Any ideas of re-centering piece in chuck

[SteveColes]

Once more I am trying to turn my first goblet.:yes4lo: Everything was going great:eusa_danc (I thought) I was hollowing the end grain to make the interior of cup portion, when suddenly the tenon slipped in the chuck. To make matters worse, it appears that it had slipped a bit even before, I noticed it. the hollowing of the cup is visibly off center from the shaped blank.:crybaby2:

What I'd prefer to happen is that I could re-center so that outside shape is correct or close to it. Any tricks you experienced turners have up your sleeves? :angry6wn:

 

[cskipper]

Call me clueless (again)

 

[Big Mike]

Steve, once you the wood slips in the chuck it becomes a matter of trial and error to find the "best" center you can. I know that is a poor answer but it is virtually impossible to find the center you started with particularly if you have any torn wood fibers where the wood slipped in the chuck.

One recommendation I will make is to mark the location with pencil lines of two different jaws, like 1 and 2, with pencil lines and put a number between them as a reminder which jaws were your reference. Sorry if that is not much help but that is all I have for now.....

Did you have a shoulder on your tenon/spigot for the chuck jaws to abut? If you didn't that can be a problem in itself. Also did the spigot/tenon bottom out in the chuck? If it did then that is also a problem. The most holding power is achieved by the chuck jaws contacting a shoulder on the piece while contracting on the spigot.

Worse comes to worse, start over. It is just a piece of wood.....I know easy for me to say as I am the world's worse for trying to save every piece after a screw up.....:-?

 

[michaelgarner]

good info Big mike, you saved the day again.

 

[Monty]

Yep, like Big Mike said. This is really a lesson for next time, I think. Make sure your tenon has a nice square shoulder for the jaws to rest on. One other point - your jaws are probably numbered. Make a pencil mark on the wood between the #1 and #2 jaws (always use this location, so you don't forget). This way you can re-chuck the piece the same way if it slips.

 

[SteveColes]

Thanks Monty and mike. It slipped becuase, I didn't tighten it enough. But I love the idea of marking the the tenon in relation to it its jaws:yes4lo: That will be a new SOP.

I've re-centered using a large cone on a live center in the tail stock. At least the hollowing will be centered:eyeslam: I'll just true up the outside again. The whole piece will now be a lot smaller diameter then intended, but I think I have enough thickness left on bowl of the goblet to get away with it. I'll just wait on the spindle till near the end and hope for the best

 

[Canuck]

You will post-it when you are done, right! Steve!!!:eusa_danc

I am in anxious anticipation for the completed goblet!!!!

Don't leave us hangin', Steve!!!!

Turn, Turn, Turn!!!!!!!!!!!!!!!!!!!!!!

Wayne

 

[SteveColes]

I am trained as a machinist, learned wood turning on my own. I am unconventional and don't know common wood lathe terminology, but I can do and have done great work.

If wood workers would learn to use a few of the machinist tools it would make some things easier. Most everyone I have met or talked to say that precision measuring is not needed for woodwork. And in lots of cases it is not, but at times it is good to know how to make exact measurements.

Centering is one of those times. You really don't have to guess or trial and error to get a work piece centered in a chuck or even under a drill bit. Dial indicators were invented for exactly this purpose and with the proper technique you can re-center a piece within 1/1000 of an inch.

It is worth the cost of the tools and time required to learn. Really minor compared to the cost of the lathe or even a fine chunk of wood.

Mike, I have a dial indicator, etc. But I'm not sure what the technique would be. Would you mind giving a lesson?

 

[SteveColes]

You will post-it when you are done, right! Steve!!!:eusa_danc

I am in anxious anticipation for the completed goblet!!!!

Don't leave us hangin', Steve!!!!

Turn, Turn, Turn!!!!!!!!!!!!!!!!!!!!!!

Wayne

I promise to however this turns out:shocked7fl:

 

[Matt]

NOTE: I am NOT a machinist, but I like to hang out with them (does that count for anything?)

Anyway to center your piece:

Take your dial indicator (in it's stand) and put the needle against the piece so that it is reading something on the dial. Tighten the stand / secure the indicator.

Turn your dial to zero it out.

Rotate the bowl (or whatever you are indicating), watching the needle on the indicator. You will find high and low points. I like to mark the high side.

Note: If you have a lot of runout, you may need to adjust / re-zero your indicator. Most are only capable of handling 0.200" or less.

I tap on the high side to move it over (with motor shafts I use a dead blow hammer, you might want to be a little more subtle with a thin wooden bowl).

Indicate again and note the high points.

Repeat until you have the part spinning as true as you want it.


Hope that helps. I don't know if this is the "official machinist" method, but it works for me...

 

[jeff...]

I big honking drill bit

 

[Big Mike]

I wish I had thought to mention the large cone. I have one and almost never remember to take it out of the box.... Short of the dial indicator method Mike and Matt are talking about the cone would be the fastest and most accurate method of recentering....At least good enough for government work.

In a previous life I did a little work as a machinist and had to use dial indicators to set up multi-axis milling machines. Of course I don't have a dial indicator any more and probably should get one because just as Mike and Matt said they are the best way to accurately adjust tools.

 

[SteveColes]

Well. I went with using large cone to recenter on goblet hollow and then re-truing the out side

So all went well and then I just neede to smooth this one little place.

:growl5cj: :growl5cj: :growl5cj: :growl5cj:

 

[DaveO]

Now, you make a scoop...that's the beauty of turning :lol::lol::lol::lol:

Dave

 

[cskipper]

:cry: Boy, bet you said the serenity prayer A LOT!

 

[DaveO]

I bet he said other things, too, a lot :BangHead: :BangHead: :XXcombust


:lol: :lol: :lol:

Dave