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Ideas for removing small tight (maybe locktited) pins from cast iron table?

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  • Ideas for removing small tight (maybe locktited) pins from cast iron table?

    As advertised. Two pins in the end of a milling machine table. They are for aligning the feedscrew crank assembly.

    A previous owner may have been left handed, and must have cut off the pins flush when he moved the feed to the left end. I am right handed, and want the crank at the right had end, but the pins are cut. I want to replace them.

    They are around 0.187 diameter, possibly 0.203, I have not measured them, and are set in the end as shown. (Pic is poorly focused, I will try to replace it with a better one) At least one of them had the pin hole break into a void in the casting, which comes out to the surface, so methods using greaser pressure are not likely to work. And, I suspect the pins were locktited as well as pressed in, so I am not sure how well that would work anyhow.

    There is almost no pin sticking out, and no ledge in the recess, so very little way to positively center a drill decently over the pin to drill it out on center. No, it will not fit on the other mill's table in any way that will let me see it to check center.

    Because they are alignment pins, wandering a drill out into the cast iron would not be a really bright idea, the hole really needs to be down the middle. I suspect that I will need to pretty much drill it to a thin shell, because of the possible loctite, and the tight fit. I doubt that a jack screw of a size to go down it would be able to push it put. And I may not be able to drill through into a space under the pin, so threading to the end may not happen unless I drill way into the cast iron.

    About all I can think of is to make a drill guide plate, and then find a way to get it accurately set over the pin. But since it would cover the pin, I can anticipate a problem getting it aligned.

    I do not want to try welding on it, both because it may not work well with the small pins, and because I do not want to heat up and warp the table.

    So, aside from being very careful when drilling, are there any really good ideas out there?

    3751 6193 2700 3517

    Keep eye on ball.
    Hashim Khan

    If you look closely at a digital signal, you find out it is really analog......

  • #2
    My thought would be whether or not the pins are Really needed .The manufacturers would not have fitted them without reason, but if the reason was to simply aid quick assembly by unskilled folk then can you get round their loss by using time skill and cunning.
    . IF they really are needed to ensure alignment well you have to get them out somehow.
    But if they can be disposed of providing you can get the bracket to the proper place then how can you ensure the bracket goes where it should.
    I am guessing the bolt holes in the bracket are big enough to allow some movement of the bracket, even maybe they are as cast and well oversize.
    Is the difference in colour between the pins and the cast of the table enough that sighting through the holes( for the pins) in the bracket, after carefully enlarging them about 30 thous,and bolting up tightly once they are sighted as centrally as possible a possibility. Maybe careful smearing of marking out blue might help show up the pin ends,
    Those are my first thoughts.
    Regards David Powell.

    Comment


    • #3
      A lot of talk of drilling, tapping etc, what makes you think they are not hardened dowel pins? I am going to take a guess you checked.

      Welding on a extension to pull with is the best bet. A Tig welder is in no way going to heat that table anywhere near enough to cause warping ! Tig welding would also loosen up any loctite. Alternately, a nut could be TIg welded on, would also serve as a guide to protect the table during the weld. Show it to a real PRO at Tig and get their opinion.

      Another thought would be one of those stud welders they use for auto body work, they are used for pulling dents. Not sure of the stud size they use but the studs could be customized a bit too.

      First I thought of a bridgeport size table but its obviously a lot smaller. The best, although not the cheapest or easiest would be to have they EDM'd out. Nothing beats a EDM for removing broken taps, dowels, bolts etc.

      Years ago, I put a ballscrew kit into a bridgeport knee mill. The instructions said to toss the dowels, they were not needed and had to be removed to align the screw properly. Thats your final option, although one you won't want to do, ignore them and proceed. They are for ease of reassembly without the need to align each time. If that table has been reconditioned, the dowels are probably no longer in the right position anyway !

      Keep us posted on the final solution !
      Last edited by Sparky_NY; 11-25-2020, 07:47 AM.

      Comment


      • #4
        If that job landed on my desk at work, I'd stand it up on end and interpolate them out in the CNC with a 1/8" carbide endmill (if I had the Z height). Dowels are hard, but not that hard.... Probably 2 hours tops, from hello to goodbye.

        If I had to do it at home, id hit it with a torch to bust the loctite, and try and tig on a nut, stud or something to grab onto the pins. Failing that, I'd try and peck drill it out with a carbide endmill, running against the depth stop all the way down. You don't have to go for center, in fact if you go outside the lines a bit it will allow the pin shell to collapse, and you will still have more than plenty of hole left for proper alignment.

        Not sure what you have to work with, but that's how I'd do it with what I have.

        Just thought of another way that might work while typing. I wonder if a body stud welder would be able to tack a couple pins on there to pull out? The fact they're loctited make me think the hole itself is actually a slide fit, and if you could break down the bond, and get something stuck on there it should be an easy pull. Drive around to a body shop with a box of doughnuts and see if you can get somebody to stick a couple studs on for ya. The small amount of heat generated to tack something on there will be no problem for table warpage.

        Comment


        • #5
          Originally posted by David Powell View Post
          My thought would be whether or not the pins are Really needed .The manufacturers would not have fitted them without reason, but if the reason was to simply aid quick assembly by unskilled folk then can you get round their loss by using time skill and cunning.
          I had a similar thought. On one of my small CNC mills the pins were actually putting a slight bind on one of the bearing carriers for a ball screw when that end of the table approached the saddle. I removed the pins, and used the ball screw's natural tendency to want to be straight to position the carrier before snugging down the mounting bolts. The machine runs faster without binding. The pins were actually causing problems.
          *** I always wanted a welding stinger that looked like the north end of a south bound chicken. Often my welds look like somebody pointed the wrong end of a chicken at the joint and squeezed until something came out. Might as well look the part.

