to continually cut beneath the chip which is hardening from deformation. This means the drill is cutting softer steel. The cobalt drill, with its thick web, cannot be fed at a fast enough rate to cut beneath the area which is hardening. As a result the cobalt drill is continually drilling into hardened steel.

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*Remember to Cut the Feed Rate in 1/2 when coming into corners. Also, if you need to slot then your axial DOC should have 1/2 the Tool Diameter (For Example a 1/2" Diameter End Mill should take a Max Axial DOC of 1/4" when slotting to allow chips to clear)

We have found using a 5 or 7 Flute Variable Pitch End Mill ideally with a Corner Radius works best taking a Full Flute Length Axial DOC along with a Light Radial DOC (7%-11%) of the Tool Diameter when profile milling.  This allows you to utilize the Helix of the End Mill so that it leads into the cut lowering the tool pressure and keeping the heat formation down.  A Chipbreaker Style Rougher/Finisher End Mill is also ideal as it will keep tool pressure down and break the chips so that they get out of the way (a lot of the times the chips stay around the workpiece when using an End Mill without chipbreakers and re-cutting chips will break an End Mill).  Also, if you can have a Corner Radius then do it as it will double your End Mill over a Square Corner End Mill in Stainless (and then come in with a Square Corner as a Finisher).   Here are the End Mills we recommend for Profile Milling Stainless Steel:

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The Ideal Solution is an Optimized Tool Path that accounts for the End Mill coming into corners as well as chip thinning so you are always at a constant chipload. If you are running an optimized Tool Path then Click Here for Speeds/Feeds in Stainless

Lathe cuttingspeedchart PDF

Here are recommendations for Machining 303, 304 and 316 Stainless Steels.  Stainless Steel is tough on tooling but with the correct tools as well as speeds/feeds you can do well in machining Stainless Steel. First let's break down the differences between 303, 304 and 316:

In Drilling 303, 304 & 316 Stainless Steel a Carbide Coolant Thru Drill is the ideal option.  It will give you the fastest cycle times along with the longest tool life.  With a Coolant Thru Drill you do not need to peck as the coolant thru will evacuate the chips but with a Non Coolant Thru Carbide Drill or HSS/Cobalt Drill you do need to peck to evacuate the chip (you will want to take 0.5 x Drill Diameter Pecks with these drills as shown below).  If you do not have a coolant thru spindle then a non coolant thru drill will also work well, you will just need to peck.  If it is shorter run and you want to keep your costs down then a Cobalt Drill will also work well.  Here are links to the Cobalt and Carbide Drill we recommend along with speeds and feeds:

*With Cobalt Drills you need to peck at Half the Drill Diameter to make sure chips evacuate (a 1/4" Drill should take 1/8" Pecks). You can run the drill 2XD on the initial plunge and then take 0.5XD Pecks to cut cycle Time