Offset key for Sherline Lathe Headstock - need one made

Forty Niner,

Considering my level of knowledge and experience in machining, perhaps it would have been more accurate for me to have specified "some kind of boring tool" instead of an end-mill. ;-) OK, an end mill is the wrong tool.

I think that you are correct in recommending that I keep my expectations of the lathe commensurate with its price.

I have not seen how an adjustable tailstock is adjusted on a lathe that has one. Your backside locking screw adds adjustability for turning between centers. Perhaps that is enough. Satis est, in Latin.

Tozguy,

My main idea behind boring the tailstock ID is to eliminate/reduce any radial and axial misalignment of the tailstock ID. If one could accomplish boring it to be parallel with the ways, then perhaps a tight-fitting spindle would result in a tailstock that is more aligned than original.

If (big if) one would could bore the tailstock ID to be parallel with the ways, then one could order a new spindle with the right OD from Sherline.

This idea of boring the tailstock ID to align it reminds me of rotating a photo slightly in Photoshop to level it.

Karl
 
Karl A said:
That backside locking screw is a clever addition to the tailstock, Forty Niner.

I have a Sherline 4400, and I am a beginner to machining. This thread has gotten me asking myself what necessary function the tailstock serves. Is the only necessary function to provide a center? Can drilling, reaming, and threading-an-ID-using-a-tap be done as well or better from the cross slide? I think that the answer is no for a long piece that requires the support of a steady rest (mounted on the cross slide).

I examined the tailstock on my lathe today, to see the effect of adding a locking screw on the backside. I was struck by how much play there is between the tailstock spindle and the tailstock case. It's a disconcertingly loose fit.

Sherline says here that each tailstock spindle is individually ground to fit each tailstock case:

Tailstock Spindle – Sherline Products

www.sherline.com www.sherline.com
In ordering a new spindle, one can specify the OD. The default is 0.618-0.619".

Would the following idea work to align a tailstock with the headstock?
1. Order a tailstock spindle with an oversize OD.
2. Align the headstock very well with the ways.
3. Mount an endmill at the headstock that matches the OD of the new tailstock spindle for a nice fit.
4. Mount the tailstock to the left of the cross slide. Adjust the tailstock gib tight and evenly.
5. Feed the tailstock onto the spinning endmill.
6. Install the new tailstock spindle.
Click to expand...

Have you considered using one of Sherline's adjustable tailstock adapters?

Tailstock Tools – Sherline Products

www.sherline.com www.sherline.com

These are very effective and will provide very precise adjustment of the tailstock center.

Bill
 
Yes. I ordered an adjustable bullnose center after I had drilled and reemed two lengths of 1-1/8" dia. Delrin stock to 14mm ID, for wheel hubs. The bores turned out visibly off center. Fortunately, I needed to reduce the OD. With the adjustable bullnose center, i was able to obtain an adequately concentric hubs. The wheels in my chocolate refiner turn evenly.
 
[QUOTE="Tozguy, post: 762139, member:
...
I always prefer to turn an OD to get a close fit rather than the opposite. If you start with a new oversized spindle then why not turn it to fit the bore in the tail stock? You would have to make tight fitting extensions for both ends of the new spindle. To turn between centers you would have to have a way to align the original spindle. Or use a four jaw chuck and steady rest.
[/QUOTE]
Tozguy,
Your suggestion of turning a new oversize spindle to fit the bore in the tailstock has given me another idea for lessening tailstock misalignment: Mount the spindle, for turning, with a horizontal offset that is opposite of the existing tailstock horizontal misalignment. The idea is to eliminate offset with offset, or: If you can't beat them, join them.
Karl
 
Quite frankly, the non-adjustable tailstock is the most glaring deficiency on a Sherline lathe. You would think that after decades of existence they would have figured out how to make the tailstock at least laterally adjustable for alignment. Instead, they spent their time making adjustable things that go into the off center tailstock. Not only are these things time consuming to adjust, the fact that they are adjustable means that they can move under load while in use.

Add to this the fact that the Morse taper inside the ram may or may not be all that accurate. If accurate, it will not remain that way due to wear over time. I used this wear to align my live center to offset my tailstock misalignment so it actually helped me but that inaccuracy is there. Is it enough to matter? For most things, probably not. For precision turning of longer work pieces, yes, I think so.

My suggestion is to use a good test bar and find out how much your tailstock is really off by. Then using the live center you usually use, index it in the tailstock ram and do trials to see if there is a position that minimizes the offset. It may surprise you to find that between the non-perfection of the live center taper and the tailstock taper, there may just be a position that gives you acceptable run out. I did this with my shop-made live center and it resolved run out completely in both the horizontal and vertical directions. Maybe I just got lucky but maybe not ...

The only other option really is to make an adjustable base. Luiz Ally did this on Youtube so I know its possible.
 
The tailstock of my lathe is misaligned 0.0044" to the rear. My live center is the Sherline adjustable one; unfortunately, it has 0.001" total indicated runout.

Can the runout of the Sherline live center be improved by replacing its bearing with a higher quality bearing?

For me, the sigificant misalignment of the tailstock is like an itch that I want to scratch. It's also a fun puzzle. I am a beginner to machining and I am still getting my lathe and mill set up and equipped, though. For now, I think it's better for me to use the adjustable tailstock tools.
 
Is the following a feature or a defect in my tailstock? As I turn the tailstock handwheel to advance the spindle to the left, I have to keep loosening the spindle lock screw. Diagnosis: I found that the depth of the groove in the spindle gradually decreases from left to right.

It's happened that while drilling, I thought that the drill was encountering significant resistance to advancing when it fact the spindle lock screw required loosening.
 
Pull the spindle out and mill the groove flat. It should not taper like that.
 
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