Gunsmithing Lathe alignment issue.

[rigmaster10]

I have a Grizzly G4003 Gunsmithing lathe. And my question is how do you check alignment between the headstock and tailstock. Also how do you check to make sure it is properly square in all ways. I have built three rifles on it now and there doesn't seem to be any real issues. But as I become more knowledgeable. I have more questions on everything. Like how do I know the lathe is set up correctly

 

[BrianLara400]

(Would do this one first)Headstock alignment involves chucking a length of bar unsupported and taking a light longditudinal cut near the jaws and then using the same setting (keeping backlash in mind) take a second cut 8-12" away*, farther down the length of the bed. Then "miking" these 2 cut diameters they should be reading exactly the same (or near, not sure what a realistic tolerance for that brand of machine to hold is?) (*what ever distance you can manage with out inducing chatter - can't comment on the rigidity of the grizzly - however the more span the better for accuracy) Should these 2 measurements be significantly different the headstock will need to be minutely rotated so as it no longer turns tapers & the spindle axis/carriage movement are back in parallelism again. Another alternative is grip a length of a ground test bar and dial indicate along it from your carriage/tool post whilst traversing. (Would do this after the your headstock alignment is proven) Tailstock alignment involves turning a piece of bar "between centres" with a freshly cut centre in your chuck/headstock (and don't take it out until alignment is correct) and a high quality live centre in your tail stock. the piece of bar will need to be "driven" by a drive dog at the chuck end. Take 2 cut's wide apart as per the first method and check for differences of measurement between. Ideally they will "mike" exactly the same, if not it is turning tapers and the tailstock will need to be shifted minutely one way or the other perpendicular to the spindle axis. When correcting a tailstock, would be smart to have an indicator set against it on the bedway - so as you can accurately gauge just how far your moving it and should be able to calculate the ideal location. Good luck with it mate

 

[maccrazy2]

(Would do this one first)Headstock alignment involves chucking a length of bar unsupported and taking a light longditudinal cut near the jaws and then using the same setting (keeping backlash in mind) take a second cut 8-12" away*, farther down the length of the bed. Then "miking" these 2 cut diameters they should be reading exactly the same (or near, not sure what a realistic tolerance for that brand of machine to hold is?) (*what ever distance you can manage with out inducing chatter - can't comment on the rigidity of the grizzly - however the more span the better for accuracy) Should these 2 measurements be significantly different the headstock will need to be minutely rotated so as it no longer turns tapers & the spindle axis/carriage movement are back in parallelism again. Another alternative is grip a length of a ground test bar and dial indicate along it from your carriage/tool post whilst traversing. (Would do this after the your headstock alignment is proven) Tailstock alignment involves turning a piece of bar "between centres" with a freshly cut centre in your chuck/headstock (and don't take it out until alignment is correct) and a high quality live centre in your tail stock. the piece of bar will need to be "driven" by a drive dog at the chuck end. Take 2 cut's wide apart as per the first method and check for differences of measurement between. Ideally they will "mike" exactly the same, if not it is turning tapers and the tailstock will need to be shifted minutely one way or the other perpendicular to the spindle axis. When correcting a tailstock, would be smart to have an indicator set against it on the bedway - so as you can accurately gauge just how far your moving it and should be able to calculate the ideal location. Good luck with it mate

Above is good info. Also make sure lathe bed is properly leveled with a machinist level before doing the checks.
One quick test I do to check the tailstock is to cut a 60deg center hole with a centering drill then run the live center into the hole and look for an even space all around as you run it into the hole. This is not a substitute for the above method but just a quick check I used to do when I had to offset my tailstock to turn a taper over a 30 in piece and then had to recenter the tailstock. It gets you real close before fine tuning it all the way

 

[ugsly]

I use a set of centering buttons If Im way out of whack (profiling a barrel) then mount a ground and polished 12" rod between center and check it with indicators.

Kc

 

[cal50]

I have a Grizzly G4003 Gunsmithing lathe. And my question is how do you check alignment between the headstock and tailstock. Also how do you check to make sure it is properly square in all ways. I have built three rifles on it now and there doesn't seem to be any real issues. But as I become more knowledgeable. I have more questions on everything. Like how do I know the lathe is set up correctly

You can cut a test bar or use the dial indicator method.

Initial Lathe Set-up


I mounted my lathe on the rubber machinery pads / feet you get from Enco or MSC. It cuts down on vibration. Level the lathe bed using a machine level and once you get it right cut a test bar. You ideally want a bar with two narrow diameters to cut to minimize deflection. My lathe was perfectly level but not cutting parallel so I needed to raise the tailstock end to make it within a couple tenths. I was off about .003 over 12 " on my test bar.

Its quick and easy.

If you use the rubberized machine isolation pads check your level about 6 months after. I feel they tend to settle some. Mine did not change but its still worth checking.

 

[E. Bryant]

A quick-n-dirty way to check headstock/tailstock alignment is to clamp one end of an edge finder in the chuck, dial it in, grab the other end with a collet in the tailstock, and measure the offset along the top and side using a DTI or dial indicator.

 

[Mark Housel]

A quick-n-dirty way to check headstock/tailstock alignment is to clamp one end of an edge finder in the chuck, dial it in, grab the other end with a collet in the tailstock, and measure the offset along the top and side using a DTI or dial indicator.

Nice trick! ;-)

 

[dinc]

Google 'Rollie's dad's method'. You'll get a ton of information on lathe alignment and leveling.

 

[stangfish]

Running a lot of old machines every day I have heard a lot of good advice. Using a Starret 98 or something similar is your first step. Something I see as an indicator of the machines alignment or wear is if you indicate something in that is known to be straight and of same dimension the length of the material like a Piece of PSQ shaft material is where I see issues. With both the chuck end and the tailstock end indicated true to better than .001 Use the carriage to run the length of the shaft @ 12 and 9 o'clock. it should read zero all the way down. The shaft may sag a little. the horizontal position is the most critical. Then center the shaft and make up the live center. Repeat readings. Your tailstock might be adjustable horizontally if you need to make changes. If you want to know if you are facing true cut a large flat face and run an indicator al the way across using your cross slide.

 

[scotharr]

Google 'Rollie's dad's method'. You'll get a ton of information on lathe alignment and leveling.

This method should only be used for small hobby lathes that have no "proper way of adjusting headstock alignment. The Rollie Dad method is essentially twisting the lathe bed to get the Apron and headstock in alignment: not recommended. Here is how I got my lathe perfectly aligned in all dimensions.
1. Use a precision machinist level to ensure the lathe ways are level and untwisted.
2. Use a test bar and take readings along its length, adjusting the headstock directly to get it perfectly aligned with the lathe ways. Turn a few inches of bar stock and measure the diameter at each end to verify you have the alignment perfect. Most decent lathes have a way to pivot the headstock to get it perfectly aligned....this is much preferred to the Rollie Dad method which twist the ways.
3. Finally put a dial indicator on the headstock and rotate it around the tailstock to check tailstock alignment. I had to use shim stock to get the tailstock at the proper height and the adjustment screws to align the x-axis on the tailstock.

Hope that helps.

 

[dinc]

Thanks for the Rollies update.

 

[microsuck]

Just turn a 12" piece of round stock. Both ends should be the same diameter. If the tailstock end is larger, move it towards you. If its smaller, move it away. Repeat until both ends of the stock are the same diameter.

 

[dinc]

If you don't have a lot of sacrificial stock lying around get a 12" piece of all thread and center drill both ends. Put a washer between nuts on either end take cuts on the washers and follow microsuck's instructions.