10EE tailsotck spindle taper
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  1. #1
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    Well, after using my lathe more and more I'm finding some of those little annoyances, and one has come to irritate me all too much. The MT2 taper in the tailstock quill is overground by about .010". No too much, but it makes some tools not fit at all and others require taking out the tang stop screws on the spindle for the taper to engage all the way in.

    The best solution I've found to date is to hard chrome the taper, then have it ground back to specification. There's an unfortunate lack of local outfits to do either, so I figured that if I had to send it out I'd check with those that might have had it done before.

    Monarch is sending me a quote for this, said that they hadn't done it for some time. I've priced out the plating and it was higher than I expected when they guessed at $150. The grinding is going to be expensive - expensive small wheel and excessive time on hard material. I've dropped email on a couple of outfits that appear to fix spindle tapers on the off chance that a MT2 tailstock quill wouldn't be too far from their regular job.

    Anyone got comments? Maybe a spare quill (it might be cheaper to fit a different quill than to try and fix the taper in the old one).

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    Hi Russ:
    I was planning to roll my own.
    I figure a chunk of 4140 prehardened bar machined to shape and then ground and lapped would just be the ticket...especially since I plan to dump the tailstock screw for a 0.100" pitch screw anyway.
    (I just hate those fractional pitches!!)
    This will let me line bore and hone the tailstock barrel after I get bronze pads under it. (it's badly worn)
    Cheers

    Marcus

    Oh yeah...while I'm at it, I just might go to MT#3

    [This message has been edited by implmex (edited 05-07-2003).]

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    I just may have to make one as well. I got the first repair quote back and it's about a third of the price I paid for the lathe. I'm waiting for a price from Monarch, but I don't expect to see anything different from them as I'm sure it'll be jobbed out.

    4140 sounds good, but I'd be tempted to make the whole quill overside then harden it and send it out for outside grinding - that's cheap enough that it wouldn't kill me. The taper I'd leave at MT2 as I've got lots of tooling to fit, I'm just not sure if that should be reamed to size or left oversize and ground after HT.

    Maybe I'll take this one apart and see just how hard it'd be to put one together. I can't see it being more than a couple hundred in materials and tooling to get one put together properly. Damn, but I hate making inside Acme screws, it's just a PITA, so that screw insert looks to be the most painful part.

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    I'm going to put my two cents in because I
    now have alittle experience with tailstocks.
    First, the bore of the tailstock housing HAS
    to be accurate to a tenth or better. Trust me, its got to be this accurate. The best way
    would be to have it jig ground and then lapped. We had ours ground by a very reputable
    outfit but did not QC it. Big mistake. Second, the chromer had a hell of a time fitting the quill to the bore. We thought
    he was not doing a good enough job. Well
    the problem was the grind job. I purchased
    a bore gauge and found the bore to be out
    about a .001, way way too much. We have
    since honed, and lapped the bore. And have
    gotten it down just under a tenth. Alot of
    $%^%$#@ Work!!!. We will take the now undersize quill back to the chromer again.
    Hopefully, this will work. This is a massive
    PITA!! You have been warned!!!

    PS that acme leadscrew is a real bastard size, bigsurprize ain't it. The bronze nut
    pulls out of the quill after you unscrew a
    slotted ring in the back. The hone and lap
    for the quill might be a problem, we used
    a Sunnen and a Boyer-Shultz. Not stuff you
    get at a yard sale. Cheers


    [This message has been edited by daryl bane (edited 05-07-2003).]

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    Ouch - both quotes for hard chroming the taper and regrinding to MT2 were in the $750 range. I'm going to take a stab at making one from precision ground stock, it looks like I can take some 1.250 stock and reduce it to fit the tailstock bore - wish me luck.

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    If you are going to cut it anyway, why start with precision ground?
    Bob

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    Bob, I ought to be able to hold the center for the taper and the nut with careful indication in the 6-jaw, and the current quill is 1.250 minus a couple of tenths so I suspect that the original size was 1.250 +- .0001. If there's any reduction it's not going to be turning, more likely a ring lap with very fine abrasive is all that'll be necessary.

    I picked up some O1 drill rod today, it doesn't appear to be lobed so I'll cut a chunk off, run a keyway in it and see how it fits in the bore.

    Measuring this one up the odd thing is the through hole - 37/64ths seems to be the closest if I assume that it was just drilling a bit oversize, and the hole is pretty clearly drilled. Everything else looks easy, I'll likely drill through for the taper with a 9/16, setup the taper and bore the MT2 close then clean it up with a reamer. After flipping it around I can come in from the other size with a 37/64ths, and bore .875 for the nut and bore and cut for the 1x16 locking dingus.

    If I had a


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    Russ, what condition is your tailstock bore in?
    Both Tim's and mine's bore were badly bell-
    mouthed before we started. And as I stated
    earlier, we had alot of work to fix a mediocre internal grinding job. We are now
    at a junction point as to the next phase.
    What is the proper way to fit a hard-chromed
    shaft into a cast-iron bore, with less
    than .0004 play? Tim's Harrison lathe has
    less than .0002. Any thoughts? I am going
    to shoot this question thru a couple of the
    boards and see what I get. I would think
    since you are making a new spindle from scratch, that a super precison fit to the bore would be important also.

