# Pm 940v



## nighthawkFmobil (Sep 12, 2021)

***Edit below*** ive since addressed the issues discussed in this thread. Hopefully things hold up because im really liking this mill.

Alright i need help again hah.

Im going through testing mill alignment. Mill table movement is flat in the x and the Y. I know you're not really supposed to tram these vertical mills without locking the gibbs but i just did to see if i could. I was able to get th z aligned to the column with tilt and nod according to a 7" piece of 3/4" drill rod. There's so much slop in z gibbs i decided to see what i could get without them. Next I aligned the column to the table without locks and with shims erased nod and had little side to side. The tilt i had to the table could have been adjusted with a better level(room is not flat) or some head tlilt it was like .002,  possibly would have lost some head to column tilt but anyways. Fun was over and i had to do it again since people dont typically mill without z locked.

Getting head to column tilt wasnt all that bad. I can consistently hit my tilt less than a thou over 6" or so with the locks on. Id say as i lock it in place im getting like .002"-.003" X movement with the gibb screw pretty tight.

Now when i go to check the head to column Y nod its all over the place. Im about .007" out. When i lock the gibbs the thing can nod around .010" just from locking the gibbs(seems a bit much). As the bar decends it gets further away telling me the head is nodding with locks on haha(im no sherlock).

Maybe someone can point out something im overlooking. Is the gibb lock slop normal? Just shim it and deal with it?

***edit***

I put a square on the table to test the squareness of xy and im not getting variation of over .0005" along 6" so I'm going to call that good.

So far ive used an 3/8 endmill on some 6061 and some cold rolled steel with very good results. Did a little drilling in the steel as well and that went well too.

At this point im pretty happy with the machine. I think my initial misalignment/excess movement when locking the gibs on the Z was due to the gib being very touchy as well as well as the paint that had gathered on some of the mating surfaces. Partially my fault i suppose.

My only issue at this point is the head will kind of slip a bit when traveling at the bottom of the z. Its really in a spot that ill most like never be milling but im going to have to figure that out. Will look into it more asap. Not sure its even a repeatable issue just something i noticed once.

Overall im quite thrilled with the machine. Even if i did have to take it apart and clean it. I knew i was going to want to do that anyways. I hopr this all holds up. Should translate to some pretty flat and square cuts


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## Tipton1965 (Sep 12, 2021)

Did you adjust the gibbs before starting all this alignment?


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## nighthawkFmobil (Sep 12, 2021)

Ive been running them snug. Im not going all out cranking them but ive been keeping them snug.


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## Tipton1965 (Sep 12, 2021)

nighthawkFmobil said:


> Ive been running them snug. Im not going all out cranking them but ive been keeping them snug.


Are you talking about the gibb adjustment screws or the locks?


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## nighthawkFmobil (Sep 12, 2021)

The gibb adjustment screw.


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## nighthawkFmobil (Sep 12, 2021)

I leave the locks loose. I've always wondered if people ride them a bit though.


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## Tipton1965 (Sep 12, 2021)

nighthawkFmobil said:


> The gibb adjustment screw.


Well, if you're getting .010" nod from locking the gibb then it sounds like the gibb needs more adjustment.


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## nighthawkFmobil (Sep 12, 2021)

Im getting more like .003 nod. I decided to use the stem of the test indicator to try and catch the high spot instead of the ball and it was making my numbers go crazy. Im using the ball and now im around .003 nod which sounds more reasonable to shim. The nod from tightening gibbs is a lot less testing with the ball too. For now it seems like the stem was throwing my numbers off. Ill update.


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## nighthawkFmobil (Sep 12, 2021)

All of my prior measurements besides the confusing round were off the ball. Idk why i switched it up. Its appears i can take some of the nod out by clamping the upper gibb locks first.  Im consistently getting less than .002 variation in Y nod now. And my lock slop is about .002. Maybe too much mill alignment for me this weekend.


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## davidpbest (Sep 13, 2021)

This might help.   Have a look.


__
		https://flic.kr/p/2mpC66D


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## nighthawkFmobil (Sep 13, 2021)

After the good results i double and triple checked. Tipton was right it has to be something with the gibs. Even when the gib is adjusted so tight that i dont feel comfortable manually raising the head theres still a bunch of play with the locks. The variation changes so the gib seems to be moving around. 

Ill have to call pm later and ask for their procedure because the manual doesnt have anything about that going on. Anyone have an easy way to get the Z axis gib off this beast without removing the head?


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## yota (Sep 13, 2021)

lathe gibbs I've pulled apart have recesses where the screws go in.  you have to back the screws way out, or fully out.  can you support the head with a large block of wood and remove the screws and then pull it out or tap it out with some type of thinner drive plate?


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## yota (Sep 13, 2021)

then again, if there is debris in there causing the problem you'd want to take it completely off to clean everything properly.


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## nighthawkFmobil (Sep 13, 2021)

I agree yota. I wouldnt doubt some kind of paint being in there. Overspray was abundant.  Its hard to make it out in the pics but the gib on top(first pic) had a more shallow angle for the adjustment screw seat. The one on the bottom is a lot more steep. It looks like it had been broken. Probably pushing on the gib uneven. Idk i dont think it would make it move as much as it does when i lock it. Unless it just cant adjust at all...


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## davidpbest (Sep 13, 2021)

Make yourself a saddle to hold the head.   Below is a photo of the one I made for my RF-45.   Once the head is off and to the side, you should find it easy enough to remove the gib and get the backing plate off of the column.  Then you can check for paint and body filler overspray on the dovetails, etc.  As for the gib itself, I would stone it, get all the burrs removed, and then blue it up and test how it seats on the two dovetail surfaces - you can do that without the head mounted.  You might have to do some filing to get it to fit well, but it's worth the effort.  Have you checked that the XY table X and Y axis run perpendicular to each other as covered in the video I posted earlier?


