Note: This project has been on hold
since March of 2014. I need to machine an arbor to hold a 1" bearing
block to hold a 13/16" round plumb level to the mill head. Then
things got quite busy, and the project dropped off. Now the jig
would allow me to machine some T/C Contender sights and forends _IF_
I get down to brass tacks and finish it...
As always, disbelief, comments, experiences, may be sent to me HERE
In my plan for world domination, or at least a
repeatable T/C Contender forend and rear sight jig, I ran into a wee
problem. The 13/16 x 18" 12L14 round was spot on, the 13/16 ID
bronze bushings slid snugly over the ends. Then I got beat about the
head with an empirical lesson in differences in tolerances.
Sleeve Bearing and Shaft End Support
BUNTING
BEARINGS, CB131612, Cast Bronze C93200 (SAE 660)
Sleeve Bearings , I.D. 13/16, L 1-1/2 OD is @ 1.004"
Bearing
OD is too Big for Support ID!
Slip the bearing over the 13/16 rod, drill and pin it, chuck it up
in a lathe, then skim cut using a sharp tool (HSS from Warne).
Shaft Alignment to the Mill Head
By the time I was done, it varies about a thou and a half over four
and a half inches. Close enough. The 5C 13/16 collet is used to get
the rod as close to center as possible while being lazy as possible.
Measuring Table to Shaft Support Base
Ran into a real stump the chump thing on measuring
the distance from the mill table to the bottom of the arbor support.
Tried my Starrett electronic calipers. No go, but the method I used
points to an answer. In this case I whipped out my (depressingly
cheap) import telescoping hole gauges, used a flat of 3/8 steel
(actually .373") to get a flat surface, then measured the distance
from the steel to the arbor base a few times to be sure, then added
both heights. Height from base to table is 1.758"
Now that is just about the same way to allow the use of the inner
measuring jaws on my caliper, put some parallels on the table and
use them to make things right.... Whatever....
Here is the turned bearing installed on the 13/16
rod. This will cut set-up time way down, since the angle of the head
is pre-set by the block below the bearing block. All that I
need to do is drill a positioning hole through the split in the
bushing block, then I can stick in the pin, which orients the rod at
zero degrees, rotate the 5C head down to the table, then I tighten
up the three-jaw chuck. Rod is now indexed to zero up and down. A
little tapping on the 5C fixture base to get alignment (with
indicator on rod) to get front to back square, then tighten it down.