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Attempting to make an L-00 mount spider chuck, trouble boring the proper taper

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  • Attempting to make an L-00 mount spider chuck, trouble boring the proper taper

    Attempting to make an L-00 mount spider chuck, trouble boring the proper taper

    I am attemting to make a spider chuck to attach to the L-00 spindle on my Sheldon lathe. When I began planning this project, I assumed that boring the taper just right would be the most difficult part. It turns out I was right. I began with a 4" round chunk of steel, 3 1/2" long. I faced both ends of it in the three-jaw, driled a 5/8" hole all the way through, and then bored a 2.25" hole, 2.10" deep. At this point, I removed the chuck with the workpiece still chucked, and mounted a .0001 indicator on my toolpost. I was able to adjust the compund slide while indicating off the far side of the spindle nose taper to less than a tenth. With the compound properly adjusted, I re-mouunted the three-jaw with the workpiece in it and bored the taper by hand cranking the compound (with the cairrage locked) until there was about 1" of tapered surface. I have a spare L-00 spindle that I picked up on ebay, and I put that into my tapered bore. With the taper seated, I was able to rock it a bit, telling me that my compound was not quite right. So, I removed the chuck again, and re-indicated off he taper nose, and I was still at less than a tenth. I put the chuck back on and made a few more passes with the boring tool. After every pass, I am putting my spare spindle nose into the bore, checking for it to seat without any rocking. I have not been able to get it perfect. I make 4 pases of the tool at the same setting each time, to make sure tool flex is not an issue. I can not get the angle perfect, the spare spindle 'guage' still rocks.

    How do I determine if I have my indicator tip set perfectly on the spindle centerline when I indicate the taper?

    How would you go about setting up to bore the taper perfectly?

    I have a lot more passes until I am at my full depth, so I have a lot more tries to get it right, but so far no luck. My adjustment method now has been determining whether my 'guage' is pivoting on the inboard (spindle side) of the bored taper, or the outboard end, loosening the compound nuts very slightly and tapping the compound in the apprpriate direction with light taps from a dead blow hammer. I have gotten the fit extremely close, but not perfect. At this point I am dancing on either side of 'perfect', but not quite there. I notice that all of my L00 chucks have the middle part of the taper relieved so that the spindle nose seats on the front and back of the taper. Could the fact that my bored hole does not have this relief yet be an issue?

    I am making my own tooling to rebarrel a Model 7 to 7mm-08. Once I get this chuck finished, I will only need to make a loating reamer holder (I am going to copy Butch Lambert's design) and I will be able to get started with that. But, this tapered hole is proving a whole lot more difficult to get just right than I originally thought.

    I appreciate any advice you guys can give.

  • #2
    Use the extremely close fit then blue and polish to a final fit.

    Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.


    • #3
      Sounds like two possibilities.
      1) (less likely but still possible) your test spindle taper is slightly different than the one in the lathe.
      2) when you're indicating to set the compound, you need to be as exactly on the centerline height as you can get. maybe make it so you can raise/lower the indicator once it's in contact with the taper and move it until you reach the apex of the indicator's travel, which is most pronounced out at the smallest end of the taper.

      Then when you're turning, make sure the cutter is also as exactly on the centerline as you can get.

      Either of these being off will cause an error. If the tool is above or below the centerline, you'll be cutting a slight parabola (conic section).

      And of course the turning itself isn't likely to be absolutely flat, having ridges and valleys so it will pivot on the ridges. At this point you do as John suggested and polish to final fit.

      One more suggestion: I have some back plates that instead of a solid tapered bore have a relieved area in the middle - maybe about 1-inch across. This helps the female match up with the male a little more solid touching the outer and inner faces of the spindle nose taper instead of having to match the taper across its whole length.
      You've probably seen similar on Morse taper shanks:


      • #4
        Yes, my existing chucks have that relieved area, and since I have not cut that into the tapered bore yet, I wondered if it could be a problem. I hear you on getting the proper center height, I belive ihave it correct with the tool, but getting it dialed in properly with the indicator tip is where I am unsure how to get it at just the right height. The spare spindle I am using as a guage fits perfectly in all of my L00 chucks, it seats solid with no movement, so I'm pretty sure its good to go. Could I possibly use it as a lap to get my tapered hole just right after I have it bored 'extremely close"?


        • #5
          Tapers can be difficult to fit especially when cutting tapers with the compound which in most lathes doesn't track straight when run close to limits of travel.

