MPP USERS CLUB - MAKING CAM PLATES

INSTRUCTIONS FOR MAKING RANGE FINDER CAM PLATES

MicroTechnicals Mk's VI to VIII and S92 Cameras

Technical Information Section

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YOU WILL NEED

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1 - Skills and Facilities.

Accurate measuring and marking out of material.

Precision drilling, filing, thread tapping and finishing.

2 - Tools

2.4mm Twist Drill

2.3mm Twist Drill - Mk VII and Mk VIII only

6BA Tap - Mk VII and Mk VIII only

3.8mm Twist Drill - Mk VI and S92 only

3 - Material

1 Piece Steel Strip (or brass or hard plastic - see text)

75mm long x 25mm x 1.6mm thick (3 inches x 1 inch x 1/16th inch)

4 - Obtain Working Drawing

Download engineering drawing. The link is at the bottom of the Table of Cam Angles panel.

5 - Read Notes

Read the notes to ensure you are making the right cam for the camera and lens. Updated information is given in Additional Notes.

6 - Refer To Table Of Cam Angles

This table lists cam angles for lenses of different focal lengths.

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TABLE OF CAM ANGLES & ENGINEERING DRAWING

Find The Required Cam Angle For Your Lens

Lens Focal Length (mm) Cam Angle (Degrees)

127

135

150

180

210

240

266

18.0

16.5

13.0

8.5

6.0

4.0

3.5

Download the Engineering Drawing.

Click HERE to download engineering drawing (camplatedrwg1c.jpg : 70kb)

Print on A4 paper with printer set to Landscape (wide) format.

CAMPLATE PROFILES

MicroTechnical Camplates
Focal Length (mm)	Image No.	Camplate Length (mm)
90.75	1	64
127.66	2	56
134.37	3	57
148.74	4	57
179.88	5	61
210.92	6	62
241.81	7	65
266.70	8	65

Click Image for Larger Numbered View

Camplate Profiles

Camplates are shown by lens focal length.

Length of camplates is given as the greatest distance from L to R.

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INSTRUCTIONS

Read Before Starting Work.

1
Mark out the material accurately as per the drawing.
The really critical points are the line A - C, hole centres A, B, C and the Infinity point Inf.

The Infinity point must be 7.0mm above the line A - C and above a point exactly 3.5mm from the centre of B, towards A.

2
Mark exactly the Cam Angle. This must pass through the Infinity point.

3
Drill the three holes. Drill sizes are on the drawing.
Tap hole B if required. (6BA thread)

4
Test on camera mount for a snug fit. Increase holes A and C with a small Swiss mouse tail file if necessary. Ensure a good but not loose fit on the dowels of the mount.

5
Shape to marks. Ensure the Infinity point is not less than 7.0mm above line A - C.

6
Test and calibrate making adjustments as follows using the focussing scale that matches the lens.
With the camera on a tripod, set the standard to the infinity mark on the focussing scale, and check if the cam is OK, or too high or too low. If too high, the images in the Range Finder will go apart when the arm is gently lifted. If so, remove and file off at I. It may be useful to make a narrow strip of card to use as a feeler gauge here, to slip between cam face and arm.

When OK, refocus on a subject at about 6ft, and repeat the adjustment. Next, file a smooth curve between these checking on other distances as needed.

If the cam is too low, either reset the follower on the feeler arm by loosening the slotted nut and with the top bonnet off, adjust the vertical screw, (which may need repeating for success), before retightening; or make a new cam; or spread the top edge by hammering it out a touch waiting 12 hours before refinishing to height.

Click HERE for image showing cam follower Height Adjuster.

Always try for a smooth finish, especially on the top to avoid wear.

7
Finish then mark lens details and focal length on cam plate.

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ADDITIONAL NOTES

A : Cams for MkVI and S92 have a larger (3.8mm) centre hole, and were retained by a screw from the outside rather than the inside. Details are on the drawing.

B : 90mm cams are bulky, as they have to be higher to allow for the drop bed action, and also the steep angle. They were made, but the R/F follower does not ride as easily over them, and the camera may not close with the cam in place.

C: The length of a cam depends on the focal length of lens for which it is made. Longer lenses require long cam plates.

D: Matching up a set of different cams has additional problems as they must all have the identical height at infinity. Few cameras were supplied with these.

E: Alternative materials are Brass and Hard Plastic but these do not wear as well as steel.

F: Cams for use with wideangle lenses of 90mm etc. are thought to be different between Mk VII and Mk VIII cameras. They are used with a cone lens panel (see other data on lens panels) and have different registers, being 55mm for the Mk VII and 50.5mm for the Mk VIII. Various cone panels have been noted but insufficient information is to hand to be definitive. Cam plates are therefore not readly interchangeable between models and in any event need to be used with the correct cone lens panel.