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SIEG X2 Y Axis Stock Screw Dimensional Drawing?

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MetalMuncher

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#1
Does anyone know where I can find a CAD type drawing of the stock Y axis screw for a SIEG X2 mill? I am specifically interested in the end machined for the hand wheel and support block, and the dimensions of that machining.
 

MetalMuncher

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#2
Or, alternatively, a supplier of 20 TPI ball screw kits machined to use the original hand wheels of the SIEG X2? I'd like to convert only my Y axis screw to a ball screw, but I have no interest in converting to CNC. I also don't really need to do the X axis, as it works smoothly and already has a power feed on it. So I am looking for a single kit for just the Y Axis.
 

DAT510

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#3
Just a heads up regarding the use of ball screws in Manual Mill (Non-CNC) setup. Ball Screws are two way. What I mean is turning the screw moves the Nut/Table, but also pushing on the Table will turn the screw. Unlike Acme or Square Treads, which are "one way", where only turning the screw will move the Nut/Table, just like worm drives.

I bring this up because, without something to hold the screw in position (such as a Stepper or Servo) you will alway have to make sure the table is locked or any pressure will move it.

Based on your second post, are you looking to improve the "smoothness" of the Y axis?
 

MetalMuncher

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#4
I did not know that. Thanks! I do have a power drive on the Y axis, but it has a disengagement clutch to make it easier to use the hand wheel.

Yes, my goal is to get around the miserably poor smoothness of Y axis movement when the gibs are anywhere near reasonably snug.

My opinion of how they overlooked adding a rear carrier bearing on the screw is about as low as it could be. There is certainly room for one. I've thought about making one, but converting to a ball screw would be easier. I have a Phenom thrust bearing kit on the screw, and that helped a little. I can get fairly smooth movement with a lot of patience in the adjustment procedure for the front screw support block and for its acme nut, but their intended design for the nut retention screw to not be torqued down fully is another miserably poor design. And the smooth movement I do achieve is always a time bomb waiting to change, usually in the middle of some involved machining project requiring a lot of Y axis movement.

The whole reason I designed a power drive interface for the Y axis is to help with how difficult turning the Y axis screw can get when it starts to go out of perfect adjustment in the middle of some project. Sometimes even the power drive won't turn it. Then I have to tear things down and redo the adjustment before I can complete the project in progress. I'd like to find an affordable way to eliminate this problem. This mill is highly customized, so I doubt I'll ever look toward a different mill.
 

DAT510

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#5
Sounds like you've done a lot of work to your mill. Versus the leadscrew, could your issues be more related to your ways and gib?

Could the Gib benefit from stoning or flattening/smoothing on a surface plate. Regarding the ways.... could they also be stoned or going to the extreme, you could consider scraping?
 

MetalMuncher

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#6
I won't consider scraping, but the gib strips have already been polished on a surface plate. The problem is not there.

As I mentioned, when I can get all the planets to align while hitting that infinitescimle sweet spot adjusting the screw support block and acme nut retainer, I get very smooth travel. The problem is that the acme nut moves, as per their stupid design, and in so doing it binds on the screw. If I torque the nut retainer down, then it also binds. If I leave the nut retainer too loose, it also binds. It has to be tightened to some imperceptible magical amount that has no definition, so it can't possibly be expected to remain as such. The only reason for such a (ridiculous) set up is because they KNOW the acme nut and its slot are poorly machined, so this was their half baked solution....to allow the nut to wander around instead of being held in precise alignment.

I have to wonder if it would even work to put a carrier bearing on the far end of the Y screw so it can't wander off being parallel to the ways. It may come down to their not making the ways perfect either. But I've seen so much discussion on converting these X2 mills to CNC that I feel using a ball screw must be improving on the poor original design, or there would be tons of dialog on CNC not working with these mills. So I am thinking the problem is not in the ways. It is in the original acme screw and nut.

It has occurred to me today that I have a way to create a CAD drawing of the screw's hand crank machined end myself. When I converted this mill to inch scale many years ago, I kept the original metric acme screws. The shaft dimensions for the crank end will be identical. I can measure the old metric shaft to get the dimensions and draw it up myself, without taking my mill apart. I would need this drawing in the event I decided to order a customized ball screw to fit the mill's Y axis, so I could provide the vendor with the drawing for their custom machining.
 

