# help adjusting gibs on pm45



## dball (Dec 8, 2012)

just got a pm45  a few months ago and never used a mill before this.I was having a problem with my y axis it was geting tight checked for chips in the threads under the saddle none at all! I spoke with matt and was told to adjust the gibs i told him i have 0 knoledge on it so i played with them and got no where.Im paranoid i messed it up seeing as i have no idea at all on what im doing and dont want to mess up my mill thanks for any help


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## Ray C (Dec 8, 2012)

Hang on about an hour.  I'm knee deep in chips and need to finish something.  Will take some pics for you to explain the gib system.

Ray


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## Richard King (Dec 8, 2012)

It sounds like the gib screws are loose letting the gib go to deep into the taper and making it tight.   I am not familiar with the PM brand, but I looked it up on the net and it looks like a table top mill.   I would hope you have the saddle lock loose and that's not the issue.   Take off the front way wiper and rear Y or saddle way wipers and look for the gib screws.( I see from the other pictures your machine does not have wipers...  So be sure to keep your ways wiped free of dirt and chips.    A Bridgeports only has one in the front as it has a notch milled in the big end for the screw, and other machines have one in front and one in back. 

When you find it loosen it a 1/2 turn and see if it gets looser if not loosen it another 1/2 turn.  You should have .0005" to .001" clearance to hold the lubrication oil..or is it grease on yours?  There has to be a gap so the metal has a thin layer of lube or it will wear due to to tight a gib. The best way to check the gap is to mount a mag base on the bed and a .0005" dial indicator on the saddle and check the "Shake" or clearance ..I am going to attach a picture so you know what I mean.  But you push and let go, then pull and let go.  the machine will spring a litle, so let go and read the indicator.   It' hard to explain, so hopefully you will understand from the pics.   You can always call me.   I am a machine tool builder / rebuilder and fit gibs all the time.  When we scrape the gibs we make this test on both ends and scrape the gibs so they have the same gap (shake) on both ends, so the taper is the same.   This picture was taken in new machine factory in Taiwan where I was teaching machine building and we were scraping the head to the column of a VMC, but the principal is the same for a bed to saddle of your mill.  You can always call me if you need advice.  My cell is 651 338 8141.   Rich


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## Ray C (Dec 8, 2012)

OK, don't freak-out, it's easy to deal with...

First, look at the picture of the locking paddles and notice the bottom right one.  That paddle often interferes with the base hold-down bolt below it and when you crank backward in the Y direction, the paddle hits the bolt and tightens the gib.  Unscrew the gib lock to remove the paddle and grind the paddle down short enough so it won't interfere anymore.  Then put it back in.


The weight of the table is supported by the bed and there is no adjustment there.  So, if your bed is see-sawing, there's nothing you can do -but they get it right at the factory.  Mine is 2 years old and it holds under 0.0002 from end to end.  It's rock solid from the zero to 10" mark and shoots-up 0.0002 at the extreme ends (between 10 and 12") where you wouldn't normally mount anything.  That measurement can only be checked by putting a TDI on the spindle and running the table back and forth.  The same is true for both X and Y direction.

Now for your problem.  Everything hereon describes the X direction but it's the same thing for Y...

Next, look at the pic of the gib position screw with my finger pointing at it.  There is one at the other side too and before turning one in, the other must be backed-out out first.  The gib is long and tapered and it adjusts the table rotation -meaning, if you crank out all the way in the X direction, it goes in a perfectly straight line instead of going off at a slight angle.  (hope that makes sense).

Now, look at the picture with the TDI.  It's fixed at the bed and indicating off the table.  Clean that surface and run the table back/forth.  The needle shouldn't move (much).  If it's off by more than what you feel is acceptable, you need to push the gib to the left or right and capture it into position using the gib position screws.  Give one side a twist out and the other a twist in, to make your adjustment then, snug the paddles then, back them off a little.  Check the travel a couple times.  When you first crank the wheel, the TDI will show a little deflection because things will shift a little due to the tiny amount of tolerance in the fit.  What you're looking for is stability in the needle over most of the travel.  Keep adjusting the gib one way or the other until you're satisfied.

