Machining 303, 304 & 316 Stainless Steels
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:
- 303 Stainless is the most machinable and will machine similar to Steels like a 4140 Steel and will be run at similar Speeds/Feeds but it is also the least stable and most likely to bow or warp in long or thin walled parts when machining. The Machinability Rating of 303 Stainless Steel is 78%
- 304 and 316 will Machine similar, they both need to be run at slower speeds/feeds than a 303 Stainless but they are more stable and better material choice for long or thin walled parts as they will be less likely to bow or warp (as long as you keep tool pressure down and don't add too much stress into the part). The Machinability Rating of 304 Stainless Steel is 45% and The Machinability Rating of 316 Stainless Steel is 40%
Milling 303, 304 and 316 Stainless Steel
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:
Click Here to See the High Performance Chipbreaker End Mills for Stainless Steel we Recommend
Click Here to See the High Performance Square Corner End Mills for Stainless Steel we Recommend
Here are Speeds/Feeds to Start at:
*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)
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
Drilling 303, 304 and 316 Stainless Steel: 1/2" and Under
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:
Cobalt TIN Coated Stub Drills
Cobalt TIN Coated Jobber Drills
*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
Run 303 Stainless at 70 SFM. Run 304 & 316 Stainless at 50 SFM
