Speed and feed confusion
Hi All,
Must be a senior moment but I am stumped. 1/2" dia. two flute carbide cutting SFM 850, cut per flute 0.002" it calculates out to around 6500rpm at 26-IPM 1/2" dia. two flute HSS cutting SFM 425, cut per flute 0.002" it calculates out to around 3250rpm at 13-IPM No surprises there. However, I don't like running the the spindle at top speed (3000rpm) so I tried to figure the IPM for say 2000rpm. My thinking for carbide... 6500 / 2000 = 3.25 26 / 3.25 = 8 IPM at 2000rpm OK, still so far so good, but using that same thinking with HSS 3250 / 2000 = 1.625 13 / 1.625 = 8 IPM at 2000rpm HUH??????????????????? Where am I going wrong here? The HSS should be half the carbide IPM. Dave |
Speed and feed confusion
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Speed and feed confusion
Dave, I can't do that wrote:
Hi All, Must be a senior moment but I am stumped. 1/2" dia. two flute carbide cutting SFM 850, cut per flute 0.002" it calculates out to around 6500rpm at 26-IPM 1/2" dia. two flute HSS cutting SFM 425, cut per flute 0.002" it calculates out to around 3250rpm at 13-IPM No surprises there. However, I don't like running the the spindle at top speed (3000rpm) so I tried to figure the IPM for say 2000rpm. My thinking for carbide... 6500 / 2000 = 3.25 26 / 3.25 = 8 IPM at 2000rpm OK, still so far so good, but using that same thinking with HSS 3250 / 2000 = 1.625 13 / 1.625 = 8 IPM at 2000rpm HUH??????????????????? Where am I going wrong here? The HSS should be half the carbide IPM. Dave The logic is correct, but the math reasoning is wrong. The calculated figure of 8 IPM for HSS is not based on half the surface footage of carbide, as the spindle speed is 2000 RPM for BOTH, which equates to the same SFM for the HSS as the carbide, therefore with the same chipload, the feed will be the same. 2000 RPM = about 250 SFM -- Steve Walker (remove wallet to reply) |
Speed and feed confusion
On 2010-06-06, Dave, I can't do that wrote:
Hi All, Must be a senior moment but I am stumped. 1/2" dia. two flute carbide cutting SFM 850, cut per flute 0.002" it calculates out to around 6500rpm at 26-IPM 1/2" dia. two flute HSS cutting SFM 425, cut per flute 0.002" it calculates out to around 3250rpm at 13-IPM No surprises there. However, I don't like running the the spindle at top speed (3000rpm) so I tried to figure the IPM for say 2000rpm. My thinking for carbide... 6500 / 2000 = 3.25 26 / 3.25 = 8 IPM at 2000rpm OK, still so far so good, but using that same thinking with HSS 3250 / 2000 = 1.625 13 / 1.625 = 8 IPM at 2000rpm HUH??????????????????? Where am I going wrong here? The HSS should be half the carbide IPM. You are using the same feed per tooth, the same RPM and the same number of teeth, so the feed comes out the same for both. The carbide could handle a lot more RPM, and under those conditions, it would have a higher feed -- but as long as you are sticking to the same RPM, the same number of teeth, and the same feed per tooth, you are stuck at the same feed. Enjoy, DoN. -- Email: | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
Speed and feed confusion
Thanks Don, Steve and Charles,
OK, I got it. Definitely a senior moment there. Once I became fixated on the expectation to see a difference, logic left the building. Dave |
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