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Pressing bearings

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  • Pressing bearings

    First, thanks for the help in my previous post - I've decided to go ahead with the ones I've got... but I have a few questions before I get started as I've never pressed bearings before.

    Here's a pic of the arbor, as it stands right now:

    You can see one of the old bearings on the shaft, and the flange against which the blade sits.

    First, I need to get this old bearing off. Should I press both pieces off over the threads, or all the way to the other end of the shaft? I need to reuse the flange, but I don't care about the bearing, of course.

    Second, is there anything special I need to know about pressing the new bearings on? I know I need to support things properly, and press only on the inner race of the bearing. Again, for the flange and bearing near the threads, should I press over the threads or should I press on over the un-threaded portion? I was considering heating the bearing a bit and maybe cooling the shaft - worth the trouble? I've got an old toaster oven to do the heating, I was thinking about 180-200F or so.

    Thanks guys!

  • #2
    After you get the old bearings off, polish the shaft real good and while you're doing that, heat up the bearings in some 10W-40 motor oil. Don't let it smoke too much. Let them soak in the heated oil bath for about 30 minutes and you should be able to just slide them on the shaft without needing the arbor press


    • #3

      That's an interesting method of heating bearings. Presumably this would only work with sealed bearings?

      You didn't say how hot the oil needs to be. But you mention not to let it smoke which implies fairly hot.

      Is there a chance of the oil bath dissolving the grease in the bearings? Or of oil getting into the grease, possibly causing the bearing to be overlubed?

      The only way I've pre-heatd a bearing was by resting it on top of a light bulb.


      • #4
        My guess is you'll want to press the bearing off away from the flange. the units I have dealt with the flange is silver soldered on.


        • #5
          About the hot oil - I looked on the NTN bearing website, and it mentioned this method with no disclaimers about sealed only/overlubrication, etc. That said, I still think I'd prefer using an oven to make sure... Any reason _not_ to use an oven to heat it?

          About the silver solder - I hadn't thought about that. I just looked, and I can't see any evidence that it is soldered. There is a slight chamfer on the hole in the flange where the shaft goes through, leaving a slight "groove". If it was soldered, I'd expect to see some solder in this groove, which I can't. I even broke out the 10x loupe.... This is a 1979 craftsman - not a high-end saw. Think it may just be a press-fit? Any harm in trying (gently!)? I'm thinking it'd be a real pain to pull the bearing without disturbing the flange, since there's no gap between the two to get something in. I guess if I have to, I'll heat it up and try pulling on the outer race of the bearing.


          • #6
            I would press the bearing off. I would use the outer race to press it off. You aren`t planning on re-using it are you? I would stay away from heating up sealed bearings. I find there isn`t enough grease in them to begin with so why melt some of it away. The oil idea is cool. I never thought of that. I am not a fan of the idea because there would probably be oil dripping out of the bearing for a good little while and if the oil isn`t new then you are just putting in dirt/sand/metal shavings into a new bearing.

            You can buy this cooling product from GBS that is a spray. This will cool the shaft. It takes alot fo spraying in my experience. Another way to heat up the bearing is by putting it on a curling iron. It doesn`t take too much heat to make a difference. I love the using a lamp/light idea.

            Well after all that rambling here is my suggestion. Just press the bearing on. Make sure the shaft is smooth and press away. These things are made to tolerences so use that to your advantage. Stay away, as much as possible from the flange. You don`t want to crak it of make it skewed. Your blade will never be square with the shaft and you will wounder why all your blades seem dull.



            • #7
              I use an old fondue pot. I dial up 300 degrees and park the bearings in the dry pot, no oil. Small bearings cool VERY quickly. Rehearse the assembly when the parts are cold. Heat the bearing. Move with alacrity.


              • #8
                I use a heating elment from an electstove and set the bearing on the element and watch is closely. when the oil on the bearing starts to smoke the bearing is ready to go on the shaft.

                Also I get a gallon or two of kerocene put the kerocene in an open bucket. Then put a couple of pounds of dry ice in the kerocene. Don't put too much in the kerocene at one time, wait untill the temp equalizes some than add more dry ice. Lay the shaft in the kerocene for a few minutes (15 minutes or so depending on the size of the shaft). It will go togeather so quick you will be amaized.

                Why kerocene? It transmittes the cold better than just laying the shaft in dry ice.

                You save the kerocene and use it next time.
                Don\'t ask me to do a dam thing, I\'m retired.


                • #9
                  What a bunch of great ideas for heating bearings...this is the reason I am on this website daily....

                  I like the light bulb one....I have used a tapered rod so the bearing would fit over it and then slides down till it stops..and then I heat the rod,(with a torch) which of course transmits the heat to the bearing..but I like all the other ideas better than mine...



                  • #10

                    Do you have tolerances to the shaft and bearing that you are installing? Just for kicks.



                    • #11
                      You're probably done the job by now, but just another few ideas- heat the flange with a propane torch instead of in an oven or other means. What will happen if the heating is too slow, the whole thing heats, and nothing changes, except your fingers burn when you pick it up. You don't overheat the flange, but expand it quickly, so it has a chance of becoming looser, before the shaft heats too much.
                      If you didn't see silver solder with the magnifying glass, it isn't there.
                      The inner race of the bearing isn't much metal, and it will quickly cool to the temp of the shaft, press it to position quickly.
                      I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-


                      • #12
                        I tried taking that flange off on an old arbor a couple years ago and it would not move at all. Not sure how it's held on, but it is very tight. You also have to get the flange back to the same spot when you reassemble it, otherwise the arbor is not going to fit back in the saw trunion, the flange positions the flange end bearing and the grooves on the other end position the floating bearing. If you are off, it may not fit right.
                        Bearings of that size are easy to press on, use a woodworking clamp and a piece of pipe that fits over the shaft if you don't have a press.


                        • #13
                          Try placing the bearing on top of a light bulb in a lamp, say 100 watt. This heats the bearing in short order without too much heat.


                          • #14
                            Since this is a Craftsman saw, I will guess that the flange is pressed on a knurled section of the shaft. I took down an old Craftsman a couple of years ago, have no idea as to its age, and it was pressed on. Since I had no way of knurling the new shaft I had made, I pinned the flange to the new shaft. If memory serves me correctly, at that time(1979), Craftsman saws were made by Emerson Electric Co., at Paris, Tennessee.


                            • #15
                              To remove the bearing use a bearing splitter. It fit around the shaft and has two threaded rod that you tighten. There is a tappered section that will push it way between the bearing inner race and the boss that the bearing is against. Once it is in place, on the outer race, use the press and press the bearing off the rest of the way. Don't remove the flange it is probably a shrink fit and would be hard to get back in the same position. The clearance between the bearing and the shaft should not be so tight that with just a little heat it would slip on. You should be able to press it on cold but a little heat won't hurt. The light buld idea would work fine. When you press the new bearing on only push on the inner race. You will damage the bearing if you press on the outer race. use a little lubrication when you install the new bearing.

                              Hope this helps.