email: tony@lathes.co.uk
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Bridgeport Milling Machines
Handbooks, Parts Lists and Spares are available for most Bridgeport machines


Original Bridgeport Round-ram Model

Accessories   

Bridgeport at Work

Tree, Halco and Kerney & Trecker (Dalrae) Vertical Attachments

Table Power-feed Units   

Bridgeport Serial Numbers

Bridgeport Horizontal Stub Miller

Further Bridgeport Company History and "Building a Bridgeport"

Although in the UK one often finds ordinary horizontal and horizontal/vertical millers badged as being by Bridgeport, these were actually made by Adcock and Shipley, a Leicester-based company owned at one time by Bridgeport and responsible for producing copies of the "real American Bridgeport turret miller" (the Serial number on these models should be on a plate inside the column door - the last 4 digits being the date of manufacture).  Although the Bridgeport factory on the corner of Lindley Street and Capitol Avenue, Bridgeport, Connecticut, was demolished in 2010, spares are still available and will continue to be so for the foreseeable future.
Today the original form of the Bridgeport is, to distinguish it from later computer-controlled and larger models, referred to as the "Series 1". It was first manufactured in 1938, by two immigrant Swedish engineers Magnus Wahlstrom, a toolmaker, and Rudolf F. Bannow (died 1962) a pattern maker and radio ham. The two men had first met in 1928, when Wahlstrom had called to buy wooden loudspeaker parts from Bannow, then president of the "Bridgeport Pattern and Model Works". By 1929 they were in business together and attempting to develop an electrically-powered hedge clipper; however, when this idea was abandoned they began work on a vertical-milling attachment designed to fasten to almost any of the hundreds of thousands of plain horizontal millers then in use. The accessory, which become known as the "
Master Milling Attachment", was originally designated by the partners as their "Model C". Smartly presented, with a polished aluminium housing, it was well engineered and equipped with a heat-treated and ground spindle running in four precision, pre-loaded bearings (with those at the pulley end allowed to "float" to accommodate expansion and contraction of the spindle) and with a quill that accepted (as standard) 3-inch long B-3 collets. The head was powered by a 1/4 hp motor that gave, in conjunction with 6-step aluminium pulleys, speeds of 465, 675, 1000, 1500, 2140 and 4250 rpm. The first production example was delivered in 1932 to the Atlas Tool Company of Bridgeport and the head continued in production long enough to become known as the "Model M" when eventually fitted, some years later, to the first Bridgeport milling machine. The partners, however, were not alone in the conversion market and by the 1940s many similar attachments were available, the best-known of which were the "Tree" from Racine; the Marvin from Michigan; the "Halco" from Detroit and Kearney & Trecker with their Dalrae-manufactured "Midgetmill" and "Speedmill" units.
One special version of the Bridgeport Model C was made for use on precision Hardinge horizontal millers (early versions were badged Cataract MD5) and these heads can be recognised by a Serial numbers beginning with the letter "H". Although identical (at a glance) to the standard Model C they were not as long and used a shorter "2VB" Collet closer. From the centre of the mounting holes to the bottom of the 2VB collet closer was 5
3/16" whilst the same dimension on the B-3 collet closer model was 611/16". 
By 1936 the original head been improved by the addition of a 1/2 hp motor, the inclusion of a sliding quill with 3.5" of travel - which of course radically improved the unit's drilling and boring performance - a choice of either a No. 2 Morse or a No. 7 Brown & Sharpe taper and an improved speed range that ran through 275, 425, 700, 1050, 2100 and 4250 rpm. With this much more useful specification business began to pick up and, by 1938, with sales of 500 units per annum, and seeking further expansion, the partners decided to incorporated the head in a completely new design of highly-versatile milling machine that they would produce themselves - the Bridgeport. Apocryphal, no doubt (but with the ring of truth) the initial sketches were said to have been drawn by Rudy Bannow on a paper bag whilst waiting to unload patterns at a customer's works. In 1938 the Company changed its name to "
Bridgeport Machine Inc." and in August of that year the first Bridgeport turret milling machine was completed and shipped to the plant of the Precision Die Casting Company of Syracuse, New York - this first example, invoiced at $995, was later recovered by Bridgeport and donated to the Henry Ford Museum at Dearborn, Michigan. Today it can be found at the Precision Museum in Windsor, Vermont, U.S.A.
Because the Bridgeport was extremely well thought out its versatility was quickly appreciated in both toolrooms and production plants; not only did the whole upper turret pivot on the main column, but the round horizontal ram (driven by a rack and pinion on some but not all versions) could be moved forwards and backwards over a distance of 12 inches; once that setting had been achieved the whole assembly could then, if needed, be swung left and right and the head tilted over under the control of a large worm-and-wheel gear - the latter arrangement ensuring alterations could be made quickly and with great precision. The value of this latter feature can only be truly appreciated if you have ever have struggled to hold 75 lbs of cast iron in one hand - over at an angle in perfect alignment with an engraved mark - whilst simultaneously trying to tighten a miserably-small nut buried in some dark and oily recess hidden away at the back of the machine. Probably due to difficulties with rigidity, not all models had a clevis on the vertical-head end of the ram, later types being fitted with a more robust flat end but retaining a clevis at the other end to mount a slotting attachment. These early models had a 5-inch diameter round horizontal ram, distinctly different to the "square" type that was available from September 15th, 1952; this later ram assembly, and its mounting, could be used on earlier machines and was advertised for a time by the factory as a conversion unit. The new design had so improved the rigidity of the ram that it allowed the reintroduction of a clevis end for the vertical head (like that the competing Cross miller) and so, once again, it could be "nodded" backwards and forwards through an angle of 45 degrees each side of vertical. As an interesting aside some early (round-ram) machines have been found with a Type C head having a much-improved quill travel of 5 inches,  rather than the usual 3.5.
Continued below:

