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Need vindication, thoughts on bushing change

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  • Need vindication, thoughts on bushing change

    I have a 11" Logan/Powermatic made in 1981. I finally decided to remove the carriage and perform the saddle/way lubeing upgrade JTiers did to his Logan. So those I got done. Since I had it off the bed I decided to check out the apron internally. Everything was in great shape and no issues.

    The issue I found, and hope you can follow the description :-) On the backside of the apron is a wormgear that the leadescrew goes through. The wormgear is keyed to the leadescrew to provide power for long and crossfeed. I decided to take it out for inspection also. The wormgear has extentions on either end which ride in hollow steel caps as bushings. These caps are carried in trunions intregally cast on the backside of the apron, and captured by setscrews. The caps are like those on a 'U' joint except open so the leadescrew can pass through.

    While the wormgear itself is in primo shape, the bearing surfaces at either end were scored. One not badly and the other looked almost like it had tiny fine threads turned on it. Ditto the caps being worn the same. The ends of the wormgear bearing surfaces (thrust faces) were also worn (ribbed) from contact with the caps. Pressure I suppose from turning the gear for long and crossfeeds.

    I can get a new wormgear and 2 new bearing (bushing) caps from Logan for about $300 total. Actually I don't consider that too bad for what they are, etc, etc. I'd just rather not spend that much if I don't have to. I don't know why they used steel on steel, nor do I see a really positive way that the bushings are oiled. It's a wet apron and the wormgear turns a gear that dips into oil, but how it gets to the bushings is a mystery to me. When I took them apart they had oil. They don't turn really fast but ........?

    My idea, and for this I need you thoughts and input, good idea/bad idea, etc. I have a friend who said I can use his lathe to do the work. I figure I can clean up the wormgear bearing surfaces with a .015" cut & polish, if that much. The cap's, or captured bushings have about .200" thick walls. I figure I can bore the walls thinner .075 to 0.100" and then turn a bushing to press in. The wormgear then running on these.

    Since there is considerable thrust on the worm gear when power feeding, I had thought to put hardened steel rings inside the bearing caps. These would have to go in before the bronze bushings are pressed in. You can see where the ends of the wormgear have worn themselves and the inside flange of the bearing caps. It's obvious neither is hardened. I don't think having bronze thrust washers, or forming them in the new bronze bushings would be optimal due to the rather narrow surface on the ends of the wormgear bearing spigots.

    One of my reasons for asking is that the rest of the machine is fairly well outfitted with impregnated or oiled bronze bushings. Why not here? Why steel on steel?

    For positive oiling my idea is to drill through the bearing cap trunions, the bearing caps and the bushing. Then thread the trunions and use elbow zerks. I'd unscrew the nose with the spring and ball off the zerk, and thread some steel brake line to screw in. I could run these around the right end of the apron and use spring top Gitts oilers and afix them to a bracket. Then before or during use I could give each a shot of oil on occasion.

    Maybe grease would be better? With elbow zerks a flex nose gun can easily reach them behind the apron.

    So I'd appreciate ideas re: the bushings, hardened steel thrust washers and the aux oiling ideas.

    Rick
    Son of the silver stream ..... Bullet caster.

  • #2
    Rick,

    Instead of hardened steel thrust washers, is there space for a needle thrust bearing or similar?

    Ian
    All of the gear, no idea...

    Comment


    • #3
      With the gear dipping in oil, and the slow motion, I would suppose the lubrication is supposed to be from the oil off the gear onto the worm, and and running down the worm as it is turned. Wouldn't take much. Obviously the oil level has to be lower than the leadscrew holes.

      I am not very familiar with the "automatic " apron innards, although I have worked on similar S-B aprons. But, I would think that oiling should be adequate, so long as you "prime" it with lots of oil when assembling.

      Any chance (hah) that the damage was simply from being run "dry" sometime? That would score it up, but needn't be a long term concern.

      S-B ran hardened steel against cast iron for 60 years..... it works, in part due to the nature of CI. I do appreciate the idea of a dissimilar metal though... steel on steel unless one is hardened seems less than perfect.

      Can you turn down the gear shafts, or polish them, and re-make new caps with a bronze liner?
      1601

      Keep eye on ball.
      Hashim Khan

      Comment


      • #4
        Originally posted by Buckshot
        One of my reasons for asking is that the rest of the machine is fairly well outfitted with impregnated or oiled bronze bushings. Why not here? Why steel on steel?
        Logan often used steel shafts in iron (not steel) journals - a perfectly workable combination in that application. Both ends of your leadscrew probably run in iron journals too.

