Straightening Propeller Shaft Material

[jackieschmidt]

One of the first steps in machining the long propeller shafts that we build is getting the bar stock straight enough To machine. This will be an 9 inch diameter x 35 foot long shaft When finished. The rough bar starts out at around 9.5 inches.

Although the material does come rough turned, it is no where near straight. So it is common procedure to straighten it.

We also use these rigs in repair. Many of the shafts that we rebuild are bent, or have to be straightened after welding up worn areas, so we must have an efficient, and precision method of straightening them. The pump assembly is a 10,000 psi Simplex unit.

This is our 500 ton rig. We have a 150 ton rig, a 300 ton, a 500 ton, and a 700 ton.

All of my Machinist are trained to handle these rigs. We designed and built them. The arms are adjustable so you can place the tonnage exactly where you need it. We use T-1 plate to build the rigs from.

Precision straightening is as much of an art as anything. Ascertaining exactly where bends begin and working them out with the proper tonnage comes with experience.

 

[Tommie]

Fascinating. What are the allowable tolerances?

 

[PigButtons]

When you need a dumpster for the chips, you know it's the big time.

As always, thanks for posting, Jackie.

 

[jackieschmidt]

H

Fascinating. What are the allowable tolerances?

When straightening new material, you just have to get it straight enough to clean up on all surfaces.

Often we will get a shaft in that was bent in service, with nothing else wrong. Depending on the severity of the bend, we can straighten shafts to run just about dead true. We have gages on the pumps that allow us to put “precision tonnage” at a very specific spot.

A good example is we had a 7 3/4 diameter shaft come in last week from one of our customers that was bent at the prop taper about .250 inch. The taper, which the prop fits on, is around 20 inches long. I was able to get it within .005 anywhere on the taper and be put back in service with no other work needed.

here is a picture of one of my machinist straightening the coupling end of a rebuild after rewelding the worn surface. This is our 300 ton rig.

 

[Charles]

Did boat shaft straightening for years at Armco Stainless never saw a set up like that

 

[jackieschmidt]

H

When straightening new material, you just have to get it straight enough to clean up on all surfaces.

Often we will get a shaft in that was bent in service, with nothing else wrong. Depending on the severity of the bend, we can straighten shafts to run just about dead true. We have gages on the pumps that allow us to put “precision tonnage” at a very specific spot.

A good example is we had a 7 3/4 diameter shaft come in last week from one of our customers that was bent at the prop taper about .250 inch. The taper, which the prop fits on, is around 20 inches long. I was able to get it within .005 anywhere on the taper and be put back in service with no other work needed.

Did boat shaft straightening for years at Armco Stainless never saw a set up like that

We actually get shafts in to straighten only from other shops that have no straightening capabilities, or at least the capabilities we have.

The beauty of using these types of rigs is you can precision straighten the piece in the lathe and put no strain on the lathe what so ever.

 

[Fuj]

When you need a dumpster for the chips, you know it's the big time.

As always, thanks for posting, Jackie.

Erie Forge and Steel near where I live, made the shafting for the
Ohio class submarines, My brother has a chip of steel mounted
in a piece of walnut commemorating the first delivery. It weighs
near 3 ounces.

Jackie.....You'd fit right in with a few of the guy's I shoot with that
work for Don Jon ship building. Just a short time ago, they did full
repair on the WW2 Sub USS Cod. Not many Lake Freighters have
come in for winter work or dry docking as of yet. With the Lakes
still open, they will haul to the last minute. Thousand footers have
been built and repaired here.

 

[dfrosch]

Gotta stress relieve after straightening?

 

[jackieschmidt]

Gotta stress relieve after straightening?

No.
It really doesn’t seem to be an issue.

 

[gdbleb]

Now that's a lathe!

 

[7887mm08]

I have straightened a lot of shafts in my career as a machinist, But nothing of that size!
Kudo's to your abilities. Love it!

 

[Hal]

Jackie
Thanks for post pictures and sharing what goes on in in a Big shop.

Hal

 

[Walt Schmidlin]

Truly amazing equipment and expertise. Guess everything is bigger in TX

 

[Spike A]

Not sure the size of boat in need of a shaft like that… but I assure you it’s no 20ft pontoon…

 

[hogpatrol]

Is that an old gun lathe from WW2?. Ran one similar in a steel mill shop. No rapid traverse, to get to the center end, dropped the half nut and ran it as fast as it would go.

 

[Dusty Stevens]

Thanks for sharing that jackie. Keep on giving them the shaft

 

[Kracken McGraw]

Ok I’ll ask the stupid question. What device do you use to tell if it’s perfectly straight?

 

[mike mccormick]

Where there's a will, there's a way! I like the design of your straightening presses. Well done!

 

[jackieschmidt]

Ok I’ll ask the stupid question. What device do you use to tell if it’s perfectly straight?

Dial indicator.

keep in mind, on any piece you can always make two spots run true. In this case, we decide where the bend originates, and the steady rest goes there. The other point is trued in the chuck. You work the bend out in around four foot sections, moving the steady rest to the last spot that runs true. Sometimes you have to work both ends from a section in the center.

on a finished machined shaft, where you have to straighten a bent part of the shaft to run dead true with the rest, you have to ascertain exactly where the bend originates and work it out from there. Often you have to get it close, yhenstart at that point again.

like I said. There is a certain amount of art involved in this process That comes with years of experience.

The two lathes in the pictures are our 38 foot American, built in the ‘06’s, and the other is our 32 foot Lehman, also built in the 60’s. Both are duel carriage.

the shafts in the pictures come out of 3200 horsepower inland tugs. Here is a picture of a typical size push boat that we work on. This vessel was christened last summer.

 

[jackieschmidt]

On occasion, we will have to straighten a bent rudder post, The shipyard will remove The blade and send it over. Her is a 8 inch rudder stock I was preparing to straighten last week.