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Accurately Locating a Center Hole (Read 270 times)
 
Don Stephan
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Accurately Locating a Center Hole
Dec 3rd, 2017 at 10:28am
 
Sometimes, after turning a spindle and cutting or parting the ends to final length, it is necessary to mount in the lathe again.  With a more uniformly dense wood like maple or walnut it usually is easy to exactly position a divot with an awl or small drill bit.  With oak and the current project, cypress, the needed center point almost always seems to fall on the boundary between softer early season growth and harder late season growth, pushing the awl or small drill bit off the mark.  If I had a large negative cone adapter for the live center and a sufficiently small diameter spindle end, that might work for one end of the spindle but not both.  And this would not allow work on the very end of the spindle.

Has anyone yet solved this challenge.
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Ed Weber
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Re: Accurately Locating a Center Hole
Reply #1 - Dec 4th, 2017 at 10:42am
 
I use Multimedia File Viewing and Clickable Links are available for Registered Members only!!  You need to Login or Register
Sloan Dowel Center Marker/Center Finder
You do need to turn your spindle to one of the 9 sizes on the plate but it has been helpful at times.
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robo_hippy
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Re: Accurately Locating a Center Hole
Reply #2 - Dec 4th, 2017 at 11:38am
 
I don't think it is possible to remount any blank perfectly. Mostly you can get pretty close, but they always seem to be off by a tiny bit. I haven't used one of the cup centers much, but they would position it pretty close, then if you take the cup off and replace it with a live center of some sort, it just never seems to remount perfectly. That is why I rough turn if I have to reposition a piece, then after all is set, do the finish turning without taking it off the lathe again.

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Don Stephan
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Re: Accurately Locating a Center Hole
Reply #3 - Dec 4th, 2017 at 7:51pm
 
The Sloan Center Marker reminded me of a center finder I bought perhaps 20 years ago and never used.  It is metal, the sides form a right angle and there is a sharpened blade running out at a 45 deg angle from the corner of the sides.  I'll have to see if I can find it and give it a try.  The point of a spur center or live center might stay more centered at the intersection of two or three shallow cuts across the end.

Agree completely Reed.  Made a gauge clock with a 1 1/2" wide slot, foolishly though if I turned a tenon to almost fit in the slot it would be a snug fit in a 1 1/2" forstner bit hole.  Hahahahahahaha!  Had to cut thin strips of the same wood, split off 1/16" wide pieces, glue them around the tenon, remount the piece and gradually sneak up on a tight fit with (gasp) a skew.
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Re: Accurately Locating a Center Hole
Reply #4 - Dec 5th, 2017 at 9:30am
 
Remember, wood moves.
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Mike Mills
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Re: Accurately Locating a Center Hole
Reply #5 - Dec 5th, 2017 at 10:33am
 
The Nova live center comes with a reversible cone for the their center. Using the "threaded insert" it can also be use in the headstock.
I'm sure there are youtubes for cutting a morse taper... pretty easy.
You would need two. Cut the tapers to fit your lathe on blocks of wood.
Drive: Install in the headstock and turn round with tailstock support. Then remove the tailstock and cut the cone to the size you want.
Live: Do the same but you will need more wood (length). After cutting as above remove the MT. Hold the cone in chuck jaws and hollow just enough to slip over your live center (maybe 1.5" wide and 1" deep).
This still will not allow work on the very end of the spindle.
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« Last Edit: Dec 5th, 2017 at 10:34am by Mike Mills »  

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Ed Weber
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Re: Accurately Locating a Center Hole
Reply #6 - Dec 5th, 2017 at 11:26am
 
Mike Mills wrote on Dec 5th, 2017 at 10:33am:
The Nova live center comes with a reversible cone for the their center.  Using the "threaded insert" it can also be use in the headstock.
I'm sure there are youtubes for cutting a morse taper... pretty easy.
You would need two.  Cut the tapers to fit your lathe on blocks of wood.
Drive: Install in the headstock and turn round with tailstock support.  Then remove the tailstock and cut the cone to the size you want.
Live:  Do the same but you will need more wood (length).  After cutting as above remove the MT.  Hold the cone in chuck jaws and hollow just enough to slip over your live center (maybe 1.5" wide and 1" deep).
This still will not allow work on the very end of the spindle.


Mike, I know all that makes sense in your head but i think a photo would help the rest of us. I'm pretty sure I know what you're getting at although the main issue from the OP was how to re-center AND be able to work on the end of the spindle.
Don Stephan wrote on Dec 3rd, 2017 at 10:28am:
And this would not allow work on the very end of the spindle.


Has anyone yet solved this challenge.

While I don't like to suggest things that have large changes to peoples method of work (people don't like that) I would offer this "solution"
The one way that comes to mind as of now would be to drill a small pilot hole into the end of the spindle. This only needs ot be deep enough to allow for truing up the end and still be present for re-mounting. I would think a 1/16" or 3/32" hole would be large enough.
This would need to be done before any turning begins


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Jennifer Hasan
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Re: Accurately Locating a Center Hole
Reply #7 - Dec 5th, 2017 at 11:48am
 
I use the Veritas Center Marker with good results.
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Mike Mills
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Re: Accurately Locating a Center Hole
Reply #8 - Dec 5th, 2017 at 7:50pm
 
Ed, as normal I did not interpret it correctly. I thought the "work on both ends" was an add on to the main problem on not finding the center.
I do not have pics but maybe this will help.
I have seen videos of making a morse taper jig but can not find them.
This pdf show how to make one. You would need to make two morse tapers, one for the headstock and one for the tailstock.
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Once the moris tapers are made insert the one for the headstock and turn the reverse cone in the wood extending. You now have a friction drive for the headstock.

For the tailstock you will need a bit longer piece of work but turn the taper and reverse cone as in the first. Then reverse and hold the reverse cone end in you chuck and part off or cut off the morse taper.
Now turn a recess to fit over your tailstock live center as shown in the video starting about 3:00.
You now have two reverse cones which should center any round or equal sided work (square, hex, octagon,..).
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I have no idea how you can work on the very end of the spindle no matter how it is held. The only thing I can suggest is to make sure of the final length and leave enough for the cones before cutting them to length.

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Ed Weber
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Re: Accurately Locating a Center Hole
Reply #9 - Dec 5th, 2017 at 10:27pm
 
Thanks Mike, I confess I got a little confused with the first post.
I've been guilty of doing the same thing, makes sense to me  Roll Eyes
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Don Stephan
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Re: Accurately Locating a Center Hole
Reply #10 - Dec 6th, 2017 at 8:07pm
 
Probably Reed is correct - don't turn an overly long tenon at the end of a spindle planning to cut the tenon to length for assembly.  My tenons were 1 1/2" and 1 1/4" so I could have used a Steb drive center and cone/point live center and carried the tenon to the very ends.  Then I could have test fit and remounted as necessary to get a tight final assembly.
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Re: Accurately Locating a Center Hole
Reply #11 - Dec 7th, 2017 at 8:07am
 
Jennifer Hasan wrote on Dec 5th, 2017 at 11:48am:
I use the Veritas Center Marker with good results.

I use something very similar
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