Box Cam Desc 48-08 question

I\'m getting ready to start on my box cam and breech casing and noticed in the Desc 48-08 that the material listed as 3\" O.D. and 2 1/4 I.D steel tube, shouldn\'t that me 3\" O.D. and 2 1/2 ID. Also are their any gotchas I should be aware of? I have looked at all the pictures here on the forum and have been dreading starting these parts.  Thanks!

Bob

Hi manatee,
Are you doing your cam on manual machines or CNC ?

Cutter

Cutter,
I\'m doing it on a manual mill with a DRO.

Bob

Ok Bob,
Here\'s a process I\'ve used in the past.

I used 3.00 OD with .312 wall DOM tubing.
Cut to length and turn OD to fit your casing.
Counter bore and put in the 2-56 holes, and the .500 slot.
I put in two 8-32 holes on each side of the .500 slot.
The rear section of the Cam will open up when it\'s cut through.
Makes it easy to put & take.
Cut the Casing to length.
Then put in your mounting holes for the two pieces.
Remove the Cam and mount it on a fixture. ( Here\'s mine )
Plunge to .200 deep as you step.
Mount it back in the Casing and bore to 2.52 dia.
Then you can take it out using  8-32 screws.
Deburr and polish.

Here\'s some pictures
I have a peice of tubing if you want it.

Cutter,
Thanks for the info.
Why the .312 wall DOM?  Paul sent me tubing that is .2485 OD. I ordered an extra tube and brass casing just incase  I screw the first one up. I also ordered some 2 5/8 alum tubing to make a fixture to hold it on the lathe and mill. I\'m planning on ordering a Tormach 1100 next month maybe I should just wait until I get it. Another question, when did you drill the side holes in the brass frame parts that hold the breech casing?  The sequence of doing things in the plans in confusing to me at times!
Bob

Sorry that was 2.485 ID.

Using .312 wall keeps it together.
Remember the finish bore is 2.520 dia.

I don\'t use the RG-G frame, so no mounting holes there for me.

I think anyone who has made a Cam manually would say wait for the CNC.

I made mine on a Tormach 1100 with a 4th axis (code is posted here somewhere)  What I did was make a mandrel to go inside the cam tube (backyard-cast some scrap Al into a bit of the tube) and bolted it inside with four bolts that later hold the cam in the outer casing, then put a tailstock into the end to help hold it.  The point of the mandrel was not to lose the far end once it profiled through the material on the cam track.

After I got done faffing around cutting the part with the tailstock and mandrels and so on (holding everything how it would be after it was all assembled), I realized it would be a lot easier to make the cam in two separate pieces and profile each separately on the 4th without any of that.  :oops:   If you have enough material, I suggest doing it that way.