Don't go nuts with it...  The table is 24" long and if you have 0.001" deflection from end to end, you have a non-linearity of 0.0024 degree.  -Good luck noticing it.  Machining to a tenth of a degree is hard.  Hundredth of a degree... -Very, very difficult.  Thousandth of a degree?  Only in your wildest dreams...

Let me know if you want to know how to do the top side...

Good luck...

Ray

PS:  I know what you're going to ask me...  How close is my X-Y table linearity set?  Close as possible which is about 0.0005 from 0 to 12" in either direction.  Once you get this set, it doesn't really ever change -that I'm aware of.


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## Ray C (Dec 8, 2012)

Hi Rich,

I'm confused about something...  I thought the whole purpose of scraping was so you can essentially run two surfaces at near-zero tolerance.  For example, the 2 ways on my surface grinder.  One is flat the other is V-shaped -both are scraped.  The table is about 150lbs, the mag chuck is 75lbs + whatever the piece weighs.  Last week, I did an antique cylinder head that was cast iron -had to weigh 90 lbs...  That's 315 lbs squeezing those ways together and the only place the oil can go is in the little grooves of the scraping...  No doubt in my mind that if I were foolish enough to completely degrease the ways, the table wouldn't budge with that kind of weight on it.

Maybe there's different kind of gib setups.  The gibs on this machine bear no weight.  They only apply force to pull the table down into contact with the bed and also serve to let the table move precisely in a given axial direction.

Anyhow, the machine's seen 2 years of good use and things look to be in mint shape.  I can see no sign of wear pattern -at all.  This machine has those BB-indent-oilers and I assume they lead to channels and cavities that lead to the scraping.  I also give those a couple drops of oil every day I use the machine.  I'm always blown away at how well these things work.  -That and how piston rings work so well in engine cylinders.  -Amazing really...

Ray





Richard King said:


> It sounds like the gib screws are loose letting the gib go to deep into the taper and making it tight.   I am not familiar with the PM brand, but I looked it up on the net and it looks like a table top mill.   I would hope you have the saddle lock loose and that's not the issue.   Take off the front way wiper and rear Y or saddle way wipers and look for the gib screws.( I see from the other pictures your machine does not have wipers...  So be sure to keep your ways wiped free of dirt and chips.    A Bridgeports only has one in the front as it has a notch milled in the big end for the screw, and other machines have one in front and one in back.
> 
> When you find it loosen it a 1/2 turn and see if it gets looser if not loosen it another 1/2 turn.  You should have .0005" to .001" clearance to hold the lubrication oil..or is it grease on yours?  There has to be a gap so the metal has a thin layer of lube or it will wear due to to tight a gib. The best way to check the gap is to mount a mag base on the bed and a .0005" dial indicator on the saddle and check the "Shake" or clearance ..I am going to attach a picture so you know what I mean.  But you push and let go, then pull and let go.  the machine will spring a litle, so let go and read the indicator.   It' hard to explain, so hopefully you will understand from the pics.   You can always call me.   I am a machine tool builder / rebuilder and fit gibs all the time.  When we scrape the gibs we make this test on both ends and scrape the gibs so they have the same gap (shake) on both ends, so the taper is the same.   This picture was taken in new machine factory in Taiwan where I was teaching machine building and we were scraping the head to the column of a VMC, but the principal is the same for a bed to saddle of your mill.  You can always call me if you need advice.  My cell is 651 338 8141.   Rich
> 
> ...


