Author Topic: Bridgeport head rebuild  (Read 699 times)

Offline kvom

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Bridgeport head rebuild
« on: May 27, 2021, 10:56:15 PM »
I have been living with not having back gear for a number of years, and then when I tilted the head to try to drill at an angle the spindle wouldn't turn.  After watching several YouTube videos from H&K on teardown/rebuild/and reassembly of the upper section, I decided to send the entire head to H&K for a rebuild of the top and inspection of the lower spindle section.  Rather than struggle with the entire 200 lbs of head, I planned to disassemble the upper half following the videos, and deliver the parts myself (one day drive from home).

The first issue was removing the head from the ram.  To do this, I ordered their ram removal tool from H&K.  It's basically a fixture that bolts the table using t-nuts, and has a vertical 7/8" diameter vertical rod at the top.  A 7/8" collet is inserted into the spindle and locked to the fixture prior to bolting to the table.  With everything tightened up, the 4 nuts that secure the ram bolts are removed, and then the table is retracted.  The bolts are quite long, so I also had to retract the ram to clear them from the head.



Now I could lower the knee to the bottom and start the disassembly with the head still clamped to the table.  The removed sections are the motor and 1 set of pulleys, the pulley enclosure, the front pulley assembly, and the bull gear section. I'll leave the spindle section on the fixture until time to load the car.

One thing I noticed through experiment is that it could be difficult to reattach the head to the ram even with the tool.  That's because the 4 t-bolts that need to line up are free to rotate and wiggle, and unless lined up perfectly with their holes will jam solid.  Not having Chris' elves to station one per bolt, I decided to make an alignment fixture to hold all 4 simultaneously in position.  This fixture is a piece of cardboard with 5 holes, and is show in position with the bolts about halfway into the head.



To prepare to use it, the head is positioned on the table and moved into the ram so that the ram's helical gear enters the matching cavity on the head.  The the t-bolts are inserted and moved so that the cardboard can be inserted  over them.  With the cardboard's hole over the ram's gear, it was fairly simple to guide the bolts into the head.  Once the bolts are well in, I'll cut away the cardboard.

To make the fixture, I measured the head and produced this drawing in Solidworks.



I cut the holes into a 7" square piece of 1/8" thick cardstock on my CNC mill as follows.

With a 6" wide piece of aluminum in the vise, I put three strips of 3M painters tape on top.  These were burnished to remove any bubbles/wrinkles.



I spread some Loctite glue along both sides and a small amount in the center, then centered the cardboard and clamped.  I waited 30+ minutes for the glue to set.





Not too difficult to remove the tape from the aluminum freeing the fixture.  Nothing too pricise here other than the holes.
« Last Edit: May 27, 2021, 11:10:22 PM by kvom »

Offline Dave Otto

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Re: Bridgeport head rebuild
« Reply #1 on: May 27, 2021, 11:10:42 PM »
Looks like it's time to give her a much needed bath. :lolb:
Hope the rebuild goes well, I have been into mine a couple of times over the years.

Dave

Offline kvom

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Re: Bridgeport head rebuild
« Reply #2 on: June 05, 2021, 12:04:15 PM »
All the parts loaded into the car, and I'll be driving it to Ft. Wayne IN or Monday.  I had the option of trading it for an already rebuilt head, but decided to have mine rebuilt instead.  Doing the trade would mean needing to drill and tap three mounting holes in the pulley case for my hydraulic drawbar.  Hard to do without a mill and also requiring some disassembly.

Going to spend the rest of the week in Detroit, with a mandatory visit to the Henry Ford.

Offline kvom

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Re: Bridgeport head rebuild
« Reply #3 on: June 12, 2021, 12:07:35 PM »
I dropped the head off at H&K on Monday morning.  I had a tour of the shop that was interesting.  Lots of Bridgeports and other machines in course of repair as well as some lathes.  One BP knee was in course of having its ways reground on a giant grinder.  Nice family-run business.

They didn't make any promises, but on Tuesday night I got an email that it was ready.  I cut my Detroit stay a bit short and picked it up Thursday morning.  Now back home and needing some hired labor to get it onto the BP table.

Offline kvom

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Re: Bridgeport head rebuild
« Reply #4 on: June 14, 2021, 12:28:40 PM »
Head is back on and working.   :D

Offline Admiral_dk

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Re: Bridgeport head rebuild
« Reply #5 on: June 14, 2021, 11:00:51 PM »
Great new - bet you're feeling good about that fact  :cheers:

Offline kvom

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Re: Bridgeport head rebuild
« Reply #6 on: June 14, 2021, 11:06:32 PM »
Yes.  Now need to get shop AC back working.

Offline steamer

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Re: Bridgeport head rebuild
« Reply #7 on: June 15, 2021, 11:47:11 PM »
Yes.  Now need to get shop AC back working.

You can say that again!

Following along.....
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline Art K

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Re: Bridgeport head rebuild
« Reply #8 on: June 16, 2021, 02:52:59 AM »
Good to see you have the Bridgeport back in one piece.
Art
"The beautiful thing about learning is that no one can take it away from you" B.B. King