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Tailstock Setover Adjustment (was Alignment)
- Thread starter cdhknives
- Start date
- Joined
- Nov 16, 2012
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- 5,596
Re: Alignment
You're 3 thou off end-to-end which is pretty good... There's a little problem though... You're holding with a jawed chuck and supporting with the TS. Under normal circumstances, you'd want to move your TS 1.5 thou away from you. The problem is, the shaft is being held firmly by the jaws. You could try to loosen the jaws a bit to allow the shaft to move a little but, I can all but guarantee, you're going to chase your tail as things will settle into different positions each time. If you don't loosen the jaws and try to strong-arm the TS over by 1.5 thou, a thin bar like that will bend (ever so slightly) as it rotates and you'll end-up with an inverted barrel profile. As is, what you're kinda doing, is a TS alignment test. To do that "by the book" you should spin between centers.
To do the 2-collar test (which is what I think you're after), you'll want to use a piece of stock at least 1-2" diameter -preferrably aluminum -and you'll want to relieve the center. Also, don't support the end in the TS. Take an extremely light cut as not to put a lot of force on the shaft.
Make sense?
Ray
You're 3 thou off end-to-end which is pretty good... There's a little problem though... You're holding with a jawed chuck and supporting with the TS. Under normal circumstances, you'd want to move your TS 1.5 thou away from you. The problem is, the shaft is being held firmly by the jaws. You could try to loosen the jaws a bit to allow the shaft to move a little but, I can all but guarantee, you're going to chase your tail as things will settle into different positions each time. If you don't loosen the jaws and try to strong-arm the TS over by 1.5 thou, a thin bar like that will bend (ever so slightly) as it rotates and you'll end-up with an inverted barrel profile. As is, what you're kinda doing, is a TS alignment test. To do that "by the book" you should spin between centers.
To do the 2-collar test (which is what I think you're after), you'll want to use a piece of stock at least 1-2" diameter -preferrably aluminum -and you'll want to relieve the center. Also, don't support the end in the TS. Take an extremely light cut as not to put a lot of force on the shaft.
Make sense?
Ray
- Joined
- Jul 1, 2012
- Messages
- 1,356
Re: Alignment
I tell folks to relieve the middle when checking the head-stock alignment with the bed. You could undercut the test bar you have but I would leave it the way you would be using it when cutting a shaft. It looks like the tail-stock needs to be adjusted over .0015 as it is now closer to the tool bit. I would mount a mag base on the bed with the shaft as straight or even with the center point as you can, mount the indicator on the bar and zero it Then loosen the tail-stock nut, but keep it snug and adjust the TS over, re-tighten the nut and see what the indicator reads. When you have it as close to .0015, take another cut. When the ends read the same measure the bar every inch or so and see what the readings are. This will show you if the bed is worn if the size changes. I am assuming you have the quill locked during the cuts, right?
I tell folks to relieve the middle when checking the head-stock alignment with the bed. You could undercut the test bar you have but I would leave it the way you would be using it when cutting a shaft. It looks like the tail-stock needs to be adjusted over .0015 as it is now closer to the tool bit. I would mount a mag base on the bed with the shaft as straight or even with the center point as you can, mount the indicator on the bar and zero it Then loosen the tail-stock nut, but keep it snug and adjust the TS over, re-tighten the nut and see what the indicator reads. When you have it as close to .0015, take another cut. When the ends read the same measure the bar every inch or so and see what the readings are. This will show you if the bed is worn if the size changes. I am assuming you have the quill locked during the cuts, right?
- Joined
- Nov 16, 2012
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- 5,596
Re: Alignment
BTW: If you're not familiar with the term "spin between centers", it mean you use a point at both the chuck and tailstock end and you drive the shaft with a "dog" which is an object that bolts to the end of the shaft and has a protrusion which comes in contact with a faceplate that is driven by the spindle. It's possible to mount a pointy piece in the jaws of a normal chuck and drive the protrusion off the face of the chuck. This is a little kludgy as it can scratch-up your chuck. Enclosed is a picture of a type of "dog" that I make which is very non-traditional but, it has an advantage of being somewhat balanced (unlike normal dogs) and is universally adjustable for different diameter shafts (unlike normal dogs). What's being shown is a MT3 center installed in the spindle and my special dog is bolted to a face plate. The dog also has adjustable beams that close-in on the shaft and some bolts in those beams transmit rotation to the shaft. Feel free to make one of your own... The idea was self produced but, it falls into the category of "intuitively obvious" and is at best worth a design patent -and I don't even bother with those.
Also, if you leave your setup alone and strong-arm the TS by 1.5 thou and if it cuts straight, it probably means your spindle bearings are wiggly and taking-up the slack.
