Parting is such sweet sorrow...

Roger Tulk

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Location
St. Catharines, Ontario, Canada
Today I turned a 3" pepper or salt shaker in the end of a 15" piece of Butternut. Everything went marvellously until I went to part it off. I had mismeasured the depth of the hole for the salt container, and cut into it with the parting tool, with dramatic effect. The shaker bounced off my shoulder and disappeared, and the long part of the workpiece scurried under the frame of the lathe and hid in a corner. The shaker itself cracked and a chunk came off the base, and it fell, appropriately, into my firewood box.

Now, I know the mistake I made with the measurement, and I won't do it again. I've parted off a number of things in my short turning life, but I'm wondering with a piece like this, which has a long straight span beneath the piece, couldn't I just take it off the lathe when I am finished shaping the end piece, put it into my table saw and cut it off at right angles? This is what I did to remove the stub from the long part, and it is perfectly at right angles. It would have saved me a lot of trouble if I did, and I would actually have a salt/pepper shaker to show off to my friends and adoring relatives.

Parting definitely makes me nervous, although I do it with an appearance of professionalism and insouciance. When I part things with my Benjamin's Best parting tool, it cuts nicely through the piece, but usually leaves me with a nub that I have to trim off. Is this normal?

OH, BTW, my sharpening must be OK, because I am definitely getting shavings from my tools, and not dust.
 
...and it fell, appropriately, into my firewood box...

Sorry to laugh at the pain of others, but that's funny stuff right there. :D

As for cutting a round piece (a cylinder) on a table saw, it can be done, but the workpiece should be held firmly to the miter gauge - clamped preferably. There is a real risk of the piece rotating when it meets the blade, and if that happens, things can get dangerous quickly. It's also important to control the off-cut. Since it'll be round, there's a risk of it rolling into the blade and becoming a missile. Personally, I'd stick with the parting tool. ;)

Parting has always been tricky for me on a piece that's held between centers on a lathe. When the one piece becomes two, I don't enough hands to catch both pieces and hold the parting tool. For that reason, I don't part anything off with the parting tool unless one end of the workpiece is held in a chuck. If I'm running between centers, I'll use the parting tool down to about the last 1/4 or so, then stop the lathe and use a flexible flush-cut saw to finish the cut. Here's the one I use:

http://www.amazon.com/Shark-10-2204...UTF8&qid=1407119025&sr=8-3&keywords=shark+saw

(And don't forget to loosen the tailstock pressure a bit before starting the saw cut. It helps keep the blade from binding as you cut.)
 
....Parting has always been tricky for me on a piece that's held between centers on a lathe. When the one piece becomes two, I don't enough hands to catch both pieces and hold the parting tool. For that reason, I don't part anything off with the parting tool unless one end of the workpiece is held in a chuck. If I'm running between centers, I'll use the parting tool down to about the last 1/4 or so, then stop the lathe and use a flexible flush-cut saw to finish the cut. Here's the one I use:
http://www.amazon.com/Shark-10-2204...UTF8&qid=1407119025&sr=8-3&keywords=shark+saw
(And don't forget to loosen the tailstock pressure a bit before starting the saw cut. It helps keep the blade from binding as you cut.)

Ditto on how Vaughn does it. Also don't forget that pepper mills have that nice hole in the center which you can slide on an appropriately sized mandrel to fix mistakes or finish/sand the top after you part it off. I prefer the band saw for trimming these small pieces, with the caution to feed slowly and hold the piece firmly against the miter gauge so it doesn't spin. Less dangerous than the table saw.
 
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Slip a peice of white PVC sewer pipe over it to use as a catchers mit maybe??

So now instead of having two loose pieces when the cut goes through, he'll have three. ;)

As I mentioned earlier, the easy solution is to use a chuck (and a tailstock) instead of turning between centers. That way you only have to catch one piece, and it's possible to have a free hand available to do it.
 
So now instead of having two loose pieces when the cut goes through, he'll have three. ;)

As I mentioned earlier, the easy solution is to use a chuck (and a tailstock) instead of turning between centers. That way you only have to catch one piece, and it's possible to have a free hand available to do it.

Yep, agreed...
 
It can be. Pic's would be appropriate...and stuff like speed, angle, diameter...unless you were looking for something else???
 
I didn't get that he was turning between centers, but like Vaughn, when I turn peppermills, I'll turn the blanks round between centers, but always add a small tenon for a chuck... I usually mark the lengths of the mill and will use the parting tool to divide the blank into the two pieces, then I use a chuck to drill the blank.... after I've drilled the mill, I switch the body to a couple of jam chucks that I made specifically for pepper mills... the top piece gets put back on a spigot chuck to turn the ball I use on the top of my mills.
 
I was turning between centres when I rounded the workpiece and cut a dovetail for the chuck. Then with the chuck in place I drilled the end of the shaker, and shaped the piece. Then I parted off the shaker, or tried to. When the parting tool ran into the hole in the centre of the piece is when the piece flew apart, and the part that was in the chuck slipped out and went in one directtion while the shaker went in the other. Today I put the wood back on the lathe and tried to drill the end, but the piece kept slipping in the chuck, and I had to tighten the chuck several times, until I gave up and put the piece back on the spur centre, and was able to finish drilling the hole that way. Then I shaped the shaker (I'm not doing mills yet, I'm working up the nerve,) and took the whole thing off the lathe and parted it off on the tablesaw. I cut a new dovetail while I had the stock on the spur centre, and I will try it again tomorrow, if the weather is good. The salt/pepper shaker looks very good and only needs a little finessing with sandpaper to be complete except for finish.

