Vibration frustration - Woodworking Talk - Woodworkers Forum
 
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post #1 of 7 Old 02-20-2010, 09:24 AM Thread Starter
 
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Vibration frustration

I am relatively new to turning and I am looking to solve a vibration problem when I am turning spindles. I have a Powermatic #45 and I am wondering if my drive center is worn. I think it is a #2 Morse. Should the collar with the four drive spurns bottom out against the drive spindle? Should I be able to easily remove the center after turning? Or should it require some force to remove the center?

-Thanks
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post #2 of 7 Old 02-20-2010, 01:21 PM
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We probably need a little more information. Are you turning a thin or long piece. If so vibration or chatter is a common problem. Vibration is do to flexing of the wood. There are a lot of causes but mostly it's too much pressure on the bevel of the tool.
To eliminate the chatter you first need to make sure your tools are very sharp. On a skew if it will shave hair off your arm it's perfect. Less than that and it will work but takes more pressure which of course can cause more chatter.
The first thing to do is to make sure you have the drive center firmly in place so it won't slip. Then tighten up the tailstock. Now back the tailstock off until it acts like it's trying to slip. Increase the tailstock pressure just a little. To much pressure from the tailstock will cause the wood to flex.
I use a rough out gouge to get most of the wood to shape. Take lighter and lighter cuts when you start to get chatter. I turn right handed so I use my left hand over the spindle to dampen the chatter. The harder you push on the bevel of the tool the more pressure you have to put on the back side of the wood with your fingers. This burns your hand. The lighter the pressure on the bevel the lighter you have to touch. When it's just right you don't burn your fingers. As a new turner you should probably turn the speed of the lathe down to keep from burning your fingers as easily.
If all else fails and there is enough room. Use a belt sander to smooth it out. That's what my dad does and it works for him.
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post #3 of 7 Old 02-20-2010, 04:52 PM Thread Starter
 
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Thank you for your advice John. I can easily shave the back of my thumbnail with my tool. I am never sure when sharp is sharp enough, I currently sharpen with progressively finer sandpaper on a glass plate. The spindles I am turning are between 16 and 24 inches long, 1.5-0.5 inches in diameter, out of maple. Should I be able to pull the drive center out of the lathe easily by hand? Is it possible that the vibration is a result of the drive center wobbling sightly? It may be that I am putting too much pressure with the tailstock, but otherwise the drivecenter slips. I have no trouble roughing the blank with a roughing gouge, it is when I switch to a smaller spindle gouge, or a skew chisel that the vibration starts.

Last edited by athorp; 02-20-2010 at 04:54 PM.
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post #4 of 7 Old 02-21-2010, 01:11 PM
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Quote:
Originally Posted by john lucas View Post
....The first thing to do is to make sure you have the drive center firmly in place so it won't slip. Then tighten up the tailstock. Now back the tailstock off until it acts like it's trying to slip. Increase the tailstock pressure just a little. To much pressure from the tailstock will cause the wood to flex....
Thanks for the tip on adjusting the live center John. I did not know that. Now I understand why I was getting so much chatter when i was turning my baseball bats. Tail stock was too tight.
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post #5 of 7 Old 02-21-2010, 01:11 PM
 
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Athorp,

I am also new to wood turning. This is what I have read about that vibration/chatter. From a book called Modern Woodturning by Gordon Stokes " There are two possible answers to this, one of which is to steady the work with one hand around it whilst turning with the other. The other is to use a steady." I didn't know what a "steady" was. If you use a search engine and look up "woodturning steady rest" you get a whole ton of information on how to buy one and/or how to build one. There may even be some info on this site. Good luck!
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post #6 of 7 Old 02-21-2010, 01:28 PM
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It takes a lot of practice to learn to cut without chatter. For years I would get it as best I could and then just sand it out. The size legs your turning are about in the middle of the chatter category. I turned some just recently that tapered from 1" to 1 3/4" over a 31 inch length. I was able to get rid of virtually all the chatter. I could not have done that just 2 or 3 years ago.
There are two things that I do that helps. One is to change the angle of the skew so it's not repeating the spirals. You just want to remove the top of the spirals. Take very light cuts. I push the skew down on the tool rest with my left thumb to steady it so it doesn't bounce and then I cup my fingers over the piece to steady it.
When your first learning try using a spindle gouge with a really small tip. I use a 3/8" Thompson detail gouge. You still have to take very light cuts. It's harder to get a really smooth curve with the small tool which is why I use the skew.
If I can post it there will be a drawing of a really simple spindle steady. I used to use the steady some but now I've gotten to where I don't need it. It takes lots of practice. I turn a ton of 3/4" by 9" spindles that taper to 3/8" at both ends. They chatter easily so I've had lots of practice. I find the longer thicker spindles to be harder to do.
I almost forgot. Turn your spindles from the center out if possible. This way the wood chatters less but it is hard to do a long taper like my walnut legs. For those I just had to work from big end to small end.
If your drive center is driving the wood and you can't feel any slop when pushing the piece toward the tailstock or headstock then it should be firm enough. If your having chatter problems don't use a Steb center. The center spring is those is too strong and actually causes chatter.
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post #7 of 7 Old 02-22-2010, 06:59 AM
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I forgot to say that I'm going to build another one of these but I'm going to install rollers where the V notch is. The way these were used is to make your last turning pass right where the V notch is. This gets rid of the friction marks,hopefully. some serious sanding is needed at times. With rollers there won't be any friction marks just shiny spots that are easy to remove.
If you wax all the surfaces the wedge actually drops down under it's own weight and compensates for the changing sizes of the spindle. This is better than the screw adjustable steady's I think.
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