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## nighthawkFmobil (Sep 13, 2021)

davidpbest said:


> Make yourself a saddle to hold the head.   Below is a photo of the one I made for my RF-45.   Once the head is off and to the side, you should find it easy enough to remove the gib and get the backing plate off of the column.  Then you can check for paint and body filler overspray on the dovetails, etc.  As for the gib itself, I would stone it, get all the burrs removed, and then blue it up and test how it seats on the two dovetail surfaces - you can do that without the head mounted.  You might have to do some filing to get it to fit well, but it's worth the effort.  Have you checked that the XY table X and Y axis run perpendicular to each other as covered in the video I posted earlier?
> 
> View attachment 378295


David, i just ordered a precision square today. Cant wait to get it. Seems to make alignment faster. Definitely should have taken care of that first. Now i see why you said that Haha.  

Its seems like im going to be taking good ol mothra apart. Maybe i should wait for the square first...


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## nighthawkFmobil (Sep 13, 2021)

Sweet cradle btw. That's a cool idea.


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## Janderso (Sep 13, 2021)

davidpbest said:


> This might help.   Have a look.
> 
> 
> __
> https://flic.kr/p/2mpC66D


David,
I just noticed your signature -"Kappa 400 Xmotion sliding table saw" and 'I'm single".
I got a good belly laugh out of that one.
I checked out that saw. Holy com man, that is sweet.


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## davidpbest (Sep 13, 2021)

Janderso said:


> David,
> I just noticed your signature -"Kappa 400 Xmotion sliding table saw" and 'I'm single".
> I got a good belly laugh out of that one.
> I checked out that saw. Holy com man, that is sweet.


Hahaha.   I'm moderator of the Felder Ownsers Group forum.  And I wrote the book on how to set up and commission their saws: http://www.davidpbest.com/Publications.htm 

Shop Tour Video is here:  




The Kappa 400 xMotion is a nice machine.


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## yota (Sep 13, 2021)

nighthawkFmobil said:


> I agree yota. I wouldnt doubt some kind of paint being in there. Overspray was abundant.  Its hard to make it out in the pics but the gib on top(first pic) had a more shallow angle for the adjustment screw seat. The one on the bottom is a lot more steep. It looks like it had been broken. Probably pushing on the gib uneven. Idk i dont think it would make it move as much as it does when i lock it. Unless it just cant adjust at all...


that sure looks like a crack in the cast iron.


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## yota (Sep 13, 2021)

oh, if that's the gibb.  def would think that should be a straight line.


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## nighthawkFmobil (Sep 13, 2021)

It does, i wonder how that happened. I  overlooked that.


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## nighthawkFmobil (Sep 13, 2021)

Its cracked pretty good. I can fit a small pick about 3/4"down into it. Its kind of a coned shaped hole with the big end to the top of the carriage. the other corners are nice and straigt. Darn

Would that be enough to cause the shifting I'm experiencing?


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## Christianstark (Sep 13, 2021)

nighthawkFmobil said:


> Its cracked pretty good. I can fit a small pick about 3/4"down into it. Its kind of a coned shaped hole with the big end to the top of the carriage. the other corners are nice and straigt. Darn
> 
> Would that be enough to cause the shifting I'm experiencing?


I thought it was the end of the gibb. I think the paint gooped on the way it is is making it look like an irregular crack, but it’s the gibb I’m 95% sure.


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## nighthawkFmobil (Sep 13, 2021)

Christianstark said:


> I thought it was the end of the gibb. I think the paint gooped on the way it is is making it look like an irregular crack, but it’s the gibb I’m 95% sure.


Theres either a crack or its made like that one purpose. I think he was originally talking about the gib but all of the other four courners are straight where as this one has a small chunk taken out for whatever reason.


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## nighthawkFmobil (Sep 13, 2021)

Other four corners are more like this.


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## Christianstark (Sep 13, 2021)

nighthawkFmobil said:


> Theres either a crack or its made like that one purpose. I think he was originally talking about the gib but all of the other four courners are straight where as this one has a small chunk taken out for whatever reason.


Looks like it’s made that way to me…but the paint job on that machine is FUGLY. I hope the mechanicals on this get sorted.

edit. Saw the second picture. I retract my statement above that it looks like it was made that way. I maintain that the paint job is awful. Is this par for the course with Chinese castings? Looks like the casting was chipped?


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## nighthawkFmobil (Sep 13, 2021)

Christianstark said:


> Looks like it’s made that way to me…but the paint job on that machine is FUGLY. I hope the mechanicals on this get sorted.
> 
> edit. Saw the second picture. I retract my statement above that it looks like it was made that way. I maintain that the paint job is awful. Is this par for the course with Chinese castings? Looks like the casting was chipped?


Yeah its definitely chipped.


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## yota (Sep 14, 2021)

I would scrape all the paint off the top.  if its just the edge of the gib it should be a straight line,


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## ptrotter (Sep 14, 2021)

That is the way these gibs look, you are looking at the end of the gib. It has a notch in it where the screw comes up and pushes it upward. Support the head with a block. Then remove both the top and bottom gib screws and you should be able to push the gib down from the top using a small rod to remove it.  You will then see what the gib really looks like.  I have done this several times on my 940V, it is quite easy.


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## Christianstark (Sep 14, 2021)

ptrotter said:


> That is the way these gibs look, you are looking at the end of the gib. It has a notch in it where the screw comes up and pushes it upward. Support the head with a block. Then remove both the top and bottom gib screws and you should be able to push the gib down from the top using a small rod to remove it.  You will then see what the gib really looks like.  I have done this several times on my 940V, it is quite easy.


The chip they are referring to is on the casting, and not the gib. I think it is cosmetic, and not causing the nod reported upon tightening the gibs.


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## ptrotter (Sep 14, 2021)

Yes, I see what you are looking at.  These are not finished well but he ground surfaces seem reasonably ok. They seem to paint they after they are put together so the paint chips as soon as something moves.  I took mine completely apart, striped all the filler and paint off, and repainted it.


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## nighthawkFmobil (Sep 14, 2021)

ptrotter said:


> Yes, I see what you are looking at.  These are not finished well but he ground surfaces seem reasonably ok. They seem to paint they after they are put together so the paint chips as soon as something moves.  I took mine completely apart, striped all the filler and paint off, and repainted it.


