Pepper mill concentricity?

[alex grams]

I made a few pepper and salt mills for christmas gifts, yet I am having a hard time getting perfect concentricity of the head and body. Per the instructions:

Turn rough blank, cut tenon, part the two pieces, them mount the head by the tenon and drill a hole from tailstock into head. Then I mount the body, cut recess in bottom, hollow it halfway, turn around and remount, then cut other half. But when I mount the body to cut the through holes, there is no centermark on the second cut where the tenon fits, so that is off just a hair, but that error doubles when you mount the head and turn it when it is all finished.

Is there any trick to keep those truly concentric?

This is not a problem if you have a design part there in the overall shape, but for a continuous curve style where you want a smooth line between the two pieces, this is an issue. I can get it close, but I want it closer.

[Dan Hintz]

Would a centermark tool not help? Simple little spindle-makers tool, allows you to find the centerpoint of a dowel.

Like this:

41oBwG2efPL-600x600.jpg

[Mike Golka]

I turn my blanks to a cylinder, drill the holes, then mount the blanks for final turning with an internal grip using Oneway spigot jaws for the body and a jamb chuck for the top.

[Jim Burr]

Similar to Mike's method, the only thing I do differently is once the holes are drilled is to re-assemble the top and bottom halves, bring up the tail stock and touch up the cylinder alignment.

[Dennis Ford]

I have had a similar problem; it was caused by the small drill bit wandering off center. A stiffer bit and careful feeding helps a lot.

[Quinn McCarthy]

ditto with mike and jim. I use the same jas too.

I have never had any concentricity problems and have done some biggies over the years.

Even if you are tad off you should be able to clean it up unless your were really off.

I like using my oneway tailstosk with the largest one that come when youm by the tailstaock. I have had the best luck with a forstner bit. that doesn't move off center a bit.

Hope that helps.

Quinn

[Stan Smith]

I used a kit from Craft Supplies. The top has a 1/2" tenon. There's a hole the size of the shaft through it. I follow basically the same procedures as the others. After I'm done drilling out the holes in the bottom piece, I put the top back on. The tenon on the top piece fits exactly into the hole in the bottom piece. With the 2 pieces together, I bring it back into round and then do the shaping. It seems that any time I take pieces off and on the lathe, I always have to bring them into round each time, but that may be due to my being clumsy.

[Kyle Iwamoto]

Drill first. I turned 2 loose tenons, that fit in the top and bottom. Use them between centers, friction drive or jam chuck, what ever you want to call it. For the top, I drill the top and insert a tenon the same size as the top of the mill. That makes the grain match up a bit better. Then I drill the 1/4" hole, use a pen mandrel to turn the top. Roughing to cylinder helps this since the pen mandrel can't take too much pressure from the gouge. Hope you have the same style mill as I have. Good luck!

[Bill Boehme]

I made a few pepper and salt mills for christmas gifts, yet I am having a hard time getting perfect concentricity of the head and body. Per the instructions:

Turn rough blank, cut tenon, part the two pieces, them mount the head by the tenon and drill a hole from tailstock into head. Then I mount the body, cut recess in bottom, hollow it halfway, turn around and remount, then cut other half. But when I mount the body to cut the through holes, there is no centermark on the second cut where the tenon fits, so that is off just a hair, but that error doubles when you mount the head and turn it when it is all finished.

Is there any trick to keep those truly concentric?

This is not a problem if you have a design part there in the overall shape, but for a continuous curve style where you want a smooth line between the two pieces, this is an issue. I can get it close, but I want it closer.

The headstock and tailstock axes are never absolutely perfectly aligned -- on most lathes they're close enough, but sometimes a lathe has more than the usual amount of alignment error. This can be a problem when drilling from the tailstock with the wood rotating because it puts side loads on the drill and may lead to wandering on smaller size drills. On large Forster bits that can't deflect, you might notice a squealing sound or even a bit of burning of the wood if running the lathe too fast and not clearing the swarf while boring. The solution for twist drills is to drill from the headstock and hold the wood against the live center point. Advance the tailstock quill a short distance to get the hole direction established and then just hand feed the wood. This method can also have problems with drifting if you are not careful and apply a side load on the drill. Another reason for drifting that sometimes is overlooked would be due to using a dull drill. If the drill is not progressing very fast, is squealing and burning and is producing powder rather than shavings then it is probably worn out.

I turn a 1⅝" tenon for a tight fit in the bottom of the mill, I join the two parts of the mill (at this point I prefer a tight fit, but if it isn't, wet the tenon and it should swell enough to make a tight fit. I drive with a Oneway dead center and use the small Oneway cone on the live center against the top. BTW, before joining the top and bottom, I undercut both parts slightly so that there won't be a visible gap.With everything assembled, the top and bottom are turned together for a perfect match.