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Turning a taper, which is the prefered method?

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HRgx

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#1
If I wanted to taper a shaft that is approximately 26" or so long. I'm thinking gun barrel blank here. Would it be best to use my steady rest and move it the the desired offset. Or, would it be best to use my taper attachment which guides my cross slide as required?
 

kd4gij

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#2
Taper Attachment hands down.
 

Ulma Doctor

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#3
i haven't ever had a working machine with a taper attachment, as a result i never really tried to turn tapers.
the idea of making an concentric and accurate taper, i thought was beyond my ability.

i was wrong!
i had to go by tailstock offset to reproduce an MT2 taper for a tailstock centerdrill holder, and it worked beautifully!

it would be nice to know different methods to do the same thing :grin:

good luck and please post the results, i'm very interested in any outcome :)
 

Tozguy

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#4
I have two barrels that need to be tapered and this is my approach.
I don't have a taper attachment. Practice on a barrel stub has been promising.
 

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kvt

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#5
I know on a mini lathe I have seen an offset able center for the tailstock. That way you could offset it the amount needed. Then turn between centers.
 

Wreck™Wreck

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#6
i haven't ever had a working machine with a taper attachment, as a result i never really tried to turn tapers.
the idea of making an concentric and accurate taper, i thought was beyond my ability.

i was wrong!
i had to go by tailstock offset to reproduce an MT2 taper for a tailstock centerdrill holder, and it worked beautifully!

it would be nice to know different methods to do the same thing :grin:

good luck and please post the results, i'm very interested in any outcome :)
On a good day you will turn a taper without effort, the more important question is how do I not turn a taper.
 

Ray C

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#7
The proper methods of turning a taper that long would be (in order of precedence):

1) Use a machine designed and dedicated for such a purpose.
2) Spin between centers with a tailstock offset (you'll need a cathead to support along the way).
3) Use a lathe with a taper attachment (most of them are limited to short travels of about 10-14 inches).
4) Inch along using the compound (buy 2-3 barrel blanks and maybe 1 will survive but still look ugly).

Regards

Ray C.
 
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Robert LaLonde

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#9
I picked up an offsettable tailstock center. Made my own lathe dog.

5033.jpeg
 

petertha

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#10
I have two barrels that need to be tapered and this is my approach.
I don't have taper attachment & I keep returning to this setup as what I should try. What prevents the boring head from rotating or is there just not enough twist force acting on the center? Does your MT arbor have a tang to engage the tailstock or is it tang-less?
 

Tozguy

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#11
The MT3 arbor is tangless. At first I had the same question and made a sleeve to lock the boring head to the quill.
After some tests it did not seem to be a problem. The MT3 taper holds very well on its own and was actually very difficult to eject from the quill.
The MT3 taper seemed to be less torqued than during some drilling operations. There is little offset and cuts are relatively light so the MT3 taper has an easy time of it. Of course the MT3 socket andarbor are in excellent condition. I do not use the locking sleeve anymore.
A more obscure cconcern is the boring head unscrewing on its arbor. A set screw was added on mine as can be seen in the first picture above.
 
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Tozguy

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#12
BTW when using one of the offset TS center approaches and you want to get fancy, make some ball centers instead of using the conventional 60 deg point center.
 
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Robert LaLonde

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#13
Either way grease the tail stock "center." Ball or 60 degree center.
 

Tozguy

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#14
The proper methods of turning a taper that long would be (in order of precedence):

1) Use a machine designed and dedicated for such a purpose.
2) Spin between centers with a tailstock offset (you'll need a cathead to support along the way).
3) Use a lathe with a taper attachment (most of them are limited to short travels of about 10-14 inches).
4) Inch along using the compound (buy 2-3 barrel blanks and maybe 1 will survive but still look ugly).