DAT510

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#7
Your comment " I have to wonder if it would even work to put a carrier bearing on the far end of the Y screw so it can't wander off being parallel to the ways" made me wonder... Could you leadscrew nut and Y axis bear block not aligned, given the lead screw moves off parallel to the ways as you move the axis?

The reason I mention it is, I recently refurbished a Syil X3 CNC mill, which is built on the chassis of the Sieg SX3 ( the big brother to your X2). The owner sold it because it was loosing steps on the X axis and he was unable to determine the cause. What I found was the Ball Nut was originally mounted slightly Off center and Low, from the centerline of the lead screw, causing the screw to bind towards the ends of travel. I took me about a 1 week of chasing to figure it out. In my case the bearing block at the end of the lead screw made it worse, since it prevented the screw from deflecting as it got closer to the bearing block.

Hope this helped... Good Luck
 

MetalMuncher

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#8
I am wondering if you are familiar with the way the SIEG X2 Y axis screw and nut are constructed? There is no way to "align" the nut. The manual tells you it is SUPPOSED TO move. They tell you to only "snug" its retention screw so that the nut is pretty much loosely held in whatever is the closest to a real alignment. Its poor design. They do that, coupled with the lack of a tail end carrier bearing, so the screw can move around "if needed".

It's like how some people only fasten one end, and the head screw, on a DRO scale, because they don't want to take the time and patience to properly get the scale fastened such that the head travels perfectly aligned from end to end with both ends and the scale head firmly screwed down. If you try to fasten the nut retainer screw tightly, the screw will bind at some point(s) in travel. My statement that the screw goes off parallel is an assumption, I admit, as it is forced in some direction by the movement of the acme nut in its loose holder, as it suddenly grabs in the slot. Ideally, wanting something to be able to move around in a slot should not incorporate the end of a screw trying to hold it in place, but should incorporate lubricated polished bearing surfaces to guide it along a desired path if it does move, precisely adjusted to eliminate chatter. Imagine if, instead of a nice smooth flat gib strip, the ways on the mill table axis were held in tight tolerance instead by only the tips of the gib screws themselves against the ways. That's essentially what SIEG did on this acme nut.

The X2 Y axis nut looks like an inverted tombstone. The threads for the screw are toward the rounded end. The squared off end sits upward in a slot that is wide enough to allow the tombstone to rotate many degrees left and right of being perpendicular. In fact, it can rotate beyond the point where it comes out of the slot in the carriage, if not careful when adjusting it. This allows for flexing of the screw (which ideally should never be needed) to accommodate whatever travel errors are occurring along the screw path, likely due to the fact the screw isn't rigidly constrained. This is a top heavy orientation. If the "snugged" retention screw loosens (it hides behind things you must remove to access it), the square top end of the tombstone "flops over" to one side or the other. Note that the alignment of the tombstone nut is the only thing holding the screw parallel to the ways, since the screw is free floating at the tail end. So when the nut tries to flop over, it pulls the screw sideways with it, and that is what causes it to bind, usually bringing a halt to any project until you disassemble, re-align and re-assemble things again. Typically, when the nut "moves" to one side, it never "moves" back the other way because of the retention screw grabbing at its surface as it slides past the screw end. That nut needs to be held in place vertically so it can't flop over. On the X axis, the squared off (heavy) end of its tombstone nut hangs down instead of pointing up, so gravity helps keep it centered. Perhaps what they should have used on the Y axis is a circular disc, with the acme threaded hole in its center, rather than the crazy inverted tombstone design they used. Hmm. I wonder if that idea would retrofit?

It is interesting you mention the X3 uses a tail carrier bearing. Perhaps they realized how essential that is. When they did, they should have applied the idea to any further X2 models produced. I've been through 3 different base castings along my upgrade path to the wider table and then a fixed vertical column. Every one of them lacks the tail bearing, and has this same problem with the Y axis screw binding. This "floppy nut" issue causing the binding is intrinsic to their design, it is not just a single incident on one casting. If they would have used the same design they use on the X axis, which has a bearing at both ends, and moves as smooth as butter, there would not have been this issue.
 

9t8z28

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#9
I have the factory Y axis and X axis leadscrews out of my Sieg X2 if you want me to get you any dimensions with a picture or something? I installed the LMS imperial leadscrews and now have a larger table abd solid column so I will never use them again if you are interested in one or both of them.
 

