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  1. #1
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    Default How to zero a universal mill table?

    I struck a problem a little while ago when doing some stub milling on the Victoria U2 universal mill. When taking more than one pass with a face mill in the horizontal spindle, I was left with a step between the two cuts, I didn't measure the step but it was visibly obvious and definitely enough to catch a fingernail on. I puzzled over it at the time and then I had a bit of a lightbulb moment a few days ago, I think the table X axis is not square to the spindle. Can anyone tell me the correct procedure for setting the table square to the horizontal spindle? Haven't been able to find any info on this anywhere. I'm thinking that if I mount an indicator on the table so that it probes the face of the column, moving the table across in the X axis will sweep the indicator across the machined face of the column. I tried this today and I get a difference of .007" across the column which is about a foot or so wide. Before I go and make the adjustment based on that I thought I'd better check that I'm not missing something. Also this assumes that the face of the column is square to the spindle- is this a reasonable assumption? I guess I could check that by turning an indicator in the spindle with the tip on the column face, like tramming a vertical head.
    Given that these machines are intended to be swiveled to various angles for spiral milling etc, there must be a right way to set it back to zero, let me know if I'm barking up the wrong tree.

  2. #2
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    I agree with John, it should be measured from the spindle.
    If it were me, I'd mount a DTI onto the spindle shaft, and run it along the T slot.
    Kryn
    To grow old is mandatory, growing up is optional.

  3. #3
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    You know, I've never come up with a good method myself. I usually just line up the graduations and assume it is good. One day when it is critical I'll work it out fully. In the mean time a few thoughts -

    You will have to put an indicator on the table and measure across the column face. An indicator in the spindle and measuring on the table assumes that the table edge (or the T slot) is spot on parallel to the slide axis. After 50 years of use, I would not trust those bits on mine without checking as over the years they get dinged up, machined, crashed and so on. Your mill could well be the same.

    There are also some assumptions to be made about the machine construction. Ideally the short axis (Y?) should be parallel with the spindle axis, and the long axis (X) should be square to that. It could well be within Schlesinger limits but is unlikely to be perfect. I think what I would do/ should do in the future is make up a straight edge (maybe 8 to 10" long?) on an adaptor (in my case ISO 40), with the straight edge square to the spindle axis. That should give you a decent surface to work to that you know is square to the spindle and flat enough not to flick too much.

    As an added bonus, you can then secure a square to it and with an indicator on the table, check how square the short axis is to the spindle. You may have to make a choice as to whether you want X and Y spot on square to each other and the spindle axis slightly off or the spindle aligned with one of the axis and live with the other being slightly off.

    Michael

  4. #4
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    Thanks for the replies Kryn and Michael. I've been nutting this out since I realised that the table was not properly squared; I hate to say it but I think you've both hit the same stumbling block that I was tripping over until I had the lightbulb come on. The problem with mounting an indicator in the spindle and running the table past it is not how straight the edges- or T slots- of the table are, it's that the table will move in a straight line past the indicator regardless of what angle the table is set to. So the indicator definitely has to be mounted to the table, and passed across something that is dead square to the spindle axis. I think that theoretically the face of the column should be dead square to the spindle axis. Also the Y axis movement should be parallel to the spindle axis. This I can check by mounting a long arbor in the spindle and an indicator on the table, moving the table in Y and sweeping the indicator along the arbor, rotating the arbor and using averages to compensate for any non-straightness in the arbor itself. Of course there is no way to adjust the Y-axis, if it's not parallel to the spindle.
    I have the vertical milling attachment in place at the moment and it is a pain to install and remove; I may have to complete a couple of small jobs with it before I get it out of the way and perform the above checks.

    Given that these machines were used in industry for a generation and that swiveling the table is all part of using the machine, I'm surprised how difficult it's been to find a procedure for setting it.

  5. #5
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    I just measure from the back of the table to the ways on the column on each side.
    Cheers, shed

  6. #6
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    Im not super familiar with swiveling table horizontals like you are talking about but commonly on grinders with swing tables there is a very snug fitting dowel or taper pin what is used to reset a hard zero. Do any Universal's have these?

  7. #7
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    Few different ways, Put a square on the table and indicate off it to the cross slide ways.

    Put a parallel on the table, parallel with the table and use a tramming setup off the spindle, like you would a vertical mill to get the head square.
    Gold, the colour of choice for the discerning person.

  8. #8
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    Quote Originally Posted by .RC. View Post
    Few different ways, Put a square on the table and indicate off it to the cross slide ways.
    This is what I do. In fact it's one of the uses I put one of my hand-scraped precision right angle squares to.

    Pity I didn't do it *before* I machined a bunch of castings. Would have been a lot less scraping. I hate scraping ATM.

    PDW

  9. #9
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    Working old flogged machines and getting accurate results can be difficult.
    For example if you sqaure across the ways and indicate the square you will need to lock the y at each end of the travel when indicating, when you lock it the measurement will change and as you usualy need to lock the y when cutting in x direction this needs to be taken into account. Same thing if you are to lock your z when cutting. Then again depending on how worn or how well your machine has been made locking on unlocking the z can move the table out of parallel to the spindle or the z ways.
    So in essence you have to know the failings of your machine and work around them.
    Measuring from the back of the table to the z ways with a caliper with the y locked is the quickest easiest and accurate enough way that i have found without trying complicate things and introducing other errors by going the long way around.
    shed

  10. #10
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    Don't know if this helps, it's from a book called Machine tool testing by DR. GEO. SCHLESINGER. I've attached the PDF file.Mill Testing-min.pdf

  11. #11
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    Use the same method on the horisontal universal mill as we do on a turret mill to set head square to table. Hold a suitable length bar on the spindle to attach a dti. Rotate spindle side to side through 180 degrees to check squareness of table. That is the normal procedure in all the workshops I've been in during the last 50 odd years. Most likely in your "Culley" text book or any other trade books used by TAFE for apprentices.

