I hate my Z! (Axis... X2) Ideas?

[TroyO]

I really don't like the Z axis on my mini mill. I'm still in the process of getting set up/tuned but I get the feeling that good old Z and I aren't going to get along... LOL.

That whole worm gear/rack and pinion is just... sloppy.

Anyone have or seen a great idea for modifying that?

Thoughts that came to mind... just get rid of the existing system and put an Acme screw on it. Lots of cranking for big height changes though.

Next thought... same idea, but with a lathe leadscrew type half-nut system? I think the half nut has more slop though... that gets taken up and doesn't cause issue driving a lathe leadscrew, but may be a problem for a fine feed on Z.

Last crazy idea... what about a ballscrew driven/driver? I saw somewhere that you can either drive the screw, or the nut for linear motion. What if you had a ballscrew set up so you could turn the screw directly with a hand wheel, or using a (Gear? Belt?) drive from a larger crank turn the nut (@ 10 to 1 or similar)? You would have to lock whichever wasn't in use, though. Hmm, and also lock Z since the ballscrew won't hold it.

Or... maybe not re-inventing the wheel and just making another worm drive setup that actually fits nice and tight is the way to go?

Or just admit defeat and live iwth it, LOL?

Any thoughts/help/ideas or just brainstorming appreciated!

Thanks,
Troy

 

[Tin Falcon]

just put an indicator on it . Yes sloppy and unpredictable.
Tin

 

[ieezitin]

A indicator does not tell lies. Everyone else will, it wont. Shave off and get a reading then run true what the clock says then go from there.

All machines are not equal . Math is.


Anthony.

 

[TroyO]

Yeah, I already figured on putting a dial indicator on the stop for now. A full DRO is on the medium list.. somewhere in the middle.

LOL, of course "The list" kind of rolls out through the door and down the street like a bad christmas movie....

OK, it sounds like "Live with it" is the most viable suggestion, LOL.

 

[Troutsqueezer]

You get what you pay for.

You get used to it. In fact, after you make a milling pass and release the locking lever to lower the head for the next pass, it falls a predictable amount with no further effort on your part, just re-tighten and make the next pass. All the while keeping an eye on your DI of course. It usually falls around 10-20 thou. That works OK until you get close to your marks then you need to pay closer attention. Also if you're milling steel that is too much to take off on one pass for this machine. IMO.

-Trout

 

[techonehundred]

If you are going to put an acme screw in it, why not just split the nut and make a halfnut assembly for it. That way you can use the rack for drilling and the acme screw for fine feed. As a matter of fact, I am in the process of trying to do just this. Almost done, just working on a place to mount the half nut. assembly.

 

[black85vette]

Agree with it being sloppy. When I really want control of the Z axis for small distances here is what I do:

I have a coil spring about 2.5" long and 1" diameter. Looks like a small engine valve spring. I put it on top of the adjustable Z axis stop right in the middle. Then lower the head down onto it so that I have to keep force on the handle to keep the head down into position. Lock the head make the cut and repeat. I have learned to put the stop where I can get to the bottom of the cut I am making. Having that much counter tension keeps the head from dropping and gives it a better feel. I only use this when making accurate depth cuts in that axis.

Kind of a jury rig. But, fixing the poor design of the X2 is too much trouble for me.

 

[don-tucker]

I have just been milling some .030" deep recesses in mild st. using a DTI mounted on the Z axis stop,spot on every time.
http://www.homemodelenginemachinist.com/index.php?topic=8757.0
Thats the way to go
Don

 

[radfordc]

Adding a counterweight to the mill head (or an air spring) really makes the Z axis much nicer. My counterweight provides a slight upward force so that when I unlock the gibs I don't get any movement on the indicator. I can accurately feed the Z axis .001 at a time.

