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Hi all!
I'm in trouble and ask for help, any advice welcome :rolleyes:
I have an old lathe, the tailstock position is not correct and the centre is off axis.
There are some marks on the back of tailstock, the "0" seems out of phase, more 2 scratch to the side, maybe have been done later by hand.
Currently I got no double fixed point, no rectified bar, there is some way or tips for finding the correct alignement?
I take some picture
Thanks
Stefano
Make a set of alignment buttons, e.g...
http://www.homemadetools.net/forum/t...-buttons-49099
In my construction notes in that article I indicate that the holes should be center-drilled. If your tailstock is badly out of alignment, then that operation may be problematic. A more accurate process would go like this...
Rough drill hole using tailstock
Bore hole to ensure its centered and cylindrical
Form 60 degree bevel on mouth of hole using compound rest
Once you've carefully made the buttons, save them. You'll need them to reset the tailstock the next time you set it over to turn a taper. [Although there are better ways than tailstock setover but that's not related to your problem.]
Hey Stefano, Just chuck up something, center drill and use tailstock dead center or live center to piece as long as you can and turn between it and chuck and indicate you will see how it is off, than adjust tail stock accordingly. God Bless Ya Dave:)Quote:
Originally Posted by rendoman
The button method. This is one of the easiest ways to do it. Once the buttons are made, put the small end of one in a collet or 4 jaw chuck, make sure it's running true. Put the other one on a center in the tailstock and bring the 2 big ends together. Measure across them horizontally with a mike as you adjust the tailstock side to side. When the reading across both buttons is the nominal diameter of the button, the tailstock is centered.
There are pretty easy adjustments for horizontal adjustment, but not vertical so hopefully that part is ok. If not, going up will definitely be easier than going down with the help of good shimstock.The fastest way I found to check alignment was to chuck a coaxial dial indicator up in my 3 jaw (assuming that the chuck is centered) and I put a piece of machined round stock in the tailstock chuck. Then its just a matter of moving the tailstock in and out to check for being true with the bed ways, and spinning the coax indicator around the round stock to get the tailstock centered with the spindle, making necessary adjustments to dial it in. Hope that helps.
You need a dial indicator with a magnetic base or some other appropriate way to mount it. Just chuck "something" a rod or round bar in the Head-stock that is the right size for your lathe. The smother or rounder it is determines the accuracy of your alignment. Bring the tail stock up to the head-stock close enough to reach across with your Dial Indicator mounted or clamped on the rotating part of the tail-stock. Now you can spin the tail-stock so the indicator touches the outer diameter of your chucked up "something". As you spin the tail-stock slowly the indicator will show you the relative difference between the rotational axis of head and tail-stock. Adjust your tail-stock mounting ever so slightly and spin it again noting if the difference is more or less. Now you know which way to move the tail-stock mounting to bring the difference to near zero. This dance must be repeated on another location on your "something" by moving the tail-stock backward or forward to a new location. All of this is relative to the size of your lathe. The bigger the "something" is the better you will see the miss alignment. This is a really shotgun approach but I assume you have some skills or tools. Moving the dial indicator mounting to the lathe way bars that go under the tail-stock you can touch the indicator to the diameter of your "something" spin the head-stock to see if your "something" on the same centerline as the head-stock. Moving around the lathe just spin or stroke all of your slides and spindles. using the dial indicator to show the difference as they move. Trial and error will teach you what to move to bring everything to "dead nuts" zero. Like I said this is relative to the size and quality of your "something" (aka Cylinder Square) and the condition of the lathe and the tools you have to measure with. If you have access to a Machinist, tool maker he can asses your situation and give way more specific instruction. From Microns and Angstroms to feet and inches the process is still the same. Whether you have a Dial indicator or a Laser , spin, sweep, stroke or tram, it's what you have and what you make of it. Hope it helpsQuote:
Originally Posted by rendoman
Thank you all very much!
