Re: "soft jaw boring ring"
- From: BottleBob <bottlbob@xxxxxxxxxxxxx>
- Date: Fri, 25 Nov 2005 05:39:58 GMT
> Does anyone here have a drawing of a soft jaw boring ring - to fit 10"
> lathe chucks ( or any other size chuck) Or a website on how to make
> one. I know I can buy one. But with a fully equipped workshop, I want
> to make three (15",10" & 8") for my CNC's. Similar to these
> Any help would be appreciated.
I don't have a drawing, but I made three boring rings some years ago.
Here's a copy of a post I made that mentions the boring rings.
Mar 12 1999, 12:00 am
From: Bottlebob <bottl...@xxxxxxxxxxxxx> - Find messages by this author
Subject: Re: Set-up and Machining tips.
I know this may not be directly CNC related but it falls under
heading of machining and I don't know about anybody else, but I do some
manual work when work for the CNC mills is slow. That's the nature of
job shops. :)
Boring soft jaws in a manual machine. The first thing you have
remember when boring or using soft jaws is to always tighten the chuck
using the SAME chuck key location even if there is more than one
location. Mark it with dykem if you have to. The scroll that moves the
jaws doesn't repeat to .001 when using different locations (at least
Next decision is how you're going to keep the jaws stable while
boring. They make those three lobed sheet metal cam plates that you
tighten the chuck jaw down on that are 1/8- 3/16 thick, and they work Ok
but if you've had them come loose while boring you might want to look to
another idea. I sometimes use some different size big nuts that I've
drilled and tapped 1/4-20 holes in 3 of the flats. Then I can screw in
the appropriate length allen bolts and adjust the bolts to a length for
a reasonable starting point for boring the jaws. I call them "spiders",
I don't know if that's the standard name for these things or even if
they are commercially sold. To easily insert the "spider" in the chuck
you can use a long bolt that screws a couple of threads into the center
of the "spider" and when it's in place and the chuck is tightened down
on it you just unscrew the bolt.
Boring rings. I saw these devices at the last Westec show
probably been making them for years but I just noticed them last year)
that are large (8-12 inch) disks that have three curved increasing
radius slots that three movable bosses slide along and are individually
tightenable. The bosses fit in the screw counterbores of the soft jaws
and you open the chuck until you get the jaw opening you like and insert
the bosses in the counterbores and then you tighten the bosses down and
then tighten the chuck putting pressure on the bosses. There is a large
hole in the center to bore through, you need more than one size to cover
standard 10-12 inch chucks. I CNC'd about three of these things from a
picture in a catalog (I hope nobody arrests me for patent
The next thing to be concerned with is measuring the bored soft
diameter. When the bored holes are small enough there is no problem,
you can caliper it or use a telescoping gage to get the diameter. If
the jaws are separated by enough distance then a telescoping gage
doesn't work. I sometimes just put a 1/2 inch dowel pin in the
tailstock drill chuck, run it between the bored jaws and caliper the
distance between the dowel pin and bored surface of the jaws and add 1/2
the dowel pin diameter and double the figure to get the diameter. This
is actually more difficult than it sounds to get accurate, fiddling with
the caliper, so I made what I call my "Triceratops". It has three 4
inch diameter gears and a small 1" diameter gear in the center. I CNC's
a three lobed piece that holds the center gear in the center and the
three other gears separated by 120 degrees in mesh with the center
gear. The center gear has a shaft going through the bearing and the
lobed mounting plate to a knurled knob. Then I bored three 1/4" dowel
pin holes in the three large gears near the outer rim and inserted dowel
pins in them that stick out about an inch. The center gear also has a
..250 pin sticking out an inch. Now when the knob on the back is turned
the all four gears rotate and the dowel pins can move from a fully
closed 2 inch dimension to a fully extended 8 inch dimension (I don't
know the exact dimensions since the device isn't in front of me but you
should get the idea). The Triceratops is used kind of like a
telescoping gage where you put it up to your bored soft jaws and turn
the knob until the three dowel pins contact the bored surfaces of the
jaws. You remove the device and measure across the center pin and one
of the outer pins, subtract 1/2 the diameter of the center pin and then
double the resulting figure to get your diameter. I've never seen or
heard anything remotely like this device in any book or catalog. I
thought about marketing them but this thing would not be cheap to make.
I must have 40 hours into making just this one.
I ALWAYS underestimate how involved typing an explanation of
is going to be. I just hope my explanations got my points across. :)
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