The paint isnt really a concern with me at this point. As long as i have an accurate machine im happy. The table seems super flat across both travels so hopefully it all works out.


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## Tipton1965 (Sep 14, 2021)

I would take that machine completely apart and clean and inspect everything.  And if you go that far you might as well remove all the factory filler and do a repaint.  When I had my 833TV it seemed like every time I turned around there was a new chip in the body of the machine.  Had I kept it I most likely would have repainted it.


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## B2 (Sep 14, 2021)

Hi Folks,  

I folks, I purchased a PM940M CNC a few years ago.  I was so naive I missed a bunch of things at  the beginning.  However, I know a lot about the z-axis gib and ways now and am still trying to work out some fixes.  Some folks get a better machine than mine.....  PM is good about helping but somethings they do not have control over.  Lots of things were wrong with my machine.  Yes, it nods too.  We are all seduced by the large working ranges of this machine, but I think this is also part of its problems.   At this stage it if had not been so much trouble to get into my basement (basically had to disassemble the table, stand and take the CNC electronics and enclosure off to move it in in pieces) I would get something else.  I may yet, but I am still using it.  

Clamp the head to the ways before knocking the gib out from the bottom.  Blocking is a safety factor, but once the gib is out the head can roll, yaw and pitch a lot.  I don't think it will fall off of the ways, but it is close.  I have had my gib out many times and have order materials to make my own ... maybe.  (PM, Matt, offered to make a new one for me, so I cannot fault them.)  I have a very large C clamp for holding the head to the column.  However, probably some bar clamp would work.  I did knock the pain off of the soft bondo they cover the whole thing in.  (The cast iron is not very good, rather sandy.  If you think other wise just try tapping a hole in the column.  You can do it but I recommend you use a drill that is considerably smaller than the normal steel tap.  I think this bad material is why some of the smaller screws in my machine are so loose.  The screw threads are smaller than the grains of the cast iron!)

If you loosen both ends of the gib screws and then crank the head up the gib will slide down and get tighter.  If you then crank it down the gib sometimes stays high and starts to come out the top.  Probably depends on number of factors, but that is what mind does.  Anyway, this is one way to get the gib loose.  Then insert a rod up from the bottom and push the gib out.  A tap may be needed, but by clamping the head to the ways the gib is no longer holding things.  

As far as the clamps I used them to keep my head from falling for a while.  However, when I took the gib out, it was very beat up from the screw ends.  Some pretty deep holes...and they were not all in one place like they should be if the gib was not moving around!

Fundamentally the machine is designed wrong or under designed for the head weight or the head is just too heavy.  Then there is the poor QC in China.  The 904M is head is heavy.  Via my measurements and others it is between 250 and 300 pounds.  The the column for the vertical ways is heavy, but too light weight for this head.  

At first I thought the ways were not uniformly cut the length of the column so that the way spacing varied as you go up and down.  This maybe still the case in my machine as I still need to precisely measure across the width of the ways.  Precise means 0.001" or less across the way width as one goes up and down.  This is hard to measure once the head and motor are on unless you have special tools to fit behind them.  I believe that mine varies more than this.  What one really wants to do is measure this distance just behind the motor as the motor is moved up and down.  Hence, my next paragraph.  

The second issue is due to the strength and design of the column. The concept model is as follows:   I now am thinking that due to the head forces,  the ways actually move towards each other in the center region where the ball nut support passes through the U shape of the column.  At the top and bottom, where there is no travel, the column has the steel in between the ways so is stronger.  So if the U shape bows together at the ways due to the head weight then the ways/gib are looser in the middle that at the top or bottom.  On my CNC machine the little stepper's powered off cogging  and the gib friction will hold the head up when at the top and bottom, but the whole thing walks down when in the middle.  (Not good when the power goes off.   The stepper is strong enough to hold when the power is on, but if the gib is too tight then steps are missed on the way up...  too loose and maybe there are extra steps on the way down...  Not good for a CNC machine. )   So this behavior is because the gibs are adjusted to be tight at the top or bottom.  In the middle they are loose and the head also nods!!!! So far the only solution that I possible have is to reduce the weight or to support it some other way.  Currently, I am thinking that the ways bow inward about 0.003-0.005 in the center of the distance between the U shape becoming a box, at the ends.   This represents tightening the giby by a lot.    The head saddle,  contacts the ways at the top and the bottom as it tries to nod, rotates due to the torque.  Hence, the bottom rests against the column and is ok, but the top pulls on the ways causing the ways to deflect towards each other.  There is a lot of torque on the saddle.   The gib does not really contact the ways uniformly up and down the 11 inches or so.  In my case the gib does not really contact well towards the bottom at all.  In fact, at the bottom it rattles around unless its clamped by the screw.  

My gib was not made correctly, but more importantly it was cut too short when installed.  The top, bottom and length of the gib is made with two angles. One to try to fit the thickness of the hole and the other is to try to fit the width.  Unfortunately, this is difficult to do down the length.  I think the procedure is to make a gib that is extra long.  Put it in to tight and then cut the top off so that it will fit the screw.  Then cut the bottom off to fit that screw.  Since the gib tappers both in the thickness and width directions, and at different rates, it is virtually impossible to get it right at both ends, unless it was very closely made to the hole to start with.  In my case, there is so much room in the gib at the bottom that the screw does not even make contact to the end, but as it goes up it pinches the gib in the width direction rather than along the length.  Hence it becomes a clamp point.  This is the way it arrived from the factory so the head definitely nodded at all positions as the gib was not holding anything tight except at that one point. The normal clamps would bend the gib in an also clamp.  So I made a larger washer with a corner on it to stick out in to the way area of the end of the gib to push on it upward.  It works but the screw thread hole is sloppy and even this is not great. 

