Bridgeport J-Head Series User manual

Bridgeport J-Head Series I Mill Rebuild
Document Number: BPJ1RBLD_002
Document Version: 2.0.01
Document Version Date: January 31, 2011
Prepared By: Hoffman Mechatronics
496 Albrough Blvd.
Colonial Beach, Va 22443
[e-mail]

Hoffman Mechatronics Bridgeport Mill J1 Rebuild
Table of Contents
1.0 Document Information .....................................................................................................6
1.1 Disclaimer..........................................................................................................................................6
1.2 Notes from the Author........................................................................................................................6
1.3 Copyright............................................................................................................................................6
1.4 Document Organization.....................................................................................................................7
1.5 Change History..................................................................................................................................7
1.6 Dedications and Acknowledgements.................................................................................................7
2.0 Mill Overview.....................................................................................................................8
2.1 Mill Description ..................................................................................................................................8
2.2 Repair Estimates ...............................................................................................................................8
2.3 Why would I do this?..........................................................................................................................9
2.4 Isn’t it too old?....................................................................................................................................9
2.5 Disassembly/Reassembly Suggestions...........................................................................................10
3.0 Motor and Drive Section ................................................................................................12
3.1 Motor Removal, Inspection, & Reassembly (RIR)...........................................................................12
3.1.1 Motor Removal..........................................................................................................................12
3.1.2 Motor Inspection........................................................................................................................12
3.1.3 Motor Reassembly ....................................................................................................................13
3.2 Motor Replacement .........................................................................................................................13
3.3 Drive Housing Section.....................................................................................................................14
3.3.1 Drive Housing Removal ............................................................................................................14
3.3.2 Drive Housing Inspection..........................................................................................................16
3.3.3 Drive Housing Reassembly.......................................................................................................17
4.0 J-Head Section................................................................................................................18
4.1 J-Head R & R...................................................................................................................................19
4.1.1 J-Head Removal........................................................................................................................19
4.1.2 J-Head Reassembly..................................................................................................................20
4.2 Quill Pinion Shaft RIR......................................................................................................................20
4.2.1 Quill Pinion Shaft Removal .......................................................................................................20
4.2.2 Quill Pinion Shaft Inspection.....................................................................................................21
4.2.3 Quill Pinion Shaft Reassembly..................................................................................................22
4.3 Quill Stop and Quill Indicator RIR....................................................................................................22
4.3.1 Quill Stop and Quill Indicator Removal.....................................................................................22
4.3.2 Quill Stop Inspection.................................................................................................................23
4.3.3 Quill Stop Reassembly..............................................................................................................23
4.4 Quill and Spindle Removal ..............................................................................................................23
4.4.1 Quill and Spindle Inspection......................................................................................................24
4.4.2 Spindle Bearing Reassembly/Replacement..............................................................................25
4.5 On Machine Spindle Extraction .......................................................................................................28
4.6 Feed Driving Gear Assembly RIR ...................................................................................................28
4.6.1 Feed Driving Gear Assembly Removal.....................................................................................29
4.6.2 Feed Driving Gear Assembly Inspection...................................................................................30
4.6.3 Feed Driving Gear Assembly Reassembly...............................................................................30
4.7 Feed Reverse Gear Assembly RIR.................................................................................................30
4.7.1 Feed Reverse Gear Assembly Removal...................................................................................30
5.0 Turret Section .................................................................................................................31
5.1 Ram Adapter RIR ............................................................................................................................32
5.1.1 Ram Adapter Removal..............................................................................................................32
5.1.2 Ram Adapter Inspection............................................................................................................32
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5.1.3 Ram Adaptor Reassembly........................................................................................................32
5.2 Ram RIR..........................................................................................................................................33
5.2.1 Ram Removal............................................................................................................................33
5.2.2 Ram Inspection .........................................................................................................................33
5.2.3 Ram Reassembly......................................................................................................................34
