Turning gone wrong - off center

[pauly99]

From the picture you can see the turning somehow did not go straight. Thin on one side and thick on the other. How might this happen? I drilled on the lathe and it seemed to be straight and I also turned between centers on this acrylic. I'm guessing this blank will be a throw away. How can I prevent this from happening in the future?

 

[Rodnall]

Check your bushings.

 

[pauly99]

The bushings were brand new... never used before.

 

[jmbaker79]

Check the bushings still, sometimes they are out of round, or not drilled straight or centered. Perhaps put it back between center with no bushings, fix the out of roundness issue and build it back up with CA if need be to hit the correct size.

 

[jimm1]

Another possibility is that you may have "squeezed" the mandrel too much when securing your tail stock. The mandrel may have "bowed" ever so slightly.

What about the mandrel nut? That could also sqeeze your tubes too much between the bushings.

 

[KenV]

You can get out of round with turning between centers.

Causes can be

Debris in the morse tapers that prevent the centers from seating evenly.

Blanks not square and clean

Debris/ finish at the face of the TBC bushings

Loose fit when sanding or uneven sanding from too much force on the abrasive.

 

[pauly99]

Another possibility is that you may have "squeezed" the mandrel too much when securing your tail stock. The mandrel may have "bowed" ever so slightly.

What about the mandrel nut? That could also sqeeze your tubes too much between the bushings.

Jim, I was using TBC so there was no mandrel. I just checked the bushings and they are fine but I think I may have found the culprit. The tailstock has some left right play and when I tighten the tailstock it can be in a couple of different positions which I believe would make this off center problem? So my next question would be how to fix this left right play on a Harbor Freight 8"x12" lathe.

 

[KenV]

Paul -- my lots fancier lath is not locked tight to the ways either. Wood lathes are almost always registered to the inside of the ways, where metal lathes are registered (quite precisely) to the outside of the ways.

I did some checking by putting a laser bore sighting device into my collet chuck and looking at the alignment at the distance for some spindle work. It was pretty close but varied about 1/16th inch. I found that by pushing away at the tail stock ram I was consistent.

TBC is akin to spindle turning and there is ability of the centers for flex just a bit. Consistent one way or another will provide repeatable results. Tail stock in the ways is very unlikely unless the whole alignment of the tail stock is canted out of parallel with the ways.

My bet is a piece of debris in the taper -- seen that happen before - especially in the head stock with drilling debris.

 

[pauly99]

TBC is akin to spindle turning and there is ability of the centers for flex just a bit. Consistent one way or another will provide repeatable results. Tail stock in the ways is very unlikely unless the whole alignment of the tail stock is canted out of parallel with the ways.

My bet is a piece of debris in the taper -- seen that happen before - especially in the head stock with drilling debris.

Ken, I'll check for debris because that may be a possibility. Not to harp on it but I did notice that depending on how I pulled in the tailstock, sometimes I would tighten it and it would be straight on and the next time (like you said) it could be off 1/16 of an inch.

Once I locked down the tailstock, I did turn it to bring it forward a bit because otherwise the blank wasn't spinning very well between the bushings. Once tightened (by turning the tailstock) the blank spun fine.

 

[thewishman]

Stop a couple of times when getting close to the finished size and rotate each bushing a 1/4 turn in opposite directions. Do it once more just before sanding. That should eliminate most of the out of round.

 

[pauly99]

Stop a couple of times when getting close to the finished size and rotate each bushing a 1/4 turn in opposite directions. Do it once more just before sanding. That should eliminate most of the out of round.

I'm taking all of these tips to heart. Luckily on this Wall Street II Pen/Stylus, I have the other half of the blank left and was able to punch out the stylus end with no problem. I'll make sure the headstock, tailstock, and dead and live centers are clean, move the tailstock so it lines up with the headstock so it isn't off by 1/16th of an inch, not tighten the tailstock too much, and rotate the bushings a few times as I'm getting closer to finishing the blank and sanding. Learning here folks... Slow at times but I'm learning and thank you very much for the responses.

