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Line Boring Bar Completed!

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  • Line Boring Bar Completed!

    I finally finished up my line boring bar. I am very happy with it, but I had to throw every trick I knew to get what I wanted.

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    Specs:
    • 1.25" diameter
    • 24" straight section
    • MT4 taper
    • Up to 11.5" long bore
    • Dual purpose, lathe, drill press, etc
    • Fully ground
    • Diameter consistent to within .0005" for 98% of the bar
    • ~0.0002" concentricity
    • 3 Thou runout on the end when unsupported in the lathe
    • 6 holes spaced 2.2" apart
    • Not hardened unfortunately
    I wish I had a follow rest and could have turned it. But without one, I ended up grinding it to keep the deflection down. Man did I have to fight every variable in the book to get those numbers on a 40 year old manual lathe! I re-leveled it to <1 line on a .0005"/ft level. I did all my grinding between centers. I ground the headstock center installed so it would have zero runout. I used a MT2 tailstock center that had a known .0002" runout. I adjusted the tailstock 3 or 4 times until I was reading within a few tenths end per end. But even then I had high and low spots in the bar. I'm still not 100% sure of the cause of this, but I finally figured out I had to step grind (like step scraping) until it was all even. I learned that a little too late and already had some areas a little low or I could have done better on my diameter consistency. Even then I had started grinding with 10 thou stock remaining on a lot of the bar. I ended up taking a bit more than I expected to get the fit I wanted on the bearing. Seems like 5 tenths low is a good fit. It is a snug slip almost everywhere, there is only a few places it move on it's own. Of course being a soft bar, it's gonna wear like mad.

    ----------

    This guy was an absolute workhorse.

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    Many thanks to a friend for loaning it. It would have taken me a decade with our No 14. Still a bit underpowered, but capable at least.
    Last edited by The Metal Butcher; 07-11-2021, 02:10 AM.
    21" Royersford Excelsior CamelBack Drillpress Restoration
    1943 Sidney 16x54 Lathe Restoration

  • #2
    If you could see in the above pictures there is some funky patterns going on. I'm assuming that is due to wheel hop because of balance. I know my wheels aren't balanced and these old, well-used grinders probably aren't either. The 5" wheel was a lot worse than the <2" I used to do the taper with the little TPG. But they both exhibit it. I dunno. Tell me what you think in these photos.

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    <2" Wheel

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    5" Wheel. The highlighted pattern is the high spots burnished off by the bearing.

    I know surface grinder wheels can be balanced, but I'm just not sure that is possible with TPG wheels that don't really mount that accurately. I did have them dressed, so the runout was not an issue. It's certainly not the best finish. I've seen better turned finishes. But hey, I'll take what I can get! I almost didn't grind the taper, but it wasn't sticking well, so I re-calibrated the taper attachment and ground it. I'm glad I did! What a difference. Sticks good now and the Prussian Blue confirms it.

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    Welp, probably a huge waste of time over buy turned, ground, and polished but I couldn't find any that I could really work with, with it all being hardended. I probably have over 40 hours in this trying to get it right, but eh, who cares. I learned a ton! Still no master with a TPG but hey. I'm a lot better than before.

    Lastly, I know I'll get a few comments about dust. I did not guard or shield against it. I find those to be in the way, dangerous, and not helpful. What I did do was:
    • Used a vacuum whenever dressing. Stone bits are far worse than metal.
    • Turned towards the tailstock, always. Any dust fell on the ways, but didn't get run over.
    • Wiped the ways with a WD40 rag before running back over them.
    • Had fresh, quality way wipers.
    Some of you may still scream. Don't care. It's a tool, made to do a job, which I used it for. I see no damage to the ways that wasn't already there. Use your judgement on what you are willing to put on your ways. I daresay that most multi-discipline shops will see more grit get ground into their ways from angle and bench grinders than my careful use of a TPG.
    Last edited by The Metal Butcher; 07-11-2021, 02:12 AM.
    21" Royersford Excelsior CamelBack Drillpress Restoration
    1943 Sidney 16x54 Lathe Restoration

    Comment


    • #3
      First question regarding the finish: what RPM were you running the lathe at? Were you running with or against the rotation of the wheel? Next: part of that finish problem looks somewhat like you were dressing the wheel too fast. That will produce a weird pattern like that as well, but it won't cause the chatter. I am fairly certain that's what caused the speckled appearance in your finish where the high spots rubbed.

      Regarding grinding dust on the lathe, I like to use a sheet draped over the ways and leading edge of the carriage. I spray it with aerosol lubricant like WD40 or similar to help catch and hold any grit and swarf. Last but not least I use a vacuum on the wheel guard.
      Last edited by eKretz; 07-11-2021, 02:25 AM.

