Gunsmithing Lathe Chatter; using PTG action jig for tenon/chambering.

[Gene Poole]

I got one of Viper's action truing fixtures as I've heard they are nice for doing short barrels on my long (18 inches or so--22 with the chuck) spindle (https://shop.pacifictoolandgauge.com/index.php?main_page=product_info&cPath=5_28&products_id=1457) and it is a nice solid fixture, but I'm getting chatter while cutting both tenon and threads. I believe it is all that unsupported length hanging off in space. I had to slow down to about 175 rpm to do the cuts and it took forever. I usually do threading at 175, but I had to drop to 64 rpm and still got chatter. Any clues?

Should I try a live center in the bore? I dial in the bore to within a tenth or so, but I know my tailstock is about 2 tenths off in the z-plane.

Setup for tenon work (Click for hi-res):


Notice chatter on the threads and also where I tried to cut some relief at the shoulder (click for hi-res):


The action fits great:

 

[JJones75]

I would say it is due to being a non rigid setup , it is stout yes but its nothing like only being 1.5" off the chuck.
I made a fixture for a buddy that locks into the D6 out of a piece of 10" OD 7075 aluminum and it is way more rigid that a jig held by the chuck (just something to conside)
I'd say you can either make lighter passes or slow it down. When threading small or flimsy stuff I actually prefer to use a piece of Rex95 with a bit of rake on the front and leading edge and hone it razor sharp and that helps a bit.

 

[Aeon1]

my tailstock is about 2 tenths off in the z-plane.

You must mean in the Y-axis (vertically up/down) because lathe tailstocks move parallel to the ways on the Z-axis and are adjustable in the X-axis. The spindle determines the Z-axis.

Looks like an old South Bend, if so I'd guess the old babbit bearings have too much play to run that much overhang in your setup. Put an indicator on the outboard end of the fixture and see how much you can move it by hand.

Oh, if it's only 2 tenths off then why not use it for support.

 

[nzgrip]

Probably the unsupported muzzle, centered on the bore doesn't mean balanced.

 

[Gene Poole]

It's a 1966 SB13 with very little use
. I recently adjusted the bearings to spec (0.0005 - 0.0015) by peeling layers off the shims. I got it to 0.0008.

I've really never known what the axes were called on a lathe. On a mill it would be the Z.

Will a tailstock quill flex enough or will it force the barrel out of line? The barrel bore is dialed in tighter than the quill runout.

 

[wnroscoe]

You have way too much material hanging out in front of the chuck. No matter what you do your going to get work piece flex and chatter.

In order to turn, thread and chamber the right way, with out chatter, you need an outboard spider and get the work area of your work piece closer to the chuck.

 

[msalm]

Make a unitized fixture with a new backplate and that fixture attached directly to it. I made one w/ a 1" thick 6" diameter flange bolted to a backplate and don't have any problems. I've made several of these and used heavy walled DOM steel for the tubing portion. I have 5 or 6 steel discs yet if you need one. I had them water jetted out of a piece of scrap, 1" thick, 6.25" diameter and a 1.5" hole on the middle to save on machine time. I bore a recess 3/4" through for a press fit of the tubing, weld on the outside and inside edge, then true up the backside, machine to fit a trued backplate, bolt together, mount on lathe and true outside surfaces and bore the inside concentric. Works great.

 

[300sniper]

Do the tenon and chamber end in the chuck before you cut the blank.

 

[Aeon1]

I've really never known what the axes were called on a lathe. On a mill it would be the Z.

If it's inline with the spindle it's the Z-axis. The cross slide determines the X-axis on a lathe.

Will a tailstock quill flex enough or will it force the barrel out of line? The barrel bore is dialed in tighter than the quill runout.

Once the barrel is dialed in where you want it, carefully (sharp tool, light cuts) cut a 60° center in the breach end with the compound and a boring bar. Then use your tailstock to support it to cut and thread the tenon. If your tailstock is anywhere near as close as you say I highly doubt you will have any problems. Use the steady on the tenon threads to finish boring the chamber before final reaming (assuming you pre-bore and ream). If not and you use the finish reamer for the whole chamber just ream.

