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timh
11-04-2005, 01:15 PM
Hi was reading one of the other post were you said a horizonal mill should run 50 rpm or under why is that?

J Tiers
11-04-2005, 02:01 PM
Tougher steel, tool steels.... and cutters at 4" or above diameter....

Figure the RPM necessary for the recommended SFM, and thats where you end up.


Ignore it, and you burn up cutters.

[This message has been edited by J Tiers (edited 11-04-2005).]

jkilroy
11-04-2005, 02:13 PM
Mr. Tiers offers top notch advice, also you have to consider the number of teeth on the cutter. Most horizontal milling cutters have a lot of cutting edges. The 5" Niagra I am holding in my hand has 26 teeth. With that many teeth you can still remove a LOT of metal in a short time due to the fact that you have to really feed these cutters to maintain proper chip loading. Increasing the RPM higher will require a much faster feed, which will produce a metal removal rate that is probably beyond the capacity of the spindle motor.

But you have got to love horizontals. The first time you see a big Cincy chew into a slab with a 5 cutter stack on the arbor you just have to saw WOW.

Evan
11-04-2005, 02:40 PM
http://vts.bc.ca/pics/hmill1.jpg

kap pullen
11-04-2005, 03:35 PM
Like J tiers said,

It is the surface speed that wastes your cutters.
A 6" side cutter on mild steel at 60 fpm = 40 rpm.

6 x 3.1416 = 18.8" per revolution = 1.5feet divided into 60feet = 40 rpm.

More teeth dosen't mean you can jack the rpm up, but up the feed.

Maybe things are different now?

kap

Mcgyver
11-04-2005, 03:47 PM
<font face="Verdana, Arial" size="2">Originally posted by jkilroy:
But you have got to love horizontals. The first time you see a big Cincy chew into a slab with a 5 cutter stack on the arbor you just have to saw WOW.

</font>

I do and wish I had one. maybe now with a T&C grinder that'll change, never really considered getting before because of the cost of the cutters, but now that I can resharpen it'll be cheap

I always think of spindle speed as matching the cutting speed (sfpm) constraint and feed matching the chip load constraint - theoretically the spindle goes at an optimal fpm, the feed is set, based on # teeth + rpm to optimal chip per tooth load

J Tiers
11-04-2005, 07:01 PM
I mentioned the speed think because a lot of smaller mills seem to have high speeds.

My little Lewis was "pulleyed" for about 125 rpm when I got it.... I learned quickly that was not good.... want a pic of the (now) bad cutters?

And Grizzly http://bbs.homeshopmachinist.net//rolleyes.gif offered a combo vert/horiz unit with R8 (!) arbor socket, AND a slowest speed in , IIRC , the area of 100 to 150 RPM. Two big strikes against.....


Feed.... yep, books say, and experience confirms, slow the cutter and jack up the feed. works pretty well, and does not burn cutters. Might chip them, if you get nutty with it.

There is a perfect sound of horiz mills.... a nice RRRRRRRRRRRrrrrrrrrrr..... RRRRRRRRRrrrrr.... as the very slightly offcenter cutter (they always are) munches thru metal. No banging, no squeaking.... kinda quiet, actually.


[This message has been edited by J Tiers (edited 11-04-2005).]