Studer RHU 450 from the 1960s - Page 8
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  1. #141
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    Hi Richard,

    I decided to "prove" my findings by adding shims to compensate for the missing material under the swivel table. Here are the three shims, thickness 130 microns = 0.005", 75 microns = 0.003" and 25 microns = 0.001". None of these needed to be "forced" into place. This did improve the geometry, but not quite in the way that I had expected, so it was worthwhile.

    Here are the shims:



    This fixed the problem with the table drooping by 30-70 microns on the left. Here's a video showing that with these shims in place the swivel table is level. Indicator is 2 microns = 0.00008" per division (a bit less than a tenth).



    Next I aligned the swivel table parallel to the travel (you have to click on the link since PM only allows one embedded video per post!)

    Testing swivel table for parallel to travel

    Then I aligned the workhead so that the spindle axes was parallel to the travel. This is WITHOUT the tailstock (you have to click on the link since PM only allows one embedded video per post!)

    Testing workhead spindle for parallel to travel

    Finally in the next clip I engage and disengage the tailstock. The tailstock is off in horizontal position by about 7 microns = 0.0003" (you have to click on the link since PM only allows one embedded video per post!)

    Checking tailstock alignment front-to-back

    BUT the tailstock is still too high, by about 70 microns = 0.003" (not shown).

    Summary of the effect of shimming the swivel table to compensate for the missing material and make it flat:

    (1) The workstock spindle now droops down rather than pointing up. This is completely consistent with what I see on the surface plate. Before shimming the swivel table, the tilting of the swivel table top was making the workstock spindle point up!

    (2) The tailstock is now almost in the correct front-to-back alignment. Apparently the swivel table was twisting the workhead spindle axis when the table was clamped down.

    So it looks like the right order to fix things is:

    (a) Get swivel table ground flat and parallel

    (b) Scrape the bottom of workhead to get the spindle axis tilting slightly up

    (c) Scrape bottom of tailstock to lower it to the same height as the workhead spindle axis.

    I need to do step b before step c. Step a can happen anytime.
    Last edited by ballen; 05-22-2018 at 07:45 AM.

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  3. #142
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    It sounds like your machine is not worn in the Typical way.

    In most cases the TS is low and one scrapes the HS 2nd. But if it is lower now, you can just scrape TS. Also leave the Head-stock a couple of tenths low so as the TS wears the machine gets better, other then making them the same and as the TS wears, it gets worse. The height of the Workhead and Wheelhead all depends on the parts OD your going to grind. The bigger the part the spec doesn't need to be to precise. Be sure to scrape one side before grinding anything so it is pulled down solid. Shimming is not the best way. Rich
    Last edited by Richard King; 05-23-2018 at 10:24 AM.

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  5. #143
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    Hi Richard,

    Quote Originally Posted by Richard King View Post
    It sounds like your machine is not worn in the Typical way.
    Yes, I completely agree. And I think what I have found on the swivel table can not be "wear". It's ground, just not ground correctly! I think that the machine was restored or reconditioned, but at least a couple of mistakes were made in that process.

    In most cases the TS is low and one scrapes the HS 2nd. But if it is lower now, you can just scrape TS.
    I need to scrape both, because the axis of the HS spindle is pointing downwards, about 25 microns (0.001") in 150mm (6"). According to the Studer spec, it should be somewhere in between level and a maximum of 8 microns (0.0003") upwards-pointing in that distance. So first I need to fix the axis of the HS spindle, then I can do the TS last.

    Also leave the Head-stock a couple of tenths low so at the TS wears the machine gets better, other then making them the same and as the TS wears, it gets worse.
    OK, makes sense.

    The height of the Workhead and Wheelhead all depends on the parts OD your going to grind. The bigger the part the spec need to be to precise.
    I was thinking that it was the other way around, a small part would suffer more if the HS and wheelhead heights differ. Need to give this some more thought.

    Be sure to scrape one side before grinding. Shimming is not the best way.
    I am talking to a grinding shop in Germany that seems to know exactly what they are doing. So they may do this for me, because I don't have a surface plate big enough to print the table top.

    Richard, I really appreciate your advice. I am sure that you are scrambling to teach and travel and are squeezing this in "on the side" under time pressure. Nevertheless, if at some point you do have the time for it, I would be very grateful for answers to the questions in my earlier post #140.

    I'm happy with the progress that I am making. I think the machine will be in good shape very soon now, and I can spend my time using it rather than fixing/improving it.

