Tool chatter

Totally new to metal turning on an engine lathe. Bought an inexpensive
(read cheap Chinese) Grizzly machine which is about all I really need
for my hobby type projects but - seems to me I'm getting way more
chatter trying to turn stuff than even this machine should produce.
I'm trying to turn a grooved disk, 3" in diameter. I faced off a piece
of stock (in a three jaw) and turned about 2" reasonably true. Then
took an old carbide cutter my brother gave me, looked something like a
thread cutting tool, and ground the end to about a 3/8" radius. On a
green wheel, of course.
If I 'touch up' the tool on the ginder, go back to the lathe, I'll get
a really nice curly chip off the stock at first then the tool will
start to chatter and I'll get a whole mess of little semi-circular
shavings, if you will.
I've checked and rechecked the tool for center and it's as close as I
can get. This chatter occurs with or without lube. (Using Lennox
ProLube applied manually).
Am I just asking more of this lathe than it can produce? It's the
12x36 Grizzly gear head model.
Reply to
Dennis Shinn
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Probably too big of a radius on the tool. It should be "pointed" but with a tiny bit of radius, not a sharp point. You've got too much contact between the part and the tool. Also try increasing the chip load on the tool by slowing the relationship of the rpm to the feedrate. In other words feed faster at the same rpm or use slower rpm at the same feedrate. Randy
Reply to
Randy Replogle
What Randy said, but if it's a new lathe and you're new to it make sure that you've taken out the lash on the ways, cross slide and (if you use it) the compound. You should tighten the gibs until the horizontal feed won't move, then back it off until you can still feel some resistance. Do the same for the cross feed and compount.
That won't necessarily fix things, but if you have things too loose there it _will_ chatter. Rigid tools chatter less.
Reply to
Tim Wescott
Dennis Shinn wrote in news: snipped-for-privacy@4ax.com:
In addition to what the other two fellas have posted, make sure you keep the tool tip as close to the toolpost as you can. If you have to shim the tool up, make sure the shim (if it's thick enough to matter) goes out to near the end of the tool, this provides more support.
Reply to
Anthony
Thanks for the tips, Randy
Reply to
Dennis Shinn
I haven't run one of the 12x36 China imports, but I've read numerous owners' comments which were favorable about those lathes.
You received some excellent suggestions concerning chatter, which you can usually count on when you ask questions in the RCM forum.
For the 2 Asian machines that I have (bought 1 new, 1 used), both of them produced less chatter after I checked that the spindle bearings were fully seated, and had adjusted them for a little preload. The correct preload is especially important when turning parts that are only supported by the chuck, IMO.
I dunno what the 12x36 model's bearing preload should be, and maybe it's OK. Adjustment might require some experimentation, and I suppose the best guideline is that the bearings shouldn't get hot when the spindle is test run at one of the higher speeds. On the loose end of the spectrum, the chuck shouldn't coast excessively when spun by hand (with everything else disengaged from the spindle).
If I were trying to groove a 3" diameter piece, I'd try to cut the groove with a thinner cutting tool.. a 3/8 radius groove is a lot of tool edge contact. I've roughed out grooves as big as 1/2" radius (and depth) with a smaller cutting tool (although I use HSS), and finished the groove with files to get a smooth radius (for tubing bending dies, for example). For cutting a pulley groove for a V-belt, the same rough turning is SOP, then the sides of the V are finish turned 1 at a time by advancing the compound feed set to an appropriate angle.
I also use the Lenox Pro Tool Lube applied with a dispenser bottle or brush, and find it to be a good all-around cutting lube for machining small parts. I particularly like that it rinses off with water, and that steel parts aren't especially susceptable to rusting even after water rinsing.
WB .............
Reply to
Wild Bill
Fortunately I have a friend (of a friend) who's an accomplished machinist who was kind enough to drop by the shop and give me a crash course in turning hard stuff (harder than wood, that is -grin-). Turns out I had way too much tool in contact with the work surface for the machine. It seemed big when I bought it but I've since visited a couple of shops that had some "real" lathes (hahaha). So, learned that when turning a groove like I wanted, best to cut with a pointie tool into something close then use the profile cutter to finish up.
None the less, I appreciate everyone taking the time to reply.
Reply to
Dennis Shinn

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