# Turning a taper, which is the prefered method?



## HRgx (Jan 5, 2018)

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?


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## kd4gij (Jan 5, 2018)

Taper Attachment  hands down.


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## Ulma Doctor (Jan 5, 2018)

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 

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


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## Tozguy (Jan 5, 2018)

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 (Jan 5, 2018)

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.


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## Wreck™Wreck (Jan 5, 2018)

Ulma Doctor said:


> 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!
> ...


On a good day you will turn a taper without effort, the more important question is how do I not turn a taper.


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## Ray C (Jan 5, 2018)

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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## Ulma Doctor (Jan 5, 2018)

Wreck™Wreck said:


> On a good day you will turn a taper without effort, the more important question is how do I not turn a taper.


good point!!!


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## Robert LaLonde (Jan 5, 2018)

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


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## petertha (Jan 6, 2018)

Tozguy said:


> 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?


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## Tozguy (Jan 6, 2018)

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 (Jan 6, 2018)

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 (Jan 6, 2018)

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


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## Tozguy (Jan 6, 2018)

Ray C said:


> 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).
> ...



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 (Jan 6, 2018)

Tozguy said:


> 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.


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## petertha (Jan 6, 2018)

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 (Jan 6, 2018)

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.


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## Ray C (Jan 6, 2018)

petertha said:


> 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.







Ray C.


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## Ray C (Jan 6, 2018)

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.


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## petertha (Jan 6, 2018)

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 (Jan 6, 2018)

petertha said:


> 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.


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## petertha (Jan 6, 2018)

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.


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## Wreck™Wreck (Jan 6, 2018)

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 (Jan 6, 2018)

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!


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## Tozguy (Jan 7, 2018)

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!


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## Tozguy (Jan 7, 2018)

Ray C said:


> 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?


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## Ray C (Jan 7, 2018)

Tozguy said:


> 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.


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## Tozguy (Jan 7, 2018)

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


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## Ray C (Jan 7, 2018)

Tozguy said:


> 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.


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## epanzella (Jan 7, 2018)

Tozguy said:


> 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)


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## 7milesup (Jan 7, 2018)

I wonder if a tangential tool cutter would help with any chatter issues?


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## Robert LaLonde (Jan 7, 2018)

Tozguy said:


> 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?




I just used a hand ground vertical shear yesterday to take the finish pass on a 10" long 416 tapered shaft.  It works ok, but I found slow rpm, slow feed, small depth of cut.  Just a couple thousandths.  Its really only good in my opinion for finish cuts. 

Its not hard to grind.  Just give it a little relief angle behind the edge.  Stone the edge to make it as sharp as its possible to make.

A vertical shear will even make the finish on low C steel "better."  Better being a relative term.


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## Tozguy (Jan 7, 2018)

7milesup said:


> I wonder if a tangential tool cutter would help with any chatter issues?



That is what gave me the best results so far in the test piece. The tangential bit has positive top rake and is easy to keep sharp. This was not on a full length barrel (see pics above) but I plan to try it when the time comes.


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## petertha (Jan 9, 2018)

Tozguy said:


> 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. ... 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.



I'm getting ready to pull the trigger on this hardware. I got thinking about the MT3 arbor again. Maybe a tang type would be a beneficial thing over tang-less. If it engages tailstock as its intended, then the only remaining problem is reliably orientating the boring head so it its extending horizontal. But I'm wondering if that would just be a matter of appropriate shim washer between the head & arbor. Once you figured out the correct thickness, it would be permanent & hopefully every time you re-installed into tailstock it would be the same, no?

Also, wouldn't normal chuck direction serve to be tightening the boring head threads vs. loosening? 
** oh wait, are they reverse threads ? **

Another question, I envision making a 60-deg dead center from 0.5" stock (or whatever matches the appropriate boring head tool shank). What is the miracle grease people recommend for dead center friction work like this?

I looked for something that would be a mini live center with straight shank (vs dead center) & don't think it exists. Taking apart or otherwise trying to turn down a stock taper shank seems like a PITA although the one fellow did exactly that on YouTube vid. Any other ideas?


