How do you turn a barrel with out chatter?

[john.k]

I never got the finish I wanted from lathe turning,by rough turning and then into the Landis ,the ground finish was ideal to take the hot blue .........blueing doesnt want a mirror polished finish ,but a very smooth microscopically scratched one that reflects light in a particular way.

 

[animal12]

So how does that air steady / follower rest work ? Do you keep adding pressure as you turn ? Or just more air after a cycle / pass ?
thanks
animal

 

[john.k]

If you want to build an air cylinder device,find one of the old Westinghouse trailer brake valves off a WW2 tank recovery tractor.........these valves are all brass,and look really nice,just like the brake controll off a steam loco........if you cant find one,then any semi trailer brake controll pre electronics will work the same ......and you can find a 1960s/70s one for nothing ,usually.

 

[Springer]

Make yourself some replacement spring loaded followers for your travelling steady, the basic concept is the same as a spring loaded tap follower just with brass pads fitted instead of a point. I profile right down to light sporter contours between centers without any chatter running at 800rpm. The spring was a Barnard firing pin spring cut in half and it seems to provide adequate pressure, I would expect a Rem 700 spring would work just fine.







I would usually run the tool closer to the follower than this but on this occasion the set-up required this and again it worked perfectly.


I also run polished inserts for aluminium to take my final passes as they are very sharp and leave an excellent finish, 416 stainless is soft and these inserts last well in this application.

 

[cuslog]

Smallest nose rad. you can get.
I made a separate follow rest from 3/4" plate and did the "spring thing" - helped quite a bit.

 

[triumph406]

Using Kenametal DCMT3251LF KC5010Grade is my goto. The smaller the nose rad the less tool pressure. I tried to get VNMG to work for me but the negative geometry just makes for chatter.

Might have to try those inserts

Got some Anschutz 22LR match barrels that I've chambered that I need to turn from 1.25" dia to .920" diameter. Orignal plan was to turn to .925" dia, then get them centerless ground to size. (i use a guy who's very reasonably priced for centerless grinding)

But will try those inserts, see how they work out. May forgo the centerless grinding.

Will do them on a Graziano SAG14, which is still as tight as a you know what

 

[john.k]

I would think it impossible to get chatter with a 1&1/4" dia in any usable length........chatter usually sets in when youre getting down near 1/2" dia on a light sporter profile........any hoo ,you aint done chatter till you get the awful chatter screech on a big part in a horizontal borer ......a clever apprentice could arrange a shrieking tune on the borer ,until the workshop manager would be driven out of his soundproof office "enough" "enough"

 

[50BMG DUDE]

John,

I beg to differ, any barrel blank generally will chatter if the tool pressure is too high, the rpm is to high, the feed per rev is too high or low. Also depends if you are turning with a pre-qualified end in a chuck or collet or as we do usually a face driver on one end and a live center in the other. Many drilled blanks are way out at one end or another so throw an interupted cut into the mix. Also having that nice hole down the middle make things want to sing. I have seen chatter in barrel blanks that are deeper than most barrels are FLUTED.

When we started in the business I experimented with filling the bore with lead shot, compressing with a setscrew from each end, This helped immensely but is a major PITA. Bought an Okuma LB3000EX with variable harmonic spindle drive (used a couple parameters that set a bandwidth for the spindle RPM to go up and down and also the frequency. Sounded weird, but worked OK. Over the years we have shifted to the technique I described in a previous post.

 

[???]

Turned down and chambered a 98 barrel in 30-06 using a Boxford lathe with a fixed steady, super sharp HSS and neat oil in a army mobile workshop on the back of a Bedford, piece of cake. Nothing different to any other long slender job being turned. One thing I would be really careful of is inducing stresses in a barrel, if it's a precision target rifle it will walk the group across the target if there are stresses in the barrel. This is probably more of an issue in hammer forged barrels than buttoned or cut rifle barrels.

 

[CalG]

Damn! I guess just resting a hand held oily rag on the barrel while turning just doesn't cut it any more.

 

[???]

Damn! I guess just resting a hand held oily rag on the barrel while turning just doesn't cut it any more.

Maybe a piece of leather, rag is pretty iffy.

 

[taiwanluthiers]

we are trying to turn 1.25 dia. barrels with out chatter . can anyone offer some ideas ?
Thanks for the help.

Without seeing your setup it's hard to tell.

Chatter is basically caused by taking too heavy of a cut in a setup that isn't rigid enough for the cut.

So you are going to want to use steady rests if you are turning between centers, but better to just chuck the thing in a lathe as short as you can possibly make it, and also you want to support the other end with a live center.

Either that or your lathe isn't rigid enough...

Look at your setup if you have problems with chatter.