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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.
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03-23-2020, 04:52 PM   #2
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Nice write up. I have the twin rod and agree with everything you say.
03-23-2020, 07:58 PM   #3
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Shoot, my twin rod spanner will be hi tomorrow.
I ordered them last Thursday.

They may get modified, if they are as bad as you say.
03-23-2020, 08:51 PM   #4
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thanks! as at some point I will need or actually purchase a proper tool as I use stuff from my dad's old drafting kit and various other things

03-23-2020, 10:50 PM   #5
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Thanks for the article! I long puzzled over which spanner to buy, and ended up buying a cheap twin bar. But I find I often make custom spanners for small lenses from a washer or small coin. All it takes is a couple of metal files and a small vise. The custom spanner can be made to precisely fit the slot while clearing the lens and camera/lens mount. The ability to make custom tools such as spanners and screwdrivers that fit the wide, but thin slots on the screws used in cameras is very useful for working on camera equipment.
03-24-2020, 06:29 AM   #6
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QuoteOriginally posted by pschlute Quote
Nice write up. I have the twin rod and agree with everything you say.
Thanks.

QuoteOriginally posted by Riggomatic Quote
They may get modified, if they are as bad as you say.
I find that the twin-rod style is usable, but it's a bit finicky. I find I need to take special care in adjusting it for the job at hand. They are available under various brand names, and it's possible that some are better than others (mine is a Neewer brand, IIRC). It would be great if you could return and comment on your experience with it.


QuoteOriginally posted by Aaron28 Quote
thanks! as at some point I will need or actually purchase a proper tool as I use stuff from my dad's old drafting kit and various other things
Thanks for your comment. I think you'd find that a real spanner will result in a more confident repair job. I have a couple of drafting kits, and found the hinged-leg dividers to be too flimsy for this type of work (not to mention the feeling that my first-year drafting prof was looking over my shoulder with disapproval at this misuse of the instrument!).

QuoteOriginally posted by MadBill Quote
The ability to make custom tools such as spanners and screwdrivers that fit the wide, but thin slots on the screws used in cameras is very useful for working on camera equipment.
Good point about the screws. I've modified a couple of flat screwdrivers for my camera repair toolkit using the approach you mention. Having a Dremel or similar rotary tool helps.

- Craig

Last edited by c.a.m; 03-24-2020 at 07:05 AM. Reason: spanner brand
03-24-2020, 06:53 AM   #7
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QuoteOriginally posted by c.a.m Quote
Thanks.



I find that the twin-rod style is usable, but it's a bit finicky. I find I need to take special care in adjusting it for the job at hand. They are available under various brand names, and it's possible that some are better than others. It would be great if you could return and comment on your experience with it.




Thanks for your comment. I think you'd find that a real spanner will result in a more confident repair job. I have a couple of drafting kits, and found the hinged-leg dividers to be too flimsy for this type of work (not to mention the feeling that my first-year drafting prof was looking over my shoulder with disapproval at this misuse of the instrument!).



Good point about the screws. I've modified a couple of flat screwdrivers for my camera repair toolkit using the approach you mention. Having a Dremel or similar rotary tool helps.

- Craig
Good to know. I should be able to find some time to mess around with it and report back. Should be in the mailbox around noon today.

Update, They didn't arrive today. .


Last edited by Riggomatic; 03-24-2020 at 08:57 AM.
03-24-2020, 08:30 AM   #8
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Good piece Craig. Having used and not infrequently struggled with my cheap twin bar spanner for a few years now I can endorse your comments and emphasise the desirability of:

- offset tips (more important than swappable tips, 3mm flat and 1mm point do 99%)
- good lock action on the bars - bad news if they slip. Even after modding mine with my dremel (added coin slots on the knurled knobs for quick tightening, roughened and flattened the bars) it's still not great.
In fact overall I would advise everyone to get a better one than this type, even though they are very cheap.
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Last edited by marcusBMG; 03-24-2020 at 08:36 AM.
03-24-2020, 08:39 AM   #9
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I wish you had written this before I bought my twin rod spanner. I too found them hard to use and haven't used them since 4 or 5 years ago because my Essential Tremors makes them even harder to keep them steady.