The classic Bridgeport Series 1- a 1966 "Model 9BRJ" and "Model 12BRJ" - so called because they were fitted with a table either 9 or 12 inches wide and a 1-H.P Model J Head (the Series 1 was listed for the UK market with tables lengths of 32, 36, 42 and 48 inches with, respectively, 20, 24, 30, and 36 inches of longitudinal travel; all the tables were 9 inches wide and had 9 inches of cross travel on the 9BRM, and 12 inches on the 12BRM - the only difference between the two Models.)
A detailed Manual and Parts List can be ordered here

Continued:
Another vital ingredient in the machine's success was the location of the motor to one side of the spindle, with drive by a V-belt; this meant that both the fine and drilling feeds of the quill could operate along the axis of the tool, no matter what its angle - and in a series of machining and drilling operations, which required different combinations of quick-action and fine feed movements of the quill, all could be carried out without having to reset the head. A further advantage of the side-drive motor was that the quill was left clear for a draw bar to pass through and retain cutters or their holders - some millers of this type, while having the same quill-feed arrangements, employed a motor fastened to (and so blanking off) the top of the spindle housing - so forcing the employment of awkward-to-use screwed retaining rings on their noses (a further consequence often being the need to use expensive custom or at least non-standard or modified cutter holders). Details of the various milling, drilling and boring heads can be found here.
On March 18th, 1954 the 20,000th machine left the Bridgeport factory (a building newly-erected two years earlier) bound for the Pioneer Electric Research Corporation of Forest Park, Illinois. Despite one machine being produced every 45 minutes, such was the demand for machine tools in the early 1950s that a sixteen-month backlog of orders, totalling over 3,600 machines, was not an unusual position for Bridgeport to be in. Advertising expenses for 1953 of less than $12,000 point to how the millers virtually sold themselves - and it was not uncommon in such an active market for "little-used" examples to fetch three times the manufacturer's list price.
Although for many years Bridgeport produced only the "Series 1" (though a simple horizontal miller was produced for in-house use) it was eventually converted into many special-purpose examples, both by the factory and third parties: machines with 2D and 3D hydraulic copying in both manual and automatic versions; T-shaped heads to allow a single head to be moved sideways, or up to three heads to be mounted side by side; automatic copying and precision tracing machines and, by the early 1960s, the Moog Hydra-point three-axis, numerically-controlled miller that was manufactured in England by Moog Hydra-point Ltd. on a machine made by the Bridgeport subsidiary, Adcock & Shipley Ltd. of Leicester - who had first built the Series 1 model under licence in 1959 (the initial model having a 42" x 9" table). Some versions were adapted for CNC control and the very first Bridgeport CNC miller owed much to the design of the Series 1.
By 1963 more than 60,000 examples had been manufactured, with plants in Bridgeport Connecticut, USA, Leicester and Bridlington in England - and Singapore. It was also a widely copied machine, with dozens of companies in Taiwan - and even fourteen in Spain at one time - turning out examples of greatly varying quality and performance. Today Bridgeport makes not just millers but turning and grinding machines as well, a sale being made to Rolls Royce in 2006 of a large and complex grinding machine on which to finish jet-engine parts.
As the years went by demand for the machine changed and costs came under increasing scrutiny; under various ownerships production was shifted around the globe and when owned for a time, by Textron, the machines for the USA market had their main castings poured in India and then shipped to England where the column, knee and table were built up. The part-finished millers were then sent to America where Singapore-manufactured heads were fitted and the machine put through final assembly and painting (at least, that's the story from an ex-employee.). Even so, one would have though a single plant could have achieved cost savings equal to or even better than those involved in packing up and shipping components half-way around the world and back again.
After a series of ownerships, management buy-outs, amalgamations and trading, Bridgeport eventually became part of the Goldman Industrial Group together with other leading machine tool companies including Bryant Grinder, Fellows, Hill-Loma, J. & L. Metrology, and Jones & Lamson. In 2002 (at machine Serial Number BR-247388) Hardinge took over the rights to Bridgeport's knee-mill designs (on a 7-year arrangement) and then, in November 2004, acquired full rights to the Bridgeport name to join Hardinge-branded high-precision lathes, Kellenberger cylindrical grinding machines, Hauser jig grinders, Tschudin high-production cylindrical grinders, Tripet internal-grinding machines and Hardinge-branded collets, chucks and indexing fixtures. In the UK the Bridgeport division, formerly based around Adcock & Shipley in Leicester, continued in operation - but not the Bridgeport manufacturing operation which, by November 2004, was in receivership. A total of $7,250,000 was paid by Hardinge for the acquisition but this included finished goods (including CNC machining centres) worth an estimated $4,100,000.
The continued use of the Bridgeport name seems assured with Hardinge currently having over 800,000 square feet of manufacturing capacity in its operations in England, the United States, Switzerland, Taiwan and China..
An interesting article about manufacturing the Bridgeport can be found in the American Machinist Magazine for 1st November, 2000..

