Aligning the tailstock on a 9x20 lathe.

[Kmot]

Of the few long'ish pieces I have tried to machine on my lathe, they have always had some taper to them. I have set the tick marks on my tailstock to "zero" but that has not removed it.

I have never been able to get rid of the taper in my 9x20 lathe. I certainly don't know how it is supposed to be done, but here is a method I tried today and I hope it will work.

I installed a MT2 holder with a brand new dead center into the chuck, and then I used my dial indicator to get it as round as possible. I got it to .001" TIR. I then placed an identical brand new dead center in my tailstock.

Using a high power magnifying glass and a piece of white plastic as a background I brought the two dead center points together at near touching but not quite. Then looking straight down as best I could I moved the tailstock over so that the points were perfectly aligned. As you can see by the tick marks, they are not on Zero anymore.

I hope this will make an improvement. I do not have one of those perfect and true machined bars to place in the chuck and then measure across.

So, do you guys think this was a good way to adjust it?

 

[techonehundred]

You just made that spotting tool. chuck it up and put it to use. It will give you a very good starting point.

 

[ironman]

Kmot, I have that lathe also. When I adjusted mine to center the marker was not lined up eithere. Mine (marker) shows to be off but the centers are point to point. ironman (Ray)

 

[Ken I]

Kmot,
See the thread I started under "Tips & Tricks" - the guys came back with several ways of skinning this particular cat.

Regards,
Ken

 

[Kmot]

You just made that spotting tool. chuck it up and put it to use. It will give you a very good starting point.

Wow! Never would have thought of that! I would never have used it in anything but the mill. Doh!

 

[Kmot]

Kmot,
See the thread I started under "Tips & Tricks" - the guys came back with several ways of skinning this particular cat.

Regards,
Ken

I will look for it Ken, thanks.

 

[mklotz]

Once you get everything aligned, make yourself a set of alignment buttons so it will be easier to do next time. Here's Frank Ford's words and music about how to make them...

http://www.frets.com/HomeShopTech/QuickTricks/TailstockAlignment/tailstockalignment.html

 

[Dan Rowe]

Nice tip Marv,

He did not make a set of buttons though. He left the stock he made the button with in the chuck so it remained true to the spindle. This way any 3 jaw chuck error is eliminated.

It seams to me a button set would only be useful with a 4 jaw chuck or a collet system.

Dan

 

[mklotz]

Yes, you're right. I should have reread Frank's description before posting.

The trick is to make two buttons of the same diameter, each with a center hole. Put a center in both the headstock and tailstock with the buttons caught between the two centers. Now, a mike across the button interface will show the TS displacement. Actually, a calibrated fingernail can be used in place of the mike - human fingers are incredibly sensitive.

 

[Bolster]

Regarding your "dead centers kissing" technique...I do something similar when rough aligning my rotary table under the quill of my mill...interestingly when I use a DTI to finish the job, I find the "dead centers kissing" technique usually gets me only within about .015 - .020. So as others have said, it gets you within range quickly, but probably won't take you all the way to where you want to go. I suspect one issue is that (inexpensive) dead centers are not necessarily absolutely concentric, and another is that the eye is only good down to several thousandths. At least...MY eyes.

 

[Kmot]

My alignment method seems to have paid off. I also installed the scope to verify as suggested.

I just turned a piece of 1.250" brass into a burner port for a boiler and it came out very nice and straight.

 

[Tin Falcon]

Army TCTO 9-524 chapter 7 has a lot of lathe basics.
http://www.metalworking.com/tutorials/army-tc-9-524/ch7.pdf
They mention the cut and try method and the test bar method.
looks like you figured it out.
Tin

 

[Kmot]

Thanks for the link, Tin. US Army technical manuals are awesome! Thm:

 

[picclock]

FWIW you can put a dead centre in the tailstock and use a DTI with a magnetic base stuck to the chuck and the tip on the edge of the centre. Rotate chuck and get runout. It will give super accurate results but is a pain to see (mirror and torch job). Don't forget to lock the tailstock, and also check the centering when the ram is at extremes of position.

Best Regards

Picclock

 

[Kmot]

That's a great tip! Thanks for that Picclock,

 

[Kmot]

Hey guys, I just obtained a coaxial indicator kit. I actually bought it to use with my mill but I saw that I can also use it with a lathe. So I tried it out today on my 9x20. Each tick mark on the gauge represents .0005" offset. I was able to fine tune the tailstock ram to only one tick mark. So for total offset I double that, correct? That would make my total runout .001"?

Is .001" TIR a respectable center to center setting? Or does it have to be a perfect .000"?

 

[Kmot]

I guess this was the wrong question to ask. :big:

Anyway I found out, for anyone that may be interested, that the TIR on this type of measuring instrument is actually 1/2 of what is indicated. So in this case my TIR was .00025 which I will assume is good enough.

 

[mklotz]

I'm having trouble understanding how the marks on a coax gauge can be assigned an absolute size. Won't the displacement indicated on the dial depend on the effective lever arm of the tip used on the coax?

 

[Kmot]

I wouldn't have a clue!

 

[Brian Rupnow]

Once you get everything aligned, make yourself a set of alignment buttons so it will be easier to do next time. Here's Frank Ford's words and music about how to make them...

http://www.frets.com/HomeShopTech/QuickTricks/TailstockAlignment/tailstockalignment.html

I just aligned my tailstock using the method in this link, and it worked great!!! Thanks for posting the link, Marv. I would be ashamed to tell anybody how much "out of spec" my tailstock was. I had aligned it 'By eye" about 3 or 4 months ago, and in a moment of insanity I loctited the adjusting screws. Today everything in my world slowed down enough that I was able to take the entire tailstock out to the main garage, fire up the oxy acetylene and get enough heat into things to soften up the loctite so I could remove the adjuster screws, clean off the loctite, and rejig things as per the link. It works fine now, and barely blistered the paint. ;D ;D ;D