Re: Automatic boring head?

Hello,

First let me say that there are three peoples' answers "available" as
I post this. It seems that Yahoo is not posting new messages anywhere
near real time? Am I the only one noticing this?

Ok, to the question:

An automatic boring head (Yes, sometimes called a facing head) is one
which "Adjusts itself"(the bore diameter is changed to a larger
setting) while rotating. This is used for facing a surface (say
clearing away the area under a bolt around a bolt hole, in a rough
casting) and "undercutting operations", like putting a groove for a
retaining clip in a bore.

There are a couple of variations in how it is done. The old style
used a "star wheel" on the end of the boring head adjusting screw,
which "hit" a fixed pin mounted in an appropriate place. The pin
was/is able to move "out of the way", usually with a lever. The
machinist sets the beginning size, and puts the pin at a certain
distance from the star wheel. (Moving the pin closer or farther from
the star will adjust the feedrate, since the star will be rotated
farther if it is engaged longer.) The machinist turns this setup by
hand and measures how much movement each rotation of the boring head
(past the fixed pin) imparts to the star wheel. This is then noted as
the feed per revolution.

Now the quill is inserted into the bore to place the cutter at the
proper position for the retaining ring slot. The spindle is turned
on, and the "clicks" (starwheel hitting the pin) are counted. When
the "proper" amount of feed has been counted, the machinist moves the
pin out of the way of the starwheel with the lever action. This
obviously stops the feed. There is usually another position of the
pin which will hit the starwheel and cause it to go in the reverse
direction (some of these lever arrangements only have fwd and rev)
So when the correct feed is reached, the lever is thrown, and the
head reduces its' diameter each rotation... when it is clear of the
bore, the quill can be raised to clear the part.

Besides the starwheel type, there are some which use a hand "grab",
as Jon mentioned; and some which are fully automatic (costing
thousands). Some are between the two. They use a ratchet pawl like
Jon mentioned, but are "fed" by an arm which works sorta like the
starwheel fixed pin arrangement.

Yes, you can use these as "plain ole" boring heads...

Hope this helps.

Ballendo

P.S. As Jon said, CNC has made these obsolete for many shops. Also
the wide range of commercial cutting tools (widely available) has
changed the way machinists approach their work. An entirely different
mindset. Some of these "old ways" are pretty useful to save money,
compared to buying lots of tooling (which is the choice most
commercial shops HAVE to choose nowadays).

P.P.S. You CAN "retrofit" a starwheel and lever-pin arrangement to a
lower end boring head, and it can be pretty useful, IMO.

--- In CAD_CAM_EDM_DRO@y..., Tim Goldstein <timg@k...> wrote:
> OK, I have seen this item listed in catalogs and still don't
understand why I would want one, when it would be used, if it can
work like a standard boring head, or how I would make it work
automatically.
>
> Can anyone help reduce my ignorance?
>
> Tim
> [Denver, CO]