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  • Bearing conversion for steady rest

    This started on the 'What did do today' thread but I've split it off to avoid hijacking it completely.

    Just a quick recap:
    Originally posted by me
    Drilled and tapped some M3 holes in the brass fingers of my steady rest ready for some bearings. Inspiration from here: http://www.toolsandmods.com/lathe/lathe-steady-rest
    Originally posted by CCWKen
    Saw something like that years ago and this refreshed my memory. At the time I didn't have a mill but I think I'll do similar now except use a key-cutter and make a pocket for the bearing at the center of the fingers. Thanks for the refresher! And keep up the early involvement with your helper! The chance goes away quickly.
    Originally posted by J Tiers
    Suggestion #1 .... use steel if you are going to have a roller.
    This is the steady rest with the original brass finger and a bearing screwed onto the end. The bearing is 10mm OD, 5mm ID and 4mm thick. In hindsight I should have got 4mm ID as then the head of a screw would have made good contact with the inner sleeve without a washer.
    If I did go with J Tiers' very sensible suggestion of making a new finger out of steel, I'd have to have some sort of bushing for the shoulder of the screw (left hand side of pic) to rotate in as there's significant transfer of brass onto it even with the little I've used it.




    This is the bushing/axle I made as the dimensions of the brass finger limit the size of a threaded hole to M3




    and this is the result of me cutting a pocket and getting the mounting wrong. I'm hoping that a visualisation of the dimension (assuming a similar size steady rest) may be of help to CCWKen if he's planning to do the same.



    The problem was that it was threaded all the way through - both sides of the finger and the axle. Thought I could get away with it but it (and did a couple of times) but it jacked apart on final reassembly and the brass broke.
    Now, the logical thing to do would be to just screw three bearings onto the sides of the fingers as the original recipe called for. I do like the idea of them being inset though - it just seems 'nicer'. The question is, how should this be done correctly? ...and this really is a search for a better understanding of how bearings and shafts and the like ought to be done rather than just this specific problem.

    I've made the axle 5mm in diameter so that it is a gentle press-fit onto the bearing. I figure I want the bearing to do the work so I don't want it spinning about its axle and it definitely doesn't want to be a sloppy fit. What's the recommended procedure here? Slip-fit and Loctite or press fit?
    The axle I made is Loctite'd in but I suspect some may have got in past the rubber shield as the bearing is a little lumpier than it was.

    The hole through the middle I made threaded. I understand this was part of the problem but if I made it a close-tolerance clearance fit would I not then have problems with the axle spinning about the screw and gouging up the bore on the thread?
    In the simpler 'screwed on the side' method, the screw clamps the axle against the finger so that prevents it turning. With the axle being mounted inside the finger, do you rely on the screw pulling in the sides enough to clamp the axle stationary?

    I realise that there needs to be something making contact with the inner sleeve of the bearing and not the outer race so that the bearing doesn't grind against the metal to the side of it. I made my axle 5mm with a flange 6.5 mm diameter by 0.5mm thick to do this. I think for quicker repeatability (making three of them) it would be easier to just make a 5mm axle and use a washer each side - although I think the thinnest I have is 0.8mm which is beginning to make the sides of the fingers a little thin for comfort. What's the usual method here?

    Many thanks in advance,
    Gareth

  • #2
    I am in the early stages of a similar project. I bought a Chinese fixed steady on eBay for the museum's Smart & Brown model A, removed the base and fitted it to an aluminium custom made one. The drawback was the maximum diameter of 2" with the bronze fingers. Fitting rollers was possible, but at the expense of diameter.
    So when a larger fixed steady (also Chinese) turned up on eBay at a good price, I grabbed it. The usable bore is about 4" with a hinged top and the fingers are 18mm diameter. Making three additional fingers out of 18mm ground silver steel with slots for bearings will be easy. I have bought three ball races, rubber sealed of 6mm bore, 15mm od and 5mm wide. Since the bearings will be in slots in steel with a through axel, I won't have the weakness of Gareth's first design. The steady should be usable from 1/2" to 2 3/4" diameter.

    I am going for the washer either side of the inner race to give clearance for the outer race.
    Last edited by old mart; 04-10-2018, 10:02 AM.

