Heavy 10 is cutting a drastic amount of unwanted taper - long post with pics
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    Default Heavy 10 is cutting a drastic amount of unwanted taper - long post with pics

    Hey, guys. I'm going to walk y'all though what is going on to see if anyone can help with this lathe. Bear with me, it isn't short, but I'm systematically eliminating common things in all the research I've done. Trust me, I've researched, I've tested, I'm stumped. I'm not chasing tenths or worried about minor tool or workpiece deflection, I'm trying to find out what is BIGGLY wrong. Also, for the sake of pictures I've used a set of calipers to show the readings instead of a mic.

    This lathe came up on eBay back in late Oct or early Nov, I don't remember. It was only about 4 hours away, the pics looked good, the price wasn't bad so I bought it. At pickup there was no 3-phase to test anything and I knew that going in. No big deal. When I got it home it was pretty crusty so I tore it down to about every single nut and bolt for a good cleaning, inspection, new wicks, etc. This is somewhere around a '57 so it has a little wear as expected, but generally in very nice condition, and certainly capable of cutting decent parts, right?

    Everything was done correctly to the best of my knowledge. I've done this before and I'm familiar with shims, bearing clearance, bed "leveling"/twist, etc. Right off the bat it was cutting a taper. Please note that up until the very end of this whole post there is not even a tailstock on the lathe. All of this has to do with chucked up work pieces. On about a 4" piece I was getting .016" taper. The part was larger at the chuck and decreasing in diameter as it headed toward the tail end of the lathe. I shimmed up what should have been the offending leg with no measurable change. It was shimmed once to the point of having a leg complete off the ground without any noticable change in taper. Next, a whole list of common things were done to try to rule out the problem but nothing changed.

    - changed cutting tools, no difference
    - changed tool holders (all Aloris), no change
    - changed tool posts (all Aloris), still no change
    - ran tests in a 3-jaw
    - ran tests in a 4-jaw
    - ran tests in a 5c collet
    - made cuts with and without the taper attachment binding lever tight (taper attachment clamp is not on the lathe, just in case anyone was wondering.)
    - used a different saddle, no change

    Everything was still the same. Once upon a time I had a cabinet style heavy 10 that developed a taper in it after it was moved with a forklift under the bed. Chad recommended relaxing the bolts that held the lathe to the cabinet and it fixed it. So I relaxed all the bolts, let it settle, tightened everything back up. Nothing. I removed the chip pan. Nothing. I removed the headstock and checked for chips, burrs, squirrels, and replaced it. Nothing. Still cutting the same freaking taper.

    Finally I got another headstock, spindle, bearings, everything and did a complete headstock swap with correct bearing shimming, just knowing that would somehow take care of my problems. Nope. Still cutting the EXACT SAME TAPER.

    So here we are with a few pics. The offending lathe in question with the 2nd headstock assembly on. I was trying to measure across the face of that plate but I don't think the plate is consistent enough to test.





    The following are just a few pictures of the ways and the under side of the saddle to give you a general idea of the condition of the lathe. Certainly not anything that would drag and cause such a taper.







    I started over at this point and began taking some pictures. Here's the bed twist from one end to the other. Not "level", but I understand that level doesn't matter, but there is no twist. (A leg has been shimmed .035" to achieve this)

    Heastock end, note the bubble position.



    Tailstock end as far as the carriage will travel. Same bubble position, so we have an untwisted bed to work with.




    First test cut after "leveling". You can actually see the taper. This is in a 3-jaw.



    Up near the chuck it is .841"



    Near the end it is .817"



    Next we chuck up a two collar test bar in the 4-jaw and make an equal pass across both collars.

    The collar closest to the chuck is 1.870"



    The 2nd collar measures at 1.830"



    At this point I just know all the guys on Practical Machinist are going to blame the swapped over headstock assembly, so I switch it back over. While I have it off, I snap some pictures of the bed ways underneath and also the v-ways underneath the original headstock that's going back on.








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    So now I have the original headstock back on.


    I built it back up with another spindle assembly, correctly shimmed the bearings, repeat all the tests and the taper is EXACTLY THE SAME as it was originally, with the 2nd headstock, and now back with the original.

    I didn't bother taking any more pictures of tests because they are exactly the same as I posted up above, just the diameters are slightly smaller from the work pieces being cut multiple times.

    Now, just take this last section with a grain of salt. This is the only time a tailstock is used thus far. We all understand the inherent fault with this but they're worth noting when stacked with everything else.

    All I can go by is the marks on the back, but I lines up the tailstock as perfectly as I can visually.



    Now looking straight down at two centers.



    Zero'd at the headstock end.