I will try soon all the advice received
I post a couple of pictures only to show old lathe
Attachment 17814 Attachment 17815
Attachment 17816 Attachment 17817
Many good points have been made here. Here is my 2 cents:
Many years ago, my mentor taught me to turn a rod between centers, using a lathe dog (lathe dogs are cheap; every machinist should have several of different sizes.) This eliminated any error in my 3-jaw chuck. Also, by turning the rod end-to-end, I eliminated any error in the rod itself. Once I had turned the rod, I measured it for taper, using a good (calibrated) micrometer. After adjusting the tail stock accordingly, it was rinse & repeat, using the same rod. Eventually, the rod miked out equal in diameter along its entire length. Thus, the tail stock was aligned with the spindle's center & it was good to go.
This procedure can be a bit tedious, but it works. It eliminates errors that may be introduced by the chuck* and by the rod itself.
Good luck, and happy machining!
*run out error in a chuck is another matter, but it too can be fairly easily adjusted to run true to the spindle.
Precision alignment is usually done with an axle bearing two rings, one at each end. Run between centers to avoid chuck errors, etc., a cut is made on each ring and their resultant diameters compared. This is very similar to what you suggest.Quote:
Originally Posted by Caldude53
Nevertheless, it is tedious. Having a set of alignment buttons to get you close will minimize the time spent with precision alignment and, depending on what the work is, may themselves provide sufficient alignment.
Hi; there is another method , that you can use without turning buttons or machining anything, just put a magnetic stand with a "finger" type indicator in the face of the chuck, make sure that the indicator finger is touching either in the inside hole of the tailstock or the outside diameter of the tailstock quill.Now, rotate the chuch BY HAND, slowly and you will see how much the tailstock is out, just adjust until you have same reading in the indicator across both sides of the tailstock.Quote:
Originally Posted by mklotz
Please allow me to say this... MERV KLOTZ you are a GENIUS!
Mariano
Sorry I just realise that Robertisheets has already posted something similar..
Mariano
Mariano,Quote:
Originally Posted by rasta
Much as I appreciate the compliment, undeserved though it may be, my name is still Marv, not Merv.
1st you need a test bar which is a round bar 6-12 in. long with centers on both ends hardened and the od is ground to a tolerance of +or- .0005 or better .0001. you can make 1 if you have access to a full shop or you can buy 1 from Travers Tool or McMaster Carr. if your head bearings are tight and the ways are not beat up. take a stone to smooth out nicks and dents on the ways and the bottom of the tail stock put the bar between centers put a dial on both ends and there are adjustments on the tail per the manufacturers instructions that you can download from them. you can find this on youtube look up "using lathe test bar" that should get you started. that's the best I can help you unless you live in wi. usa Jimbo
Try reading any of the myriad of "How to run a lathe" manuals.
1st things 1st
I've owned several old lathes, most have had hard lives long before I got hold of them. What I usually do is to start off with checking to see if the head stock is anywhere near in alignment. first the spindle bearings would need to be adjusted if they are the type that can be adjusted if old poured Babbitt bearings shims may have to be taken out and the bearing scraped to round or re bored using an external boring bar attachment which would have to be mounted to the ways and centered from both ends. It is usually preferable to strip the ways of the head stock the carriage and the tail stock and get the ways trued first but this process of completely refurbishing is neither quick nor for the faint at heart.
assuming the spindle on your lathe is already running close to true, and you have decent ways,and the chuck is is good condition. You can chuck up a piece of stock and simply turn it to a point 60° would be a nice number since many dead centers are of that angle then use the buttons that Marv described or use the test bar mentioned above. I like the idea of the button method with this note. with buttons and dead points in place check the tail stock with the quill fully retracted then with it fully extended if both reading are the same your job is done, Another variation to this would be to chuck a piece of stock preferably a piece that is ground and polished leave sufficient amount protruding from the chuck in order to turn the same MT size as your tail stock has then part it off with enough of the cylinder surface remaining on the part you just made. insert that into the tail stock then perform the same measuring technique as with the buttons.
If you are not comfortable in making your own tapers then bars can be purchased that already have the taper machined on them,You would simply part it off like I mentioned.
