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



## TroyO (May 25, 2010)

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


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## Tin Falcon (May 25, 2010)

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


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## ieezitin (May 25, 2010)

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.


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## TroyO (May 26, 2010)

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.


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## Troutsqueezer (May 26, 2010)

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


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## techonehundred (May 26, 2010)

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.


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## black85vette (May 26, 2010)

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.


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## don-tucker (May 26, 2010)

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


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## radfordc (May 26, 2010)

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


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## compressor man (May 26, 2010)

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!


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## TroyO (May 26, 2010)

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.


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## rake60 (May 26, 2010)

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


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## TroyO (May 26, 2010)

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.


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## techonehundred (May 27, 2010)

TroyO  said:
			
		

> 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


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## mardtrp (May 27, 2010)

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


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## RichD (May 27, 2010)

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


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## Deanofid (May 27, 2010)

mardtrp  said:
			
		

> 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.


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## TroyO (May 27, 2010)

mardtrp  said:
			
		

> ------------------" 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)


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## Troutsqueezer (May 27, 2010)

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


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## TroyO (May 27, 2010)

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.


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## Cedge (May 27, 2010)

Mark....
Maybe because I own it and simple wanted to tinker with it. It did all I ever asked of it, but I could and did make it do more than the original design. The challenge was half the fun. You can polish your whatever but the rest of us have mills to play with. I didn't think we needed your permission.

Steve


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## AR1911 (Jun 3, 2010)

You can tighten up that Z-axis rack by shimming it out.
Good to do when you install the LMS rack extension.


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## doubletop (Jun 4, 2010)

Whats all this "why bother" nonsense isn't this an engineering forum? Making a piece of metal into something it wasn't yesterday.

Apart from those of you who do it for a living, none of what the rest of us do would stack up as a good business case. But we enjoy doing it anyway.

Pete


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## purpleknif (Jan 2, 2012)

I put a counterweight on mine 1st thing. Machines from a 2 1/2" jig mill to an 8" G&L boring mill have them. Why not mine? BIG improvement!


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## Ken I (Jan 2, 2012)

Mine came with the air spring - so it only moves if told to - but the increments are huge.
I added a vernier as an el-cheapo DRO and that helps out a lot.

I made a dead stop that clamps onto the column - you can use this to "micrometer" into a job particularly where the cutter might snatch.

Beween the two I come out OK.

Ken


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## rleete (Jan 2, 2012)

I recently installed the LMS gas spring conversion, and that helped quite a bit. Adjusting the gibs helped more, and shimming out the rack (longer one that comes in the kit) really took out most of the backlash.

Shimming the rack will help engagement and really make things feel more positive. It doesn't take much to make a difference you can actually feel. I think I used about .003" on one end and .002" on the other, splitting the difference in the middle. Takes a bit of trial and error to get it right without binding, but it well worth it.


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## ShedBoy (Jan 2, 2012)

Never been close to one of these machines so I have no idea what they are built like. 

I like the saying polish a turd but it is a pointless exercise because you will just have a shiny turd but as my grandad told me once you are better to roll it in glitter it will be more pretty :big: :big:

As for the z axis with alot of machining and adapting you could bung a ball screw in it with some bevel gears to get the drive out the side but the handle won't move up and down with the head. There are lots of things you can do which will all cost money. Draw a line in the sand and decide how much you want to spend and how much are you willing to work with. Like yourself I like to do things to see if I can and because it is fun, who cares what other people think. Opinions are like belly buttons, everyone has one and their all different.

I have a bridgeport clone and it has more than it's fair share of quirks but it is a 1980 model.

Brock


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## miner49r (Jan 2, 2012)

Wow. This thread is a year and a half olde. 
There is a lot of mods for fixing the slop in the Z axis of the X2.

a) counter weight or gas springs. (already discussed here)
b) shim the rack. (also discussed here)
c) replace the u-jointed rod with a solid rod that comes from the fine feed dial.
d) place a ball bearing to preload the worm gear where fine feed meets coarse feed.
e) peen over the castle nuts at the fine feed engagement for a tighter fit.
f) always keep up pressure on the downfeed handle when adjusting your cut. Lock gib and go.

These are not my ideas. They have been gleaned from several different sites. Most of which cost little or nothing and will reduce the lash of the X2's Z axis to an acceptable amount. I don't have a DRO and don't use a DTI. I make the first cut, take a measurement, do some subtraction, and cut away using the fine feed dial. It's all about the operator knowing his machine

When I was looking for a mill, I needed one I could carry into the basement. The G704 was top on my list until they became unavailable. Next was the X3 & IH clones. Then I came across a coupon for the X2 selling for $299. It does exactly what I need it to do and I spent the rest on tooling. (and it saved the newly straitened quill on my drill press)

Alan


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## Wrist Pin (Jan 3, 2012)

I have the HI-Torq Mill from the Little Machine Shop and I love it but I also hate the Z.
I have to hold the head up when feeding down to keep it from dropping. Other than that it is fine and quite accurate.
Is the gas cylinder upgrade worth it?

