semi finish bearings / resizeable bearings / full floater

[Ingo]

Hello Guys,

since i have a rod bearing damage and figured out my crank was allready grinded 0,030 under i bought a set of semi finish full floater bearings / resizeable bearings. Has anbody of you anytime cut / bored those bearings to size and can give me advice how to get them fit?

thanks all

Ingo

[scooder]

Look up Walt on here, pretty sure he's had a lot of experience with these semi finished bearings.
Martin.

[Ingo]

ha thats funny, Walt was it who recommend to post my question here in the barn. As i understand him he used those bearings back in the 60s but he gave it to a machineshop to cut them to size. So he personally doesn´t know how to do it...

[flatheadmurre]

Semi finished just means the bearing is maximum undersize with a bearing material thicknes enough to resize it to less undersize.
On a fixed bearing its just to install it in a rod and hone.
On a full floater you need a fixture to hold it tight making sure its round before sizing.

[Ingo]

Originally Posted by flatheadmurre

Semi finished just means the bearing is maximum undersize with a bearing material thicknes enough to resize it to less undersize.
On a fixed bearing its just to install it in a rod and hone.
On a full floater you need a fixture to hold it tight making sure its round before sizing.

Thats it! I considered to bore a sleeve on my lathe, put the bearing in the sleeve (as tight as possible) and then bore the bearing to the needed size. I just wonder if anyone has some special advise ...

[Walt Dupont--Me.]

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You got it pretty right INGO. I cut many many semi bearings back in the 60-70, My brother use to turn cranks and also with portable crank grinder. A lot of trucks would spin a rod bearing and bro would grind journal in the truck, he would call be back in the shop and I would cut a semi bearing to size. Also ground many semi pistons. Those jobs are about all gone now. It would pretty hard now to find a shop that has any of those machines. Simple things like knulling pistons and installing spacers in worn top ring groove. The younger generation are missing all that fun stuff. Walt

[motordr]

Look up Tobin Arp bearing resizer on Google and you will see the way it is done.

[Bored&Stroked]

The Tobin machine is essentially a 'line bore machine' for bearing shells and/or caps. If you can find somebody who has one and knows how to use it, then this would be a good approach. I believe you could make a one-off custom holder that would work in a lathe - specifically for the full-floater 91A/21A bearings you have. If you want me to draw you up a 'fixture' - and then you could have it made, ping me off line. There are guys with the Tobin machines - you should be able to just send them your bearings and the crankshaft dimensions . . . if you can find "that guy". Good luck

[deuce_roadster]

Making a fixture for the floaters, getting machine work done etc. seems to me would cost a whole lot more then just getting a good crank that is ground to the size of the good throws and getting 1 pair of new shells for throw that was damaged. Or even having the 1 throw welded up and ground back to the size of the rest.

[JWL]

Yes, I have some suggestions after having performed this operation several times---the OD of the bearing shell should be clamped such that it is perfectly round and matches the diameter desired to fit the rod housing. Just boring a sleeve to be a tight fit on 2 bearing shells will not do it correctly as the gap between the 2 shells will likely cause the sleeve bore to differ from the rod housing and getting the bearing shells to perfectly conform to the sleeve bore will be a challenge. But, if the shells are not tight in the sleeve, all around the outer perimeter, the shells will have thick-thin conditions when re-bored.

I did one set in a lathe where I tapped the oil holes and screwed the shells to a bored sleeve. My results were just "ok".

Your results might vary.

[Bored&Stroked]

JWL has a good point. Maybe a good approach would be to create the fixture and then use some .001 or so shim stock all around the outside of the bearing - to simulate oil and clearance. I'm just talking out loud. If it was me, I'd find a replacement 59x or 8BA crankshaft and not screw with it (but he already knows that part from me! LOL)

[Ingo]

Tanks guys for your tips, i´ll try and Keep you posted

Ingo

[Yoyodyne]

What year engine are you working on? I have a pair of flanged .040 under bearings I don't need.

