Out of Balance-way out

[Brad Girod]

I’m having a real problem with bowl blanks. Dry cherry 6X3 inches it is out of balance, even though turned round its wobbling and when I true up the face it’s banging against the tool especially nearing the rim. It’s mounted on a Nova woodworm screw. I thought perhaps the screw was bent so I mounted it on a different chuck but got the same results. It’s so far out that I can’t turn it. I am now making a face plate to see if that helps. If anyone has run across this issue please, please advise. The lathe is an old Delta 46-460 but it doesn’t seem to be the spindle since the chucks run true.

 

[hockenbery]

Do you have a dried bowl that was turned green?
It will be out of round. You can see how I deal with a warped bowl see link below.

If you have a solid block of cherry turned round on a screw center it should not wobble.
Most likely Something is loose. Chuck not screwed on tight. Screw not tight -hole too large
Headstock is moving, banjo is moving.
It is possible that you did not turn it round. If you get lots of bounce with your tool while turning it round the bounce is turning it not round. Dull tools, Pressing too hard on the bevel, taking too big of a cut can all cause the bounce.

Link to video of a Demo where I mount and return a warped bowl

View: http://www.youtube.com/watch?v=sCZWsHB4vlM

 

[Brad Girod]

Thank you and I appreciate the video my gouge bounces off the face just like in the video. I drilled a depth hole to insure I wouldn't go thru the bottom and that much worked but now I'm going to sacrifice this blank to find out what the problem is. I can mount another blank but then it will do the same thing. I wish I had a video to put up. The depth hole now shows how far out this little timber is. I have a face plate somewhere but since I can't put my hands on it I will make one and see where that takes me. You are right something is out of whack!

 

[Tom Albrecht]

Can you post some photos of your setup with this blank?

 

[Richard Coers]

What speed are you spinning it? A 6x3 should be a piece of cake! Do you have the lathe bolted down? What kind of base? Don't start on the face, start on the turned outside diameter and cut towards the center.

 

[Mike Johnson]

This will most likely be one of those palm slapping forehead moments if we find out what the issue is.
I would get the bowl/blank mounted on an adjustable chuck with a tenon and then true it up.
Start with the basics and determine each possible variable with the problem.
Is the wood wet or dry? (Is it stable enough to finish turning)
Is the wood blank solid? (Might be cracked)
Are the threads holding solid in the blank? (poor threads, bad spot in the blank)
Is the screw mount straight? (Is it bent)
Is the screw mounted squarely in the blank? (Each time you remount the blank it is not square to the chuck)
Is the screw mount securely held in the chuck? (It might not be tightened all the way down on the screw head)
Is the chuck working correctly? (Are there loose screws/fasteners)
Are there issues with the headstock or spindle? (Bad Bearings, Bent Spindle)
What is the run-out on the spindle? (Does your spindle run true to the axis)

 

[Brad Girod]

Thank you, the blank snugged up nicely, I am worried that the screw is bent so I put the calipers to it and it certainly appears straight. It's a Nova G-3 chuck and it appears to run true. I can't flatten the face because of the bounce. I removed the blank and in desperation drilled a shallow recess but when mounted it still wobbled. At this point I don't care about the blank that's why I'm turning a faceplate. The thinking is that if I can somehow mount it on that then I should be able to true it up. I think this has actually happened once before so I hesitate to proceed without knowing why.

 

[Mark Wollschlager]

When your gouge is in contact are you getting cuts?
It looks like you have had luck turning it round and sanding the outside.
I have had cherry that was very hard and only a very sharp tool at the right angle would give me a good cut.
If you cut back toward the headstock do you get a clean cut. Like from around the pencil line.

 

[Gerald Lawrence]

A test. Bring up the tailstock then see if you still have the wobble. If you have wobble with tailstock up try to make light cuts to true the blank. Since you have drilled the tailstock side then you will need a cone center to center that side. Another thought if the cone center does not line up with the hole then the blank is moub=nted off center.