Regards

Ray C.
Ray, I am having difficulty relating those methods to the OP.
But for my similar project my only option is your 2), and I don't see how a cathead can be used when turning a barrel blank. In my case I have to turn a seamless taper of .910'' to 1.235'' over 18 inches with the o.a. length between centers being 23''. Deflection is a concern although there is no precision requirement, the operation is only for looks and weight savings. I plan to use a tool grind and DOC that will minimize deflection. This is with 416SS and the barrel will be Scotchbrited to the desired finished look.
 
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Ray C

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#15
Ray, I am having difficulty relating those methods to the OP.
But for my similar project my only option is your 2), and I don't see how a cathead can be used when turning a barrel blank. In my case I have to turn a seamless taper of .910'' to 1.235'' over 18 inches with the o.a. length between centers being 23''. Deflection is a concern although there is no precision requirement, the operation is only for looks and weight savings. I plan to use a tool grind and DOC that will minimize deflection. This is with 416SS and the barrel will be Scotchbrited to the desired finished look.
Assuming the bbl is 20-24" long it's going to flex like crazy in the middle. A cathead in the middle running off a support will still allow you to cut on either side of it (albeit a pain to tweak into position the second time). Once the taper is turned on both sides of the cathead, you'll have a spot that has no taper in the middle. To address that, using the same taper, you take a piece of roundstock, bore it then put a taper inside it that matches the outside of the diameter and taper near the middle of the bbl. Walk that piece over to the bandsaw and put a longitudinal split in it so it has "fingers". Slide it over the bbl close to the middle and put the fixture in the chuck. The remaining piece to be tapered will be near the chuck now. When you tighten the chuck, it will pinch the bbl and you'll be able to finish the remaining part in the middle.

FWIW, I've done this before. It's a pain but I think the best way of pulling it off in the absence of a dedicated machine or high end CNC lathe.

Regards

Ray C.
 

petertha

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#16
Dumb question, but is a cathead like a fixed steady? When I Google that I get lots of images that look like either (fully enclosed) spiders or open fixed steady's like below. Do you have a picture to elaborate? I'm still not getting how to traverse past it while taper turning, unless the contacts are in a specific orientation or you somehow interrupt the cut & then go back & blend it after the fact?
 

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petertha

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#17
One of the better vids showing boring head tailstock adaptation. I think I want to try this.
And actually now that I noodle upon this, it pretty much has to be tangles tailstock arbor unless you make some sort of collar to phase the boring head horizontal but that sounds both fussy & pointless based on what I see.

 

Ray C

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#18
Dumb question, but is a cathead like a fixed steady? When I Google that I get lots of images that look like either (fully enclosed) spiders or open fixed steady's like below. Do you have a picture to elaborate? I'm still not getting how to traverse past it while taper turning, unless the contacts are in a specific orientation or you somehow interrupt the cut & then go back & blend it after the fact?
Perfectly fine question... Here's a cathead. It supports a shaft in the middle and the outside of it can be grabbed by a steady rest.

And now, I realize Tozguy is right... You don't need a cathead if you're starting with a round piece of blank bbl. Some time ago, I changed the taper on a barrel that was already tapered -for that, you must have a cathead because a steady rest cannot stabilize a tapered shaft. In the case of a normal bbl blank, you can just use a steady rest. You still need to make the taper holder though.



1515260775860.png


Ray C.
 

Ray C

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#19
Part II of reply.

Once you have a steady rest employed, the setup has to be disturbed to cut on both sides of it. Not desirable but, there's no way around it.

There are CNC lathes that have a center rest that automatically move along with the cutting bit. Such machines have price tags out in fantasy land. I can almost guarantee that rifle bbl manufacturers have dedicated machines whose sole purpose is to taper barrels.

Next time you get the chance, take a 24" long shaft at least 1" in diameter and try to take a skim cut. Don't even try it with less than 1" diameter -too dangerous. No matter how light you go (even with sharp HSS), it will look terrible and it will bow in the middle. If you try to dig in, it will catch and jump up on top of the cutter -I can practically guarantee this. If you're lucky, when it jumps on top of the cutter, the TS end won't pull out of the tailstock tip and the shaft go flying around and beat your machine up. (ask me how I know this).

