Line boring main bearings

Marklambert61

Marklambert61

Member
Team,

Trying to come up with a set-up on my Bridgeport mill or maybe a lathe to line bore the main bearings to accept bearing inserts.

Any other machinist types out there that have already been through this process?

Mark
 
Marklambert61 said:
Team,

Trying to come up with a set-up on my Bridgeport mill or maybe a lathe to line bore the main bearings to accept bearing inserts.

Any other machinist types out there that have already been through this process?

Mark
Click to expand...

I made my own. It is just for the A engine. I use a 90 deg angle head in my Bridge port mill, with a long bar that is supported, front and rear.
 
It may take a little effort, but using the lathe and bridgeport you could make a fixture and a bar, some locating fixtures for the cam-crank location --

i would think that even with a very tight bridgeport it would be very hard to get all 3 bored exactly in line and at the proper place for inserts -without a fixture--perhaps with babbitt you could make it a little small and scrape the crank into place ---and if you screwed up you cam pour it again---if you screw up for inserts you have to try again on another block.

I don't think the 'average" bridgeport is tight enough-when I was looking it was hard to find one that the table moved in a straight line--many were over .005 off over the length of the table--but if i had to use it I would start in the babbitt ,see how close I could get, come up with reference points to measure from so adjustments for machine wear can be compensated for ---

Even most shops that do line boring on "chevy" blocks wouldn't have the equipment to properly locate the crank in an "A", wander on these sites some-- http://www.fordgarage.com/pages/kwikwayinstructions.htm, and http://fordfarm.net/TBabbittToolsLinks.html --

The first time before I had equipment I scraped in a .020 crank into worn .030 babbitt, then I got a lathe and used it to move a KRW fixture, I don't think that a krw fixture is tight enough to cut iron without chatter, and it was intended to be reamed after the use of the boring fixture, then I got a good deal on a Kwik Way ---and a better deal on an Aamco 400 ---keep your eyes open, look on craigslist, I got the Aamco for 40$, the guy just wanted more than scrap valu for it, I called 2 weeks after he posted it
 
I had 2 or 3 photographs of a set up on a Bridgeport that was used to align bore a B block but I had a serious computer crash and lost them. I had thought to duplicate it and leave a few .001"s and have the mains align honed.
It used a 90 degree head and aluminum plates bored with bronze bearings to maintain alignment and support. The boring tools were an off the shelf item fitted into what appeared to be a 2" dia bar and spaced to cut all 3 saddles at the same time.
 
just plain bill said:
I had 2 or 3 photographs of a set up on a Bridgeport that was used to align bore a B block but I had a serious computer crash and lost them. I had thought to duplicate it and leave a few .001"s and have the mains align honed.
It used a 90 degree head and aluminum plates bored with bronze bearings to maintain alignment and support. The boring tools were an off the shelf item fitted into what appeared to be a 2" dia bar and spaced to cut all 3 saddles at the same time.
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That is the way I do it also. Except I use steel plates with bronze bushings. The front plate locates off the cam bearings and pan rail, the rear bushing locates off the rear main. The cam gear mesh is always right, and the crank is in line with the cylinders.
I did look for a picture, but could not find one.
 
I agree with Kurt in NJ, Unless you have a mill that's Ways are in exceptional shape, I don't believe the table, quill, and head will be solid enough to keep the vibrations down to a manageable level for a good boring process. Most older Bridgeport’s aren’t that tight especially if you are feeding the table. JMO
 
Now fellas don't laugh, but I made a boring tool out of a block of aluminum that I bolted to a steel plate with a 3/8" barstock with a ground down forstner bit for the cutting tool and rebored a rear main bearing after pooring new babbit for the block for my nephews big iron AA truck. It ran good, but I couldn't tell you for how long. {:
 
I had Gene build me a custom jig with a 1.5" bar instead of the standard 1.25". It works pretty good. I drive and feed it from my lathe with a splined shaft. I am not sure how long it will last though...
 
Dave in MN said:
I had Gene build me a custom jig with a 1.5" bar instead of the standard 1.25". It works pretty good. I drive and feed it from my lathe with a splined shaft. I am not sure how long it will last though...
Click to expand...
I think he builds them in aluminum because most are going to use it once or twice and aluminum is easy to machine. It would be better if he built one out of steel or cast for builders.
 
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