      Comment


      • #4
        Originally posted by eKretz View Post
        First question regarding the finish: what RPM were you running the lathe at? Were you running with or against the rotation of the wheel? Next: part of that finish problem looks somewhat like you were dressing the wheel too fast. That will produce a weird pattern like that as well, but it won't cause the chatter.

        Regarding grinding dust on the lathe, I like to use a sheet draped over the ways and leading edge of the carriage. I spray it with aerosol lubricant like WD40 or similar to help catch and hold any grit and swarf. Last but not least I use a vacuum on the wheel guard.
        60-100. Against. (AKA lathe in reverse)

        I may have been dressing the wheel too fast. I know a quicker dress is more open and better for roughing. I have no idea how fast to dress. I didn't read up any beforehand, probably should have.

        I tried a vacuum on wheel guard, but cheapo duck-tape let me down. I wouldn't have really wanted to listen to it for >10 hours anyway.
        21" Royersford Excelsior CamelBack Drillpress Restoration
        1943 Sidney 16x54 Lathe Restoration

        Comment


        • #5
          NOT Slamming You, but by niw you know why buying a 400 dollar hardened and ground bar .. is not so bad..
          but hey.l bet You learned a bit and now know how and when to use a TPG.l.. good job..

          Comment


          • #6
            Against is good, but you were running way too slow for a 1¼" workpiece. Generally for finish grinding I like to run in the range of 75--120 fpm, especially if there's a little chatter problem. That would be closer to at least 300 RPM.

            Dress as fast as you want for roughing, you are correct that a fast dress gives you an open and cool cutting wheel. Dressing speed of about 10-12 inches per minute is about right for finishing as long as you have a sharp diamond. Running much faster will usually produce a very bad pattern like you got. Running slower is okay for an even finer finish but it will close the wheel up and could cause problems with excess heat and burning of the workpiece.
            Last edited by eKretz; 07-11-2021, 02:50 AM.

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            • #7
              Cool beans! That is exactly the type of boring bar I think we should have at work. I don't think hardening is going to change things much except for wear. My old boss used to order 1018 TGP and you'd be amazed how useful that stuff was, and dirt cheap too. BTW that's a *very* nice job on the taper, I don't think I've gotten one right yet. I always get them "close but no cigar"
              25 miles north of Buffalo NY, USA

              Comment


              • #8
                I think the hardened shafts are more resistant to weld spatter, and of course dings and dents...

                Comment


                • #9
                  Originally posted by 754 View Post
                  NOT Slamming You, but by niw you know why buying a 400 dollar hardened and ground bar .. is not so bad..
                  but hey.l bet You learned a bit and now know how and when to use a TPG.l.. good job..
                  For sure. But I would have still had to have modified it to fit my purposes. Also, thinking about it now, at least two days of that were spent making new pieces for the TPG. That will be worth it beyond just this project.

                  Originally posted by eKretz View Post
                  Against is good, but you were running way too slow for a 1¼" workpiece. Generally for finish grinding I like to run in the range of 75--120 fpm, especially if there's a little chatter problem. That would be closer to at least 300 RPM.

                  Dress as fast as you want for roughing, you are correct that a fast dress gives you an open and cool cutting wheel. Dressing speed of about 10-12 inches per minute is about right for finishing as long as you have a sharp diamond. Running much faster will usually produce a very bad pattern like you got. Running slower is okay for an even finer finish but it will close the wheel up and could cause problems with excess heat and burning of the workpiece.
                  I see. I did try it at 200 and at 375 but I ran into major issues where the bar started chattering real bad and left huge scallops I barely got out. I may have still been taking too much DOC at that point. I was also a little worried about it running eccentric due to being out of balance, but that may be unrealisitc.

                  When I looked at my wheel last night is was clearly contacting heavy on one side even with a even dress. I used both a 100 grit Norton and a 36 grit Dayton. The Norton did a better job.

                  I probably dressed somewhere about that speed. I didn't use powerfeed, so I wouldn't know. I didn't use a sharp diamond.

                  As per usual I get the advice I need after I finished haha. But that's on me, I haven't sought TPG grinding advice in some time.

                  Originally posted by nickel-city-fab View Post
                  Cool beans! That is exactly the type of boring bar I think we should have at work. I don't think hardening is going to change things much except for wear. My old boss used to order 1018 TGP and you'd be amazed how useful that stuff was, and dirt cheap too. BTW that's a *very* nice job on the taper, I don't think I've gotten one right yet. I always get them "close but no cigar"
                  Thanks!

