From: Doug Jackson <actionj@io.com>
Newsgroups: rec.crafts.metalworking
Subject: Re: Installing table power feed
Date: Sun, 12 Nov 2000 08:00:29 GMT

Mike Graham wrote:
>
> On Sat, 11 Nov 2000 04:01:17 GMT, Tony wrote:
>
> >One end of your table should have the bearing bracket with the captured
> >table screw bearing. This will provide the thrust bearing that is necessary
> >to keep the table screw in position. The other end of the table (right side)
> >has the power feed with the supplied bracket and needle roller bearing.
> >After that you may need to make shims as needed, and you may even need to
> >turn/face something to get it to fit together. The dials may also need
> >shimming to prevent binding. Save them for last.
>
>   I installed it this morning.  It was way more of a prick than I expected.
> Getting the right number of shims in there was a real pain, because the feel
> would change as I tightened the nut on the handwheel.
>
>   As it is, it works, and doesn't seem too tight on the bevel gear, but the
> handwheel is significantly harder to turn than it used to be.

	When I adapted my 135 in-lb HF power feed for the mill-drill, I took
one look at the way it was "supposed" to be installed (with shims
between the handwheel and bevel gear to set the axial position of the
bevel gear, as you seem to be describing) and decided that this was one
design shortcoming that I wouldn't put up with.

	Mating gears should be aligned with each other via ONE chunk of metal,
dang it!

	I sounds like your powerfeed is designed similarly to mine- with axial
alignment between the bevel gear and its pinion maintained via the
handwheel shims, the handwheel, the handwheel nut, the leadscrew, the
leadscrew thrust bearings, the table, the powerfeed mounting bolts, and
the powerfeed housing, plus any other parts in between (such as a
leadscrew extension, depending on the mill.)  This is ridiculous.  If
the handwheel nut backs out under vibration, or if the leadscrew
stretches a bit under heavy torque, etc... the engagement depth on the
bevel gear changes.  This wears out gear teeth in a hurry.

	What I did was to make a new inner race (journal) for the needle
bearing.  The new journal includes a flange on the end opposite the
bevel gear that acts as a thrust bearing.  A bronze washer between this
flange and the power feed housing serves as the other half of the thrust
bearing.   The bevel gear is fastened to the new journal/thrust bearing
by two small screws that go axially through the hub of the bevel gear
and thread into the new jounal.  To set the axial clearance for the
bevel gear I made the new journal a bit long, then temporarily installed
it and measured the axial play in the bevel gear with a dial indicator.
Then I took it back apart and faced off the end of the journal to
shorten it by the measured amount of play minus about .010" (I found
that .010" axial play was about right on mine- this gives full gear
tooth engagement with enough clearance to avoid rough movement.)  The
bevel gear/journal/thrust bearing assembly is keyed to the leadscrew
shaft but free to slide axially along the shaft.  The handwheel is
tightenend onto a new shoulder in the leadscrew shaft so it never
touches the bevel gear (alternatively you could cut a groove in the
leadscrew or leadscrew extension and butt the handwheel up against a
snap ring in this groove.)

	I've been using this unit fairly heavily for a little over two years
now (heavy use for a mill/drill, at least - stuff I never expected to do
with it when I bought it.  Surprised I haven't broken any of the
castings yet ;-/).  I hate to think of all the times I've engaged the
power feed with gib locks tightened (oops...table moves anyway but
powerfeed motor makes a noise like a tortured cat.)   I took the
leadscrew assembly apart a few months ago to adjust some of the backlash
out of the leadscrew nut (worn in large part because of all those
"oopses") and the bronze bevel gear still looks nearly pristine.  I'm no
expert at reading gear tooth wear, but the only evidence of wear that I
could see was a greenish tint in the grease, which is pretty normal for
bronze gears.  Much less wear than I'd expected, given the abuse it's
taken.

Regards,
Doug Jackson

From: Doug Jackson <actionj@io.com>
Newsgroups: rec.crafts.metalworking
Subject: Re: Installing table power feed
Date: Mon, 13 Nov 2000 09:25:53 GMT

Mike Graham wrote:
> Did you drill the bushing and put in grub
> screws so it would hang onto the shaft somehow?

	I drilled the bevel gear and drilled and tapped the bushing for axial
screws to hold the bevel gear to the bushing.  Neither part is attached
to the shaft at all, besides being keyed to the shaft.

> > To set the axial clearance for the
> >bevel gear I made the new journal a bit long, then temporarily installed
> >it and measured the axial play in the bevel gear with a dial indicator.
>
>   How?  I couldn't figure out how to get in there to measure it.  I just
> kept taking out shims until the play on the big plastic gear on the bottom
> of the unit felt like it was about as snug as it was going to get.

	I don't know how yours is set up, but on mine I was able to mount the
dial indicator to the power feed housing with the indicator tip
contacting the back of the bevel gear to measure its axial play.