After taking the gib out I carefully measure down the gib hole as to its width across the diagonal (corners of the gib).  This was not easy to do as I had to take a very long thin piece of tapered width, 0.020 thick, sheet metal and insert it into the hold until it just fit, measure its length into the gib hole and its width at the end.  I then cut it off and measure the next distance down into the hole. Repeat a lot.   I did this every 1/2 inch or so.  to get the hole profile to compare to the gib.  I repeated this a couple more times just to convince myself I did it right.  My gib was cut off too short by about 3/4 inches which corresponded to a gib to way spacing of about 0.005" when the gib was fully inserted and could go no farther.  It never fit.   In addition to not being thick enough, the gib is not wide enough as mentioned above.  So out came the shims to be attached to the gib.  If finally got it tight but then the bowing of ways is still a problem.  I have all of these measurement in a spread sheet if they would help anyone.  

There are other problems which are just poor workmanship.  One of them:  When the mill arrived the nuts, washers, bearings, holding the bottom of the lead screw had fallen off and fortunately were still on the pallet.  I had no idea where they went, but figure it out after using the machine a while.  I initially thought maybe this was why the head was falling, but now I think it was just another contributor.  See the beginning of this posting string to see the parts.  I am not the only one who found them to be a problem.   https://www.hobby-machinist.com/threads/pm-940m-cnc-z-axis-bearings.59538/#post-608202 


Good luck.  
Dave

PS. I am thinking about putting some pulleys on the top of the column, hooking cables to the head, routing them through the pulleys and using the cables to the dangling some counter weights down the back of the column .  I would only need about 300#s of weights!  Maybe some air springs instead of more weight on the poor column and swing around.


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## davidpbest (Sep 14, 2021)

Watch the first few minutes of this video - James found similar issues with his PM-940:


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## yota (Sep 14, 2021)

sad but good information.  the bearing on the bottom of the Z axis lead screw on my brand new 932M was almost off when I got it.  I took it off, cleaned and re-greased and re-installed.  there is a washer with tabs between the 2 nuts under the bearing.  I tapped one of the tabs down into the slot on the bottom nut so it can't back off again.    the screw holding the worm gear on the hand crank shaft was also loose.


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## nighthawkFmobil (Sep 14, 2021)

Appreciate the reply dave. Theres a lot i can kearn from your experience.  I was surprised when i first opened her up and the top hinge to the electronics cabinet was laying on the ground.


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## nighthawkFmobil (Sep 14, 2021)

Are you guys referring to the bearing assembly that attached to the z handle? Is it the same on the manual machines?


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## yota (Sep 14, 2021)

no, the flat bearing with upper and lower races and 2 nuts at the very bottom of the leadscrew.


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## yota (Sep 14, 2021)

this is the bolt that was never tightened at the factory on mine.  am I right to assume that the 940 and 932 are very similar other than the table size?


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## Weldingrod1 (Sep 14, 2021)

Btw, if you have shop air you could use an air cylinder as your counterbalance... bigger, but you dont have to worry about it leaking down over time.

Sent from my SM-G892A using Tapatalk


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## nighthawkFmobil (Sep 14, 2021)

Yes mine is exactly like that from what ive seen. Do you have some kind of rear access? 

Does the z screw have to be removed in ordet to get that assembly out?


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## B2 (Sep 14, 2021)

davidpbest said:


> Watch the first few minutes of this video - James found similar issues with his PM-940:


Thanks,  Yes, I know James caught it soon enough to trade his in for a knee mill.  I doubt that he was seeing all  the things I have observed, but he did not like the issues.  I did pay for a CNC version, which it PM quit selling.  I spoke to Matt, at PM, a year or so ago and I know he has been trying to find a CNC mill that he wants to sell, but there is nothing on his web site yet.  Guess he has not found one yet.  

I live in Pittsburgh so I have been to his facility several times. The folks are very helpful.   I purchased a PM1440GT lathe from them here while back and have posted my VFD conversion documents Saturday.  So the lathe conversion has kept me from worrying much about the 940 issues.  I have just been living with it.


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## B2 (Sep 14, 2021)

nighthawkFmobil said:


> Yes mine is exactly like that from what ive seen. Do you have some kind of rear access?
> 
> Does the z screw have to be removed in ordet to get that assembly out?


My machine's side looks like your picture.  I took the huge CNC electronics box (~200#s) off the back so I have the same view as @yota picture. However, because of my CNC version I have a small z-axis crank. The nut, washer, and bearings can be reached from the hole in the back but it is tight working. I did not want to take the crank assembly off so have not tried to do so. However, others have. I am not for sure if the lead screw has to be removed to do so, but I doubt it. In my case, I would have to take the mill off the stand to have head room to remove the lead screw so....... The basement joist are just over head. If you want to see the nuts etc more clearly see the start of the post thread I sent. @yota picture with the arrow is the correct location. You can also see my mill. I have it on wheels, but block it when I am happy with the location. I have pulled it out a couple of times. Because of the caster height, I can slip a car jack under the stand to take it on and off the blocks.

By the way, in the CNC version, when the mill goes up and down that crank handle slaps back and forth a short distance, but its very loud and annoying.   It sounds like something is broken.   Hence others with CNC have removed it.  Because my the head on my machine falls, I use the crank all of the time.  Before I turn the mill power off I tie a bungie cord to the handle to keep it from turning.  After my experience with the way locks/clamps I do not use them.


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## B2 (Sep 14, 2021)

Weldingrod1 said:


> Btw, if you have shop air you could use an air cylinder as your counterbalance... bigger, but you dont have to worry about it leaking down over time.
> 
> Sent from my SM-G892A using Tapatalk


Thanks.  No air cylinder available.  No head room to spare either.  I have not yet found room to mount  cylinder on the front or sides yet.    But this is why I am thinking air spring "closers" (not openers) instead of weights.  I could mount the closers to the vertical column back with the cables and pulleys going over the top.  However, I have not followed up and found the right size closers yet.


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## yota (Sep 14, 2021)

nighthawkFmobil said:


> Yes mine is exactly like that from what ive seen. Do you have some kind of rear access?
> 
> Does the z screw have to be removed in ordet to get that assembly out?


the bearing can be removed easily by itself.  it looks like the crank handle assembly will not come out with out removing the Z leadscrew.  I'm not positive but it looks like the Z leadscrew has to come out from the bottom of the column.


