Headstock Alignment Colchester ?
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  1. #1
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    Default Headstock Alignment Colchester ?

    Guys I have a 70's 13" Colchester lathe that I believe is out of alignment.I was boring a 1" hole for some bushings in about 5" tubing.The end out of the chuck the bushing fit perfect with using the press just to apply even pressure.I went to install other bushing that was on the inside of the chuck the bushing slide in with just finger pressure.There is couple of adjustment screws that is on back side of the headstock to aid in alignment.What I did was put piece of bar stock in the chuck about 10" then put the dial indicator on end closest to tailstock to see how much I move it while adjusting.So before I start how can I check to see how much its out so that I have an ideal on what to look for?Guys the headstock seats on v-ways so I don't see how its going to move.If you know of a procedure please let me know or if possible please explain how.Thanks guys

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    Generally ,you will need to loosen the head to bed securing screws,before the head alignment can be adjusted.........does it have two horizontal set screws......they can be used to move the head over...........If you need to remove the motor to get at the head screws,it can be a pita,and you want to get it right first time..........Ive found the easiest way is to get a length of 2" app dia brass,and do test cuts on that......doesnt take any cutting force ,and cuts very cleanly.....just remember ,you only need to move the head half the diameter difference......BUT...before you do anything make sure the tapered cut isnt the saddle twisting on the ways,or caused by worn ways just under the chuck........a simple way to check this,is to bore a bore,then reverse the saddle ,without touching anything......does the tool take another cut,or just run out with maybe a bit of fuzz.........if it takes another cut,the saddle is twisting.

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    according to this it doesn't sit on the v way- it has a v cut in the head but is only for clearance, actually sits on the flats and has a dowel and adjusters to pivot it.

    Read carefully before you do anything-
    http://vintagemachinery.org/pubs/181/17225.pdf

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    As John said your bed might be twisted. Make sure the lathe is leveled with a Machinist precision level, don't use a Carpenters level! Another thing to check is the chuck! If it don't hold the work straight you'll bore a taper. Your taper is not much about a thousandth or 2 in 5".

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    I should have said ....the saddle can rotate on the ways......this will have a most pronounced effect on a boring bar sticking well out......Twist is a poor choice of words,but thats what it is.......consequently,when making a short cut ,be sure this rotation has been worked out ,or the saddle will turn on the bed ,affecting the dimension of cut.............this rotation is quite noticeable on worn lathes ,and can be a difference of 010 in a return cut........this is why some turners say to never cut in both directions when boring......

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    Unless the lathe has been knocked over, it's highly unlikely the headstock is out of adjustment. Was your tubing 1 inch bore diameter by 5 inch long? I'm having trouble visualizing the setup. Colchester lathe manuals show the technique for machining two rings to adjust the lathe bed to eliminate twist, I use a 2" diameter bar with a couple of 3" rings of aluminium loctited to the 2" bar to get a reasonably rigid test bar to machine with light skimming cuts and a sharp tool to minimise cutting force. You have to have three of the lathe feet bolted to the concrete slab and the fourth foot on the rear of the headstock has a jacking bolt to eliminate any bed twist.

    I have a 1967 11"? Bantam and had less than 30% contact between the ways and the worn saddle casting as well as the compound slide base rocking on the cross slide due to wear. Once that was sorted out it was a completely different lathe performance wise.

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    Fantastic guys this will be big help,while looking at back of HS seeing’s it seat on bed there is clearance I be dang.Na the lathe was broke down for transporting the HS was removed.So going to break out my new precision level start from there.Never gave the saddle a thought.Starting over👍

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    A very quick test for checking HS alignment that mostly eliminates effects of bed twist and wear is to take a facing cut on a large diameter disk, say 6" dia. x 3/4" or so. After your facing cut put an indicator on the cross slide and traverse across the cut. On the front half it should read zero since you just cut there. On the back half it'll read twice the error of your head stock alignment, convex or concave. (I usually ignore the middle inch or so because low surface speed can have an effect on finish/cut). You then simply adjust your HS to split the error, i.e. both front and back readings are the same.

    Some will argue that cross slide perpendicularity to the ways is will impact this as well, but the tolerance of this on any decent lathe is very tight, usually something like 0.0005" over the entire swing of the lathe, concave only. If yours is out considerably more, you've got bigger issues than HS alignment. As such, for lathes with a moveable HS, the facing cut is a very quick way to get the alignment very close before moving to two collar tests.

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    You got good fit at one end but the end that was in the chuck is loose...you are probably compressing the tubing in the chuck!!!!

    Probably better off to do it in two chuckings.

    as mentioned a better explanation or a pic will help.

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    The reason people sell test bars is so you can avoid all this faffing around but hey ho we are where we are.

    When I aligned head stocks I released the screws at the back of the headstock and one of the screws at the front. I left the other one at the front just less than really tight but tight enough to pivot off. Look out for any dowels locating the headstock to the bed.

    Using the " push me pull you " at the back of the headstock between the ways you can throw the head into alignment. I always put a DTI on top of the feed box touching the headstock casting near the " push me pull you " adjusting block. That way you know your starting point and you can see how far you've moved the headstock.

    Regards Tyrone.

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    When you ve done a few ,you get a idea of how much to move the head,but ,moving it a thou at a time will take a month of sundays if you have to part reassemble the machine between tests............and I am very suspicious of arbors ,and if you use one,be sure to rotate it 180 deg for two readings at each setting......dont trust the thing .......and remember ,you can easily spring an arbor several thou with just fingertip pressure,or heat

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    Default HS

    Guys I think I can call this good with ya'll vote.After couple afternoons adjusting and getting closer and feeling good I told myself just one more time.Yep you guess it,I over shot it.The big end is now at the chuck,but after another 3 times I got closer and closer then I told myself"No this is good enough" so I am within .002 Guys I have made several test cuts,its better than what it was leaving well enough along. I hope this is good enough for a guys who just plays around but want a good fit.My fingers hurt,back hurts,etc.so bar getting smaller.Anyway here few pics of the part I made then bored it out for bushings.Looking at my welding you can see why I have Can'tWeld as my login.Going to take die grinder clean up weld.Any suggestions please let me know,going to start on my tailstock now to get it lined up.
    Attached Thumbnails Attached Thumbnails bar.jpg   part4.jpg   part3.jpg   part2.jpg   part1.jpg  


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    Your bar is too skinny For that much sticking out...4-5x

    and if that is an interrupted cut at the end it isn't helping either.

  17. #14
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    Dang I knew something had to be wrong it was going so good.I do have some 2" but its only about 10" so time its in chuck maybe 8" be sticking out.That's 1" shaft but the keyway is only bout 1"

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    2" with 8" stick out is about perfect.

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    Quote Originally Posted by iwananew10K View Post
    2" with 8" stick out is about perfect.
    +1.

    Your long skinny bar is going to move all over on you and as you know have you chasing your tail. As mentioned 4 to 5x diameter is about max for just regular turning without tailstock support, let alone a test cut for HS alignment or bed twist.

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    Just tell me you de-burred those drilled holes before you fitted the bracket ? That and a nice 1/8" X 45 degree chamfer all around that bracket is the difference between an amateurish job and a pro job.

    Regards Tyrone.

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    I tend to buy all my holes pre-blurred.


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    Quote Originally Posted by jim rozen View Post
    I tend to buy all my holes pre-blurred.

    Thanks for that Jim, that Stella Artois must be stronger than I though. You know what I mean but I better correct the typo just in case.

    Regards Tyrone.


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