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The Leica Camera British Intelligence Objectives Sub-Committee 1946

Updated: May 1


"This report is issued with the warning that ,

if the subject matter should be protected by

British Patents or Patent applications , this

publication cannot be held to give any protection

against action for infringement ."




Purpose of investigation................... 1

Details of journey......................... 1

Introduction............................... 1

General description of factory............. 2

Leica Camera - Manufacturing Processes..... 3

Machine Tools and Methods.................. 3

Cutting Multiple Threads................... 4

Optical Manufacture........................ 5

Satin Chrome Finish........................ 5

Assembly and Testing....................... 6

Shutter.................................... 6

Shutter Timing............................. 6

Shutter Blinds............................. 7

Lens Flange................................ 7

Setting Telemeter.......................... 8

Testing of Lenses.......................... 8

Final Test................................. 8

Drawing Office............................. 8

Research and Development................... 8

Labour..................................... 9

Working Hours.............................. 9

Wages...................................... 10

Production Costs Etc....................... 10

Other Products............................. 10

General Conclusions........................ 11

Appendix "A" . Works Notice........... 12/13

Appendix "B" . Wage-Groups with Age-Gradings

for Men and Women......14/15

Subject Index.............................. 16







Reported by:-

Mr. H. J. Bigg.

Mr. L.G.H.Cantle

BIOS Trip No:- 2858

BIOS Target No:- 9/14

Dates of Investigation.

19th.November 1946


25th.November 1946.


Page 1.

1. The purpose of the investigation was to examine the

methods of manufacture and constructional details of the Leica

Camera with particular reference to finish, assembling and

testing. It was not intended that the team should cover the

manufacture of the lenses, although some details of the

construction of lenses were noted and are included in the report.

One member of the team examined the microscope manufacturing

side of the business but was unable to add any useful information

to that already obtained.

Details of Journey.

2. The Team left England on the 15th November, 1946 and

returned on the 28th November, 1946. Of this period only that

from the 18th to 26th November was spent in Germany and the

investigation at the Leitz Works was carried out on 19th, 21st

and 22nd November. Subsequent visits to the Leitz works w


made by the Leader and one member of the team on the 25th and

26th November to collect documents for the removal of which

permission had to be obtained.


3. Close co-operation with the U.S. Scientific Consultant

Section was necessary and it was considered advisable that the

team should be accommodated at Hoechst, near F.I.A.T. Head-

quarters, and proceed by road to Wetzlar for each day of

investigation. This proved to be a very happy arrangement

and cordial relations were established with the U.S. Scientific

Consultant Staff which were of inestimable value to both the

Americans and ourselves.

4. Before the investigation at the Leitz Works was

proceeded with the micro-films taken at the Leitz Works by a U.S.

Army Micro-film Unit, and filed at F.I.A.T. Headquarters, were

examined by one member of the team and it was soon established

that these films were, from a practical angle, completely use-

less. Although all drawings and documents at the Leitz works

had been filmed they had been so completely mixed up that it

would have taken a very knowledgeable Leitz executive many

months to sort out those relevant to the Leica Camera.

5. At a meeting with B.I.O.S. and the U.S. Scientific

Consultants Section it was agreed that the team should be author-

ised to remove copies of the drawings for the Leica III B and

III C or, alternatively, that another micro-film unit should be

sent to the Leitz Works to take a fresh set of films, under the

direction of a member of the Team. The U.S. Scientific Consult-

ants Section also indicated their interest in the investigation

at the Leitz Works and decided to send a team to join forces with

the British Team.

6. The investigation, therefore, proceeded as a joint Anglo-

American investigation although members of each team made their

own notes and reported to their own team leader. It is empha-

sized that this report is the result of the investigation of the

British Team and is not a joint report.

7. The British Team split at the works to cover various

fields such as machining methods, assembly, testing,inspection

and organisation. This report is a consolidated result of

their findings.

8. The persons interviewed were;-

Herr Ernst Leitz (Senior). Chairman

" Ludwig Leitz Technical Director

" Dumur Commercial Director

and various members of the technical staff of

E. Leitz.

We received every help and courtesy from these persons and a

considerable amount of assistance from Mr. Dumur.

Page 2.

General Description of Factory.

9. The Leitz Factory, situated at Wetzlar, comprises a

number of buildings built over a period of years. In conse-

quence some of the departments are old-fashioned and badly

lighted whilst others, notably the new eight-storied building

standing in the centre of the factory site, are modern and well


10. The plant and equipment varies similarly but is all well


11. Besides the main Leitz works, the firm of W. & H. Seibert,

Instrument Makers, is owned by Leitz and they have a few

dispersal works for pressings etc.

