FP4NC: Larger Diameter Work
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  1. #1
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    Default FP4NC: Larger Diameter Work

    Running a little job here that required some work around to handle the size of the needed parts.

    Fitting new liners to a car set of brake drums on a 52' 340 mm Ferrari.
    Originals had been worn and turned too many times where the liners had become thin and unreliable.

    Original drums setup on the lathe (21" "Dong Yang" , stupid name, gorgeous license copy of an Okuma) And original steel liners cut out.
    Drums cleaned up straight and round to the same size for the front and same for the smaller rear.

    Material selected was Ductil iron,(80-55-06) supplied by "Dura-Bar. Sized at 14", and 15" OD's. being roughly 4 1/2" long.
    Needed the material to have a center hole, but only supplied or available as a solid. Dura-Bar was able to supply the material by trepanning the center hole...Saving tons of time and
    material cost.



    Set the rings up on he lathe for turning. Lathe is 21" swing, but the starting material is too large to pass over the cross slide. To allow machining i used a boring bar (shop built)
    to give the reach needed (over 5" long) .Design of the bar allowed turning both ID and OD by swapping the tool holder from RH (OD) to LH (ID)...



    Material was purchased aprox 1 3/4" longer than required to allow for chucking. I wanted to be able to machine both the ID and OD in one setup.
    Which brings us to the Deckel portion of this story.

    Once the ID and OD were at size i needed to cut off the excess stock. tool long to allow use of the parting tool in a conventional setup on the lathe...
    Could have ground up a parting style tool that fit the boring bar already in use, but i suspected that the depth of cut (1.3" on a side) would be difficult to handle and not really rigid.

    Opted to do this operation on the FP4NC.
    Took the 10" "Schunk" chuck off the Romi and fitted some extended soft jaws that would allow chucking the larger (front) liners on the ID....
    Removed the cam lock pins from the chuck (D1-6) and set the chuck on the mill table. Without the pins you have in effect a flat face on the chuck back. Set the chuck in the center of the machine table
    and using the rotary function set the chuck to run true with the table's rotation.....Used hold down clamps to secure the chuck body to the table....
    Gripped the liner and mounted a .250" 5" diac saw to a stub arbor and i was ready to proceed.



    Plunged the cutter till it pierced the inner wall of the liner, then used the rotary feature of the 2038 table to cut the unwanted stock from the liner.....
    Working this way, found the best was to climb cut. Reduced the chatter and allowed relatively rapid rotation.....
    Definitely not the most efficient way to get this done, but worked without issue so that i could continue with the job....
    This was a case where a nice VTL (Bullard) would have been the ticket.

    Another view of the job...Chuck has been changed to different jaws in order to run the smaller rear liners. Here i added some clamps to ade in holding the part...Gripping on the thin liners from the ID they tend to turn into a three lobed part and its hard to develop enough grip. Here i am clamping between the jaw of the chuck and the OD of the liner ....a more direct grip.

    Clamps holding the chuck also clearly seen...Cutter is opposite side of the part , about to finish the cut....



    Lots more to this job, but most involved different tools/setups that aren't relevant here....

    Cheers Ross

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    Always a learning experience and a pleasure to see what you are up to. Cool setup- always wondered how well rotary milling with the Uni table like that would work, have had a few jobs where being able to run through the center of the table is handy. Have done some smaller project like this, but I cheated and used the NCT500

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    Quote Originally Posted by AlfaGTA View Post

    Lots more to this job, but most involved different tools/setups that aren't relevant here....

    Cheers Ross
    Would still like to see them -

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    I have done similar but on a smaller scale on my FP2NC. The job was to open up the hollow cavity inside tall red brass fire hydrant operating nuts that had seized on the screws. Since I only have a fixed table, I contoured the circle with G41...G2.... in several passes. The cutter arbor looked very similar to Ross'. The cutter was an insert saw that used GT_-style single-ended parting inserts. I think they were 1/16" wide. It was a pucker job with a lot of overhang using a fairly delicate cutter in a "grabby" material, but it worked well.

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  9. #5
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    In deference to john (Mud) here is some additional text and photos of the brake drum /liner job.

    Some base line information: Liners were originally made from steel. Opted to replace them with Ductil iron alloy 80-55-06. Higher strength than grey iron.
    Original liners were made with a flanged edge on the liner that nested to the outside face of the drum and were riveted using copper rivets through the drum casting...




    The replacement liners will retain this feature and replicate the rivet application.
    Liners will be shrunk fit into the aluminum drums. I will be using .035" of interference on the fronts, somewhat less on the rears.
    Because the liner flange needs to be square and fully seated into the drum , i needed some method to guide and insert thee liners into the heated drum casting....

    As outlined above the original drums were trued up on the ID to include the flange seating area.
    I used the boring bar as already shown . Drums were held by gripping on the OD of the "Rudge" spline of the front and rear hubs. Held using soft jaws bored to size.
    To control chatter i used a "rope" of modeling clay (Plasticine) wrapped around the outside of the drum......(sorry no photos of this setup)
    Liners also turned from rough stock to size in one chucking...Liners gripped on the ID using 4-jaw . (see above)
    Liners finished on the OD , left undersize on the ID leaving the flange somewhat thicker than needed...OD of the liners also included a rib on the OD that would form a feature as part of the backing plate dust seal...
    That rib was left somewhat oversize and unfinished.

    So here is the setup i developed to install the liners:
    There is a nice 50 ton "Dake" H-frame hydraulic press at the shop. Deemed unsuitable for the liner installation because of the relative slow movement that was possible with this press (hand operation), and a relative
    short stroke on the ram.
    As things would have it, shop also owns a small press for doing straightening work...has a 1 1/2" ram running with an air over hydraulic ...incorporating a foot pedal control. That cylinder also has
    a full 9" of travel.....
    Small press frame was disassembled and the ram with its support frame clamped to the Dake press top frame....Original Dake press head moved to the far side for clearance...



