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Thread: Focus adjusters for M9 diode mounts.

  1. #1
    Join Date
    Mar 2006
    Posts
    2,478

    Default Focus adjusters for M9 diode mounts.

    DIY Focussing adjusters for Dave's barrels:
    (Should work with others that use a similar form).

    The point of this is to allow full view of the beam during the adjustment, as it's much quicker to do it that way.

    Stuff:
    1mm thick straight piano wire.
    Brass modelling tube, 9/16'' OD, 1/4'' ID.
    Masking tape, an inch wide.
    Cyanoacrylate glue. (Superglue, must be low viscosity.)
    Adhesive lined polyolefin heatshrink tubing, 9 or 10mm unshrunk bore.

    Tools:
    Small hand-operated pipe cutter.
    Fast modelling drill with fine cutting disk.
    Small 'mole' grip, or forceps, something that will stay gripped when you let it go.
    Oven set to 90°C.
    Wipes to degrease your fingers and thumbs before beginning.

    Method:
    Cut a 20mm length of brass tube, and a 20mm length of heatshrink tubing. Be precise. If the heatshrink is 1mm too long, it will walk off one end of the tube when you try to shrink it!

    Don't clean up the tube end. If it were ground flat, it might reflect light back into a laser diode while adjusting it. The pipe cutter will leave the end bevelled, with a rough diffusing surface, so leave it that way. Light deburring with emery paper is all it needs.

    Grind the end of the stock piano wire against the side of the cutting disk at moderate speed to make it flat, then gently grind the edge to round and smooth the end, rotating it and applying very gentle contact pressure with the disk. Cut the end off at exactly 20mm total length. Repeat for two parts in total.

    Pull back the masking tape on the roll so it lies back on itself, edges aligned parallel, exposing the sticky side to a length about an inch or so, and stick the 20mm length of brass tubing onto it with one end flush with the tape's edge.

    Lay one piano wire pin beside it opposite the loose end of the tape, with its rounded end protruding beyond the edge of the tape by 1.5~2.0mm. Pull back the tape to expose more of it at the same time as you lift the tube and rotate it to bind the pin tightly to the side of the tube, then cut the loose end of the tape off as close to the tube as you can get.

    Rotate the tube on the tape until you are in position to place the second pin diametrically opposite the first, rounded end protruding as with the first one. This doesn't have to be absolutely precise, but both ends should match closely. Bind it with more tape, cutting the tape just before it begins to overlap the starting point.

    Tweak the wires into accurate position and alignment using edges of fingernails to press the tape beside the pin, opposite to the direction you want to move it to.

    Once it's set accurately, use a drop of superglue at each end of each pin, letting capillary action draw the glue into the gaps under the tape.

    Place the tube on end, prongs down, on the jaws of the mole grips or forceps, and clamp gently so the tube end is flush with the jaws. Place the 20mm length of heatshrink over the tube and bake the lot in the oven till tender, then allow to cool before touching it again. (To protect the heatshrink). Trim off the glue and any overhanging heatshrink from the top end of the tube. Also, cut back the prong end's heatshrink tubing a bit to get better visibility for what happens at the business end when adjusting. Keep laser power low while using this.
    Attached Thumbnails Attached Thumbnails Laser Focus Adjuster, 1.jpg  

    Laser Focus Adjuster, 2.jpg  

    Last edited by The_Doctor; 10-26-2013 at 10:18.

  2. #2
    Join Date
    Dec 2007
    Location
    Nottingham, UK
    Posts
    2,845

    Default

    Nice!

    I've been using a slightly modified Thorlab SPW308 for the last 18 months or so.
    It just requires turning 1mm off of the end - perfect fit.
    - There is no such word as "can't" -
    - 60% of the time it works every time -

  3. #3
    Join Date
    Mar 2006
    Posts
    2,478

    Default

    Thanks for the vote of confidence. Mind you, I reckon that Swann Morton scalpel makes it look posher than it really is.
    I ought to have asked what other people are using, but I love inventing my own stuff. Habits of little loot...

  4. #4
    Join Date
    Jun 2010
    Location
    Australia
    Posts
    3,734

    Default

    Nice, I have been cursing for too long, time to build one! Hell, 2. 1 for the bench, 1 for the gig tool kit.
    This space for rent.

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