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HELP - Computine Horizontal Mill Table Feed

Apostle

Plastic
Joined
Apr 20, 2009
Location
Charlottesville, VA
Hi Guys,

I am stumped! I have a Sheldon No. 0 Horizontal Milling Machine on its way to my shop. While I'm pretty familiar with many machine shop operations (lathe, vert milling, welding, etc), a horizontal mill is new to me. I've had very little experience running one.

I've been readying myself for making chips shortly after its arrival. I"m having a problem in determining how to compute a reasonable table feed rate.

This Sheldon mill has x-axis feed rates of: 0.0011, 0.0023, 0.0046 and 0.0094 inches per spindle revolution. To compute the proper feed, the following formulas are provided in handbooks:

IPR (inches per revolution) = N (# cutter teeth) x F (cutter feed rate per tooth, a table look up value)

Now, RPM's are computed as: [CS (cutter speed, table lookup)x(4)]/D (diameter of cutter)

Finding the table feed value for a 4" side-tooth HSS cutter with 72 teeth, cutting a low to medium carbon steel (CS~80) yields a spindle RPM of 75 RPM. The "F," or feed in inches per tooth from the table look-up is a range from 0.002" - 0.007". Using a middle value of say 0.004", the math yields a table feed rate of 0.290 inches per spindle revolution. That represents a rate of over 30x my highest feed of 0.0094"/revolution.

I'm missing something BIG here ..these forumlas do not take into accoute the depth of cut or the HP rating of the motor. I'm stumped and I cannot find the answer. Is it possible these comps are made for a HUGE mill with a "MUCHO-HP" motor, unlike my tiny 1 hp motor (3 phase motor driven from a VFD) ??

Any and all comments are welcomed..

Regards,

Puzzled Mike in Virginia
mike at w4xn dot com
 

johnoder

Diamond
Joined
Jul 16, 2004
Location
Houston, TX USA
Say the Sheldon was making 200 RPM and the feed was on the .0094 setting

Multiplication gets you 1.88 inches per minute

If the cutter had 12 teeth, that would be a chip load of .00078" per tooth

A two flute end mill would have a chip load of .0047, which gives you the idea that it won't feed multi tooth cutters nearly fast enough

Yes, it feeds slow - so you work around it, or make it different
 

Apostle

Plastic
Joined
Apr 20, 2009
Location
Charlottesville, VA
Say the Sheldon was making 200 RPM and the feed was on the .0094 setting

Multiplication gets you 1.88 inches per minute

If the cutter had 12 teeth, that would be a chip load of .00078" per tooth

A two flute end mill would have a chip load of .0047, which gives you the idea that it won't feed multi tooth cutters nearly fast enough

Yes, it feeds slow - so you work around it, or make it different

Thanks for your reply John. I'm thinking that learning the proper cutting feed will be a matter of "cutting and listening."

Mike
 

Nmbmxer

Hot Rolled
Joined
Jun 22, 2008
Location
VA
Those seem like fairly common feed/rev numbers for 1,2 & 4 flute endmills. Seems kind of short sighted for a horizontal mill which commonly uses large cutters.
 

matt_isserstedt

Diamond
Joined
Dec 15, 2003
Location
suburbs of Ann Arbor, MI, USA
My experience is a multi-toothed cutter (with multiple edges engaged at the same time) puts a lot more load on everything from workpiece to machine. Start with hand feeding to see how things react. Then start with the slowest feed.

If you have a home shop and the longevity of edge tools is of prime importance, I'd just leave it there. If you have a production job you might be more inclined to speed it up. A trigger spray bottle set to "stream" makes a handy dispenser for water based machining coolants if you are so inclined, a chip brush is good for oils.
 

JST

Diamond
Joined
Jun 16, 2001
Location
St Louis
Ok on the more load, but it seems that horizontal mills, even small ones, do better with a fairly aggressive feed per tooth, than they do trying to dust off bits. And the cutters do better cutting, and not rubbing as they dust off a tenth per tooth.

Cutters commonly have 12 to 25 teeth, so I'd expect the feed to have some settings with a faster feed than you describe. Are you certain those are the the only ones and there is no other range? The UK reference site mentions feeds up to 0.032 oer rev.
 








 
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