Newsgroups: rec.crafts.metalworking
Subject: Re: jig borrer
From: jmorton@euler.Berkeley.EDU (John Morton)
Date: 20 Sep 1994 19:26:00 GMT

In article <35mvve$gp4@andromeda.rutgers.edu>,
Charles Rowe <clrowe@andromeda.rutgers.edu> wrote:
>  Can anyone explain the difference between a jig borer and
>a small vertical mill ( differences in construction , function,
>and use in the small shop)?
>Thanks   
>          Charlie     clrowe@andromeda.rutgers.edu 

I have not put much time in on jig borers, because in a general
shop they are always reserved for very precise jobs.  Of course 
they can be used as mills or drill presses, but then after awhile 
they will be no good as jig borers :-).

The traditional jig borer provides a table with movement in two
axes.  The Z axis I think is usually represented by a slide
carrying the spindle head.  The system for locating the table
is what is distinctive:  there are gutters which run between
micrometer anvils, one on the table, one on the machine frame.
Precise standard-length bars are cleaned and laid end to end
in the gutters of the X and Y axes until they are within the
range of the micrometer screws.  Their lengths are totaled to
obtain absolute locations.

I forget the details (it has been 10 yrs. since I was in a shop
that had one), but suffice to say that jig borers are designed
for extreme accuracy.  Therefore they are always heavier,
slower and more limited in their capacities than milling machines.

Obviously what I remember is an outmoded version, but it probably
still holds true that jig borers are uneconomic as mills.  I
think the new ones use laser locating systems.

Can somebody supply some info from experience?


John Morton					University of California
jmorton@euler.berkeley.edu			Mechanical Engineering
{decvax,cbosgd}!ucbvax!euler!jmorton		Machine Shop