Horizontal Mill Spindle Direction?

Discussion on all milling machines vertical & horizontal, including but not limited to Bridgeports, Hardinge, South Bend, Clausing, Van Norman, including imports.

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Re: Horizontal Mill Spindle Direction?

Post by tetramachine » Sun Oct 29, 2017 12:34 pm

I am not sure of the question, Is it the nut is loosening? or you want to know how it would loosen.
On my arbors the key runs almost the full length of the arbor, each spacer is wiped clean of chips, and the nut run against a spacer that is keyed. Not had any loosening issue.
Since the rpm is low with an arbor mill, the startup momentem torque is very low. My surface grinder no key, 1/2 Left hand thread spindle nut must be tight, as zero to 3600rpm in a couple tenths of a second is big torque.
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Re: Horizontal Mill Spindle Direction?

Post by wlw-19958 » Sun Oct 29, 2017 1:32 pm

Hi There,
earlgo wrote:I am certainly missing something here. This is my setup for a wide milling cutter turning CCW (facing the spindle) with a conventional cut. The cutter is keyed to the arbor and the nut is RH thread pulled up tight. wide mill.JPGcutting the key.JPG I am having difficulty figuring out how the nut is going to become loose. Please explain this to me.
In your example, the CCW IS the correct rotation for a
RH threaded arbor.

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Re: Horizontal Mill Spindle Direction?

Post by Harold_V » Sun Oct 29, 2017 3:49 pm

wlw-19958 wrote:Hi There,
Harold_V wrote:
wlw-19958 wrote:Although horizontal milling cutters can be mounted on the arbor either way, the direction is dependent on the threads on the arbor. You want the cutting forces to tighten the nut and not loosen it. That means, right-hand threaded arbors should be used for right-hand
cutting (counter-clockwise) and vise-versa for left-hand.
True to point, but large cutters are generally mounted with a driving key, so they can be operated in both directions, regardless of the hand of the arbor nut thread. There are times when one simply must run the opposite direction.
Unless it is necessary for a cutter to run in a particular
direction, I think it is better to err on the side that will
tighten the nut, rather than loosen it. There is nothing
more frustrating that ruining a piece of work because the
nut loosened and the cutter started to wobble (even with
a driving key).
I agree. I made mention simply because there are times when one may not have the option of observing the preferred shop practice. The risk, in this case, is exceedingly small, due to the key preventing the cutter from loosening the nut. For large cutters, it's a mistake to hope for nut pressure, alone, to drive the cutter, anyway.

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Re: Horizontal Mill Spindle Direction?

Post by Jaxian » Sat Nov 04, 2017 3:06 am

Just an observation given there was a picture of a slab mill posted earlier. According to the Cincinnati "Treatise on Milling" when using a helical "slab" type cutter you should always make sure it is set up so that when it is spinning it is trying to "pull" itself back into the column and not trying to move in the direction of operator. Compressing the spacer stack and putting the force into the column makes for a MUCH more rigid cutting action then if it is trying to pull itself outward taking tension off the spacer stack on the column side and putting the force into the arbor support and bushings at the operator side of the Z (spindle) axis which is not remotely as rigid and stable.

Just something to keep in mind as my stack of slab mills have both right and left hand twists and it pays to pay attention and do your setups accordingly.

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Re: Horizontal Mill Spindle Direction?

Post by earlgo » Sat Nov 04, 2017 8:19 am

Jaxian: Thanks for the info on slab mills and the proper orientation. This will inspire me to finally put the reversing switch on the mill motor. Many thanks.
My dad had a copy of the Cincinnati milling book and somehow it escaped me in a fit of foolishness.
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Re: Horizontal Mill Spindle Direction?

Post by Profkanz » Mon Dec 04, 2017 9:40 am

With cutters that have straight or alternating angle teeth the spindle direction depends on which way the cutter is mounted.

With cutters that have the teeth at an angle or helix, the cutter is mounted so that the angle or helix transfers the force of the helix back towards the column of the machine and the spindle direction is then determined by the correct rotation for the cutter.

We always taught that on any mill there is really no forward or reverse, but only CW and CCW and these are determined by the cutter. There are left hand end mills for vertical milling which make this true for vertical mills as well.

The FWD/REV issue is compounded by switches which have the buttons labeled that way and is further complicated by reversing the vertical mill spindle when changing from high to low speed range and back again for different operations.

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