# Question for Atlas Horizontal Mill Owners



## JPMacG (Jan 5, 2022)

To those of you who have used an Atlas horizontal milling machine...   What is your technique for loosening the arbor clamp nut?  I mean the big nut that holds the cutter and spacers tight on the arbor.  I loosen it while the arbor is mounted on the machine.  But in order for the arbor's morse taper not to slip in the spindle socket I have to tighten the draw rod so tight that the morse taper then becomes very difficult to remove.


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## Bi11Hudson (Jan 5, 2022)

I use a lead hammer around the shop for most everything. Light taps to adjust, heavy slugs to seriously move. It can be used or a scrap of 2X4 and a steel hammer if you don't like lead. Anything that won't bounce. . . For the MF-C mill, the process is the same as for the lathe and other vertical machine quills. I loosten a half rotation to one full turn and tap with the lead hammer. Then back it out by hand. Most times a 3/8-16, sometimes a 10mm. When the metric drawbolt is used it isn't left in the machine. I had acquired a piece of unplated all-thread, it rusts if I look funny at it even when oily. I use some odd setups making my models so some of my gizmos aren't "approved" for general machinist work. Tiny gears the size of my thumbnail don't need much clearance room.

Rereading the OP, the nut on the end of the spindle is just to hold the tooling tight. It's never an issue with the MT-2 on the spindle. I don't understand the jump from one end to the other. I loosten and tighten the nut with an open end wrench and never use the hammer there. There are occasions, very rare but there, when I remove the spindle with tooling intact. And I'm sure someone with two or more spindles might mount tooling on a second one in advance of a move. I only have one spindle, a 1 inch, but a number of MT-2 tool holders and gear cutter mounts. Things get swapped around some.

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## JPMacG (Jan 5, 2022)

Thanks Bill. 

What prevents the arbor from rotating when you use your open end wrench to loosen the nut?  If not the morse taper, then what?


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## brandon428 (Jan 5, 2022)

I don't understand the relationship between the two.  The big nut on the end holds the cutters and spacers in place on the arbor.

The morse taper on the arbor is keeping the arbor held in the spindle.  The drawbar at the back keeps the arbor snug.  The pins on the arbor driver are insurance against the arbor spinning inside the spindle.

My procedure for installing/removing the nut on the end is engaging the back gear and using a big crescent wrench. I give it a firm snug on and off, never have problems.  I do have problems removing my arbor from the spindle, meaning I have to hit it several times.  I use anti-seize on the morse taper which seems to help, but it still never "taps out" for me like the manual says.


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## JPMacG (Jan 5, 2022)

So you are getting enough holding power from your morse taper to allow you to unscrew the nut.   My problem is that when I try to unscrew the nut the morse taper slips.   And the arbor driver does not help - it just unscrews.


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## brandon428 (Jan 5, 2022)

Oh definitely.  I've never had problems with the morse taper holding.

But stepping back.  If it's spinning, it sounds like you don't have any pins on your arbor driver.  Those should prevent that if nothing else.


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## JPMacG (Jan 5, 2022)

I have pins, but unscrewing the nut also unscrews the arbor driver - they are both right-hand threads.


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## Bi11Hudson (Jan 5, 2022)

The pins on an OEM arbor were put there as a "drive" clamp. They also serve to secure the  arbor for tightening and loosening the clamping nut. A retrofit arbor may or may not have them included. An OEM arbor may have had them removed for some reason. As with lathes, engaging the back gears to lock the shaft is a bad idea. Broken teeth is a difficult repair on the MF-C. The nut should be loose enough to tighten by hand. The last little jerk with a wrench is just to make sure it stays where it was set. A key in the tooling does the driving. Same for loosening it, a wrench to break it loose then remove by hand.

From the above post while I was writing, it sounds like the nut is too tight. It should spin on by hand and the wrench just to make sure it stays. And the same for removing it.

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## brandon428 (Jan 5, 2022)

I'm just using the back gear to make it snug, not a hard turn of the wrench.