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## nighthawkFmobil (Sep 14, 2021)

yota said:


> the bearing can be removed easily by itself.  it looks like the crank handle assembly will not come out with out removing the Z leadscrew.  I'm not positive but it looks like the Z leadscrew has to come out from the bottom of the column.


Is there something up top blocking it? Was thinking it could be possible to move z screw up just enough to get handle assembly out.


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## nighthawkFmobil (Sep 14, 2021)

Initial messaging with pm states this is normal behaviour for a mill to unpredictably nod in
the Y and shift or tilt in the X along the z axis. Ill have to look more into this but it seems odd a 5k$ mill cant consistently sit within at least .003 of perpendicularity to the table.

For now ill just have to keep cleaning it up and checking it out. Hopefully it gets better.


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## yota (Sep 14, 2021)

nighthawkFmobil said:


> Is there something up top blocking it? Was thinking it could be possible to move z screw up just enough to get handle assembly out.


the lead screw has a section at the bottom that is threaded to work with the worm gear on the hand crank.  It did not look to me like you could get that section through the casting that holds the leadscrew which is above that section.  it only looked like it could come out from below but I was not looking hard at it as I did not need to remove it.  you will have to look at it.


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## B2 (Sep 15, 2021)

nighthawkFmobil said:


> Initial messaging with pm states this is normal behaviour for a mill to unpredictably nod in
> the Y and shift or tilt in the X along the z axis. Ill have to look more into this but it seems odd a 5k$ mill cant consistently sit within at least .003 of perpendicularity to the table.
> 
> For now ill just have to keep cleaning it up and checking it out. Hopefully it gets better.


I agree with you about the nodding etc.  Others have much better results.  If your gib actually fits and you tighten it us really well the slop in the motion will decrease, at least in the y direction.  I did this just to test it out.  However, if you do this in the center of the vertical then don't try to move the head up and down too far as the ways will get really tight as you approach the top and bottom.   I was fearful that I might actually crack the saddle if it got too tight and then cranked the head up high.  It will be tighter at the top and the bottom z- axis range of motion because the ways do not bend (as much?) there.

If you really want to know if the lead screw has to come out, you might contact @ptrotter , or just look at his posts, as he took the lead screw out and replaced his lead screws as he rebuilt the machine into a CNC.  He took on the task of stripping all the whole surface of the machine and repainting it too!  This meant that he basically took it all apart including removing the vertical column.  https://www.hobby-machinist.com/threads/new-pm-940v.87161/page-5#post-827110


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## yota (Sep 15, 2021)

it would be cool to disassemble and bead blast one of these to see what the castings really look like.  and do a real paint job.


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## nighthawkFmobil (Sep 15, 2021)

Thanks david, it was a cool tool so i thought id give it a try. Seems to work great.


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## nighthawkFmobil (Sep 15, 2021)

Initial inspection of gibs wasnt too bad. Theres some paint that did make it on to the end of one and the backside. Not optimistic that alone will get me where i want.

Are the tapered seats for the adjustment screws ok? The one in first picture is hardly there and the 2nd looks pretty beat up. Not sure it can do its job properly with the gibs tightened unevenly.


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## nighthawkFmobil (Sep 15, 2021)

The head mounting surface has a bunch of paint or some kind of crud. The z carriage has at least paint and some other crud on the flat part that rides the ways. Ill have to figure out how to get the z base plate off.


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## Christianstark (Sep 15, 2021)

That second gib does not look like it has a good enough surface for the adjusting screw to apply force in the direction needed to slide the gib vertically, and instead looks like the force would be pushing just the end of the gib diagonally into the dovetail. Am I seeing this correctly?


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## nighthawkFmobil (Sep 15, 2021)

Christianstark said:


> That second gib does not look like it has a good enough surface for the adjusting screw to apply force in the direction needed to slide the gib vertically, and instead looks like the force would be pushing just the end of the gib diagonally into the dovetail. Am I seeing this correctly?


Yeah it doesnt seem useful. Its totally different from the other one. Im not sure i can take the carriage off without removing lead screw but it really needs to come off because i can see paint and crud.


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## yota (Sep 15, 2021)

have you taken that giant electrical box off to look inside the back of the column?


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## nighthawkFmobil (Sep 15, 2021)

yota said:


> have you taken that giant electrical box off to look inside the back of the column?


No, is that the only way to take the z saddle off?


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## yota (Sep 15, 2021)

pretty sure.  you wanted to remove the crank mechanism anyway.  and check the lower bearings are not coming loose.    in for a penny, in for a pound? 

 but

there have to be guys who converted one of these to CNC and changed to ballscrews who could tell you exactly what to do to get the leadscrew out.


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## nighthawkFmobil (Sep 15, 2021)

Ptrotter had his z saddle off before his lead screw so there has to be a way to loosen the nut from the "nut bracket"


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## yota (Sep 15, 2021)

looking at the dwg you attached.   if you can get gear 56 off the hand crank shaft then you could remove bearing set 61 thru 64 from the bottom of the lead screw.  then you have to remove upper bearing 61 and gear 56 which is keyed to the leadscrew shaft.   if you do all that then the leadscrew will come out the top of the column and the hand crank mechanism can then be removed..      you will have to remove the big electrical box to get access through the back of the column to do all of that unless you can do it from the front.  I think the leadscrew will be in your way trying to do it from the front.


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## nighthawkFmobil (Sep 15, 2021)

yota said:


> looking at the dwg you attached.   if you can get gear 56 off the hand crank shaft then you could removed bearing set 61 thru 64 from the bottom of the lead screw.  then you have to remove upper bearing 61 and gear 56 which is keyed to the leadscrew shaft.   if you do all that then the leadscrew will come out the top of the column and the hand crank mechanism can then be removed..      you will have to remove the big electrical box to get access through the back of the column to do all of that unless you can do it from the front.  I think the leadscrew will be in your way trying to do it from the front.