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    • #3
      Planning ahead comes in handy once in a while. Your brass fingers look a little thin or bearings too wide. I wouldn't have cut that much stock out of brass. The slots in the follower they ride in looks capable of handling a much beefier finger. Take advantage of that and make thicker fingers. I think they did that so the follower could go up close to a chuck, face plate or flange with the mounting hardware they had but how often does that occur? (Not sure where your follower mounts in relation to the tool tip.) And there's no rule that says you can't countersink new hardware into the fingers.

      I know you're trying to use parts you have and I've opened a can of worms but stepping back and looking at the big picture can save a lot of frustration.

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      • #4
        That's good to know. Would be interested to see photos if/when you've got to that stage.
        How do you intend to stop the bearing spinning on the axle or do you not see it as a problem?
        How do you intend to fasten the axle to the finger to stop that spinning?

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        • #5
          Just make sure you keep any chips from coming in contact with the bearings or your going to have problems. Since a follower is mounted on the carriage close to the cutting tool it's going to be a challenge. That's why followers use a finger type contact so chips can't get rolled under it.

          JL.................

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          • #6
            Hi Ken. Not a problem opening a can of worms. I have the obvious easy way out if I should chose to take it....but sometimes complicating things can be interesting! And I'm fairly sure I'm going to come across this issue with bearings on shafts at some point in the future so it'd be helpful to understand how not to do it in advance! The double-ended bump tool I have in mind, for example.
            I originally bought as wide a bearing as I could find, thinking it would spread the load out on the part. I could probably make the fingers wider if I made new ones. The securing bolt (black, oval-headed) would stick out proud of the surface but that's not as much of an issue as I originally thought it was - I thought the head needed to engage with the slot to prevent it turning but it's just to clamp the finger in place once adjusted.



            Would probably still have to make them out of brass/bronze to re-use the existing adjustment screws though - unless there's another way I can make a bearing surface for the screw...?

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            • #7
              I think you are worrying too much about the bearing surface of the screw wearing, its probably the screw itself having such a rough finish that it is abrading the brass. Smooth up the surfaces with some fine wet and dry paper or a fine stone/lap.

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              • #8
                You may well be right. Lack of experience makes me look for problems that may not be there....but I'm getting there. Whether I'll have driven you all to insanity before I get to that point is still up for debate!

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                • #9
                  As mentioned by JoeLee earlier, it is important to prevent any chips/swarf from getting in the vicinity of the rollers. A thin piece of plastic the diameter of the steady rest with a hole to just clear the workpiece would do quite well. Save each one used for future jobs and some sticky tape would hold them on the steady.
                  If you make some new fingers, whatever metal they are, make the nose end thicker to give yourself more meat to work with.
                  Last edited by old mart; 04-10-2018, 12:00 PM.

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                  • #10
                    Will have a go at that. Ordered some 20 x 12mm steel. Should give me another 3mm of thickness to play with and a stronger material. Definitely plan to make the nose a bit longer so I've got more material between the mounting hole and the slot. By my calculations, I should still be able to get 40mm diameter through it or thereabouts. Haven't yet gone over 20mm so doesn't (yet) sound like a limiting factor.
                    Presumably keeping the chips out isn't to protect the bearings - I got the two rubber shielded versions to (hopefully) prevent that. It shouldn't be able to deflect the material that much as the other two contact points should stop it so presumably you get a chip under the roller and it just makes a mess of the surface of your piece? Being that the outer race of the bearing is going to be hardened and therefore 'win'.

                    Comment


                    • #11
                      I believe the concern with chips is getting them between the roller and work.

                      I'm assuming that is a traveling steady rest? imo, you are better off with with bronze solid fingers than a bearing for a traveling steady. I did the opposite - the steady came with bearings and I made bronze fingers. Aside from small chips getting caught, my main reason is that it takes a slight bit of force to get the bearing turning - a fair bit of force if its sealed type. This can play havoc with trying to get anywhere close to a thou or two over the work when its long and spindly. A fixed steady is different - you can put put some pressure on.....do that with a traveling steady and you'll get a different diameter in the middle vs chuck and tailstock

                      Using one to a degree of accuracy depends on a bit of a feel - after starting the cut at the tailstock, and with everything working, bring the fingers into contact with just cut surface and pay attention to how much force you pun 'landing' them. Measure the centre. If its a larger OD than the tail stock end (and the lathe is aligned properly, often it'll need a tweak on a long cut), 'land' them with a bit more force next cut.
                      Last edited by Mcgyver; 04-10-2018, 01:29 PM.
                      in Toronto Ontario - where are you?