MetalMuncher

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#10
There is one thing you could tell me, since you offered. Are the screws 5/8" diameter? I've been trying to remember that, but hadn't yet dug into finding out.

If you're interested, I've learned that the shaft thread technically isn't ACME as I had thought. ACME doesn't offer the 20 TPI you have now. They are a thread called Unified Standard. I had been looking for a tap or nut and none of the ACME sizes at all use 20 TPI. But there are many of the Unified Standard diameters that use 20 TPI. So I am thinking they are UNS 5/8 - 20 TPI.

I am re-thinking an upgrade to ball screws, given the above information on how they can rotate under a load if manually operated instead of using stepper motors. Now I am considering adding a rear shaft bearing to the Y axis screw instead. I think that might eliminate the screw binding I get when the axis nut shifts in the middle of a project.

You're going to like the upgrades you did!

BTW, if you're wondering can you stack the 2 inch riser blocks LMS sells for extending the solid column, I'm using 2 of them stacked up. I had to find a new longer air spring for lift, but it all works together very well. One of the most major drawbacks to these mini mills is a serious lack of Z axis travel. I also bought a second rack gear, cut it to fit, and mated it to the original, so I can move the head the extra distance of travel toward the table. Later testing seems to indicate there is no concern for flexing with the stacked riser blocks under the solid column when taking heavy milling cuts.
 

MetalMuncher

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#11
Mulling over this whole "floppy tombstone" design of the Y axis screw and nut, I decided to look into what the "genuine article" uses to move the Y axis. Looking at the design of this Bridgeport Series 1 hardware, its pretty obvious nothing is intended to wobble around "if needed" as SIEG's design does. There has to be a way to eliminate this hassle in the X2 Y Axis. Some kind of rigidly adjustable nut in place of their design. The saddle doesn't wobble around when it slides, and the screw, although only held from one end, is held rigidly from that end, passing through a bearing block in close tolerance to its shaft. So the screw can't wobble around any appreciable amount. The only thing that tries to move is the silly tombstone nut held "loosely" in its over-sized slot. Perhaps something to make the slot a closer fit, and not allow the tombstone to rotate more than a few degrees might help. Or, re-design the nut with the same goals in mind, so it nearly fills the slot?

Bridgeport Y Axis Screw.png
 

homebrewed

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#12
An alternative to modding your Y axis drive with a ball screw/nut is to make a new block that uses real thrust bearings like this. I made something similar and it totally transformed the feel of the Y axis. If you make a simpler one-piece bearing block you may lose a bit of range on the Y axis, but worst-case it's not much -- somewhere around .2" if you make the block the same thickness as the OEM part. I made mine out of 6061 and it works just fine.

The reason you may lose a bit of travel on Y: the thrust bearing OD puts it a bit proud of the base so it fouls the table. The design at the link I provided moves the thrust bearing out a bit, but at most you only get a few tenths (of an inch) more range because the feed nut comes up against the base....so there's only so much you can do.

The method for adjusting axes for minimum drag on these machines is to loosen the set screws that hold the feed nuts, run the table up close to the hand wheel and tighten the set screws. You also may find it helpful to (at the same time) loosen/re-tighten the bolts that hold the bearing blocks in place. The built-in manufacturing slop takes care of the rest.

Yes, clear evidence of a poor design, but we're talking about an inexpensive hobbyist-level machine here. Consider it an opportunity to get creative :).

Edit: To give proper credit, I did not design the block shown in the link (a member of the 7x12MiniLathe@groups.io group did that). I just made one like it.
 

MetalMuncher

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#13
That's a beautiful thrust bearing modification!

I already have a thrust bearing mod on mine, sold by Phenom. It is not as involved as the lovely one you showed, but it does help.

Regarding losing some Y axis, when I switched from just having the LMS Large Table to also having the Solid Column (which requires switching the base casting as well) I found that I could actually increase the Y axis travel range by spacing the front bearing block, supporting the crank end, away from the column by an extra half inch using a spacer block I made for that purpose. That almost made up for what I lost by having the DRO X axis glass scale mounted to the back of the table.

I have found with a lot of patience, trial, and error, that adjustment method you mentioned will allow me to actually tighten down the retention screw on the Y axis nut much more than the loose grip they suggest. It's a balancing act between all three screws and the angle you put on the Y axis screw by lifting or pressing down on the crank wheel while you tighten them. But eventually I find that even with the nut retention screw tightened reasonably, the nut still eventually moves, usually at the very worst possible moment while in the middle of a project, and can result in binding the screw shaft so badly you have to stop and fix it.