  9. #9
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    Why not set up the 10EE as a boring mill
    and do the tailstock bore in place?

    Get a second tailstock or jury-rig a center
    that you can adjust until it is on the lathe
    axis, and lap the tailstock casting to
    fit. Presumably the tailstock ways are
    still in excellent condition close to the
    headstock.

    -Dave

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    One step I would take before using the
    tailstock ways up close would be to remove
    all the knicks in the ways. i.e. get out
    the scrapers straight edge and scrape off
    the high spots left from chuck dings, etc.

    -Dave

  11. #11
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    The first pass went well - I cut off a 9.5"+ piece of the O1 stock and cut a keyway in it, and after burr removal it fit into the tailstock. After feeling the fit of this I believe that the quill is pretty loose - this isn't the feel of a 'too tight' but the quill is definitely 'loose'. There's some slight bell mouthing but I don't think it's severe enough to bother about right now.

    I didn't have time for more than that. I believe that I'll drill and bore for the nut and keeper next - without the odd 37/64" drill I think I'll just use 19/32" (of which, strangely, I seem to have a dozen or so). That shouldn't take more than an afternoon, but I'm not sure that I've got a lot of time this week - it's getting busy again at work.

    Once the nut is in place I'll flip it around and drill & bore the taper, finishing with a reamer. I gave myself an extra .1" so I can screw it up one time.

    This might actually work.

    (Added later - crap. When I started indicating it in on the lathe I found the stock was lobed badly, so I'll have to find some replacement. The worst part was that I wanted to check when I brought it home, even mentioning it to the folks I bought it from, but I couldn't feel it with the V-mic {I couldn't measure as it's too large, but I thought I could at least feel it with some tension on the mic.} Anyone out there with a source for 4140 or 4142 TGP in less than a stick?)

    [This message has been edited by rke[pler (edited 05-12-2003).]

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    Continuing on my saga, I figured that I may as well run through the machining operations with the lobed drill rod while I wait for some 1144 to arrive. I've drilled and bored the outboard end, and have cut the inside keyway with the expedient of a 3/16" piece of M2 in a 90 deg boring bar run in & out using the carriage travel. It cuts much better on the outstroke than the instroke, but I've found that the spindle lock has too much slack and the keyway cut this way wanders a bit - anyone have any ideas on holding the spindle completely locked? I'm thinking a tapered wedge next to the locking pin, or just something to fill that space.

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    Dumore makes an indexing attachment that
    has an expansive collet that locks inside
    the spindle bore, then allows you to lock
    the spindle in place or index it as desired.

    I know that Al Sharon had several of these
    at one time, why don't you give him a call?

    Contact me offline if you need Al's contact
    info. I don't have it handy, and will need
    to dig it up.

    -Dave

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    Still moving on this, there were some complexities I'll outline since Marcus said he was going to make one of his own.

    The 1144 shafting arrived, on size and unlobed, and is a very nice fit in the tailstock bore after cutting the keyway. I drilled in from both ends after indicating and center drilling (the 37/64ths is the closest drill to the small end of the MT2), bored the .875 recess for the 1/2-8 acme nut and keeper, cut the inside keyway (some fun there) and threaded the keeper recess 1x16tpi.

    For the MT2 I put up an MT2 tool between centers and setup the taper, expecting only a rough taper in the setup, but it was pretty dang close on my test piece of O-1. I put in the 1144 and cut the MT2 taper inside.

    Right now I'm working on the outboard end of things - getting the tang stop pins (a bit of a complexity there as the holes for these in the quill are not through tapped, and the wedge slot is a 17/64). I stopped to make a couple of new stop pins, they're ready for heat treat this afternoon.

    I should finish up the new quill this week if I don't get tapped for some travel tomorrow, then it's off to make a tap for the 1/2-8 acme to make a new nut. Gonna be real fun to make that w/o a follow rest - I may have to use my old lathe, but I don't have a lot of faith in its leadscrew.

    Opps - forgot to add that I replaced the key in the front of the tailstock that the quill runs on - interesting setup. the key is apparently a 3/16" by 5/32", and has a 3/16" pin to keep it from moving fore and aft in the keyway. Even the old quill feels a lot better with the new key - no rotational slop at all. I also put a shim in the back of the tailstock to get the witness mark back to the top - for some reason it was towards the back of the lathe but a .005" shim moved it back to the top.

    [This message has been edited by rke[pler (edited 06-01-2003).]

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    Why not resize the 2 up to a 3 morse?

  16. #16
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    Phil asks "why not MT3"? Well, there's not a lot of meat in the quill for that - you need a 25/32 through hole and 3/4" more depth, and even after that the major diameter is close to an inch, so that outboard inch or so of taper won't have too much support.

    Even with that I might just make one from one of the spare pieces of stock. It'll be that little bit short but would still be able to hold a drill. Likely I'd forgo the holes for the removal wedge and just make it with stop pins for the taper tang, depending on the quill screw for removal.


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