    Made 4 major parts for the liner install.

    Upper press plate. Holds the liner and provides the push against the liner.
    Upper plate hub. Connects and holds (clamps) the press ram to the upper press plate.
    Top view:


    View of bottom face of press plate. Note bolts holding the hub to the plate.
    Outer edge of plate faced both sides to be flat with the axis of the hub.

    Center Hole in the hub , both sides ,,,parallel and concentric. Upper bore has clamp to grip the hydraulic ram...
    Lower bore made at size (1.000") as a seat for an alignment bar (explained later)

    Also note the threaded hole patterns toward the outside of the plate...2 circular patterns to accommodate the two different sized liners (front, and rear)
    Upper plate made from mild steel plate 3/4" thick. roughly 16" OD Purchased plasma cut on OD. Drilled and bored in center to locate the center hub.....Drilled and counter bored for retaining bolts.




    More to follow.....
    Cheers Ross

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    More press parts:

    Second major part needed for installing the liners was the lower plate or platen.
    Again this is 3/4" steel plate. Center hole with a steel bushing fitted that is sized to be a loose sliding fit to the OD of the front and rear hubs....

    Plate is also drilled and tapped (1/2-20) in two patterns (6 and 4 holes) to relate to the different drum sizes and configurations....(front and rear)
    The holes ate there to accept threaded swivel foot adjusters...photo shows the adjusters in the 4 position row for the rear drums.
    Additional 6 holes visible, used for the front drums....
    Center alignment bushing shown as well.



    In addition there were two alignment bushings made. Have a true 1.000" through hole, and accurately locate on the hub bearing bores (front) or splines (rear).....



    Bronze was selected here for ease of machining (long bore at 4" )

    The liners needed to be held to the upper plate and since it would be upside down the holding method needed to be strong enough to keep the liner in place...Also needed to be
    relatively low profille as when pressed together there would be less than .2' of liner proud of the drum casting....

    Further i needed to locate the liner concentric to the center hub....

    I choose "Mitee-Bite" clamps....
    Here is a clamp , 1 of 8 placed around the liner...These clamps have a threaded screw that is eccentric. Rotating the screw cams the clamp into the part....



    Here the liner is in position, all 8 clamps fitted. A true bar is installed in the center hole of the hub and used as a spindle to sweep the OD of the liner.
    The clamps can be manipulated like a 4-jaw chuck to center the liner....



    Once the liner is aligned the upper plate and center hub are moved to the press and clamped to the press ram....



    More to follow...................
    Cheers Ross

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    The next step is to fit the lower plate to the press.
    Drum is set on the lower plate with the swivel foot adjusters bearing on the drum at the outside edge .
    Object is to provide support to the drum where its strongest. Adjusters need to swivel to account for the as cast surface of the drum casting....

    Adjusters are positioned to fit between the cast air ducts in the drum face....Drum is centered by the bushing in the plate locating on the hub of the durm.



    The platen of the press is raised while an alignment bar is fitted to the center bore in the hub and held via grub screw....the bar enters the bushing in the center of hub. This aligns the upper plate and liner with the drum...
    The swivel foot adjusters are set to take even contact, this levels the drum with the upper plate, and also sets the liner concentric with the drum....



    The lower plate is clamped to the press platen at this point.....

    The press platen and drum are now lowered to the base of the press. A heat reflecting blanket is wrapped around the upper plate and liner.....
    The drum is heated in place using a torch with large rose bud ...Temp is monitored using a temp gun.

    Once the drum is hot (350+f) the platen is raised back up close to the liner...alignment bar in place, the platen secured with pine (normal press setup)

    The hydraulic ram is engaged and the liner pushed into the drum till it bottoms....the pressure is held till the drum cools.....

    The end result.....


    Work remaining....Drill the rivet holes suing the original holes in the casting, tehn apply the copper rivets...
    Finally, chuck up drum,s and finish turn the ID of all , finish the detail of the outside ridge on liner ....
    Finally fit to the car.
    Cheers Ross

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    How did you determine the amount of interference? Rule of Thumb or were you able to measure the old parts?

    Do you plan on redrilling the holes at the intersection of the shoulder and the drum ID? I assume those were supposed to help ventilation?

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    Interference calculated by projected operating temp and differential expansion of the drum....

    Angle drilling done as are the rivet holes...Done on Deckel with head angled to replicate original on drum...Stop on table that i set against the inner diameter of the liner and just
    moved the drum by hand for each angled hole while resting against the stop.....
    They are there in my understanding to give a way for oil, grease water or gas to exit the drum.
    Would post photo of drilled liner, but the software on the site seems to not be letting me do so...perhaps i have exceeded my posting limit.

    Cheers Ross

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    I done much the same thing for an International pickup, I used steel and a shrunk the drums on the liner I made. I bought material just a little longer than needed and used a lathe to finish ID and OD for one drum then turned the piece around and did the other end, then parted it off and had two piece with no waste. The pickup is still run on a farm with no problems to date.

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    Did you notice the liner beeing out of round because of the 4-jaw chuck ?


    Peter

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    Peter:

    Material pretty thick where the chuck gripped the liner...However i did release the chuck grip before the final cuts on ID/OD.
    Then re-gripped the stock with a light pressure....
    Some distortion when measured after cutting off the excess, but well within tolerable limits...Not enough to affect the install into the drum.

    Liners will be finished on ID now that they are installed into drums.

    Cheers Ross

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