We (or I) need a better spanner

[Struan Gray]

If there's aluminium corrosion in the threads you may never get it off, at least not without bending something that should be straight. Even if you manage to grip the locking ring securely, you still have to somehow apply a torque to the barrel or shutter, and that can munge the shutter body.

If locked in place by corrosion, cutting the ring off, cleaning the threads and finding a new ring may be the safest option. Cut one or more radial slots in the ring and prise it out and away from the shutter/barrel thread),

I have applied the largest, most steady, and most stable forces to rings by locking two screwdrivers upright in a bench vise. This lets you use two hands to hold the shutter/barrel and turn it.

Hammer tools are great for breaking a locked screw or bolt, but I don't know of any that will apply an even impulse around a retaining ring, or even on two or three slots around the rim.

[Drew Bedo]

This won't help at all—but it is a good story:

Back in the early 1990s I bought a number of oscilloscope cameras from a surplus dealer at <$10 each. They had those 75mm/f1.9 lenses in an Alphax shutter. The lenses were easy to get out of the cameras but each had an aluminum collar screwed onto the barrel of both the front and back lens cells. I tried all the things mentioned above; penetrating oil, heat and at last, massive torque. Nothing I could do worked. So I took them to a local gunsmith. It took a bit of convincing to get him to chuck up one of these lens cells in his athe. I had to reassure him that they were salvaged and inexpensive . . .it would be OK if it damaged the lens. THAT is what it took. He cut off each collar in about 20 min overall. The lenses got sold at the Houston Camera Show on the morning of th first day.

Some solutions are way out of the box!

[Jac@stafford.net]

I slept on the problem, re-read the very helpful posts here and have decided that rather than removing the lens from the mount I will build the camera around it. The 'board' is a recessed alloy lens cone with a focusing helix. The retainers are three concentric steel rings. It could be no sturdier than it is now!

Thanks for the help. I think machining as Drew Bedo mentioned would be the solution for this case.

[Drew Bedo]

Machining on a lathe was the last resort. It is important to emphasize that the lenses I had were salvaged and cost me $10 each.

[Jim Jones]

A toothpick is a more precise tool than a Q-Tip or syringe for applying tiny amounts of solvent or lubricant.

[Drew Wiley]

I make my own by grinding the tips of right-angle pliers.

[domaz]

To free really stubborn retaining rings and lens collars I put the spanner in my vise, with the business end facing up. Then- put the lens firmly on the spanner, in the right position and "unscrew" using the whole lens. A little risky if the spanner pops out of position, but very effective way of getting lots of force on it.

[HMG]

Drew Bedo's comment reminded me that I visited an engineering and machine shop recently. CNC machines on one side and Bridgeport's with digital readouts on the other. I bet those Brridgeports could cut down the ring and leave the threads intact or cut a slot through ring and threads leaving thread usable.

[HMG]

I make my own by grinding the tips of right-angle pliers.

Do you grind flat or to a point?

[Tin Can]

I forgot to add Metal Disintegration machines. This is first time I have watched on You Tube. This procedure saved several $100K prototype engine blocks in my career.

Seems simple enough, but 20 years ago it was secretive and rare.

https://youtu.be/YbeKxFBZrF8