 

[Bob Pastor]

I got one of Viper's action truing fixtures as I've heard they are nice for doing short barrels on my long (18 inches or so--22 with the chuck) spindle (https://shop.pacifictoolandgauge.com/index.php?main_page=product_info&cPath=5_28&products_id=1457) and it is a nice solid fixture, but I'm getting chatter while cutting both tenon and threads. I believe it is all that unsupported length hanging off in space. I had to slow down to about 175 rpm to do the cuts and it took forever. I usually do threading at 175, but I had to drop to 64 rpm and still got chatter. Any clues?

Should I try a live center in the bore? I dial in the bore to within a tenth or so, but I know my tailstock is about 2 tenths off in the z-plane.

Setup for tenon work (Click for hi-res):


Notice chatter on the threads and also where I tried to cut some relief at the shoulder (click for hi-res):


The action fits great:

Hi Gene,

That is my fixture. You don't have too much material sticking out of the fixture. What you are doing is turning way to fast for this particular operation.
Use the same speed that you would chamber with. That should be 70 rpms. If you have the barrel tight in the fixture, it doesn't make any difference
wether the muzzle end is supported or not. Your bearings have been adjusted and that is a plus. How are you turning threads at 175 rpms. with a good sulfur
based cutting oil and not filling up your shop with smoke? Are you using HSS threading cutter? HSS insert? or carbide?

Bob Pastor
1-269-521-3671

You can call and I'll try to help.

 

[dakor]

I have that same fixture and I thread between 70 and 115 rpm and have not had an issue since my new lathe. Did you dial the fixture in when you set it up in the chuck? You may want to give Bob a call he might have some idea's for you to try. 1-269-521-3671

 

[Bob Pastor]

Hi Gene,

That's my fixture and I can help you. I tried to post to you earlier in the day but It hasn't come up yet. First of all, you have just the right amount of barrel
sticking out of the fixture. I can tell by your threading that you are accomplished in this department. The unsupported end of the barrel makes no difference
in the stability of your set up until you go super sonic with your turning speeds. I see by your original post that you like to thread fast (175 rpms.) I do hope you are using carbide for those speeds. If you are using HSS and grinding your own bits, they must be razor sharp. Also a high sulfur cutting and chambering oil should be used.
Try to enjoy the lathe time and just slow down a bit. You should be threading at the same speed you chamber at (70rpms.) with HSS reamers.
Once you exceed 150 rpms. with any metal tube or rod that is unsupported and is not straight, you can't help but get some vibration, especially in a smaller machine with less mass. Adjusting your bearings was a good thing. My fixture will do what it's designed to do, within the limitations of the tooling, operators ability and nominal speeds.

If I can help any further please call: 1-269-521-3671

Bob Pastor

 

[FCrifles]

Just curious, is your threading insert full profile? Are you feeding straight in with the cross slide or compound? 29.5 or 30 degrees?

Partial profile insert, 29.5 degrees, feeding with compound will work best on the smaller lathes. Lots of good Viper oil too.

ALL of Bob's products are great. He is also one of the nicest fellers you'll ever meet.

 

[Gene Poole]

I have that same fixture and I thread between 70 and 115 rpm and have not had an issue since my new lathe. Did you dial the fixture in when you set it up in the chuck? You may want to give Bob a call he might have some idea's for you to try. 1-269-521-3671

I dialed in the fixture to within 2 or 3 thou as best I could ascertain, what with the flats on the sides. Then I dialed in the barrel bore directly with a long-reach DTI styus. I suppose I could slow down some more, but I'm used to cutting 416 SS at 500 rpm or more. Any slower and I get a lot of gummy cuts (with carbide inserts) or my bit dulls before I make a full pass (with sharp HSS).

Hi Gene,

That's my fixture and I can help you. I tried to post to you earlier in the day but It hasn't come up yet. First of all, you have just the right amount of barrel
sticking out of the fixture. I can tell by your threading that you are accomplished in this department. The unsupported end of the barrel makes no difference
in the stability of your set up until you go super sonic with your turning speeds. I see by your original post that you like to thread fast (175 rpms.) I do hope you are using carbide for those speeds. If you are using HSS and grinding your own bits, they must be razor sharp. Also a high sulfur cutting and chambering oil should be used.