>   So the handwheel on the other end of the table is the only
> one that affect the 'play' of the system.

	No, actually neither handwheel affects the "play" of the bevel gear,
nor do the leadscrew thrust bearings.  As I feared, my previous
description wasn't clear enough, so I'll break out the ASCII art:

T = Table
P = Powerfeed housing
B = new Bushing/thrust bearing
L = Leadscrew
K = shaft Key
S = Screws joining bevel gear to new bushing/thrust bearing
W = bronze Washer
N = Needle roller bearing on power feed

T T T T T TP P P P P P P P P P P P P P P P P P P P P P P P P          H H H H
T T T T T TP P P P P P P P P P P P P P P P P P P P P P P P P          H H H H
T T T T T T     B B B B WW P P P P P P P P P P P P P P P P P          H H H H
T T T T T T     B B B B WW P P P P P P P      /   |                   H H H H
T T T T T T     B B B B    N N N N N         /    |                   H H H H
T T T T T T     B B B B    N N N N N        /     |                   H H H H
T T T T T T     B B B B B B B B B B B B B  /      |________           H H H H
T T T T T T     B B B B B B B B B B B B B |                |SS        H H H H
T T T T T T     B B B B B B B B B   SSSSSSSSSSSSSSSSSSSSSSSSSS        H H H H
T T T T T T     B B B B B B B B B B B B B  _K K K K K K K _|SS        H H H H
                                            K K K K K K K             H H H H
L L L L L L L L L L L L L L L L L L L L L L K K K K K K K L L L L L L H H H H
L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L
L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L L H H H H
                                           ________________           H H H H
T T T T T T     B B B B B B B B B B B B B |                |SS        H H H H
T T T T T T     B B B B B B B B B   SSSSSSSSSSSSSSSSSSSSSSSSSS        H H H H
T T T T T T     B B B B B B B B B B B B B |        ________|SS        H H H H
T T T T T T     B B B B B B B B B B B B B  \      |   ^               H H H H
T T T T T T     B B B B    N N N N N  /    \\     |   |               H H H H
T T T T T T	B B B B    N N N N N /      \\    |   |               H H H H
T T T T T T 	B B B B WW P P P P  /________\\___|   |               H H H H
T T T T T T 	B B B B WW P P P P P P P|| P P P P P P|P P P P P      H H H H
T T T T T TP P P P P P P P P P P P P P P|| P P P P P P|P P P P P      H H H H
T T T T T TP P P P P P P P P P P P P P P|| P P P P P P|P P P P P      H H H H
T T T T T TP P P P P P P P P P P P P P P|| P P P P P P|P P P P P      H H H H
                                        ^             |
                                        |             |___ bevel gear
                                        | ___ pinion

	This is the basic concept - I've left out things like leadscrew
bearings & leadscrew extension pieces since your mill is obvously
different from mine in these respects.
	The bushing/bevel gear assembly has a sliding fit around the leadscrew
and transfers torque to the leadscrew via the key, but otherwise is not
fixed to the leadscrew.  The flange and the bronze washer keep the
bushing/bevel gear assembly from moving to the right.  Nothing keeps the
assembly from moving to the left except the axial force exerted by gear
tooth contact.  This means that the handwheel nut can't exert any force
on the bevel gear or it will smash the gears together too tightly.  Thus
the hanwheel has to sit on a new shoulder in the leadscrew.
	The beauty of this is that the leadscrew can slide in an out of the
bushing/bevel gear assembly without changing the axial position of the
bevel gear.  Thus if the thrust washers connecting the leadscrew to the
table have a bit of play this will not affect proper meshing of the
bevel gear.

Hope this helps,
Doug Jackson

From: Doug Jackson <actionj@io.com>
Newsgroups: rec.crafts.metalworking
Subject: Re: Installing table power feed
Date: Mon, 13 Nov 2000 11:49:01 GMT

Mike Graham wrote:

>   So the flange on the bushing and the driven bevel gear actually 'sandwich'
> the powerfeed housing and that's what keeps it in place.  Interesting.  I'm
> not sure that my feed unit has the lip that your flange bears against.
> That's a very snazzy setup, though  looking at that diagram makes me wonder
> how you found space to fit a dial indicator in there to measure backlash.

	Since I don't need the handwheel in place to keep everything together,
I had plenty of room for the dial indicator.

	If your feed unit doesn't have a recess between the table and the
needle bearing, you might be able to make a spacer to sandwich between
the power feed housing and the table to make room for the flange.  A few
washers around the powerfeed mounting bolts would probably work,
although I'm sure you could work up something more elegant.  Of course
this would only work if the leadscrew is long enough to leave room for
the handwheel- alternatively you might be able to machine a recess in
the power feed housing.  Up to you.  This wasn't a problem on mine since
I had to extend the powerfeed out from the table about 5" in the first
place so it wouldn't hit the base casting on the mill/drill when the
table was moved all the way to the other side.