    It goes negative as we travel towards the tailstock. That's not a precision test bar but it isn't tapered and only has a couple thousands of runout.



    So where exactly do I go from here? Please use small words and short sentences because obviously I'm not as bright as I once thought. I can't do anything with it tonight, but later this week I can do further tests and report back.

    Thanks.

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    Headstock is crooked -- it is pointing "out" instead of straight down the ways.

    Take it off, clean the mating surfaces, make sure there's no chips or dents, put it back on, try again.

    Regards.

    Mike

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    normally put test bar in headstock only and indicator on carriage and indicate test bar tram. this assuming lathe ways are level and not severely twisted. which if level on carriage as it travels ideally level should not change much
    .
    if it shows headstock is not parallel to carriage travel you can try adjusting headstock although why or reason to need to do this is curious
    .
    other is if cross slide not tight enough vibration can allow it to shift while cutting. usually i adjust gibs for slight resistance

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    kind is wish the other head was still on so you could run it.

    I would have much preferred the level across the tops of the v ways at the extremes of each end and then do your collar test....riding on the saddle its picking up saddle drop and it looks like you do have a fair amount of it...the level bubble really shouldn't stay the same going from worn area to unworn area.

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    Quote Originally Posted by hsracer201 View Post
    ...

    Now looking straight down at two centers.



    ...
    With that much misalignment it is going to cut a taper.

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    i would test headstock alone first with a test bar, tailstock is adjustable and can be anywhere.
    .
    headstock normally should with indicator on carriage indicate testbar in heastock within .0005" per 10" ideally which is .001" diameter difference per 10"
    .
    this assumes the lathe ways are level or not twisted

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    i am going to step out, and would encourage all but a couple posters to do so too, or this will become 5 pgs. of guessing.

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    Quote Originally Posted by iwananew10K View Post
    i am going to step out, and would encourage all but a couple posters to do so too, or this will become 5 pgs. of guessing.
    I appreciate your input, and was hoping to get it. It just kills me when people cannot read, but then post anyways. (not you)

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    Quote Originally Posted by Finegrain View Post
    Headstock is crooked -- it is pointing "out" instead of straight down the ways.

    Take it off, clean the mating surfaces, make sure there's no chips or dents, put it back on, try again.

    Regards.

    Mike
    I covered that I had done all of that.

    Next.

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    Quote Originally Posted by DMF_TomB View Post
    normally put test bar in headstock only and indicator on carriage and indicate test bar tram. this assuming lathe ways are level and not severely twisted. which if level on carriage as it travels ideally level should not change much
    .
    if it shows headstock is not parallel to carriage travel you can try adjusting headstock although why or reason to need to do this is curious
    .
    other is if cross slide not tight enough vibration can allow it to shift while cutting. usually i adjust gibs for slight resistance
    But it can't shift if the taper attachment binding lever is tight, right? Either way, cross slide gib is tight.

    Thank you.

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    Quote Originally Posted by iwananew10K View Post
    kind is wish the other head was still on so you could run it.

    I would have much preferred the level across the tops of the v ways at the extremes of each end and then do your collar test....riding on the saddle its picking up saddle drop and it looks like you do have a fair amount of it...the level bubble really shouldn't stay the same going from worn area to unworn area.
    It is up and running, and I can test just about anything, just need the guidance.

    I can put the level directly on the ways at each end and post pics.

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    Quote Originally Posted by hsracer201 View Post
    But it can't shift if the taper attachment binding lever is tight, right? Either way, cross slide gib is tight.

    Thank you.
    you grab tool post with touching indicator and magnetic base on lathe ways and try to move back and forth with your hand. it should not move easily back and forth seen with indicator. if it does move sometimes the gib needs adjustment,
    .
    some tapered gibs need a shim or a new tapered gib installed if adjusted all the way and it still is not tight. some gibs have adjustment screw on each end if you push one end of tapered gib you need to loosen the opposite side adjustment screw to allow it to move. also sometimes a screw is bottom out feels tight but its not tight just screw at bottom of its hole

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    [QUOTE=hsracer201;3299289]It is up and running, and I can test just about anything, just need the guidance.

    Guidance:

    1) to outboard collar has way too much chatter there. Sharper tool, slower feed, slower spindle speed.
    Or a larger diameter test piece, or a shorter test piece.

    2) the right hand legs on this machine appear to be basically floating on the concrete floor. If you push on
    the machine does it rock on the legs? If so you will *NEVER* get it to turn or bore straight. If there are
    shims under there have you tried adjusting them?