I use your Viper's Venom for cutting. I love that stuff. I'm using a full profile 16TPI carbide threading insert (I run the carbide at 275 or so when I can). I guess I could slow down; after all, I'm in no big hurry, but my experience with the carbide inserts is that the faster the better.

Try to enjoy the lathe time and just slow down a bit. You should be threading at the same speed you chamber at (70rpms.) with HSS reamers.
Once you exceed 150 rpms. with any metal tube or rod that is unsupported and is not straight, you can't help but get some vibration, especially in a smaller machine with less mass. Adjusting your bearings was a good thing. My fixture will do what it's designed to do, within the limitations of the tooling, operators ability and nominal speeds.

If I can help any further please call: 1-269-521-3671
Bob Pastor

Thanks Bob. I'll get a hold of you later. We've exchanged PMs on Practical Machinist before. Thanks for the advise.

Just curious, is your threading insert full profile? Are you feeding straight in with the cross slide or compound? 29.5 or 30 degrees?

Partial profile insert, 29.5 degrees, feeding with compound will work best on the smaller lathes. Lots of good Viper oil too.

ALL of Bob's products are great. He is also one of the nicest fellers you'll ever meet.

Bob is a great guy. As I mentioned above, we've conversed in the Practical Machinist forum.

I'm using a full profile carbide threading insert. I have the compound set at 29.5 and I feed all but the last thou or so from the compound.

 

[300sniper]

I am still curious why you are doing the breech end in a fixture sticking some 6 inches out of your chuck.

 

[JJones75]

I am still curious why you are doing the breech end in a fixture sticking some 6 inches out of your chuck.

I think the idea is to eliminate the need for an outboard spider in case your through bore is tiny or the head is to long to use a spider.

 

[MDM]

^This. I had a similar experience when working on a 15" pistol barrel chambered in .260 Rem. I don't have Bob's fixture but made one similar and welded it to a back plate. I'm working on an old Heavy 10. Long story short, I finally figured out I was getting too much deflection when tool came in contact with the work piece. I'm curious how much deflection Gene is getting. Like it was pointed out, put a dti on the end of the fixture and see how much deflection there is when you push on it by hand. My bearings were within spec too. I ended up putting a live center up against the piece and that made it work with no issues. I'm threading at 50 Rpm and chambering at 80.

 

[Bob Pastor]

Good Morning Gene,

We need to get you a really sharp HSS insert from The Arthur R. Warner Co. You can thread up to 120 rpms. and always get a clean thread.
I now see the Carbide insert you are using. You were correct in using it at higher speeds but carbide inserts are never really razor sharp due to how they are produced. I'm going to bet that the person who taught you is a machinist and worked in production for some time.
You always have an open invitation to visit The Lathe Cave. I have what you need, if you want to come visit. I'm just North of you a few hours.

Bob

 

[Gene Poole]

I am still curious why you are doing the breech end in a fixture sticking some 6 inches out of your chuck.

As I mentioned in the first post, I don't have enough barrel to make it to the outboard spider on this SB13 with it's long spindle. For muzzle threading, I can thread an extension onto the breech end to get the extra length. I considered using a sacrificial muzzle thread and an extension on the muzzle end, but my blank is already short (27 inches) and I don't want to lose any more than I have to. Since this is for my own use, I'm probably going to leave it as pictured above since the receiver fits fine and the chatter marks are just cosmetic; we'll see how the chambering goes.

 

[Gene Poole]

Good Morning Gene,

We need to get you a really sharp HSS insert from The Arthur R. Warner Co. You can thread up to 120 rpms. and always get a clean thread.
I now see the Carbide insert you are using. You were correct in using it at higher speeds but carbide inserts are never really razor sharp due to how they are produced. I'm going to bet that the person who taught you is a machinist and worked in production for some time.
You always have an open invitation to visit The Lathe Cave. I have what you need, if you want to come visit. I'm just North of you a few hours.

