Studer RHU 450 from the 1960s - Page 9
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  1. #161
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    I had some time today and since I have not heard back from Richard about this, I went ahead on my own. Originally I had planned to remove material from the lower half of location 4 (just beneath the grinder wheel casting). But after I got the parts off and looked at them, they were too long and too wide for my grinder and for my surface plate. After that I decided to remove material from the upper part of location 2 (rotary table just above machine casting). Here are the bottom and top:





    To get a reference surface I first ground the non-working surface above the dovetail, using the rotary plate as a reference. This surface was originally planed and still had the planar marks. By grinding it parallel to the rotary plate, I get a reference surface which I can then use for milling and grinding the rotary plate to a different height.



    Then I milled off about 480 microns (about 0.019"). I did this using multiple passes of a small carbide end mill because that made it easier to compensate for some "belly" in my milling machine.



    Then back to the grinder. The part is twice as wide as my grinder, so I needed to do half, then rotate and blend. Note that in both the milling photo above and the grinding photo below, I am using the reference surface created earlier to clamp the part down.



    The result is not perfect but better than the other alignments in this part of the machine. I had thought about deepening the relieved center portion when I had it on the mill, but I did not want to "erase" the machine number stamped onto the casting, and since the facing part is relieved, I decided not to relieve this part further.



    The hold-down dogs no longer had enough range, but they had 14mm holes and a 12mm eccentric drive, so I bushed them in to 13mm. I made the bushings by lightly knurling some 14mm steel rod then boring it out to 13mm. I coated the bushings with permanent loctite and squeezed them in with a vise. Not pretty but works well!







    Here it is, 0.52mm = 0.020" lower than this morning.

    Last edited by ballen; 07-09-2018 at 03:03 AM.

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  3. #162
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    Edit: This messabe was written while Bruce's preceding message has been posted.

    Hi Bruce,
    Quote Originally Posted by ballen View Post
    I set a dial indicator stand on a pair of 18.00mm high parallels and zeroed the indicator on the wheel hub.
    Has the real height of the parallels been checked, too?

    After some parts of the machine have been rebuilt (e. g. the table), before removing so much material from the grinding wheel stock, I would measure the geometry of the grinding wheel stock guide surfaces related to the rebuild parts before. I expect, that the relevant surfaces of the grinding wheel stock are within the wanted geometry, but who knows, if there could be found another issue, remaining from further pre-owner's rebuilds.

    Quote Originally Posted by ballen View Post
    Comments please. Where is the best place to remove 520 microns = 0.021" of height?
    I'm not sure, don't have enough experience; so I'm tending to remove the 520 microns from the top surface that matches to surface 4. In the photograp, that top surface seems to be made for removing some material, because the level is interrupted by a painted lower surface.

    Cheers,
    Karl

  4. #163
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    Quote Originally Posted by CharlyDE View Post
    Has the real height of the parallels been checked, too?
    Yes, it's within a few microns of 18mm.

    After some parts of the machine have been rebuilt (e. g. the table), before removing so much material from the grinding wheel stock, I would measure the geometry of the grinding wheel stock guide surfaces related to the rebuild parts before. I expect, that the relevant surfaces of the grinding wheel stock are within the wanted geometry, but who knows, if there could be found another issue, remaining from further pre-owner's rebuilds.
    I did study the remaining misalignments before cutting and grinding.

    I *only* removed 520 microns, because if I correct the other inaccuracies, one of them will raise the axis 40 or 50 microns, leaving enough material for me to remove to correct other inaccuracies below. It's complicated to explain, but I will put the machine within the Studer and Schlesinger specs now, and can keep it there if I also correct the additional inaccuracies that I found in the grinding wheel slides. Those inaccuracies are:

    (a) grinding wheel spindle points down and to the left, because the cross slide on the machine base has worn about 40 microns = 0.0015" more on the left side where it runs on a V-way than on the right side where it runs on a flat way. I could step scrape the lower half of the rotary table to compensate for this. If I do that it will raise the grinding wheel spindle on the left (the main one) and lower it on the right (where it was even higher).

    (b)On the upper (manual) cross slide under the grinding wheel the two dovetail faces are out of parallel by about 20 microns (0.0008") over their length. At some point in the future I might correct this, but I don't think it's enough to have any effect on the accuracy of the machine.

    I'm not sure, don't have enough experience; so I'm tending to remove the 520 microns from the top surface that matches to surface 4.
    This top surface at location 4 is the grinding spindle casting. It's heavy and hard to clamp and align, so I did not consider this the best option.

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  6. #164
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    I like what I see....sorry about not responding as I am at the cabin. I recall reading your message, but I guess I forgot. sucks getting old. You didn't need my help and I am so proud of what you did. Grinding the top was exactly the way I would have done. Rich

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  8. #165
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    Rich, Karl, thanks for your feedback and comments. I spent a bunch of time measuring the geometry of the rotary table and slide, so if I want to make these better, I now have a good idea of where metal needs to be removed. But as far as I can see, it's all within spec and "good enough" as it is currently.

    Before reassembly, I "fixed" a slow spindle-oil link in the grinding wheel head. I put this in quotes because the leak was so slow that I am unsure about where it was from. So I won't know if this worked until after the machine is back together for a few days or weeks.

    I am going to make one other improvement before reassembly. I noticed that the cross slide is very worn in one corner, which is closest to the grinding wheel and coolant. In the photo this is the bottom left corner.



