I'm asking about the cutting portion. For turning 4:1 L/D seems to be normal for steel.
An endmill being seriously relieved would seem to to have a lower L/D ratio.
Cutting plastic vs aluminum vs steel would seem to have varying optimal L/D ratio's.
Being cheap, I sharpen even the small stuff on the end using a fixture on a surface grinder to add to the equation.
I'll sit back now and read. I don't have an opinion, I'd like to read yours and the thinking supporting it.
Wes
-- "Additionally as a security officer, I carry a gun to protect government officials but my life isn't worth protecting at home in their eyes." Dick Anthony Heller
(Something malfunctioned there. Good thing I save whatever I write.)
I have a fairly light Clausing mill that doesn't like to cut deeper than about 0.050" in steel per pass. The flip side is that it doesn't mind long end mills because I know better than to hog out a lot of metal with them.
Last night I cut two slots in steel, 3/8" wide by 1" deep, using a long 4-flute endmill with 1-3/4" cutting edges. The end mill measures
0.376" across. and so do the slots; the end mill is a light drag fit in them. I couldn't ask for more.
I roughed the slots with plunge cuts with an undersized reground end mill first. Since I resharpen them on a surface grinder too, I try to remove most of the metal with the more easily sharpened end. The one I use most for milling flat surfaces is beveled at the tips with the fixture in the 30 degree back-relief position. The bevel seems to keep them sharp much longer. It was a tip in the Cincinnati Milling Machine book from Lindsay.
L/D of 3:1 or 4:1 are fine most of the time. I've used longer center- cutting ones to drill interrupted holes and mill out deep electronics enclosures. They don't start well in a drill chuck, even on a milling machine.
I had to use one to drill through the slotted parts mentioned above, which are eccentric cams, because the center hole to locate them in the mill interfered with drilling the 3/8" axle hole 0.062" off center. Good planning! I found the largest centered circle that cleared the axle hole on the CAD drawing and drilled through the center slightly smaller, to give the end mill some center clearance and let the chips fall out.
Don't sweat the optimum length. Get an assortment with several duplicates of the common sizes and a few longer 4-flute center-cutting ones, which you can feed gently if necessary. When you regrind them only two flutes need to cut to the center. You can Dremel the other two back a ways for clearance.
It's always nice to define an abreviation the first time it appears in a text. L/D to me will always mean lift over drag when I see it by its self. I guess you mean "length over diameter" but have no idea how that relates to milling. ...lew...
The longer an endmill is in relation to the diameter , the more potential flex under load . I don't think I'm pushing mine hard enough to worry about that . Yet , but there's always tomorrow .
In mechanical engineering, L/D is used in column formulas. As it increases the stiffness of the column becomes more important than its compressive strength.
I've been collecting a library of on-line aircraft data, some of which is surprising. For instance L/D for that classic powered brick the F-4 Phantom is 8.5.
That's from Wiki. I don't know about fuel load or stores, or if it refers to thrust required for normal flight or gliding unpowered with the engines windmilling and everything jettisoned. It was discussed in rec.aviation.military a while ago and surprisingly some fighters will glide further than a Cessna. Airliner L/Ds are around 15. Apparently fighter jets' reputation for falling out of the sky comes from a best glide speed around 200Kts.
I remember flying over a frozen lake. IP telling my what am I going to do if my engine goes out. Terrain in area sucks. Felt pretty stupid for not figuring out circling until low enough was the answer.
Wes
-- "Additionally as a security officer, I carry a gun to protect government officials but my life isn't worth protecting at home in their eyes." Dick Anthony Heller
Help me out, what is the difference between a forward slip and a side slip?
I remember being taught to cross control rudder and aileron to deal with a too high approach. IIRC, that left me flying down along centerline of runway with nose pointed off centerline and wings banked.
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