5.3 Turret RIR........................................................................................................................................35
5.3.1 Turret Removal..........................................................................................................................35
5.3.2 Turret Inspection .......................................................................................................................36
5.3.3 Turret Reassembly....................................................................................................................36
6.0 Table Section ..................................................................................................................38
6.1 Lead Screw Bearings & Brackets RIR.............................................................................................38
6.1.1 Lead Screw Bearings & Brackets Removal..............................................................................38
6.1.2 Lead Screw Bearings & Brackets Inspection............................................................................39
6.1.3 Lead Screw Bearings & Brackets Reassembly.........................................................................39
6.2 Table X&Y-Axis Gib RIR..................................................................................................................40
6.2.1 Table X&Y-Axis Gib Removal...................................................................................................41
6.2.2 Table X&Y-Axis Gib Inspection.................................................................................................41
6.2.3 Table X&Y-Axis Gib Reassembly..............................................................................................42
6.3 Table RIR.........................................................................................................................................42
6.3.1 Table Removal..........................................................................................................................42
6.3.2 Table Inspection........................................................................................................................43
6.3.3 Table Reassembly ....................................................................................................................44
7.0 Saddle Section................................................................................................................45
7.1 Saddle Section Removal .................................................................................................................45
7.2 Saddle Section Inspection...............................................................................................................46
7.3 Saddle Section Reassembly............................................................................................................47
8.0 Knee Section...................................................................................................................48
8.1 Knee Section Removal....................................................................................................................48
8.2 Knee Section Inspection..................................................................................................................50
8.3 Knee Section Reassembly...............................................................................................................51
9.0 Tramming the Mill...........................................................................................................52
9.1 Bridgeport Method...........................................................................................................................52
9.2 Bearing Race Method......................................................................................................................53
9.3 Tramming to the Vice.......................................................................................................................53
10.0 Maintenance & Lubricants.............................................................................................54
10.1 Backlash Adjustment.......................................................................................................................54
10.2 Feed Trip Adjustment ......................................................................................................................55
10.3 Spindle Lubricant.............................................................................................................................55
10.4 Way Lubricant..................................................................................................................................56
11.0 Troubleshooting .............................................................................................................57
11.1 Quill does not go more than 3-4 inches down.................................................................................57
11.2 Quill feed does not disengage when the quill stop is hit..................................................................57
11.3 I try to install a gib and it stops short. It feels like it is hitting something.........................................57
11.4 My quill keeps falling down, I have to lock the quill in place for it to stay up...................................57
12.0 CNC Conversion.............................................................................................................57
12.1 Why would you convert to CNC?.....................................................................................................57
12.2 Where do you start? ........................................................................................................................58
12.3 Phase 1 – The Ball Screws..............................................................................................................58
12.4 Phase 2 – The Electronics...............................................................................................................59
12.4.1 Open Loop System ...................................................................................................................59
12.4.2 Closed Loop System.................................................................................................................61
12.5 Phase 3 – The X and Y Axes ..........................................................................................................61
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12.6 Phase 4 – The Z Axis ......................................................................................................................63
12.7 Phase 5 – The Planetary Gearhead for Z Axis................................................................................64
12.8 Software packages..........................................................................................................................65
12.9 The Moral of the Story.....................................................................................................................65
13.0 Reference Documents and Websites............................................................................67
13.1 Documents.......................................................................................................................................67
13.2 Websites..........................................................................................................................................67
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Table of Figures
Figure 1 - Mill ID Plate................................................................................................................................8
Figure 2 - J Head Figure 3 - Table and Knee ......................................................................................9
Figure 4 - Grub Screws, note the hollow locking screw...........................................................................11
