No announcement yet.

Dumb post about changing ball bearings.

  • Filter
  • Time
  • Show
Clear All
new posts

  • Dumb post about changing ball bearings.

    I feel kind of dumb. You know, "Oooooh..."

    I spend a loy of time chasing down ball bearings of special sizes for special applications. It seems a lot of time is wasted, because I always find ones that are just aaalmost right.

    Duuh. I just realized that BB's are not like completely permanent...if you don't like their dimensions, it is no problem at all to turn them down in the lathe or add a flange or a circlip. Or cut a recess for o-rings, or taper them a bit. Make them spherical or self-centering...
    Slow turning speed, fine feed, light cut with a carbide tip...piece o' cake.

    I hope someone remembers this and makes use of it when the need arises; it will save them some trouble.

  • #2
    I just hope that you're taking care to get any chips and debris out of the bearing assembly. Radial and tapered roller bearings are not expensive and are usually generally available at any bearing supply house. I definetly would not try this with any precision angular contact or precision tapered roller. It isn't worth the potential cost if screw up. Besides the reason that most bearing sizes are oddball is that they are METRIC
    Forty plus years and I still have ten toes, ten fingers and both eyes. I must be doing something right.


    • #3
      Hm. It's not that difficult to adjust a bearing diameter. Bearing races are machinable using ceramic tooling and of course you can grind and hone them. You do have to be fanatical about internal cleanliness but that's to be expected.

      My question is why? My career has stretched over 40 years in heavy industry and in that time I've only once had to machine a bearing race and that was for a second snap ring groove.

      Work your local bearing supplier. It's his job to come up with replacement bearings for you. Fetch him a sample: (Bet you can't match this one.) and he'll be all ofer it with his worn out dial caliper and stacks of catalogs. You may not like the price but you can ALWAYS find a suitable bearing if it was made on Earth.


      • #4
        >> You may not like the price ...

        The price would have to be pretty d*mn scary to make machining an outer race in a home shop the more attractive choice. You may be better equipped than I am, but I wouldn't care to try it in my home shop.


        • #5
          Whoa, what did I start? Somehow I made myself unclear... I'm perfectly familiar with the manufacturer's catalogs and commercial availability of unusual sizes. I'm also aware that unusual bearings come from unusual places and are not cheap. ("Well yes sir, we found your 3.14 bearing on Neptune, and it costs 9000 bucks...")

          The whole point was that I needn't locate the bearing or go to Neptune or spend the bux, when all I want is a flange on one end. An easy quick-fix, that's all.

          In this case it was a machine spindle that needed an axle of a specific size, and needed to be crammed into a housing of a specific size. Solution was to just trim the outer diameter a bit. Spent one day trying to work around the problem, another day locating a NASA bearing, and about twenty minutes just trimming a bearing I already had for free. How's that?


          • #6
            If you had to reduce the O.D. of the bearing to fit just how much was the reduction? If it was only in the range of .005" to .025" it makes me wonder if the bore was right in the first place. And no one's trying to start any arguments here.
            Forty plus years and I still have ten toes, ten fingers and both eyes. I must be doing something right.


            • #7
              One other thing, i seriously doubt that any of us really have the machinery capable of achieving the level of concentricity needed in a home shop.
              Forty plus years and I still have ten toes, ten fingers and both eyes. I must be doing something right.


              • #8
                I worked for an instrument company some time back.

                Every thread we cut was a bastard.
                It wasn't a 1.000-32, it was a .980-32 thread.

                It was done so you would get frustrated making a spare part, and buy their overpriced replacements.

                Wouldn't be surprised if some companys skim bearings off in the grinder for that reason.

                Whatever works for you.



                • #9
                  This may or may not be amusing. It depends on your out look. For several years I was responsible for repairing and rebuilding the machinery in our tool room and cutter grind departments. Well one days one of the T&D apprentices lunched the front bearing in a smaller K&T universal mill. No problem, diassemble the head, order new bearings & seals, fix any dimensional problems on the arbor,,,right. The front bearing would not move. Tried heat, no go. Finally cut the gage off to get at the race. The look on my bosses face when I showed him that the race for the front bearing was part of the arbor was really priceless. When I called the service department at K&T the first response I got was a chuckle and the service rep told me I'd just joined the club. Seems the only way they could get the proper bearing and the tool holder in the arbor was to go that route. We had to send it in to K&T to get ground and then Timken Would grind a special set of rollers to match the corresponding change in taper angle. And thats the primary reason I think modifying bearing sizes is a dumb idea for the most part. Yes it can be done when required but there are usually other solutions to the problem.
                  Forty plus years and I still have ten toes, ten fingers and both eyes. I must be doing something right.


                  • #10
                    Well sure Spin, of course it's a dumb idea. I would never, ever dream of putting something like this into a production scenario. Of course not- think of all the frustration and added costs it would induce. And when designing a new component, of course I start with the known parameters of available components. Established standards are paramount.

