Struggling with Wobble

[Shane Sura]

Alright I really need some help. I have been really struggling with wobble. What I mean is this. Today I am making a shallow bowl/platter. I attached a faced plate. Roughed it out and cut a tenon. Then I flipped it around and put it into my chuck. Tighten everything down turn it on and the wobble starts. Now first thought of course is it is my tenon. The real issue I have is this happens EVERY single time I cut a tenon. My technique is pretty simple. Cut the tenon. I can't figure out what I could possible be doing wrong. Any suggestions?

Shane

[Jonathon Spafford]

One thing that I can think of off the top of my head is if you make the tennon so long that it bottoms out on the chuck, that can often cause wobble. Also make sure that their is a good square shoulder butting up against the jaws.

[Shane Sura]

Yea I thought of that. In this case the Tenon is not very long. Also the way I mounted it to the chuck is to sit the chuck flat on the table and then sit the bowl down flat into the chuck. It could be the square shoulders but I would think it would be equal as I faced it when it was attached to the face plate.

Shane

[Richard Madison]

Shane,
Lots of chuck questions tonight.
Having a cheap (economy) chuck, I have to compensate as much as possible.
How much "wobble" do you have?
Consider alternative procedure. Put chuck on lathe and put workpiece in chuck just tight enough to hold it. Bring up tailstock with center or whatever and piece of scrap to avoid making a dent in workpiece. Loosen the chuck slightly and apply some pressure with the tailstock. NOW tighten the chuck. Back off tailstock and remove scrap piece. If enough thickness is available, bring tailstock back up with cone center and apply enough pressure to make an impression. Rotate at low speed and check wobble. If this doesn't help, we need someone witha better answer.

[Kevin McPeek]

What kind of chuck is it? Is it possible that you need a dovetail tenon and are using a square tenon? What size tenon are you using? What is the travel and what size jaws?
If you could post a close up picture if the bowl in your chuck someone might be able to pick out what might be amiss.

[Mitchell Cholewinski]

Shane. Don't let the spigot bottom out in your chuck. Maybe you think the tenon is straight on the bottom and it might be concave in the middle. Try turning the center of the tenon down some to minimize the surface touching if the tenon is bottoming out. After you get a tenon you like, push your toolrest up against it and see if it touches all way across. Maybe you could use a dovetail tenon. I had the same trouble and it was just me doing it wrong. I use a super nova 2 chuck. Make your spigot right and it will work. Good luck. Mitch

[Philip Duffy]

Shane, There is an adapter available that mounts to the threaded portion of the Tailstock, onto which I mount the chuck. Then, when I take the bowl off the Headstock and mount it with the chuck, the alignment is just about perfect. The adapter is available from Woodcraft/Oneway, etc, and works like a charm. The small cost of the adapter is worth the removal of aggravation. Philip

[Steve Trauthwein]

A lot of good responses. What holds the piece stable is the end of the chuck against the shoulder. One should not be able to get a piece of paper between the chuck and the shoulder after mounting.

Regards, Steve

[Shane Sura]

As requested here are some pictures. The tenon is so small it is definitely not bottoming out and there is no room between the shoulder and the piece. The only thing I can think is the bottom of the bowl is not circular across though I do not know how that could be given I rounded it and sanded it on the lathe. Take a look and let me know.

I did end up mounting it on the chuck and reshaping it slightly so I am back in business.


Also could someone tell me how to do thumbnails sorry for the large pics.

http://www.thereviewstop.com/Bowl%20001.jpg




http://www.thereviewstop.com/Bowl%20002.jpg



http://www.thereviewstop.com/Bowl%20003.jpg

[Kevin McPeek]

When you have it mounted are your jaws most of the way open or most of the way closed? It is generally accepted that the jaws being as close to a circle as possible is the best grip, rather than having the corners of each jaw digging into the tenon. This means (on my chucks, SN2) that the jaws are nearly all of the way closed.
When you say wobble, do you mean the bowl is loose in the jaws or that it just doesn't run true?
It also appears that your tenon is fairly straight and your jaws look to be a Nova style which need a dovetail tenon. This may be bad form, but I use a skew on its side (as a scraper) to make a dovetail.

[Gordon Seto]

You need a sharp clean cut on the shoulder. From the picture, it seems that there is a bump on the shoulder preventing your bowl to sit flat on your chuck. If there is only a very slight gap at one side of the shoulder, there will be enough run out to cause wobble.