12. As the chief employees of labour in this beautiful little

town, the Leitz Company can rely on continuity of service and

have adopted a very sound policy of training young labour from

apprentices. They take pride in the skill of their workers

and have welfare and other schemes which help to this end. As

a result there is a high percentage of skilled labour employed

and the general labour is highly skilled in the particular


Page 3.

Leica Camera - Manufacturing Processes.

13. The Leitz Company is now producing only the Model III C

Leica Camera, this having by development, superseded the

Model III B. The Model III C differs from the III B in several

aspects, although it is functionally similar. It is approx-

imately 1/8" longer, it has an integral top plate and range

finder cover, and the main body is now a single pressure die

casting, which together with two other pressure die castings for

the top and bottom of the unit forms a complete chassis for the

assembly of all the other component parts. In the later models

the focal plane shutter blind rollers have been fitted with ball


14. The outer case of the Leica although 1/8" longer is

formed from extruded tube as was the case in the III B and

earlier models.

15. The coupled range and view finder has not been altered

in any way.

16. Leitz make in their own factories practically all their

requirements, including the leather cases for cameras and


17. Of the items bought out, the castings come from Mahle of

Stuttgart, slow speed shutter mechanism from Gauthier of Calmbach,

shutter tape from Soenecker & Pfaff of Wupperthal Barmen, and

blind material from America through their associated company in

that country.

Machine Tools and Methods.

18. In the machine tool side the following machines were

noted:- Steinel Drilling Machines, Lindner Thread Grinder,

Deckel Engraving and Horizontal Milling Machines, Lorch Lathes,

Sooda Automatics, Mikron Gear Hobbers and Hauser Jig Borer.

The chasing lathes were by Hille.

19. The general machining of small precision parts followed

very closely the usual procedure in this country.

Page 4.

Cutting Multiple Threads.

20. The cutting of the multi-start thread in the focussing

mount of the Sumitar and the Elmar lenses was carried out on a

converted Lorch Lathe. The conversion of this machine by Leitz

was extremely ingenious. The component to be screw-cut was

screwed on to an attachment on the head-stock of the lathe by a

chucking-thread already cut in it. A single tool was employed

in the tool post. The whole head-stock was then caused to

oscillate backwards and forwards by a thread attached to the

back of the head-stock engaging with a chasing nut which was in

turn engaged and disengaged at the end of each stroke by a yoke

which also operated four glass-mercury switches. These

switches operated a solenoid attached to the drive counter

shaft which, in turn, operated a reversing clutch in the drive.

The head stock was caused to rotate for some ten revolutions

in a clock-wise rotation which moved it forward by the chasing

thread on it engaging with the chasing nut. At the end of

this forward stroke the chasing nut disengaged and then

re-engaged with the next thread, the counter shaft also re-

versing, causing the head-stock to rotate in an anti-clockwise

direction on the back stroke for some ten revolutions. As the

head-stock oscillated backwards and forwards at each successive

movement it engaged with a conveniently disposed paul which

engaged with a ratchet connected to the feed on the tool post

and at each backward and forward stroke the tool was automat-

ically fed in. The extent of this was shown by a clock

indicator attached to the tool post slide. The device worked

well and was almost "fool -proof" to operate.

21. The male 5 start thread was cut first on one lathe of

the type just described. The female member was cut in an

identical manner but to suit the male thread. A certain amount

of play was purposely left between the two, when dry, but after

both had been well washed out in paraffin a liberal application

of special grease was applied and they were assembled together.

The special lubricant caused them to have a very fine "velvety"

feel when moved in or out. As male and female members are

machined to suit one another it is very doubtful if any two

complete units are dead alike as regards inside and outside

diameters of threads. Mr. L. Leitz agreed that this was so

but added that once a lens focussing mount was assembled it

became a unit for good and it did not need to be interchanged

with parts from another complete lens mount.

22. The pitch of the 5 start thread in the focussing mount

of the Sumitar was 6.210 mms., but in the case of the Elmar a

pitch of 6.00 mms. and also 6.138 mms. was employed.

To ensure lineality between movement of the lens and the

coupled telemeter a slight cam is machined on the end of the

male member of the multi-start thread which engages with the

roller which actuates the swinging prism of the telemeter. The

greatest depth of this cam face does not appear to exceed .007".

Page 5.

Optical Manufacture.

23. The manufacture of small prisms as used in the tele-

meter were by mouldings cemented in fours and then gang-milled

by diamond milling tools. They were then taken apart and

milled to the other face. Diamond tool milling machines are

used for slotting the hypotenuse. Smoothing and polishing was

achieved by normal type poker-arm machines. Edging was carried

out on small lens in the telemeter by diamond wheels. These

wheels are made for Leitz by Jung of Berlin.

