Metal Lathe Chatter - Need advice/opinions

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mikemac

mikemac

Member
Joined
Sep 4, 2006
Messages
269
Location
Ottawa, Ontario, Canada.
Hey there.

Maybe a metal lathe guru has some advice for me... Today I started turning a pen mill sleeve, and started getting some 'chatter' that left quite an undesirable pattern on the rod.

The extended length of the rod is approx 7 inches, .500 diameter, and I'm only taking a 0.005 cut, using a slow feed speed & rpm.

Any suggestions? I just honed the cutting bit, and the tailstock is tight.

Bit too high? Too Low? Wrong Angles?


chatter1.jpg


chatter2.jpg
 
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Increase the rigidity of your setup will get rid of most of it.
Lighter cuts will help you here. .005/side is quite a bit if you are not rigid.
Sticking out 7 inches is a loooong way. Try shorter stock lengths if possible.
Try a follow rest if you must stick out of chuck so far.
Try less radius on the tool bit.Sharper is better for less than desirable setups.
Try increasing your chip load.(increase feed, or decrease speed).
Get rid of that cutoff tit, and sink a good center seat in the end for l.c.
Try micro adjusting the bit height, as you mention. A few thousandths can make
a LOT of difference in a dicey cut. A shim pack works well if you are finding the
adjusting screws too coarse to have good effect.
Hope something helps! You got some nasty chatter.:bye:
 
I used to have that problem. Nice patterns though:biggrin:

Things to check that can get rid of it.
1. Increase feed rate.
2. If your machine is robust enough, increase depth of cut
3. Clamp the topslide ways if you're only using the cross slide
4. Clamp the cross slide ways if you're only using the topslide.
5. Upgrade topslide base from two bolt to four bolt.

Quick check for tool hieght; Lightly clamp a small steel rule between cutter and workpiece. If the rule is held perfectly upright, then the tool hieght is correct.

Hope this helps:wink:
 
John is right, of course, I was hoping I could make a LONG cut, but with a mini lathe like mine, it just won't work. Changed the overhang out of the chuck, and turns smooth as butter. I had just ground a new toolbit, and thought that might have been the problem, but now its cutting beautifully. Awefully addictive, this metal turning. I'm saving for a mill, but that may take a while.
 
mikemac said:
Hey there.

The extended length of the rod is approx 7 inches, .500 diameter, and I'm only taking a 0.005 cut, using a slow feed speed & rpm.



chatter2.jpg
Click to expand...


I would try shortening the stick out as much as possible either by running the excess stock through the chuck or cut off a section just long enough to make the sleave.


Chuckie
 
mikemac said:
Thanks, Chuckie.. I WAS hoping I could turn 2 at a time, end to end, but I'll guess I'll have to stick to 1 at a time :p
Click to expand...

Go ahead and try the longer stock, leave part length X (2) + .25".
Turn one half, flip around, turn other half.
Split length on saw or part in two when done.
You get the benefit of extra length to hold, and making 2 parts on your stock.
You lose very little by splitting.
Maybe this will work for you, maybe not, I find it to be a timesaver.:)
 
Mike, A few suggestions, some already mentioned...
- shorter s.o. from chuck
- deeper/bigger center hole
- much greater relief angle (@ the front of the tool). Presently that edge is nearly parallel to the work, creating a lot of tool pressure. Your lead angle is okay and looks to be about 15* Grind the relief angle about 75* to the lead angle and a .015 to .030 tool nose radius.
- try 200 - 300 rpm and .003 to .005 feed
- make sure the tool is on center. A real easy and accurate method is to just face off a piece of stock in the chuck. It's real easy to see where you're at. (you'll have to swivel the compound using the tool shown). Than make a gage to check your center height. Here's the one I made for my old SBL........
lathegage.jpg
 
mikemac said:
John is right, of course, I was hoping I could make a LONG cut, but with a mini lathe like mine, it just won't work. Changed the overhang out of the chuck, and turns smooth as butter. I had just ground a new toolbit, and thought that might have been the problem, but now its cutting beautifully. Awefully addictive, this metal turning. I'm saving for a mill, but that may take a while.
Click to expand...

When you do get a mill get a Taig, best small mill on the market , Or if your pockets are deep enough go for a Tormach. $2000.00 for a CNC Taig or $8,000.00 for the Tormach http://www.tormach.com/Product_PCNC_main.html
 
bitshird said:
When you do get a mill get a Taig, best small mill on the market , Or if your pockets are deep enough go for a Tormach. $2000.00 for a CNC Taig or $8,000.00 for the Tormach http://www.tormach.com/Product_PCNC_main.html
Click to expand...

Wow.. that Tormach would be nice... but unfortunately, with my current employment status, its WAY out of my budget. I'm likely looking at something like this:

http://busybeetools.ca/cgi-bin/picture10?NTITEM=CT133
or
http://busybeetools.ca/cgi-bin/picture10?NTITEM=CT129N
if I can somehow find the cash... :befuddled:
 
Mike, that's about the same mill as the Rongfu I've heard some folks that have them like them and they can be CNC'd the are pretty sturdy mill for the money!! a friend has a Tormach I love it, I'm still using my Taig, I never had any idea I would be putting it through the use I do, I bought it for doing jewelry masters just figuring on cutting machinable wax, was I ever wrong, it's an amazing machine, I'd like to have a Tormach, but I'm in about the same shape as you, and since I don't play the lottery, I guess I'll have to wait till the next life.
 
mikemac said:
Wow.. that Tormach would be nice... but unfortunately, with my current employment status, its WAY out of my budget. I'm likely looking at something like this:

http://busybeetools.ca/cgi-bin/picture10?NTITEM=CT133
or
http://busybeetools.ca/cgi-bin/picture10?NTITEM=CT129N
if I can somehow find the cash... :befuddled:
Click to expand...

I have the first one, sold by any number of companies around the world, popularly known as the X2 Mini Mill/Drill.

There's heaps of mods done by people, including CNC.

The mini-lathe site has a section on these mills as well.

Nice little mill for the money and reasonably cheap entry to milling.
 
Most tips I know already said. I agree with the sharper tool, and bumping up the feed rate and depth of cut. You said the tail stock was tight, do you use the quil lock handle? I have found that most of the time it works better unlocked. At least on the big lathes. I'll have a guy trying to cut something and come ask why they can't get away from the chatter. First thing I do is unlock the tail stock quill, and after they look at me like I'm nuts as I walk away, then they start to cut, and..........I had a 7x10 once. Not a bad little lathe once you figure out what their limits are.
 
I usally drill the hole in the stock first then set my tail stock in it. I also use a sharp carbide triangle type bit and han't had a issue doing it this way.
 
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