PS, I always say, " You can paint a turd gold, but it still stinks".
Jim


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## rleete (Jan 3, 2012)

Wrist Pin  said:
			
		

> Is the gas cylinder upgrade worth it?



Yes! If for nothing else than the longer rack (about 1.5 times the length of stock) which gives you more travel. You probably can't make the parts and buy the gas spring for what they charge.

Do NOT drill the hole in the back of the column down 12.0" as the instructions say. This limits lower travel (the whole point of a longer rack) by about 2-3 inches. I drilled a second hole - I already made the first one - down 14.5" from the top. This means you can get the spindle nearly touching the top of a small vise, roughly 3.0" from the top of the bed.

The gas spring supports the head much better, improving the drop problem. I would strongly recommend that you take the time to shim out the rack (feeler gauges work well) to tighen up the fit between it and the gear. this makes it feel smoother, with less play. Don't make it too tight, or it will bind, probably causing more wear.


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## Troutsqueezer (Jan 3, 2012)

The airlift also makes a good place to stick your welding magnet which holds on to your spindle wrench and doo-hicky.


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## Wrist Pin (Jan 4, 2012)

OK, now I have a problem.
Troutsqueezer's picture, ( I just love that handle. Do you really squeeze trout when you catch them??), shows the gas cylinder rod extending about a foot above the head if I am looking at the picture right. I have no room above the head of my Hi-Torq for that .
Perhaps I would be better off with a counterweight.
I will also look into the rack situation and see if I can improve it.


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## Captain Jerry (Jan 4, 2012)

Wrist Pin

Most, if not all of the problem of head drop can be resolved by careful and regular gib adjustment. In my shop the first day of every month is "GIB DAY"! All gibs, mill and lathe, are cleaned, lubed, and adjusted. On the mill, the top gib screw is the most important. Put an indicator between the table and the front end of the head and watch the dial as you tighten the head lock. If it moves, the top gib screw is too loose. I keep mine tight enough so that there is no drop and no droop and of course, I lock the head before every cutting op. If the bottom gib screw is too loose, down pressure on a drilling op can cause the outer end of the head to rise and take the quill axis out of line with the column slightly. It takes regular maintenance to keep it working right.

Hope this helps.

Jerry


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## MachineTom (Jan 4, 2012)

Rake60 said, Bridgeport has a rack and pinion, yes but on the quill, the knee is a acme screw with bevel gears, and its the knee which is used for milling, the quill for drilling boring. 

If the goal is to be accurate in downfeed, a worm gear driving the rack pinion, and a force pushing up the head (air,weight) would seem the best way to do it. A BP knee has a pitch of .200 for the screw but 2:1 gearing so each turn of the crank is .100, its great excersise to crank a 800# knee 16". I always think about adding an air assist, but then decide to make parts instead.


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## Ken I (Jan 4, 2012)

This is my mill - not terribly clear in the photo but the gas spring stops just short of my flourescents (I have the upper stop set about 5mm lower than maximum to stop it crashing into the tubes) one day, needing a bit more hight & forgetting why I set it there I imploded a tube - big fright.






The el-cheapo DRO is a vernier bolted to the front of the head (again not terribly visible) and the mechanical stop which clamps to the column.






It has a printed paper dial which has to be replaced from time to time (I must get round to engraving the damn thing).

Uses a M12x1.0 thread so the divisions are easy.

Ken


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## purpleknif (Jan 4, 2012)

So okay, now we've got the drop problem solved. Now what we need is a Z axis feed. Any ideas?  ???


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## rleete (Jan 4, 2012)

Ask the wife to do it for ya?


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## rake60 (Jan 4, 2012)

purpleknif  said:
			
		

> So okay, now we've got the drop problem solved. Now what we need is a Z axis feed. Any ideas?  ???



I wouldn't want a Z axis feed.

That would take away the _*feel*_ of a small drill bit or end mill snapping off in an almost finished part.


Rick


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## MachineTom (Jan 4, 2012)

A BP has power feed on the quill .0015, .003, .006 rarely used with drill, but very often used when boring. The feed rates are ok for boring, slow for drilling, also when drilling you need to keep disengaging the feed to clear deep holes, the quill lever is quicker overall. IMO


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## don-tucker (Jan 5, 2012)

This is my power feed for the Z axis




The big handle makes life eaiser when feeding down, I remove it for normal use.
Don


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## TroyO (Jan 5, 2012)

Rake60... I know that refreshing snap-crunch *feel* you are talking about!