Rather than going the ball screw route, I am currently thinking about ways to "stabilize" the Y nut so it can move a little, but would be constrained such that it can't cock over in any direction enough to bind the screw. Perhaps a pair of springs bored one into each side, to keep it from rotating very much. I've also toyed with the idea of making a new nut with its weight mass centered at the bottom, instead of at the top. The X nut has its weight at the bottom, and it never moves on me at all. Being top heavy, the Y nut is begging to rotate all the time.

Agreed, it is a hobby level machine, but that doesn't mean it needs to be "thrown together cheaply". They've sold enough of these to have been worth more thought and a better design here. I know the X3 has a support bearing at the rear end of the Y shaft. They wouldn't have added that unless they realized it is needed, probably through complaints about the lack of it on the X2. They could have offered an X2 upgrade to add that bearing.

Creativity is how we take these "once inexpensive" (no thanks to the current establishment's tariffs) tools and make them into something truly useful. Thus the many modifications this machine has seen since I bought it years ago. This Y axis binding is pretty much the last annoyance I am trying to remove.

:) I Thank you all for your suggestions!
 

9t8z28

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#14
Correct me if I am wrong but you dont want the leadscrew nut to move. The set screw should be tightened to keep it from moving. What I do is run the Y axis all the way forward and then all the way back and figure out where the nut works best in both directions and then tighten it down. If it moves it allows a lot of slop which is no good unless you have DRO’s. If its positioned wrong it binds really bad in one direction but not the other.
I just measured the threads and they are .615”.
Have you looked into Phenom Engineering’s Y-axis bearing upgrade? It does not completely solve the problem but it does help tocsmooth out the motion.
I am working on getting you those dimensions. I am hoping too
Mulling over this whole "floppy tombstone" design of the Y axis screw and nut, I decided to look into what the "genuine article" uses to move the Y axis. Looking at the design of this Bridgeport Series 1 hardware, its pretty obvious nothing is intended to wobble around "if needed" as SIEG's design does. There has to be a way to eliminate this hassle in the X2 Y Axis. Some kind of rigidly adjustable nut in place of their design. The saddle doesn't wobble around when it slides, and the screw, although only held from one end, is held rigidly from that end, passing through a bearing block in close tolerance to its shaft. So the screw can't wobble around any appreciable amount. The only thing that tries to move is the silly tombstone nut held "loosely" in its over-sized slot. Perhaps something to make the slot a closer fit, and not allow the tombstone to rotate more than a few degrees might help. Or, re-design the nut with the same goals in mind, so it nearly fills the slot?

View attachment 278979
 

9t8z28

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#15
EDIT: I wrote a reply before I read your latest replies so disregard everything excpet the thread major diameter

Correct me if I am wrong but you dont want the leadscrew nut to move. The set screw should be tightened to keep it from moving. What I do is run the Y axis all the way forward and then all the way back and figure out where the nut works best in both directions and then tighten it down. If it moves it allows a lot of slop which is no good unless you have DRO’s. If its positioned wrong it binds really bad in one direction but not the other.
I just measured the threads and they are .615”.
Have you looked into Phenom Engineering’s Y-axis bearing upgrade? It does not completely solve the problem but it does help tocsmooth out the motion.
I am working on getting you those dimensions. I am hoping too
 

9t8z28

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#16
I too have a scale on the back of the table. I really didnt loose much travel since I have the read head standing up and tight up against the back of the table but I am curious as to how you added travel to the Y-axis. How much travel do you think you gained? Is this simply a 1/2” spacer? Any other mods required?

That's a beautiful thrust bearing modification!

I already have a thrust bearing mod on mine, sold by Phenom. It is not as involved as the lovely one you showed, but it does help.

Regarding losing some Y axis, when I switched from just having the LMS Large Table to also having the Solid Column (which requires switching the base casting as well) I found that I could actually increase the Y axis travel range by spacing the front bearing block, supporting the crank end, away from the column by an extra half inch using a spacer block I made for that purpose. That almost made up for what I lost by having the DRO X axis glass scale mounted to the back of the table.