Bridgeport Series 1 "9BRM" and "12BRM" 0.5 hp. turret miller designed as a "medium-light duty" machine. The model was identical to the BRJ but fitted with the lighter Model M Head.

Bridgeport Milling Machines
Milling, Drilling & Boring Heads Models M, J, 2J and 2J2

A range of different heads and head accessories has been available for the Bridgeport since its introduction, allowing the customer to choose between heavy-duty, fixed-quill models and very high-speed "sensitive" units with either (or both) power down and up feeds and hand operation though worm-and-wheel fine-feed or quick-action, sensitive drilling mechanisms. Heads were at first available with a choice of either a No. 2 Morse taper, or Brown & Sharpe No. 7 or B-3 tapers - but later the "designed-for-Bridgeport" R8 fitting became the standard. Whilst some heads will fit only on the front of the ram, others can be mounted on the back as well; details of the adaptors that allow rear mounting can be found here.
In the past a variety of heads were been available, including:
Model M*, the original head - see the bottom of this page.
Model R for heavy-duty use, but with a fixed quill.
Model C* for light-duty, high-speed use, with a sliding quill.
Model T for Cherrying.
*can be mounted at rear of the ram.
For many years the standard head was the V-belt drive "Type J" fitted, for slow-speed work, with a lathe-like backgear assembly. This was joined by what was, at first, listed as the "Type J Varidrive" but later called the "2J": fitted with expanding and contracting pulleys this provided, in conjunction with its standard fit backgear, two infinitely-variable speed ranges that ran from 50 to 450 rpm and, in direct drive, 450 to 3750 rpm - though small changes in the mechanical specification (and the type of electricity supply) dictated that these ranges did vary somewhat from country to country. By the 1990s the "regular" head had become the infinitely variable speed 2 h.p. Model 2J2, or, at a saving in cost, its less powerful predecessor the Model J with 12-speed V-belt drive. The J2J and 2J both had hand-operated and power feeds - and both quick-action drilling and fine-feed quills. To increase the versatility of these heads a special right-angle extension drive, the "Quillmaster", used to be available and even this could be further modified by the addition of a right-angle tip drive, the "QRA" or "Quillmaster Right-angle Attachment". Details of the Quillmaster and its capabilities can be found here.  Also available for many years was the Model T slotting and forming head.
For new Bridgeport owners it is worth noting that, whilst the speed setting dial for the variable-speed head can only be turned whilst the motor is running, to engage backgear (and the slow speed range) the head should be stopped and the spindle "jigged" backwards and forwards until the gears engage. Importantly, in backgear, the spindle runs in the reverse direction to normal and hence the reversing switch has to be used to get the cutter rotating correctly..