Old thread... and I still haven't done much about the Z axis. 

I have a DRO so it's a little easier to fiddle-by. Dial it in, lock it up and go. I still hate it... it's the least well performing axis on the machine and with it being a mini-mill that's saying a lot. ;-) It also sucks when trying to drill an exact depth... 30---35---90... WTF?

I did get the Making Gears the Easy Way video so maybe it will get a revamped worm drive which I think would help a huge amount. I do also wonder if a simple leadscrew with a big disk on top might work pretty well too. Turn slow for precise increments, and "slap-spin" it for quick adjustment using the flywheel effect... not sure.


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## purpleknif (Jan 5, 2012)

I'm referring to a Bridgeport type feed for boring. Tough to get a good finish by hand. Yes, it would have to disconect for drilling and such.


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## dgjessing (Jan 5, 2012)

Captain Jerry  said:
			
		

> ...I keep mine tight enough so that there is no drop and no droop ...



Me too. If the thing will drop on its own accord Id say tighten the gibs :


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## Wrist Pin (Jan 10, 2012)

Over the weekend I did a real fast, (half-fast?), job of tightening the gib on my Z.
It did improve the drop problem but it still drops when close to the top. Guess the next step is to shim the rack.
Thanks to everyone for the info and ideas!
Jim


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## purpleknif (Jan 10, 2012)

Looks to me like the gas spring in the pic is inside the column. Couldn't do that on mine, I got a couple of cast ribs in the way. Hmmmm...


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## TroyO (Jan 10, 2012)

My rack "shim" was quick and dirty... I used aluminum foil tape, like you use to seal up duct work. (But not duct-tape/duck-tape)

Stick it on, trim it with a razor and try it. I think I used 2 layers?

RE: Tightening gibs... that's not really what the problem is. Of course you can tighten the gib to make everything super stiff... which I tend to do but then you have to crank hard on it to move it.

IMHO the "drop" happens because the pinion gear in pushing the head down is doing so by applying contact to the -bottom- faces of the rack gear. 

The bit, when it grabs and pulls down pulls the head directly and it won't stop until the pinion teeth contact the -top- of the next set of rack teeth. You also have a sloppy worm gear involved that lets the pinion move when it drops too.. making it even worse. 

The only "fix" I can think of is different drive system entirely OR very careful fitment to minimize slop between the worm, and pinion and rack so the pinion teeth contact both the top and bottoms of the gear rack at the same time and the worm keeps the pinion from turning freely. 

I'm kind of thinking a 10 TPI lead screw might work pretty well. 10 turns per inch, ~12" travel so no more than 120 revs from end to end..... not so hot for drilling though.

Anyway.. learned to live with it mostly. Still hate it tho... LOL. Still on the someday list...


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## lensman57 (Jan 10, 2012)

TroyO  said:
			
		

> 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.
> 
> ...



Hi Troy,

While we are all it you can add the Z axis on my X1 mill to the list as well.
I have sort of converted it to cnc and while the X and Y axis have about 0.04
~0.06 mm back lash the Z has about 0.9mm, I have not done anything really special to sort this out with the exception of hanging 12kg of my dumbbell weight to the column to keep it straight.
What a waste of effort and money this turned out to be.
I was thinking of making a second nut for the Z axis but I don't seem to be able to find one for M10 and 1.5mm pitch in the UK.
Regards,
A.G


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## Wrist Pin (Jan 10, 2012)

In the Hi-Tork Mill from Little Machine Shop that I have, the Z is not controlled by a worm/rack. It is a rack/pinion arrangement. Until I tightened the gibs, it would drop when ever moved. Now it doesn't move except when at the top of its travel. 

What I did before the gibs was to hold upward hand pressure on the head as I moved it down into position and before releasing pressure, would make sure the Z lock was tightened. This has worked very well in the past and I continue to do so now, mainly because I don't trust it and don't want to lose a work piece that I have a good amount of time in. I find this to be very reliable and accurate for this machine. I have been very happy with the results.

For what it is worth...


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## TroyO (Jan 10, 2012)

Ohh yeah, there are tons of ways around it. I actually don't mind it so much when I am setting a height and locking down the gib. It's when drilling or feeding in Z when it's a PITA, lol. (Or when I forget to lock the gib...)

This one has a rack/pinion and the pinion in turn hooks to a worm gear gear drive for "fine feed". The drill press handle drives the pinion directly.


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