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Lens Spanners -- Using the right tool for the job
Posted By: c.a.m, 03-23-2020, 04:19 PM

Lens Spanners – Using the right tool for the job


Introduction

Like other repair jobs, fixing cameras and lenses requires proper tools. The lens spanner wrench, or spanner for short, is an essential specialized tool that is used to remove lens retaining rings and collars, small caps and covers, and screws with special heads.

Disassembling and refitting the components should be done carefully to avoid damage. Although make-shift spanners are feasible and may seem to be cost-effective for an occasional job, using a proper tool increases the likelihood of success and reduces the risk of inadvertent damage. In hindsight, I am glad that I invested in several spanners, which have served well in my successful repair efforts.

A search on the internet will reveal plenty of questions and discussions concerning lens spanners. This article is intended to provide some insight as well as an overview of my experience with several types.


General Features and Characteristics

The spanners in my toolkit are shown in the figure below.





Lens spanners are available commercially in various designs, prices, and qualities. An ideal spanner would have the following characteristics:
  • Positive fit. The tip must fit securely in the component’s holes or slots, with little or no wiggle. This requires the tips to be properly sized for the job, while the shafts near the tips should be parallel to each other.
  • Free of play when tightened. The tool’s arms and the tips should not wiggle or move after the tool is tightened for use.
  • Ease of use. The tool should offer easy, smooth, and precise adjustment; an assured hand grip; no shift in tip positions while tightening; and no flex when torqued.
  • Range of span. The span should adjust from several millimetres to around 100 mm. This may not be possible in a single tool, so the user may need to acquire more than one.
  • Selection of tips. To facilitate various jobs, the spanner should accommodate several different tips, including points, flats, and half-flat. Similarly, some jobs may require a spanner with a long reach, so it’s desirable to have various tip lengths.
  • Custom tips. Certain jobs may require special tips, which the handy repair person may fabricate at home. The spanner should accommodate such tips securely and precisely. See Post 14 below for examples.

V-style

My V-style spanner is a model from Japan Hobby Tool, which I bought for approximately CAD $40.00 from Amazon. It’s also available from Micro-Tools.

The two legs, each 140 mm long, are formed from plated channeled steel and attached securely at one end by a flanged pin. The key feature of this tool is the threaded locking rod and its four nuts – this configuration provides for the desired span to be set precisely and locked securely in place. This spanner is easy to adjust and it’s rigid when tightened. It also allows a fair torque to be applied safely to a tight workpiece. The two standard tips include a point (0.5 mm) and a flat (5 mm). It meets most of the key characteristics noted above.

Its span range of 12 – 60 mm works for most jobs. A 3-mm span may be attained by using the offset tips from one of my other spanners. The included tips are relatively short, which precludes their reach into deep spaces. Luckily, the shaft holes are 5 mm diameter, which accommodates tips from another spanner for extended reach.

Because of its ease of use, secure setting, and rigid build, this is my preferred spanner.


Twin-rod Style

One of the commonly available spanners is the twin-rod, twin-arm type. This type is available from various suppliers, and its cost runs in the CAD $ 25.00 range.

The arms are 100 mm long and 10 mm in diameter. It is secured by tightening two thumb screws on each arm and a separate screw for each tip. The span range is 2 – 80 mm. My tool came with several useful tips: an offset point, a 5-mm flat, and a 2.5-mm half-flat.

While this particular spanner is fairly versatile with its various tips and useful span, I find that it’s somewhat frustrating to use. Unless the arms are kept perfectly perpendicular to the rods, they often bind when being adjusted. Furthermore, the arms are difficult to adjust and set precisely, as they move slightly when being tightened. When working at close quarters, such as removing a retaining ring for a convex lens element with little clearance, one must use this tool with particular care to prevent scratches. When the arms are properly set and tightened, though, this tool is reasonably secure and affords a fair torque.


Bar Spanner

Another common spanner features a single stainless steel bar and two arms. This type of tool is relatively simple and can be acquired for around CAD $15-20.00.

With a span range of 8 – 130 mm, this style is useful for wider retaining rings, although I’ve never encountered such wide pieces. When adjusting the span, the arms slide loosely across the bar without snagging. However, the cross section of the bar and the slots in the arms are not matched precisely, so there is an excessive amount of lateral play (2 mm) at each tip even when the arms have been tightened. I have mitigated this play somewhat by replacing one of the thumb screws with an included socket-head cap screw to securely set one of the arms, while retaining the other thumb screw for convenience. Even so, the second arm is prone to movement when set.

Another disadvantage of this spanner is that it does not accommodate other tips – what you see is what you get with a 0.5-mm point and a 3-mm flat.


Other Styles

Other styles or models of spanners are available from various suppliers. I’ll mention two that I’m aware of, but because I haven’t used either, I can’t vouch personally for their quality.

ThorlabsSPW801 Adjustable Spanner Wrench seems to be a solid precision tool, albeit more expensive than most other options at around USD $ 105 or CAD $ 140 (as of March 2020; shipping extra). Featuring a spanning range of 3 – 73 mm, the tool has reversible flat and pointed tips. Users report that it is well made, solid, secure, and easily adjusted. One user has mentioned that the tips can wobble slightly when adjusting the span. Spanner Wrenches

SK Grimes New Design Adjustable Optical Spanner Wrench is a robust version of the bar spanner. The span ranges from near zero to 140 mm, and pointed and flat tip styles are available. It appears to be a hefty tool, affording a solid grip and precise adjustment. USD $ 56 for either set of tips or $ 97 for both (as of March 2020; shipping extra). Spanner Wrenches SKGrimes


Home-made Spanners

As illustrated in a Pentax Forums article (https://www.pentaxforums.com/forums/114-maintenance-repair-articles/199396-s...bstitutes.html) there are many possibilities for home-made spanners by re-purposing common workshop items:
  • Vernier callipers
  • Needle-nose pliers
  • Scissors
  • Marking or measuring dividers
  • Pins held in locking pliers
  • Nails through a piece of wood
While any of these make-shift tools might work for some jobs, my opinion is that their use depends on luck that they won’t slip and scratch a lens element or mar a visible metal component. In particular, any non-locking tool such as scissors or pliers cannot be controlled with assurance. Furthermore, some of the tools do not have parallel arms, so the tips will not fit positively or securely in the workpiece.

I hope that you have found this article to be useful.

- Craig

Last edited by c.a.m; 07-11-2020 at 05:21 PM.
Views: 3,881
10-09-2021, 11:06 AM   #16
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One item not shown is a set of expanding spanners. When I retired from the bench, I left mine at the shop. I couldn't have done lens repair without.
I suspect these originally came from the Army Air core service kits. I wish I had a picture, but simply put, they were round and expanded, different sizes were made with a split ring. These were for inner barrel repair.

I grew up using the National Camera twin bar with interchangeable tips, and made many special tips.

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