Plate Edge Getting Chatter and "Waves"

[Joe Vincent 63]

My plates are getting a little better - no flying saucers today! I do have a question thought ... on a 7" popular plate (1" thick blank), as I am attempting to turn the outer edges of the face, I get chatter - very loud screeching noises, and the tools cut "waves" (literally) in the wood on the face of the plate. Doesn't matter if I use a scraper very lightly or a bowl gouge (again very lightly). Inner portion of the face is smooth with no waves. The outer edges never true up and cut smooth.

Lathe is a Powermatic, plate was held by SN using 2" jaws expanding outward in a dovetail recess.

Any thoughts on what I could be doing wrong would be greatly appreciated!

Joe

[Mark Levitski]

Hi Joe,

Depending on how thin you are getting, you might have to support the outer edge as you make the cuts. It is probably fluttering on you a little and you will never get a smooth cut that way, thus the "waves". On bigger pieces some people use a steadyrest of sorts, but lots of turners just use their hands. You can pick up a handful of coarse shavings to put between skin and piece. Yes, that means you are cutting with one hand and holding with the other. I never get to worried about screeching as long as the cut is going OK.

If it's the rim's outer edge that you are trying to cut, you will not have much luck with a scraper no matter how sharp. Rather, you are better off to use a tool that cuts or slices instead of scraping. Even then, I try to get the edge done while it's thicker, then take it down to final thickness on the faces. Some pieces I resort to a sharp detail gouge for that.

Hope this helps a little........................Mark

[Rich Aldrich]

I sometimes have to support the outside of bowls with my hand for final cuts on the inside of bowls for similar reasons. I havent had the screech, but have had the chatter. The chatter makes for a lot more sanding. Supporting the edge eliminates the chatter and reduces sanding.

[David E Keller]

+1 for the idea that your piece is flexing near the rim. You can fashion a steady out of a single wheel to sit behind the rim or use your hand as the others have suggested. On thin, wide forms, I try to finish the outer rim before moving into the center of the piece... Sometimes, I have to do it in stages.

[Jim Burr]

+1 on working on the rim first. The screeching is a harmonic due to the thickness of the wood; thicker wood absorbes the noise. If you are using a hand to balance the rim...may want to try a glove just for protection

[Joe Vincent 63]

Thanks everyone, I believe that is what is occurring. I did the center first, then worked my way out the to rim. The edge was really no problem, it was 2" or so of the outer face. Do they make steady rests for these types of applications? I will try the hand method first, but thought I would check as at my stage of learning, I like to keep 2 hands on the tool at all times.

David, when you are referring to a single wheel as a steady, what do you mean?

Joe

[Kyle Iwamoto]

Hmm. I spent money on a chatter tool, so I can make those waves..... You may consider leaving them on. Just a thought.

[Reed Gray]

Okay, yes, for sure it is the edge of your plate flexing as you apply tool pressure to the rim. There is not enough wood to support it during the cut to keep it from flexing. This seems to be a bit more of a problem with plates than bowls. If you are getting the screeching, I would guess that you are using a scraper flat on the tool rest. This type of cut will put more pressure on the wood than a shear cut. It is also a lousy finish cut as it will leave more tear out unless you are cutting end grain. You need to support the outside of the plate as you make the finish cuts. I don't think there is a steady rest for plates/platters, so you need to use your hand. Some times taking it down to final cuts in stages helps a bit. First, and MOST IMPORTANT, make sure you round over the edges of the rim. If you don't, the sharp edge is like a razor saw, and can slice you to the bone quicker than you can say whoops. You can round over by cutting with your tools, or use abrasives.

