I've brought this up before

Pete Wass

Pete Wass

Well-known member
Wondering about heat straightening barrels. There is another recent YouTube in which Keith Fenner straightness a long section of SS he will make a propeller shaft from. His personal standard is a max of .002" anywhere along the entire length of the stock . He demonstrates how he makes that happen.

Thinking back to the thread on the Air Gun forum in which a lad quoted laboratory results in accuracy differences between straight barrels and bent barrels and the indexing of them, it seems absolutely feasible to me that this is an area in our sports that could be dealt with by using the same or similar techinique(s) the old shipyard machinist uses.

I havent yet gotten to the barrel I have with the .015" bow in it but will try this week.

P
 
Shafts need to be straight because they are rotating parts that need to be in balance and for which there may be alignment issues as well. They are not used the same way that gun barrels are, so internal stress is very likely less of an issue than it is for barrels, where it is a known issue when the very highest level of accuracy is required. On the other hand, heat and mechanically induced internal stress are well known enemies of rifle barrel accuracy. Apples and oranges. Fellows that I know that index barrels are not reporting any problems. Another fellow that I know has done some testing and with the high quality barrels that he uses he has not been able to see an on target advantage from indexing. I am not saying that there is none, but that for typical short range CF barrels, he has not been able to see it on the target, and yes, he knows how to shoot and tune.

Many years ago, when I was a LOT younger, I worked in the office of a small structural steel fab shop producing shop drawings and doing estimating. (I also had a hood, gloves and chipping hammer in the tool shed, for personal projects.)One of the partners was a very talented fabricator who was an absolute genius with regard to straightening with heat. He would use a rosebud (oxyacetylene torch heating tip), a 2# coffee can half full with water, and a red shop rag to make the most distorted welded fabrications look perfectly straight. Anyone in the industry is familiar with the technique. For shaft work, this is commonly done with a hydraulic press, except in cases where it would not be practical.

One issue that you should be aware of is that for certain high performing alloys, fabrication induced stress can seriously degrade their strength, to the point that stress relief is an absolute requirement. This came up in a conversation with a friend who is a materials engineer, who spent his career in the defense industry. We were discussing another way of stress relieving that has seen some small use for rifle barrels...sub harmonic vibratory stress relief.
 
in short range Benchrest, barrel straightness seems to be a non issue. Because always remember, the ID's of barrels are not "bent" on the classic definition. They simply have sections along their linear length that do not run truly straight with other sections. This is a product of the initial Gun Drilling procedure.

I did a thread some years ago where I showed how different portions of the bore could run out on complete different linear plains. I took and old Unlimited Barrel, turned the OD dead straight between centers, and scribed a straight line down it's length. I then count it in 4 inch long pieces. I placed these pieces between centers And took indicator readings at each end.

On some pieces, I would see as much as .004 runout in an entirely different spot in relation to the scribed line as other spots on other pieces. Some almost 180 degrees opposite.

That thread is in the archives somewhere, I have no idea how to retrieve it. But anybody with even a small amount of machinery sense can see the true nature of how runnout is exhibited in a typical Gun Drilled Hole.
 
Jackie,
It would be interesting to do the same sort of testing on a Bartlein barrel that had been honed with one of their new Sunnen machines.
Boyd
 
If it is a full length hone, similiar to those used to align hone main bearing saddles in engines, yes, I suppose it could st sighter a bore, depending how much the gun drill wandered in the initial drilling operation.
 
jackie schmidt said:
If it is a full length hone, similiar to those used to align hone main bearing saddles in engines, yes, I suppose it could st sighter a bore, depending how much the gun drill wandered in the initial drilling operation.
Click to expand...

A hone is not for straightening a hole. It removes very little material. You can go to Sunnen's website and they state the same thing.
 
I am thinking

The difference found in that laboratory between truly straight barrels Vs not so straight ones may be the difference between "hummers" and non hummers, or could be anyway. It is also somewhat intrigueing that some gun makers straighten their barrels and hand presses exist to do same and have for a long time. So, apparently it is possible to straighten barrels. Why Benchrest people don't seem to see any value in doing so is a bit puzzling to me.

Pete
 
Understood

Boyd Allen said:
Shafts need to be straight because they are rotating parts that need to be in balance and for which there may be alignment issues as well. They are not used the same way that gun barrels are, so internal stress is very likely less of an issue than it is for barrels, where it is a known issue when the very highest level of accuracy is required. On the other hand, heat and mechanically induced internal stress are well known enemies of rifle barrel accuracy. Apples and oranges. Fellows that I know that index barrels are not reporting any problems. Another fellow that I know has done some testing and with the high quality barrels that he uses he has not been able to see an on target advantage from indexing. I am not saying that there is none, but that for typical short range CF barrels, he has not been able to see it on the target, and yes, he knows how to shoot and tune.

Many years ago, when I was a LOT younger, I worked in the office of a small structural steel fab shop producing shop drawings and doing estimating. (I also had a hood, gloves and chipping hammer in the tool shed, for personal projects.)One of the partners was a very talented fabricator who was an absolute genius with regard to straightening with heat. He would use a rosebud (oxyacetylene torch heating tip), a 2# coffee can half full with water, and a red shop rag to make the most distorted welded fabrications look perfectly straight. Anyone in the industry is familiar with the technique. For shaft work, this is commonly done with a hydraulic press, except in cases where it would not be practical.

One issue that you should be aware of is that for certain high performing alloys, fabrication induced stress can seriously degrade their strength, to the point that stress relief is an absolute requirement. This came up in a conversation with a friend who is a materials engineer, who spent his career in the defense industry. We were discussing another way of stress relieving that has seen some small use for rifle barrels...sub harmonic vibratory stress relief.
Click to expand...


Being able to separate the crooked hole from the o d is an issue, for sure. Apparently there is a visual technique used by folks who straighten gun barrels. Friend who was trained in the Army's Armorer school described the technique to me. I have the impression that the process is meant for younger eyes, mebby not. Considering the Springfield Armory saw a great deal of value in straightening barrels it is a shame the process seems to have been lost along the way.

Pete
 
Keith is a shmatd guy

FBecigneul said:
I went to Keith Fenner YouTube.
Keith is a busy fellow what with his repair establishment and with his video camera.
Very interesting stuff but not on Thanksgiving as I should be videoing the oven.
Click to expand...

After working at stuff I really didn't like much and not being very good at, I envy him. Wish I had had the foresight to find a trade like his to work in, I would have enjoyed my life a lot more I think. I began that way but was too impatient. Still am.

Pete
 
Pete Wass said:
After working at stuff I really didn't like much and not being very good at, I envy him. Wish I had had the foresight to find a trade like his to work in, I would have enjoyed my life a lot more I think. I began that way but was too impatient. Still am.

Pete
Click to expand...


Pete, I don't think that it is cost effective and it does induce stress.
 
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