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## Tozguy (Jan 10, 2018)

In my tailstock there is nothing for the tang to engage. Even if there was, my tests convinced me that the normal traction of a good MT taper is more than adequate. I prefer the simplicity of using a line level on the boring head to get it level then tap it into the quill until it is seated. Periodic checks with the level during my test runs did not show any movement whatsoever.

There is one surefire way to back up the MT taper and that is to put a clamp on the nose of the quill once the taper is set normally. See the third pic below.

With the muzzle end of the barrel at the tail stock, the boring head is set out towards the operator. Cutting forces tend to lift the barrel which puts  a slight torque counter clockwise on the boring head. With vibration and time however it is enough to work the head loose on its threads if there is no locking mechanism. They are right hand threads. It obviously it takes much less torque to unscrew the boring head than it does to slip the MT taper. Even the slightest rotation of the boring head would have a drastic consequence on the cutting action.

When working between centers it is important to account for any heat build up in the barrel. This heating will expand the barrel and the centers will become too tight, possibly to the point of bowing the barrel. If this is left unattended there is no quality of grease that will work on centers that are binding.

I have been using quality white grease formulated for bicycle wheel bearings on a ball centre in the boring head. 60 deg pointed centers would have a harder time of it because they do not work as well at a slant. That is the reason I use a ball centre for turning tapers. Maybe someone else has a grease to recommend but there is no guarantee that it will work as well when the a pointed centre is set at an angle.

I have never seen a small enough live centre that could be used in a boring head whereas making up a couple of ball centers would be fairly straightforward. Please ask if would like to know more about making some.


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## petertha (Jan 10, 2018)

Very good info Tozguy, thanks.

- I'm still not comprehending the clamp pic, they look like they are on the tailstock barrel. isntthe unscrewing issue between the boring head & threaded arbor? (red arrow)

I like that bearing ball concept. II have a model engineering book (George Thomas?) where he describes exactly that. there is a relationship to ball size & 60-deg center depth, but that would appear to take care of hardness & the swivel+rotation movement simultaneously. 
- How did you retain the ball (like locktite, silver solder...0 and what kin dof divot is on the backside that it engages in?
- do you have a series of ball centers like at progressive diameters?
- out of interest, did you ever try those special elliptical center drills (or whatever the curve profile is) specifically intended to work with conventional 60-deg dead centers?

If I was choosing between 2" or 3" boring head, any pros & cons you can think of? 3" is a bit more beefy, sticks out further has slightly more deflection range but guessing either should satisfy most typical arbor tapers I'm doing. 3" uses larger tools, 2" is I believe 0.5" shank. Do you find you can get to your carriage dials ok under the head or do you have to keep the compound at a certain position?


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## Tozguy (Jan 10, 2018)

The collar clamp I referred to is the one closest to the boring head. It is on the nose of the quill. It provides extra hold on the MT3 taper by compressing the front of the MT3 socket after the arbor is put in place. It does not secure the boring head on its arbor in any way. The other clamp to the right is mounted on the tail stock body and is used to prevent the quill from moving. For normal operation it is left loose so the quill slides in and out of the TS with no binding.

The unscrewing issue was solved by drilling and tapping the boring head for a set screw into the middle of the threads. Visible in the pictures.

A 5/16'' ball was used for 6mm bores and a 3/8'' ball for 30 cal. bores. The sockets (divots) for the ball were cut round to hold exactly 1/2 of the ball. I had a 5/16 round Dremel cutter on hand but I had to buy a 3/8 cutter for the larger ball. The balls were glued in with liquid Krazy glue. There is a slight cone cut on the shoulder surrounding the ball to provide relief for the barrel. 

The size of the balls was limited somewhat by what cutters are readily available.The balls have to be bigger than the bore but not too big.
To get a 60 deg contact ring on a ball just chamfer the bore slightly with a centre drill. For example, a 5/16 (.3125'') ball inserted in a 60 deg centre divot will have a contact ring .270''in diameter. So a .243'' bore would have to be chamfered out to at least .270'' to get a good fit.

