Profiling a barrel blank

I am a machinist in northern Alberta Canada.
I am looking to do some of my own rebarreling work on the side.
My question is in regards to the specific tooling that will work the very
best for cutting the contours/profile of the barrel. I would also like to know
The best process for supporting the barrel during machining.
I took a night course where we used hand ground high speed steel cutters, taking a .020" depth of cut and I resolved then to find a better way.

I realize there are people who will suggest to me that I should buy my barrel bank already profiled by another and save myself the hassle.
While I respect that I want to learn how to do it.
Thank you all for any suggestions.
( my first project was a 6.5-.284 Norma)

I do not know if you have access to U.S. magazines, but if you do. The last issue of Machinist Workshop June/July 2011 Vol.24 , Number 3 has a complete several page article on just that subject. The author takes a Bull barrel and profiles it down, showing complete tools, rests and procedures. Reprint sales dept. shows an e-mail of [email protected]
or www.villagepress.com/workshop/ I hope this helps.

Back when I actually used to do such things, used my H.E.S. Tracer lathe and HSS tools ground for axial thrust rather than radial. IE close to 90 degree lead angle and lots of rake in a chip breaker parallel to the cutting edge.... straight out of the Henry Ford Shop text of the 1950's.

Cyclotronguy

We had a Graziano lathe setup with a tracer specifically for turning and profiling barrels.

If I started with a rough blank, I turned a chucking point between centers on the breech end. Profiling was done between a three jaw chuck and a spring loaded live center in the tail stock. Flood coolant was used to keep the cutter cool and a lead weight sometimes rode the barrel near the cutter to prevent chatter near the center of the cut.

Carbide insert tooling is the modern alternitive to HSS.
Even the inexpensive five piece triangular insert tool kits with screw down inserts work ok.
Actualy they are a good choice for the small lathe, the insert is ground with a positive rake and chip breaker, which reduces the power needed to cut.
The down side is you use a special screw to hold the inserts in place, and the heads round off. The answer is to identify the threads and order a box of countersink screws.
They are a lot cheaper than the special screw head and work just as will in my experiance.

My experiance with the cheep brazed inserts that look like HSS tools is they are a total waste of time and effort.
Spend the money for at least a mid ranged HSS insert or stick your better off with HSS. Poor boy this and you get poor results.

The upside to carbide is its harder and more ware resistant.
Down side is its more brittle and cant support as highly angled and edge as you can get with HSS.


The issues with barrel profiling are simple:
1, chatter and deflection of the part.
2, actualy producting the desired profile

Chatter is usualy delt with useing a combination of feed rate, spindle speed and extra support in the form of a follow rest riding just in front of the cutter. The suggestion to use HSS ground to reduce radial thrust to a minimum is actualy a very sound. Most carbide inserts have a small tip radius that creates quite a radial thrust load and makes it hard to control deflection on long limber parts like barrels.

Producing a profile other than a long taper repetably requires a CNC machine or a way to follow a profile, such as a tracer lathe. A couple of other options inclue eye balling it, and modifying a tapering attachment to follow a template.

A while back I came accross an extra compound for one of my lathes. I stripped the lead screw out of the compound and added a small lever to push it in and out. Adding a small stylis to follow a template creates a crude manual version of a tracer attachment. Simple and effective.

If you are doing a one of turning as more of a hobby and learning experiance, I thing the best advice is to invest in several rolls of 1" abrasive strip in a variety of grits. Odds are you wont get everything right the first time and will need to do a lot of pollishing to hide the chatter.

Cyclotronguy said:

Back when I actually used to do such things, used my H.E.S. Tracer lathe and HSS tools ground for axial thrust rather than radial. IE close to 90 degree lead angle and lots of rake in a chip breaker parallel to the cutting edge.... straight out of the Henry Ford Shop text of the 1950's.

Cyclotronguy

Click to expand...

Making sure I understand you, the lead angle would be exactly parallel to the chuck, and having a generous amount of positive side rake angle?
Thanks for all the responses by the way. They were are helpful.

I have absolutely no practical experience with barrels.
But from a machine & tooling perspective, a person could do worse than use a planer with a milling head for long skinny stuff held between inclinable, rotating centers. Adjustable supports (rests) can be contrived if necessary without too much trouble

The machine would allow round, hex, octagon, fluting; also straight taper and hyperbolic tapers generated by work position W/rsp to cutting tool (table) travel. Using a simple flat plate with a profile cut/ground/filed into it, it would be easy to mechanically trace.

This could also be possible on a large horizontal with inclinable rotating centers. The planer would be easier to use for rifling, though.

Contour it on the planer, polish it on a lathe.

Or bite the bullet and get a cnc lathe. But then you give up the non round options...

smt

Send me an email kente*at*passlabs*dot*com.... will repsond with JPG