Drilling Main Bearings ??????

[GUMBALL]

Background.................

We are building an FE and have been advised to drill holes in the upper shells to align/match the diameter of the oil feeds in each saddle. This should aide oiling to the mains as the standard shells are groved in a manner that restricts nearly half of the oil feed hole.

We were advised to use a step drill bit to prevent drill slippage.

After drilling, the bearing material raises slightly on the outside edge and needs to be filed smooth. (not unlike most drilling or sawing on metal surfaces) Filing the inside groove on a main bearing scares me as the tolerances ar so tight.

Question......................

Does anyone know the method to accomplish this?

Or, do we need to take the bearings to a machine shop and let them work their magic?

Any help would be appreciated.

Regards,

John

[mickmate]

John, the book I keep under my pillow says the bearing bores for the crank and cam are not in perfect alignment so the oil holes are off center. Don't worry about the off center holes check the size of the opening. A drill bit shank can be used to check the size of the hole.#1 is 17/64, 2 is 9/64, 3 is 9/32, 4 is 5/32, 5 is 9/32. They shouldn't just be opened up as a bigger hole is less restrictive and may cost you in oil pressure where it's most needed. If you check them to the numbers given and they need opening up I would recommend a straight flute or at least a low helix drill with something that thin and soft. The other thing is to modify a drill point to no rake on the cutting edges. A chamfer tool will deburr the hole effectively after drilling.
Hope this helps
Cheers Nick

[GUMBALL]

Mickmate......................

Thanks for the advice. Since my original post, I contacted my local machine shop and they advised to chamfer the drilled holes with a deburring drill bit. (just as you noted) The job came out fine. Thanks again for taking the time to help.

Regards,

John