I am not familiar with special elliptical centre drills, what is special about them?

I chose a 2'' boring head with 1/2'' holes because I already have 1/2'' shank boring bars, they have sufficient adjustment range and they were on special at BB. There has been no special clearance issues when using this set up. 

I hope i understood your questions properly.


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## petertha (Jan 10, 2018)

Thanks for concise reply.
re the funky center drills that assist taper turning, I'm not sure if I named them properly as elliptical (an uneducated guess).
Bell or type-R maybe? (I suspect the KBC is an incorrect stock picture of regular center drill.)


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## Tozguy (Jan 11, 2018)

Interesting, thanks, I wonder if anyone watching has tried these.

I don't see how they could work when there is a bore to contend with, if the bore is larger than the pilot on the drill.


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## petertha (Jan 11, 2018)

I’m no expert but I think the way they are supposed to work is same principle as your ball end dead center. In conventional turning, a 60-deg dead center point exactly aligns to 60-deg center drill hole. Now when you offset the work for taper turning, it’s no longer aligned & coincident cone within a cone. The dead center can only partially contacting an edge of the angled part. I think a curved center drill profile is intending to provide better contact to linear 60-deg center tip, which remains aligned parallel to bed axis. But I’m still fuzzy as to how much more contact, or if the objective is more-so to get contact it inside the cone as opposed to the lip? I can visualize a ball though, its spherically curved so it has to be making a full circle contact line and inside even a conventional 60-deg center drill profile. Then again the cutting force is only pushing on one side of the center drill / support. The book I have draws this out, I’ll have to take a peek again.


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## petertha (Jan 13, 2018)

I've been thinking about this some more. 

Here's some sketches showing a conventional 60-deg center drilled part. I just used #4 center drill geometry but they are generically similar through size progression. The turned part itself is angled at arbitrary 5-degrees in top view, just to show exaggeration in offset tailstock taper turning mode. And then showing 2 styles of tailstock support centers - a typical 69-deg cone and a ball ended profile. The dimensions aren't important, more just a visual thing. Here are my eyeballing observations, see if you agree.

It seems to me that the 60-deg support can only have one point of contact. Either on the lip end of the part or possibly the inside corner where the smaller pre-drill transition. And I think 'point' is the right term (viewed in mid plane horizontal section view). It cant be a line if there is any offset. That can only occur when axis are coincident. There may be one unique setting where the center is supported by both corners mentioned, but that doesn't help us much & probably isn't desirable.

The ball end support superimposed inside the 60-deg center drill cone has a resultant 'circle' as a tangential ring constantly in contact. I drew it up in 2D just to confirm the geometry satisfies this & it does. The tangent contact occurs in slightly different positions (red arrows). I was having trouble 'mating' the parts in 3D but that was probably just me. Actually the ball would work for any angle like 45-deg chamfer, just showing 60-deg for similar comparison.

So now add tool cutting pressure to one side of the parts arrangement & a bit of wear on whatever makes contact. Seems to me the ball has to be better. Its spreading that side imposed load on at least half the tangent arc. The 60 cone within a cone is concentrating all that pressure on one teeny point area. What do you think? Am I barking up the wrong tree? 

Some other points to ponder

- re the special curved profiled center drills. I don't know what kind of curve they have so cant really draw them up. But I could visualize where they might have similar connected ?circular? contact similar to the ball. At least they would prevent  potential interference with the pilot drill. But this presumes you can actually drill your part. In the case of gun barrel this might not me an option, or not without a secondary lopping off operation.

- a 60-deg live center in a 60 deg hole. What's happening here? Its kind of teh same point contact thing but maybe better? The part would drive the center even though not on the same axis, kind of like bevel gears in principle? If so, that might be an improvement over 60-deg dead center. (But more work to integrate a live center bearing assembly into a boring head used for offset.

- and thus far we have been talking about the tailstock end. But seems to me the exact same geometry issue is happening at the headstock side if its got a typical dead center & drive dog arrangement. The relative part-to-dead center doesn't care that the displacement is higher at the TS end, its the same angular difference the 2 axis on either end, no?


