Last night I was playing around on the lathe getting some practice in and I installed my 4 jaw independent chuck and centered in my work near perfect within .0005 and put my alignment tool in the tail stock and aligned the tail stock within.001. then cut a shaft and it measured right on time. I then took off the 4 jaw and put the 3 jaw scroll chuck back on and cut a shaft and it was cut on a .006 taper. I know that I am new to this but shouldn't a center be the same from chuck to chuck? Some of you guys with lots of knowledge and experience please tell me what I am doing wrong. Do you have to re-align the tailstock with every chuck change? It is an old Enco lathe and from what little experience it all works great. Prolly my not knowing how to do things is the problem. thanks
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Tail Stock Alignment
- Thread starter COPE 19
- Start date
- Joined
- Sep 25, 2014
- Messages
- 1,111
"shouldn't a center be the same from chuck to chuck?" No
That would be nice if it was.
"Do you have to re-align the tailstock with every chuck change?" No
Nothing is perfect. Your chucks, any chuck, will not have the axis in absolutely perfect alignment with the long axis of the bed. A 4-jaw you can dial in so that the radial run out is good in one plane (say an inch out from the chuck), but further down it will be out a little bit - because it is off axis. A 3-jaw scroll style chuck will have some radial run out and be off axially.
That is called life. Dealing with this type of issue is called machining. You can (and should) fuss with it, and you can improve your results. You can pay more money and get better results.
You will get lots of good ideas, in feedback on this thread, or reading old threads (this topic comes up quite often). Welcome to Hobby Machinist.
Regards, David
That would be nice if it was.
"Do you have to re-align the tailstock with every chuck change?" No
Nothing is perfect. Your chucks, any chuck, will not have the axis in absolutely perfect alignment with the long axis of the bed. A 4-jaw you can dial in so that the radial run out is good in one plane (say an inch out from the chuck), but further down it will be out a little bit - because it is off axis. A 3-jaw scroll style chuck will have some radial run out and be off axially.
That is called life. Dealing with this type of issue is called machining. You can (and should) fuss with it, and you can improve your results. You can pay more money and get better results.
You will get lots of good ideas, in feedback on this thread, or reading old threads (this topic comes up quite often). Welcome to Hobby Machinist.
Regards, David
- Joined
- Dec 27, 2014
- Messages
- 658
3jaw chucks almost never clamp work well centered.
Even if the work does clamp up centered where you measured it, most chucks will not clamp the work parallel to the ways.
Used ones will usually have worn spots that make some sizes even worse, and worn jaws that have a bell mouth.
If you want convenience use a 3jaw.
If things need to be very close to on center, use a 4 jaw
if you want things to be perfectly on center, turn between centers.
Is there a reason you want the work perfectly on center?
I am curious what alignment tool you used. Could you provide a link or pic?
getting something near center in the chuck and then using a tool that revolves in the tail stock just creates a situation of compounding error most times.
You can usually get as good results by simply putting a scale between the centers and adjusting til it is perpendicular to the ways.
Even if the work does clamp up centered where you measured it, most chucks will not clamp the work parallel to the ways.
Used ones will usually have worn spots that make some sizes even worse, and worn jaws that have a bell mouth.
If you want convenience use a 3jaw.
If things need to be very close to on center, use a 4 jaw
if you want things to be perfectly on center, turn between centers.
Is there a reason you want the work perfectly on center?
I am curious what alignment tool you used. Could you provide a link or pic?
getting something near center in the chuck and then using a tool that revolves in the tail stock just creates a situation of compounding error most times.
You can usually get as good results by simply putting a scale between the centers and adjusting til it is perpendicular to the ways.
I used the one that I saw Tubalcain demonstrating, A MT2 in the tailstock turned on the end and stock in the chuck turned to the exact measurement (within .0005). It cut really good and very close using the 4 jaw but when I put the 3 jaw back on that is when things went hay
wire. I will admit it is not a hi dollar chuck, it is a shars but has only about .0025 run out. I will try to get pics tonight. I reset the tailstock last night but ran out of time but had it cutting very close. I will get back on it as soon as time permits. What is the least expensive and easy to cut while practicing thru the learning process. I am not cutting anything critical just figured the 3 jaw being new would be easier/closer but I understand what you are saying. Its just a hobby that I enjoy and want to get it as close as I can. Its like lots of other trades, it is easy when you see a pro do it. I will just keep at it and reading every chance I get. I am not sure I understand the scale between the center method you are mentioning but I will try to find it. I did try cutting on centers and as you said that was more accurate. Still practicing shaping and sharpening bits and turning and measuring. Thanks for all the help.
wire. I will admit it is not a hi dollar chuck, it is a shars but has only about .0025 run out. I will try to get pics tonight. I reset the tailstock last night but ran out of time but had it cutting very close. I will get back on it as soon as time permits. What is the least expensive and easy to cut while practicing thru the learning process. I am not cutting anything critical just figured the 3 jaw being new would be easier/closer but I understand what you are saying. Its just a hobby that I enjoy and want to get it as close as I can. Its like lots of other trades, it is easy when you see a pro do it. I will just keep at it and reading every chance I get. I am not sure I understand the scale between the center method you are mentioning but I will try to find it. I did try cutting on centers and as you said that was more accurate. Still practicing shaping and sharpening bits and turning and measuring. Thanks for all the help.
