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Thread: holding big stock on lathe

  1. #11
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    I think what the OP is wanting, since these seem to be anti-scalp wheels for a mower deck, is to crown the outside diameter so they don't tear up the grass while turning with wheels carrying some load. I would use a mandrel the size of the mounting bolt as previously suggested or drill a couple holes though web of wheels to bolt to faceplate also previously suggested.

  2. #12
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    wow 10 responses already, thank you all so much, let me try to respond to these suggestions:

    Quote Originally Posted by Lew Hartswick
    If youre cutting 4 Acres with 6" diameter wheels you need a bigger
    mower.
    ...Lew...
    what do you mean by this? this are the mower wheels, its a belly mounted 60" wide deck....short of a brush hog or similar 3 pt implement I can't go any bigger.

    Quote Originally Posted by scotplant
    could you not remove chuck jaws and turn them round and hold it with the stepped side??
    Tom..
    Could you clarify what you mean by the "stepped side"? when I pull the chuck, I have a 4 hole backer plate (with reg boss)....I do not own a faceplate at this time, but wouldn't mind an excuse to make one.


    Before I realized my chuck wont handle it, I had planed on making nice hardy arbor out of some 1-1.5 cr I have...make a nice threaded shoulder at the end and maybe a second for the tail end. I have used this method many times to do my "normal" work(~1-2" stock) The trouble I have is putting the center hole it without the lathe. Yes I have a drill press, put have never had much luck in accurately locating the center & if I miss then I am starting with an irregular cut at 6" and I worry about the machine handling that . My drill press probably needs a good tramming if I am to go in that direction.


    Quote Originally Posted by Carld
    I have a 13" lathe and turn 8" work as long as it's not to long.

    If your going to make wheels out of 6" stock are you going to band saw them to 2" disc's? If so just chuck one up as straight as possible and face one side, flip it face the other side and bore the hole for the bushing or bearings.

    I don't see a real problem doing the disc's. It's a mower and the OD concentricity is not that important.
    yes I plan on a band saw to slice them, but was thinking I would take the od down to true before than slice, but I still cant hold it for that first turning. My plan was similar to bore out bearing cups for ball bearings. and I know concentricity is not crucial, but I would like to do it well to expand my skill set.

    Quote Originally Posted by garagemark
    Here's a dumb question: Why true up the 6" CR in the first place? These are not high speed wheels. Why not just cut your 2" slices, center drill them and bolt em on? Unless you need to cut bearing pockets or something else, I can't see the need for perfect deck wheels. 2" Slabs will last forever, or until the center hole wears out. Then simply sleeve them again and again.

    Mark
    my father suggested this....I am putting bearings it the wheels (2per wheel) & making new axle bolts to mount them. This is overkill, but the old steel on steel bearing arrangement led to the shafts looking like irregular cams and the bores to be nearly 0.250 over sized....it took about 20 years, for this wear to occur but I don't want to do it again, ever.

    Quote Originally Posted by lakeside53
    I interpreted the OP question as a holding for a facing/boring operation.

    Surely the 16 inch lathe can handle the stock if the jaws are turned around. My 14 with and 8 inch chuck can do it in a heartbeat. I've used expanding mandrels where the faces and OD of 7 inch stock needed to be done in one setup.
    I thought so to, unfortunate its a 16" swing with a 5" chuck...would love to get a big 4 jaw in the future, just not in the budget right now. I cant reverse the jaws, but I have 2 sets, neither are big enough.

    Quote Originally Posted by Dieseldoctor
    I think what the OP is wanting, since these seem to be anti-scalp wheels for a mower deck, is to crown the outside diameter so they don't tear up the grass while turning with wheels carrying some load. I would use a mandrel the size of the mounting bolt as previously suggested or drill a couple holes though web of wheels to bolt to faceplate also previously suggested.
    this is correct, although I am planning to create a lip on either side to retain some rubber treads I'm making to give a little cushion to the wheels & keep the power coating on the entire chuck of steel....rust always worries me on agriculture equipment.

