Detecting out of round

[Tiger]

I reviewed a couple of my recent pens and found that they were slightly out of round. Of course i had already assembled the pens but am wondering whether i could have detected the out of round while i was turning. I turn between centres but possibly there was some muck in the headstock morse taper or one of the paper shims on the tailstock moved anyway would be nice to know while turning that something is wrong rather than finding out after you've assembled.

 

[smik]

Tiger - One idea once you turn to round but still with stock to remove, take the piece out and check. Can't think of anything simpler at this time.

 

[TonyL]

Since I started TBC, I have not had the issue. HOWEVER, I recently started rotating my bushings about half-way through my finishing-turning, just to be on the safe side. I believe Barry Gross advised the same, but I have only seen him turn on a mandrel one barrel at a time. Again, since TBC, no OOR issues. I don't know if this will help.

 

[ed4copies]

If a blank is completely round, you can rotate it on your mandrel (or your centers) and it will not "wobble". You continue to cut on all points.

If it is even slightly out of round, you will have a wobble, when the blank is moved, relative to the bushings, or centers if you are not using bushings.

 

[rd_ab_penman]

TBC without bushings resolves all OoR issues.
Works for me.

Les

 

[1080Wayne]

TBC without bushings resolves all OoR issues.
Works for me.

Les

Not quite . Misalignment of the head and tailstocks will still cause it , as will local variations in hardness of the piece being turned .

 

[KenV]

TBC without bushings resolves all OoR issues.
Works for me.

Les

Not quite . Misalignment of the head and tailstocks will still cause it , as will local variations in hardness of the piece being turned .

May I suggest that the cause is more the preparation and end of the blanks than any issues with alignment of headstock and tailstock when turning between centers unless headstock and tailstock are really grossly out of alignment. Cocked (misaligned) bushings are the outcome of less than precise preparation. That is the predominate reason that Les Elm is spot on with his observation -- it minimizes the effects of less careful blank preparation.

Difference in density is handled by very sharp tools and careful tool use. Failing, fall apart spalted wood may be a special case, but sharp high speed steel and shearing cuts will succeed in variable density woods.

 

[mredburn]

Well........... IF you went to extremes you could buy a magnetic base and dial test indicator and check them that way. I have one that measure from 0-.004 by .0001 increments that I use to dial in my chucks. Although if you were lazy you could just get one that measures 0-1 inch in .001 increments.:biggrin::biggrin:

 

[Dave Turner]

It's assumed that you have aligned your headstock and tailstock. If your 45 degree cone drive and tailstock active cone center are of decent quality and the Morse tapers are clean, then you should be able to achieve precision roundness when turning between centers.

I never use bushings for my final turning because they will often introduce an unacceptable out of roundness. They also make it more difficult for me to measure the end diameters with my calipers, since I always turn to a desired measurement and not the bushing.

As was pointed out, it is critical that the brass tubes be clean at the ends. To this end, I will always use a deburring tool on the ends of the brass tube before final turning. That, together with a wire brush will ensure that the brass tube seats completely on the supporting cones and eliminates out of roundness (assuming your tube was round to begin with - I always check mine before using by taking several measurements with calipers).

 

[SteveG]

The deburring tool is an essential item in my shop. Recently found it available at Home Depot in the plumbing dept. Price: about $5, with extra 'bit' inside the handle.

 

[Ironwood]

I use one of these to clean up the ends of my tubes before I start turning. Takes the high spots off, and you can use the side like a scraper to scrape any spots of glue left inside the tube.
Tapered Reamer : CARBA-TEC

 

[Tiger]

Thanks for those suggestions. I have also found that I've had a small amount of CA on the dead centre which also throws things out. I have a deburring tool, i use it at the end to help with pen assembly.