Figure 5 - Motor Nuts................................................................................................................................12
Figure 6 - Drive Housing Assembly..........................................................................................................14
Figure 7 - Power Head Mounting .............................................................................................................15
Figure 8 - Drive Housing Timing Belt .......................................................................................................15
Figure 9 - Bolts Fastening Drive Housing Together.................................................................................16
Figure 10 - Drive Housing Inspection.......................................................................................................16
Figure 11 - Gear Housing Cover..............................................................................................................17
Figure 12 - J-Head....................................................................................................................................18
Figure 13 - J-Head Mounting....................................................................................................................19
Figure 14 - Overload Lever Plunger and Spring ......................................................................................21
Figure 15 - Overload Clutch Ring and Circlip...........................................................................................21
Figure 16 - Ball Reverse Lever, and Quill Stop Trip Lever.......................................................................22
Figure 17 - Homemade Spanner Nut Wrench..........................................................................................24
Figure 18 - Note the Axial Alignment Asterisk and the Bearing Orientation ............................................25
Figure 19 - Note the alignment marks on outer races preparing for next step.........................................26
Figure 20 - Aligning with Nosepiece Screw Hole .....................................................................................27
Figure 21 – Homemade Spanner Nut Wrench.........................................................................................27
Figure 22 - Worm Gear Cradle Assembly................................................................................................29
Figure 23 - Feed Driving Gear Assembly.................................................................................................29
Figure 24 - Reverse Feed Gear Assembly...............................................................................................30
Figure 25 - Reverse Feed Gear Removal................................................................................................31
Figure 26 - Ram Adapter..........................................................................................................................32
Figure 27 - Ram Assembly.......................................................................................................................33
Figure 28 - Turret Base and Ram Lock....................................................................................................33
Figure 29 - Ram Installation .....................................................................................................................34
Figure 30 - Ram Sliding Fixture................................................................................................................35
Figure 31 - Turret Bolts and Cross Member.............................................................................................36
Figure 32 - Turret Reassembly.................................................................................................................36
Figure 33 - Turret Cross Member.............................................................................................................37
Figure 34 - Table Handle, Dial and Nut....................................................................................................38
Figure 35 - Broken Bracket.......................................................................................................................39
Figure 36 - Bearing Bracket with Bearings Installed................................................................................40
Figure 37 - Gib Adjusting Screw...............................................................................................................40
Figure 38 - Gib Parallels...........................................................................................................................40
Figure 39 - Y-Axis Chip Wiper Cover.......................................................................................................41
Figure 40 - Y-Axis Gib and Adjusting Screw............................................................................................41
Figure 41 - Table Nearly Ready for Removal...........................................................................................43
Figure 43- Saddle.....................................................................................................................................45
Figure 44- Lead Screw Nut.......................................................................................................................45
Figure 45- Lead Screw Nut Bracket .........................................................................................................46
Figure 46- Knee Gib Area.........................................................................................................................48
Figure 47– Removing/Reinstalling the Knee............................................................................................49
Figure 48 - After the Crank and Dial have been Removed......................................................................49
Figure 49 - Knee Elevating Bevel Gears..................................................................................................50
Figure 50 - Elevating Screw Bearing Retainer Ring.................................................................................50
Figure 53 - Feed Nut Bracket...................................................................................................................54
Figure 54 - Feed Trip Lever......................................................................................................................55
Figure 55 - Spindle and Back Gear Lube Cups........................................................................................55
Figure 56 - Way Lube Fittings ..................................................................................................................56
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Figure 57 - Knee Lube Fittings.................................................................................................................56
Figure 58 – CNC Electronics....................................................................................................................60
Figure 59 – X Axis Drive Tube .................................................................................................................62
Figure 60 – Y Axis Drive Tube .................................................................................................................62
Figure 62 – Z Axis Installation..................................................................................................................64
Figure 63 – Z Axis Planetary Gearbox Installation...................................................................................65
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1.0 Document Information
1.1 Disclaimer
Milling machines are industrial pieces of equipment meant to be operated by trained personnel.