  12. #12
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    Quote Originally Posted by Karl Robbers View Post
    Don't know if this helps, it's from a book called Machine tool testing by DR. GEO. SCHLESINGER. I've attached the PDF file.Mill Testing-min.pdf
    I decided to take a heap of measurements of my mill based on the info in that link- thankyou Karl- and found that the machine is pretty good except for a sag in the knee, the Y axis falls away from the spindle axis by 0.12mm in 200mm, that's about nine times the permissible error in the given specs. If I ever get a spare year I guess I could scrape the machine in but for now I will live with it.
    I tried two methods of aligning the table, firstly by mounting a DTI on the table and passing it across the face of the column.
    indicate from table across column face.jpg

    I got it to .007mm across the 210mm sweep by this method then took a test cut with a face mill in the horizontal spindle; it was clearly still no good as the leading edge cut but the trailing edge cleared.
    I tried the second method of aligning the table, mounted a carpenter's level to the spindle to provide a rigid arm
    setup for indicating spindle to rear face of table- level clamped to spindle.jpg

    and with an indicator mounted to the outboard end of the level, measured to the rear face of the table at each end by swinging the level through the arc of the spindle movement. The two reference points were 1140mm apart and I got the readings to within 0.01mm and called it good.
    indicating spindle to rear face of table.jpg

    I took another test cut with the same face mill and this time got a nice cross-hatched pattern which was encouraging.
    I've been sceptical of this method as the rear face of the table did not appear to me to be a precision surface; however after scraping off the several layers of paint that have been slapped on it over the decades it is indeed a machined surface and the results of tramming from here are good.

    I re-cut the job that originally showed up the problem, I'm milling a flat face on each side of an overarm casting as part of a frankenmill project. Due to the way I need to mount this casting on the mill, the cuts on each side need to be made in two passes in the Z-axis by moving the knee. When I did this a few weeks ago I got a distinct step between the two passes. I took another skim on it yesterday after zeroing the table and ended up with a flat surface. In the photo below you can see the machined area at one end of the casting- it's set up to do the opposite side. Two cheek plates will be attached to the casting at those positions, and an adaptor plate to mount a J-head will be attached to the front end of the overarm by fixing to those cheek plates.
    overarm clamped for milling 2.jpg

  13. #13
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    Quote Originally Posted by Pete O View Post

    I re-cut the job that originally showed up the problem, I'm milling a flat face on each side of an overarm casting as part of a frankenmill project. Due to the way I need to mount this casting on the mill, the cuts on each side need to be made in two passes in the Z-axis by moving the knee. When I did this a few weeks ago I got a distinct step between the two passes. I took another skim on it yesterday after zeroing the table and ended up with a flat surface. In the photo below you can see the machined area at one end of the casting- it's set up to do the opposite side. Two cheek plates will be attached to the casting at those positions, and an adaptor plate to mount a J-head will be attached to the front end of the overarm by fixing to those cheek plates.
    I'll be interested to see how you go with this - I've been planning on doing the same thing for a number of years now, just had other priorities to date. Given the rigidity & geared feeds on the Vicky mill I expect I'll sell my B/port once I get to this. The main thing I use it for nowadays is a glorified router - had a bunch of dumb bell blocks in it today milling away the excess (nice bit of huon pine too for you timber tragics - I've got heaps of it).

    The spare J head has been sitting in the pallet racking waiting its turn for quite a while.....

    PDW

  14. #14
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    Quote Originally Posted by PDW View Post
    I'll be interested to see how you go with this - I've been planning on doing the same thing for a number of years now, just had other priorities to date. Given the rigidity & geared feeds on the Vicky mill I expect I'll sell my B/port once I get to this. The main thing I use it for nowadays is a glorified router - had a bunch of dumb bell blocks in it today milling away the excess (nice bit of huon pine too for you timber tragics - I've got heaps of it).

    The spare J head has been sitting in the pallet racking waiting its turn for quite a while.....


    PDW
    I've definitely felt the lack of a quill on the vertical attachment of the U2, been very envious of proper vertical mills. When a friend from another forum mentioned a J-head that needed a home (as well as a rebuild) I jumped at it. I think it should be a good combination; as you say, the U2 is a very rigid machine. The versatility of the J head plus a 4hp horizontal spindle, power feeds on all axes, universal table. Just hope I can do a good enough job to do the machine justice. I bought a second, incomplete U2 machine as a parts donor a couple of years ago as mine was missing some components of the power feed; this means I have a spare overarm that I can do the conversion work on, if I stuff it up I haven't ruined the mill.

    Don't hold your breath to see this thing finished though. I might post a thread on the project, if so it'll be sure to disappear off the bottom of the page several times before getting finished.

  15. #15
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    Quote Originally Posted by Pete O View Post
    Don't hold your breath to see this thing finished though. I might post a thread on the project, if so it'll be sure to disappear off the bottom of the page several times before getting finished.
    Not a problem - given my project backlog I expect to get to this one about 2050, assuming I live that long....

    Though I actually did get something (more or less) finished last week - decent re-scrape of the top slide & cross slide ways on my big Monarch lathe. Now I don't want to see a scraper again for at least 12 months.

    I use my U2 quite a bit as-is but I've never mounted its vertical head. Mostly I use decent face mills in the horizontal spindle with stuff mounted on angle plates and the like. I've a ton of side & face cutters as well and some nice slabbing cutters for cast iron. You can remove a lot of metal quite quickly this way, far more than with a wimpy B/port J head.

    PDW

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