Yes thats exactly what i was thinking just trying to figure out the sequence. Thanks


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## ptrotter (Sep 15, 2021)

I would be careful about removing the Z lead screw and crank.  I had a lot of trouble doing that and I knew I was not going to put it back in since I was converting it to CNC. You don't need to remove the leadscrew to remove the saddle.


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## ptrotter (Sep 15, 2021)

Here is picture of mine with most of it apart.


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## ptrotter (Sep 15, 2021)

yota said:


> it would be cool to disassemble and bead blast one of these to see what the castings really look like.  and do a real paint job.


I completely stripped all the paint and filler off my mill.  It was a lot of work.  The finish is not great and I had to resurface it with Bondo to make it look good.  The result is very nice but it was probably not worth the effort.  If I wasn't taking it apart to do a CNC conversion, I would not do it again.


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## B2 (Sep 15, 2021)

nighthawkFmobil said:


> Initial inspection of gibs wasnt too bad. Theres some paint that did make it on to the end of one and the backside. Not optimistic that alone will get me where i want.
> 
> Are the tapered seats for the adjustment screws ok? The one in first picture is hardly there and the 2nd looks pretty beat up. Not sure it can do its job properly with the gibs tightened unevenly.


Hi  @nighthawkFmobil

WRT to the gib.  The big end, (top), of your gib looks typical.  The small end (bottom), of the gib which is chewed off is similar to mine, but not as bad.  As I said mine did not work at all as the screw pushes it into the way making it a clamping force, not a gib.  I made a washer with a finger sticking out to catch the gib end.  At the time I was cutting some thin aluminum and it was clamped to my backer board anyway so I just used this Al. It was thin, so I may have used to layers in the gib hole.  I cannot recall.   However, something harder would work better.  

Just for you..... I have a bridge... for sale...

I will attach two files for you that may be useful.  One is just a drawing of the washer.  The other has Gcode.  In addition I will through in another gcode which you can simulate if you want.... it for the instrument panel I was making.    I made 4 washers at the time out of this thin Al.   The made the tab a bit large as I figured I was going to have to file by hand to get it to fit anyway.   So the ID was to fit the bolt and the OD was to fit the hole where the gib screw head was receding into. That hole on the 940 was not well defined (sloppy) so I made it as large as I could and have it still fit.  The finger on it sticks out and I just tried to make it larger than needed so I could file it down.    I was actually cutting a much more complex panel plate with lots of odd shaped holes and just put the gib washer on the end of the Al that I was cutting.  I put a holding tab on the circle edge so that the part would not tear out as it was being cut.  

I will stick the Gcode I wrote for the process, but it is way overly complex and may not make a lot of sense to you.... as I said I was cutting other parts at the same time.  I was using a 2mm diameter end mill.  Anyway, I was taking very small cuts so the thin parts would not get bent as they came loose or curled out of the cut material.     I will also attach my Mach3 Gcode text files for these cuts and another for the washers..... which you can simulate to see what it looks like.  This gcode looks extremely complex, but maybe you can extract something that you might want to run.  The reason for the complexity is that I actually did the parts design in Visio,  then wrote a program in Excell that allowed me to shift and rotate any individual part to a location in the X-Y plane and places its holding tabs at any angle. The Excel program automatically generated the Gcode, which I then made into a text file.   Some of the parts also had flats on the circles as well as the holding tabs.... so the Excell was used to calculate where the cutter went from making a circle to making a straight line or where the tool was lifted to make the holding tab... as a function of how the part was shifted in X-Y or rotated.  Anyway, I will share it, along with the Gcode for the washers.  Maybe you can run the washer Gcode just as it is written, but you may have to make a leap of faith!!!

Not to be incomplete, I will also attach a 4th file, which should be the same as the 12Circles-2Rects.... file but with comments.  When I had put all these comments in the file it would not simulate in the MillWizard software as it had too many characters!  I cannot recall if it would actually run in Mach3.  The MillWizard simulator is actually a lot different from the actual Mach3 software.  

Dave


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## davidpbest (Sep 15, 2021)

yota said:


> it would be cool to disassemble and bead blast one of these to see what the castings really look like.  and do a real paint job.


The castings are very rough and faired out with filler that is soft and chalky.  Every bump and the paint chips off.  I completely disassembled my PM mill and lathe, stripped them down to metal, used real Bondo to smooth them out and then primed and painted with industrial paint and so glad I did.  I upgraded all the fasteners in the process too. 









						Paint the Mill Project
					

Explore this photo album by David Best on Flickr!




					flic.kr


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## nighthawkFmobil (Sep 15, 2021)

Finally got the saddle off haha. The trick is to remove the z motor and loosen the z screw mounting plate underneath.  From there i had to lift the z screw and saddle with 2 arms, then reach down and pull hand piece out of its pocket and after that you have enough play to get the saddle free. Oh boy that was fun.


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## nighthawkFmobil (Sep 15, 2021)

Taking the bolts out of this plate allows you to lift the entire thing. Id take the head off unless your david best and you can just strong arm the entire thing.


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## nighthawkFmobil (Sep 15, 2021)

B2 said:


> Hi  @nighthawkFmobil
> 
> WRT to the gib.  The big end, (top), of your gib looks typical.  The small end (bottom), of the gib which is chewed off is similar to mine, but not as bad.  As I said mine did not work at all as the screw pushes it into the way making it a clamping force, not a gib.  I made a washer with a finger sticking out to catch the gib end.  At the time I was cutting some thin aluminum and it was clamped to my backer board anyway so I just used this Al. It was thin, so I may have used to layers in the gib hole.  I cannot recall.   However, something harder would work better.
> 
> ...


Yes, thanks for sharing. Love to see what otger people are up to with drawings and g code. Had no idea people used excel to generate g code. Ill have to look inti that more.