 

[bwftex]

I have a HF 10x18 that I've had for some time now. The tail stock has a little slop. When I first got it I tightened the nut under the tail stock just a bit so it would still travel smooth. That helped to keep the tail stock snug and firmly in place when turning. Using the centers that came with the lathe I ran the tail stock all the way up until the points just touched. I found that they were only off just the very slightest amount if I pushed the tail stock firm against the far side of the way. The tail stock was then tightened down and I loosen up the four hex bolts on the head stock a little and taped it with rubber mallet until the alignment was perfect. When I started turning pens i got a mandrel with a mandrel saver. As long as I kept the the tail stock firm against the way when sliding it the mandrel saver went over the mandrel smoothly with no bump. Keeping the tail stock firm against the way while tightening it down always keeps it lined up just right and the pen blanks turn perfectly. One day I did a piece of antler and it turned out much like the blank in your picture. I checked out the head stock and tail stock alignment and sure enough the headstock needed a little adjustment just like it did in the beginning. Don't know if your problem could be similar or not but it a very easy thing to check and adjust if it is.

 

[ed4copies]

Although Chris' (Wishman) suggestion will work, kind of, it will slow you down and it is NOT a solution to the real problem.

Another possibility, if I am reading your question correctly, would be "left over glue" in you pen tube. This would keep one spot from seating on your 60 center (either head or tail) and make the pen OOR. If you rotate the pen blank and the problem does NOT change, it is probably glue in the tube.


FWIW

 

[Hendu3270]

Maybe it's just me, but when I look at the photo, it looks like the blank was drilled with the wrong drill bit and you attempted to use extra glue to "fill" the space between the blank and the tube? Again, I may be seeing something in the photo that isn't actually there. If this is the case though, when the glue has set and dried, and the tube is not perfectly aligned in the drilled hole, this is the outcome I would expect.

Both ends of the tube are this way? are they off on the opposite sides of the blank?

 

[Dale Allen]

Here's a quick and easy way to check the alignment on the centers for TBC.
Note that this is best done using either a magnifier headset or lighted mag lamp so the minute differences can more easily be seen.
When I did this I was not aware that the headstock needed a 'bump'.
Using 2 small magnets I set a steel rule along the opposing sides of the centers(they have to both be 60 degree). you will need to tape the live center so it does not rotate. Viewing this close up you will be able to see if the sides of the ruler are not laying flat on both centers. You cannot see it very well in this picture but mine was off. So, as I have to do often on this HF lathe, I smack the bottom edge of the headstock with a rubber hammer and you can see that it moved it back to alignment. It is a situation I have just had to deal with along with the fact that the tailstock must be pushed away from me when tightening.
Having these centers out of alignment is what may be causing your problem. As you can imagine, the tube end is keeping the bushing from trying to adjust to the mis-alignment of the center. That causes the bushing to ride heavy on one side of the center and all kinds of bad things happen.

 

[pauly99]

Maybe it's just me, but when I look at the photo, it looks like the blank was drilled with the wrong drill bit and you attempted to use extra glue to "fill" the space between the blank and the tube? Again, I may be seeing something in the photo that isn't actually there. If this is the case though, when the glue has set and dried, and the tube is not perfectly aligned in the drilled hole, this is the outcome I would expect.

Both ends of the tube are this way? are they off on the opposite sides of the blank?

Chris, I drilled with the 27/64 as called for in the kit. If you are referring to the black part in the picture, it is the brasso that I was using before the carnauba wax. The out of round was on both sides of the blank.