Bob

I'll look into the HSS threading inserts. You're right; I had a mentor that was a machinist for Olin/Winchester (here in East Alton) for 20 years or so, then a machine shop supervisor for another 10-15. He made me grind everything out of HSS blanks before he'd let me touch carbide.

 

[Cigarcop]

Gene, you'll like the Warner tools, they are very well made and extremely easy to resharpen... they are a pleasure to deal with too!

 

[Twisted300Win MAG]

Gene. Is your spindle threaded? If so I made a spider for the outboard side as close as I could get to the edge of the bore. Then took a 3.5" back plate turned a shoulder on it. Next I took a piece of 4" 1018 bar stock and bored it for a press fit to the back plate, pressed them together and welded. Mounted it to the spindle and turned it true add some jacking bolts. I can work on both ends of a 23.5-24" barrel. Ill try and snap some photos when I get home.

 

[AKONA]

I think carbide is not needed and normally it likes higher speeds and a harder material.
Try a 5 to 8% cobalt HS tool at the slowest speed. They have them already profiled or you can make one with the grinder. The angles are simple for a threading tool.
It will work better at lower speeds, cuts will be smoother and most likely chatter will go away
But I agree that fixture seems too long. I made my own that is 6 inches and 8 bolts only and made of steel. It works like a charm and I can dial it to dead zero runout.
More times than not less becomes more in the end.

 

[fastshooter03]

So you dialed the bore to .0001" or so and the tailstock is only out by .0002" ??? Very nice.
I see a little chatter on the minor of the threads but that's all I see.
Unless you're gettin chatter on the thread walls I wouldn't worry about it.
Maybe cut that fixture in half though.
I've never needed a fixture like that. You said it was for holding short barrels?

 

[Bob Pastor]

The fixture can be used for truing up Remington actions, chambering barrels and it allows you to chamber a barrel as short as a pistol barrel.
It allows you to make all your alignment adjustments from the headstock side, instead of reaching around to the outboard spider.
The fixture is 4"'s in diameter and 7"'s long and does not flex.

I don't know how to post a photo with the post. If you go to www.viperbench-rest.com and click on the products button, you can see how it's used for truing actions.

 

[JJones75]

The fixture itself will not flex but the farther away you get from the bearings the more "flex" you allow.. if you set up an indicator on the back side of the jig and push on it you will see that their is a lot of "flex". Now do the same thing on the side of the chuck and you will see why threading a barrel locked down in the chuck if far more rigid.
The same thing applys for deep hole boring , the part and tool both flex due to the cutting point and chucking point being far away from their base.
I'm not knocking the tool at all just saying its no where near as rigid ad a chuck , this can be helped somewhat by using sharp cutters and maybe a live center in the chamber end on the barrel.
Personally if it were me I'd shorten the jig so that the rear screws are maybe 3/4" off the back of the chuck and have the flats machined so that the adjustment screws are between the jaws , this will move the part back closer to the bearings

 

[wnroscoe]

It's a nice set up and Mr. Pastor is very passionate about his work. I use indexable carbide and prefer to turn/face at 750 rpm+, thread at 242 rpm+ and chamber at 242 rpm. I use a chamber flush other wise I'd chamber at 70-80 rpm. I pre-chamber with carbide roughing reamers at 420 rpm BTW.

I cant imagine threading at 70 rpm, YAWN, I'd fall into the machine once I feel asleep.

 

[chipsfan]

Good Morning Gene,

We need to get you a really sharp HSS insert from The Arthur R. Warner Co. You can thread up to 120 rpms. and always get a clean thread.
I now see the Carbide insert you are using. You were correct in using it at higher speeds but carbide inserts are never really razor sharp due to how they are produced. I'm going to bet that the person who taught you is a machinist and worked in production for some time.
You always have an open invitation to visit The Lathe Cave. I have what you need, if you want to come visit. I'm just North of you a few hours.

Bob

Those high-speed steel insert threaders are fantastic. I use them at 220 RPM and they run like a champ. I run vipers venom for my rough cuts and tap majic for my final pass. Brownells sells the kits from Warner for the same money but you get their return policy.

