Turning a taper, which is the prefered method?

[Tozguy]

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.

 

[Tozguy]

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.

 

[Robert LaLonde]

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

 

[Tozguy]

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.

 

[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.

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]

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?

 

[petertha]

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]

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.

 

[Ray C]

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]

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.