TECHNICAL INFORMATION

TECHNICAL INFORMATION
WORKPIECE MATERIAL	Specific Grades	Speed SFM	FEEDRATE (inches/tooth) Tool Cutting Diameter
WORKPIECE MATERIAL	Specific Grades	Speed SFM	1/8	3/16	1/4	5/16	3/8	1/2	5/8	3/4
Low Carbon and Leaded Steels <25Rc	1005-1029 12L14	550 "	0.0003	0.0006	0.0001	0.0013	0.0017	0.002	0.0027	0.0035
Medium Carbon and Alloy Steels 25-35Rc	1030-1050 4130, 4140, 4340	450 "	0.0003	0.0006	0.001	0.0012	0.0015	0.0018	0.0025	0.0032
Medium Carbon & Alloy Steels 36-46Rc	1040, 4130, 4140 4340, 52100	250 "	0.0003	0.0004	0.0007	0.0009	0.0012	0.0015	0.002	0.0025
Aluminum Alloys	6061, 6066	1200	0.0004	0.0008	0.0012	0.0017	0.0021	0.0025	0.0035	0.0042
Brass	Free Machining	1000	0.0004	0.0007	0.001	0.0015	0.0018	0.0022	0.003	0.0037
Titanium and Titanium Alloys	Commercially Pure 6AI4V	350 250	0.0003 0.0003	0.0005 0.0004	0.0007 0.0006	0.0009 0.0008	0.0012 0.0011	0.0015 0.0013	0.0021 0.0018	0.0028 0.0022
Nickel Alloys	Inconel 718, Waspaloy Hastelloy Monel 400 series Monel 500 series	80 100 200 140	0.0003 0.0003 0.0003 0.0003	0.0004 0.0004 0.0006 0.0004	0.0005 0.0005 0.0008 0.0006	0.0007 0.0007 0.0001 0.0008	0.0009 0.0009 0.0013 0.0011	0.0012 0.0012 0.0018 0.0015	0.0016 0.0016 0.0022 0.002	0.0022 0.0022 0.0028 0.0025
Stainless Steels	300 series 400 series 15-5PH, 17-4PH Nitronic 32,33,40,50,60	350 400 250 150	0.0003 0.0003 0.0003 0.0003	0.0004 0.0004 0.0004 0.0004	0.0006 0.0006 0.0006 0.0005	0.0008 0.0008 0.0008 0.0007	0.0011 0.0011 0.0011 0.001	0.0015 0.0015 0.0015 0.0014	0.002 0.002 0.002 0.0018	0.0025 0.0025 0.0025 0.0022
Cast Cast Iron	Gray Ductile Malleable	500 425 400	0.0004 0.0005 0.0004	0.0006 0.0007 0.0006	0.0009 0.001 0.0009	0.0011 0.0013 0.0014	0.0014 0.0017 0.0014	0.002 0.0025 0.002	0.0028 0.0032 0.0028	0.0035 0.004 0.0035
Tool Steels	H10, H12, A2 D2	325 225	0.0003 0.0003	0.0004 0.0004	0.0007 0.0007	0.0009 0.0009	0.0012 0.0012	0.0015 0.0015	0.002 0.002	0.0024 0.0024

When cutting an internal thread the linear feedrate has to be reduced to compensate for the ratio of the tool's cutting diameter to the major diameter being cut. If you do not compensate, the feedrate that the cutting edge sees will be much greater and tool failure will occur. The threadmilling feedrate is equal to:

((major diameter - cutter diameter)/major diameter) x linear feedrate

Example #1
Thread Diameter to be cut (D2): 3/8
Threadmill Diameter (D1): .285

If the linear feedrate calculated from the feeds and speeds above came out to be 10 IPM the programmed feedrate for the internal threadmilling cut would be: ((D2-D1)/D2) * linear feedrate or ((.375-.285)/.375)*10 or 2.4 inches per minute

Example #2
If you were going to cut a 1/2-13 thread in a low alloy steel that was less than 25 Rc hardness:

Question: Which tool would you use?
Answer: #TM50013 which has a .350 cutter diameter and 4 flutes

Question: What surface speed should you run?
Answer: 350 - 500 (We will use 400 SFM)

Question: What is the chipload per tooth?
Answer: .0025-.0035 per tooth (We will use .003"/tooth)

How do you calculate RPM's?
Take 3.8 divided by the threadmill dia and multiply by the SFM
Example: ((3.8/.350) * 400 SFM = 4343 rpm

How do you calculate linear inches per minute?
Take the ("/tooth) * (# of flutes) * RPM's
Example: ((.003" * 4 flutes) * 4343 RPM's = 52 linear "/min

What will be the programmed feedrate when cutting a 1/2-13 internal thread?
Answer:((D2-D1)/D2) * linear feedrate or ((.500 - .350)/ .500) * 52 ipm = 15.6 IPM