5C Collet Chuck & Ball Bearing Spinner
I've had one of the cheap Asian
import 5C collet chucks for a long time. Mine is not an adjust-tru nor
even a Bison. I think I got it for $150-ish on eBay. I finally decided
I needed to get a backplate made so I could use it when I joined a team
build for one of the Verburg steam engines on the HMEM Board. My job would
include machining a little connecting rod that would be about the most
complex small part I've made so far. It's an ideal part for 5C collets
due to its size, the desire for precision, and the need for both turning
and milling operations. It so happens I also have a set of 5C collet blocks
and a 5C spin indexer for the mill. If I can get a chuck on the lathe,
I will be set!
I had done one
backplate before for a Buck 6-jaw chuck. It was one of my earliest
lathe projects and a thing or two didn't go exactly smoothly, so I decided
to try to do a few things differently this time around.
the Rough Stock to Size
The first order
of business is to cut the cast iron blank in half. There's enough meat
here for 2 chucks. My trusty DeWalt Multicutter is powerless against a
piece of iron this big, so the old bandsaw was pressed into service. Been
a long time!
More than enough
material here for the chuck. It sure is a precision looking thing, isn't
Re-Cutting the Collet Chuck's Bore to Be Concentric
With the Spindle Axis
I started out
doing an odd thing: I stuck a piece of junk stock in the 6-jaw, turned
it true, and then I put a collet in the collet chuck and stuck the collet
chuck onto my round stock....
Next I stuck
my Noga indicator holder on the lathe and checked the runout. About 0.002-3".
Then I got out
my little Circle Boring Bar and made sure the ID on the chuck was true
relative to the lathe's axis and the collet on a live piece of stock.
You can only take very light cuts this way, but the technique worked well...
I was out around
0.002" before truing. Now this is the most I'm out. Looks like maybe
2 or 3 tenths. I should be so lucky as to hold that tolerance when I get
it all put together!
Facing the Rough Stock Flat
Next I fired
up my Lovejoy indexable face mill and made sure the two faces of the stock
were flat. When I made the 6-jaw backplate I had no mill and had to follow
the common method of using a bolt as a spigot to turn on the lathe. It
was a mess: lots of chatter, lots of wasted material for the spigot, barely
enough clearance, yada, yada. Much easier with the milling machine!
Locating the Faux Cam Lock Holes With
Shopmade Transfer Screws
What's all this
then? I need to make a transfer screw in M10 to capture the hole locations
for my faux cam locks. You can order them, but they're expensive and I
didn't want to wait. I thought this would be quick and fun to do, and
it was! The two nuts are held by my chuck to protect their threads...
I set over the
compound for a 60 degree point and started cutting...
get to a point...
With three made,
I set them all to the same height within a thou with the surface plate
and height gage. Why? No idea, but it was quick and so I did it...
I slapped on
some marking dye, and while that was drying, I used the blocks to find
where the rough middle would be. Not a precision intensive operation as
the blank is much larger than the chuck and will be turned down anyway.
I flipped it
on the chuck, gave it a tap, then took it over to my worktable and gave
each punch mark a much harder tap. The centering isn't perfect, but it
Mounting the Faux Cam Locks
Using my centering
spigot to line up on the pips. I made the spigot one day when I was bored
on the lathe. It's handy!
I used 1 size
larger, a "T", in screw machine length for the M10 x 1.5mm holes...
I hate my crappy
tap wrench, but a new tap in slightly oversized holes in cast iron goes
like a breeze...
There they are
all mounted! Fits great on the spindle. Now I need a center hole...
Backplate Center Bore
My next trick is going to be
much harder. I need to place a bore for the spindle nose exactly dead
center of the cam locks. I came up with what is probably an overly finicky
and underly (is that a word?) accurate way of approaching the problem.
Before I explain what that is, let me just say that if I had it to do
over again, I would probably build a locating fixture that would sit in
the spindle bore of an existing backplate and locate the new backplate.
It would be a simpler and better way. For future generations, I would
do it thusly:
- Build a locating plug gage.
One end would be spindle bore sized and a very close fit on a finished
backplate. the other end would be a much smaller diameter to fit a hole
drilled in the new backplate.
- Start the new backplate faced
and with a center hole drilled to fit the plug.
- When using the transfer screws,
drop the backplate onto the plug pin before tapping. This would ensure
alignment of the transfer screws relative to the spindle bore.
- Finish by boring out that
center hold to the spindle bore diameter.
Meanwhile, since I didn't think
of that before going to far down this road, here is what I did on this
I want to use
the height gage to mark out a couple of crossed lines that will locate
the center of the bore. To create a datum or reference, I will rotate
the backplate in the angle block until the two bottom cam lock barrels
are exactly level. I can tell by measuring their heights. I choose two
because an alternative would be to rotate until one cam lock is at the
lowest point. I feel measuring two will be more accurate, but that could
be wrong, it's just an intuition.
them leveled, I measure the location of the top and bottom of the spindle
bore. In this case I used the scriber. After I had already gone much further,
I realized I could have done this more accurately by mounting a DTI to
act as a sensitive "feeler" in place of the scriber. That's
another one for future generations to ponder.
the top and bottom relative to the datum, I can now easily figure out
where center height is relative to the datum.
Now I want to
level two cam locks in the new backplate. I start off with a level to
get it close. I tried this three times and learned the level is accurate
to about 20 thousandths. Something to keep in mind for future uses.
We finish up
by adjusting untiil I can test height of both and the height gage says
0.000, which means there are the same height...
Then I move
the height gage up by the amount I calculate earlier and scribe a line
that intersects the center of the bore. The line is faint, but visible
in the dye...
Now rotate the
backplate, relevel the cam locks at bottom, move up 0.348" (whew!)
and scribe a second line. The intersection of these two marks the centerline
for the bore...
If you have X and Y DRO on your mill, you could figure the coordinates
of all these locations in a CAD drawing and just dial them up on your
DRO. You can even use the dro to measure the coordinates on an existing
backplate. Alas, I only have an X-axis DRO on my mill and no Y-axis, so
I'll use this height gage and work more laboriously one axis at a time.
As usual, I
pick out the intersect with my Starrett automatic punch, double check
it, and then hit it with the big hammer and punch. BTW, this first try
was off by about 10 thousandths when I double checked. Turns out I added
instead of subtracting when I figured the height. Remember: measure twice,
cut once! I went back and corrected the problem and got the center on
track relative to the holes, at least as measured by my digital calipers.
the Spindle Nose Hole: Part 1, Roughing It
I started with
a 3/8" screw machine bit, and then went to 1/2". After that,
I dug into my Silver & Deming bits and went 3/4" and then 1"...
How about that
big honking corn cob? The silly thing is 1.5" and it cut much more
smoothly than my 1" Silver and Deming twist drill. The main issue
is that it needed a fair amount of feed pressure or it would chatter while
Why all this
drilling and plunging? A boring head is a slow operation. I wanted to
get the bore as large as possible to minimize the boring head work to
reach final size.