        Comment


        • #5
          Logans

          What I did to mine (14" logan) was, cleaned up both sides of the worm and made two new bronze bushing cups to fit.

          It worked really well. Here is a photo of one of the old bushings..

          That bottom of the 'cup' was about a 1/4 inch thick on the new bushing, so you can see how worn they were. The other (forward feed) bushing had broke though the bottom, this is the reverse feed bushing.

          Forward feed bushing...



          uyk.
          Last edited by Kenb; 07-23-2006, 04:30 PM.

          Comment


          • #6
            While not a Logan I did have the same sort of problem on our old Hendey lathe at work.It had the same scored and worn thrust faces,but little wear in the bore.

            It did have about 1/8" of endplay between the worm and the housing bores from the wear.This condition is what causes the delay between ingaging the feed and the carrage actually moving.

            I made up a boring bar to fit in the caps and fitted it with a tool bit so I could hand crank it and clean up the thrust faces flat and smooth.Once I had that done I measured the endplay and made two hard bronze washers one for each side of the worm.

            The effect was reducing the ingagement delay from 3-4 seconds to 1 second or less and since the bearing surfaces are now smooth there is less strain on the tumbler gears.

            Personally I wouldn't worry too much about the bores,I would correct the thrust faces thou.

            As for lube,the Hendey just has a dip pan for the feed gears,it uses way oil for the lube 300 ssu to be exact.That stuff is very sticky and climbs the gears well so lube isn't a problem,unless I forget to fill the pan.

            It also has a plunger pump that is driven off a cam on the apron gear which feeds the ways and crossslide gearing,but only when the carrage feed is ingaged.

            If your Logan doesn't have a pan,I would look for a way to add one.

            Hope this helps.
            I just need one more tool,just one!

            Comment


            • #7
              ...........Thank you all for the replies and especially to kenB for those photo's. Those bearings look like the steel bearing caps on my 11" lathe. As mentioned both the worm and steel caps are scored and worn on the thrust shoulders.

              J Tiers, "Any chance (hah) that the damage was simply from being run "dry" sometime? That would score it up, but needn't be a long term concern.'

              HA! The guy I bought my lathe from uses a '50's era 11" Logan. I noticed the pipe plug in the bottom of the apron and a screw on top with "OIL" stamped next to it. I asked if there was supposed to be oil in the apron. He said yes, but don't worry about it because it all leaks out! Rather then take his advise I did put oil in and over a weeks time you'd have to add maybe an ounce to bring it up. The apron halves aren't gasketed so the oil does slowly ooze out.

              Engageing the clutch was like Wierdscience said, it takes considerable time for the carriage to begin moving especially if feeding slowly.

              I don't know if a needle roller thrust washer would work due to the thinness of the working area they'd have to fit. The ends of the bearing area, or faces on the ends of the worm gear are only maybe 0.100" wide. Maybe a tad more but picturing them in my mind seems to be about that. This thinness was the reason for the idea of hardened steel thrust rings inside the bearing caps.

              An idea that just floated through my head would be to turn down the existing rough bearing surfaces of the wormgear and then sleeve them. The sleeve could have a shoulder internally at the ends to make a wider thrust area. The bearings cap ID's then bored smooth to match. This would also increase the width of THIER thrust surfaces. It would leave no room for a bronze bushing, but since I only paid $14 for the blanks, I can use them later on for something else.

              I suspect if the steel on steel lasted 25 years, and the new fix is as least as long, it will certainly be good enough!

              Again, thanks for the replies!

              Rick
              Son of the silver stream ..... Bullet caster.

              Comment


              • #8
                .............I got the wormgear repaired:



                At the extreme outside are the bearing cups (for lack of a better name) that are carried in ears off the rear of the apron. Next in are the sleeves I made and then the wormgear. The sleeves were just off having to be pressed on. I heated them in the oven, smeared threadlocker on the wormgear and then ran the sleeves on.

                The next day I took the pieces back to my buddy's house. He also has an 11" Logan and I used it to do the work. I used an expanding arbor held in a Buck 6 jaw adjust tru and a center on the other end. I took readings off the top of the wormgear threads then took a small skimcut of a couple thou off each sleeve, to make sure they were true to each other.

