Determining a Pinch Roller diameter
This page is to illustrate and hopefully help you determine the correct size
pinch roller for your reel to reel. The first picture is a typical unit showing
the pinch roller on the machine. I realize most roller / capstan areas are not
this easy to get at, but I used this one for clearity. This roller comes
off by unscrewing the center metal cover. Yours may vary.
First remove the pinch roller as showned in Picture #2 It is hard to see the
pinch roller shaft in this picture as it is sticking straight up toward the camera.
Next measure the distance between the Pinch roller shaft and the capstan shaft.
(Picture #3)The recorder selector handle must be in the play mode. If your unit
is push button, plug it in and then push play. The pinch roller shaft will move
forward as if it was playing.
Take that measurment multiply times 2
Step # 2
|Distance between the 2 shafts = .538
Now measure the diameter of the Pinch roller shaft , as in the picture above.
Add that diminsion to the total in step #2.
Shaft diameter = .232
Distance between 2 shafts times 2 = 1.076
This is the last and final step
OK , If I made the pinch roller a diameter of 1.308, it is only big enough to
barely touch the capstan shaft, and there would be no pressure against the tape.
So we have to give it some crush or pressure against the shaft to hold the tape.
Take the 1.308 and add .125 to it, that equals 1/8 inch to the total diamater
or 1/16 of an inch on each side, you will now have 1/16 inch crush, or pressure
against the capstan shaft. The .125 is not an exact number. It can vary plus or
Total from above = 1.308
Amount of total crush = .125
This is the approximate diameter the 1.433
roller should be to fit your machine.