It sounds like you're not tightening your arbor driver enough though.  You should need a spanner wrench to tighten and loosen it.  It shouldn't come off when you turn the nut.


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## Bi11Hudson (Jan 5, 2022)

When I tighten either end, the drawbar or the arbor nut, if I cause the spindle to rotate it's tight enough. Most times the machine is in back gear because I can see what I'm doing better. That and the tension on the belts gets things pretty tight.

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## JPMacG (Jan 5, 2022)

I am likely tightening the arbor nut too much.  When removing the nut I could use a spanner wrench on the arbor driver to resist rotation but the spanner wrench I have is only about 4 inches long - not enough leverage.

My morse taper socket has always been problematic.  If I don't tighten the draw bar snug it will slip, but if I do tighten the draw bar that much then it becomes difficult to remove - taking much more than a few taps with a lead mallet.  I suppose I should get a MT2 reamer and try to dress the socket.


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## JPMacG (Jan 5, 2022)

Bi11Hudson said:


> The pins on an OEM arbor were put there as a "drive" clamp. They also serve to secure the  arbor for tightening and loosening the clamping nut. A retrofit arbor may or may not have them included. An OEM arbor may have had them removed for some reason. As with lathes, engaging the back gears to lock the shaft is a bad idea. Broken teeth is a difficult repair on the MF-C. The nut should be loose enough to tighten by hand. The last little jerk with a wrench is just to make sure it stays where it was set. A key in the tooling does the driving. Same for loosening it, a wrench to break it loose then remove by hand.
> 
> From the above post while I was writing, it sounds like the nut is too tight. It should spin on by hand and the wrench just to make sure it stays. And the same for removing it.
> 
> .



My arbor does not have pins - it has half-round sockets that engage with the pins on the arbor driver.  This agrees with the Atlas OEM drawings.  I made the arbor driver following an Atlas drawing.


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## Bi11Hudson (Jan 5, 2022)

It has been a while since I have swapped out the arbor for a tool holder. My memory isn't too pretty good either. The locations of the notches and the pins falls into that memory hole. Which ever one has which, the pins fit into the notches and hold things tight.

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## JPMacG (Jan 5, 2022)

Thinking about this some more, I stumbled on an obvious solution - so obvious that now I feel stupid.  The spanner wrench will lock into the base casting very nicely.  works like a charm.


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## Dave Smith (Jan 5, 2022)

JPMacG said:


> Thanks Bill.
> 
> What prevents the arbor from rotating when you use your open end wrench to loosen the nut?  If not the morse taper, then what?


a spanner wrench on the front spindle collar will keep the arbor from turning when loosening the nut.
Dave


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## Dave Smith (Jan 5, 2022)

JPMacG said:


> Thinking about this some more, I stumbled on an obvious solution - so obvious that now I feel stupid.  The spanner wrench will lock into the base casting very nicely.  works like a charm.


in your picture, the hole in the spindle arbor driver is for the spanner wrench to be used in, not the pins. Dave


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## Bi11Hudson (Jan 5, 2022)

Sometimes asking a question will put things in a different light and you can see better what you're asking about. You're lucky that you thought of your solution before someone else did.

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## JPMacG (Jan 5, 2022)

The photo shows a spanner wrench engaging the rear hole in the arbor driver.


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## Dave Smith (Jan 5, 2022)

JPMacG said:


> The photo shows a spanner wrench engaging the rear hole in the arbor driver.


Oh, my arbor driver only has one hole for spanner wrench.
Dave


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## JPMacG (Jan 5, 2022)

I put two in, 180 degrees apart.   Even with two they are always in the wrong place.


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## Firebrick43 (Jan 5, 2022)

Doesnt your arbors have wrench flats right before the support journal?


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## Dave Smith (Jan 5, 2022)

Firebrick43 said:


> Doesnt your arbors have wrench flats right before the support journal?


not mine.
Dave


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## 577 stu (Feb 6, 2022)

Hello -new guy here, When ever I deal with shafts or arbors and round things a leather or rubber strap wrench will tame
the nasty round things


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