adjusting half nuts on a 10EE
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    Default adjusting half nuts on a 10EE

    I need to adjust the half nuts on the 49 10EE. Currently they are too tight, or one of them is. When the carriage is moving to the right it makes some noise. Monarch did not make it easy - the saddle has to come off to get access to the top half nut's lock nut, and of course the apron needs to be supported from the bottom. Anybody have any pointers on how to do it? How much clearance should I aim for when the half nuts are engaged?

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    I don't have any particular advice on the adjustment. But I'm curious how's the alignment of lead screw and such through apron ?

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    I have a couple of these in my shop and there's no way to adjust the half nuts without separating the apron from the carriage. What I do is bring the whole assembly to the very end of the lathe, then take my bolts out there. if you have a hoist, eyebolts in the carriage makes it easy. If you don't have a hoist, this job is more difficult. Above all, make sure you properly hold the apron up with some boards and make SURE you support your lead screw. I made up a support out of 2x4's that wedge in between the lead screw and bar. Once separated, run the apron off the end just far enough to get to the half nuts. There is an adjustment for the half nuts and since you're dragging against the lead screw, just open the gap adjustment a hair till you're not touching. This will eat up the half nut quick and i can tell you from experience that making a new set is not fun. By the way, if you make some, i've been making them from silicon bronze and they hold up well in all of my machines and we thread on all of them everyday.

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    Quote Originally Posted by rimcanyon View Post
    I need to adjust the half nuts on the 49 10EE. Currently they are too tight, or one of them is. When the carriage is moving to the right it makes some noise. Monarch did not make it easy - the saddle has to come off to get access to the top half nut's lock nut, and of course the apron needs to be supported from the bottom. Anybody have any pointers on how to do it? How much clearance should I aim for when the half nuts are engaged?
    First.. see if the top one is "tight" because the whole carriage has worn and dropped. My '42 isn't bad. My '44 was dragging so badly it "sang" as it was traversed from dragging on the guts.

    Dunno if round-dial parts are the same as your '49 or not, but I have a decent leadscrew and a still usable set of half-nuts from a '41 part-out.

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    Bamabo, thanks for the suggestions. Your process is similar to what I have in mind. This machine never had a threading capability, so the gearbox, lead screw and half nuts are all good used parts put together for the first time. And the lathe has a turret, so the saddle has about 12" of travel, not 20" like a regular toolroom machine.

    I am thinking that when the half nuts are engaged, there should be some clearance. i.e. using the handwheel I should be able to move the apron maybe.005". Right now there is no measurable clearance when the half nuts are engaged. Also, If I set up an indicator on the lead screw I should be able to check vertical alignment and clearance with the half nuts engaged. At least that is my plan. I will let you know how it goes.

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    Quote Originally Posted by rimcanyon View Post
    If I set up an indicator on the lead screw I should be able to check vertical alignment and clearance with the half nuts engaged. At least that is my plan. I will let you know how it goes.
    That will tell the tale. Stiff as it is, the lead screw will be displaced.

    The diff between:

    - the '42, with most of the wear in the center 1/3 of travel (the saddle doesn't contact the front flat at either 1/3 end..).. which does not YET drag on lead screw or surfacing drive pick-off.

    and

    - the '44 . which has near-as-dammit the same wear pattern end-to-end and DOES "sing" as it drags Bronze over leadscrew and surfacing shaft pick-off (or did before it got shimmed)..

    Is/was only about 5 thou out of the overall larger-yet drop.

    So there WAS some clearance, even brand-new, in anticipation of a reasonable wear-budget.

    Monarch's plan, of course, was to sell a NEW lathe ever' now and then?

    They didn't intend theirs to last ALL of "forever." Just longer than the competition.


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    Quote Originally Posted by rimcanyon View Post
    I need to adjust the half nuts on the 49 10EE. Currently they are too tight, or one of them is. When the carriage is moving to the right it makes some noise. Monarch did not make it easy - the saddle has to come off to get access to the top half nut's lock nut, and of course the apron needs to be supported from the bottom. Anybody have any pointers on how to do it? How much clearance should I aim for when the half nuts are engaged?
    Dave,

    I would start by making sure that the tailstock end bracket for the leadscrew and feed-rod is at the right height. You can do that by unbolting it and pulling the dowels, then run the carriage to the right and see if the leadscrew is still binding. If you used the mounting location for the original bracket, it may not be at the right height.

    If the bracket is out of place, you can oversize the bolt holes to allow it to move into the right place. You'll want to drill out the dowel pin holes in the bracket 1/64" under the new (larger) dowel pin size while you have the bracket off, then use it as a drill jig to match drill the holes in the bed. Finish by reaming for the new dowels.

    It's nice if the leadscrew is parallel to the ways, but not as critical as the position of bracket. There were some quick-and-dirty rebuilds done that consisted of machining down the bottom of the saddle, then dropping the right bracket to account for the amount of material removed from the saddle. This resulted in the leadscrew and feed-rod running down hill as you move right. My machine, as well as others, had this done. My bracket was dropped about 0.040". It works because when the carriage is all the way to the left, the half-nuts and feed worm are close to the middle and thus only have to deflect the rods 0.020". Not ideal, but it works.

    Cal

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    Cal, I am using the original lead screw/feed rod bracket on the lathe. It had a plug where the lead screw attaches, but it was fully machined for a leadscrew. So alignment of the leadscrew is fine. I just needed to adjust the half nuts so that they were centered properly and had the right clearance. I worked on it today and got it pretty close. I set up an indicator on the leadscrew and blocked the apron with some 2x4's and shims before removing the saddle. The half nuts were adjusted so that when they are closed, the leadscrew does not deflect. And when I use a pry bar to force the leadscrew up or down, the clearance is quite minimal. There is very little side to side clearance, and there is no noise from the half nuts when engaged and running in each direction, so I will declare done.

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