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## Bob Korves (Jan 13, 2018)

I am pretty sure that the offset angled 60 degree setup will give two points of contact.  The ball center will indeed have a full ring of contact.  Yes, it is the same issue at both ends of the work.


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## whitmore (Jan 13, 2018)

petertha said:


> It seems to me that the 60-deg support can only have one point of contact. ...Seems to me the ball has to be better. Its spreading that side imposed load on at least half the tangent arc.... seems to me the exact same geometry issue is happening at the headstock side if its got a typical dead center...



The 'dead' center might be tilted to make the 60 degree work better (you're already
offsetting it, adding a tilt knuckle is relatively benign).   The beauty of the ball center is
that it tolerates any tilt (but at the headstock, the driven ball swings against the work
according to the spindle rotation, it'd have to be a LUBRICATED ball for
a ball center there).


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## petertha (Jan 14, 2018)

Bob Korves said:


> I am pretty sure that the offset angled 60 degree setup will give two points of contact. .



You mean here & here Bob?


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## Bob Korves (Jan 14, 2018)

petertha said:


> You mean here & here Bob?


Yes, exactly.


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## Tozguy (Jan 14, 2018)

Peter, those drawing are very helpful, each worth 1000 words.
As whitmore mentioned above, there is a slight difference at the headstock in that the barrel will rock slightly on the ball so lubrication is required there too.
At the tailstock end the location of the contact ring on the ball, although it is tilted, is constant.
Thinking about all this helps me appreciate why 60 deg. is chosen for centers as opposed to any other angle.


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## Tozguy (Jan 14, 2018)

Bob La Londe said:


> I just used a hand ground vertical shear yesterday to take the finish pass on a 10" long 416 tapered shaft.  It works ok, but I found slow rpm, slow feed, small depth of cut.  Just a couple thousandths.  Its really only good in my opinion for finish cuts.
> 
> Its not hard to grind.  Just give it a little relief angle behind the edge.  Stone the edge to make it as sharp as its possible to make.
> 
> A vertical shear will even make the finish on low C steel "better."  Better being a relative term.



Bob, I just did some testing with a shear bit and concur with your comments.
On a 416SS, 1.125'' dia. test piece at 235 rpm, feed of .003''/rev and .010'' doc, using cutting oil, it cut very freely. Chips were wispy. No smoking of the cutting oil and the HSS tool stayed sharp the whole time. The tool has 5 deg relief on the nose and the cutting edge is slanted to roughly 20 deg. with zero rake.Finish was just what I need. Interesting! 
It remains to be seen how this technique would work on a longer work piece but I am optimistic.


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## Tozguy (Jul 26, 2018)

Just got done cutting a long taper between centers. A tangential tool holder worked best. Am very happy with the results. Did the job with an MT3 boring head offset by .158'', a conventional center in the headstock and a ball center in the boring head. No intermediate support was used and once I found the right DOC, speed and feed it cut very smoothly with the chips carrying the heat away.


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## Tozguy (May 10, 2019)

Just an update on my second barrel. This time I wanted to try offsetting the TS. A live centre was tried first in the TS but it was too bulky. Finally an MT3 end mill holder was used with a DIY ball centre. The ball bearing floats in the centre and a grease fitting is provided so the ball can turn either in the barrel or in the centre.
A very sharp HSS-Co bit was used in a tangential holder. A follow rest was cobbled up using a auto lug bolt and nut. A spring loaded 520 motorcycle chain was used to put constant pressure on the barrel.
The first 5 inches of the cut was done without the follow rest. After the first 5 inches the lathe is stopped and the rest installed.
It is very important to add some extra drag on the barrel to prevent chatter and patterning.  Cutting fluid was brushed on heavy.
Care needs to be taken to adjust the centres when heat builds up in the work and to keep chips out of the follow rest but all things considered I would do it again this way.


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## mikey (May 10, 2019)

Ever heard of the Bowers Taper Turning Attachment? Made by Bowers of the UK and marketed here by Royal.


