To quickly align your tailstock:
- Face and center-drill some scrap steel, round 1/2″ about 5 inches long.
- Insert a dead center on the tailstock.
- Mount your dial indicator so it touches a flat section of the dead center, right after the 60°, make sure you are on a flat by moving the tailstock quill back and forth, your indicator dial shouldn’t deviate.
- Once you’ve setup the indicator, you can now push the dead center onto the center you drilled before. If your tailstock is misaligned your indicator will show a slight deflection as everything slightly flexes toward center.
- At this point, you can go back and forth adjusting the tailstock setscrews until pushing the dead center won’t yield a deflection on the indicator dial.
You can easily get your tailstock centered within a thou or less using this method in under 5 minutes. Depending on whether you use a test indicator or a dial indicator, you can improve the alignment furthermore based on the available accuracy and resolution of your indicator.
Just keep in mind a test cut is always a good way to know for sure if you’re in dead center. Of course this requires the use of a known good micrometer and lots of time and patience. The alternative is to use a calibrated rod and indicate throughout the X travel for deviation, but the rod has to be held within centers.
Step 1 is very important, the part has to be center drilled on the spot every time for a good reference. You can use the same part twice (working on either side) afterwards you’ll have to face the center marks off or start from another scrap piece.
Once you are happy with the alignment:
Don’t forget to lock the setscrews against each other. Do this while indicating to make absolutely sure you aren’t pushing the tailstock to either side.
If after the alignment you still have issues, chances are you need to look into shimming your tailstock as wear has brought it’s height down from center. This is unfortunate, but it does happen. Bigger machines have removable contact plates that can be remade to deal with this, other machines can be coated or utilize teflon contact surfaces that are replacable. But typically if you have a solid cast iron base, you have to shim it.
The alternative is to machine a new lower plate / base for the tailstock, making it so the contact areas are replacable. Problem with more parts is, more chance of the parts actually moving and causing trouble. Your choice though.
This method relies on flexing of the part and the actual tailstock quill, it doesn’t matter how big or small your lathe is, all parts flex and we can use this to our advantage.