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turbo_rob
05-17-2013, 07:41 AM
Hello All,
Been reading and searching for idea for checking the setup of my lathe. I will try to give all the info I can. Also I am not a machinist just a hobby guy making a few parts for my own motorcycle.
Lathe is a standard modern 13/34 I have it sitting on concrete floor and leveled the best I can with a 6 inch craftsman spirit level. I am using quick change tool post holder phase 2 250 with 1/2 carbide inserts. I have read to use a 2 or bigger bar and make a cut and measure both ends to check alignment. The setup is 4 jaw chuck with a 2 diameter mild steel bar. Length from face of chuck is 10. I made a few light cuts. I read somewhere on the net (never know if it good info that why Im here) to turn at slowest speed and very light cut. I have tried slow and fast making light cuts and getting the same results.
Result is chuck side measurement is .003 smaller that the free hanging side. No tailstock being used. Chuck side is 1.976 free hanging side 1.979 this is over a 10 distance. I have check the bearing in the head by putting a dial on the side of the chuck and used a brass bar to push the front and rear of the shaft inside the head. Very little movement less than a .001. I want to get it setup correctly before using.
I guess my main reason to be here is to gain wisdom from people who know. What would be my next step or should I start over. :confused:
Rob

Dr Stan
05-17-2013, 08:23 AM
You really need to set up the test bar in between centers. I recommend that you pick up a copy of both the South Bend "How to run a lathe" and the US Navy's "Machinery Repairman 3 & 2" as reference books. The MR 3 & 2 is available for a free download, but it lacks all the graphics. Lindsay Technical Books was an excellent source until it shut down. Hopefully other members may know of a different source.

How to run a lathe should be available on EBay.

BTW, welcome to the asylum. :)

ammcoman2
05-17-2013, 08:30 AM
Do you know if the headstock was removed for transporting the machine? The reason I bring this up is that I did this to get mine (1120) into the basement. After re-assembling the lathe I got the same results. After two tries with stoning and cleaning I finally got the headstock set up correctly. I can only surmise that a piece of swarf or a burr was present on the mating surfaces.

Another possibility is that the chuck's jaws are out of alignment. After chucking the bar a DTI reading of the part near the end should be done to see if there is a high reading. Also does it follow the bar or the chuck when rotated in the chuck.

And a third one is that the carbide tip is deflecting the part. For this test you should use HSS or a high shear carbide (AK style) to minimise side forces. A regular carbide tip needs about 600rpm for that diameter and a minimum of 0.003" depth of cut.

Geoff

Mike279
05-17-2013, 08:55 AM
I agree that you should get a reference book or two on how to run a lathe. I have Machinings Fundamentals "Goodheart Wilcox" from the seventies. That one includes most shop tools. Setting up a lathe right once will ensure you get the best starting point you can. Running a lathe safely should be your first objective. Making parts is really about learning the practices and using the lathe correctly. I have reference books from College and took courses there. Once you get the safe routines and basic knowledge you will be able to make things easily and safely. Cutting speeds of materials and tool geometry can be easily referenced to speed the learning curve. I don't know exactly about the spirit level you used, but I picked up a Starret Machinist level to do my lathe. Once set, my cheap Atlas has been giving great service for over twenty years. Mike

winchman
05-17-2013, 09:47 AM
Just for fun, put your dial indicator on the OD at the outer end of the bar. Push/pull the bar and see how much deflection you get. I'm thinking the chuck isn't holding the bar absolutely rigid, and that's what's causing the outer end to be a little larger.

.0015" deflection ten inches out from the chuck probably won't require a great deal of force. That's why you should do the turning to check alignment between centers as mentioned.

Of course the suggestions for learning more about how to use a lathe are spot on.

darryl
05-17-2013, 05:47 PM
Agree with all the advice to read the books- How to run a Lathe is supposedly a good one, though I haven't read it. I would check through this forum and read all the posts on aligning a lathe as well. There is a lot of useful information there, plus some ideas on where you could go wrong.

Leveling a lathe is not making it level in the traditional sense, although having it level is nice. Leveling in this sense is making sure the front way and the rear way are in the same plane, which essentially means taking any twist out of the bed.

One thing I would mention at this point, since you have taken a light cut on a bar already, is that deflection can occur easily, and finding the outboard end of the workpiece larger in diameter than the inboard end (close to the chuck) is common, and does not definitively mean the lathe is out of alignment. You have an overhang of about 10 inches, so even though the bar is 2 inch diameter, it could be deflecting by a thou or two and causing that end of the bar to be wider than it should be. Your lathe could be perfectly aligned and this can still happen. It has a lot to do with the geometry on the cutting tool.

I would not attempt to make any adjustments to the lathe until you have read up, at which point you will have asked more questions here.

Don Young
05-17-2013, 09:11 PM
I do not disagree with any of the previous advice. Your experiment and results really do not indicate any problem with the lathe. It could just as well be a normal result of the setup because of normal deflection and tolerances of the lathe and chuck.

beckley23
05-17-2013, 10:43 PM
You did the turning test correctly. What you did in known as the 2 collars test, without the collars. You most likely need to raise the right rear leveling pad just a bare minimum, which will move, twist, the TS end forward, or you could raise the left front pad, which move, twist, the HS end towards the rear . This is the hard way to level the lathe, and it's a pure guessing game that can get quite frustrating. A precision level would go a long way to make this job easier.
Aligning the tailstock is done with a test bar between centers.

You're going to get a lot recommendations, but the underlying problem is that you don't know if the bed is level, and a carpenters level is the wrong tool, it simply isn't accurate enough for this type of work.
Harry

dian
05-18-2013, 05:25 AM
interesting, i would raise the right front pad. no?

