New to me ZX45 milling machine

[JustaDB]

umm umm I mean it was is such bad shape

Uh-huh... In that case, you'd be more than willing to part w/ it for 1/2 what you paid for it, right? I'll even pick it up. Going to be out in Saskabush this month anyways, probably w/ a moving van. And, no thx, I'd like one w/ a quill, too.

 

[Megar arc 5040dd]

Uh-huh... In that case, you'd be more than willing to part w/ it for 1/2 what you paid for it, right? I'll even pick it up. Going to be out in Saskabush this month anyways, probably w/ a moving van. And, no thx, I'd like one w/ a quill, too.

I have no choice but to keep it the other one is sold and gone. I'm sure you understand

 

[JustaDB]

I have no choice but to keep it the other one is sold and gone. I'm sure you understand

<sigh...>

 

[Megar arc 5040dd]

How much backlash should there be in the X and Y directions? This mill has these split nuts and I am not sure what the proper adjustment is. This picture was taken before the pieces were cleaned and put back together.

 

[Former Member]

How much backlash should there be in the X and Y directions? This mill has these split nuts and I am not sure what the proper adjustment is. This picture was taken before the pieces were cleaned and put back together.

View attachment 33426View attachment 33426

I believe there is mention of it in one if the threads. My approach is snug up to just before you start feeling it binding.

 

[Megar arc 5040dd]

I believe there is mention of it in one if the threads. My approach is snug up to just before you start feeling it binding.

Do I want there to be some backlash or is the goal to get rid of all of it? I've never had a machine with this adjustment before.

 

[140mower]

Do I want there to be some backlash or is the goal to get rid of all of it? I've never had a machine with this adjustment before.

I am no pro here, but I don't believe you can ever get to zero lash with a nut and screw. The best you can do is adjust for as little backlash as possible and still be able to smoothly move that axis without any binding. The condition of the screw will determine how much backlash you can take out, and wear in the screw is often localized in one or more places where the most work happens....
Hopefully my ramblings clear up more water than they muddy.....

 

[Former Member]

Ideally no backlash, unfortunately you will always have some in the system to allow freedom of movement.

Its a fine balance between, backlash in the system, ease of movement, least amount of wear inflicted.

I converted mine to CNC, so backlash has other impacts which is why I strive of as close to zero as possible, however even with larger backlashes on manual machines understand and using proper technique you can negate the impact which on CNC limits on how you approach machining.

 

[Dabbler]

Most machines have around 10 thou backlash when new. Even 15 thou would be fine. If you adjust it too close, you will just wear out the nut quicker.

 

[Susquatch]

Do I want there to be some backlash or is the goal to get rid of all of it? I've never had a machine with this adjustment before.

In machining, we learn to live with, and work with, whatever minimum we can achieve. The problem gets worse with time as parts wear more where they are most frequently used. Backlash in the worn area is usually adjusted to be equal to or greater than the wear so the parts don't bind in the low wear areas. We learn to know our machines and compensate accordingly.

 

[jcdammeyer]

In machining, we learn to live with, and work with, whatever minimum we can achieve.

My two cents as spoken by a true amateur.

When we have a manual milling machine generally the best we can do is motion in X or Y. If we need 32 degrees from X=0 we turn the part 32 degrees and then move in X. Rotary tables will do that for us for some parts.

When we need to bore a hole we use a boring tool tweaking it until it measures correctly. We have either power down feed or we turn the handle very slowing creating a smooth cut. And we lock the table to it doesn't move or get pulled away from the nut during this boring operation.

In each case we adjust the work or the direction of cut so that backlash isn't an issue. Try to do deep aggressive cuts with climb milling and you can see the cutter pull the table forward away from the driving nut by the black-lash slop. Do conventional milling and we're always loaded against the nut.

That's why threading on a lathe is never an issue from a backlash perspective because the tool is always loaded against the driving lead screw surface.

Enter CNC and the world as we knew it changes. Now with the ability to profile the path of a hole we don't bother mucking around with a boring tool. Especially if the diameter isn't super critical. But following a curved profile means the load on the lead screw changes as you follow the curve. Now backlash, taken out by the CNC software is a rapid acceleration and motion in the opposite direction meant to again put the load on the lead screw nut.

