Any tips to centering a MT3 dead center in a lathe?

[Pcmaker]

I'm trying to hold an MT3 dead center on my lathe. I used my 3 jaw chuck at first, then moved on to a 4 jaw independent chuck. There's a small part on the end of that dead center that's not tapered and that's where I'm holding it. I put 2 indicators on it, one of the left side and one on the right. I'm having a heck of a time trying to center it in. I can get centered at right end, but the left side is visibly wobbly, clearly not centered.

What am I doing wrong? Any tips? Do I even need 2 dial indicators to center this in? Using a live center, pushing on it from the tailstock side didn't help.

 

[Latinrascalrg1]

Your best and easiest option would be to chuck up a scrap piece of stock into your 3 jaw and turn a new dead center. The mt3 would usually fit the center bore hole in the lathe spindle or by using an adapter of some sort.

 

[RJSakowski]

What is the purpose for this? It will help to determine the best way to mount the dead center. Usually the tail end of the dead center is center drilled. I would make a center drilled adapter for the tail stock and use it along with a headstock mounted center and lathe dog to mount your work.

 

[Pcmaker]

I want to line up the MT3 taper to my compound slide so I can turn a new MT3 taper for a tailstock die holder project I want to do

 

[T Bredehoft]

Use the sine of the appropriate angle to set your compound, put the tool exactly on center vertically, (otherwise it wont turn a true taper) and have at it.

 

[bill stupak]

chuck up a piece of scrap, center drill it, mount another center in the tail stock, put the first center in between. Accuracy is dependent on the tail stock being aligned.

 

[JimDawson]

Here is how I set mine to to turn a MT 3 taper


To turn this taper

 

[RobertB]

Using a live center, pushing on it from the tailstock side didn't help.

If this did not center the end, then your tailstock alignment needs to be fixed.

 

[bill70j]

I put 2 indicators on it, one of the left side and one on the right. I'm having a heck of a time trying to center it in. I can get centered at right end, but the left side is visibly wobbly, clearly not centered.

What am I doing wrong? Any tips? Do I even need 2 dial indicators to center this in? Using a live center, pushing on it from the tailstock side didn't help.

One problem you may have had with the 2 indicators is that one or both of the indicators might not have been precisely on center. If not on center, the indicators will be simultaneously measuring taper and diameter difference.

So If the right side indicator was on center and showed zero delta along the taper, but the one on the left showed an increasing delta, then the one on the left was measuring the taper, but also measuring circumferential difference.

 

[RJSakowski]

I want to line up the MT3 taper to my compound slide so I can turn a new MT3 taper for a tailstock die holder project I want to do

From your second post, I gather that you wish to use your MT3 taper as a gauge to set the compound for turning a new taper. Setting up as Bill S. suggested, You should not have any runout. However, the accuracy of your gage is highly dependent on the tailstock being on the spindle axis both vertically and horizontally at the position the tailstock is at. This can be difficult to determine.

I would center drill a piece of bar stock and extend it to engage the dead center with the tailstock the same position that it will be in your setup. Then turn two collars, one near the chuck and the second near the tailstock. The two diameters should be the same. If the tailstock diameter is smaller, move the tailstock back and vice versa. Repeat the process until you have equal diameters.

The tailstock may still be above or below the spindle axis. To check that, I would mount an indicator on the cross slide and sweep across the top of the two turned surfaces. The readings for both collars should be the same at the point of maximum deflection. Changing the height of the tailstock will affect the turned diameter slightly so the process should be repeated.

When you have passed this test, the MT3 center can be used as a gage. Observe the precautions that bill70j stated. when setting your compound angle. I would set the dial indicator height at the small end of the taper as it is most sensitive to variations in height there.