I have found with a lot of patience, trial, and error, that adjustment method you mentioned will allow me to actually tighten down the retention screw on the Y axis nut much more than the loose grip they suggest. It's a balancing act between all three screws and the angle you put on the Y axis screw by lifting or pressing down on the crank wheel while you tighten them. But eventually I find that even with the nut retention screw tightened reasonably, the nut still eventually moves, usually at the very worst possible moment while in the middle of a project, and can result in binding the screw shaft so badly you have to stop and fix it.

Rather than going the ball screw route, I am currently thinking about ways to "stabilize" the Y nut so it can move a little, but would be constrained such that it can't cock over in any direction enough to bind the screw. Perhaps a pair of springs bored one into each side, to keep it from rotating very much. I've also toyed with the idea of making a new nut with its weight mass centered at the bottom, instead of at the top. The X nut has its weight at the bottom, and it never moves on me at all. Being top heavy, the Y nut is begging to rotate all the time.

Agreed, it is a hobby level machine, but that doesn't mean it needs to be "thrown together cheaply". They've sold enough of these to have been worth more thought and a better design here. I know the X3 has a support bearing at the rear end of the Y shaft. They wouldn't have added that unless they realized it is needed, probably through complaints about the lack of it on the X2. They could have offered an X2 upgrade to add that bearing.

Creativity is how we take these "once inexpensive" (no thanks to the current establishment's tariffs) tools and make them into something truly useful. Thus the many modifications this machine has seen since I bought it years ago. This Y axis binding is pretty much the last annoyance I am trying to remove.

:) I Thank you all for your suggestions!
 

9t8z28

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#18
That’s interesting about the leadscrew. I thought it was ACME but I guess thats why I was never able to find much information about it.

I am also using the 2” column riser block and have not noticed any difference in rigidity but I am only using 1 spacer. I think you are the first person I have heard to of ever used 2 spacers. Your mill must have a ton of travel! I have been contemplating upgrading the studs as I feel they are not adequate. I cant remember what size hardware I got to replace them with. I have not gotten around to doing it yet but I will soon because I need to re-tram the column. When I trammed it I used LMS’s plastic shim stock. I know, it was stupid but it was all that I had at the time. I now have Steel shim stock to replace it with and I am hoping it makes it a little more rigid although I think its rigid enough for even 1/2” end mills and slightly larger.

There is one thing you could tell me, since you offered. Are the screws 5/8" diameter? I've been trying to remember that, but hadn't yet dug into finding out.

If you're interested, I've learned that the shaft thread technically isn't ACME as I had thought. ACME doesn't offer the 20 TPI you have now. They are a thread called Unified Standard. I had been looking for a tap or nut and none of the ACME sizes at all use 20 TPI. But there are many of the Unified Standard diameters that use 20 TPI. So I am thinking they are UNS 5/8 - 20 TPI.

I am re-thinking an upgrade to ball screws, given the above information on how they can rotate under a load if manually operated instead of using stepper motors. Now I am considering adding a rear shaft bearing to the Y axis screw instead. I think that might eliminate the screw binding I get when the axis nut shifts in the middle of a project.



You're going to like the upgrades you did!

BTW, if you're wondering can you stack the 2 inch riser blocks LMS sells for extending the solid column, I'm using 2 of them stacked up. I had to find a new longer air spring for lift, but it all works together very well. One of the most major drawbacks to these mini mills is a serious lack of Z axis travel. I also bought a second rack gear, cut it to fit, and mated it to the original, so I can move the head the extra distance of travel toward the table. Later testing seems to indicate there is no concern for flexing with the stacked riser blocks under the solid column when taking heavy milling cuts.
 

MetalMuncher

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#19
EDIT: I wrote a reply before I read your latest replies so disregard everything excpet the thread major diameter
Thanks! In the interim, I was reading a lot of forum posts looking specifically to see if anyone had ever added a rear support bearing on their Y axis screw. I didn't find anything about that, except that many feel this is an acceptable way to do it, supporting the screw only at the crank end. My personal opinion disagrees. But I did find mention of the axis screws being 5/8-20 (on the ones with inch conversion screws).