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## Richard King (Dec 9, 2012)

Ray,
I you were to pull the table you would see scraping which are small pockets that hold oil and those groves are called oil groves and they are designed to distribute the oil to the ways as he able travels  plus many are 1/2 mooned on one side. Most grinders are scraped lower in the center 1/3 of it's length on the bottom approx .0005 to .001" low which I call a puddle of oil.  It's a small reservoir that holds the oil ready to flow when you move the table.  The machines are designed for square inches of coverage and 1/2 the surface is lower or has scraped marks and the area between the scrape marks are called high spots that carry the weight plus there is a thin film of oil on op of them.  All machines wear do to dirt, lack of the proper oil, heavy use, etc and as it wears the high spots and low spots disapear and increasing the friction because there is no puddles.  Worn ways start looking scratched and it stars to shutter which is called stick-slip. Many new machines use a green Teflon and bronze impregnated plastic strip called Turcite that is glued to the ways, so less oil is needed and it eliminates the stick slip.    Many of the cheaper machines have wider clearance because they are not scraped as accurately.  A friend of min has a machine similar to yours and it was out .008" before we scraped it.  He said he had to leave .004" shake in order to move the table (X).  He used way oil too.   

I wrote this for my Forum "Way Scraping and Restoration" a few weeks ago:

*What is Scraping?*

Hi Everyone,

I wrote this few days ago on another site I write on and thought I would share it with you. 

Someone asked "What is scraping anyway?"

my Answer:

It is the precision fitting of ways on a machine tools and it provides even oil lubrication film on the ways (also used on Babbit and bronze bushings bearings, etc. Over the years it has been discovered that hand fitting or scraping of the ways is the most precise method so machines wear and function properly. We use a carbide tipped "scraper" that resembles a file or wood chisel. We scrape pockets approximately .0002" deep to form weight carrying high spots and the low spots are for oil. A good scraping job resembles a chess / checker board one spot is high and the next spot is low. Our goal is to get 50% high spots to carry the weight and 50% low spots for oil. 

We fit the machine way clearance from .0002" to .001" so oil can squeeze between both sides of the way surfaces so the ways move smoothly and do not wear. We also test the squareness and alignment using levels and gages.

It's a trade, but it is pretty easy to learn if your mechanically inclined and have a good teacher. Scraping is easy but knowing where to scrape and how much to take off is the hard part. I also say in my DVD, start small on a surface plate and then start an easy project like a lathe compound. 

Most conventional machines like lathes and mills are scraped to an accuracy of .0002" per 12" and straight edges and jig bore super precision machines are scraped to .00005" per 12". The high spots are classified as High Points per 1 sq. inch and on the conventional machine we try to get 12 to 20 point per inch (PPI) and jig bores / super precision we try to get 38 to 42 PPI If you ever look at the ways of a Bridgeport you see 1/2 moon spots, well those have 2 functions, the main being extra deep oil pockets plus they look nice. they are approx .002" deep. 

I was talking to a reader and he asked about a Scraping Seminar in the UK sometime, so I just wrote a friend of mine in NE England who works at a used machinery company and asked him is he could host a class next summer. I await his response. So all who live in the UK pass the word and let me know if your interested in learning to Hand / BIAX power scrape, 1/2 moon flake and learn to repair your machines. When we have more info I will advertise it on the area Tony talked about.

Mechanics that scrape are called Machine tool builders, fitters, or machine rebuilders. I am a Journeyman Machine Tool Rebuilder. I apprenticed under my Father who lerned from a German born Journeyman during WW2 a a Defense Plant here in MN. I started to rebuild machines and scrape when I was a child...50 years ago...I am now 62 and have been teaching scraping for over 30 years for companies like GM, Timken, Cummins, John Deere, worked with several new machine builders in the USA, Europe and Asia; Spinner, Hardinge, Kent, Paragon, Hartford, Sharpe, Chevilier, plus taught several hobbyists and home machine shop owners. 

I hope to help all of you repair your machine tools on his site. I like this site as there are no bullies allowed as seen on other sites. 

There are others who teach scraping, I am one of them.​


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## Ray C (Dec 9, 2012)

Rich,

I think scraping is cool, really cool in-fact and when I saw it done, it appealed to me.  Sadly though, I spent a lifetime doing something foolish (martial arts and other forms of combat) and as a result of millions of impacts, broken bones etc. my wrists, knuckles and finger joints (and other body parts) are in bad shape.  10 minutes of scraping would probably trigger a case of tendonosis that would last for months.  How do you get past that?  I'm guessing it's got to be rough on the hands and forearms?