You should also make sure the lathe is level which would be checked most accurately with a machinst level across the ways near the headstock and also tailstock. You could get the tailstock in alignment with the headstock as has been mentioned before but then if you center drill something and then extend the stock out quite a ways, such as almost lathe capacity and turn until cleaned up and check for taper. If you do not have access to a precision level and there is taper, you at least need a good dial indicator. Set the indicator on the same plane as the cutting tool and adjust leveling screws which should be sitting on metal pads with a countersunk hole for the screw. When adjusting, only move a thousandth or two at a time and let settle for a day or so before making any more adjustments for level. Take another cut and see what changed. If you like the change, keep moving in the same direction. When setting up indicator you need to have slight pressure on the needle, you can often push or pull on tailstock and see slight movement of needle depending on how robust your lathe is. Good luck.
Thank you guys! you are really fantastic!
I'd offer reinforcement to utilizing buttons as a starting point.
However, with a decent length bed, buttons won't reflect error that surface on a longer part. Due to imperfection of wear and out-of-plane ways, and leveling of the machine itself. That's where a dog driven proof rod on centers will. "Out-of-plane" has to be corrected both along and across the ways. Straight and round turning will not occur over bed with twist.
Marv is correct, single point boring centerdrill recess and turning an outside diameter of short length [each end] will be concentric to greatest degree possible. Chuck runout is then reduced or not an issue. I'd be tempted to mark bar's relation to chuck #1 jaw, and that both ends coincide.
Then make a wooden box to store it in; ideally supported 1/3 [one third] from each end. If you suspect the bar sags in use, that is corrected by a rest; either steady or follow variety. Then you'll get good results setting up in the position you intend to work.
AND, test bar isn't restricted to occupying the chucked end and center. Set the bar chucked and steady rest accurately, then pull chucked portion into steady and free end to center point elsewhere along bed for indicating.
Hi everybody,
As I not always understand all explained, my english is sometimes not sufficient, it's just something to remember, it can take a lot of time for controlling all parts, as you can have an error in the centering of the cone which can be controlled with a well centered MC… with a 100mm. part, a second error can be with an out of round tailstock etc., you can have at least 8 or 10 possibilities of an error, controlling all parts is a big time consumer.
With a lathe as the Schaublin with a trapezoidal centering, there are less possibilities, but what occurs often on second hand lathe is you have parts with a difference in numbers of mounting, and it's a headache to solve such errors, the system with the two reference diameters give only a solution for a given position, and not for example when using a collet system.
For me the alignment of a revised lathe is the more time consuming operation to make and you do never be irritated when it doesn't be right at the first proof.:cool:
Hi Rendoman,
Do you have a pair of centers? One for the head stock and one for the tailstock? If you have place a six inch,(150mm), rule between the two with a light pressure. Looking at the rule and how it lies will tell you if alignment is out and in what plane.
Rough set/align and then chuck up a bit of scrap. Center drill the end and turn the outside round for about an inch. Part-off a bit about 1/2" long. file/stone off any pip. place parted off piece back in place where it came from and bring up center in tailstock to hold firm.
Rotate chuck while holding parted off piece staytionary with thumb and forefinger. You will be able to feel any mis-alignment very easily between the two faces,(radial displacement).
Short of having test bars and quality D.T.I.'s this is the easiest method I know. Note most tailstaocks are not true in the verticle plane from the factory.
There is a fairly easy way to align the tailstock , Chuck up a piece of metal larger then the diameter then the tailstock spindle. Turn the stock to the same size as the tailstock . Press tailstock spindle up to the turned metal , using a dial indicator zero out on turned part move carriage to spindle adjust the tailstock to zero and it should be good , top to bottom if out you will need to shim the tailstock.Quote:
Originally Posted by NortonDommi
Works about the best of all ways to realign.
As Stilldoinit and Toolmaker posted, LEVEL the lathe first. This is critical. It don't matter how much cast iron is there, the ways will be twisted if not level. If it sat in a twisted state for many years, you may have to give it time to resettle, and keep checking the level until you have it zeroed out. What is the floor it's sitting on, if not poured concrete, you will have problems. Then you can proceed with making sure the lathe spindle is parallel to the ways, then the tailstock quill is aligned with the spindle.
Lots of good techniques here.
