7x10 Repairs & Modifications


BROKEN MOTOR DRIVE GEAR
02/18/2000 I was making three brass nuts for the Steady Rest when I heard a sickening THUMP from the lathe. UHHH OWWW.... I thought. Hmm the motor is going but the chuck stopped spinning. GREAT! I broke the keyseat on the Motor Drive Gear. When I looked at it to figure out how bad it was, this is what I saw.

Plastic Drive Gear
in three pieces

Plastic Drive Gear
Notice the air bubble
on the Left side.

Another air bubble.

Air bubble on main
piece. Better Lighting.

Notice the clean
fracture of the piece.

Plastic Drive Gear after
carefully using crazy glue.
 I started thinking.... Lathe down for a couple weeks to a couple months until gear ships in from CHINA... NOOOOO..... I'll make one!! After a couple minuites carefully gluing the peces back together so I could measure the gear. I sat down with Visio and made a drawing of the gear. I took a 1.5" disk of t6061 I had in the CHUNK pile. mounted it in the 3-jaw. Placed the glued gear on the motor. Crossed my fingers & turned the dish down to the proper size. Then mounted it it the 5C indexer. PROBLEM #1 - drive gear has 17 teeth. Lets see 360/17=21.1764 Degrees. OOOps.. Well 360/18 is 20 Degrees, So 18 teeth it is. UH OH, that changed the pitch diameter beause the tooth size cant change much without having the belt jump a tooth. Back to calculating.. I finally came up with numbers that looked correct. So I fired up the mill with the indexer mounted. cut 18 slots on the blank about .050" deep just in case. I then cut a keyway with a 5/32" endmill and tried the gear & belt together. It fit for a couple turns with out having a tooth fall out of sync. So I mounted it on the motor, Crossed my fingers and spun up the 7x10 at min. Not a sound out of place. So I spun it up to max no odd sounds. So if you break a gear have heart. If I can make one YOU CAN TOO!!!

New Drive Gear Oblique View.

New Drive Gear Rear View.

New Drive Gear Front and Above.

New Drive Gear TOP View.

New Drive Geari Side View.

New Drive Gear Head on View.


This page last updated 04/20/2000

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For more information email me at:
pth3k@virginia.edu


All above images Copyright (c)1999
Ty Hoeffer