"Moving" Axle Pivot Hole in the Casting

[ri702bill 11,077]

All:

The center pivot hole in the C81 Axle had a bit of wear, so I decided to drill & ream it for bushings. Upon closer inspection, I noticed the hole was visibly not centered in the boss; I decided to correct that as the best I could. The 3/4" ID bushing has a 7/8" OD - I could use a Boring Head and safely relocate the center about 2/3rds of the 1/16" bushing wall thickness and still have material left to ream to size. If I had a larger wall bushing & reamer, I could have re-centered it....

First photo shows the new center moved .040 with a light cut. The second shows the interrupted cut as the boring bar is moved outward. Third shows the hole at .840 diameter where it became round again. Last photo is the finished reamed .875 diameter hole.

 

[kpinnc 16,802]

I've seen that before as well. More than once now that I think about it. 

 

Much like the axle bores in a Unidrive, I figured it was just the location some engineer decided on, and the jig used just repeated the same thing... 

 

Excellent work relocating. Looks great! 

[ri702bill 11,077]

12 minutes ago, kpinnc said:

Much like the axle bores in a Unidrive, I figured it was just the location some engineer decided on, and the jig used just repeated the same thing... 

The axle looks to be a sand casting - who knows how many times the Pattern was used, repaired, etc.??

There is a void in the middle, the same in the spindle bores... cuts down on the shaft guiding but gives a place to store grease... Wonder how they did that??

Edited December 22, 2025 by ri702bill

[ineedanother 1,830]

Nice work @ri702bill. I've considered getting a reaming bit for my drill press to do this although that would be a considerably less-skilled approach. I wouldn't attempt to center the bore but I think I could fit bushings well enough to remove some of the play that seems to be an issue with most of my c-series axles.

[ri702bill 11,077]

The pivot holes elongate at the top from the weight of the engine; the canted spindle bores get elongated on opposite sides, top & bottom from the offset of the wheel.

The key is the lineup and clamping the axle - not just down to the table, but also to eliminate it rotating if (when) the tool bites into the metal.....

[Handy Don 15,692]

4 hours ago, ri702bill said:

Third shows the hole at .840 diameter where it became round again.

Nice work!

This sentence just tickled me -- I’m visualizing the hole magically morphing itself from wallowed and off center to more centered and round!

[ri702bill 11,077]

Look again at the second picture. The dark portion of the wall is the original wallowed out part - the shiny part is the new cut at a bit more than 50% of the hole. Each pass the new cut gets longer, until the ends meet as they did at .840... the hole was both moved & round....

[ebinmaine 76,891]

12 hours ago, ineedanother said:

Nice work @ri702bill. I've considered getting a reaming bit for my drill press to do this although that would be a considerably less-skilled approach. I wouldn't attempt to center the bore but I think I could fit bushings well enough to remove some of the play that seems to be an issue with most of my c-series axles.

 

 

12 hours ago, ri702bill said:

.

The key is the lineup and clamping the axle - not just down to the table, but also to eliminate it rotating if (when) the tool bites into the metal.....

 

 

Seconded. 

 

I've done this repair by hand. It worked okay but obviously a drill press or other proper machinery would be a huge improvement.

 

 

 

Bill, nice work on this one.