2J2 Head showing the disposition of the variable-speed drive and air-flow route through the head and motor.

For most late-model machines the Model 2J2 was the "Standard" head offered for the Series 1. It had a 2 hp. (1.5 kW) motor driving an expanding and contracting pulley system, incorporating a lathe-like "backgear", to give infinitely variable speeds from 50 to 3750 rpm.
Like all Bridgeport heads the quill was hard-chrome plated, ground and then lapped to fit the honed bore in the main casing. The handles of both the quick-action drilling  ("sensitive") and wheel operated fine-feed were detachable and three rates of power down (and up) feed provided.
The spindle was fitted with a brake - to slow it rapidly from high speeds - that could also be positively locked to aid tool changes; a clutch, designed to slip in overload conditions, protected the spindle from damage.
As a point of interest 3 different lengths of drawbar were used on the 2J2 head: 19.5", 23.5" and 26.5" - so, if the one with your  newly-acquired machine doesn't fit, now you'll know you know why .

Model M Head
This was the head fitted to the first Bridgeport milling machines and had 3.5-inches of quill travel through both fine and quick-action feeds by hand operation only.
The spindle could be ordered with a No. 2 Morse, B & S No. 7 or a B-3 taper - and the maximum collet capacity was 0.5 inches. Special tapers were available to order and it is highly likely that a factory already equipped with tooling to a different specification might have ordered its machines so as to be able to mount cutters already in stock.
The 0.5 h.p. motor was available as either a 1200 rpm unit - which gave spindle speeds of 275, 425, 700, 1050, 2100 and 4250 rpm - or as a 3600 rpm model with rather higher spindle speeds of 950, 1350, 2200, 3250, 6500 and 12000 rpm. 
The unit could be mounted either on the front or back of the ram and, if on the latter, fitted to a swivel adaptor that allowed it to be angled in both planes.
Details of the various head mounting adaptors can be found below.

Model J Head
This unit, after the original M head and before the introduction of the variable-speed 2-hp head, was the standard Bridgeport fitting but was then offered as a cheaper alternative to the 2J2. The counterbalanced R8 quill - hard-chrome plated and ground, then lapped to fit the honed spindle bore - had 5-inches travel and was fitted with both hand and power feeds. The hand feed could be applied through either a quick-action lever when drilling - or by a handwheel for fine feeds. The power feed, at the rate of 0.0015, 0.003 and 0.006 inches per spindle revolution, worked in both directions and could be set to trip out automatically; a 0.001" graduated micrometer stop was fitted as standard. A wide range of spindle adaptors was available to mount a variety of tooling.
Whilst the specifications of more recent versions of the head varied, in the past a choice of two 1 h.p. motors, each wired for reverse, was offered (and others, possibly, depending upon the year of production); a 1800 rpm unit that gave (in direct drive and "backgear") spindle speeds of 80, 135, 220, 330, 660, 1100,1800 and 2720 rpm - and a 3600 rpm version that had the effect of doubling each of the aforementioned speeds.
When vertical, the head could be run continuously  - but needed modification to the lubrication system if used in the same way horizontally..

The original product of Bridgeport, the Model C Head: fixed quill for light-duty but high-speed use with a 2-bolt flange fitting.
Motor 1/4 h.p.
Speeds: 465, 675, 1000, 1500, 2140 and 4250 rpm.
Height: 26 inches
Depth: 11
13/16 inches
Width: 8
3/8 inches
Collet capacity:  1/2 inch
Spindle fitting: B-3

Model R Head: fixed quill for heavy-duty use with a 4-bolt flange fitting and a larger spindle and bearings.
Motor 1/2 h.p.
Speeds: 275, 425, 700, 1050, 2100 and 4250 rpm.
Height: 21
3/16 inches
Depth: 15
inches
Width: 9
1/8 inches
Collet capacity:  13/4 inch
Spindle fitting: R-8

The Model T Cherrying Head was designed to assist with die sinking work. The head carried an oscillating quill that could move the cutter through both convex and concave circular paths to perform rough and finished cherrying operations. The radius of operation was adjustable from 0 to 1.75 inches.
The unit could also be used for conventional milling when the quill was locked.
Motor: 1/2 h.p.
Speeds: 275, 425, 700, 1050, 2100 and 4250 rpm.
Spindle: No. 2 Morse, 7 B 7 S or B-3 taper. 
Collet capacity: 1/2 inch
Height: 27
3/8 inches
Depth: 20 inches
Width: 173/8 inches
A head with a similar function was manufactured by the Everede Company of Chicago, IL, USA. This was made in at least two versions, the RH-1 and the manual had RH-2. Details are sketchy and, unfortunately, the maker's handbook almost useless in describing their functionality.