If I understand what COPE19 is saying he first turned a shaft in his 4 jaw using the tailstock to support the outboard end resulting in a shaft with no taper. He then changed to a 3 jaw chuck and again using the tailstock to support the outboard end he ended up with a tapered shaft. If I got this right the tapered shaft is not a result of switching chucks as they revolve around the spindle axis which does not change. It appears the tailstock did not lock down in the same location. Could be the clamping mechanism, chips or grit under the tailstock, or the upper half of the tailstock not tightened sufficiently to the lower half.
Tom S.
Tom S.
- Joined
- Dec 27, 2014
- Messages
- 658
Not sure which video you mean. Tubalcain has a bunch of videos on this, and most of them are maddeningly over complicated.
Are you referring to this one?
Here is the issue trying to re-use the test bar in a three jaw chuck.
If you put raw stock in the 4 jaw, the machined end will never be concentric to the part clamped. This is because the raw stock it not round. Even if you centered it to 0.0005", it will still only be that close to center on those 4 areas that are clamped. The 3 jaw will clamp on different parts and the spigot will not be on center. Clamping marks and distortion will lead to further error.
You would have to put stock that is already machined round in the 4jaw, and get it perfectly on center, then turn the spigot. Since you will never get the stock perfectly on center, it will always introduce some error, the error will compound. You would need to turn a new test bar each time you used this method.
You will notice that Tubalcaine is not putting it in a chuck, he is using the headstock MT.
Really though, anything that you are comfortable with, that is actually aligning the axis of the spindle to the tail stock is fine.
All that is important is that they line up close enough for the kind of work you are doing. If you are doing very precise work that requires a great deal of repeatability, then nothing beats a taper test - it is how the machines that make test bars are aligned. If you just need to support the end of longer stock or drill holes, it is enough to bring the points together with a scale between them. this will get the alignment to under 0.001" in the same amount of time it takes to loosen, adjust, and tighten the tail stock.
The "best" method for this is the method that brings you the most joy (or least frustration), and does the job well enough for what you are doing. Getting the tail stock in under 0.005" alignment is a waste of time for most work, but doing this brings many of us more enjoyment (myself included).
The "scale" method I was referring to is an old school way to align the tail stock. You just put a center in the head and tail stocks, and bring them together with your pocket scale between them. Any mis-alignment will cause the scale to cock at an angle. If the points are in perfect alignment, any flat thing clamped between them will sit perfectly perpendicular to the axis of the spindle. I do not align my tail stock this way, but I do use it check alignment before I turn between centers.
Are you referring to this one?
If you put raw stock in the 4 jaw, the machined end will never be concentric to the part clamped. This is because the raw stock it not round. Even if you centered it to 0.0005", it will still only be that close to center on those 4 areas that are clamped. The 3 jaw will clamp on different parts and the spigot will not be on center. Clamping marks and distortion will lead to further error.
You would have to put stock that is already machined round in the 4jaw, and get it perfectly on center, then turn the spigot. Since you will never get the stock perfectly on center, it will always introduce some error, the error will compound. You would need to turn a new test bar each time you used this method.
You will notice that Tubalcaine is not putting it in a chuck, he is using the headstock MT.
Really though, anything that you are comfortable with, that is actually aligning the axis of the spindle to the tail stock is fine.
All that is important is that they line up close enough for the kind of work you are doing. If you are doing very precise work that requires a great deal of repeatability, then nothing beats a taper test - it is how the machines that make test bars are aligned. If you just need to support the end of longer stock or drill holes, it is enough to bring the points together with a scale between them. this will get the alignment to under 0.001" in the same amount of time it takes to loosen, adjust, and tighten the tail stock.
The "best" method for this is the method that brings you the most joy (or least frustration), and does the job well enough for what you are doing. Getting the tail stock in under 0.005" alignment is a waste of time for most work, but doing this brings many of us more enjoyment (myself included).
The "scale" method I was referring to is an old school way to align the tail stock. You just put a center in the head and tail stocks, and bring them together with your pocket scale between them. Any mis-alignment will cause the scale to cock at an angle. If the points are in perfect alignment, any flat thing clamped between them will sit perfectly perpendicular to the axis of the spindle. I do not align my tail stock this way, but I do use it check alignment before I turn between centers.
Gotcha now with the scale. I only put the MT in the tail stock. I put round stock in the chuck, not tapered with both ends machined to the exact same size. I will get back on it tonight and re-align with the 3 jaw and give it another shot. Thanks again.
- Joined
- Feb 26, 2014
- Messages
- 257
Try this for quick and accurate alignment.
http://www.frets.com/HomeShopTech/QuickTricks/TailstockAlignment/tailstockalignment.html
Bill
http://www.frets.com/HomeShopTech/QuickTricks/TailstockAlignment/tailstockalignment.html
Bill
- Joined
- Sep 18, 2014
- Messages
- 254
Don't see how that can happen, myself. The chuck end is spinning with the long axis regardless of the chuck. Even if the chuck ran out a ton, turned shaft should be straight from end to end, once dialed in. Some difference, sure, but I would expect a thou or two at most. Personally not a fan of the scale method of alignment, but it works for some. And just because you put centers in both ends and pull them together, doesn't mean they will be aligned when in use several inches apart. Could be the bed ways are 'tweeked' a bit. This can affect the turning from end to end as well.