 

[Brad Girod]

Okay, here goes. Yes, I've tortured this blank and that's why I drilled thru the bottom in every effort to get it in balance but I haven't tried the tailstock! So, I'm hitting myself in the head. Why didn't I think of that. Thank you.

 

[Brad Girod]

When your gouge is in contact are you getting cuts?
It looks like you have had luck turning it round and sanding the outside.
I have had cherry that was very hard and only a very sharp tool at the right angle would give me a good cut.
If you cut back toward the headstock do you get a clean cut. Like from around the pencil line.

When your gouge is in contact are you getting cuts?
It looks like you have had luck turning it round and sanding the outside.
I have had cherry that was very hard and only a very sharp tool at the right angle would give me a good cut.
If you cut back toward the headstock do you get a clean cut. Like from around the pencil line.

Hello Mark, I managed to cut it with a gouge and get it round but after that it went to hell in a handbasket. I don't know what to think that's why I posted it. The calipers say the screw is straight. How can it be mounted off-center when it's been turned round on any given axis? the drill hole really gives it away. I can attempt another cherry blank but I'm afraid it will be the same story. I need to figure this out before it goes any further. Thank you for wading in on this.

 

[Brad Girod]

A test. Bring up the tailstock then see if you still have the wobble. If you have wobble with tailstock up try to make light cuts to true the blank. Since you have drilled the tailstock side then you will need a cone center to center that side. Another thought if the cone center does not line up with the hole then the blank is mounted off center.

Okay, tailstock up and light cuts with 1/2 inch gouge made improvements but the face is banging against the tool. Tried scraping it with a skew and made some progress but it's still banging. I will persist and find some answer to this nightmare. Thanks again.

 

[Bernie Hrytzak]

If you have an out of round piece, you can't ride the bevel. You should anchor the tool down to the tool rest with your l hand and take controlled cuts with the edge of the gouge. Once roundness is established you can use the bevel to guide your cuts. (don;t push hard unto the bevel)

 

[hockenbery]

Okay, tailstock up and light cuts with 1/2 inch gouge made improvements but the face is banging against the tool. Tried scraping it with a skew and made some progress but it's still banging. I will persist and find some answer to this nightmare. Thanks again.

I think what you have is a face out of square with the lathe bed. Thus is usually the case when a piece is flipped end for end and put into a chuck.

The way I find easiest to cut the face is to work from the outside in cutting parallel to the lathe bed toward the tailstock in 1/2" cuts. With the hard cherry you might try 1/4" cuts. Begin the cut slowly the bevel will make a place to ride on the interrupted cut with the bevel parallel to the ways let the tool cut until it feels real smooth- this is where it is flat. Make the next cut and just befor it matches the last cut pull the tool toward you scraping across the surface.

In the video below
Fast forward to 17:14 you will see the face is about a 1/2" off square.
Because this is wet wood I can make a 3/4" cut. I also push to tool in a little faster than Than I recommend. If this were dry wood I would have to take lighter cuts.

View: http://www.youtube.com/watch?v=Lo0bGSafZq4

 

[robo hippy]

The problem I had with screw chucks is that you need a dead flat surface for the blank to contact the face of the chuck. If there isn't firm contact all the way around, it will wobble, much like cutting a circle on the bandsaw with a piece of wood that had a 'rough' chainsaw cut...

Some times, chuck jaws will wiggle because the set screws manage to work themselves loose...

robo hippy

 

[hockenbery]

One other thought is the worm screw is loose in the chuck.
The nova chuck screw should have 4 flats on the nut part. Those flats should face the jaws.

When the chuck closes the auxhillery jaws will go into the slot in the nut portion and the main chuck jaw ends will center in the flat. This locks the screw in place so that it cannot turn.

To many people it seems intuitive to face the round part toward the jaws.
The chuck will often close on the high spots of the nut well enough to screw on the blank.
In any event the screw nut is likely off the high spots. This will let the blank wobble.
Also if the blank is screwd on with the nut loos the screw will move to one side as it tightens making the hole slightly off center. The blank gets turned round because it is tight o the chuck but the screw hole is off center.