                  To get the taper right I usually indicate in on a known good one. And I'm using a T/A, which helps a lot. So for this one, since I was grinding towards the tailstock (bar held mirrored of first picture) I did the following:
                  1. Took a piece of Aluminum, held it in the tailstock Jacob's chuck, and centerdrilled it.
                  2. Placed a number 4 hardened center with the tail sitting on a B&S 9 headstock center, and the center point resting in the aluminum.
                  3. Ran an indicator along the shank of the #4 center bumping the T/A around until it read zero.
                  4. Of course ground it, which eliminates toolpost pressure.
                  Finally, something I learned on instagram: For leadscrew-pusher lathes (I.e., not South Bends, ones where there is no positive lockup handle, you want to turn from big to small. If you turn from small to big, you tool pressure is pushing away, and your T/A is pushing away. So the exact position of your tool is indeterminate. It is in the slop of the backlash. Where as if you turn from big to small, then your tool pressure is pushing away, and your T/A is pulling in. Therefore you are always held firmly in regards to backlash. Dad has ours modified to lockup decently well, before it was terrible.

                  I hope that helps.

                  Originally posted by 754 View Post
                  I think the hardened shafts are more resistant to weld spatter, and of course dings and dents...
                  For sure. This one shouldn't see any weld spatter. It's not a mobile line boring bar. Meant to be used on machines for virgin bores or ones that have been welded up elsewhere.
                  21" Royersford Excelsior CamelBack Drillpress Restoration
                  1943 Sidney 16x54 Lathe Restoration

                  Comment


                  • #10
                    One more for the road: It's a real good idea to narrow the contact patch of the wheel by dressing it back to a narrow contact area or to use a narrower wheel when rigidity is an issue.

                    Comment


                    • #11
                      very impressive work! 1 1/4" might sound beefy but I bet it was still a little whippy in the middle over 24". Think of the scallops from grinding chatter/ balance issues as small oil retaining pockets - it's a feature, like flaking ways

                      Comment


                      • #12
                        BTW, forgot to ask earlier but what were the wheel hardness ratings? For finishing an OD or flat surface grinding I generally like a range of H through J, depending on the material, hardness etc. I think 100 for finishing is a little on the overly fine side - probably would have used a 60 myself. The narrower wheel would have helped you overcome some of that lack of horsepower too. Too bad you didn't get a chance to try some of these on the job!

                        Comment


                        • #13
                          Everyone says to grind with the work turning AGAINST wheel rotation, but for some reason I have always gotten better finish turning WITH the wheel, but slowly. Not sure why, could compensate for faults in machinery or technique, or even be coincidence.

                          Not sure what grinder you are using in the pic, I have a Dumore model 44. The pic looks like a larger model with a cartridge spindle.
                          Last edited by J Tiers; 07-11-2021, 10:33 PM.
                          CNC machines only go through the motions.

                          Ideas expressed may be mine, or from anyone else in the universe.
                          Not responsible for clerical errors. Or those made by lay people either.
                          Number formats and units may be chosen at random depending on what day it is.
                          I reserve the right to use a number system with any integer base without prior notice.
                          Generalizations are understood to be "often" true, but not true in every case.

                          Comment


                          • #14
                            Originally posted by eKretz View Post
                            One more for the road: It's a real good idea to narrow the contact patch of the wheel by dressing it back to a narrow contact area or to use a narrower wheel when rigidity is an issue.
                            Thanks!

                            Originally posted by mattthemuppet View Post
                            very impressive work! 1 1/4" might sound beefy but I bet it was still a little whippy in the middle over 24". Think of the scallops from grinding chatter/ balance issues as small oil retaining pockets - it's a feature, like flaking ways
                            So that's what got me. I turned the entire 29" section from 1.5" to 1.3" in two passes. 4 jaw on one end, tailstock on the other. No chatter. Then I drilled the holes on it. After that, I couldn't get it to stop chattering for nothing. With my sharpest HSS bit with no radius, I could barely take 10 thou. I'm not sure if it was the holes, the prior heavy cut keeping the pressure on it, a poor morse taper or what. But it was chattery as hell. Which makes me dubious how well it will work as a boring bar. I guess we'll see.


                            Dad polished the bar up for me with gray scotch-brite. Looks a lot better and he didn't really take anything off.

                            I then made two plastic bushings, a tight slip fit with a 1.5" OD. Those go in a 1.5" PVC tube with a cleanout on the end. Just 1/8" of slop at best, end to end. That should keep it safe and rust free. I didn't have any glue and the power went out, so I didn't get to take pictures. But it's easy to imagine.

                            I should try it out next weekend if all goes well. I'm excited!
                            21" Royersford Excelsior CamelBack Drillpress Restoration
                            1943 Sidney 16x54 Lathe Restoration

                            Comment


                            • #15
                              FWIW if you ever have to make another similar to this one... I can highly recommend using some chrome hydraulic shaft. It's already case-hardened, incredibly straight, incredibly round, chromed, and cheap. Dirt cheap. Get to know a tractor or heavy equipment shop and see if they'll spare some old hyd cylinder rods. They machine beautifully, I think the better ones are 8620 and the regular ones are 1030. Once you get through the case and hard layer it goes like butter with carbide. I always scrap-pick it when I can find it, it's great for tool making.
                              25 miles north of Buffalo NY, USA

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