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How do you manage turning thinner barrel contours?

MattiJ

Titanium
Joined
May 31, 2017
I'm curious about experiences what everyone is using to turn something like sporter profile without insane chatter?
For sure not everyone has a hydraulic following rest so what tricks or method do you use?

High rake HSS or some specific carbide inserts? Lead hammer? Changing feed rate and/or rpm for each pass?
 
I use pneumatic follow rest, modified reg follow rest with pneumatic cylinders and offset tailstock to cut taper, tooling varies from sharp sharp handground carbide or HSS and .015R sharp edge insert, rpm still has to be played with. Normally I can start at 400 rpm .050 per side cut when blank is still large, then down to 190 rpm and .010 per side smaller barrel gets, adjust pressure from 80psi to 40 psi, that will vary on cylinder size also. still very much a PIA , but It is worlds better than not having follow rest, for sporter weight from 1.25 blank prob takes me an hour, but, I can't walk away from it, still get spots that chatter and have to tweak it. Also,I do blending and final finish on barrel spinner not lathe. Any better methods I am interested in also.
 
Anyone experiment with tool height?
Seen someone recommend (HSS) tool slightly below center and the opposite, (insert) tool slighly above center so that insert edge is sort of supporting the workpiece.
Sometimes it seems that everything changes the chatter behaviour so kind of makes sense..
Letting the HSS tool to rub is probably no-go as it would heat and wear out.
 
I use pneumatic follow rest, modified reg follow rest with pneumatic cylinders and offset tailstock to cut taper, tooling varies from sharp sharp handground carbide or HSS and .015R sharp edge insert, rpm still has to be played with. Normally I can start at 400 rpm .050 per side cut when blank is still large, then down to 190 rpm and .010 per side smaller barrel gets, adjust pressure from 80psi to 40 psi, that will vary on cylinder size also. still very much a PIA , but It is worlds better than not having follow rest, for sporter weight from 1.25 blank prob takes me an hour, but, I can't walk away from it, still get spots that chatter and have to tweak it. Also,I do blending and final finish on barrel spinner not lathe. Any better methods I am interested in also.

1 hour sounds a lot considering that you have follow rest?
 
When I was in school we had to make three custom rifles and turn the barrels down from blanks. We did a low RPM 200-400 between centers only no rests. We used a hand ground, high rake HSS tool with a 1/8 rad. Took about .025-.05 per side. Took about 1 1/2 hours to turn it down. Once you get to desired size we filed the chatter out while still between centers. thandraw filed it to get the waves out of it. Than used different grit buffers to get the desired finish
 
I will repeat it is Pain In A** to profile barrels, smaller, thinner you go the worse it is. playing with tool type and tool hgt is constant, sharp tool is a must, small radius tip .005-.015 max. Much better than was before pneumatic rest, normally fairly easy on large varmint tapers, but sometimes one section of barrel will chatter out of the blue, and stop, slow down take lite cuts through that sections, then run full length again with lite cut. Chromy moly cuts much different than Stainless, heavier cut and faster rpm with chrome moly, but finish comes out better with stainless, still have to draw file to blend some places, but expanding drum sander with 60 or 80 grit to start with cleans up alot, then work down to 320 or 400 grit. Much cheaper and easier to buy contoured blank. I am offsetting tailstock between centers, I am sure true taper attachment is probably somewhat better. Any better ideas or advice I am certainly open for myself.
 
Even if I were doing it as a hobbyist instead of for profit (at least, that's the plan) I'd never profile a barrel (manual lathe). Time is still money either way.

For $35, I can draw a purty picture of whatever custom contour I want and have the barrel manuf do it. Longer lead time, but who cares...
 
Hello,
Chatter is a true test of your ingenuity and patience. Filling the bore with #9 lead shot, and adding wooden plugs to keep them in place will help a lot. Adding a follower rest to the mounting position that most lathes have, or a dovetailed cross slide. I had the honor (?) of cutting 8 pitch acme threads on some 1.5"x 48" lead screws with a follower rest that used a pair of maple blocks mounted to arms that were mounted to an upright post. the top arm was weighted in front pushing down, while the lower arm being longer was weighted at the rear end pushing the bottom block up to stop the tendency to climb over the tool. I am in agreement about the high positive rake hss(m43) tool with a radius. Enough radius is needed to prevent the corner from wearing away, and to help the finish without adding an increase in up thrust from too much radius. If you have clearance on the ends, using a tool as above having a 45 degree leading edge sometimes reduces cutting forces. Shallower depths of cut can help to reduce stress and warpage. Start the cut and go make some money while it runs a cut, until touching a limit switch to activate an alarm.
Best regards and good luck,
Bob Queberg
 
Way back in the mid sixties, as an apprentice at Firestone, one of the machinists brought some brazed carbide to the tool grinding room, and wanted a 35 degree front clearance to allow setting the tool above center. He was turning long straight 4140 shafting. He "said" it worked great.
Regards,
Bob Queberg
 
Way back in the mid sixties, as an apprentice at Firestone, one of the machinists brought some brazed carbide to the tool grinding room, and wanted a 35 degree front clearance to allow setting the tool above center. He was turning long straight 4140 shafting. He "said" it worked great.
Regards,
Bob Queberg

Thats pretty extreme clearance angle, especially for sixties carbide!
Have to give it try sometime.
 
My dad taught me how to grind a tool similar to that that works great for hogging or very fine cuts. Best part is on a less rigid machine like mine, you don't generate a lot of back thrust in the crossfeed so it cuts on size and most times doesn't require a final spring cut. Mine looks a bit different. I grind the groove with a dremel cut off wheel along the long axis of the HSS blank, just up to the edge, leaving about a .020 land. The relief angles are ground and then the faces honed and a slight radius applied. I usually run the tool square to the work or with a slight lead and it generates a nice short curled chip. If the feed rate generates a long spring, a block can be clamped on to break the chip into shorter peices. I can't think of a tool that would have less cutting force.
 
I have run a barrel finishing with an anglegrinder fixed to the toolpost, easy way to get rid of the chatter marks.

Marko
 
Please be aware that if you profile turn a button rifled barrel, it can actually spring open and increase bore diameter. This is how Anschutz chokes their smallbore rifle barrels. After button rifling they turn most of the barrel down slightly and leave the muzzle end unturned, and thus smaller.

Cut rifled barrels don't have this effect I don't believe. (Apologies if this was posted in the thread previously)

Sent from my XT1053 using Tapatalk
 
Even if I were doing it as a hobbyist instead of for profit (at least, that's the plan) I'd never profile a barrel (manual lathe). Time is still money either way.

For $35, I can draw a purty picture of whatever custom contour I want and have the barrel manuf do it. Longer lead time, but who cares...

Easy for you when you don't need to pay exorbitant amount of money for shipping or wait 1 month for overseas shipping. Add to that the import hassle, lisences and permits.

35$ for pre-turned profile or charge the customer bit more if you do it by yourself without extra wait.
 
I'm having some trouble picturing the orientation of the tool. Is it supposed to feed backwards (from headstock to tailstock)?

A bit late but I believe the 2 views shown end to end are side views and on the angled view the lighter surface is the top of the tool.
 








 
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