Here is a link to a slew of information on threads, including where I discovered that there were no 20 TPI listed under standard ACME sizes, but several 20 TPI across the range of UNS thread. Thus, knowing we have 5/8 screws now, I concluded they are UNS 5/8-20. A tap for that thread is available on McMaster-Carr if anyone needs one. Also the 37/64 drill bit required for it.

https://www.gewinde-normen.de/en/20-un-thread.html
 

MetalMuncher

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#20
I too have a scale on the back of the table. I really didnt loose much travel since I have the read head standing up and tight up against the back of the table but I am curious as to how you added travel to the Y-axis. How much travel do you think you gained? Is this simply a 1/2” spacer? Any other mods required?
I gained 0.540". If you will excuse the fact that my CAD drawings are meant only for my own use, and therefore probably do not adhere to any kind of accepted "standards" for CAD in the outside world, I can add a drawing of what I made.

This may or may not work for anyone else. I make no promises. And understand that is is MOVING the travel range of the Y axis, not EXTENDING it. This steals 0.504" off the back end and moves it to the front. The problem is that the rigid column base puts the table closer to the column than it was with the stock column that pivots on the shaft and nut. Because I was losing the 1/2 inch due to the scale thickness (glass scales) I didn't want to give that up. The X2 mill, even with the large table upgrade, has such a meager travel on the Y axis, every little bit counts! It is basically just a spacer, with 3 holes in it, made to fit in between the crank support block and the base casting. I made mine out of aluminum, one of my favorite materials to work with.



Mini Mill Y Axis Screw Extender.png
 

MetalMuncher

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#21
That’s interesting about the leadscrew. I thought it was ACME but I guess thats why I was never able to find much information about it.

I am also using the 2” column riser block and have not noticed any difference in rigidity but I am only using 1 spacer. I think you are the first person I have heard to of ever used 2 spacers. Your mill must have a ton of travel! I have been contemplating upgrading the studs as I feel they are not adequate. I cant remember what size hardware I got to replace them with. I have not gotten around to doing it yet but I will soon because I need to re-tram the column. When I trammed it I used LMS’s plastic shim stock. I know, it was stupid but it was all that I had at the time. I now have Steel shim stock to replace it with and I am hoping it makes it a little more rigid although I think its rigid enough for even 1/2” end mills and slightly larger.
I've not had any problems using a pair of the 2" lift blocks. I did add another piece of rack gear onto the bottom of the stock length used on the solid column, so I can lower the head way down closer to the table. My original thinking was that, since I use as 3" screwless vise most of the time, or a rotary table, I really didn't need the head as close to the table as you get without using spacers. Originally I had left the Z axis scale as it was, because of this (moved from my original tilting column) on the DRO 350 I had been using. But when I got the new DRO with glass scales I ordered the Z axis scale long enough to allow for the extra 4 inch lift. So at that time I also extended the rack gear. It is so nice to be able to work on taller things!

These machines, if properly modified, strengthened where needed, etc., are capable of far more than their printed rating. Admittedly, I work mostly with aluminum and plastics. I try to avoid steel unless it is a necessity. But I do work with steel when needed, and just keep the depth of cut down to 60 mils or less. With 6061 aluminum or plastics, cutting 0.1" passes is easy. That said, I routinely use milling cutters up to 1 1/2" diameter, and a fly cutter that is about 3" diameter. I have also cut T slots across a 6 inch diameter disc of 6061 on my original rotary table. I think that was one of the hardest jobs this mill has done so far, but it did it without complaining.

For tramming, I finally ended my frustration and bought an Edge Tool dual indicator tramming tool. That makes life a lot simpler.
 

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#23
The issue of the Y axis nut shifting and binding appears to be a relatively rare problem -- this is the first time I've heard the complaint. It's possible there's a manufacturing defect in there. Maybe the pocket for the nut is poorly machined, the nut itself is defective in some way, or ??? (fill in the blank).
 

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9t8z28

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#25
delete post.

Thanks! In the interim, I was reading a lot of forum posts looking specifically to see if anyone had ever added a rear support bearing on their Y axis screw. I didn't find anything about that, except that many feel this is an acceptable way to do it, supporting the screw only at the crank end. My personal opinion disagrees. But I did find mention of the axis screws being 5/8-20 (on the ones with inch conversion screws).

Here is a link to a slew of information on threads, including where I discovered that there were no 20 TPI listed under standard ACME sizes, but several 20 TPI across the range of UNS thread. Thus, knowing we have 5/8 screws now, I concluded they are UNS 5/8-20. A tap for that thread is available on McMaster-Carr if anyone needs one. Also the 37/64 drill bit required for it.

https://www.gewinde-normen.de/en/20-un-thread.html
The issue of the Y axis nut shifting and binding appears to be a relatively rare problem -- this is the first time I've heard the complaint. It's possible there's a manufacturing defect in there. Maybe the pocket for the nut is poorly machined, the nut itself is defective in some way, or ??? (fill in the blank).
 

