The revival of 650143R, 1970 with TS.

[Richard48Y]

Third time the charm?
I have ordered another adjustable cam gear and hub.
All I really needed was the hub.
At $200 each I HAVE to stop ruining these.
I cannot get dry ice locally so may give in and have a machind shop do it for me.
A "Galling" situation.

[BDA]

Good luck! That sounds really frustrating and expensive!

[Richard48Y]

At least my front bumper only had to be chromed once, $700.00. 

[Richard48Y]

I am about sick.
I gave in and had a local machine shop make the third try on my cam gear.
Cost me $100 and is ruined again.
So I will have to get yet another.
Something must be out of spec here.
I am beggining to think the cam nose is an RCH too large?

[jbcollier]

The interference fit must be too tight.  You could also heat the hub prior to fitting, just like you do with an axle bearing retainer.

[Richard48Y]

Machine shop heated the hub and chilled the cam nose in dry ice, still no good.
They are saying .004" fit.
I am going to contact CAT Cams to ask for the correct cam nose specification.
Not sure where I could get this one reduced, needs to be ground not just turned. 

[GavinT]

I'm no engineer, but...    (don't ya love it when people start out like that)
Anecdotally, - 0.004" seems like an extremely tight fit given the shaft diameter.

There's a wealth of tolerance charts, materials ect. out there, but I found this site:

https://www.engineersedge.com/calculators/mechanical-tolerances/force-fit-tolerances.htm

In the calculator, I selected "FN2" as the fit type - the suggested maximum for high grade cast iron.
I entered 1.00 inch as the shaft diameter.

The calculator output for interference fit suggested:

Max = 0.00190 inch
Min = 0.00060 inch

Any thoughts from our resident engineers?

[TurboFource]

Richard couldn’t it be honed to size on something like a Sunnen?

[Richard48Y]

I have to get an exact measurement of the camshaft nose.
Then I will do the same for the new hub.
With that I think honing out the hub will be safer than trying to reduce the camshaft nose diameter.
It is unfortunate that with all the tools I have I still don't have what I would need to do this myself.
I can't really justify it for one time use.

[dakazman]

Machine shop heated the hub and chilled the cam nose in dry ice, still no good.
They are saying .004" fit.
I am going to contact CAT Cams to ask for the correct cam nose specification.
Not sure where I could get this one reduced, needs to be ground not just turned. 

Hey Rich, I believe I still have a cat cam sitting in my shelf I can measure it tomorrow.
Sorry to hear about your troubles.
Dakazman

[Richard48Y]

I am strongly suspecting mine may be just a literal fraction oversize.
I do not have an original cam to measure for comparison.
I have sent an email to Cat cams, I hope they answer quickly.

[jbcollier]

4 thou press fit on that size of shaft?  Way too tight as you already know all too well.

[Richard48Y]

Measured my cam nose, it is .0003" over maximum.
That really should not be enought to be such an issue.
On the next try I will have help from a guy who can measure with pin gauges before and after heating.
He has the proper oven and infrared temp gun.
We will exactly know much it will grow at 700º - 800º.
Goal is that it DROPS on this time.
If it does have to be honed I will get that done.