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Cutting a V-Grove Pulley

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  • #46
    Originally posted by Jim Stewart View Post
    Just a thought: why not build up the inside of the hole with JBWeld and rebore?

    -js
    Its not that loose. There would be no real place for JB weld. Like I said I can use it, but I think I may just try again. Mostly I was wondering if I can get more consistent results with a reamer and if so, do I machine mount it or do it by hand. I read somewhere on the forum that a floating reamer holder is best for holding a reamer in a lathe but I don't want to get that involved at this point.

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    • #47
      Originally posted by Jim Stewart View Post
      ...why not build up the inside of the hole with JBWeld and rebore?

      -js
      Ugh!

      I often simply chuck the reamer in a tailstock chuck. The extra stick-out I think helps with self-centering.
      12" x 35" Logan 2557V lathe
      Index "Super 55" mill
      18" Vectrax vertical bandsaw
      7" x 10" Vectrax mitering bandsaw
      24" State disc sander

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      • #48
        Originally posted by donf View Post
        A related question when boring the center hole I over shot the size just a hair. It is still usable, but I think I am going to redo and try for a tighter fit. Is it better to ream the last little bit? If so do I look for a morse taper reamer that held in the tailstock or it is better to ream by hand?
        So it goes like this:
        • A twist drill makes a hole that is neither on size, round, or in the right location.
        • A reamer makes a hole that is round and accurate, but follows it's pilot. If that pilot is out of position and crooked, so will be the final hole.
        • Single point boring creates a hole that is round, in the right location, straight, and may be accurate. The last part is up to the user.
        The technical correct way to use all three is to drill, bore, ream. If you do this procedure properly, your tools are sharp and ground correctly, your machine geometry is at least close to correct, then you will end up with a very good hole indeed. Often you can skip one step. It takes experience to know which, and when.

        I would definitely ream under power. Whether you use a chucking or MT reamer doesn't really matter. Chucking reamers are bit more versatile.
        21" Royersford Excelsior CamelBack Drillpress Restoration
        1943 Sidney 16x54 Lathe Restoration

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        • #49
          Originally posted by ezduzit View Post

          Ugh!
          A man of few words, I gather. Care to expand on your comment?

          -js

          There are no stupid questions. But there are lots of stupid answers. This is the internet.

          Location: SF Bay Area

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          • #50
            Originally posted by Jim Stewart View Post

            A man of few words, I gather. Care to expand on your comment?

            -js
            OK.

            If the damage from operator error was purely cosmetic, then yes, JB Weld would be fine. Since the pulley requires a specific bore size, which the operator missed, then the correct fix could be:
            start over
            re-bore and bush
            re-bore and install shaft adapter
            Possibly others, but definitely not "Bondo it up to size".
            12" x 35" Logan 2557V lathe
            Index "Super 55" mill
            18" Vectrax vertical bandsaw
            7" x 10" Vectrax mitering bandsaw
            24" State disc sander

            Comment


            • #51
              Thank you for the lessons. It helps a lot! I will order a reamer and try a few practice holes.

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              • #52
                Originally posted by ezduzit View Post

                Ugh!

                I often simply chuck the reamer in a tailstock chuck. The extra stick-out I think helps with self-centering.
                Agreed with EZ.

                You actually don't want a reamer to be "too rigid". JTiers can and probably will fill you in on floating reamer holders shortly. But sometimes morse taper (shank) reamers can be a little too stiff and cut oversize when following a drilled hole. Chucking reamers have less of that issue.
                21" Royersford Excelsior CamelBack Drillpress Restoration
                1943 Sidney 16x54 Lathe Restoration

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                • #53
                  Correct; the bottom of the V is always flat unless its a NASA special. Short and simple measure the belt , width, & angle and the flat bottom of the belt. Then with any point tool transfer those measurements to the stock. Then I hog out the flat bottom parting tool the width of the belt..
                  set my compound at the degree of the belt and let her rip doing both sides but keep things a little proud cause you can always go back for a final cut: the belt should be flat with the pulley at the top and the bottom of the belt should not touch the flat bottom. Just picture how a snowmobile centrifugal clutch works. What you are looking for is full contact of the belt and the pulley.....sam
                  Last edited by big job; 07-20-2021, 11:14 AM. Reason: spelling

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                  • #54
                    OK I finally got back on this under drive pulley project. I used the material that was a goof, slightly oversized but possibly usable just to practice on and see what kind of problems I ran into. I ran into a few. https://www.amazon.com/gp/product/B01LTFCPYS is an expanding mandrel I purchased.