    Given the suggestions, I am inclined to go with the mandrel method as I intended, but starting that hole on the drill press...something I never do, because I have a lathe, could you all give me some advice on getting that center hole accurate? I know I can turn it true no matter where the hole is, but I'de like to keep as much material as possible. thanks again everyone!
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  3. #13
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    Its not the most accurate but for smaller round stock I use a center square (3" and under) but for the size you have, try using the center head of a combination square set

    http://www.mcmaster.com/#combination-squares/=gzaj3o

  4. #14
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    you can also use a live centre to press/clamp the disks against the jaws of your chuck to true them up, as long as you are not taking big cuts it works fine

    the more you expand the jaws out, the more leverage less slippage you will see
    --
    Tom C
    ... nice weather eh?

  5. #15
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    Lot of work for going and getting something off the shelf like this:

    http://www.harborfreight.com/7-inch-...eel-98951.html

  6. #16
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    Quote Originally Posted by Astronowanabe
    you can also use a live centre to press/clamp the disks against the jaws of your chuck to true them up, as long as you are not taking big cuts it works fine

    the more you expand the jaws out, the more leverage less slippage you will see
    Was going to suggest this same thing, you only need a center drill hole in the stock.

    Getting the punch mark for drill press in the center of stock is easy: Just measure the OD, halve it, lock your calipers to that number and scribe a line from couple of directions to get about a square in the middle of the stock. Then just punch mark the center of that tiny little square and it is good enough

  7. #17
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    If you're going to make bearing cups... you can't use a central mandrel I mean, that would work to true up the outside, but then what? You still can't chuck it. Seems the best way is that multi-bolt clearance hole idea.

    Spin up something that you can chuck and face yet allow a bolt radius bigger than your hub needs to be, maybe some clearance in the center for your boring. Drill and tap the bolt holes in it. Drill holes in your blanks larger than the bolts you intend to use so you can true it up on the above face-plate/mandrel thing if you're off in your drilling. Dial it in, tighten up the bolts. If you do well, you may not need to take anything off to true the outside.

    I'm far from an expert but that's what I'd do. Well, I'd just park a big whack of old wrecked cars on all that grass and be done with it... but that probably wouldn't work for you.

    David...
    Last edited by fixerdave; 04-06-2012 at 03:38 AM.

  8. #18
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    Actually yiou can use a central mandrel, if the stock lenght allows. I recently had to do aluminum timing belt pulleys, they only had a 10 mm through hole in the center and a small hub on one side. I chucked them first from the hub, drilled through, bored the center hole to about the required diameter and then bored the bearing recess.

    Once I had done this for all the pulleys, I chucked up some steel bar, turned a step that would fit snugly to the bearing recess in the pulley and also a small length that would fit the through bore. Then, drilled this deep, made a screw hole in the bottom of the hole and bored a 10 degree included angle in the front. On another lathe (or prior to turning this mandrel), I took a 12.9 SHCS that I turned to have that same angle in the head.

    Last thing to do was to slit the end of the mandrel in 4 places with a cutoff disc mounted in an angle grinder, cleaning the cuts and presto! Instant expanding mandrel! This way I could put the halfmade pulley on the mandrel, tighten the screw and bore the other bearing recess without dialing in anything and without marring any surfaces

  9. #19
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    I've machined a couple of 23" flywheels, for starter ring gears, in my 19" lathe.



    Method was to make a mandrel to fit the spindle internal taper, with a register to fit the flywheel bore. Then fit the flywheel to the mandrel with a drawbar through the headstock, and pressure from a revolving centre as a safety measure.



    No help if it's the bore you need to machine, but worked well for the outer edge.
    I tried a boring bar to begin with but the amount of metal that had to be removed would have taken ages, so welded a brazed tip turning tool to some heavy flat bar, which enabled me to take some decent cuts.

    The flywheel needed to be tight against the headstock to allow it to fit in the cutouts at the end of the bed. It's not a gap bed, but the bed isn't quite full height for the first few inches, presumable to allow room for chuck jaws etc.


    Tim
    Last edited by Timleech; 04-06-2012 at 04:30 AM.

  10. #20
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    So, the need is to turn bearing cups concentric with the outer? And this is an exercise in turning as well as a practical job?

    My suggestion, drill three holes at some convenient pitch circle and mount the blank to a face plate, put some scrap blocks in behind so that you can turn the diameter without fouling the face plate. True up the face of the work piece, drill the centre and bore one bearing cup. Flip the workpiece on the face plate and use a DTI on the diameter to centre it, bore the second bearing cup.

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