Eccentric Hole in Bearing

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mortier
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Eccentric Hole in Bearing

Post by mortier »

I want to make a camshaft bearing for a 1924 Citroen. The damaged original (see photo) was of cast iron. I want to turn a new one of bronze. As you can see, the I.D. is off-center. This was necessary because of its position in the crankcase. The 2 bolt holes are critical to the alignment, also. The O.D. is 42mm, the I.D. 24mm. I can understand how to turn this part were the hole centered. Any tips on how to locate the off-center I.D. accurately? I do have a 4-jaw chuck.

Phil





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mortier
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Eccentric Hole in Bearing

Post by mortier »

Here is a drawing of the part (though the numbers aren't very clear).

Phil

cames.jpg
Rich_Carlstedt
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Re: Eccentric Hole in Bearing

Post by Rich_Carlstedt »

Start off by doing the ID first. That will make it easier to know what the offset is when turning the OD by using
a dowel pin in the bore for measuring offset
Rich
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Bill Shields
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Re: Eccentric Hole in Bearing

Post by Bill Shields »

Why bronze? Didn't the original last long enough? :mrgreen:

Anyway...I would make all except the finished ID...

Start with a rough ID that is on center but small enough to finish out eccentric.

Make a fixture to hold in a mill where you know the locations of the flange screws relative to the center and the axes of the mill.

Move off center and bore it to size.

This assuming that you have a good boring head and the mill has a power feed on the quill.
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GlennW
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Re: Eccentric Hole in Bearing

Post by GlennW »

First bore the proper size hole in the stock that you are going to use and finish it to the proper length.

Make an arbor to fit the hole.
DSC03962.JPG
Put the original part on the arbor and chuck it up in the four jaw and adjust the chuck until the OD of the part runs true using a dial indicator.

Remove the original part from the arbor and install the new part/stock.

Turn to the proper OD and add the required features.
Glenn

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Bill Shields
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Re: Eccentric Hole in Bearing

Post by Bill Shields »

I thought the original was worn and required replacement ...
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choprboy
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Re: Eccentric Hole in Bearing

Post by choprboy »

As an alternative to making an off-center arbor (or moving the part in the 4-jaw chuck), do you have a mill in addition to the lathe? If so, turn the OD and flange, then mount it in the mill, find the center, and then offset the desired amount and drill/bore the center hole and screw locations.
mortier
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Re: Eccentric Hole in Bearing

Post by mortier »

Thanks for those ideas. I'll post a photo when it's done.

Phil
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Bill_Cook
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Re: Eccentric Hole in Bearing

Post by Bill_Cook »

I think I'd look into boring the bearing and making a 660 bronze bushing to press in assuming there is part of the bore or a chamfer to indicate the offset and clock position accurately.
BC

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rudd
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Re: Eccentric Hole in Bearing

Post by rudd »

Easy. Put stock in lathe. Turn OD. Put DI on stock and use chuck jaws to move it over offset dimension. If I am reading your drawing right, that is square root of 8 units.
Drill, bore, ream center hole.
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