Parting vs Saw Cutting

E

eww1350

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What is the percieved difference between saw cutting-off of the unused part of the rifle blank versus parting it off in the lathe...?
I have used both methods and can't see any difference in accuracy once the barrel is crowned properly..
 
I seem to remember an article in PS by Bill Calfee wherein he states that muzzles should not be parted off due to the heat generated causing the bore diameter to grow. I think he proved this to his satisfaction using the slugging method's he champions.

I don't know if the above is a definitive statement, but it sounded reasonable to me, so I use my bandsaw for such goings on now. Plus I hate parting tools...

For what it's worth,
Justin
 
The most used electric tool I own is a hand held band saw (Port-A-Band). I rarely use a parting tool.
 
I don't think either method matters... heat is not a problem with either.

It may be a different story if you used a chop off saw with an abrasive wheel send red hot metal down the bore and heating the metal melting red hot.
 
If the barrel is already dialed in the lathe from a previous operation, then I part and crown while in the lathe, if the sequence of operations is appropriate.

If the barrel is out of the lathe then I cut off using a band saw, much quicker than lathe parting, still have to dial in the lathe for final crowning cuts.

Neither produces enough heat to distort barrel if done with the proper lubes and feedrates....................Don
 
I don't like parting tools either, but use them to start a cut off at the proper dimension. Usually, I end up with a hacksaw in hand to cut off the offending piece of metal (while it is spinning in the lathe, of course). Just rock the saw occasionally to clear the chips. Then the crown is cut and finished...

Scott
 
Parting vs Sawing

Parting induces stress and changes the metal structure for about and inch on each side of the part. It leaves the muzzle with a constriction issue that sawing doen not leave.

Nat Lambeth
 
You Got To Be Kidding

I have never cut a barrel by any method but parting in a lathe.

I think some of the statements made in this thread are ludicrous...........jackie
 
I once was asked to fit a replacement barrel to a SMLE .303 for a guy who was off "hunting" a couple of hours later. I had a clean #4 barrel, but he didn't like the step down where the foresight fits, so I had to shorten it for him. Without access to a lathe, I marked where I had to cut with a pipe cutter snigged up really lightly & cut it off with a fine metal cutting blade I had at the time for a jewellers' piercing saw, rotating the barrel every few strokes. I draw filed the face of the barrel the same way to neaten it up & cleaned up the bore with a RCBS neck chamfering tool. :eek:

Cutting the new extractor slot was a bit of a bugger (the #4 indexes differently on the thread to the SMLE), as was slotting for an old 92 Winchester foresight & the ratchet rear sight off my Husqvarna .243.

Bedding was a piece of cake, as I did it in 5 minute body bog. :rolleyes:

The bloody thing shot (to his standards at least) right on the money at 100 yards after I'd boresighted it for him.

Oh, the days of innocence...
 
Agree to disagree

Jackie and others:

If you look at the metal structure under a microscope, have it ultrasound tested, magnafluxed, or Xrayed you would see what is being said in those test.

Parting is well known to cause a tight spots, small fractures, hard spots on both sides of the part.

A simple example is to look at copper or aluminum tubing that was cut with a tubing cutter. No matter how sharp your tooling is and how light our feed is it still pinches and distorts the metal in front and directly beside the parting tool.

I am glad you are happy using your parting tool. I am happy using a bandsaw and facing the muzzle with a tool bit. I am sure you are saying, what is the difference in parting and facing the barrel after it has been sawed. The stress on the barrel/muzzle is going against the bore when parting. The stress is going parallel to the bore with facing. The saw blade induces less stress around the cut surface than the parting tool.

This topic was discussed in great detail in our machining class. Our class went to an engineering firm that test metal and looked at metal cut many ways in a laboratory setting. Many of the same issues are encountered by welding to metals together. Heat and preasure make physical changes to the metal.

Take Care

Nat Lamberth
 
I love it..a good discussion.

My tuppence.

Not all parting cuts are equal.

When you get a tool set up right, it makes nice curls, and the metal barely warms up. I like lotsa oil for parting

A poorly ground tool, with bad speed/feed gets hotter than hell, squeels like a pig, chatters and cannot be good for anything. This is just poor machine work.

Grind your tools well, or use a quality insert parting tool, like an Iscar, with the right feeds, speeds etc.

is all I have to say.

I love a Milwaukee portaband also, for many jobs, in and outta the lathe.

Ben
 
Rustystud said:
Jackie and others:

If you look at the metal structure under a microscope, have it ultrasound tested, magnafluxed, or Xrayed you would see what is being said in those test.

Parting is well known to cause a tight spots, small fractures, hard spots on both sides of the part.

A simple example is to look at copper or aluminum tubing that was cut with a tubing cutter. No matter how sharp your tooling is and how light our feed is it still pinches and distorts the metal in front and directly beside the parting tool.

I am glad you are happy using your parting tool. I am happy using a bandsaw and facing the muzzle with a tool bit. I am sure you are saying, what is the difference in parting and facing the barrel after it has been sawed. The stress on the barrel/muzzle is going against the bore when parting. The stress is going parallel to the bore with facing. The saw blade induces less stress around the cut surface than the parting tool.

This topic was discussed in great detail in our machining class. Our class went to an engineering firm that test metal and looked at metal cut many ways in a laboratory setting. Many of the same issues are encountered by welding to metals together. Heat and preasure make physical changes to the metal.

Take Care

Nat Lamberth
Click to expand...

I think you were out too late last night. I have got to raise the BS flag this time. It is like the guy who did not want me to drill and tap for a front sight base on his match barrel because it would force a dimple into the bore.
 
Rustystud said:
Parting is well known to cause a tight spots, small fractures, hard spots on both sides of the part.

A simple example is to look at copper or aluminum tubing that was cut with a tubing cutter. No matter how sharp your tooling is and how light our feed is it still pinches and distorts the metal in front and directly beside the parting tool.
Click to expand...

The copper or aluminum tubing has a hard wheel forced into the softer material. The softer material stretches beyond it's elastic ability and is permanently distorted as it separates.

This is a far cry from a tempered steel barrel being machined by a hard sharp parting tool. You can't really compare the two. The steel barrel is not forced beyond it's elastic ability.

... and even if it was, the crowning of the barrel would remove any imperfections caused. Proof of this is in the accuracy of the many, many barrels Jackie and others have done this way.
 
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As to the BS..

First, Jim I am up late every night as I have two jobs.

Second, as for the badge of the BS Flag I will wear it with honor as I know where it came from.

I believe you wiil find this topic discussed in many machining text books and it may even be discussed in the MACHINIST HANDBOOK.

You might even find it discussed by some of the better barrel makers.

Nat Lambeth
 
I use a saw and then face the end in a lathe, cutting from the bore outward. This was how I was taught by three old toolmakers. I will run a test one day at work using an air gage and cutting with a saw and also with a parting tool. Will post the results when I get them.

Kevin
 
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