[Kurt in NJ]

I dug out this Sunnen bearing sizer, it has a proper sized insert holder, I have the instructions, a few pieces of tooling are missing but not hard to make, it was all stuck not moving with congealed oil I got it freed up some but it needs to be taken apart to free up the feed

[Kurt in NJ]

The phone only loads one picture

It uses the sunnen machine to adjust the cutter, looks to be somewhat trial--error to get size, the instructions say to take a cut and measure, each graduation on the machine dial is about .001----seems like it would take some practice to be consistant---it does look like the insert can be removed without changing the setup so once the inserts were close the final cut could be repeated by just changing the insert, no change in cutter depth

[flatheadmurre]

Thats a nice little attachement.
Big i want one factor...another one to the list of stuff to find.

[Ingo]

Originally Posted by Yoyodyne

What year engine are you working on? I have a pair of flanged .040 under bearings I don't need.

sorry i wasn´t there a couple days. I have a 39-42 engine without flanges bearings.

Thank you

Ingo

[Ingo]

Originally Posted by Bored&Stroked

The Tobin machine is essentially a 'line bore machine' for bearing shells and/or caps. If you can find somebody who has one and knows how to use it, then this would be a good approach. I believe you could make a one-off custom holder that would work in a lathe - specifically for the full-floater 91A/21A bearings you have. If you want me to draw you up a 'fixture' - and then you could have it made, ping me off line. There are guys with the Tobin machines - you should be able to just send them your bearings and the crankshaft dimensions . . . if you can find "that guy". Good luck

Dale, i would be glad when you draw it for me.

Thank you

Ingo

[Bored&Stroked]

Okay Ingo - I'm working in CAD this evening, will send it your way . . . both the 3D CAD model as well as a 2D drawing.

[Bored&Stroked]

Here is a screenshot of the bearing holder - designed it in SolidWorks. I'd make it out of 6061 Aluminum. It needs to be dead-nuts correct in the inner bore - so the bearings sort of 'press in' by hand. The depth of the pocket leaves about .005 of the bearing sticking out - so the top plate can be used to hold them down and in position.

I made four 'relief' holes (1/2") that go all the way through the main part - so that one can use a wooden dowel rod or something soft in case they need to "tap" the bearings back out after the machine operations (from behind). I usually forget crap like this - than wish that I didn't!

Can't say that I've ever attempted to 'bore bearings' on a lathe, but there is no reason it can't work if the machine is good and the operator knows how to do precision work.

If anybody wants a copy of the CAD model, just ping me . . . not a big deal by any means.

B&S

2-14-2016 1-26-16 PM.jpg

[flatheadmurre]

How about a thickwall tube with the inside turned to correct size.
Mill half of drill and tapp for 2 pieces holding the bearing half in place.
Preferably the last finish cut of the inside diameter would be done in the same setup as the sizing to prevent any offset in the chuck to give offset/angle in the bearing.
This way you take the pressfit out of the picture.
Would be faster setup.
What a trainwreck of a drawing compared to the nice solidmodel

[Dodge]

Measure your crank and send the bearings to Ron's Machine Shop in Shandon Ohio
(513)738-7353 call and ask them about it.

[Bored&Stroked]

I've seen these guys (Ron's) at shows - certainly appear to know what they're doing. Also, since I am in Columbus, be happy to relay them to Ron's if you send them my way. Happy to help guys who are trying to get their flatheads up and running.

[Ingo]

Update... so on my lathe i made the bearing holder and the plate for pulling the bearings out (i made it simple)

[Ingo]

...and than i bored the bearings to the needed size

[Ingo]

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pulled it out and bored the next one...it seems to work okay. Now i have to bring the rods to the machine shop to grind the big end bore.

[Bored&Stroked]

Hey Ingo - glad that a simple version of my basic design worked for yah! Let us know how everything works out in the end . . . always curious to see the end results!