Machinist Group of Northeast Indiana

Cutting Tool Theory Intro Speeds and Feeds July 8, 2014

• • • • What RPMs & IPM would you run?

Specifications (dry machining) Material: 1018 CRS Endmill: – 5/8” diameter (.625) – 8 flute – High Speed Steel – TiN Coating Machine limits 7.5 horsepower 550-10,000 RPMs 200 IPM max (X&Y axis) Amount to remove – “Z” total depth = 1.22” – “Y” total material = 3.5” – “X” total material = 6.25”

Important Formulas (applies to any rotating tool)

Vc x 12 n =

p

x Dm

OR better known as

SFPM x 3.82

RPM = Diameter

D

m

f

n

a

p

n P

c Q​ Lathe (Sandvik Coromant) Machined diameter mm (inch)​ Feed per revolution​ Cutting depth Spindle speed Net power​ Metal removal rate

h

m

h

ex Average chip thickness​ Maximum chip thickness​

T

c

l

m

k

c Period of engagement​ Machined length​ Specific cutting force​ KAPR​ Entering angle​ PSIR​ Lead angle​ mm (inch)​ mm/r (inch/r)​ mm (inch)​ rpm​ kW (HP)​ cm 3 /min (inch 3 /min)​ mm (inch)​ mm (inch)​ min​ mm (inch)​ N/mm 2 (N/inch 2 )​ degree​ degree​

Milling Machines (multi-flute cutters)

Vf = n x Fz x Zn OR IPM = RPM x IPT x # of Flutes

Milling (Sandvik Coromant)

• • Milling: Up or Down?

Conventional Milling (fights the rotation) – Aka: UP milling – Starts at ZERO chip thickness and progresses to MAX – In most materials, should only be used with machines with backlash Climb Milling (acts like a wheel) – Aka: Down Milling – Starts at MAX chip thickness and progresses to ZERO – In most materials and set-ups, this is the best choice

Face Milling

Climb Milling Feed per Tooth Maximum chip thickness Working engagement average chip thickness

Traditional Milling Engagement

Radial Chip Thickness

• How does new concepts in metal cutting help us on smaller machines?

Specifications (dry machining) – Material: 1018 CRS – Endmill: • 5/8” diameter (.625) • 8 flute • High Speed Steel • TiN Coating – Amount to remove • “Z” total depth = 1.22” • “Y” total material = 3.5” • “X” total material = 6.25” Machine limits 7.5 horsepower 550-10,000 RPMs 200 IPM max (X&Y axis)

What we ran at SA with our old tools • • • RPM = 2200 IPM = 190 1.22 = “Z” depth of cut per pass – Total depth needed to finish part • .030 = “X” step over (radial width of cut)

• • • • • Results: It took 208 passes to finish the part 3 minutes 50 seconds: Total time to remove 27 in 3 of steel We actually changed our cutting to G00 (rapid) moves Cutter looked like it was new when we were done Part and tool was cool enough to touch at the completion of the material removal

Good Reading: • • • • Cutting Tool Engineering Magazine “Limited Engagement” by Bill Kennedy July 2011 / Volume 63 / Issue 7 http://www.ctemag.com/aa_pages/2011/110 705-Milling.html