  6. #144
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    Yeah I left out a word on my last one...I read it and fixed it...big difference... lol...

    Yeah I am exhausted and didn't check for typo's before hitting enter...lol. After the CA classes, 2 in a row..back to back with one day to drive to new city. Then we flew to Austin TX when my Brother-in-law sold us some of his $$ furniture as he is moving out of the country. Alex and I (my son) rented a truck and drove it home. 1700 miles in 1 1/2 days. I am happy to have helped you. :-) ...going to go read #140. Rich

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  8. #145
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    I'll write later...wife has me busy cleaning, being away for 15 days

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  10. #146
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    Hi Rich,

    Thanks for taking the time, after two weeks on the road that's a scarce commodity!!

    I started scraping the HS to shift the spindle angle from pointing down to pointing up. The flange is 160mm (6.5") in diameter and about 20mm (3/4") wide. The starting print was OK, contact most of the way around, not great. I split it into four parallel zones. Made three scraping passes on the zone farthest from the spindle nose, two passes on the next zone, one pass on the next zone, and no passes on the zone closes to the spindle nose. That reduced the downwards tilt by about half. Contact print is not as good as when I started. I figure I'll make another 3/2/1/0 pass to see if that gets the tilt to zero or a bit positive. If so, then I'll start scraping for better contact and worry about tuning the angle close to where I want it. Is that a good approach? Or after each 3/2/1/0 pass should I try to refine for good contact before doing another "tilt" pass?

    It's great to have all the tools at hand from scraping the oil pockets a few months ago. Having blades of different radii and the power hone to quickly sharpen them makes all the difference. Plus this is easier scraping, good access, a much smaller area, I can turn the HS around to get a good scraping angle or better lighting. I don't think it's going to take me more than a few hours spread over a couple of days to get the HS into reasonable alignment.

    Cheers,
    Bruce

    PS: You mentioned the weight of the test bar and "lift". I've calculated that the weight of the cylindrical portion outside of the taper is 2.3kg. So in measuring the tilt of the HS spindle, I hold a small digital scale under the end of the test bar and lift up until the scale indicates 1.15kg (half the weight). I think this should remove the effect of the test bar's weight "twisting" the spindle axis. If there is a better way, please tell me!
    Last edited by ballen; 05-24-2018 at 12:17 AM.

  11. #147
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    When the grinder was delivered, it was on a pallet which was almost exactly the same size as the base of the machine. Since I don't have lifting equipment in the right place, this made it a challenge to get the grinder off the pallet gracefully.

    Now that I am getting down to the fine points of adjusting the geometry, I thought it was important to get the machine level and standing on the correct points. So after some careful work last weekend it is safely down off the pallet and standing as designed. (Note that the swivel table is off being ground and I am scraping the underside of the work-head to remove the droop.)



    On the two front corners are adjustable screws with "ball ends" that go into ball sockets on the round feet. For a concrete floor that would be the end of the story, but my shop has 25mm OSB on 50mm of hard foam, so I have 300mm x 300mm (12" x 12") steel plates that are 15mm (5/8") thick spreading the load.

    On the two back corners, there are the same adjustable screw feet, but they are only there as a "safety" to protect against tipping:



    The load is carried (as per the manual) by a 70 x 100mm (3" x 4") steel block in the center. So the screws at the two rear corners are adjusted hand-tight then backed off a quarter turn.

    I have the machine level according to my antique-but-still-good South Bend 12" lathe level. Since the machine is on a 3-point support, that should be good enough.

    I wonder how long it has been since the machine was standing as it was intended to stand. Hopefully this will give the castings a chance to relax back into their original shape.

    One nice thing about this foot design is that it makes it easy to get a pallet jack under the machine if I want to move it. I tighten all four jacking screws to lift the machine 25mm (1") then hammer a couple of wooden wedges under one corner to support the load, back off the screw in that corner, and add a 25mm thick wooden square underneath the square steel foot. Repeat for the other three corners, then start the cycle again. In 15 minutes the machine base is 85mm = 3 1/2" off the ground and I can push a pallet jack under it to move it. To lower the machine, just reverse the procedure.
    Last edited by ballen; 06-01-2018 at 12:50 AM.

