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  1. #1
    BobL is online now Member: Blue and white apron brigade
    Join Date
    Feb 2006

    Default Little turning job

    My motor bike restoring/modifying brother asked me to do a small turning job for him involving shortening an ally cylindrical shaped crankcase breather chamber that was 10 mm too long to fit in the space available. The chamber was ~125 mm long x ~60 mm in diameter. and had threaded end caps glued onto each end. There were two 3/8 BSP threaded holes in the side of each end cap but we had no idea how thick the chamber was.

    We could have persisted and removed one of the end caps (we did give it a bit of a try without any success) and cut 10 mm off the main chamber body and cut a new thread but I did not trust myself to setup and cut such a fine thread of that size.

    Plan B was to cut 10 mm out of the middle and get pro welder and boat building BIL to TIG weld the two halves back together, the chamber is hidden under the seat so looks are not an issue. BIL agreed to do the welding for a 6 pack (which he always generously shares all round) and asked me to turn complimentary steps into the cut ends so that would make them easier to align while welding.

    To cut the chamber I lined the chamber up in a 4 jaw (it was definitely not round) and then drilled a shallow centre hole in the exposed end cap so it could be supported by a live centre and then parted the chamber. Now I could see the ally was 2.4mm thick and would be able to turn an end cap onto these soafter removing 10 mm I turned 3 mm wide steps on each cut end. I deliberately made the steps a tight fit, so much so that when pushed together the two pieces snapped into place and they were very hard to separate.

    I gave the chamber to my brother and he just epoxied the pieces together and he's happy, BIL still wants his 6 pack for the advice provided.

  2. #2
    BobL is online now Member: Blue and white apron brigade
    Join Date
    Feb 2006


    Sorry Bradford, the breather chamber has been glued together and is already installed under the M/C seat so there's not much to see.

    Meanwhile here is an example of bros work and his shed helper.
    Attached Images Attached Images

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