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My lathe headstock has adjustable bearings and I have it set so that the headstock and tailstock centers touch, but I'd like to check it over the length of the bed. I've never been able to find anything made for that purpose. Asking here if anyone has devised a method for checking centers and parallelism.

Being an engineer I tend to get anal about such things... I'm thinking of maybe a laser mounted in a #2MT.. just can't find one.

Thoughts?
 

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I'm not an engineer but have wondered the same thing. I have been thinking along the same lines with a laser mounted in the tailstock but haven't come up with anything that I thought was noteworthy.

However, happened to see this http://www.executivegiftshoppe.com/ls-2210b.html?gclid=CJC03sfs6bkCFUdo7AodXCMAsg in a search and wondered if it would work if mounted in a piece of wood turned to a MT2.

Just a thought.
 

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If they line up at the head stock they should be in alignment the length of the bed. Unless there is a problem with the ways or bed along its length.
 

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I agree with preach and I also wouldnt worry about it. Check the bed with a straight edge if you must.

The closest thing I can think of to what your looking for is a bore sighter for sighting scopes on a gun. They typically come with several differeny adapters to fit differnt calibers of guns. I would think maybe one of the ones for a shotgun might fight. Just do a google search for laser bore sight.
 

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Do an internet search for laser bore sight or similar string.

I recall seeing a post on some forum, not this one, where the laser sight was designed to be mounted in a drill chuck for determining run out of the chuck.

If you get one, you may also be able to tell if the headstock has any run out compared to the tailstock at the end of the lathe.
 

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Just because the points touch does not mean they are aligned. Either one could be unparallel to the bed left and right or up and down. Been discussing this problem with a master machinist. Haven't come up with a way to really check. I tried an inexpensive laser bore sight and not sure it told me anything. I build an adaptor to fit the headstock. It traces a small circle just a little off center on the tailcenter but that doesn't tell me if my homemade adaptor is off, the headstock is off or the bore sight is not dead on.
It all started because I have a problem when I'm threading boxes. Adjust the cutter until it just touches the wood. Then rotate the box against the cutter. I usually have to move the cutter any where from .008 to .012" before it touches the wood all the way around. My threader is absolutely dead on accurate as checked by this machinist. We think the problem is the headstock is not dead on, the chucks aren't dead on, or the mating surface of the chuck is either dirty or not dead on.
When you stop to think about it these aren't metal lathes so every one of the above is probably off just a hair. Not a problem for 99 percent of all we do on the lathe but every now and then (like my problem) something creaps up.
 

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My lathe headstock has adjustable bearings and I have it set so that the headstock and tailstock centers touch, but I'd like to check it over the length of the bed. I've never been able to find anything made for that purpose. Asking here if anyone has devised a method for checking centers and parallelism.

Being an engineer I tend to get anal about such things... I'm thinking of maybe a laser mounted in a #2MT.. just can't find one.

Thoughts?
If you are concerned about parallel-ness of the head and tail stock, I assume you are turning a spindle. A drive spur and live center are essentially ball joints, meaning that as long they don't wobble they are points and only one line can be drawn between two points making the question of 'how parallel are they' moot.

Regards,
Steve
 

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they are points and only one line can be drawn between two points making the question of 'how parallel are they' moot.
I agree with Steve. At 24" out it doesn't matter if the points are off by 1/4". You are cutting by how you place the banjo and tool rest by hand anyway.
 

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My needs for headstock and tailstock to be centred are for drilling such as pepper mills, wood vases.

If the headstock and tailstock are not centred the drilled hole will be larger and not consistent. Been there, fought with that. :thumbdown:
 

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If your headstock and tailstock are not aligned, any spindle turned between them is not going to be round as it would be just like turning on multi-axis.
 

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If your headstock and tailstock are not aligned, any spindle turned between them is not going to be round as it would be just like turning on multi-axis.
How can it not be round? It can be tapered from one end to the other, but it can't be out of round at any given point.

Get a piece of aluminum round stock and have a machinist center drill both ends, and check concentricity between centers. Mount this between centers on your lathe, then measure between the bar and the bed at various points. Use a pretty hefty piece of stock so it doesn't sag under it's own weight.
 

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Discussion Starter · #16 ·
My avitar is a picture of my lathe. Bed, legs and tailstock are cast iron by Oliver. The headstock is home made (original was lost in a fire). The 1-1/2" spindle is supported by two flange bearings on each end of a steel and plywood box.

Turning spindles between centers is very forgiving, as mentioned above. A spur center can handle that. The problem comes when you try to hold one end of a spindle in a chuck and drill a hole in the other end.

Just because the points touch does not mean they are aligned. Either one could be unparallel to the bed left and right or up and down. Been discussing this problem with a master machinist. Haven't come up with a way to really check. I tried an inexpensive laser bore sight and not sure it told me anything. I build an adaptor to fit the headstock. It traces a small circle just a little off center on the tailcenter but that doesn't tell me if my homemade adaptor is off, the headstock is off or the bore sight is not dead on.
Roger that. I have a bore sight checker for .45 ACP and have considered using it for this, but as you said you dunno if it's the chuck, fixture, or headstock if it doesn'tline up.

Why not use this http://www.novatoolsusa.com/NOVA-Acruline-System-2MTNA.htm If the bed is flat and straight than the remainder of the lathe is aligned.
Thanks, Bob. That's a clever idea.. a piece of steel with a #2 MT at both ends. The lathe's bed is flat, and I trust Oliver that the tailstock is dead on. I'll buy one of those Nova thingies.
 

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The problem comes when you try to hold one end of a spindle in a chuck and drill a hole in the other end.
Also if you need to flip a spindle piece end for end, e.g., to finish the headstock end since better access at the tailstock end.

If the headstock and tailstock are not aligned ad you flip, the piece will not be true. Another case which had me scratching my head until I realised the alignment was the issue.

In my case the problem happened after I had pivoted the head, then reset and foolishly assumed the detent would be accurate. Close, but needs checking to tweak the alignment before locking down the head.
 

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My needs for headstock and tailstock to be centred are for drilling such as pepper mills, wood vases ...
... in my case, making fountain pens without using kits. A typical pen barrel is made by drilling a hole in a piece of acrylic with an 8.25mm drill bit and threading it with a 9mm x 0.75 tap (drilling and tapping for the nib & feed can be even tighter tolerances.)

Any misalignment between the head and tail stocks results in a very sloppy fit.

(The Nova "Acruline" double-ended MT2 has helped enormously.)
 

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