For this finish cut, I prefer a scraper in shear cut mode, which means with a fresh burr (I usually use one straight from the grinder, or if you want fancy, a burnished burr), and up on its edge at a 45 or higher degree angle. Left hand is very gentle on the outside, and right hand holds the scraper. My thumbs are usually touching to help coordinate the move. This is a very gentle pull cut, and it will take several passes to remove tool marks. You can't get it all in one pass. Hand pressure on the outside of the bowl is the same amount of pressure as you are using with the tool. If you are pushing too hard with your support hand, it will get very hot very quickly. Also, if you are pushing too hard with your support/steady rest hand, you can deform the plate walls, just like too much tool pressure can. This cut can be done with a gouge if you drop the handle, but I found it more difficult to control, and I just like scrapers.

robo hippy

[Keith Westfall]

I did the center first, then worked my way out the to rim.

By doing this you have less support in the middle and more weight out. May cause you some problems as well...

[Chip Sutherland]

This is a great thread for newbies. Great question and great responses. Robo Hippy always has good responses. Harmonics can occurs on bowls, too. In the extreme, that can cause a thin-walled vessel to fail (fracture or tool catch) if not damped with a finger or something. As a general rule, one I turn the rim on a platter or bowl, I don't re-visit it with any tools.

[David E Keller]

...David, when you are referring to a single wheel as a steady, what do you mean?

I thought I had seen this somewhere before... Here you go:

http://www.sawmillcreek.org/showthread.php?130287-Steady-Rest-Opinions

Look for Leo's post at about number 12 or so... There's a picture of what I had in mind.

[James Combs]

You will want the wheels of a plate or platter steady to be orientated like this. This plate/platter steady attaches to my bowl steady but it could be designed as a stand alone. The wheel mounts pivot to keep the wheels perpendicular to the axis of the plate's rotation.

192728

[Chip Sutherland]

Wow, I have never seen that type of setup for platters. I have a great bowl steady already. How about a close-up shot? I need to noodle on it some more. I've got a 20" piece of honduran mahogany that I've been itching to turn thin for piercing. This would be ideal support to hopefully get it even thinner.

[James Combs]

Wow, I have never seen that type of setup for platters. I have a great bowl steady already. How about a close-up shot? I need to noodle on it some more. I've got a 20" piece of honduran mahogany that I've been itching to turn thin for piercing. This would be ideal support to hopefully get it even thinner.

Chip, I don't want to shanghai Joe's thread so a PM has been sent to you.

[Richard Jones]

......I've got a 20" piece of honduran mahogany.......blah, blah, blah......... That classifies as the Stealth Gloat of the Week, at least in my book.

Rich

[Doug Wolf]

Robo said: I don't think there is a steady rest for plates/platters, so you need to use your hand.

Here is one I made after looking at the Oneway spindle steady rest.
It can be used as a spindle steady rest or by remounting the roller blade wheels on the square tubing be used as a plate steady rest. Rollerblades are found cheaply at Goodwill.

192792
192793192795192794
192796

[Reed Gray]

That now makes 2 versions I have seen, both through this thread. Good idea. I don't turn super thin, and learned to use my hand as a steady rest before I knew what a steady rest was.

robo hippy

[Joe Vincent 63]

Thanks everyone for the great ideas! I'm going to try starting from the edge and working my way towards the center while using my hand as a steady rest when required. I really appreciate the thought put into these responses.

Robo Hippy, excellent safety information regarding the edge of the spinning platform. I do have one question regarding the 45 degree orientation of the scraper ... do you mean scraper on its side edge and slanted at 45 degrees such as is normal for a planer cut using a skew - at an angle like this / (versus flat but handle put down and scraper edge put up 45 degrees?

Joe

[Joe Vincent 63]

That is simply an amazing set up!

Joe

[Bernie Weishapl]

I use a oneway bowl/platter steady when turning and it does help. One thing is to start from the outside edge and work your way to the center a little at a time. I think it was Leo that told me to do the outside rim first and complete it. Then work your way to the center a inch at a time measuring the thickness as you go. That way you have the center which is still thick to support your work as you go.

[Reed Gray]

Joe, correct on having the tool on its edge at 45 or more degrees. If you dropped the handle, while keeping the blade flat on the tool rest, that is an invitation for a huge catch/launch.

robo hippy