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tp grinder pics

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  • tp grinder pics

    Thought I'd post a pic or two of another lathe accessory, one of my tp grinders.

    There it is sitting on the crosslide. There's only one t-nut used to hold it right now, but in use I use both t-nuts.

    Here's a view from the business end. From this pic you can tell that it's 'geared up' to the spindle, and the drive is an 0-ring.

    This pic shows the bolts that allow for tilt adjustment. I loosen the two socket head screws, then loosen the bolt just enough to allow the motor/spindle assembly to tilt left or right. You can see two slots under the cap head screws that allow a range of adjustment.
    At the time I wanted to experiment with grinding threads, and of course because threads are angled, I needed the adjustment. It does the job, but my v cutter blade need to be properly sharpened.

    Otherwise, the tp grinder setup works fine. I have a few different mounting adapters made for it, so all the wheels that came with the Unimat can mount, as well the standard 3 inch cutoff discs can mount. I have a tray that mounts under the wheels and moves with the carriage to collect swarf.

    At the rear you can see the motor. It's a dc motor, built up (by me) from three satellite actuator motors, using all the magnets and all the rotor laminations. I wound it by hand, tied and epoxied the windings. Balance was pretty good right away, and further balancing was done by dripping epoxy onto the windings in the right spots. Yes, I guess I'm one of those guys who likes (as someone aptly put it) "entangling oneself in yards and yards of magnet wire". The motor has so much torque that I can get away with a step up ratio from motor to spindle. If I crank up the speed, the o-ring grows to about the size of my granny's waistline Well, maybe not quite that much.

    Just behind the spindle pulley you can see a guard that rotates with the spindle, and closely clears the housing. I don't know if it was needed or not to protect the bearing, but I thought it would at the time, so there it is. I used a novel method of preloading the bearings, and that's the nylon bushing seen at the right end of the spindle. I could have used a bellville washer, but I figured the nylon would have some squish room, and it seems to be doing the job.

    I'll post some pics of other projects if anyone is interested.
    Maybe the centrifuge-
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

  • #2

    Your use of satellite motor components raised another question in my mind. At a local used stuff store there are a bunch of ceiling fan motors. What might these be useful for in the shop context?
    "People will occasionally stumble over the truth, but most of the time they will pick themselves up and carry on" : Winston Churchill


    • #3
      Very nice work!!


      • #4
        Very nice setup. I can really use something like this, thanks for posting.



        • #5
          Daryl, that's one of the nicer TP grinders I have seen to date. By all means, show some more projects!



          Try G-Wizard Machinist's Calculator for free:


          • #6
            Good post and nice job on the execution. Looks like it could be a very useful tool.

            Got any ideas for a cutter welder? LOL Most of mine snap long before they have the need to be sharpened !!
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            Thank you to our families of soldiers, many of whom have given so much more then the rest of us for the Freedom we enjoy.

            It is true, there is nothing free about freedom, don't be so quick to give it away.


            • #7
              Yeah more pictures of other projects would be great


              • #8
                Nice job! The body looks pretty solid. Have you tested the finish on something? I'm wondering if the belt on the wheel side will transmit any vibrations?

                Your next project should be fabricating a cover/guard for the wheel and belt. After my belt came apart during a grind, that was moved to the top of my list.


                • #9
                  Motor winding similar to Generator?

                  Hey; while I'm thinking about it, how did you go about winding the armature? I've got three generator (DC) armatures I need to rewind. I pulled one lead from the commutator and it looks like the windings are overlapping. How do you keep track of all the wires?


                  • #10
                    Thanks for all the kind words.
                    It's capable of giving a pretty good finish, but is obviously not up to par with what a real surface grinder can do. With the right wheel (and this white one is pretty good) I can grind a finish that won't catch a fingernail. That's a pretty vague description, but another way of comparing it is to a fly cut surface done on a mill. I can get something in the same ballpark.

                    I most often use this tool with the 3 inch cutoff discs, which is what I use when machining on rubber parts. I used to re-surface pinch rollers a lot, and this gave a very smooth result. Very messy though, and nasty to be around. I would usually make a few passes while holding my breath, then scoot away for some fresh air.

                    One of my next projects will be a diamond surfaced disc for the tp grinder. Should be interesting. I have some of that stick-on diamond coated sandpaper to try.

                    As far as winding the armature- I can't remember when I did my first one, but I was not yet a teenager. It has almost become second nature for me to wind one, but still I start by making a diagram of the existing windings. Find where the outermost winding is, which will have none of its turns under any other winding, then note the comm segment it's fastened to, and the pole that it begins to wrap around. You need to keep that relationship the same when you rewind. Note also how many poles are included within the winding loop. There will probably be two windings which are totally outer, and they'll be opposite each other. Most often now I unwind one of these coils, noting these things, and also the number of turns and the gauge of the wire. From this I can determine how many turns I want on the new winding, and what the gauge can be to keep the slot fill ratio about the same for the lowest reasonable winding resistance. After making notes, I just hack away the rest of the wire as best I can, without damaging the commutator. Ken, that armature looks like it's been well tied and glued- it'won't be a trivial task to rewind. One thing you might check- if there's an uneven number of comm segments, then the winding is harder to keep track of (at least it is for me).

                    Windings are usually put on in opposites, which is to say that you would start two wires, fastened to opposite comm segments, then put the first winding on with each wire, alternating them as you go around the rotor. This way you're getting and keeping a close balance as you get all the windings put on. Obviously the outer coils will be farther from the core than the first coils, so to have a chance at balance, you have to try to keep some symmetry going on.

                    There's more to it than that, one other thing being that you need to make sure every coil you put on has the same number of turns in it. No doubt about it, the process is a time consuming chore, and certainly can be mentally taxing.
                    Ceiling fan motors- I've tried, but those aren't good for anything other than- well, ceiling fans.
                    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-


                    • #11
                      darryl... nice job. What did you use or how did you make up the spindle.
                      Wow... where did the time go. I could of swore I was only out there for an hour.


                      • #12
                        I had a brainwave one day of how I could make the shaft and the bearing diameters concentric. I started with thompson shafting, chucked one end and used a steady at the other end. I center drilled, drilled, and tapped for the 1/4-20 bolt, then turned the bearing diameter there. Turned the shaft around and did the other end the same way. I shimmed the shaft at the chuck to make it run as true as possible there. The shafting was nicely round to start with, so the steady worked well. I did pay some attention to whether or not the piece I was using was bent at all.

                        I made the business end for a tight press fit of the bearing, and the other end for a light press fit. At the business end, the bearing is kept seated in part by pressure from the wheel mounting bolt. The bearing fit to the housing is also tighter at this end. When I turn the bolt on the other end, I'm pulling the shaft through the bearing inner race, (the nylon bushing is hollowed for a short length of the shaft to come into it) and pushing the outer race into it's recess and up against a shoulder in the housing. The bearing doesn't come up to a shoulder on the shaft at this end. I can feel and hear the range of preload build up as the bolt head presses into the nylon. I should probably check this adjustment now, it's been awhile.

                        The business end of the shaft also extends past the thickest wheel I have, so a special washer can fit concentric to the shaft with little play. The brass washer you see is recessed a short distance so it can also be concentric when it's there holding the wheel on.
                        I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-