Wandering vise, Is this a problem?

[TxBlacksmith]

While drilling out the taper pins in my cam, the very last hole i drilled, last pass or two?
The vise wandered a little out of position on the old drill press.  This hole is the bottom side of the exhaust
cam.  Will this be a problem?  Do I now need to go with a new shaft?  Gee I feel stupid! 

[Jordan]

So, you're blaming the old drill press!

A fix might be an oversized taper pin in a newly reamered hole?
Or just redrill and taper reamer to the standard in a different position?

[32 coupe]

Shoot, looks like a standard Indian job to me !

Someone will chime in with a fix.

Gary

[contaucreek]

Have someone fixture it up solid in a bridgeport and go oversize?

[LowGear]

Why is it a problem?  Honestly.

What is the mission or purpose of the hole?

Casey

[TxBlacksmith]

I am putting all new cam lobes on the shaft.  The old pins were hopelessly stuck.  So i drilled them out one by one with fractional bits. 
Somehow the shaft moved, vise slipped whatever, and now the hole is slightly enlarged and off center. My concern/fear is that this willl screw up exhaust timing, and/or create a clearance problem.

[32 coupe]

That is probably your best best......think I'd opt for a new shaft as well.

Gary

[38ac]

Moving an off center hole like that back to center and keeping the lobe properly timed is more involved that it would first appear. Everything tries to take the path of least resistance, which is not where you want things to end up. You will likely end up with a nice round hole,, in the wrong place, Good luck if you try it by hand or on a drill press because even on a mill it is a challenge.  Your best bet would be to start over with a new shaft. You need to make friends with a Bridgeport owner and have him drill you a new shaft and then buy a reamer from McMaster Carr plus the pins,,,, ya, it was an expensive ooops fixed correctly. I have the tooling and pins but all is tucked away as I move my shop operations or I would help you out,

[Tom]

I'll toss out an alternative opinion. Since the shaft is toast anyway, I'd just put the lobe in the correct location on the shaft and weld it into place by filling the hole. If it works great, if not most likely nothing lost.

[LowGear]

Have you considered just putting it back together and seeing what happens?  How much work is it to R & R it?

Casey

[BruceM]

If it was a Rajkot cam instead of an original I'd say that looked like a typical stock hole, and would just clean, JB weld lobe and pin to take up slop.  A classic "farmer fix" which I think would work well as the crankcase/cam run so cool in these engines.  The placement is so inaccurate and holes so off center on Rajkot cams that you might have improved things by accident.

Tom's weld suggestion is nicer, and has been used by others with way off lobes that had to be shifted.

For a high quality original restoration, I'd read 38ac's advice very closely.

[TxBlacksmith]

Here is the underside of the hole, lobe removed, with a new pin just pushed in place.
Maybe not such a problem?

[EdDee]

Hi TxBs,

What about this...

Clamp the lobe to the shaft in the correct position, ream it slowly and carefully by hand, keep reaming until the hole just cleans up on taper all the way, allow the reamer to average in the hole if possible, carefully cross force the reamer to bias the cut towards the area that needs it most, above all, take your time go slowly, and don't be afraid to inspect it under bright lights..... Install an oversize pin tapping it in lightly and peen it lightly on the small side if you have had to go more than about 10% oversize on the hole... try and keep stresses from fitting as low as possible...

This is not the correct way of doing things, but it might just be an out that suits you....

Regds
Ed

[George A]

Assemble the cam to the shaft. Drill both pieces through with a STRAIGHT bit. Heat a STRAIGHT pin until bright red and insert. Quickly peen the ends over. Just like a hot rivet, the pin will shrink (draw) as it cools with a grip that will never let go. If worse came to worse, you could always drill it out on a Bridgeport.

Oh, as for any inaccuracy? At this point you can at least save what you've got.....the point has already been made that you might have improved it.....!