Ray C.
 

petertha

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#20
Thanks Ray. I'm still not getting how you could travers cut through the cathead area (or maybe that's just not possible & I'm still not getting it). I figured if an open frame steady had tangent contact points like sketch of cross section, you might get away with it. Although you would still have to reset the fingers with every cut.
 

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Ray C

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#21
Thanks Ray. I'm still not getting how you could travers cut through the cathead area (or maybe that's just not possible & I'm still not getting it). I figured if an open frame steady had tangent contact points like sketch of cross section, you might get away with it. Although you would still have to reset the fingers with every cut.

There's a steady rest and a follower-rest which are 2 different things. Your picture is showing what a follower rest does. Those attach to the carriage and support the spinning shaft and follow along as you cut. That works fine for a non-tapered shaft. When the shaft is tapered the diameter is constantly changing and the follower will not self-adjust itself to remain in proper contact.

You cannot traverse the cut on either side of a steady rest. You can work on the left or right side and to switch sides, you have to break the setup and re-establish it.

On a tapered shaft, if you're going to use a stead rest, you need to use a cathead to proved a flat surface for the bearings or contact pads to ride on. There are problems with this too... you have to grind flats where the cathead bolts will touch otherwise, the grip won't hold (for long).

Either way, yes, you're left with an unfinished spot that has to be smoothed over. That is where that tapered-bore shaft comes into play.

Ray C.
 

petertha

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#22
Ah, duh! Topside tunnel vision syndrome :)
The steady rest is occupying lathe bed real estate, the carriage cant traverse through that, hence the travel steady. But that's only parallel turning.
 

Wreck™Wreck

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#23
A cats head holding a copper tube in a steady. I place steel banding strips under the set screws so as not to mark the parts, for those without experience using a steady rest be aware that if misaligned it will walk the part right out of the chuck jaws, this will end in tears at best.
 

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epanzella

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#24
My first attempt at tapering a barrel was between centers and I just couldn't stop the chatering. It looked like I cut it with a hatchet. I made a small cathead to fit the blank and just kept sliding it down the barrel machining the first 6 inches at the 4 jaw end. I had to blend it with file and emery but it came out good. It's a PIA as I had to keep resetting the tailstock to keep the taper constant as the length of stickout changed. I ended up with a stainless afro! Lotsa chips!

BARREL COLLAR TOTALLY COMPLETED.JPG MACHINING BARREL BLANK CONTOUR 1.JPG zDSC_0875.JPG zDSC_0361.JPG
 

Tozguy

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#25
epanzella, interesting, would you please explain how and where the collar (spider?) was used?
If I am imagining right, the 4 jaw holds on the collar and the barrel would start far into the spindle bore and at an angle for the first section.
Then as stick out from the 4 jaw increases for each subsequent section the TS offset is reduced to pick up the taper from the previous section.
The angle of taper wrt to the bore axis would change slightly from one section to the next.
Bet you can clean a lot of pots with that SS wool!
 

Tozguy

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#26
Part II of reply.

Next time you get the chance, take a 24" long shaft at least 1" in diameter and try to take a skim cut. Don't even try it with less than 1" diameter -too dangerous. No matter how light you go (even with sharp HSS), it will look terrible and it will bow in the middle. If you try to dig in, it will catch and jump up on top of the cutter -I can practically guarantee this. If you're lucky, when it jumps on top of the cutter, the TS end won't pull out of the tailstock tip and the shaft go flying around and beat your machine up. (ask me how I know this).

Ray C.
Ray, thanks for driving the point home, it would simply be very poor practice to attempt to turn a long slow taper like that using a conventional tool without some sort of extra rest to support the work. However, this style of tool might be a hedge against the work jumping on top of the cutter.
http://gadgetbuilder.com/VerticalShearBit.html
Do you have any experience with this particular approach?
 

