Feeds & Speeds

Step Over/Step Down

These guidelines are simple starting points and are influenced by what you are cutting, how much you want to remove, and what you intend to cut it with.  The tool length, diameter, tool material, part fixturing, machine horsepower, as well as machining a slot versus a profile all ultimately have a large effect on part quality and tool life.  Inspecting finished parts carefully helps us to develop experience. 

• Radial stepover < 1/2 of tool diameter

  • Light roughing: 10% of diameter

  • Heavy roughing 30% of diameter

  • Finishing 3-5% of diameter

• Axial stepdown traditionally less than 1/2 of tool diameter.  Up to one diameter stepdown combined with shallower radial step overs can spread heat out along flute length as opposed to concentrating it near the end of the tool.

  • Slotting < 1/2 of tool diameter

  • Profiling up to 1.5 tool diameter but watch flute length.

• Plunge feed rate < 50% of calculated feed rate.

• You might wonder where does this stuff come from?  The material hardness and how it forms chips are large factors, see By the numbers

• The recommended speed and feed values published by tool manufacturers post are a great resource but you have to recognize these values are for optimum cutting circumstances.  Experience helps us to know we need to dial these back to start and inspect finished parts.

• It is wise to check values you are using and recalculate to confirm your numbers.

Materials

• Sandvik Workpiece Materials Knowledge ISO categories

• Identifying Plastics Lehigh Univ.

• Endmill selection for Plastics - Harvey Tool

• LMT Onsrud Cutting Data

  • MDF

Drilling holes speed & feed

http://www.norsemandrill.com/feeds-speeds-drill.php 

6061 Aluminum:

• 250 SFM for HSS twist drills

• Feed 0.001" per rev for each 1/16th" diameter +/- 0.001" overall

• Reduce speed & feed 50% if depth is larger than 4 drill diameters

• Peck drilling helps to clear chips and allows coolant inside.

Sawing

https://www.sawcalc.com/saw-calc