9t8z28

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#26
I have heard many complaints about the same issue. I’ve had the same issue but was able to adjust It to decrese the binding but it still gets tight at the extent of it’s travel toward the operator
The issue of the Y axis nut shifting and binding appears to be a relatively rare problem -- this is the first time I've heard the complaint. It's possible there's a manufacturing defect in there. Maybe the pocket for the nut is poorly machined, the nut itself is defective in some way, or ??? (fill in the blank).
 

MetalMuncher

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#27
The issue of the Y axis nut shifting and binding appears to be a relatively rare problem -- this is the first time I've heard the complaint. It's possible there's a manufacturing defect in there. Maybe the pocket for the nut is poorly machined, the nut itself is defective in some way, or ??? (fill in the blank).
(All of the above). ;)

The first Y Axis nut I originally found inside this mill, back in 2004 shortly after buying it, had incredibly bad looking threads. The best way to describe them would be a comparison to how Play Dough will crack and separate when extruded if it is too dry. That is literally how the threads looked. I replaced it with a new nut from LMS, which was in much better shape. But Y axis binding has always been a problem on this mill, and I've seen it mentioned several times over the years in forums. Likely one reason people developed the thrust bearing modifications available for the Y axis.

Still, now that I think about it, the X axis on the stock X2 table, lacking any addition of a power feed, also has its tail end unsupported. But the length of that axis is so much longer that probably helps prevent the nut jamming in its slot. The biggest problem I ever had with the X axis was very poorly machined gib strips. Eventually I lapped and polished both axis gib strips, which helped smooth things a lot. They looked pretty rough from the factory, and it made trying to get uniform tension across the X axis range impossible. I had an ammeter mounted on my first X axis power feed, which liked to die if the load got too high. The power draw would vary by double the lowest amount (.2 to .4A) as the entire axis was traveled under no load at all, until I lapped the strip.
 

homebrewed

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#28
What I was saying (apparently unclearly) is that the issue of the nut shifting is unusual in my experience. It is very common for the feed screw/nut to get tight when the table is close to the end of its travel, but then it loosens back up when you move the table back. This is an alignment issue -- the nut doesn't line up exactly with the mounting block.

That's why it is recommended to loosen/retighten both the feed screw nut and mounting block so they can get closer in alignment. Manufacturing tolerances could be such that this is only partially successful for a given machine.
 

MetalMuncher

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#29
I have heard many complaints about the same issue. I’ve had the same issue but was able to adjust It to decrese the binding but it still gets tight at the extent of it’s travel toward the operator
My current magic formula for setting those 3 screws involves working between them, as well as adjusting the angle up and down on the screw shaft, while trying to hold the nut centered. But it never seems to stay as I adjust it, even if I tighten the nut retainer screw rather tight. Over time, and moving the table fore and back, the nut manages to start moving, and then gets a mind of it's own. I've thought about trying boring a detent on one side of the nut for the screw to sit in. If that didn't work I could flip the nut around and undo it. One thing I haven't done is, when the nut binds up, pull the table off the carriage and see exactly what the nut did. I'm usually in the middle of a job and want to finish it, so I readjust the nut and continue on. I should probably take the time to do that once. It might help me see a means of prevention.
 

9t8z28

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#30
Agreed, this is when mine binds, in the middle of a job but it’s only when the Y-axis is almost at its end. Speaking of, can you post a picture of your spacer ?
My current magic formula for setting those 3 screws involves working between them, as well as adjusting the angle up and down on the screw shaft, while trying to hold the nut centered. But it never seems to stay as I adjust it, even if I tighten the nut retainer screw rather tight. Over time, and moving the table fore and back, the nut manages to start moving, and then gets a mind of it's own. I've thought about trying boring a detent on one side of the nut for the screw to sit in. If that didn't work I could flip the nut around and undo it. One thing I haven't done is, when the nut binds up, pull the table off the carriage and see exactly what the nut did. I'm usually in the middle of a job and want to finish it, so I readjust the nut and continue on. I should probably take the time to do that once. It might help me see a means of prevention.
 
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