Charlie

 

[compressor man]

I just want to second everyone that has suggested adding a counterweight to this little mill. A good heavy weight will just about eliminate the tendancy for the Z axis to creep on its own volition. I have also added a non-digital caliper to the side of the column. I was tired of hearing about how coolant would ruin cheap dro's so I made sure that would not be an issue for me. Besides, an analog gauge is really nice, imo. It is easy to make changes on height by watching a gauge slowly advance rather then seeing those numbers flying around. Not saying that it is better than a dro by any means, but it does work and was cheap!

 

[TroyO]

I do have the air spring already. Belt drive is in the works.. making that.

Techonehundred... the half nut was in my list of possible ways to do it. I'm not real sure exactly how a half nout works... I saw a pic once upon a time and I recall it looked like it opened like a clamshell, but only one side actually has threads right? Seems like that would add slop... not that it wouldn't still be 100X better than the stock design.

I was also thinking an acme screw (say a 3/4 x 10 TPI) with a crank right on the screw... and another crank on a 10-1 gear drive. .1 per turn with wheel A, 1.0 per turn with wheel B. I think friction might kill that idea, though.

How do other mills do it? If the rack/worm concept is OK then it's just a matter of making a better one.

 

[rake60]

A Bridgeport mill uses the same rack and pinion design as the simple X2.

Why is it so much more stable and reliable?

A decent used Bridgeport can be bought for $6500USD.
A NEW X2 can be bought for $550USD on average.

Can you make the X2 perform like a Bridgeport? NO!

The X2 is a great little hobby mill. I really like mine!
I has the air spring, belt drive and extended Z rack.
It's still not a Bridgeport and I know that.

If it is used within it's limits, it is a safe and reliable little milling machine.

It is the operators responsibility to recognize and accept those limits.

Press it too far and it will bite back.
That may be in the form of permanent damage to the machine or
personal injury.

Common sense can keep that from happening.

Rick

 

[TroyO]

Well, I know it's not a Bridgeport... but that doesn't mean I have to live with all it's limitations either. I want to make it the best little mill I can.

I don't see how increasing the accuracy and fit and finish is pushing it's limits in way that will cause machine damage or personal injury?

But, if Bridgeport uses the same system it's a good bet the concept is good and it's the fit that is the issue... which gives me hope that I can make or buy a better hunk of rack material and maybe rebuild the gearing block to make it better.

 

[techonehundred]

Techonehundred... the half nut was in my list of possible ways to do it. I'm not real sure exactly how a half nout works... I saw a pic once upon a time and I recall it looked like it opened like a clamshell, but only one side actually has threads right? Seems like that would add slop... not that it wouldn't still be 100X better than the stock design.

I was also thinking an acme screw (say a 3/4 x 10 TPI) with a crank right on the screw... and another crank on a 10-1 gear drive. .1 per turn with wheel A, 1.0 per turn with wheel B. I think friction might kill that idea, though.

I started on this mod a while back, and am now going back to it. The largest 10 thread acme I found was a 5/8" from mcmaster. I built the half nut by taking a 1" square brass stock and drilling then threading it to fit the screw as close as I could. Then I split the nut with a bandsaw. I then machined a base with a groove for them to slide perpendicular to the screw. I them made an adjustable closer. So my nut has threads on both sides. My design will probably not win any awards, but we will see how it works when I get it installed. The biggest challenge at this point is thinking about how to put the handle in a comfortable place. If you place the handle at the top(the easy way), it will be a little high to reach. Otherwise I may need to find some angle gears to fix it much like the x3. Of course the angle gears have play also, so the fight continues. Hope this helps clear things a little. I don't have pictures tonight, but can get some if you would like. Also realize that sometimes I will bite off just a little more than I can chew. ;D

 

[mardtrp]

Hmm, all these threads about trying to make the X 2 into something it's not, reminds me of a comment made on one of the yahoo sites about re-working these mighty minis. It seems that there is a whole industry growing up around this phenomenon, so please take note of this simple statement about all this reworking.