    Another reason it is so worn is because the way oil for this corner comes from an oiling nipple which is completely hidden behind the grinding wheel guard! Even if you know it is there, and want to oil it, that's not possible without removing the wheel guard and the wheel and flange. Definitely a design oversight.

    One way to "fix" this is for me to mill a diagonal oil groove that connects this "bottom left" oil ring to the one on the bottom right. But I don't like that much.

    So I am going to try drilling a new oil passage as shown with the red lines, to connect this bottom left (in the photo) oil ring to a new (visible and accessible) oil nipple that I will add. I will need to drill three long holes in cast iron, 6mm (1/4") diameter, one with length around 120mm (5") and the other two with length around 105mm. These holes only need to be precise enough to intersect each other and existing passages (say under 1mm wander in 100mm). I will plug two openings with aluminum or brass plugs.

    I'd welcome comments on this idea.

    [EDIT]

    I decided that this was the way to go. Drilled the passage that goes across the cross-slide, went in 110mm = 4 1/4" from each side. The holes met perfectly in the middle . This 1960s Swiss cast iron cuts beautifully. I did these in vertical mode because access and clamping were easier. The third hole I'll do in horizontal mode because the cross-slide is too long (480mm=19") to stand vertically. Or perhaps I'll remove the work table and clamp it directly to the vertical table. Hmmmm...



    [FURTHER EDIT]

    This part is finished: I did the last oil passage this morning in horizontal mode. Instead of plugging the ends of two of the passages, I enlarged them to 6.8mm and threaded them M8. I will close them off using M8 setscrews secured with thread sealant.



    The passage I am drilling here meets up with the oil hole visible in the photo above, which that feeds the oil ring at the top right.
    Last edited by ballen; 07-12-2018 at 07:48 AM.

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  10. #166
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    Here is a photo of the cross slide with the new (second) oil nipple, where I've indicated the new oil passage with red lines.



    Originally I had intended to put this new oil nipple the left end of the cross slide (where the hex-head grub screw is visible, covering the 210mm hole that I drilled to carry the oil to the far side of the cross slide). But I realised that this corner will be covered by a splash shield. So I drilled one more passage about 50mm = 2" long to locate the oil nipple next to the one for the near side of the cross slide.

    I had to close off four openings: two on the front of the cross slide and one on each side. The traditional way is with brass or aluminium plugs. I prefer a more easily reversible solution. So I threaded each opening for an M8 grub screw (8 x 8 mm) which is secured with a liquid thread-sealant.

    I was wondering about one other point. The angled sides of the dovetail do not have any oil points, and are above the flats, so don't get oil from there. It would not be hard to make a diagonal oil groove in the gib with a hole to carry oil from the other side, and add an additional oil nipple for that. It's harder to do cut an oil groove on the other side of the support, but also possible. On the other hand, most of the weight/load is on the flats, so perhaps it's deliberate that there is no oil groove on the angled sides. Is there any logic to this choice? My idea is to cut a long diagonal oil groove which starts at the top back and angles down to the bottom front, with an oil nipple feeding oil into the top back. Then gravity would carry it down the groove.

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  12. #167
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    Looks good Bruce. You have it under control :-) I do have some suggestions. Do some measuring and see how far the wheel head slides forward and to the rear. That is probably why they put the circles where they did. Many times I will cut a diagonal oil groove between the 2 circles and in many cases I cut a groove at the end of travel about 1" from the extreme ends of travel at right angle to the travel so the oil spreads evenly as it moves forward and backward. One thing you HAVE to be sure of is you do not cut the grooves out to far long or sideways so the circuit is open to the air as you know all the oil would drain there.

    I would also think about running steel or brass or copper oil lines to the rear of the machine with a oil Zerk fitting as I dislike those ball oilers. Your choice though :-) A auto lube pump would even be better :-)

    Have you checked to see if the slide ways are flat? They wear high in the middle...why? You should know...lol Think about it before I tell you. lol Where does the dirt wear slides first? On the ends. I would think they (factory) scraped the shorter way lower so as it wore it didn't get high in the middle and rock like grandma's rocking chair. I like the way you are improving your machine. Everyone makes mistakes, even Studer. I have had to re-engineer many machines over the years after I have discovered a flaw in machine manufacturing. You have discovered how one eliminates stick slip by scraping oil pockets in worn ways, but not worn enough to affect the accuracy. Ballen your a good example of a good example :-) Thanks for your thread. Makes me smile and proud. Rich

    Ooops I forgot the gib. Many times builders leave the gibs flat, I suppose they figure the .0005" per side will let the oil drain through the gap. I will grind a bevel on the top side of the gib to help the oil to drain down. Also I cut a diagonal oil grove (most of the time I use a die grinder and a Christmas tree shaped carbide burr. Again being very careful not to grind to low so the oil just drains out. If you wanted to get a bit more detailed. Have you seen how a Bridgeport lubes it's gibs?

    They feed (oil) the wear side from the back positive side of the gib and it has a groove in it laterally so if you adjust the gib deeper it still gets oil. Many machines also have pressure lube that feeds from a Zerk drilled into the big end in back if there is room. Now you have put your thinking cap on. Rich

    PS: check gib to be sure it isn't bent and check in machine with blue when it is in so the center 40% is .001" lower so it wears on the ends. Be sure to check the surface where the positive side rests. They seem to always get high in the middle


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