Disassembly of a vintage binocularA pictorial record is provided for the disassembly of vintage 7x50 Selsi binocular.

Selsi Lightweight Amber Coated Luminous 7X50 Field 7.1 degrees binocular

Prior to disassembly, it is strongly recommended to obtain and review a copy of “Choosing, Using & Repairing Binoculars” by J. W. Seyfried.http://www.universityoptics.com/books.htmlDisassembly of a valuable binocular is not recommended.Here is the path I took.Disassembly is not difficult if you work patiently, cautiously and gently. It is wise to make a written and or a photographic record that notes the correct placement and orientation of the components.

Firmly grip and twist off the protective external guard rings. On occasion the gentle use of a strap wrench will aid.

Remove the objective housing retaining rings with a spanner wrench. As an alternative, notch the side of a small metal putty knife with an abrasive Dremel cut off wheel so that the notched metal inserts into and just spans the retaining ring. Then firmly push into both retaining ring slots and twist.Ensure that metal never contacts the glass.

In this photo and others that follow both sides of the binocular have been disassembled. This is not advisable. It is highly preferable to disassemble one side at a time.

Now, within the objective housing take note of the eccentric objective ring – it has one slot. Insert a Jeweler’s straight slot screw driver (no larger than 1.5mm) and rotate the eccentric ring. Note how this repositions the objective cell.The objective cell and eccentric ring can now be gently removed.

Although, not pictured, using a spanner wrench or a re notched putty knife, remove the retaining ring of the objective cell. Never make contact with the glass. Be diligent and carefully note how the convex (crown) side of the glass faces out to the world.

Firmly grip and twist off the objective bell housing. On occasion the gentle use of a strap wrench will aid.

OK!Carefully remove all debris and excess grease from the threaded fasteners and then with equal care reapply, as needed, a thin film of synthetic grease. Gently rotate the fasteners until their movement is smooth. Ensure that they seat squarely. Never force the threads to fasten. Release and try again. It may surprise you how many tries it takes.Once again, carefully remove excess grease. In addition, clean and grease the eccentric ring so that it rotates freely over the objective cell.

Now comes the hard part – cleaning glass. My words of wisdom may be dubious but they do reflect trials and errors.Strong reading glasses and a well-lit work area are highly recommended.

Volatile organic solvents are a hazard. They will enter the bloodstream by skin contact and inhalation. They are flammable and explosive. Use common sense!

First and most important remove all debris from the objective. Apply a stream of air or solvent to the glass – never rub.

A solvent by definition dissolves a solute to form a solution. A solute is most likely the cause of the imperfections you see on the glass.(Mold, fungus and the loss of optical coating are a different matter)

Once you are assured that all debris has been removed from the objective

liberally apply an appropriate pure solvent. Remove the solution containing the offending solute with lens paper or an absorbent micro fiber cloth. If you reuse that portion of the absorbent material then you will simply redeposit the solute. Be patient and repeat the application of the pure solvent and, if you can, resist the overwhelming temptation to rub. A previously washed micro fiber cloth if inappropriately used may cause sleeks.

If you are satisfied with your cleaning then insert the objective, convex side facing out to the world, into its cell and secure by firmly seating the retaining ring. Do not over tighten. Place the objective cell with the eccentric ring slot, facing out to the world, into the bell housing. Loosely, thread on the objective housing retaining ring. Do not tighten. Using the Jeweler’s screwdriver ensure that the eccentric ring freely rotates. Finally, replace the protective external guard rings and store the assembly in a dust free environment. Never force the threads to fasten. Release and try again. It may surprise you how many tries it takes.

Back to the binocular – remove the central objective end cap.

On the now exposed brass fastener look for a set screw and if present remove with the Jeweler’s straight slot screw driver

Then, with care, remove the exposed brass fastener.This external fastener sets the force required to set the IPD. That is the stiffness of the hinge.

Rotate the central thumbscrew to extend the eyepieces out to their maximum extension. Insert a relatively small shank straight slot and just release the internal brass fastener. This internal fastener limits the maximum extension of the eyepieces.

Rotate the central thumbscrew to just extend the eyepieces so that they will release from the binocular.Gently pull the assembly out.

Refrain from any additional rotation of the central thumbscrew.

Note the crud!

Gently twist out the eyepiece guides.

As before, clean and apply a minimum of grease to the threads. Ensure that the eyepiece guides rotate smoothly and reseat properly.Never force the threads to fasten. Release and try again. It may surprise you how many tries it takes.

If you wish to disassemble and clean the eyepieces – go for it.It is time consuming but not difficult. Be patient and diligent – above all - be certain to keep a record of the lens placement and orientation.

Remove the eyepiece end cap screws and lift off the eyepiece end caps.

Please remember that in this photo and others that follow both sides of the binocular have been disassembled. This is not advisable. It is highly preferable to disassemble one side at a time.

Remove the objective end cap screws and lift off the objective end caps.

Gently remove the fastener that retains the prism clips

Release the prism clips from their retaining slots.

Note and record the placement and orientation of the prism and then very gently unseat and remove.

Clean the internal binocular housing.

Clean the prisms.

Take a break!Place components in a secure dust free environment. Keep a record of what goes where. Do not interchange optics.

Reassembly, of course, is the exact reverse of disassembly. However, a few pitfalls may await you.

Never force the threads to fasten. Release and try again. It may surprise you how many tries it takes.

Reseat the prisms with great care. Ensure that they are absolutely properly seated.

Reseat the eyepiece guide so that it sits in a perfectly square manner on the eyepiece end cap.

Reseat the objective bell housing so that it sits in a perfectly square manner on the objective end cap.

When installing the eyepiece assembly just rotate the central thumbscrew until the eyepieces seat appropriately on the eyepiece guides, at maximum desired extension, and then tighten the internal brass fastener. Repeat, if required, to set the proper focus range. This may take a few tries.

When the binocular is reassembled remove the external guard rings and with the objective housing retaining rings loosely secured view the image. If required, rotate the eccentric rings until the images in your view merge. This is a trial and error process. Remove your eyes and if you feel that eye readjustment is required repeat the process. In addition, in the first instant of viewing, if the images wander or snap together then repeat the process. When satisfied tighten the objective housing retaining rings and replace the external guard rings.You are now good to go.

The above information is copyrighted © by William C. Blunk and Howard Rose Nov. 10, 2008 for individual use only and may not be copied for other than individual use or distributed, either for free or sold, without permission.