Ray C

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#27
Ray, thanks for driving the point home, it would simply be very poor practice to attempt to turn a long slow taper like that using a conventional tool without some sort of extra rest to support the work. However, this style of tool might be a hedge against the work jumping on top of the cutter.
http://gadgetbuilder.com/VerticalShearBit.html
Do you have any experience with this particular approach?
Matter of fact, yes I have. If I'm not mistaken, about 10 years ago, those pre-ground bits were being sold individually by someone. I have not tried them however. I'd say, give it a shot but, my instincts call out for a steady rest whenever I see something whose length is 20x greater than it's diameter.

If you've been following my other thread about the bullnose live center, you can probably tell that I'm a carbide guy. I use HSS when it's called for and many folks are wizards at grinding it and using it to cut metal. It really is a special talent (in my opinion) but the guys who are good at it, seem to take it for granted. If you want to give that a whirl, I'd suggest lots of practice with HSS using the same material as the bbl (SS, if I'm not mistaken). SS gives carbide a run for it's money and it must be tough on stainless too. In my pre-teens and teenage years, I used nothing but HSS but only on soft carbon steel. I've never cut SS with HSS bits.

When the current lathe setup is finished, I'll toss-in a piece of 316 (I've got boat shafts coming out my ears) and try cutting with HSS. We'll see what happens.

Nothing ventured, nothing gained....

Ray C.
 

Tozguy

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#28
Ray, thanks again for your thoughts. I have been cutting this barrel steel (416SS) for a few years now using carbide tools and HSS reamers.
It machines well enough and that might make all the difference in results compared to 316SS. Looking forward to reading about your tests.
https://www.crucible.com/eselector/prodbyapp/stainless/cru416rs.html
 

Ray C

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#29
Ray, thanks again for your thoughts. I have been cutting this barrel steel (416SS) for a few years now using carbide tools and HSS reamers.
It machines well enough and that might make all the difference in results compared to 316SS. Looking forward to reading about your tests.
https://www.crucible.com/eselector/prodbyapp/stainless/cru416rs.html
I love that website. Thanks for passing that along!

FYI: It might be a couple days before I try turning the 316 so hang in there.

BTW: If you enjoy metallurgy track down this book: "Heat Treater's Guide, Practices and Procedures for Irons and Steels" ASM International. This book mainly covers carbon steels but has some stainless info. There's a companion book covering stainless in detail. It's hard to find this book at a reasonable cost but sometimes, a used copy turns-up.

Ray C.
 

epanzella

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#30
epanzella, interesting, would you please explain how and where the collar (spider?) was used?
If I am imagining right, the 4 jaw holds on the collar and the barrel would start far into the spindle bore and at an angle for the first section.
Then as stick out from the 4 jaw increases for each subsequent section the TS offset is reduced to pick up the taper from the previous section.
The angle of taper wrt to the bore axis would change slightly from one section to the next.
Bet you can clean a lot of pots with that SS wool!
TOZ,
You've got it exactly right. Start with the collar a foot from the (temp) muzzle and cut that taper. Then move the collar 6 inches at a time while extending the stickout. The setup is only rigid near the chuck. At each move I stick a DI in the QCTP to dial in the taper, machine, then move on to the next 6 inches. As you probably gathered, you should cut the taper to full depth as you go. Going back to a part you tapered already would be a hassle. In the second pic you can see the center drilled brass muzzle protector for turning on centers. It has a 1" long stem that's .001 over land diameter and is driven into the bore.
PS. I almost forgot. The bore has to be concentric with the OD before you start tapering. The first thing I do is I take light truing cuts (no taper) on centers using a following rest to get the whole barrel true to the bore. (I'm just a weekend warrior so I don't have rods and bushings)

TRUING UP BARREL FOR MACHINING 1.JPG TRUING UP BARREL FOR MACHINING 2.JPG
 
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