                    The point was, that in a tight spot with few viable alternatives, this one presented itself very nicely. It's a machine modification, and I am the one & only owner / user of the machine. No harm there. With regards to accuracy and concentricity, I don't have any better equipment than anyone else, and can achieve only what may be deemed normal for the circumstances. Really it isn't that important, since the bearing (outer, newly machined race) lives in a casting on a fully adjustable slide. It still spins perfectly, and would even if I had so made it into some wierd polygon shape.

                    So from one Doc to another, man...Sorry if this idea somehow got your stethoscope all knotted up, but it was only intended as a simple D.I.Y.-when-you're-in-a-jam-fix-it trick.

                    And, if the unforeseen should happen, the bearing is labeled with its original number and diametral reduction. So, no future confusion.


                    • #11
                      IMHO bearings have over the years become very standarized. I have hit some odd ball ones. those fall into two classes- those that as alluded to before are differnt just to make money on spare parts (or more likely- to use up some expensivebearings that were available cheap and the Mfr saved bunch back for selling at high cost) and those that differ becausethe needs are different- like those big thin rollers in jet turbines. In case one I have, usualy with success, modified the parent machine to use a better bearing that is standard, more expensive to modify the machine at first but cheaper in the long run for high use machines. In the second case, they differfor a reason so stick with the OEM.

                      BUT! being able to modifiy a bearing is a skill that could be useful. Further more its the type skill you want to learn at leisure, not under pressure. A neat trick.

                      Once in South Texas, The rear universal dropped free and lost the bearings (two of the four on the cross). Road was very little traveled- did not see another car during the entire incedent. first i wrapped some nylon cord where the cup and rollers used to be. Lasted maybe a mile, and while driving I am thinking all the time. Wife two kids, little water, sun getting past noon. Next stop, selected at my choice, I had the girls bring me back some aluminum cans (probaly beer), with pocket knife, cut a spiral length of can. wrapped it around the cross arm, well oiled and rove about 25 miles to Pecos Texas, bought a new joint, wnet to garage and was told tommorrow may be the day after. Drove the car across a ditch, fifteen minutes and had new cups (only the two held by a strap were missing) installed and on my way. Its rough learning how to make bearings under pressure!!! THanks Dr.Rob


                      • #12
                        Ditto Docksteve - I had a drive shaft throw itsself out on a 100*F day near Vernon, Texas. Took oak splinters from a small dead tree in pasture and packed the U-bolts where the cups were lost. Drove 20 miles back to town, bought parts, went to city park under a tree and fixed it! More than one way to skin a cat.


                        • #13
                          More than one way to skin a cat? Yep

                          In the 1930's picking cotton and following wheat from Corpus Cristi to Sascat... the province in canada with the long name.... cotton was paying .50 cents per hundred wt, good man could get 200 lbs a day. Whole familes (men, women, kids (rollers ,walkers, runners) were barely able to get from one town to another (job to job). I saw tires packed with sand, sawdust, a good way to get along was to take a good slick carcass (one the would not pinch the innertube but had no tread), cut the bead off a good treaded tire, wrap the treaded tire around the slick one, put carriage bolts around the rig to keep them together and head for the high cotton!!! (or fields of grain). Rear ends filledwith oily sawdust causethe seals leaked too much oil. Heard of, never saw, Bacon rinds used for crank shaft bearing material until next job.

                          Dad Over hauled our 1928 Dodge truck in Scotts Bluff nebraska, behind a Sherwinn Williams sign board,near the the Dodge Dealer. Man from the dealer brought his "crankshaft grinder" that they used to redo farm equipemnt, and bround the crank shaft for us. It was a belt that threaded through the cylinder, around the throw of the crank (I have no idea how the belt was rejoined) and a litle engine to spin the crank shaft. The motor that drove the belt moved up and down on springs to keep the belt tight. Miked the crank throws, and he had another little machine the only sized the bearings (the truck had inserts vice shims like chevvy). Each bearing a differnt size. I think the machine was made of a fly type cutter, a fine threaded bolt, fitting in babbit bearings. total travel would not have been 2 inches. whole rig was a motor and chunk of wood about 6 by 6. The dealer was gone, the sign (in poor shape , but still readable- wonder if it was painted with the advertised paint) was still there in the mid eighties.

                          And baling wire was really useful to hold parts together till the days work ended.

                          Hard to believe how ingenious some of those old fellows with a "3rd reader schooling" could be. They taught me lessons that I have not used in years, hopefullly never again.

                          But a man can usualy stick it out with what he has on his person, if he "don't panic", and uses his "God given brains"

                          Nuff nostalgia. Merry Christmas again



                          • #14
                            Used to spend days off in old time auto parts store. fellow came in and ordered a set of engine bearings. Told us he spun a bearing somewhere around Kansas. We are in Lancaster, Ohio. He had the idea of using peices of leather belt to replace the bearing. Went to store bought all the belts they had. Dropped the pan every 50 miles to replace belt. After about a day of this he "discovered" that if he would punch a hole in the leather that oil could then get through and get 100 miles out of the setup. Stubborn ain't the word
                            mark costello-Low speed steel


                            • #15
                              Docsteve -

                              Thanks very much for those nostalgia trips!!!

                              Very Merry Christmas