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Mounting Eccentric Trees as 2 page pdf

Quick Change Chuck/Drive Center

Collet Chuck

I find that a collet chuck is the best method for small work of this sort.  It holds securely, even when only tightened by hand.  Its small size allows easy access to the headstock end of the project, and its smooth surfaces are hand and finger friendly.  Everyone should have one.

It is possible to precut stock using a jig and table saw or band saw so that it can be mounted directly in the chuck, but I prefer to turn a mounting tenon on the lathe as it takes less time than setting up a jig unless you're turning mass quantities.  But I don't like to constantly mount and dismount the chuck.  The solution was to make a safety-drive that would fit in the collet chuck.

Find a bolt that is the same size as the collet you normally use—I've made drives for the 1/2” and 3/4” collets.  Cut off the bolt about an inch behind the head.  Mount the bolt in the collet chuck. Select a drill that is about the size you want the rim of the safety drive to be—1/2” works fine.  Mount the drill bit in your drill chuck and drill into the bolt head until a cup is formed.

Select a smaller drill which is the same size as a pin or nail you have, and use the drill chuck to drill a hole into the center of the cup ~1/2” deep. Remove the drill chuck from the tailstock and select a fairly aggressive metal file.  Turn the lathe on at a slow speed and use the file to reshape the outside of the bolt head to complete the shape of the safety drive.

Remove the bolt from the collet chuck and clamp it to your drill press table.  Drill and tap for a set screw to hold the center point in place.  Cut your center point material to approximate length.  File a flat spot on the shaft so the set screw can grip securely.  Mount the center point in the safety drive, then mount the drive back in the collet chuck.  Turn on the lathe at a slow speed and use a file to shape a point on the center point.

[DFig01:  A home-made drive center for the collet chuck made from a 3/4” bolt.  The drive is quickly mountable and removable and has an adjustable center point.]

Number 1 Jaws

The # 1 Jaws for my Stronghold are a good size for holding this type of work, but the large chuck body obstructs access to the headstock end of the work and the sharp edges of the jaws can hurt your hands and tools.

You can buy a drive center to fit in the chuck so that the chuck doesn't have to be removed.  While it's perhaps designed for use with the #2 jaws it does work with the #1 jaws as well.  The drive I have is a four prong.  Nominally a 2 prong drive is better for eccentric mounting, but pine is soft enough that the 4 prong works fine.


[DFig02:  A four jaw chuck with #1 jaws and commercial drive center.]


I have a 2 prong center that extends past the end of the headstock Morse Taper by half an inch or so.  If you have a similar drive center, then mount it in the headstock and file the taper between the headstock and the prong base flat.  The drive center can now be held in the #1 jaws.  You could also use a drive center modified this way in a collet chuck with a 11/16” collet.


[DFig03:  After filing flat the part of a Morse Taper drive center that extends past the headstock.]




[DFig04:  With a section of the taper filed flat, the drive center can be securely held in #1 jaws.]

Limited Penetration Tailstocks

Modified Point

Most commercially available tailstock centers are sub-optimal for small work in soft wood because a cup center is to large and a point center tends to split the wood.  One way to solve this problem is to shape your own center with a finer point and flat area to limit penetration.  Old One-Way live centers use a tapered dowel pin as the center pin.  You can take the center to a well stocked hardware store and find a tapered dowel pin that fits and has the amount of extension you want.  Mount the new dowel pin in the tailstock and then mount the tailstock in your headstock.  Find a rod or nail about the diameter of the tailstock knockout pin and insert it in the live center cross hole to lock the tailstock.  Tape the pin in place.  Turn on the lathe at a slow speed and file the point however you like.


[DFig05:  After filing a tapered dowel pin into a limited penetration center.]

Newer One-Way tailstocks use a #0 Morse Taper as the center pin.  You can do the same thing if you can find a suitable pin.  Some internet searching about convinced me it would be easier to make your own pin.  Chuck up 3/8” rod somehow on your lathe and have at it with a file until it matches the taper of the pin that came with the chuck.  Then mount the new pin in the tailstock center and shape the point.


A decidedly lower tech solution is to use a regular V-point tailstock and a small washer.  The washer will prevent the center from penetrating to far.  If you get tired of chasing it across the shop you can temporarily glue it in place with CA glue.


[DFig06:  Using a small washer to prevent the tailstock from penetrating too far and splitting the soft pine.]