Edge Tailstock Alignment Bar

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umahunter

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Anyone have one of these alignment bars if so how do you like it ???202-0036D.jpg
 
This post describes a cheaper method. Its the method I use.

"The easiest way to make a test bar to align centers is to use a 12 inch piece of 1/2 x 13 threaded rod. centerdrill each end. At each end screw on a nut , a large washer and another nut to lock the washer. Place between centers, take a light cut on each washer(don't change depth of cut). If the diameters of the washers are equal, the centers are aligned."
 
I have the Edge alignment bar. It is about an inch too long for my 7x16 HF lathe. I have to do a little bit of gymnastics to use it with a dial indicator. It works great. I have no good way to check the bar, just turning some round bar stock 12" long I get the same diameter at both ends and in the middle after aligning my tailstock with the bar. As with all the Edge Technologies products the fit and finish are first rate.
 
any old shaft from a printer ect. should work.
 
The threaded rod and washers would work fine. I just use any old piece of scrap bar, center drill one end, then extend it how far I want (say 18" - 24"). Then I take a skim near the tailstock & note the cross feed dial position. Then back the tool out, and take another skim near the chuck to the same dial position (first time I did this I confirmed with a mag mounted dial). Tweak the tailstock set screws until the two locations mike to the same size.

It is pretty quick, very cheap. Doesn't take much longer than dialing in some special bar. I don't shift my tailstock very often - so I rarely have to repeat this activity.
 
An adaptation of Rollie's Dad's method can be used to set the tailstock. http://www.neme-s.org/Rollie's_Dad's_Method.pdf

You will need a test bar of uniform diameter. It doesn't have to be straight. The bar should be center drilled on both ends but the center drill doesn't even have to be on center. The explanation of how it works is also valid for running on centers. Mount the bar between the two centers and mount an indicator on the cross slide. Obtain a maximum and minimum indicator reading near the headstock and, without changing the cross feed. make another pair of readings near the tailstock. If the average of the readings is the same in both locations, the headstock and tailstock are aligned. If not, the difference in inches divided by the separation distance is the taper in inches/ft.

That's all there is to it. No turning required. Reusable. Cheap.

I made my bar from a salvaged roller from a printer. You can easily verify the uniformity of the bar with a mike. As the method states, the diameters don't even have to be the same; they just have to be known. The shaft does have to be round, again verifiable with a mike.
 
I watched the youtube video that Edge Technologies posted about using the tailstock alignment bar.
My question about using this bar is:
How do you isolate any change found on your dial indicator to be only due to the tailstock being out of alignment? There are many reasons to have varying readings on the dial indicator. Tailstock being out of alignment is only one.

My $0.02 is for you to save your $50 and use one of the methods posted above.

Mike
 
I watched the youtube video that Edge Technologies posted about using the tailstock alignment bar.
My question about using this bar is:
How do you isolate any change found on your dial indicator to be only due to the tailstock being out of alignment? There are many reasons to have varying readings on the dial indicator. Tailstock being out of alignment is only one.

My $0.02 is for you to save your $50 and use one of the methods posted above.

Mike
The Edge Technologies bar is using a special case of the RDM method where the diameters of the measuring surfaces are concentric with the center drilled ends so there is no runout and the reading at either end (hopefully) doesn't change as the bar is rotated so there is no need to rotate the bar. IMO, it is a small inconvenience to rotate the test bar and average the minimum and maximum readings so I'll save my $50 for other tooling.
While other factors can influence the dial indicator readings at either end, the readings will be a true indicator of what will happen if your turn a cylinder on centers.
 
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