Hoffman Mechatronics
Bridgeport Mill J1 Rebuild
Secure the J-Head to the lift being used, so that as the nuts that hold the J-Head onto the turret
are loosened the J-Head does not fall or pivot. The J-Head is held to the Ram Adapter with four
½” bolts and nuts that ride in a T-Track on the Ram Adapter. These bolts can be either square
head, or hex head depending on the year of your mill. Once you have removed the four nuts from
the face of the J-Head, it may be slid away from the Ram Adapter face. Some people who have
not been able to acquire a lift for the J-Head, will remove the motor and drive portions to lighten
the load, and then get a friend to help lift the J-Head off. You can also use the table to assist by
raising it up until it supports the nose of the quill.
Just be safe, that’s all I ask.
4.1.2 J-Head Reassembly
I reassembled the J-Head onto my machine by supporting it with an Engine Hoist, and sliding it
over the bolts that I had slid into the T-Tracks on the Ram Adaptor. Once the unit is up against
the Ram Adaptor, and the tilt gears are engaged, you can put the nuts on and tighten them up.
4.2 Quill Pinion Shaft RIR
The Quill Pinion Shaft provides the drive mechanism for raising and lowering the Quill both
from gross manual movement which uses the Quill Feed Handle, to the micro adjustments
available through the use of the hand wheel assembly, to automated using the Quill Feeds.
4.2.1 Quill Pinion Shaft Removal
To remove the Quill Pinion Shaft you will have to first remove the Pinion Shaft Hub Handle then
remove the Pinion Shaft Hub by pulling it straight off the shaft. You will then have to remove
the clockwork spring. Be careful when removing the screws securing the clockwork spring as the
spring is under tension and the housing will want to rotate. I have included plans for a small tool
that can be used to control the twisting of the clockwork spring in Appendix A. Please use this
tool or something similar to release the spring tension in a controlled manner. Next you will need
to remove the quill feed clutch cover, and extract the overload clutch.
I have not included any procedures for adjusting the overload clutch simply because unless
something is broken in your clutch assembly, it rarely needs adjusting and the Bridgeport manual
states that it should be done by an authorized Bridgeport Repair Facility.
BPJ1RBLD_002
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January 31, 201111