Nice write up though, and I'm sure it will help others to not buy the twin rod spanners.
03-24-2020, 06:39 PM   #10
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The reviews I've read indicated that the Japan made hinged caliper type was the best. With the single bar type being marginally better than the twin rod type, though quality varied wildly with both models. Most likely due to sloppy manufacturing tolerances.

Thank you for confirming this. The extra cost of the caliper type is probably worth it in the long run.
03-25-2020, 06:50 AM   #11
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QuoteOriginally posted by marcusBMG Quote
Having used and not infrequently struggled with my cheap twin bar spanner for a few years now I can endorse your comments and emphasise the desirability of:- offset tips (more important than swappable tips, 3mm flat and 1mm point do 99%)- good lock action on the bars - bad news if they slip.
Thanks for your useful comments. Good point about the offset tips -- I use mine frequently to either attain a very narrow span or to provide clearance in tight spaces.

QuoteOriginally posted by photolady95 Quote
I wish you had written this before I bought my twin rod spanner.
If only I had known! Thanks for your comments.

QuoteOriginally posted by Not a Number Quote
Thank you for confirming this. The extra cost of the caliper type is probably worth it in the long run.
Yes, I tend to agree. I've never regretted spending a bit more for quality tools. While I favour my 'V-style' spanner, I do use my other spanners occasionally.

- Craig
03-25-2020, 07:48 AM   #12
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QuoteOriginally posted by c.a.m Quote
Yes, I tend to agree. I've never regretted spending a bit more for quality tools. While I favour my 'V-style' spanner, I do use my other spanners occasionally.
You could always set them and leave them at that setting. There are probably a few common diameters or if you work on the same model lenses that this would not be impractical. Slippage though is a problem.
07-08-2020, 10:53 AM   #13
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I have a Tokina lens with a deeply recessed lens group.
My twin-post spanner won’t reach in far enough, and the shafts are too wide for the bit tip to reach the slots anyway.
I have the same issue with any of my spanner alternatives, and I expect the V spanners would also do that.

The optimal tool seems like it would be a metal plate of the right length and width, with the end field down to the right thickness.
The ones I’ve had handy haven’t been thick enough and have just bent.

Is there a spanner that is designed for such a deep dive?

-Eric
07-08-2020, 11:48 AM   #14
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Custom spanner tips

QuoteOriginally posted by TwoUptons Quote
Is there a spanner that is designed for such a deep dive?
Great question! I've had exactly the same situation when working on the rear lens block in a rangefinder camera. I'm not aware of a spanner with long, narrow tips.

I ended up fabricating custom tips from a cheap $5 set of 'miniature screwdrivers' similar to this set: amazon.com: Herco HE826 Precision Screwdriver Set: Musical Instruments?tag=pentaxforums-20&

I bought two sets from a local hardware store to get matching pairs of tips. The tips are strong enough that they don't bend under moderate stress, and the pointed ends have not fractured. It took a few minutes with a Dremel tool* to cut the shaft and fashion the tip, but the same job could be done with a hacksaw and file.

My twin-rod spanner accepts shafts up to 5 mm diameter.

Here's a quick picture of the tips, which I hope shows the idea. The scales are in inches and centimetres. (Apologies for the poor exposure -- it was a quick kitchen-table shot with a *ahem* point-and-shoot!)

* Safety note: When using power tools, it's important to keep your safety in mind. When using my Dremel, I wear safety goggles, ear protectors, and gloves, and keep my workspace uncluttered.


- Craig


Last edited by c.a.m; 07-08-2020 at 05:48 PM.
09-30-2021, 06:52 AM   #15
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Indeed, just what I needed for my Pentax spotmeter V eyepiece retaining ring! Thanks for the tip!
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