EDIT: Here's a picture of a very traditional lathe dog being driven off a chuck face. I don't like doing this since it beats-up the chuck... (Picture taken from google images)
BTW: If you're not familiar with the term "spin between centers", it mean you use a point at both the chuck and tailstock end and you drive the shaft with a "dog" which is an object that bolts to the end of the shaft and has a protrusion which comes in contact with a faceplate that is driven by the spindle. It's possible to mount a pointy piece in the jaws of a normal chuck and drive the protrusion off the face of the chuck. This is a little kludgy as it can scratch-up your chuck. Enclosed is a picture of a type of "dog" that I make which is very non-traditional but, it has an advantage of being somewhat balanced (unlike normal dogs) and is universally adjustable for different diameter shafts (unlike normal dogs). What's being shown is a MT3 center installed in the spindle and my special dog is bolted to a face plate. The dog also has adjustable beams that close-in on the shaft and some bolts in those beams transmit rotation to the shaft. Feel free to make one of your own... The idea was self produced but, it falls into the category of "intuitively obvious" and is at best worth a design patent -and I don't even bother with those.
Also, if you leave your setup alone and strong-arm the TS by 1.5 thou and if it cuts straight, it probably means your spindle bearings are wiggly and taking-up the slack.
EDIT: Here's a picture of a very traditional lathe dog being driven off a chuck face. I don't like doing this since it beats-up the chuck... (Picture taken from google images)
- Joined
- Jul 1, 2012
- Messages
- 1,356
Re: Alignment
There are several ways to skin a cat as you can see many have different methods we have been taught and are trying to teach you You need to find the method that fits you and fits your tooling. I have turned several shafts using the loosening the tailstock as the bed is or was so worn I had to do it that way This is why I suggested you mic the shaft in several places. You will get push away in the middle, that is why you need to take a last clean up cut of .001". From the looks of your shaft you had a good finish. The last time I saw a machinist use a lathe dog on a lathe was 40 years ago in a high school. I see them in grinding shops used more on cylindrical grinders between centers.
There are several ways to skin a cat as you can see many have different methods we have been taught and are trying to teach you You need to find the method that fits you and fits your tooling. I have turned several shafts using the loosening the tailstock as the bed is or was so worn I had to do it that way This is why I suggested you mic the shaft in several places. You will get push away in the middle, that is why you need to take a last clean up cut of .001". From the looks of your shaft you had a good finish. The last time I saw a machinist use a lathe dog on a lathe was 40 years ago in a high school. I see them in grinding shops used more on cylindrical grinders between centers.
B
Bill Gruby
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Re: Alignment
I use the lathe dog many times. I also use the steady rest in conjunction with a cat head to keep the hold during offset turning crank journals. It's SOP and the easiest way to offset. This does take us a little OT, just saying that the lathe dog is used quite a bit in my shop. But then again this is as you say turning between centers, not what you are trying to accomplish here. Just pointing out that some use them on regularly.
"Billy G"
I use the lathe dog many times. I also use the steady rest in conjunction with a cat head to keep the hold during offset turning crank journals. It's SOP and the easiest way to offset. This does take us a little OT, just saying that the lathe dog is used quite a bit in my shop. But then again this is as you say turning between centers, not what you are trying to accomplish here. Just pointing out that some use them on regularly.
"Billy G"
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- Nov 16, 2012
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- 5,596
Re: Alignment
Bill, do you use the traditional style dogs? I bought a set long time ago and found they are not balanced and things vibrate like crazy beyond a certain RPM. Are there commercial ones that don't have that problem?
I'm thinking about selling the ones I have but am torn about it. I can't bring myself to pawn-off stuff I don't like in exchange for money.
Ray
Bill, do you use the traditional style dogs? I bought a set long time ago and found they are not balanced and things vibrate like crazy beyond a certain RPM. Are there commercial ones that don't have that problem?
I'm thinking about selling the ones I have but am torn about it. I can't bring myself to pawn-off stuff I don't like in exchange for money.
Ray
B
Bill Gruby
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Re: Alignment
Yes Ray. I also have some others that I made.
"Billy G"
Yes Ray. I also have some others that I made.
"Billy G"
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- Jan 11, 2013
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Re: Alignment
I use them too- but always the smallest I can use on a particular project. But I haven't really used them at very high speed.
I got a hood of some ridiculous size ones someplace, that won't even TURN on my 10L! Hah hah- still thinking (for a little while longer) that I might find some use for them before selling them for the mere $5 I could probably get.
Bernie
I use them too- but always the smallest I can use on a particular project. But I haven't really used them at very high speed.
I got a hood of some ridiculous size ones someplace, that won't even TURN on my 10L! Hah hah- still thinking (for a little while longer) that I might find some use for them before selling them for the mere $5 I could probably get.
Bernie