Off Centered

[texasfootball21]

I just turned my first pen by turning between centers, a Jr. Gent in mesquite. I switched over from the mandrel largely because my work was often out of round (OOR). I finished turning the blank down and took it off, it is way off centered! It may be worse then when I used a mandrel. I am pretty frustrated and want to know why it is so OOR before I turn anything else.

My guess is that it may be low quality bushings. What could I do about this? I am going to buy from bushings from John when he gets everything up and running but until then I don't know what to do. Another possible solution may be to turn without bushings, and use a caliper. I've never used a caliper before but this may be my only option.

Anyone have any tips?

 

[MobilMan]

If the bushings were the only problem, you'd have the same thing [as bad] using the mandrel. Do the points on the live/dead centers mate? Could one or the other not be turning true? Spin it up & check both. Could there be some glue or something stuck to one of them, knocking it off center? Bound to be something obvious. Hopefully. Is the blank half light wood & half dark? Hard/soft?

 

[Rudy Vey]

Make sure the blanks are absolutely squared to the bushings!! Try to use bushings that are made for mandrel-less turning - tighter tolerances.

 

[hunter-27]

Just a guess, but I would rule out the bushings, I'd say you have a lathe alignment issue.

 

[texasfootball21]

I am pretty sure the lathe is aligned well, I will go double check in a little bit. Maybe it isn't the bushings, and if its not an alignment issue, then what could it be? The problem was also bad on the mandrel which makes me think about the bushings. Anyone else thinking someone different?

 

[smitty]

My guess would be the bushings. If you have a Beall collect chuck and center drill you might try to recenter the bushings. I do this to all my bushing that I use for between center turning. I also make all my own bushings on my mini metal lathe if you need any made please let me know.

 

[rherrell]

I agree with Rudy, almost. The end of the blank needs to be perfectly square with the TUBE. A sloppy fit on your pen mill OR a pen mill head that's a bit off will screw you up.
I use a pen mill to take off the majority of the wood but I leave the last 1/32" for my blank squaring jig..........

I swear by this little dude. Jay Pickens has a tutorial in the library on how to make something similar.

 

[leehljp]

Generally, the causes are:
1. Off Centered bushing holes or Off Centered bushing shoulders
2. Tail Stock and head stock not in alignment
3. Loose bushings as they fit into the tubes
4. Dirt, glue or dust in the tail stock or head stock "housing" where the drive center or live center's MT x shanks fit.
5. Unsquared blanks along with slightly loose bushings.

 

[texasfootball21]

Maybe it is a problem with squaring the blank, wouldn't have thought of that.

I use a pen mill, I do not have a bench sander(don't know the real name) anymore so I cannot make a jig like the one above. The largest shaft I have with my mill is 10mm, which is obviously too small for the 10.5 and 12.5mm tubes. How do you guys mill with the shaft being too small?

Thanks.

 

[davinci27]

I make a sleeve out of various tubes. The larges shafft I have is a 7mm. I take 7mm tubes and glue them to a scrap blank. Then I turn it down until it just fits into the larger tube. Then when I need to square the bigger blank, I just put the sleeve on the 7mm shaft and I have a nice square blank. Be sure to cut you sleeve so they are the same length, or just bit shorter than the blank you are squaring.

Ben