Speed kills, feed goes. At one point recommended SFM for HSS started at 30, and you would get chewed out for wearing out endmills by going faster. I’m not sure about the 100plus SFM without coolant-blast. Safe to start at 60 in mild steels, dry, forget squirting Wd40, (maybe mixed with Varsol for aluminum ) the vegetable compound sprays or pastes are pretty good but inhaling the smoke is vile.
Slotting is worse case scenario for heat build up so even lower SFM is desirable, light side milling @ .030 depths or less are far less sensitive to speed so crank them up
Climb milling also increases tool life over conventional,
HSS needs coolant over lubrication, water is an excellent coolant, emulsified coolants have the added bonus of lubrication, bandsaw blades require more lubrication than endmills.
Keep everything short as possible, long series endmills need to go slower to avoid chatter, can’t be avoided.
Your 5/8 endmill should be less than 500 RPM, it looks like a long series, so less speed and play upwards with the feed, once the chatter changes to a low frequency you are flirting with overloading in heavier cuts.
In steel, the chips should not change colour with HSS, except maybe stainless which will be straw coloured, if in steel if it’s straw or getting to blue back off the speed, keep the feed.
The reason I use carbide endmills is simply the speed and longevity and my aversion to using coolants or even lubricants, unless drilling or tapping of course.
There is excellent product coming out of Korea, Japan , Germany, UK, but are expensive and geared to controlled parameters which we cannot enjoy on a open hand controlled machines.
In short, you aren’t going to hurt anything by being conservative on speed, feed “feel” becomes increasingly difficult as you go down in size ie keyways smaller than 3/16”.
Keep the setup as short and close to the spindle as practical.
Machining railroad rails is difficult, very tough and often hardened surfaces,, HSS doesn’t like it that much. Face milling with an indexable cutter requires a cautious approach until it shows it’s colours, conservative speed 200SFM maybe and work up ,same with DOC and feed, once under the skin things should go better.
Unknown steels , same thing, difficult to know if it’s high Vanadium spring steel or Moms 80s Chevette courtesy of the scrap yard melt.
Rule of thumb with indexable milling, carbide should be either dry or wet, tossing a shot of coolant on hot carbide is not advisable, keep it dry or keep it wet.
Cheers Tim
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