[email protected] (Dave Williams)
mc-chassis-design  12 Aug 1999
- -> Nothing wrong with that Michael - a cylindrical is a handy
  -> machine to have but even big(ish) shops have trouble
- The original message mentioned a Landis, I believe.  Landis made some 
  internal grinders specifically for finishing cylinder bores.  They claimed 
  it was more accurate than boring and honing since the grinding operation 
  mostly eliminated errors caused by cylinder wall springback. I've been 
  keeping an eye out for one, but the only ones I've come across have been 
  expensive and far away.  Production apparently stopped around WWII.  They 
  work similar to the more common Hall-Toledo orbital valve seat grinders. 
- Tools are good karma, you know...

[email protected] (Dave Williams)
mc-chassis-design  13 Aug 1999
- -> That's grasping at straws. Grinding produces more heat too, so it's a
  -> toss-up whether there's more thermal distortion or mechanical.
- One would assume the use of coolant.
- -> rigid and inside a block it isn't going to distort more than
  -> millionths while machining it.
- Bikes normally have iron sleeves of constant thickness, well supported by 
  external fins or aluminum jackets.  Older automotive applications, back in 
  the days when Landis promoted their cylinder grinders, were neither.  
  Between core shift and designed-in eccentricity (some bores have extra meat 
  on the thrust side, for example), with the odd head bolt boss here and 
  there, the bore is not evenly supported.  During those days it was common to 
  take fairly large bites with the boring bar -.030 or so at one pass - with a 
  round nose bit.  The instruction manual for my 1950s Kwik-Way boring bar 
  describes that sort of thing in detail. But if you try it, you'll get a bore 
  that can have over a thousandth out-of-round on a modern V8 block; you can 
  also make the bore sort of Cokebottle shaped since the ends are supported 
  better than the middle, and the bit takes a deeper cut there.  I use a 
  several passes with a pointier bit and hone .004 or so off to come up on the 
  final finish. Honing has its own problems wrt. generating an eccentric bore, 
  but trial and error has shown that's what I need to get a proper cylinder 
  wall finish, which is basically a 600 grit mirror for modern moly rings. 
- Boring distortion would be negligible with a properly supported bore, but I 
  don't get to do many of those. 
- -> The real reason for grinding bores is that grinding is inherently a
  -> more precise process and you get the finish needed w/o honing.
- You'd have to use at least two different stones, one for roughing and one 
  for final finishing, but it'd be a lot faster and easier than separate 
  boring and honing steps.