 

[pauly99]

I have a HF 10x18 that I've had for some time now. The tail stock has a little slop. When I first got it I tightened the nut under the tail stock just a bit so it would still travel smooth. That helped to keep the tail stock snug and firmly in place when turning. Using the centers that came with the lathe I ran the tail stock all the way up until the points just touched. I found that they were only off just the very slightest amount if I pushed the tail stock firm against the far side of the way. The tail stock was then tightened down and I loosen up the four hex bolts on the head stock a little and taped it with rubber mallet until the alignment was perfect. When I started turning pens i got a mandrel with a mandrel saver. As long as I kept the the tail stock firm against the way when sliding it the mandrel saver went over the mandrel smoothly with no bump. Keeping the tail stock firm against the way while tightening it down always keeps it lined up just right and the pen blanks turn perfectly. One day I did a piece of antler and it turned out much like the blank in your picture. I checked out the head stock and tail stock alignment and sure enough the headstock needed a little adjustment just like it did in the beginning. Don't know if your problem could be similar or not but it a very easy thing to check and adjust if it is.

Like you, I just (as in after I started this thread) tightened the nut under the tailstock on my HF 10x18 lathe and this only seemed to tighten the back and forth of the tailstock along the way. I was surprised to find there doesn't seem to be another way to fix the play in the tailstock. When I tighten the tailstock as is and bring the live center to the dead center, it is off by maybe 1/16th of an inch. When I push the other way (against the tailstock) I'm guessing that the difference is more like 1/64th of an inch. So unless suggested otherwise, I will slightly adjust the headstock to get rid of that 1/64th of an inch, although I think I would be better to make sure that if I do so that I am hitting the center of the blank after all is said and done.

 

[Hendu3270]

Maybe it's just me, but when I look at the photo, it looks like the blank was drilled with the wrong drill bit and you attempted to use extra glue to "fill" the space between the blank and the tube? Again, I may be seeing something in the photo that isn't actually there. If this is the case though, when the glue has set and dried, and the tube is not perfectly aligned in the drilled hole, this is the outcome I would expect.

Both ends of the tube are this way? are they off on the opposite sides of the blank?

Chris, I drilled with the 27/64 as called for in the kit. If you are referring to the black part in the picture, it is the brasso that I was using before the carnauba wax. The out of round was on both sides of the blank.

I gotcha. That IS the right bit, as I turned one today as well.

 

[pauly99]

Dale, thank you for the pictures. That is exactly what I intend to do.

and now after ever so slightly moving the headstock it is much better centered than it was before.

 

[Dale Allen]

That looks good to me. I am assuming that is looking on from the top.
That is the direction I took the pictures from. It must also be aligned vertically. I spent many hours shimming mine to get that corrected.
Also, it is possible to have the center points exactly meet but the linear plane of the centers be off. That would still create problems.

 

[pauly99]

That looks good to me. I am assuming that is looking on from the top.
That is the direction I took the pictures from. It must also be aligned vertically. I spent many hours shimming mine to get that corrected.
Also, it is possible to have the center points exactly meet but the linear plane of the centers be off. That would still create problems.

I will check the vertical as well and shim if necessary but I believe all looks good now

It was a good idea to check if there was glue inside the tubes but that was not the case. However I was reminded about leftover shavings after drilling and making sure to check the tapers to ensure everything is clean. I did find out after my most recent drilling of the acrylic blank that shavings did make it into the headstock (excuse my lack of knowledge of exact lathe terminology) after using the PSI pen blank drilling chuck. I will have to make it a habit of checking these items before starting my next pen.

 

[Tom T]

Paul,
I spent two hours on the phone with powermatic on the same problem. They were very nice and we checked all the things mentioned already. All was in alinement, I use the PSI pen saver mandrel. Works very well have done many pens on it. I am looking for bushing to go to TBC.
They carefully told me that it was me and not the machine. They were kind. The issue was my roughing gouge, which is what I use was a little dull. They had me sharpen it up and had me make very light cut by turning my wrist to engage the acrylic. After a few minutes the blank became round. Basically I had pushed it out of round and it will stay that way as long as I keep my tool against the pen blank. It was not until, as they said, I cut so lightly I made a fine cut that made flower, not a ribbon of acrylic. As I said it became round again. I guess I was to much in a hurry and was pushing hard to get the cut. Since then all has been well, good round pens. I do lots of euros and had the same issue with the tenon. It was some times out of round, because my parting tool was not as sharp as it should have been. I would rather turn than sharpen. I hope that helps.
Tom