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Line Borer

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e coutts18/03/2010 11:02:29
6 forum posts
I want to construct a manual line borer for my old car main bearings. I have certainly heard of various simple  home made designs, some manually driven and others driven by even battery drills, but haven't seen any in action and enquiries have come to naught. Has there ever been published designs?any help welcomed.
KWIL18/03/2010 11:50:59
3681 forum posts
70 photos
As I recall, production tolerances on old car main bearing were quite tight, with cylinder bores measured to 4 decimal places and using matched pistons. That said, you could consider a mandrel supported in two ball bearings, the outer of which fits the bearing housing or is mounted so to fit and then using a cutter mounted through the mandrel to cut the other renewed bearing shell, assuming it is a white metalled one and you  have a 3 bearing crankshaft. It would be quite slow because you would have to take the final cut at the same settings on all bearings, unless your crankshaft is unequal anyway.  An idea for discussion perhaps?
Jeff Dayman18/03/2010 12:28:57
2356 forum posts
47 photos
what model and year car are you working on?
 
north american cars from 1900 to 1930's had generally loose tolerances, but after that got a lot tighter.
 
do you have a rebuild manual? all specs should be there if so, and that will dictate what lashup you need for line boring.
 
my grandfather was a car mechanic 1917-1976 and I watched him do a number of old engine rebuilds. for some Ford models he would centre the bar in the existing bearing caps with a tapered wedge at each end of a fitup bar, and this would allow bolting a bearing plate at the wedge-derived centres to each end of the block - there were tapped holes provided in the block. old babbit was then removed, fresh babbit poured in undersize. He then swapped in the boring bar for the lineup shaft and drove it with a portable drill to bore the new bearings. A quick blue-up and scrape, a two-cigarette paper clearance check with the crank and caps, and in went the crank for good.
e coutts18/03/2010 22:02:31
6 forum posts
Thank you to both Jeff and Kwil for their replies. The car is a 1910 SCAT. I have done one of these motors and allowed .002" bearing clearance  and .002" end float which seems to work OK . The reason I want to build my own is that with another motor to do,the last engine rebuilder charged me more for the set up than the boring which was fair enough,as the motor has big mounting legs either side and won't fit into the modern style line borer.The crankcase is alumium and has to bored to establish a true tunnel , then I make bronze inserts to fit and white metal them and then bore them to suit the crankshaft.
russell19/03/2010 01:30:06
142 forum posts
I'm sure i can recall reading about someone doing this, almost certainly in an old model engineer. Just had a quick look at a on online index, but i cant find the article.
 
need to guess the right search terms. It may have been a 'duplex' or 'geometer' article - maybe 'artificer'
 
regards
 
russell
e coutts19/03/2010 06:22:23
6 forum posts
Hi Russell,
Thanks for the info. I only subscribe to MEW so the system won't let me look at past Model engineers. perhaps someone with a photograpic memory can add something
 
Cheers,
Euan

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