24. The small reflecting mirror in the range finder is very

lightly alluminised, the degree of deposit being just sufficient

to give an equal degree of brightness to both the directly and

indirectly received images when seen through the range finder


Satin-Chrome Finish

25. The satin-chrome finish on external metal parts was

obtained by the following process:-

26. Sandblast, hot cleaner without current, cold cleaner

with current, warm rinse, followed by cold rinse, hydrochloric

dip, copper flash, cold rinse, sulphuric dip, cold rinse, bright

nickel-plate, warm rinse, hydrochloric dip, bright chrome,

drag-out rinse, cold rinse, hot rinse, and dry.

27. All articles were jigged on racks and the racks were

screened to obviate side-throw.

28. The bright nickel tank was approximately 6' x 2' x 21/2',

six depolarised anodes being employed. The volt-meter and

ammeter on the resistance control board were all moving

coil pattern and the tank was worked at 2 volts, 25 amps. No

agitation of the electrolite was employed.

29. The chrome tank was approximately 4' x 2' x 21/2', twenty-

eight strip anti-monial lead anodes being employed. Moving

coil volt and ammeters were also fitted in the resistance board

and the tank was worked at 51/2 volts, 300 amps.

30. It was particularly noted that the time allowed for a

satisfactory chrome deposit was exactly three minutes. All the

plating equipment was spotlessly clean.

Page 6.

Assembly and Testing

31. The Model III C takes longer to assemble than its

predecessor, 33 hours as compared with 29 hours, but there is no

doubt that as an engineering job it is far superior.

32. Sub-assemblies were batched in tens and assembly practice

was very similar to that employed in most instrument factories.

Special jigs, fixtures, and tools were employed where-ever

possible to assist rapid and accurate assembly. Female labour

was used for the minor assemblies, the male labour being

employed mainly on shutter and range finder assemblies and on



33. The main design of the shutter is in no way basically

changed; only slight modification of various components to

suit the new assembly. In the assembly of the shutter fast-

range escapement one component after another was tried till one

was found that worked in a fairly satisfactory manner and then

various minor alterations were made to it by filing, and in

some cases, a light tap with a small watch-makers hammer. The

skill of the operators was undoubtedly the chief asset in the

efficient assembling of this shutter.

34. The slow speed escapement of the shutter is made by

Gauthier of Calmbach.

Shutter Timing.

35. The timing of the fast range of the shutter is carried

out with the aid of a stroboscope of somewhat antique design.

By means of this the 1/200, 1/500 and the 1/1000 speeds are

checked. The stroboscope consists of a revolving drum placed

horizontally, with 33 horizontal slits in its surface,

illuminated from inside by a lamp of approximately 20 watts.

The drum is driven by a belt from an electric motor which may

be controlled by a rheostat. The drum is also coupled to a

speedometer in order that its speed may be set. The correct

speed for the drum to rotate at was 280 r.p.m. The camera

is held on a wooden block in such a manner that the light

from the rotating drum falls on the blinds of the focalplane

shutter. The shutter is then fired and a series of

stroboscopic lines are seen in the aperture. If the shutter

is correctly set these lines appear vertically but if the

shutter is incorrectly set the lines will curl down either to

the left or to the right according to whether the shutter is set

too slow or too fast.

36. The checking of the lower speeds was only carried out

on the 1/20 second and 1/4 second settings by means of a

revolving series of lights. The various speeds of the shutter

were not accurate to the measurements on the shutter control

knob and this fact was acknowledged by the Leitz executives.

who pointed out, however, that the results obtained were quite

good enough for all general requirements.

37. A metronome was used in checking the one second


Page 7.

Shutter Blinds.

38. The fixing of roller blinds and tapes on the focal-

plane shutter was carried out on a very ingenious fixture.

The body of this fixture is all metal and accommodates the

two roller blinds and tapes on pivots ensuring that the blinds

and tapes are of the right length and fixed at exactly the

right distance apart. After the blinds and tapes have been

stuck to the rollers they are allowed to dry for at least

48 hours before being assembled into a camera. In every

possible operation special jigs and fixtures are used to

increase speed and uniformity of production.

Lens Flange.

39. The checking of the lens flange of the focalplane for

squareness is carried out by a focalplane collimator which is

located by the lens flange and directs a beam of light on to

a polished reflecting surface which is located on the focal

plane. Lack of squareness and an accurate measurement of the

extent of the error is at once visible on the graticule of the

collimator. When correction is necessary a specially adapted

vertical milling machine is used to correct the orientation

of the base of the camera body which corrects the lens flange.

If small errors in squareness occur which are not sufficient

to warrant machining, the lens flange is packed with a small

shim. The correct distance from the front of the lens

flange to the film pressure plate, located at the back of the

focal plane is 28.80 mms. which is the equivalent to 1.134".

40. Checking of the measurement was made by a special fixture

and a clock indicator.

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