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                      • #12
                        Actually it's a fixed steady, I've just cropped out the differentiating features. Useful info for when I have cause to use the travelling though. Currently I'm getting different diameters all over the place....but that's another thread!
                        The little 10mm bearings (apart from the one I think I 'infected' with Loctite) spin really freely so I'm hoping I should just be able to advance the until they start spinning and work out if they need a little more from there.

                        I'm planning to try the quick release clamp too - mine can only be inserted from underneath and only in certain places - but that's a project for when I finish levelling the lathe and rule out bed twist.

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                        • #13
                          Originally posted by Mcgyver View Post
                          I believe the concern with chips is getting them between the roller and work.

                          I'm assuming that is a traveling steady rest? imo, you are better off with with bronze solid fingers than a bearing for a traveling steady. I did the opposite - the steady came with bearings and I made bronze fingers. Aside from small chips getting caught, my main reason is that it takes a slight bit of force to get the bearing turning - a fair bit of force if its sealed type. This can play havoc with trying to anywhere close a thou or two over the work. A fixed steady is different - you can put put some pressure on.....do that with a traveling steady and you'll get a different diameter in the middle vs chuck and tailstock

                          .....
                          With turret lathes, it is pretty common to use rollers on the box tool , which is about what the traveling steady and tool form... Somehow they get it to work, but they a;lso tend to have far less "stickout" than the traveling steady is generally employed with. And often are used as a roughing process, prior to grinding, so tolerances of 2 or 3 thou is no issue.

                          If you use "shielded" bearings, and wash out the grease, using oil instead, there should be a lot less trouble with pressure and friction. Check out what Brian Rupnow has done with bearings on some of his more recent engines. I totally agree that "sealed" bearings would be a problem in most cases, and clearly open bearings are not applicable. The "shields" normally have a tiny clearance, and contribute no drag.

                          I'd be more concerned with what the effect of chips might be... if they get "ironed-on" to the part, that may shift the part position as they come around under the rollers, and mess up tolerances a lot more than the bearing pressure. I have not worried about roller steadies for that reason. Maybe I am just being too conservative, maybe not.
                          Last edited by J Tiers; 04-10-2018, 01:39 PM.
                          CNC machines only go through the motions

                          Comment


                          • #14
                            Originally posted by J Tiers View Post
                            With turret lathes, it is pretty common to use rollers on the box tool , which is about what the traveling steady and tool form... Somehow they get it to work, but they a;lso tend to have far less "stickout" than the traveling steady is generally employed with. And often are used as a roughing process, prior to grinding, so tolerances of 2 or 3 thou is no issue.

                            .
                            A box tool is not comparable to working with long spindly stock, the challenges to a consistent diameter are exactly as I described. Can you give examples of your using bearing traveling steady on a long spindly turning (the kind you need a traveling steady for) that came out to within a thou or better without issue? My comments as described are based on experience, as was the solution that worked - bronze fingers. Perhaps you have a better way.
                            Last edited by Mcgyver; 04-10-2018, 01:57 PM.
                            in Toronto Ontario - where are you?

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                            • #15
                              I am basically agreeing with you.

                              As mentioned I have avoided that issue by not installing rollers on either the steady or travelling rest, both of which I use.

                              I suspect that using light oil etc would help, but cannot prove it is perfect. That's why I suggested it, since I do have ball bearings that are very free, and appear likely to work for the purpose. That does not affect the issue of jamming by chips riding on the work or roller OD.

                              Turning is likely not ideal for long thin parts that need to be very tightly toleranced. I do it because I do not have a cylindrical grinder, nor a centerless grinder, and even with the "sliding" jaws, a thou is doing very well, IMO, depending on diameters, length, etc. 2 or 3 thou is probably more common for me.

                              I have used a TPG for the purpose also, and found it is not a lot better, actually, as far as actual diameter. It still needs backup, even with relatively light pressure. Surface finish is obviously a good deal better, though.
                              CNC machines only go through the motions

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