The maintenance and rebuild procedures for these machines are also meant to be carried out by
trained personnel. This manual is provided merely to provide information to authorized persons,
and the author assumes no liability for any damage or injury from the information and
procedures that are documented within. These machines are heavy, powerful, and dangerous to
those not trained in their operation or maintenance. I want to emphasize that you should exercise
EXTREME CAUTION when working on or with these machines to minimize or eliminate the
possibility of personal injury.
1.2 Notes from the Author
This document was created during the rebuild of my personal 1963 Bridgeport Series I J-Head,
Stepped Pulley Mill. Much of the information presented in this document is from my own
personal experiences, and all of the images that are located throughout the document were taken
by me using a Nikon Coolpix 4300 and a Nikon D70s. For those images where I have included
drawings, they were created using either TurboCADCAM or SolidWorks.
So why would I take the time to try and document this? First of all, because I could not find the
information I needed to complete this rebuild and I thought that others may want some of the
same information. Secondly, I wanted to give something back to the home machining
community that has provided so much useful information to me. Where possible I have included
acknowledgements/references for the assistance I have received. If I have missed anyone, please
feel free to let me know. I certainly could not have compiled and reviewed all of this information
by myself, nor do I want people to think that I have. There are many trained personnel out there
willing to devote their time and machines and I want to make sure that have I given everyone
their fair share of credit.
Where possible I have taken pictures of every phase of the assembly and tuning of this wonderful
machine. Most of the information I have is from doing, not from being taught, so if you find
something in error, I beg of you … please let me know. This document can only improve if
people like you are willing to say “Mike is full of crap, I better let him know!”
What is the benefit for telling me that I am full of crap? Well, not only the personal pleasure of
doing so, but I will place your name in the acknowledgements section, and send you a revised
copy of the manual.
1.3 Copyright
Hoffman Mechatronics (a.k.a. Mike Hoffman) maintains the copyright to this document. If this
document is sold without my permission, then that is a violation of my copyright. I have decided
to release this document into the public domain, which means if you paid for it, you have been
ripped off, and someone else is profiting from my work.
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1.4 Document Organization
You will quickly note that I have tried to organize this document to the corresponding parts of
the Bridgeport Mill. I believe it will make this document easier to follow should someone be
trying to solve a specific problem. It also tends to follow the order of disassembly if someone is
starting to completely disassemble their mill for the first time. One of the last sections of the
document deals with troubleshooting. Although this portion is rather small now, I am hoping that
I can add to this as more and more people provide questions, and solutions to common and not so
common problems.
NOTES: are included in the document where I think something bears bringing attention to.
CAUTIONS: are highlighted where someone may be injured if proper safety precautions are not
taken.
1.5 Change History
Revision Date Changed By Change Description
Draft 8/29/2005 M. Hoffman Initial draft
Draft 0.01 10/15/2005 M. Hoffman More images, callouts, and tense corrections.
1.0.00 8/22/2006 M. Hoffman More images, more text, and review of all figures
1.6 Dedications and Acknowledgements
First and foremost I want to dedicate this manual to my wife who has put up with my insane
hobbies and business ideas for some 21 years. She is the one who carries me to the hospital when
I do stupid things, and then cares for me at home until I am once again able to do more stupid
things.
Secondly I want to thank my brother for showing me this amazing machine, and putting the idea
in my head that I could rebuild it and make it new again.
I also wanted to send out a special thanks to the Chesapeake Area Metalworking Society
(CAMS). From the very beginning they have supported my efforts and offered to help with
everything. Sorry guys, I won’t be bringing the finished mill in for “Show n Tell”, but I will
bring pictures!
The following people have helped me considerably along the way, and this document would be
so much less without their inspiration and guidance.
