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Thread: Tractor frame to be milled on bridgeport

  1. #1
    Join Date
    Aug 2017
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    1

    Default Tractor frame to be milled on bridgeport

    Hi all:
    Heres one for consideration, ideas sure are welcome.

    In a few weeks or so I will be starting on a machining project that is sure to test the rated capacity of my Bridgeport mill. This is not a matter of do or don't it must be done plain and simple. I have on our farm a Oliver 1650 tractor that was repowered with a cummins B series diesel. when the shop originally did the repower they cut the cast iron frame with a plasma torch to make way for the oil pan and had to remove the engine mounts to make way for the bell housing. The problem being is that the heat that was generated from the Plasma torch ultimately set up a stress fracture in the frame and it was cracking and would soon break completly through if we had left it go. Don't get me wrong it's been twenty four years since we repowered, but still...........the crack has been there for a long time and gradually getting worse.

    What I am dealing with is white cast that is 1.250" thick at it's thinnist point, the frame will weigh in excess of 500 lbs, is approx. 7.5 feet long, 14" deep, and 20" wide.

    What I am thinking of doing is lay a couple of pieces of heavy channel iron across the table and secure channel to table and set the frame on top of that and secure into channel.
    I can secure the frame to the table but will depend on using the ram to move from one side of the frame to the other to cut out both sides of the oil pan hole with only slight movement on the y axis. I don't need to be real precise, +,- .050 on all sides but I do need to hog out about .750" on both sides.
    I'm planning on running low rpms with a roughing end mill, and having to reset every 20" of x travel. Because I know heat is what set up the crack originally, I'm thinking of retrofitting a windshield wiper pump and makeshift resivore for flooding with coolant. With the oil pan hole hopefully successfully machined I will have to flip the frame over to machine the engine mounts out.

    Outside of the obvious, heavy, big item and awkward to handle what are some of the pitfalls I should look out for?

    I've been machining for 25 years, but never tackeled anything this big and cast at that, so I'm open for suggestions.

    thanks in advance, pls Google Oliver 1650 tractor to get an idea of what I am about to undertake.

  2. #2
    Join Date
    May 2011
    Location
    Surrey, England
    Posts
    464

    Default

    One of these?

    http://www.ebay.com/itm/OLIVER-77-GA...-/263157905717

    I presume shipping would be the killer...

    Where do you want to machine it, and where's the crack?

    Dave H. (the other one)

  3. #3
    Join Date
    Oct 2002
    Location
    Bremerton Washington
    Posts
    5,756

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    Overhung weight on a turret mill table is a killer of ways. I suggest you work up a vertical suspension so the work hangs from springs, counterweights, or bungee cord about in place on the table when hanging free. There must be enough vertical compliance so the work can be elevated and enough horizontal compliance so the table and saddle can be worked. Don't forget the turret can be swiveled and the ram extended to access a far greater work envelope than by table and saddle motion alone.

    This is a job far better performed on an HBM. Can you get access to one?
    Last edited by Forrest Addy; 09-12-2017 at 07:32 PM.

  4. #4
    Join Date
    Apr 2014
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    639

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    Would a router be able to handle a job like this?

  5. #5
    Join Date
    Jan 2007
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    Northern California
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    What Forrest Addy said. That's entirely too much weight and overhang for a Bridgeport.

  6. #6
    Join Date
    Apr 2017
    Location
    Kelowna BC
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    I used a saw roller stand on ablock to hold overhang weight, and allow sliding. Boring end bushing holes on a belt vulcanizing press.
    8 feet or more long, 9 inches or more wide and about 20 or plus inches high.

  7. #7
    Join Date
    Dec 2002
    Location
    Friesland, Netherlands
    Posts
    2,160

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    Sounds like an interesting project!

    HSM'ers have been shoehorning workpieces far beyond a machine's capacity into their equipment for decades, that's nothing new. A couple of things to consider:

    Is the Bridgeport bolted down to the floor? Having the whole lot topple over would ruin your day.

    You mention "white cast iron". Just how hard is this stuff? I know from experience that in some cases, HSS cutters won't touch it - you might need carbide and more feed force than you'd expect. Try a file, see how it cuts.

    And yes, as others say, try to keep weight off the table with other means of support - an engine crane with a tension spring supporting the heavy end of the frame would be a nice solution.

    Good luck, post photos!

    Ian
    All of the gear, no idea...

  8. #8
    Join Date
    Oct 2002
    Location
    Saskatoon, Saskatchewan
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    I'm curious as to why you want to mill off 3/4" on each side?

  9. #9
    Join Date
    Apr 2017
    Location
    Kelowna BC
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    I forgot to mention, keep checking the machine if not bolted down. Grab the ram and give it wiggle.
    I have had to add weight to the far side of the table as it was getting tippy.. scary when it starts to lift the base on one side..

  10. #10
    Join Date
    Oct 2002
    Location
    Bremerton Washington
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    5,756

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    Quote Originally Posted by 754 View Post
    I forgot to mention, keep checking the machine if not bolted down. Grab the ram and give it wiggle.
    I have had to add weight to the far side of the table as it was getting tippy.. scary when it starts to lift the base on one side..
    Bridgeports are rated for 300 to 500 lb centered over the knee; a rule seldom followed. Outsize workpieces like lomng heavy tractor frames double the weight whose center of gravity lies outside the machine's working envelope is a recipe for heavy way bearing galling or even toppling the machine if, as was said, it's not bolted down. Counter balance weight would add to the gross and if not calculated carefully will still leave large weight and moments un-addressed.

    Some form of weight relief must be devised before attempting this tractor frame project on a pitifully frail machine tool like a turret mill. I've seen similar happen with a 6-71 diesel cylinder head and the overhung weight was sufficient to immobilize the table leadscrew and render the saddle axis nearly impossible to crank.

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