 

[Richard Coers]

I'd suggest you desperately need personal assistance. You are missing on some very basic bowl turning techniques that watching videos and talking on a forum are just not going to give you. You can certainly keep banging away and learn over several months, or get some hands on help and be turning in days.

 

[Brad Girod]

I think what you have is a face out of square with the lathe bed. Thus is usually the case when a piece is flipped end for end and put into a chuck.

The way I find easiest to cut the face is to work from the outside in cutting parallel to the lathe bed toward the tailstock in 1/2" cuts. With the hard cherry you might try 1/4" cuts. Begin the cut slowly the bevel will make a place to ride on the interrupted cut with the bevel parallel to the ways let the tool cut until it feels real smooth- this is where it is flat. Make the next cut and just befor it matches the last cut pull the tool toward you scraping across the surface.

In the video below
Fast forward to 17:14 you will see the face is about a 1/2" off square.
Because this is wet wood I can make a 3/4" cut. I also push to tool in a little faster than Than I recommend. If this were dry wood I would have to take lighter cuts.

View: http://www.youtube.com/watch?v=Lo0bGSafZq4

That finally, painfully, did work until I turned it around and then back to the wobble-wobble. So back to the 1/4 inch cuts.

 

[Brad Girod]

I'd suggest you desperately need personal assistance. You are missing on some very basic bowl turning techniques that watching videos and talking on a forum are just not going to give you. You can certainly keep banging away and learn over several months, or get some hands on help and be turning in days.

Wouldn't that be nice.

The problem I had with screw chucks is that you need a dead flat surface for the blank to contact the face of the chuck. If there isn't firm contact all the way around, it will wobble, much like cutting a circle on the bandsaw with a piece of wood that had a 'rough' chainsaw cut...

Some times, chuck jaws will wiggle because the set screws manage to work themselves loose...

robo hippy

Now I did think of that dead flat surface and I believe at this point that may well be the root cause here. And since it's dry timber I am going to run the remaining thru the planer a few more times before I make another attempt.

 

[Bill Boehme]

First of all, welcome to the AAW forum, Brad. If you have any questions or comments please don't hesitate to post them.

I don't know if this has been suggested yet, but something that I always do after I mount the wood in a chuck or faceplate and before turning the lathe on is to use fairly strong arm force to try to see if I can wiggle the wood side to side. If it isn't mounted rock solid then there is something that needs to be corrected before proceeding. Either the wood isn't mounted correctly, the wood has a hidden defect or is punky, or there is a mechanical problem with the chuck or lathe.

Of course, there are numerous other possibilities that probably have already been ruled out such as technique or tool sharpness. Turning wood that has interruptions where you're turning air some of the time can be quite a challenge. To do it successfully requires sharp tools, light cuts, and anchoring the tool to the rest rather than trying to do a bevel riding cut. If you get the opportunity to get some fresh green wood for practice, it is always good therapy for building your confidence and skills because it is much more forgiving of mistakes than dry wood.

One final thought is that on rare occasions I've encountered wood that refused to be cut because of high mineral content which forms hard crystals in the wood and dulls tools almost instantly. The worst that I ever encountered was a piece of black walnut. I haven't turned much cherry so I don't know if it is prone to having mineral deposits.

 

[Bill Boehme]

I just checked for the location of woodturning clubs and found that the North Carolina Woodturners is very near you. They meet at Klingspor's Woodworking Shop in Hickory North Carolina which is about 12 miles from your location. They meet on the second Saturday of the month at 10 AM. That would be an excellent opportunity to meet with other woodturners and share information and also find a mentor if you need help with any aspect of turning.

 

[musky]

No need to run through a planer for a flat surface. Can be done on your lathe with a 4 prong drive and a rotating center in your tailstock. .You could also just turn a foot right away for your chuck, and not have to ever use a screw in your chuck again. It sounds as though you have a woodturning club in your area, and that would be a good first step in not only learning to turn, but also making some really good friends at the same time. I belong to two clubs, and most experienced members really look forward to helping new members learn to turn. I think you will find that joining a club will be your fastest path to learn to turn.