Precision Washer

For my next reel design, I need a washer 5/16 inch OD, 1/8 inch ID, and .010 inch thick. I have had a similar part in past designs, and tried to make it by parting off the thin washer from a drilled rod. This is not a satisfactory method. I had trouble getting the thickness right, and the burr around the center hole was difficult to remove. The problem is that a tiny part is difficult to hold while working.

To solve the thickness problem, I have bought some .010 thick brass shim stock. I start by cutting a triangle of material using tin snips.
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Here the material triangle is resting on part of the fixture in the next photo.

This fixture firmly clamps the triangle while I put in a center hole.
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The best way to make the hole seems to be to plunge a center cutting end mill, going through the hole in the clamp plate.

The next fixture (shown here with the final washer) holds the material by its center hole.
IMG_4478
I first cut the OD using my mill and rotary table, then move to the lathe to file away the burr.

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2 Responses to Precision Washer

  1. simon says:

    Using shim stock is the right way to do it and, depending on how many pieces you need, your little fixtures might be just what the doctor ordered. If, you find that you’re allways making the same size washers though you might want to look at making yourself a washer punch and die set. At the sizes you’re making you can activate the die in an arbor press or even wack it with a rubber mallet.
    http://www.homemodelenginemachinist.com/f13/punch-die-set-14002/
    That link is just to give you an idea what they look like. One can be built much sturdier out of ground O1 plate and some drill rod. I use mine every week to make copper washers for hydraulic fittings and they work great.

  2. dave49 says:

    Simon,
    Thanks for the punch/die link, I did not know where to look.
    But since my requirement is 1 per reel, I will probably stay with the method as posted.
    Dave

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