Kirk Burns & Machinist Preston (Burns Machine Shop, King George, Va)
Gary Gelts (Hardinge/Bridgeport)
Jonathan Gavel (CAMS)
Eric Hoffmeyer (CAMS)
Leigh Basset (CAMS)

Hoffman Mechatronics Bridgeport Mill J1 Rebuild
2.0 Mill Overview
I decided to write this section to provide you with an idea of the condition of the mill as I was
evaluating it for purchase and refurbishment. I also wanted to provide a description of the
amount of work that went into the mill to make it operational again.
2.1 Mill Description
The mill that I am rebuilding throughout this document is a 1963 Bridgeport Series I J-Head
Mill. The mill was identified by a brass plate in Figure 1 below that was installed by the US
Navy. This plate identifies this mill as Model# J60526, Serial# BR69063. If you don’t have the
nice Navy placard on your mill you can also find the model number of the older mills on the
door to the pedestal, the face of the J-Head, and on the knee.
Figure 1 - Mill ID Plate
This mill came equipped with a 9” x 36” Table, 9” knee and a Geared Power Feed unit. I paid
$300 for the machine after it was purchased from a Government Surplus by my brother for $400.
That’s right; my brother gave it to me for less than his cost. Yes, I have a great brother!!!
2.2 Repair Estimates
After my initial look at the mill I estimated that it would cost about $1000 to get the mill
operational again, and based on the articles I have read in the forums I estimated that it would be
another $1200 to $1300 to convert this machine to Computer Numeric Controlled (CNC).
What follows is a quick summary of the visible items that helped me to make this estimation: the
spindle bearings were stuck, the table was stuck, the knee was stuck, the turret in/out axis was
stuck, and the entire machine was covered in rust and metal shavings. The spindle bearing felt
protector was missing and metal shavings were covering the upper spindle bearing. From this I
assumed that the bearings were not merely just stuck, but would be unsalvageable. Some of the
components from the J-Head had already been removed and put in boxes, and many items looked
as though they were broken and/or bent from the mill being dropped or mishandled. There were
also a great many parts that were not damaged at all, just stuck because of years of dried up
grease, or the friction from surface rust. Based on the age of the machine and the condition of the
spindle bearings, I decided all bearings would most likely need to be replaced. As you can see
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from Figures 2 and 3 below it barely looked like a mill at all. You can see in the figures that the
Y-Axis handle is bent, the Reverse Feed Knob has been sheered off, and many of the 1” Balls
that were on the selector shafts have been sheared off as well.
Figure 2 - J Head Figure 3 - Table and Knee
2.3 Why would I do this?
So why would I tackle such a huge undertaking? There are several reasons, but the most
compelling reason for me was that I needed a mill, and why should I buy a mill that is advertised
as a Bridgeport Clone, when I could have a Bridgeport? My decision to rebuild this mill was
quickly justified after a 5pm telephone call one evening from a technician at Hardinge Tools.
I had called Hardinge Tools to see if I might get more information about disassembling part of
the mill. I was working to disassemble the J-Head and ran into a stumbling block removing the
reverse feed gear assembly. Since I did not want to break any additional parts, I called Hardinge,
fully expecting them to brush me off because I am a home user with a 42 year old machine. I left
a voicemail message and went about trying to find the information I needed elsewhere. Imagine
my surprise when I received a phone call from Gary Gelts, a Hardinge Bridgeport Service
Technician, on his way to a trouble call. He said he had heard my voicemail and wanted to help
me out. After we had talked for a couple minutes, he pulled off the road, extracted his manuals,
and talked me through the procedure of removing the reverse feed gear assembly. After
removing the assembly and thanking Gary for his time, I sat there thinking about the entire
phone call, the level of professionalism, the enthusiasm, and the willingness to help someone
without the least expectation of payment. Yes, a Bridgeport was definitely the way to go.
2.4 Isn’t it too old?
Not really. As you can expect, many of the older machines were designed to very strict
tolerances for accuracy, ease of maintenance, and durability. The machines were so popular and
so durable that many of them are still in operation today, and more and more of these mills are
finding their way into the home market. They are showing up on Online Auctions and
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