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## B2 (Sep 16, 2021)

Hi  @nighthawkFmobil
Yes, I have used Excel several times. I use it to do the calculations and then organize things.   I usually use variables when I do and one of the problems with the Mach3 is that the available variables are not well defined.  It is a bit of a guessing game.    Most all of the 9000's, a large fraction of the 8000s, and 7000s are available.  You can see what I used in the gcode.   You can put the line numbers, GCommands X, Y, Z etc in the columns and then a row becomes a line of G code.  Each column has meaning and then in another column you grab each of the cells that you want in the final line and use the CONCATENATE command to gather the cell entries, add spaces, commas, ),   etc.  
Example:  CONCATENATE(B178,C178," ",D178," ",E178," ",F178," ",G178," ",H178," ",I178," ", J178," ",K178," ",L178," ",M178," ",N178," ",O178," [",P178,"] (",Q178,")")

The cell entries can be numbers, text, etc.  What ever makes sense in G-code.  However, in Excel the numbers will carry too many digits etc for Gcode so you need to make those entries the right number format by limiting the number of digits with a command like rounding.  
Example:  =+ROUND(E77,4) .  

If you decide you want to try your hand at something like this I suggest you start with a simple object.  

In the example code that I posted, I took one page to make an object shape.  Based upon another page  which carries the info for the particular object: shape, size, X-Y location, tab locations on the object, number of tabs, tab widths, flats on a circle, rotation angle etc would feed into the particular page where the characteristics were used to manipulated the values math wise.    This way one set ups multiple pages to handle multiple objects.   this page generates the G-code text for that particular object.  

Then I use a macro system to gather up the various G-codes for each object into a set of G-codes.  In this page subroutines are used to call each object to be cut via the main program.  


All of this seems rather complex and is, but once written one can create sets of objects with different parameters, location, size, etc.  pretty fast and can easily change these if you want a different layout.   So on the Gcode I posted for you you can quickly see the set of routines for each of the objects being cut out.   But only the final results are in the posting.  If you really want to dig deep I could send you an Excel program... but it may take longer to figure it out than to write one for your self.  

Obviously, if you are only doing one object this might be a lot easier to just draw it in a CAD package that automatically generates Gcode.  Of course if you want to change one object this is not too hard if you only have one object, but if you have a lot it gets to be a little more tedious.  

Dave


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## B2 (Sep 16, 2021)

BTW  @nighthawkFmobil

If you are interested, you can see the panel I made using the posted Gcode, or one similar to it, in my posting on the VFD conversion. Photo 15a.  I think.    Note the 12 circles and 2 rectangles for the instrument cluster switches, digital meters, lights, screws (at the corners) etc.  With a Gcode simulator you can compare the picture to the simulation.   The 940 nodding and back lash has prevented me from even trying to do any small size engraving.  So the lettering on this is from a label (tape) making machine.  


B2 said:


> More Pictures 3



Dave


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## nighthawkFmobil (Sep 16, 2021)

B2 said:


> BTW  @nighthawkFmobil
> 
> If you are interested, you can see the panel I made using the posted Gcode, or one similar to it, in my posting on the VFD conversion. Photo 15a.  I think.    Note the 12 circles and 2 rectangles for the instrument cluster switches, digital meters, lights, screws (at the corners) etc.  With a Gcode simulator you can compare the picture to the simulation.   The 940 nodding and back lash has prevented me from even trying to do any small size engraving.  So the lettering on this is from a label (tape) making machine.
> 
> ...


I was just anout to ask. What is your 940 good at?


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## nighthawkFmobil (Sep 16, 2021)

I just got done putting everything back together.  My initial finding is the same result. Man, i put a lot of work in but owell. More testing in the next couple of days. I have a starrett square on the way to check squareness of xy


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## nighthawkFmobil (Sep 17, 2021)

I guess at this pount this has become somewhat of a journal.

After last nights post and this morning before work i did more test on the column and head. Overall the test were good. Im finding my magnetic indicator holder could be playing a factor. Im also finding my nod to be a heck of a lot less. Makes me winder if the gib wasnt seated properly.  

After cleaning everything up and getting it back together its definitely running a lot more smoothly.  For right now i have the gibs tight but im not sure its neccessary.  Probably going to do ankther 40 test lol then see if i can get the spindle to table within acceptability. Fingers crossed, i could use some hope right about now. Glad i got some.

 I think im realizing there's multiple factors with a machine like this when trying to achieve decent repeatability as well as smooth operation(how it feel manually) and function, aside from how nice and tight of a fit the dovetail/gib matches up. B2 you were right about the gib not being a clamping force. I learned much about that.  Is it acceptable to put loctite on gibs? Not really confident enough in my adjustment but i could see it being helpful. Maybe a washer could have same effect in my situation


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## Christianstark (Sep 17, 2021)

nighthawkFmobil said:


> I guess at this pount this has become somewhat of a journal.
> 
> After last nights post and this morning before work i did more test on the column and head. Overall the test were good. Im finding my magnetic indicator holder could be playing a factor. Im also finding my nod to be a heck of a lot less. Makes me winder if the gib wasnt seated properly.
> 
> ...


When you say put loctite on the gibs, what do you mean specifically? Just curious, as I am still waiting for my machine, which is a Taiwanese machine.


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## nighthawkFmobil (Sep 17, 2021)

Christianstark said:


> When you say put loctite on the gibs, what do you mean specifically? Just curious, as I am still waiting for my machine, which is a Taiwanese machine.


Loctite in the gib adjustment screws sorry. One of my gibs had a cracked or reallly sloppy made screw head seat. It turns the gib into more of a clamping force instead of something that holds it in place so i cant tighten down on it much. Loctite could hold it in place 

What mill did you order?


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## yota (Sep 17, 2021)

why not have PM get you some new Gibs?    any way to drill and tap a for larger gib screw where the bad threads are?  I have read that the grainy structure of the chinese cast steel makes it difficult to tap.  maybe a helicoil?


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## Christianstark (Sep 17, 2021)

nighthawkFmobil said:


> Loctite in the gib adjustment screws sorry. One of my gibs had a cracked or reallly sloppy made screw head seat. It turns the gib into more of a clamping force instead of something that holds it in place so i cant tighten down on it much. Loctite could hold it in place
> 
> What mill did you order?


Ordered an 833TV. The ship it is on is sitting offshore near Seattle. Should dock today, and then it will be on a train for a few weeks en route to Pittsburg.