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## Suzuki4evr (May 10, 2019)

HRgx said:


> 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?


Friend if you have a taper attachement why NOT use it. I wish I had one. I don't know how long it takes to set up,but if you can't use the compound for too long  distance reasons, then the taper attachment is the way to go. Not so sure about your steady rest idea.


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## jbobb1 (May 10, 2019)

I'm working on making a taper offset tool. Got the plans off the internet.


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## Tozguy (May 11, 2019)

Suzuki4evr said:


> Friend if you have a taper attachement why NOT use it. I wish I had one. I don't know how long it takes to set up,but if you can't use the compound for too long  distance reasons, then the taper attachment is the way to go. Not so sure about your steady rest idea.



To me the crux of the matter of profiling a long rifle barrel is to prevent deflection. Regardless of which of the above approaches is used to set the taper, there must be a mechanism to prevent deflection of the barrel during the cut.


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## Titanium Knurler (May 11, 2019)

Can’t contribute much to the conversation on deflection but I thought I would show you a nice Royal tailstock offset device I picked up used on eBay. It is exceptionally well made and incorporates some of the desirable features mention in this thread: a ball-end center and spirit level as well as a chart for setting the offset for various barrel lengths:





Unfortunately they are no longer manufactured but there are lesser versions available from China:


TK


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## Janderso (May 11, 2019)

I had no idea there were so many tailstock tools to assist with taper turning.


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## Tozguy (May 11, 2019)

TK that Royal is in a class of its own.
Wondering what the two dark rings on the cone mean. Would that be a carbide ball tip on the centre?


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## Titanium Knurler (May 11, 2019)

Tozguy, yes, the Royal is a tool that is a pleasure to hold in your hand(probably not the best voice of words).  The rings were on the tool when I got it and are fortunately just superficial wear marks.  I am not sure if the ball tip is carbide but the center is “live”.

Just to, maybe, add a little something to your discussion regarding displacement, I did some tests a while ago to get an idea of what kinds of radial forces cause what kind of displacement of a workpiece. To do this I took a 1-1/2”, 12” MT5 standard rod that was placed directly in the spindle, a 1-1/2” Thomson rod mounted in a 4JC and a 1” Thomson rod in a 5C spindle chuck and pushed on them with a force generator at 0”, 6” and 12” from spindle and measured the displacement.  Here is the set-up for the 4JC and the results for all three rods:







So, just looking at the 4JC at 0” from the spindle, there was no displacement until a 100# force was used; this caused a displacement of only .0002”.  At six inches from the spindle a 15.5# force caused a displacement of .001” and at twelve inches from the spindle only 4.4# caused a displacement of .001”.  How does this relate to real life?  Not sure, but I did do some “live” experiments where I cut a rod unsupported by the Tailstock and measured the displacement while cutting.  For example, with the one inch Thomson rod in the collet chuck at twelve inches there was .005” displacement which translates to about 13# of radial force under the cutting conditions I was using.  If 13# of radial force is a reasonable ball park figure for a light cut you can go back to the chart and look at 13# for each rod and distance and get an idea of the displacement you will see.  Bottom line: Tozguy,  I think you are correct that support is key to getting a good cut, secondly, I obviously had too much time on my hands the day I put this stuff together.

TK


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## Flyinfool (May 11, 2019)

Those 2 dark rings look like wear lines. Oopie!

I may have to make me one of those contraptions. It is such a PITA to get the tail stock back in the middle after off setting it.

I have only ever turned one barrel for my 6.5x55 Mauser. I did the taper with HSS cutters and just using tail stock offset. Yes I can measure that there was some deflection in the middle, the calculated center dimension is about .013 oversize, but the eye can not see it so it is good.
Since I planned to shorten the barrel by 4 inches I did not have to protect the muzzle during the tapper process. I used a center drill to make a good cone in the muzzle and then used a carbide dead center in the tail stock with a good load of wheel bearing grease. I just used very slow and shallow cuts to avoid climbing. At the end I did 5 or 6 spring passes to straighten it out as much as possible.


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