For example, can I swap a step pulleyed head, for a variable speed
head? Are the mounting arrangements the same?

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In general, yes. There's a company near me (western Wisconsin) that
rebuilds and sells Bridgeports all the time. They never ship a J-head
out, they always update it to a variable speed drive.

I don't think this applies to the M-head though.

FWIW, the last time I was there in person (a couple of years ago)
they had a whole pallet full of those J-heads. Maybe they part 'em out
when they repair machines for others.

Pete Stanaitis
--------------------

Ignoramus18195 wrote:
For example, can I swap a step pulleyed head, for a variable speed
head? Are the mounting arrangements the same?

"spaco" wrote in message
.. .
In general, yes. There's a company near me (western Wisconsin) that
rebuilds and sells Bridgeports all the time. They never ship a J-head
out, they always update it to a variable speed drive.

I don't think this applies to the M-head though.

FWIW, the last time I was there in person (a couple of years ago) they
had a whole pallet full of those J-heads. Maybe they part 'em out when
they repair machines for others.

Pete Stanaitis
--------------------

Ignoramus18195 wrote:
For example, can I swap a step pulleyed head, for a variable speed
head? Are the mounting arrangements the same?


An "M" head will need an adapter.

Ignoramus18195 wrote:
For example, can I swap a step pulleyed head, for a variable speed
head? Are the mounting arrangements the same?

1J (step pulley) and 2J (varispeed) are interchangeable, in fact the
main casting is identical. The ancient M head is NOT the same, however,
a much smaller bolt circle. As long as it is a V-ram or rigid ram
machine, it would be unlikely to have an M head. The 1J has 4 belt
speeds and a geared low range, with a toothed reduction belt below the
vee belt. It also has power down-feed with a 3-speed selector. The M
head has 6 speeds, no back gear and no power quill feed.

One other thing, various J heads have different spindle tapers, mostly
your choice of R-8, NMTB 30 or a couple quick-switch systems.

There are the 3J and 4J heads on Series-II machines, definitely NOT
interchangeable with 1- and 2J. (Note, Series-II tracers and
multi-spindle machines often had several 2J heads on them.)

There are also BOSS heads which have a coaxial ballscrew machined into
the quill. These are CNC-only, no provision for normal manual quill feed.

Jon