Crazy vibration turning pipe

[tyler774]

Hello all

Real stumped with this one. I have a part that is ringing like a bell and chatters like you wouldn't believe when I try to turn the O.D.

First I'll admit I don't do a whole lot of machining, so may be asking the impossible here.

Part is a roller made from a 30" piece of 3-1/2" sch 40 steel pipe, ( O.D. is 4" ). It has 1/4" thick end plates welded in the ends. The end plates were bored out for a 3/4" shaft prior to being welded to the ends of the pipe. The 3/4" shaft was then inserted down the whole length and welded to the end plates. Using carbide indexable cutter, ( DNMG432-mm ).

Pretty much ruled out the cutter, I get a real sweet surface finish on a short 5" chunk of this pipe, better than 20 micro inches by the looks of it. Mind you I was able to spin this short piece way faster, too afraid to try any faster than 450 RPM on the long part.

The part needs the O.D. diamond knurled as well, but got to get it turned true first!

And your probably thinking thats one ugly piece of crap, well it is. Wanted to get the hang of things on something cheap first. Got 20 of these to make for some slab rollers I'm building, ( type of pottery tool ). Will use new mat'l once bugs are worked out, might make them out of aluminum to if customers are willing to pay added expense.

2 things I will try are making up a roller 15" and giving it a try, 2nd would be filling up the tube with wax, sand, etc.. to dampen the vibrations.

Just can't believe the vibration, not sure if you can see in the pictures but it don't even look like turning, more like what you would get with a hammer and chisel, a series of scalops ripped out.
Any ideas guys?

Thanks

Tyler

[Lew Hartswick]

The first thing I'd try is a HSS tool bit with some top rake and about a
1/32 radius tip. How stiff is your cross slide and compound?
...lew...Oh, and high sulfur cutting oil.

[jpgdesigns]

May I suggest a different order of operations...
My suggestion would be to chuck the pipe in the lathe and use a live center cone for the tail stock to turn down and knurl the pipe supported by chuck and tail stock, then weld on the end caps. Next mount a steady rest on the lathe to support the pipe while you clean up the end cap weld and then drill the hole for the 3/4" rod... flip and repeat.

Just another way to "skin this cat"

[tyler774]

Lew, thanks for the quick reply.

HSS, Hmmmm. I have some blanks, will give it a try. By top rake, do you mean positive rake on the top of the cutter?

The lathe I got, well not the most rigid thing. Chinese gap bed bench lathe, 8" swing over the cross slide, 40" between centers. You bring up a good point, will see if I can tighten the gibs up. Can only help.

Thanks

Tyler

[tyler774]

Been pondering lot of different ways to make these.

Don't currently have a live center. Will be getting one soon though. Was also looking at those tailstock chucks Bison Makes. Would allow me to hold the end of the pipe on the inside with possibly more contact area.

Thanks

Tyler

[jpgdesigns]

you did have the tail end supported... right?
3/4" rod may seem strong enough... but 30" lever arm will bent that rod and if the tail end was very so slightly out of balance... that bugger would chatter like two old maids at a bingo game.

[tyler774]

jpgdesigns

Tail end is supported by dead center, and steady rest on the 3/4" bar. The more I think about it, I want to try turning the pipe before the end plates/shaft gets welded on. Actually, the shaft doesn't have to be secured by welding, can be keyed.

Tyler

[tyler774]

Got the problem solved.

Purchased a Bison tailstock chuck. Was able to get a real nice finish, a little chatter but can live with it. going to saw off the unturned portion, then weld on my end caps. Going to build a jig to hold cap concentric and square to the tube O.D.

Thanks to those who stopped by to offer advice, greatly appreciated.

[basalt]

I used to machine pipe pulleys and what I discovered was that if you drilled and tapped the end plate near the rim for a 1/8 npt pipe plug and partially filled the pipe with coolant it took care of the chatter. You can fill/drain the pipe by rotating it in the lathe. hope this helps. Two other things I've done for chatter are using a dead centre and turning the tool upside down. Hope this helps,good luck.
Colin
Oh, by the way we welded the end plates in before machining the pipe O.D.