------------------" your only polishing a turd " :big:

So you start out with an X 2 and after all this work and money, you still only got an X 2.

If you want something better than an X 2, then why not shell out the readies and go buy something bigger and better.

An X 2 is a nice bit of gear if you're willing to work with-in it's parameters, I've got one and I'm very happy with what it can do, it's a good bit of gear as far as I'm concerned, so why go to all this bother, waste of time and expense, attempting to try and turn it into what it aint and never will be.

Rake nailed it with his post too.

Mark

 

[RichD]

Try the counterweight like Charlie and other's have suggested. If you slightly overweight the head so you have to force it to go down you'll have a real smooth and predictable setup. I did this to my X3 mill the first day I got it and I can crank my mill head up or down with very little effort. I've had the mill for about 3 years or so and I've never regretted the counterweight.

It's cheap and easy to do.

Of course...it could go air-borne on you :bow:

Regards,
Rich

 

[Deanofid]

so why go to all this bother, waste of time and expense, attempting to try and turn it into what it aint and never will be.
Mark

Why would it be a waste of time to have it working like it should have in the first place?
Troy just wants it to function properly. Great that he's willing to fix it up nice.

 

[TroyO]

------------------" your only polishing a turd " :big:

Mark

LOL, you know the MythBusters proved that you can, in fact... polish a turd. ;-P

I'm not trying to make it a Bridgeport, or anything other than what it is... I guess it depends on how you think of it. Some see it as a Mill, with the ability and parameters of "X".

I see it as a kit... from which you can make a decent mill. Arrives assembled for shipping purposes only.. LOL. Ability and parameters will vary depending on willingness to invest time and some amount of money.

My personal rule of thumb... time isn't an issue. Although "Time is money", recreation is priceless. I consider the time doing such things recreation. So far the $$ investment hasn't been that high either.... 90% of the mods I've done were simply tweaking fit an finish with some small investment in materials... so far the Air Spring kit was the most expensive.. $40. I got the mill for $390... so I'm pretty sure I'm under the $500 mark still. (Well... not including tooling.... but that's transportable to another mill.)

I'm not suggesting it would be worth installing a $3,000 spindle or something... but why not spend a modest amount of money and some enjoyable workshop time making it be all it can be? For instance... new rack/pinion/worm/block would take what... maybe $30 in materials?

All in all... I'm glad it's not a Bridgeport. Otherwise I simply wouldn't have been able to have a mill at all.

Anyway... back to the topic at hand... well, next post. For some reason this forum keeps bouncing my text up and off the screen as a type.... drives me nuts. I typo way too much for that.. LOL.

Edit: Fixed some typos (But not all I'm sure.. LOL)

 

[Troutsqueezer]

I agree with everything you say Troy, well....except for one thing maybe. It already is a decent mill. More than decent actually.

It's good that you are making small improvements. I think the most transformational upgrade is converting to belt drive. Everything else (to me) is just a tweak. Not speaking of DRO's of course, that is a different matter.

-Trout

 

[TroyO]

Well to be honest... I'd be doing the same thing to a Bridgeport anyway... (upgrading/tweaking) but I would probably run out of stuff "worth doing" sooner, LOL.

I'm thinking that *most* of the fit issues are in the gear block... I think just re-doing that with the stock gearing and replacing the drive shaft with something better would make a big improvement.

The belt drive is one of the first projects to do once I get the mill going... right after the AXA tooplost for my lathe. I'm hoping to knock those two out (Compound mods for toolpost and the belt drive plate) before horking the stock gears, LOL. (That usually wouldn't be a challenge but I'm a dead newb on the milling front. Probability of "Doing something stupid" is high.)

After that maybe I can take a closer look at that gear block... maybe design one with some adjustability and bronze bushings would be enough.

DRO someday... I have a Schumatech built (The old one) for the lathe but not installed yet. I think the mill will get a 550... eventually.