Line boring

  • 15 Mar 2018 11:37 AM
    Message # 5980288

    I am replacing the timing side main bearings on an Ariel Square Four MKII. The replacement bearings are approx. .100" undersized and must be line bored to the correct size. The crankshafts do not require regrinding.

    I am looking for a machine shop, preferably in the GTA that can do this work.

    The ones I have contacted can only bore on a vertical mill but not line bore.

    Regards Paul


    Last modified: 15 Mar 2018 11:44 AM | Paul
  • 15 Mar 2018 2:54 PM
    Reply # 5980685 on 5980288
    A.
    Paul Kotyk wrote:

    I am replacing the timing side main bearings on an Ariel Square Four MKII. The replacement bearings are approx. .100" undersized and must be line bored to the correct size. The crankshafts do not require regrinding.

    I am looking for a machine shop, preferably in the GTA that can do this work.

    The ones I have contacted can only bore on a vertical mill but not line bore.

    Regards Paul


    Maybe KPS in Oakville? (Have not had to use them myself.)


  • 15 Mar 2018 3:28 PM
    Reply # 5980721 on 5980288

    KPS certainly has an interesting website. I'm looking for recommendations on their work. The crankcases are not replaceable, hence my caution.

  • 25 Mar 2018 3:26 PM
    Reply # 5996717 on 5980288

    You have to do similar work when you install camshaft bushings in older large automotive/marine engines... they also come undersize & have to be line reamed to the correct ID size after being pressed in to place. For that you use an adjustable hand line reamer & extension with moveable tapered centring cone similar to what a brake drum/rotor lathe uses.

  • 30 Nov 2018 11:48 AM
    Reply # 6939702 on 5980288

    Ken did you get your engine line bored ?.

  • 12 Dec 2018 10:41 AM
    Reply # 6956811 on 5980288

    Paul, this is how I did mine.

    I bored the bushes on my little oriental lathe (lol) as nicely and as concentric as I could to within a few thou (-005") of final size. Then after installation in the crankcases I used an adjustable reamer (size H13?) with a made-up alloy bar shaft extension fitted, to line-ream, rather than line-bore. I found a fairly cheap Indian-made adjustable hand-reamer on Ebay, but if possible you should beg/borrow/steal a better-made one if you can. The shaft extension slides through the centre of a turned-up plastic centering piece that itself fits into the drive-side roller bearing inner races. At the end it has a jammed-in 3/8" UNC bolt head that can be used to turn the tool with a socket and wrench. I was able to do an acceptable job (imho) by gradual light cuts, passing the reamer all the way through to ensure parallelness, and frequent trial-fittings of the crank. The crankcases were on their sides to give a vertical cutting axis. A spot of oil on those two location dowels makes trial cuts and fittings easier. I am using lead-bronze bushes, and the reamer cuts/shaves quite nicely. However, for babbitted bushes you might have to stone off some of the blades' cutting edges, or somehow find a spiral-blade reamer or something more exotic.

    Last modified: 12 Dec 2018 10:42 AM | Andy
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