It is not the brute grabbing force of your jaws that holds your blank. It is how well the the dovetail fits and shoulder support that give the strength.

Gordon

[Bill Stevener]

Well lets see. :confused: You might try checking the internal dimensions of the jaws in different stages of opening and closing to see if all are working equally, one may be slightly ahead of the others. If you have one, a dial caliper works well.
Just a thought. ;)

I like your photos.>>>>>>>>>>

(edit) Just another thought. Could be the face plate is the culprit, it could be out of whack to start your problems??

[Shane Sura]

Interesting guys thanks for all the information. To answer Kevin's question it is that it is not running true not that it is going to come out of the chuck. In answer to Bills question I thought it might be the faceplate but I roughed it out on the faceplate thus making it cylindrical.

Gordon is the bump you point out on the tennon or actual bowl. I only ask because the tenon does not sit at the bottom of the chuck.

Finally, does anyone have any pictures of this "dovetail" tenon. I am still somewhat new to the lathe (since November) but in my 5 week class at woodcraft we made lots of tenon's for bowls and never mentioned a dovetail design.

Thanks!

Shane

[Jim Becker]

The "bump" that Gordon is citing is on the side of the tenon and visible in that picture. I agree that the tenon needs to be "clean" and well defined to insure a solid grip by the chuck.

[Bill Stevener]

I'm going to put this photo back. The mass left will not allow the work to seat properly against the face of the chuck, in this case, however you say you have the wobble prob. all of the time. I would still check the jaws on the chuck. 10-4???

http://i102.photobucket.com/albums/m109/nicebill/Bowl20003.jpg

[Bill Stevener]

One more to check. :confused:

http://i102.photobucket.com/albums/m109/nicebill/Bowl20001.jpg

[Shane Sura]

Bill,
How would damage to the outside of the chuck hurt the inside? I could see this causing a problem if I was using it as an expansion chuck.

Shane


One more to check. :confused:

http://i102.photobucket.com/albums/m109/nicebill/Bowl20001.jpg

[Bill Stevener]

Your photos show that your work is not seating equally (all points of contact) on the "face" of the Chuck. The mass shown left on the work will cause your prob. as well as, a bulge on the face of the chuck. They both act like a wedge, kicking the work to one side.

I'm going to do like my computer when I ask it a question.

Did you find this helpfull?

Yes_____NO____Somewhat_____

[Kevin McPeek]

I find a small amount of run out when I go from FP to chuck. It's more noticeable the larger the bowl. If you put your bowl in the chuck and rotate it by hand and bring up the tool rest up to the bowl at the point where it is closest to you and then rotate it 180* (should be the farthest away from you) what is the gap from the tool rest to bowl?

[Shane Sura]

I just noticed something while sanding. The runout on the Chuck seems very visible. I then took a flat piece of metal and let is sit lightly on the spinning chuck (round section not the teeth) and the metal jumped all over the place. Am I missing something or is the real problem runout on the lathe itself? I am now trying to figure out how to test runout without the fancy guage everyone seems to use.

Shane

[Andy Hoyt]

Take the chuck out and stick a dead center into the headstock. Turn the lathe on at its slowest speed and look at the pointy end of the center. Is it spinning on a single point in space or is it defining a circle. Bringing the tailstock up with a live center in it may help you visualize this. Or gently rest something on the spinning dead center's point. Is it bouncing?

Doing the bounce test on the chuck body or outer surface of the jaws won't tell you much.

[Bill Stevener]

You can use your tool rest, a 6" scale and your best eye. If the chuck causes the scale to travel 1/64" = 0.015", your chuck is out 0.007". However, the bouncing pc. of steel seems to indicate you could have a prob. with the chuck not seating fully on the lathe. Check for foreign matter or dings on the mating surfaces. There are other situations that may cause the same, but one step at a time.

[Keith Christopher]

Are you 'truing' up the face prior to making the foot ? I usually mount the piece between centers and the using a scraper or a shear cut flatten the faces of the work before putting a foot on it.

[Bill Stevener]

How old is your lathe and what make is it?
You can try Andy's test, this may indicate a bent shaft. However, not always reflect failing bearings. A side thrust test with the aid of a dial indicator will reveal if its the bearings. Of course if you can move the shaft by hand, you know its the bearings.