The Slotting Head, mounted on the back of the ram, swung into its working position

Model E Slotting (Shaping) Head.
Motor: 1/4 h.p.
Stroke length: 0 to 4 inches in increments of 1/4 inch. 
Stroke rate per minute: 70, 100, 145, 205, 295 and 420.
Height: 20
13/16 inches
Depth: 17
7/16 inches
Width: 8
1/8 inches
The unit could be mounted on the back of the ram, ready to be swung into position should the job demanded it.

Quillmaster Attachment for the M, T and J heads.
On the left the Type MA for the M and T heads - and on the right the Model JA to suit the Type J Head.


QRA Attachment.
The Quillmaster Right-angle Attachment was designed to fit on the end of the Quillmaster unit.

Above: No. 3 right-angle attachment for the Model J Head. This heavy-duty 4 to 3 reduction unit was very well made with hardened and lapped spiral-bevel gears and the hollow spindle, designed to accept standard R-8 tooling,  running in pre-loaded ball bearings. The attachment is shown in combination with the Auxiliary Arbor Support, a device that greatly improved its performance when used for horizontal milling. The collet capacity range was 1/8" to 3/4".

Left: the No. 4 Right-angle Attachment for the Model J Head. This was a lighter-duty, 2 to 1 reduction unit that took an N-2 collet in its spindle with a capacity range of 1/16" to 1/4".

Above: dimensions of the No.  4 Right-angle Attachment for the Model J Head.
No. 4
A = 4.25"
B = 7.28125"
C = 0.84375"
D = 1.96875"
E = 2.1875"
Collet = N-2
Collet Capacity = 1/16" - 1/4"
Speed reduction 2 : 1

Above: dimensions of the No. 3 Right-angle Attachment for the Model J Head.
No. 3
A = 4.25"
B = 6.625"
C = 1.5625"
D = 4.8125"
E = 2.375"
Collet = R-8
Collet Capacity = 1/8" - 3/4"
Speed reduction 4 : 3

No. 2 Right-angle Attachment for the Model M Head. The Spindle, with a speed reduction of 2 to 1, accepted a N-2 collet with a capacity range of 1/16" to 1/4".

Above: dimensions of the No. 1 Right-angle Attachment for the Model M Head.
No. 1
A = 3.375"
B = 5.0625"
C = 1.28125"
D = 3.375"
E = 1.875"
Collet = B-2
Collet Capacity = 1/16" - 1/2"
Speed reduction 2 : 1
Min. working space: 4"

Above: dimensions of the No. 2 Right-angle Attachment for the Model M Head.
No. 2
A = 3.375"
B = 6.5"
C = 0.84375"
D = 1.8125"
E = 3.1875"
Collet = N-2
Collet Capacity = 1/16" - 1/4"
Speed reduction 2 : 1
Min. working space: 2.625"

Mounting Adaptors for J and M Heads

Double Overarm for J Heads

Dovetail Mounting for J and M Heads.

Universal for M Head

Hand Miller type B for M Head

Dual Type for M Head

Single Overarm for J Head

Hand Miller Type for M Head

Adaptor Plate for Type  J and M Heads

email: tony@lathes.co.uk
Home   Machine Tool Archive   Machine-tools for Sale & Wanted
Machine Tool Manuals   Machine Tool Catalogues   Belts   
Books   Accessories

Bridgeport Milling Machines
Handbooks, Parts Lists and Spares are available for most Bridgeport machines


Original Bridgeport Round-ram Model

Accessories   

Bridgeport at Work

Tree, Halco and Kerney & Trecker (Dalrae) Vertical Attachments

Table Power-feed Units   

Bridgeport Serial Numbers

Bridgeport Horizontal Stub Miller

Further Bridgeport Company History and "Building a Bridgeport"