Adjusting 10EE Crossfeed Screw Backlash

[Cal Haines]

This is a carry-over from a thread on taper attachments:
http://www.practicalmachinist.com/vb/monarch-lathes/taper-attachment-10ee-171651/index2.html
Since this is a bit off topic from the original post I'm starting another thread.

I recall reading about adjusting the nut on the crossfeed but I don't think there was very much detail on exactly how to do it. I worked through the process today and am writing it up so that the next guy will have an easier time with it.

Here's a photo of the crossfeed ACME nut from my '43 round-dial:


To the right of the ACME nut is the drawbar clamp nut*, basically a T-nut with a radius machined in the bottom where it sits astride the crossfeed screw. The three fasteners associated with the ACME nut and the clamp nut are (left to right): crossfeed nut capscrew, crossfeed nut adjusting pin and crossfeed clamp bolt. These are my terms; the manual only names the pin, and I find its name confusing.

Here's a photo of the cross-slide with the compound removed and the three fasteners visible at the back of the top slide:


The basic procedure is to use the adjusting pin to push the front (operators end) of the ACME nut down, while holding the rear of the ACME nut up against the bottom of the cross-slide with the capscrew. This tips it down (rotating it clockwise in the first photo) to help compensate for wear of the nut. The procedure can be used to reduce or eliminate backlash (assuming that the screw itself is not too badly worn).

Here is a step-by-step procedure for adjusting the crossfeed backlash:

1. Move the cross-slide to the extreme front (operator end) position. Backlash will typically be less at the ends of the screw.
2. Tighten the taper attachment drawbar clamp and crossfeed clamp bolt.
3. Loosen the crossfeed nut capscrew.
4. Back the crossfeed nut adjusting pin out several turns.
   NOTE: Never attempt of turn the adjusting pin without loosening the capscrew.
   If the pin does not turn easily, remove it and chase the threads with a tap and die.
5. Draw up the capscrew. (This pulls the ACME nut up against the bottom of the cross-slide.)
6. Turn the adjusting pin in until it bottoms out, don't tighten.
7. Turn the cross-slide dial and note the amount of backlash.
8. Back off the capscrew one turn (less when repeating the adjustment).
9. Turn the adjusting pin in. Start with 1/4 turn, use more or less, as necessary on repeat. (This step pushes the forward end of the nut down.)
10. Draw up the capscrew and snug it up. (This pulls the rear of the nut back into position.)
11. Verify that the rear of the nut is in contact with the bottom of the slide. This will only be possible on round-dial machines, due the to longer slide on square-dial machines.
12. Check backlash and repeat steps 9 to 12 as required.
13. Release crossfeed clamp nut.
14. Check backlash every inch or two across the length of the axis, repeating steps 9-12 to loosen the nut as needed, clamping the cross-slide at each adjustment.

My machine had about 0.060" backlash at the front end of travel, step 7. 3/8 of turn (total) was required at step 9 to reduce the backlash at that position to 0.005". About 0.003" backlash was due to backlash in the telescoping leadscrew keyway.

My machine has a one-piece ACME nut. The 1942 manual shows a two-piece nut, held together by four bolts, that uses shims to adjust for wear. This procedure would probably work for a two-piece nut as well.

Cal

* The clamp nut is typically only present in machines with a taper attachment and may not be present in newer (square-dial) machines with taper attachments. It's not clear how one locks the cross-slide without one. All of the cross-slides seem to have the third hole for the clamp nut and bolt.

 

[G1K]

My '42 round dial does not have a taper attachment and according the the paperwork from Monarch did not ship with one. I also do not have the crossfeed clamp or bolt, though there is a hole for one there. I have a one piece nut also.

R

 

[The real Leigh]

The clamp nut is typically only present in machines with a taper attachment and may not be present in newer (square-dial) machines with taper attachments.

My '57 square dial with TA has the three screws as shown above.

- Leigh

 

[tohopka74]

Just reading this months later. My '42 has a one piece nut, but someone cut it partway through and tapped it lengthwise for small socket head cap screws. By removing the dust cover at the back of the cross feed I can just get at these capscrews with a long allen wrench and squeeze the nut together, thus tightening the nut where the cut is, and squeezing it onto the threads of the crossfeed screw. It's a bit cobbed, but it does work. I also have the adjustment screws as shone above, in addition to this little "aftermarket" feature. It's a way to go if you can't adjust the nut any other way!

 

[donie]

Monarch seems to have not provided an easy way to oil the cross feed screw.
I used a ball endmill, sunk it down a little into the head of the taper locking bolt, drilled a small hole on through the bolt and made a little brass cap to keep chips out.
So, I just run the crosslide back and forth a time or two and drip oil into the taper locking bolt.

http://s170.photobucket.com/albums/u265/donsmonarch10ee/?action=view&current=DSC00440.jpg

 

[rklopp]

At the risk of being branded a heretic, doesn't Monarch's method of restraining the nut and adjusting it's backlash seem a bit Disneyfied (i.e., Mickey-Mouse)?

 

[daryl bane]

I agree totally, but I guess it works and probably a traditional method of design. I would like to know how Schaublin, Rivett, Hardinge does it? Anybody?