Why don't you use the mill to clean up the screw seat a bit, so it has better engagement? Yes, I do recognize the silliness of my suggestion. Just adding some levity to an annoying situation you are in. . Do the jib adjusting screws line up properly in the gib dimples? Is one off center? I was thinking the gib adjustment screws would have a jamb nut so lloctite was not necessary. You may consider swapping out those screws for a better set screw from McMaster? Would rounding the tip slightly help it read in the gib better, and apply a more uniform force?

Edit - I re-read the situation. The casting is the actual issue with the gib screw, and not the screw itself? I would talk to PM BEFORE you attempt to re-tap or helicoil that so they can advise, and you don't blow your warranty. Can you post a picture of the casting area where the gib screws go?


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## B2 (Sep 17, 2021)

nighthawkFmobil said:


> I guess at this pount this has become somewhat of a journal.
> 
> After last nights post and this morning before work i did more test on the column and head. Overall the test were good. Im finding my magnetic indicator holder could be playing a factor. Im also finding my nod to be a heck of a lot less. Makes me winder if the gib wasnt seated properly.
> 
> ...



NEVER LOCTITE!  

You will want to adjust it in the future.   The proper way to do this is to loosen the screw at the gib small end.  Then tighten from the big end until you get it where you want it.  Then tigthen the small end back up.  The gib is then held in the proper position by the clamping of the screws pinching the ends of the gib towards each other.   Hence my need for the washer with the finger sticking into the gib hole.  Not pinching toward the ways as is happens when the little end of the gib gets chewed off.  The way surface of the gib is scraped (certain amount of roughness) to leave grooves for it to hold oil.  This tends to prevent as much wear on the ways.  At least that is the theory.    I also realize that for flat surfaces only 3 points actually make contact at a time, unless one of the surfaces bends.  Think legs on a table.    After operation these points tend to wear down and become more flat to give more surface area of contact.  If the points are really high then the gib may need to be retigthened a bit.  

In my bad gib case, I removed the gib and laid a 0.005" shim along the non-way side to take up the space.  This moved the gib ends up where the top screw could be adjusted.  I then added the washer with the finger to the bottom screw to hold the gib from moving up and down in the saddle. 
The taper on my gib thickness is about 0.0088"/inch.  This means that a shim of 0.005 will cause the gib to be about 0.005/0.0088 ~0.57" higher.  I measure the taper directly from the bad gib as well as down the gib hole.   So for a shim I actually used a piece of Al tape which had adhesive on one side.  I put the adhesive against the gib (non-moving way) side.  So the Al was then toward the saddle clamps.  Not ideal as the clamps would cut right through it to the gib material, but I do not use these screw clamps anyway.  

So the gib is working until I made another and the mill works.  I have made a lot of thing, but many of them were before I realized I had such a bad gib!  My real issue is that the column ways spacing variation.  

My z-axis nodding is still about  0.001 to 0.0015.  I am sure I could make it smaller by tightening the gib, but then I would be concerned about the gib tightness when the head travels all the way up to the top of the Z-axis.  Fortunately, I seldom do that either.  

Dave


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## nighthawkFmobil (Sep 18, 2021)

B2 said:


> NEVER LOCTITE!
> 
> You will want to adjust it in the future.   The proper way to do this is to loosen the screw at the gib small end.  Then tighten from the big end until you get it where you want it.  Then tigthen the small end back up.  The gib is then held in the proper position by the clamping of the screws pinching the ends of the gib towards each other.   Hence my need for the washer with the finger sticking into the gib hole.  Not pinching toward the ways as is happens when the little end of the gib gets chewed off.  The way surface of the gib is scraped (certain amount of roughness) to leave grooves for it to hold oil.  This tends to prevent as much wear on the ways.  At least that is the theory.    I also realize that for flat surfaces only 3 points actually make contact at a time, unless one of the surfaces bends.  Think legs on a table.    After operation these points tend to wear down and become more flat to give more surface area of contact.  If the points are really high then the gib may need to be retigthened a bit.
> 
> ...


Im starting to get excited. With your help along with everyone else my 940 is consistently in my spec. Of course ill keep testing but i think ill finally run an endmill tomorrow.  Now that ive almost torn her totally down and have methods to move all the parts solo. I really hope this mill works out like my chinese 1228....


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## nighthawkFmobil (Sep 18, 2021)

My column was leaning to the right about .015 in comparison to my table. I shimmed the right side up and i think im finally aligned head to column and column to table.

There's a good amount of paint on the left side, the opposite side. of the one i shimmed.  It is about .015" . I think it would be worth it in the near future to  remove column and clean that paint off after seeing how the z saddle and head reacted to having nice slclean surfaces free of paint.


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## B2 (Sep 18, 2021)

Milling wood is a good first test. 

I think I mentioned it before, but WRT to shimming the column, you may want to also look at @ptrotter  posts again.  He took his completely apart before stripping and repainting, but I do not recall if he provided any insight to shimming the column.  I know he had too and he works hard to get things lined up right.  He also said that he found shims when he took it apart, but I don't think he kept them.  Maybe they were no good after coming apart.

Good luck.

Dave


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## nighthawkFmobil (Sep 25, 2021)

I put a square on the table to test the squareness of xy and im not getting variation of over .0005" along 6" so I'm going to call that good.

So far ive used an 3/8 endmill on some 6061 and some cold rolled steel with very good results. Did a little drilling in the steel as well and that went well too.

At this point im pretty happy with the machine. I think my initial misalignment/excess movement when locking the gibs on the Z was due to the gib being very touchy as well as well as the paint that had gathered on some of the mating surfaces. Partially my fault i suppose.

My only issue at this point is the head will kind of slip a bit when traveling at the bottom of the z. Its really in a spot that ill most like never be milling but im going to have to figure that out. Will look into it more asap. Not sure its even a repeatable issue just something i noticed once.

Overall im quite thrilled with the machine. Even if i did have to take it apart and clean it. I knew i was going to want to do that anyways. I hopr this all holds up. Should translate to some pretty flat and square cuts


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