          Comment


          • #6
            Stand on end, centre punch pin, drill down with 11/64 drill using a hand/battery drill. This should loosen up the remains. If the pins are hardened, you're stuffed anyway.

            Mark and drill new pins locations on the end plate, get everything lined up, then drill out new pin holes. Don't use loctite this time.
            'It may not always be the best policy to do what is best technically, but those responsible for policy can never form a right judgement without knowledge of what is right technically' - 'Dutch' Kindelberger

            Comment


            • #7
              Looking at your picture, I would drill a 1/4 " hole from the top ( coming down in pic) and about 1/2" back from your end surface ( crank mounting surface) and go maybe 1/2" deep
              That area is not a critical machined surface on most mill tables ( usually Blanchard ground) .
              Most dowels are placed at 2 x diameter in depth, and you want to access the area just beyond the end of the pin inside.-- besure you intersect with the pin hole ! that is the important part
              carefully fill it with grease ( minimum air pockets) and place a 1/4" dowel ( flat ended if possible) in the hole and wack it with a big hammer. Have the inverted table on a flat hard surface
              The pin should spit out easily
              No Heat needed, no welding
              Rich

              wear safety glasses
              Green Bay, WI

              Comment


              • #8
                if welding isn't an option for whatever reason, I'd make up a drill jig plate using those 2 threaded holes to secure it. I'd make a hardened drill bushing for a center cutting endmill of an appropriate size to get the pin surfaces approximately flat, then swap that out for a different bushing to drill it for a suitable tap. Then heat the snot out of the pin with a torch to loosen any loctite and jack it out with a screw. Alot of prep time but the actual process should be relatively straight forward.

                Comment


                • #9
                  Originally posted by Sparky_NY View Post
                  A lot of talk of drilling, tapping etc, what makes you think they are not hardened dowel pins? I am going to take a guess you checked.

                  Welding on a extension to pull with is the best bet. A Tig welder is in no way going to heat that table anywhere near enough to cause warping ! Tig welding would also loosen up any loctite. Alternately, a nut could be TIg welded on, would also serve as a guide to protect the table during the weld. Show it to a real PRO at Tig and get their opinion.

                  Another thought would be one of those stud welders they use for auto body work, they are used for pulling dents. Not sure of the stud size they use but the studs could be customized a bit too.

                  First I thought of a bridgeport size table but its obviously a lot smaller. The best, although not the cheapest or easiest would be to have they EDM'd out. Nothing beats a EDM for removing broken taps, dowels, bolts etc.

                  Years ago, I put a ballscrew kit into a bridgeport knee mill. The instructions said to toss the dowels, they were not needed and had to be removed to align the screw properly. Thats your final option, although one you won't want to do, ignore them and proceed. They are for ease of reassembly without the need to align each time. If that table has been reconditioned, the dowels are probably no longer in the right position anyway !

                  Keep us posted on the final solution !
                  That's what I would do, TIG / fuse a piece of rod or something to it and pull it out after it cools. A piece of 1/8" TIG rod fused to it would work and use a small slide hammer to pull / tap it out.



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

                  Comment


                  • #10
                    Is it imperative they be removed?
                    Can you move over a bit and drill new holes?
                    Len

                    Comment


                    • #11
                      The museum's drill mill has handles at both ends of the bed, and I soon added a handle to the left end of the Tom Senior bed. That way gives maximun versatility and can be useful when the chips are flying more in one direction than the other. I feel sorry for people who have two arms and can only manage to use one of them.

                      Comment


                      • #12
                        You will not have much movement of the plate when you assemble it too the table. The movement will be determined by the fit of the attaching hardware. Put the plate on, center the bolts in the holes as you tighten the bolts. Then check the operation. If everything works well, use the machine. If it binds, loosen the screws and relighted. If you feel you must have the pins, drill and ream holes away from the existing holes and put dowels in. Be sure to clean away the bit of pins above the surface. I will bet that it has been working on the other end without pins.

                        Comment


                        • #13
                          Originally posted by Jim Williams View Post
                          ........ I will bet that it has been working on the other end without pins.
                          How much did you bet? Cuz you lose..... the other end has pins (they are not hardened).

                          Interesting ideas.

                          My first thought when I found those was to wonder why the last owner did not just pull the pins while he had access to the end sticking out........ For some reason he cut them off as opposed to pulling them, so presumably they were not easy to pull. He did have a welder, and could easily have put a nut over them and done a good solid weld, the pins on the other end stick out almost 3/8".

                          "have two arms and can only use one of them"....... LOL.... I prefer to operate it from the right hand end, which is enough reason right there..... But I intend to put a power feed on the other end, so there is a second reason. It's not made to accept the usual power feed at the handle end.

                          The "grease-draulic" method of removal would be fine, but will not work on the one that has hit the blowhole. It would leak.
                          3751 6193 2700 3517

                          Keep eye on ball.
                          Hashim Khan

                          If you look closely at a digital signal, you find out it is really analog......

                          Comment


                          • #14
                            Cover the blowhole and clmpntge cover. If you have a bigger hole for the grease it can still work if you hit it hard enough, it will leak but may exert enough force to push pin out.
                            if table is 40 inch or less, easy to hold off side of table on a B,port type mill, swing head over to work..

                            The original end plate with reducer sleeve in hole, will that nit guide the drill ?
                            Last edited by 754; 11-25-2020, 04:32 PM.

                            Comment


                            • #15
                              “Here” mig welder would be first choice.

                              Not a real serious suggestion, but what about trepanning around the dowel with an annular cutter just deep enough to get a grip?

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