 

[donie]

My thought on the nut adjust method for the EE, is its good enough, that is, for the life of the screw. When a screw is worn, more complicated nut adjustment methods dont do much good.
The L&S Powerturn had a two piece nut with a screw to wedge them apart.
The Hardinge chucker has one of the best I have seen. The nuts are threaded into a hole fixed to the crosslide, the outer adjustable nut is adjusted for backlash.
But, if the screw is worn, its not any better then the Monarch EEs tilt method.

 

[rimcanyon]

I think the Monarch method is, when the backlash is out of spec, buy new parts. Some of the used parts I have seen that came out of Mare Island or other U.S. Government rebuild facilities were hardly worn at all, e.g. leadscrews & nuts with .010" backlash.

-Dave

 

[DaveE907]

Mechanically the Monarch method makes little sense and is a relatively short term cure. It's one of those "what were they thinking" details that confound on a machine so well designed in other respects.

Visualize a loose nut tilted on its mated thread and determine the contact areas between the male and female threads: they're small and localized so lead to accelerated wear and chasing one's tail.

Split nuts on the other hand maintain axial alighment of the mated threads and one half of the nut fully bears on one flank of the male thread while the other half bears fully on the opposing flank. The bearing area is more than that of a tilted nut so the assembly wears better for a more stable adjustment. It's considerably more expensive to manufacture however.

Fortunately my nut and screw have .003 backlash without adjustment, when the need for adjustment arrives it will be fit with a split nut arrangement similar to those found on many other quality machines.

 

[donie]

On the Hardinge and L&S Powerturn with two piece nuts, the manual calls for no tighter then .002 dial grads on backlash. Most likely any tighter will squeeze oil off the screws and increase wear.
The Powerturn I have needs that for the tracer to work properly, the Hardinge HC for drilling and ect.
The Monarch EE, having one of the smoothest acting crosslide I have encountered, I just dont see it being any problem or having any lack of accuracy.

 

[jayhawkman]

Monarch crossfeed nut

I make these nuts and sell them on ebay for $55. I can give forum members a discount and sell them for $45 including shipping. If you have any questions please give me a call at 913 636 6107 Thanks Mike

 

[Peter Miles]

Mike, what has been your experience of the condition of the leadscrew when someone decides it is time to change the nut?

 

[jayhawkman]

leadscrew

The nut is designed to fail. If the threads on the leadscrew are worn more then 20% I think they should be replaced. I also rebuild the leadscrew if needed. PM or call if you have any questions. Thanks Mike

 

[kvom01]

Slightly off-topic, but is the crossfeed clamp screw intended as a general crossfeed lock, or just for allowing the TA to operate?

I have never seen any real creep of the crossfeed when turning, so perhaps a moot point.

 

[Jim McIntyre]

...The basic procedure is to use the adjusting pin to push the front (operators end) of the ACME nut down, while holding the rear of the ACME nut up against the bottom of the cross-slide with the capscrew....

First off, many thanks for the well written explanation, Cal.

Unfortunately, when I gave it a try on my machine, a 1962 Gov't surplus square dial it didn't work out so well. It had about .025 of backlash. I couldn't get the backlash adjusted lower than .020. If I went any lower, the cross slide became pretty hard to crank. The backlash remains pretty constant through the full travel of the cross slide.

Any ideas?

 

[DaveE907]

Is it .050 on the dial and .025 backlash? Or is it .025 on the dial and .0125 backlash? These terms are often confusing when strangers get together such as on this forum.

As the backlash is "pretty constant through the full travel of the cross slide" your screw is likely still servicable. If you have doubts about the screw measure and chart its pitch diameter along its length.

The easiest approach is to try a new nut, they wear out faster than the hardened and ground screw. You can make one or buy one, your choice.

One source is Mike in post #12 above. Two others are Miller Machine and Monarch.

http://www.millermachineandfabrication.com/default.htm

http://www.monarchlathes.thomaswebs.net/

 

[Jim McIntyre]

Is it .050 on the dial and .025 backlash? Or is it .025 on the dial and .0125 backlash?

It's .025 on the dial.

Sounds like some others have come to the same conclusion - this approach to adjusting is not good. In my case, tilting the nut just adds too much drag before it takes up the backlash.

Still a good thread - taught me how to oil the lead screw...

 

[rklopp]

On my machine, the hole for the "adjusting" pin goes through to the nut threads. Driving the pin in to try to tilt the nut just jams the pin into the side of the cross-feed screw. Fortunately, I saw this before trying to adjust the backlash. By the way, the nut seems to be OEM.

 

[Cal Haines]

On my machine, the hole for the "adjusting" pin goes through to the nut threads. Driving the pin in to try to tilt the nut just jams the pin into the side of the cross-feed screw. Fortunately, I saw this before trying to adjust the backlash. By the way, the nut seems to be OEM.

Interesting. I wonder if someone modified it, not knowing what the purpose of the socket in the nut was? Neither one of the holes in mine are through holes. The socket for the pin has a spherical bottom and the pin is a fairly tight fit.

Cal