 

[Bibs Machine]

I agree 100% with JJones75 there is nothing wrong with your fixture but it is to long to do what you are trying to do with it. All you need to do is run the chamber end on a live center. Make sure you cut a good 60 degree center in the end of the bore after you get your barrel dialed in before you do any other machining to it.That way it will run true with your live center in it,and it will make your set up ridged and it will stop all of your chatter. If I were doing it I would chamber the barrel first then run the live center in the chamber and do the rest of the machine work to the tennon.

 

[JJones75]

Probably the unsupported muzzle, centered on the bore doesn't mean balanced.

I had completely over looked this post and this is a very valid concern. The muzzle end hanging free in the bore could cause some vibrations which wil resonate though your piece. I often have to "bush" a shaft in the bore to keep vibration down with sometimes having 3'-4' on the outboard side!!.
A simple fix would be to make some plastic or nylon bushing the same OD (few rhou smaller) than your bore with a hole in the middle that will slide up and sinch down on the OD of the barrel.
This is actually how Hall of fame bench rest shooter and world record holder Don Geraci cuts his barrels. He uses a bushing in the bore that is really tight on the barrel then dials in with the chuck (3 jaw set true)

 

[AKONA]

I had completely over looked this post and this is a very valid concern. The muzzle end hanging free in the bore could cause some vibrations which wil resonate though your piece. I often have to "bush" a shaft in the bore to keep vibration down with sometimes having 3'-4' on the outboard side!!.
A simple fix would be to make some plastic or nylon bushing the same OD (few rhou smaller) than your bore with a hole in the middle that will slide up and sinch down on the OD of the barrel.
This is actually how Hall of fame bench rest shooter and world record holder Don Geraci cuts his barrels. He uses a bushing in the bore that is really tight on the barrel then dials in with the chuck (3 jaw set true)

This might work if the work is perfectly true and centered to the bore. But unfortunately this is not the case many times and that is why a spider, 4 way chuck or fixture is needed to adjust in both axis and make the threads
and chambering perfectly centered and true to the bore.

 

[JJones75]

This might work if the work is perfectly true and centered to the bore. But unfortunately this is not the case many times and that is why a spider, 4 way chuck or fixture is needed to adjust in both axis and make the threads
and chambering perfectly centered and true to the bore.

I agree , the first few times I watched him do it I could not believe what I was seeing!!
Crazy thing is he holds a 3/8" guarantee at 100yds with non mags and hand loads , most shoot in the .2's
I've argued that crazy old coot up and down but its hard to argue with results.
Not saying its a good idea , Just saying its done.

 

[DAVETOOLEY]

I agree , the first few times I watched him do it I could not believe what I was seeing!!
Crazy thing is he holds a 3/8" guarantee at 100yds with non mags and hand loads , most shoot in the .2's
I've argued that crazy old coot up and down but its hard to argue with results.
Not saying its a good idea , Just saying its done.

Hey don't pick on my old friend Don. The Raging Cajun. We talked just a few weeks ago. God we've had some good times together shooting BR.

 

[AKONA]

I agree , the first few times I watched him do it I could not believe what I was seeing!!
Crazy thing is he holds a 3/8" guarantee at 100yds with non mags and hand loads , most shoot in the .2's
I've argued that crazy old coot up and down but its hard to argue with results.
Not saying its a good idea , Just saying its done.

If he knows what he is doing (most likely the case) will have a perfect cut so probably have everything running dead on.
When folks buy profiled barrels unless you dial from the bore an correct, one will end up with a very sloppy chambering job and accuracy will suffer.
Even CNC machines make mistakes and specially CNC when things are done in a hurry!! LOL

Rule nr. 1: measure
Rule nr. 2 measure
Rule nr. 3. meausre again.

LOL.

 

[fastshooter03]

If the contour is running concentric to the bore, let her rip.
It's amazing what will shoot good.
I set back a couple of factory rem700 308's and the chamber on one was out .007".
Set back .150" IIRC to 308 match and threaded/cleaned up the muzzles and they were more than happy with the results.
The chamber on the worse one didn't even clean up but they were claiming one ragged hole @100 on both.