The problem is the table can still be pulled or pushing in the wrong direction and the hole is not perfectly round. Not like using a boring tool.

Then there's the issue of uneven wear on older machines. The backlash in the middle of the table is 0.021" but only 0.010" at one end and 0.012" at the other end. Unless the CAM system has the ability to profile the wear the backlash removed in the middle is correct but makes for inaccurate cuts at the end.

So @Susquatch is correct that we learn to work with the machine and tweak as we go. But if you want to automate, in the long run, ball screws are the only way.

 

[Dabbler]

So @Susquatch is correct that we learn to work with the machine and tweak as we go. But if you want to automate, in the long run, ball screws are the only way.

Very true. Ball lead screws on a manual machine requires some accommodation. If you are milling in X, for instance, it is a good practice to lock your movement in Y because of the ability of the lower friction ball screws tend to creep.

No matter what you do, skills development becomes important in doing the best job possible.

 

[Susquatch]

Do I want there to be some backlash or is the goal to get rid of all of it? I've never had a machine with this adjustment before.

I don't think we really answered your question.

If I were you, I'd measure it across its full range looking for where it is best. That will probably be at one or both of the two extreme ends of the travel. Then I'd try to get that best number down as low as I could get it without having any detectable friction. Zero is not likely at all. A few thou might still be too tight. 5 might be totally doable if the adjustment allows.

But don't go crazy on this. Just be gentle and shoot for not adding any friction. Friction equals fast wear. Better to learn to machine with whatever you can get without friction than to push for low numbers and add rapid wear.

 

[Dabbler]

Just one small modification to @Susquatch reply above. When you have found that 'sweet spot', back off the nut *another* couple of thou. This is oil clearance, and stops the nut from acting like a squeegee and stripping all the oil off the nut/leadscrew contact area. It is the oil that provides your antiwear properties.

 

[Susquatch]

When you have found that 'sweet spot', back off the nut *another* couple of thou.

Oh oh. Didn't do that on my own mill. Seems smooth as silk though. Might already have that there. Gunna take a look asap!

 

[PeterT]

The other thing to remember is that you have table locks & you should get in the habit of using them for manual machining if you want to maintain accuracy. If you are milling in X, then lock Y and vise-versa. If you are drilling or boring a hole, lock both X & Y. Because the reaction force of cutting action can similarly displace your table (which is taking the part along for the ride) within the free play of the backlash in both dimensions. Its also putting unnecessary wear on your leadscrew + nut especially with interrupted cutting. Those relatively small thread surface are the only thing keeping your table in that position.

 

[Megar arc 5040dd]

I finally have had a few minutes to get back to the mill and this brings up some more questions. I want to change the oil and in the manual it just says to drain the oil. It however doesn't say where and for the life of me I can't see anywhere to drain it. Does anyone happen to know how I am supposed to do that? Do I flip the head all the way over and drain int out the fill? That brings up my next question. In the diagram it has the oil fill plug on top and directly behind it it has a fitting it calls "radiator" with a hose coming out of it that doesn't seem to go anywhere. But as you can see in the picture mine has that "radiator" and hose in the front and what looks like a bolt with a washer behind it. What is the fitting with the hose in it for? And could the bolt behind it be their idea of a fill plug or is it a bolt holding something inside and should avoid removing it?


Also I put it on the chip tray the way it was when I purchased it but I am wondering if I have it backwards. should the hand wheel be over the chip tray like this or should it be the other way around so the hand wheel hands over the edge? It seems to have enough hand clearance the way it is but how is it supposed to be?

 

[DavidR8]

The mill didn't come with a chip tray so where it sits on the chip tray is entirely up to you.
Because the Y axis is going to move relative to the front of the tray I think I'd want it so that I didn't whack my knuckles on the tray.

 

[Johnwa]

My mill is a smaller version than yours. The oil drain on mine is underneath at the back of 5he head. On mine there is a fairly large rectangular recess in the casting so you have to get down low to see it.

 

[John Conroy]

That machine looks just like the PM932 I had. This is from the user manual, which is a free download on the PM site.