John Stevenson
05-18-2013, 05:36 AM
interesting, i would raise the right front pad. no?

That's the way I read it given outboard end is smaller

bandsawguy
05-18-2013, 05:48 AM
No he says in the original post the chuck end is. 003 smaller.

John Stevenson
05-18-2013, 05:52 AM
Sorry my bad, read it wrong so yes it is the right rear pad but to get a true result it does need the two collars machining then a light skim taken.
Turning a complete bar doesn't allow the tool to take a true cut, only gradual.

It could be that the machine is better than stated if this is done, as it usual to have the unsupported end larger than the chuck end just thru deflection.

turbo_rob
05-18-2013, 08:45 AM
Thanks every one for all the tips. I will be looking into the books suggested. Also a machinist level. I have read and watched about everything I could find on the setting up the lathe on the internet. Safety 1st always. I did take two dials and checked by pushing and pulling the end of the bar, I was amazed how much the bar moved. So that got me thinking. I put another indicator on the chuck jaw and one on the outside of the chuck. Did the push pull again. No movement in the chuck but movement in the jaw. So I’m looking for a dead center and need to find a replacement cam lock pin for the lathe dog plate. As far as transporting the lathe I moved it myself with my wife’s help. It was not taken down during the move. I have a sizeable engine crane and straps made for moving heavy engine parts. So 1st step, level with the right level set up for turning on centers. I would like to say thanks again to all of you for your help and wisdom. I’m sure I will be asking more question in the future. I will report back when I complete the next few steps.
Rob

turbo_rob
05-18-2013, 09:09 AM
Where would my best bet be for finding a spindle nose sleeve? #5MT to a #3MT sleeve? This is the way it is shown in the book. A tapered sleeve then a #3MT dead center sliding into it. I guess I need to measure how far the nose is tapered and see it a #5 would be ok to use by its self. My concern would the #5 stick out to far passed the lathe dog plate?

beckley23
05-18-2013, 12:04 PM
Here's one of my test cuts on a lathe that got a partial reconditioning. The bar started out as 2-1/2"D and is sticking out approx 14". The cut was performed so that I could see the accuracy at several points.
http://img.photobucket.com/albums/v152/beckley23/se221.jpg

That picture is from post #191 in this topic.
http://www.practicalmachinist.com/vb/monarch-lathes/another-new-toy-163406/

You can get a #5 to #3 MT sleeve. IIRC, they are offered in hard and soft versions, and you will need a soft #3 MT dead center, that should have the 60* end turned in place after mounting in the spindle.
Harry

john11668
05-18-2013, 06:11 PM
I would level the machine with the best level you can lay hands upon!

Take the required light cut, then reverse the feed and cut back.

Then measure! A thou in ten inches is not a lot! Most of us have machines which have been moved. it would not be surprising to see a headstock shift by a thou or two!

darryl
05-18-2013, 06:58 PM
A thou difference in diameter from end to end is 1/2 thou difference in cutter position, or conversely the bar position relative to the cutter. Over 10 inches, I'd say that's pretty good. I think you could be in for a real fight to get it better, and chances are pretty good that it will get worse. Where would you find a shim thin enough to help you make such fine adjustments- and how would you constrain the stand to keep it from changing this over time-

I realize though that we're talking 3 thou over 10 inches, which is about where my lathe stands at the moment, and which I live with easily. One day I'll add some outboard bed mounting tabs so I can more easily adjust out the small twist- if that is what is responsible for the error.

In this case there has been mention of adjusting the headstock, but it has not been determined where the error is coming from. With the proper sensitive level you can detect twist in the bed, then with enough care you can shim it out- hopefully the stand does not contribute to this moving around on you. IF all is well at this point, then you could consider adjusting the headstock if a consistent error exists. I think it's likely that just the act of loosening, adjusting, and tightening the headstock is going to have some effect on the bed, so you're really in the thick of it here. But if it's determined that the headstock is out, then work on that.

Realistically, I think the 'problem' should be approached from the ground up. It starts at the floor, which could be flexible. It goes through the legs of the stand, the structure of the stand, the give in the material where the bed mounting bolts attach, etc. I think it would be wise to have the entire picture in mind, and be willing and able to deal with all of it before you loosen even one bolt.

winchman
05-19-2013, 02:31 AM
The OP has already determined that the bar is not being held rigidly in the chuck, so there's not much you can do with the results (.003" larger on the outer end) of his first test. See post 13. "I did take two dials and checked by pushing and pulling the end of the bar, I was amazed how much the bar moved. So that got me thinking. I put another indicator on the chuck jaw and one on the outside of the chuck. Did the push pull again. No movement in the chuck but movement in the jaw."

Unless you plan on doing very precise work on long pieces on a regular basis, I'd suggest not worrying about the lathe alignment for now. Learn how to use the lathe, and have some fun making things.

Deal with the alignment when you find you can't do the things what you want to do because the machine is out of kilter.

ammcoman2
05-19-2013, 09:21 AM
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Where would my best bet be for finding a spindle nose sleeve? #5MT to a #3MT sleeve? This is the way it is shown in the book. A tapered sleeve then a #3MT dead center sliding into it. I guess I need to measure how far the nose is tapered and see it a #5 would be ok to use by its self. My concern would the #5 stick out to far passed the lathe dog plate?
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KBC in Mississauga have them but they may be longer than the "official" length. The one I have that came with the lathe is 3" long. If you get a soft version you could shorten it to suit. Add a step on the rear side OD so you don't set up a burr when knocking it out.

Geoff

turbo_rob
05-21-2013, 07:40 PM
Thanks I will look in to that. Just a update on the cutting true with no taper. It may not be the correct method but using the tailstock and the chuck I have been able to make bushings dead on with no taper. Thanks mostly to all you good people and your replies.