The chuck doesn't seem to hold very well, and I don't know if it's something I'm doing or not doing. I had the same chuck model on my old lathe, and it seemed to work fine. The chuck is this one, from Penn State.I'm wondering if there's a screw I should be tightening to make the jaws hold better after I tighten them. As I say, i didn't have any trouble holding stuff in the chuck I had before.
 
Roger buddy you're scaring me here just a little I must admit! :twocents:

I'm not entirely surprised that the shaker went the wrong when when the parting tool went into the hole - that could be a pretty nasty catch alright!! :eek: Hard to work around that except triple check your depths and don't get to speedy on the parting tool should help.

The part that shouldn't be happening is the chuck issues! We've got to get your chuck working. Having the pieces pop out means that something is quite wrong somewhere, the only way they should come out is if the tenon breaks off (usually because its a bit cross grain on a bowl bottom .. not that I've ever done that :rolleyes: .. which, I suppose, is largely why many turners prefer a recess in those cases).

It might well be you have a bum chuck but it probably makes sense to triple check all the obvious other points:
  • double check your tenon size, it should be just a smidge bigger than the ID of the jaws when they're closed ideally.
  • Reading the specs & q's it looks like those are ?probably? shark tooth jaws, so if the wood is real hard they might have a tough time getting ahold unless you really crank them down. Did you're old chuck have those or dovetail jaws? Personally I like the dovetail a smidge better because there is a bit more positive grasp in my opinion. Can you see where the jaws bit into the wood?

I did see one complaint in the Q&A section of the PSI page about that chuck about it not gripping well, the consensus was to crank down on it.. and then further down someone said they cranked down on it and it went ping and broke.. so.. :dunno:

If your chuck has a good hold you shouldn't be able to manually turn/wiggle/pull loose the piece at all. If you can.. well.. cross check the whole situation.

Hoping you get it all figured out here :crossed:
 
Ryan, I had a look at the comments also, and saw several that mentioned the jaws loosening in use. Some didn't, so there may be some inconsistency in manufacture. I had cut a dovetail in the end of the stock, but it was a tenon by the time I had tightened and retightened and retightened the jaws. The jaws have three deep ridges to hold the work, not a dovetail. I recut the dovetail yesterday I'll mount it back in the chuck tomorrow, maybe, or I may just use the spur centre because I can, and it will work finf under the circumstances, especially if I don't part it off with the parting tool.

When I was using the chuck yesterday (and I had used it the day before, and was using it when the bad incident happened,) it quickly became so loose that even a light touch with the spindle gouge caused the work to stop, and the chuck to spin around it. I was able to dril the 15/16ths hole for the salt container with a little effort and a retightening. However, I put it back on the spur centre to shape it.

If I continue to get unsatisfactory results, I will phone Penn State, and ask for a solution; perhaps a new chuck body.

I'm not going to do anything with it today, as we are to have thunderstorms all day, and I am taking my niece to see a Jays game in Toronto. They are giving away Jose Bautista t-shirts today.
 
I don't believe that you'd want to put a dovetail on the tenon with these jaws - your best grab should be where the profile of the tenon matches the profile of the jaws as close as possible,

The fact it became loose while it was just spinning doesn't really give me a lot of faith in that chuck!!
 
...The jaws have three deep ridges to hold the work, not a dovetail. I recut the dovetail...

Ryan is right...if the jaws don't have a dovetail profile, neither should the tenon. Make the tenon shape match the shape of the jaws.

...even a light touch with the spindle gouge caused the work to stop, and the chuck to spin around it...

Something sounds fundamentally wrong with your chuck. No chuck should ever get that loose in use.
 
Roger,
Ryan may have mentioned this in his posts..(I didn't read all the way through).. but when you cut your tenons, make sure they match your jaws... I did a bowl a few days back and when I cut the tenon, I actually tapered it a little to the outside instead of cutting it straight sided... the chuck only grasped it by the very out edge of the jaws, which acted a little like a pincher jaw and cut into the edge of the tenon... needless to say I had to retrieve the bowl from the yard 3 different times... (my lathe sits in the door way and with doors open anything that flys off usually and hopefully will go out side)... after the third try, I decided to try to correct everything next time I try this particular piece of wood.
 
You guys are killing me! I just learned to make a perfect dovetail with a parting tool, and now you tell me I shouldn't make one! Anyway, I think i solved the issue with the chuck not holding. I put a metal rod in the index hole on the lathe, and really reefed down on the tommy bar with all my 200 lbs. and it didn't come loose in use. I had also changed the dovetail into a tenon. I finished the salt shakers, and will post a pic tomorrow.
 
Hmm...you shouldn't have to romp down on the chuck that hard to get it to hold. You can actually overtighten chuck jaws. This crushes the wood fibers and can weaken things to the point that the tenon breaks off the workpiece. (I know this from personal experience.)

You mentioned the Tommy bar. Do you just have one? All the "Tommy bar" chucks I've seen use a pair of bars. You should be able to put them in holes near each other (on opposite scroll rings) and squeeze them together to tighten the jaws.

I went looking for a video to show how Tommy bar chucks are tightened, but didn't come up with anything. I did find one that talks at length about tenon size and profile, though:

http://youtu.be/Ypp2hssuF1Q
 
Yes, I do have a pair of Tommy Bars, but I just used the one with a pin in the indexing hole. It was when I tightened with the two bars that the thing loosened.

Ah, OK. :thumb:

Do the scroll rings move smoothly and easily when there's nothing in the chuck, or do things feel a bit stiff?
 
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