I saw and read the first week of that thread but maybe I missed some parts about how gibs are used to make contact.  I'll go back and read more. 

BTW:  Next time I take the surface grinder table off, I'll take photos of the scraping.  Geeze, it's like a work of art.  I have a working shop and do my best to keep things clean and swarf free and wipe down the machines daily.  Once a year, I do a greater level of disassembly for obvious reasons.  -Sorry, you just missed the last photo-op for the surface grinder ways.

Also, yes, the PM has scraped table ways and given the importance of keeping it primed with lube, I'm half tempted to put oil caps instead of those BB-Indent oil holes.  The one in the rear is not as accessible as the front.

Ray


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## Richard King (Dec 9, 2012)

Ray C said:


> Rich,
> 
> I think scraping is cool, really cool in-fact and when I saw it done, it appealed to me.  Sadly though, I spent a lifetime doing something foolish (martial arts and other forms of combat) and as a result of millions of impacts, broken bones etc. my wrists, knuckles and finger joints (and other body parts) are in bad shape.  10 minutes of scraping would probably trigger a case of tendonosis that would last for months.  How do you get past that?  I'm guessing it's got to be rough on the hands and forearms?
> 
> ...



The  gib is an adjustable way if you think about it.  It needs oil just like the others.  Next time you take a gib out, stone it to be sure there are no burrs on it.  Many times the ends get a burr on it where the gib screws are.  Stone or file both sides.  Then lay it on a surface plate and see if you can slide in a .001"  feeler gage under it, flip it over and see if its flat too.  Then take your forefinger and thumb and grab one end.  slowly slide it away from you about 1" and then pull it back towards you about 2".  look for the hinge or pivot point.  when the gib is flat it will hinge about 30% from each side, then use the other hand and do the same thing...That's called "the rotation of points"   Just think about a teeter totter and how if you slid in say .010" feeler gage under the center of the gib and hinged it, it would rotate or pivot directly in the middle.  Even though the gib is tapered each side has to be flat.  Gibs bends as they wear. 
More on that another time.   But you need clearance so you have an oil film between the gib in your case the dovetail way.   I have a friend who is 55 an  black belt..something degree...lol...and he limps and has issues moving around...but he still works out and competes.  
Have a nice day...it's snowing here.


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## GaryK (Dec 13, 2012)

Richard King said:


> Ray,
> I you were to pull the table you would see scraping which are small pockets that hold oil and those groves are called oil groves and they are designed to distribute the oil to the ways as he able travels  plus many are 1/2 mooned on one side. Most grinders are scraped lower in the center 1/3 of it's length on the bottom approx .0005 to .001" low which I call a puddle of oil.  It's a small reservoir that holds the oil ready to flow when you move the table.  The machines are designed for square inches of coverage and 1/2 the surface is lower or has scraped marks and the area between the scrape marks are called high spots that carry the weight plus there is a thin film of oil on op of them.  All machines wear do to dirt, lack of the proper oil, heavy use, etc and as it wears the high spots and low spots disapear and increasing the friction because there is no puddles.  Worn ways start looking scratched and it stars to shutter which is called stick-slip. Many new machines use a green Teflon and bronze impregnated plastic strip called Turcite that is glued to the ways, so less oil is needed and it eliminates the stick slip.    Many of the cheaper machines have wider clearance because they are not scraped as accurately.  A friend of min has a machine similar to yours and it was out .008" before we scraped it.  He said he had to leave .004" shake in order to move the table (X).  He used way oil too.
> 
> I wrote this for my Forum "Way Scraping and Restoration" a few weeks ago:
> ...



  If you really wanted to get into scraping get the book (If you can find it) "Machine Tool Reconditioning and Application of Hand Scraping" by Edward F. Connelly. Over 500 pages covering every topic.
Excellent book.

Gary


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