[Shane Sura]

Ok here is what I did. I tried my dead center, live center, and my drill chuck. All in the head stock. Each seemed to have a noticeable run out. Not trusting my eye I did the most scientific thing I could find. I took a sharp pencil, put it on the side of the drill chuck and turned the lathe on let it run and turned it off. Once it was off I could see the pencil line dark in some places and not in another. Tried this a couple of times to rule out shaky hand. So don't know about you but this seems to be runout the question being how much is this?

BTW it is a harbor freight lathe. Now before I hear all the groans I know for a fact many people on this forum consider this to be one of the more acceptable tools from them. I also know someone personally who had this exact same lathe for years without any issue. This is the same model that is the Jet 12 inch knock off.

So I called the store and I am going to replace it. I did want to post this to see if you all had any other advice before forcing the LOML to help me carry it again :eek:. While I am there I think I am going to buy their 7.99 dial guage to check runout :D.

[Bill Stevener]

I was not looking to knock your lathe. Good luck with a new lathe. If it were me, I would put the lathe in the truck and take it to the store and not have the LOML help me carry it there.:)

[Shane Sura]

Thank Bill. I did not think you were going to knock it I just was waiting for the inevitable that what you get for buying from HF etc. Also the LOML convinced me not to walk all the way there :p.

What I am really hoping is this fixes it. I am worried that this is an inherent deficiency with the HF lathe and now I am questioning if they will take a straight return > 30 days old. The only reason I bought it was because there was a number of people on here and local who had good luck with it. I got it on a great sale +15% off so all told walked out at < 150. Now thinking maybe it was a mistake overall.

Shane

[Mike Ramsey]

Not trying to knock your lathe either, I have one & it sets in the corner
gathering dust for the last 2 yrs..Before anyone asks why did I keep it,
I just didn't feel like I could sell it with a straight face! It works ok for
some spindle work but It had the same probems your having & I
could never get It aligned properly.

[Al Wasser]

I always have some wobble when I reverse. As stated above the larger the object the more the wobble. Having asked others, they seem to have the same thing SO, I have 2 choices -- final sand before I reverse or reverse and then take out the wobble with tools and sandpaper of your choice. I would caution that it is best to complete the entire operation in one session. Do not form the tenon today and then let the wood set for a day or more before reversing it. By shaping the wood you have changed the internal stresses and some wood will move quite a bit and it will surely move as you hollow out the object.

[Reed Gray]

After turning a couple thousand bowls, I still get some that wobble when reversed. Two things seem to reduce it. One, make sure that there are no shavings where the jaws of the chuck are going to seat. No strands of fiber sticking up, etc. You need a flat smooth surface for the chuck jaws to attach to. Also (I use a recess rather than a tenon) the final cut for the tenon or recess should be one where the tool just barely touches the wood, taking only the tinyest whispy shavings. Let the tool sit there for a short while.You always get a tiny bit of wobble from how the tool reacts to the wood. As the wood goes round and round, you cut flat grain, and end grain, and the tool reacts differenetly to both kinds of fiber orientation. By just barely touching the wood, you can remove some of this bump/wobble. If I have less than 1/16 of an inch wobble, I am pretty happy. If I am trying to turn something very thin (less than 1/8 inch) I will touch up the outside of the bowl before I turn the inside. Getting it perfect seems to be accidental but some times it happens. You can rotate the bowl 90 degrees, or 180 degrees, and some times this helps. You can also tighten the set screws for the jaws of your chuck every once in a while, One loose jaw can cause wobble. Also, you can remove the jaws and make sure that there isn't anything under them. Other than that, your chuck could be out of whack.
robo hippy

[Shane Sura]

Ok new lathe on the bench. I also bought the dial indicator and magnetic base while I was there. What I Did to test it was I put the spindle in and put the dial up to the spindle. After turning it on it wobbled from 0 - .005 (If I am reading it right on the dial it went from zero to 5). I did the same thing on the end of a pen mandrel (I put the dial right on the end of the MT2 taper before the mandrel shaft). Both times it ran to .005. Is this good/bad or indifferent. If I threw a Jet mini up on the table would the results be the same? Am I ultimately taking a small problem and wasting a lot of time and energy on it? I have read reviews of lathes with people mentioning larger runout then this without much bad to say. Any help would still be much appreciated. :confused:


Shane

P.S.,
I also put it on my drill press and it was much worse.