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    Quote Originally Posted by hsracer201 View Post
    But it can't shift if the taper attachment binding lever is tight, right? Either way, cross slide gib is tight.
    You only tighten the binding lever (over the taper attachment) when you want to cut a taper. If you really DO have this binding lever tight, this may be what is causing your taper. When you are NOT using the taper attachment, loosen the tie rod bracket of the taper attachment. When NOT cutting a taper, the TA should move WITH the carriage.

    My other idea is maybe one of the alignment pins for the headstock is too high and not letting the HS properly seat, thus riding high. Put some Dykem marking fluid on the ways in the headstock area and see if you get 100% contact.

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    Quote Originally Posted by SLK001 View Post
    My other idea is maybe one of the alignment pins for the headstock is too high and not letting the HS properly seat, thus riding high. Put some Dykem marking fluid on the ways in the headstock area and see if you get 100% contact.
    I agree, it looks as though the problem is in fact misalignment of the head stock. Because both head stocks gave the same results, I'm thinking the problem is with the mating surfaces of the bed, rather than with the head stock(s) themselves. It may be like SLK001 suspects and one of the pins is to high, or otherwise out of whack and keeping the head stock from sitting flat and true on the mating bed ways.
    You can set the head stock on the bed(not clamped down) and check it's fit with either bluing as suggested above and/or with feeler gages where possible.
    Maybe remove the pins and actually get a rub with bluing to check contact.
    I would probably first turn a test bar like the one I suggested in the other thread, with two collars of exactly the same diameter, and leave it in the chuck. Then, once the machine apart, you can trial fit things together and get check alignment with an indicator mounted on the carriage.

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    Many good suggestions on troubleshooting above, and lots of speculation too.

    Since you have had the H/S off and a second one on and still have the same problem , rules out a bad H/S.

    No guessing here, just a procedure using your level, indicator and feeler gauges or gauge blocks to find the root cause(s) of the problem

    Good troubleshooting is verifying assumptions.

    First you are not using your level correctly.

    The small vial on the end NEEDS to be in the center. Now you can use the large vial to measure, BUT only with the bubble spanning the center gap. So you should move to on the ways as mentioned, using shim(s) under the legs to get the small bubble centered (somewhere level lathe bed end to end). And shims under the low side when checking across the ways to get the large vial somewhere centered. Check by HS and again by T/S end keeping the same shim stack for both positions. Do not switch ends of the level (small vial is always on the same end). You can measure the twist by either measuring with the bubble, or by adjusting the shim stack to get the same bubble reading and noting the change, I prefer this method since the change may exceed the ability to measure with the bubble. Shim the legs as needed to get the twist out to within .001" from end to end. Now that the twist is out move the level to the T/S flat way and check both ends and middle for level, shim the level as needed . If there is tilt that is not consistent along the length of the bed, may be sway back or hump back bed. This may be part of the problem. All feet MUST be on the floor with some weight on them, it may take a day or two to for the bed to unwind from being held in a distorted position, to get the twist out.

    Do a test cut, do you still have the taper?

    If things do not check out, take the headstock off and recheck for bed twist, still the same as before taking the H/S off? If not, there are issues with HS to bed fit distorting things. Continue on to find out.

    If nothing is noticed from the above, set the headstock on the T/S end of the bed. Position an indicator to check for rock of H/S as each corner is pressed down. Any rock found? Should be none.

    Now insure that the pin in the flat way to locate the H/S cannot bottom out in the hole in the H/S. And that is a loose fit in the hole.

    If all OK, pull the pin and the clamping bolts from bed.
    Set H/S in the proper position and check for rock with an indicator as was done on the other end of the bed.

    Somewhere in the above you may find something amiss.

    If not the H/S may be tilted, to check, mount a straight test bar 3/4" or larger 6-8" long in a collet. Tap the far end around till it runs true when turning the spindle by hand. Now check the top of the bar while cranking saddle back and forth. Move indicator point to the flat T/S way and crank back and forth. The readings should be very similar, since there is bed wear.

    The above tests should reveal one or several things that are contributing to the taper. And it may be a bed that has warped over time, or from crashes. I have seen bad bed warp (swayback and twist, got the twist out but the swayback was the killer) on a fairly new Pacific rim lathe.

    Hope this helps,
    Bill

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    If the bolts holding the headstock were slightly bent, could they pull the headstock off center? (doesn't really seem possible with it sitting on the ways though...)Jim

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    Amen Bill! As soon as I saw that level bubble in no-man's land I thought 'You must be joking!'

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    As I mentioned before, I donít have much time tonight and itís 12 degrees in my shop.

    As for the single alignment pin I thought about that and did test cuts without it in place at all and got the same results.

    I also swapped headstock bolts in case they were bent.

    Iíll mess with it tomorrow night.

    Thanks for the replies and PMís. Iíll report back as soon as possible.


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