          Even a small spindle is unwieldy for taper fit checking. Use a bungee cord or spring to support the weight at the right height with plenty of easy bounce. Then your feel will be more sensitive. Use blue. Follow one side of the taper in until it seats. Give it a small part of a turn to make the print. Don't wobble it around because it will leave false indications. Examine the blue indications and proced accordingly. You may end up polishing out the high metal. Use a brake cylinder hone or a stone style glaze breaker stroking rapidly. This will cut efficiently and will not blur edges or round off corners is used correctly (run no more that 1/4 of the stone length off the edge). You may have to use an individual stone or scrape to acheive the final fit on your spindle. It shouild fit within 0.0002" of the spindle taper fitting snug on the small end to full fit.

          Here's the point where I repeat my standard rant on the necessity of making spindle gages for all your shop equipment. If you have a gage you can quickly make up spindle tooling for what ever need you have. If you don't it's like running a race with one foot caught in a bucket.
          Last edited by Forrest Addy; 05-20-2012, 08:14 PM.


          • #6
            As I posted on the BR Central forum. Get a L00 backing plate and bolt on a piece of aluminum and make your cathead. You gain nothing but a heart ache and a lot of time spent doing it from scratch. Email me and I will send you photos.


            • #7
              Thank you Tyrone, Forrest and Butch. I actually do have a spare L00 backing plate, and I also have a stainless 8" pipe blanking flange. The flange is just under 1" thick, and I had planned on doing as Butch mentioned with it after reducing the diameter to 6" or so. But, as this is a hobby of mine, done for pure enjoyment and the satifaction of making things myself, I decided to try and make the whole thing in one piece. The time and heartache that may be incurred if I fail will be chalked up to lessons learned.

              Using prussian blue, what is the correct way to apply it to the part? I have a small tube of it, but it seems to be relatively thick. Would a shoe polish dauber be a good brush for applying a thin coat? In the past, I have used a magnum Sharpie marker as a marking compound, but never on something requiring this type of precision. It seemed to work pretty well, is it an acceptable substitute?


              • #8
                Spread it with your finger.

                The film is about right when the color is vivid and you can still see the underlying finish. Most any firm absorbant that doesn't shed particles or fiber will work - a scrap of leather or cleanly cut felt (vacuun off the fluff from the cut surface). A firm fine brush or any other method will work so long as the blue film is free of debris.

                I use a roller for areas but in small applications I bite the bullet and use a finger to spread blue. Blue cleans off with most any petrolem silvent but you can practice safe bluing by using a rubber glove. .


                • #10
                  When you rotate your taper to correct the angle don't tap it. Rather, clamp a long bar (like 3 or 4 feet) onto your tool post and use this to adjust the angle of the compound. You'll be able to make more minute adjustments as the end of the long bar will amplify your accuracy.


                  • #11
                    Use a dial indicator so that you have a knife type point on it, like a blade, for example 10 mm wide. This way you can be +-5 mm from the centerline with your indicator and still get the correct result, as the knife edge travels always at the apex of the taper.
                    Amount of experience is in direct proportion to the value of broken equipment.


                    • #12
                      Originally posted by 914Wilhelm
                      When you rotate your taper to correct the angle don't tap it. Rather, clamp a long bar (like 3 or 4 feet) onto your tool post and use this to adjust the angle of the compound. You'll be able to make more minute adjustments as the end of the long bar will amplify your accuracy.

                      Yes indeed, quantify your corrections, Measure the movement of the gage in the bore and work the ratio and proportion from the length of engagement to determing the amount of adjustment. Remember the wiggle is total taper error and the adjustment is on the half angle. Don't sneak up on it. Adjust by the full amount you calculated from measurements and reading you have confidence in. Adjust bit by bit and the taper will grow by tin=y stages to as broad as a bucket and will never fit the gage.

                      Make sure the compound gib is properly adjusted. If there is any clearance the slide can easily drift under light cuts where cutting forces are too small to solidly seat the slide against the dovetail.

                      There are other ways to check a taper angle. My favorite is to make a gage of two hunks of sheet metal about 2/3 in width of the small end of the taper. Rivet in a snugly drilled holes near one end at a point to make a hinge. When the gage is opened to fit the tapered bore, the rivet acts as a firm joint resisting unwanted movement. Tap the fake gage in the taper so it centers and both edges solidly meet the taper walls. Extract the gage and, handling it carefully, check its angle with a sine bar. When carefully managed this test will determine total taper angle to the small arc seconds.
                      Last edited by Forrest Addy; 05-21-2012, 06:54 AM.