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jackie schmidt
01-27-2008, 06:22 PM
I am stuck down here in Corpus Christi doing the biggest job I have ever attempted. I am align boring the main abundements and boom pin holes on a BIG 30 inch dredge boat. The holes I am boring are between 31 inches and 33 inches in diameter. The pin that goes into these holes weighs about 4000 pounds.
This would be a major task in the friendly confines of the shop, much less out on a drydock, using portable boring equipment. I came down and looked at this job about a month ago, and told them, "yeh, I can do it". They were so tickled at my responce they never bothered to ask what it would cost. The answer to that question is, "what ever it takes".
It took me the better part of two weeks to tool the job up. Basically what I am doing is boring the wallowed out holes round, and back dead in line with each other. I work off of a music wire in order to establish the true points for which to set the boring bar.
I tooled the bar, (my 4" diameter 14 foot bar), to turn approx 8 rpm at full throttle on the air motor. I can pull about 3/16 to the side with the torque available, which is considerable. I us a 5hp air motor which puts out about 350 ft pounds of torque. Multiply that by my 36 to 1 gear drive reduction, and you come up with about 12,000 ft pounds of torque at 110 psi. It takes about 900 ft pounds to pull the tool on that 31 inch diameter sweep when cutting 3/16, (3/8 inch on diameter) to the side.
I am gong to take a bunch of pictures of this set-up, just so the Forum can see that thereis all sorts of "machine work" being performed that is to say the least, is rather specialized. Being in the Marine Industry, We do quite a bit of this sort of thing. I sort of like the idea of taking something that is a piece of junk, and performing what ever task it takes to make it a fully functional piece of equipment.
Needless to say, this is about as far from the "CAD-CAM-CNN" world as you can get and still be on the same planets. And it's a far cry from doing chamber jobs.
I plan on being in Houston Sunday morning, as I am the Match Director for our up comming Tomball Gun Club Score Match next Sunday Morning. I doubt I will shoot, I want to devote my time to the match so everything runs a smooth as possible, but if anybody wants to shoot my 30PPC, I will have it available.........jackie

Gene Beggs
01-27-2008, 07:02 PM
Most interesting Jackie. I'll be looking forward to seeing pictures of that job.

Thanks for sharing with us.

Gene Beggs

bryan
01-27-2008, 07:27 PM
What are the acceptable tolerances?:D
Bryan

Dave Short
01-27-2008, 07:30 PM
Jackie,
I used to work for a company that (among other things) did very much the same sort of repairs on heavy equipment buckets, booms, arms, etc. We'd weld temporary bearing mounting points onto the machine, attach a boring machine to those mounts, pick-up the correct position (by various means including shimming), align bore the bosses, and finally cut the mounts back off of the machine. In cases where the bosses/mounting points were too worn to bush, we'd make new ones with undersize bores, weld them on, and bore to size as usual. The boring equipment was light enough to lift with a small jib crane or forklift. As I remember, the largest diameters we dealt with were in the 8" range.

Have fun, but be careful...
-Dave-:)

Pete Wass
01-27-2008, 08:59 PM
back in my youth. I always found it most interesting to solve the how to do it. It was often boring; no pun intended, to actually do the work. I left that for the world of Sales but have missed it off and on. P,

JerrySharrett
01-27-2008, 09:28 PM
I am stuck down here in Corpus Christi doing the biggest job I have ever attempted. I am align boring the main abundements and boom pin holes on a BIG 30 inch dredge boat. The holes I am boring are between 31 inches and 33 inches in diameter. The pin that goes into these holes weighs about 4000 pounds.
..jackie

Are you going to use flood or mist coolant?

jackie schmidt
01-27-2008, 09:29 PM
On a job like this, the aim is to get round, true, machined holes that are all in alignment with each other. (in the end, the thing DOES have to go together). The pins will be built up with weld and cut to fit the holes that I bore. The boom, (that is the thing that holds the huge cutter head and suction pump on the dredge), will have large bronze bushings custom fit and installed into the holes that I bore in that assy. The pins will have about 1/32 inch clearance in their abundements, and the bronze bushings will probably have about .060 clearance over the pin.
My bar, with the minimum bearing spread of 28 inches that I can use on this job, will bore within .001 of roundness, and cut just about dead staright. It is what we call a "traveling head" bar. The bar, (which is hard chromium plated), turns in cast iron bearings, and is just about imprevulous to the harsh inviroment of the Shipyard. It has a 1.750 keyway with a 1.250 6tpi screw for the entire length. A "half nut" fits into the keyway, engages the thread, and advances the cutter head. One of the bearings has a built in thrust collar that takes the tool load.
The feed rate is .016 per revolution. That seems course at first thought, but on large work such as this, it is just right.
With work like this, you normally do not have to "size" a hole. But, if the requirements of the job dictate that I bore to an exact size, I can generally hit it within +- .002.
As a note on this big Dredge, the main pump is powered by a 4000 hp 710 EMD Diesel. The "cutter head", (that is the thing that chops up the bottom so the pump can suck it out), is powered by two 1500 hp eletric motors feeding into a common gear box. ..........jackie

jackie schmidt
01-27-2008, 09:47 PM
Lots of black suphurized cutting oil is the ticket. I grind the tool bits from 1 inch square Rex-95. As an old machinist yourself, I would amagine you have seen your share of Rex-95...........jackie

JerrySharrett
01-27-2008, 09:52 PM
Lots of black suphurized cutting oil is the ticket. I grind the tool bits from 1 inch square Rex-95. As an old machinist yourself, I would amagine you have seen your share of Rex-95...........jackie
I go way back to Rex-49 and Rex-AA even!!

That is what we turned the prop shaft on Noah's Arc with.

Be careful, bud.

Kirk Ethridge
01-28-2008, 12:55 AM
I was watching discovery or similar once and saw them cutting grooves in a Prop drive shaft for a large ship, this chips fell off bigger than a mans thumb., they looked red hot like the old "rivets" used to put together large steel i-beams.

Obviously, your boring bar is bigger than mine!

Kirk

Joe Entrekin
01-28-2008, 12:26 PM
Jackie, is this one of the Jim Beam (?) dredges, by chance? I used to work for Georgia Iron Works, and they made the pumps for these monsters. Some of them took 7,000 connected HP. One of the early ones got sunk in the Galveston area (I think) because of a water hammer that blew the pump (s) up & dumped a lot of slurry on the barge in a big hurry. After that, they built an encasement around the pumps to dump overflow overboard. Interesting work, but mighty big to us ordinary folks.

fx77
01-28-2008, 02:26 PM
This is fascinating and it is what Made in the USA is and should be about.

Butch Lambert
01-28-2008, 05:42 PM
Jackie,
I sent a link of this thread to the Practical Machinest forum. I think that they find your job interesting. Please post photos and I will keep them up to date.
Butch

Dusty Stevens
01-28-2008, 06:12 PM
that is cool jackie. be careful down there:D