                    It actually works, but if I take any sort of real cut, it spins and gets loose. 0.25mm or .01 inch cuts are about it. Those fine cuts seem to be fairly consistent though. I wedged in on hard with a plastic hammer, but the pully stock is aluminum. It sort of moves and just expands with the hole when its wedged super tight over a few passes. It spun several times and now the slightly oversized center hole is full on sloppy and not worth finishing. For my next attempt, I think I have to do most of the work in a chuck and then mount it only for final truing and making the v cut? Taking 0.25mm cuts takes forever to remove material. My other thought is to make an aluminum arbor and tack weld the round stock on there only cutting it off when the pulley is done and then final sizing the center hole. Its a learning part. I would like to be able to learn how to make them with reasonable accuracy. The only parts I have done over the years have been non critical. The finish when cutting isn't so hot. I am getting better results with hand ground mild steel than import carbide. Its a "C" model Boxford so the cross slide is not powered. I can see the difference between the finishes as the other axis is power feed. Here is a drawing of the one made in the 80s by King Motorsports. There is a lot of material to remove. I was not going to make mine that thin by the crank bolt though.
                    .
                    Attached Files
                    Last edited by donf; 09-21-2021, 10:37 PM.

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                    • #55
                      I recently made a poly V pulley a bit bigger than that. I held the pulley by the outside of the hub, partially cut each V, then went back for light finish cuts. Once that was all done, I drilled and bored the center hole, so in theory (!) the V grooves should be concentric to the shaft. Another way I had considered was drilling the hole first, then turning a short shaft down between centers to the hole size. Pulley would be secured by set screws, same as would secure it to the countershaft. Probably would have been more secure that way, but I was lazy.

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                      • #56
                        I would hold the round blank on the OD and finish all the V-groove features plus the bore. Then flip it end for end and turn the hub.
                        12" x 35" Logan 2557V lathe
                        Index "Super 55" mill
                        18" Vectrax vertical bandsaw
                        7" x 10" Vectrax mitering bandsaw
                        24" State disc sander

                        Comment


                        • #57
                          Originally posted by ezduzit View Post
                          I would hold the round blank on the OD and finish all the V-groove features plus the bore. Then flip it end for end and turn the hub.
                          Or finish the hub and then turn all the V-groove features and the bore. First option has better holding power though. Either way, there is no reason to use an expanding mandrel on this. It will only make a worse part.
                          21" Royersford Excelsior CamelBack Drillpress Restoration
                          1943 Sidney 16x54 Lathe Restoration

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                          • #58
                            Thank you for the education. I will give it another shot this week sometime.

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                            • #59
                              Its isn't that difficult. I recently made several vee belt pulleys from aluminium stock, ranging from 2" OD to 7 1/2" OD, on a 100 year old 8" lathe (4" centre height) I'd chuck the stock, turn the vee profile, do the bore (Drill, bore, finish ream), then turn over and do the hub. Doing the vee, I ground a profile tool from a 1/2" HSS blank, roughed out the groove to full depth with a parting tool, then went in with the profile tool, one side at a time, until it was just shaving full width, full depth.
                              '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

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                              • #60
                                Take a new V-belt and bend it in the arc about the same size as the sheave/pulley you are going to use. You should see the sides of the belt bulge outward. The belt attempting to bulge is what gives it traction. Or look at a worn out belt and you will see the sides are concave instead of straight. A worn out pulley/sheave will not have straight sides but will be concave as well.

                                The angles are not as critical but should be close. The belt should never touch the bottom of the groove.

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