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  13. #148
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    I also teach about 3 Points as I believe their use is also a "Lost Art" Talk to an old timer and they will show you how they used 3 points to mount parts in mills and grinders and blocked around it. All the precision machines of old and many now use 3 points to stabilize and self level machine bases using 3 main points and smaller stabilizers much like your grinder base. I am so happy you have it off the skid...:-) Keep up the good work. Rich

  14. #149
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    Hi Richard,

    Quote Originally Posted by Richard King View Post
    Keep up the good work.
    Thanks! Things are going well.

    I got the bottom of the swivel table ground by a local place called Hoppeschliff. They did a good job. No more need for the shims on the left side and now when I traverse the table left/right I get about 3 microns of height variation (slightly more than 0.0001") over 500mm (24").

    I also step-scraped the bottom of the workhead to get the spindle level. I got to do it twice, because the first time I finished it I had the spindle level and good contact over 3/4 of the mounting ring, but none on the other 1/4 . I made a classic beginners mistake, and started refining too soon. So I had to rough-scrape the 3/4 region a few times until I got bearing all around then redid it. I found that if I sit close and get the light right, I can see the high points because the blue is thinner and they are surrounded by a darker blue ring.

    I also ground the mounting plate that goes between the workhead and the swivel table because it was not parallel. That also came out well, it's now parallel within 2 microns (better than 0.0001").



    Should I scrape oil pockets into the bottom of this mounting plate (the side shown above) where it bears on the swivel table?

    Now I am turning my focus to the tailstock. It's badly out of alignment in both axes. The good news is that the taper is concentric with the bore and with the barrel, and the barrel is a honed fit with no play. I found a serial number stamped under the tailstock (602) which is 15 larger than the rest of the machine (587) so they were not factory-matched. Fortunately I have a good MT2 test bar and it was easy to measure the tailstock both on the surface plate and on the machine itself. I was able to confirm the measurements on the machine by shimming. Here it is with the shims in place:



    To get the tailstock parallel in the horizontal and vertical axes will require removing 0.08mm = 0.003" from the left side of the bottom (tapering to zero on the right) and removing 0.24mm (0.009") from the left side of the front (tapering to zero on the right). It's a lot to scrape off so I am thinking about putting together some kind of clamp to hold the tailstock body in the surface grinder. On the other hand the bottom of the tailstock is small and accessible, so step scraping might not take so long. But the surface grinder clamp might pay off because after I get the tailstock parallel in the two planes, then I may need to remove more material to bring it into alignment with the workhead.

    Cheers,
    Bruce

    PS: I think I'll step scrape the bottom of the tailstock rather than grinding it. I think that will be faster than making a fixture to hold the tailstock. For those who don't know what it is, here is a nice short video by Jan Sverre Haugjord about step scraping.
    Last edited by ballen; 06-04-2018 at 01:32 AM.

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  16. #150
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    Jan was my first European student. He flew over to the 2013 Columbus GA class. He was the first one to talk about me on You Tube....he sometimes calls me the professor....lol

    Ballen it looks good....I am a bit concerned with the index pin alignment though. Why not talk about that in here to keep the instruction of the rebuild all in one place?

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  18. #151
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    Hi Richard,

    Thanks for sticking with me on this.

    Quote Originally Posted by Richard King View Post
    Jan was my first European student. He flew over to the 2013 Columbus GA class. He was the first one to talk about me on You Tube....he sometimes calls me the professor.
    You are creating quite a legacy!

    I am a bit concerned with the index pin alignment though. Why not talk about that in here to keep the instruction of the rebuild all in one place?
    I had the impression that no one else but you is reading this thread anymore (Probably it should have been in the "Machine Reconditioning, Scraping and Inspection" forum). Also, I was afraid that I have overloaded you with questions. (You did not reply to my questions about "checking the lift" in post #140 or about scraping oil pockets in #149. I know that you have classes to teach and a very full life and am afraid to impose so much!)

    Getting back to the index pin, I have the impression that the alignment hole is a bit deformed but will take a good look at it and in particular measure how far off it is. If the right thing to do is to scrape the workhead so that it's correctly aligned with that pin in place, I will do that. First will shim and measure as you suggest.

    Cheers,
    Bruce

  19. #152
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    Quote Originally Posted by ballen View Post
    I had the impression that no one else but (Richard King) is reading this thread anymore
    Nope, I've been following all this with interest. Very few projects have been presented anywhere near as thoroughly as you are showing us this Studer project.

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  21. #153
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    Quote Originally Posted by sfriedberg View Post
    Nope, I've been following all this with interest.
    OK, thanks for hanging in there. Perhaps I should have written, "no one but you is replying to this thread any more".


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