                Then each bearing cup was put in the Buck and indicating off the outside were dialed in and bored for a .003" clearance over the sleeves.



                All finished, before installation. You can see the dissimilar finish between the 2 metals of the wormgear and the sleeve. I don't know what steel the wormgear was made of. The sleeves were made from W-1. The caps and the sleeves were bored using a new Circle C carbide insert 3/8" carbide boring bar I'd recently bought on sale from Enco. I think the end caps are cast iron. At least they turned that way.

                Oiling alterations: As JTiers suggested I suspect oiling of the sleeves is accomplished via the oil carried up to the wormgear by the driven gear in the apron. The oil finding it's way from the worm out to the sleeves. I admit I'm an 'Oilaholic'. If a little is okay, a lot is a dang sight better.

                I installed the new wormgear and bearing cups, marked their position allowing a couple thousandth's play end for end, then removed the wormgear. I had bought a piece of 3/16" (.1875") steel brake line. I used a #13 drill (.185") to drill through the ears off the back of the apron and through the bearing cups. I then drove the brakeline into each hole and formed them around the back of the apron, over the split nuts and around to the rightt front of the apron.

                I used a piece of 1/2" keystock as a terminal for the 2 oiler tubes. I drilled two 3/16" holes through the block, reversed it and counterbored .246" to accept 2 Gitts ball oilers. The block was then clearance drilled for a 10-32 sockethead screw which threads into a tapped hole at the edge of the apron. The oil lines were soldered in thier holes, the oilers installed and the block was attached to the right front of the apron. The threadchasing dial clears the tubes nicely. I can now deliberately apply oil to the bearings. I will show photos when I get them uploaded to the net.

                True to being an oilaholic, while the carriage and QC box was off I performed the oiling alterations JTiers did to his Logan's saddle, which allows oil to be applied under it. I also applied Gitts springtop oilers to the QC box bushings. I'm happy now that I can apply oil directly to places where before it was supposed to merely suck in, I suppose :-).

                Rick
                Son of the silver stream ..... Bullet caster.

                Comment


                • #9
                  Tradition

                  That's the way to do it. Keep up the good work. Save as many machines as you can. ......Did I ever tell you machines are what created society as we know it????????????????????????????? oh, yeah, don't forget the machinists.

                  Comment


                  • #10
                    ..........I got the pics of the oiling mods to the apron uploaded.



                    Hole 'B' was drilled through the mounting ear and through the bearing cap. It was then tapped 8-32 to take a setscrew to seal it and also retain the oiler tube. Hole 'A' is for the oiler tube.



                    The oil tubes is 3/16" steel brake line I bought a Pep Boys. The hole in the apron was drilled .185" and the brake lines are .187". The drilled holes were naturally a tad larger then their stated .185" so the tubes were a nice press fit. They bend around to the front to a terminal block.



                    I hadn't installed the Gitts oilers to the block yet.The block is a piece of 1/2" keystock. Each end of the block was milled down for mounting screws. The side of the apron was D&T'd for 8-32 sockethead screws for attaching the block. The brakelines were soldered in the block. The threadchasing dial easily clears the tubes.

                    I'm sure the factory means of oiling the wormgear bushings was entirely satisfactory as it lasted 25 years so far. However this way I can also positively get oil to them. If a little oil is good, a lot of oil is better? Makes ME feel better anyway.

                    Rick
                    Son of the silver stream ..... Bullet caster.

                    Comment


                    • #11
                      Looking good,love the idea using the tubes.
                      I just need one more tool,just one!

                      Comment


                      • #12
                        Very nice work. I like what you did with the worm gear bushings. I might have put a shoulder on the "sleeves" to provide a new thrust point for lateral movement, but....maybe not. Definitely I too would have made them before paying 300 bucks. As long as the sleeves are softer than the gear, it should last through everything you can dish out.

                        Your oiling plan is elaborate but nicely executed. Did you put felt wicks at the bottom to "meter" the oil, or is it just flood oiling? Either way, it's good for 99 years at least.

                        Comment


                        • #13
                          forget the bronze bushings...

                          Hi! How are you today....I would forget using bronze for your bushing,Just use oil-lite bushings...they are self lubricating....no need for grease.If the worm gear is in fair condition...leave it alone....too expensive...you can make the bushings yourself.

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