Keilim 21:1-2
Keilim 21:1
Regarding a loom, if one touches the upper or lower beam, the heddles, the sley, thread that is drawn over purple (to protect this expensive material) or hanging thread that one will not be drawing back, he remains ritually clean (since these are not considered attachments of the material). If he touches the woof, the standing warp, double thread that is drawn over purple (which was not subsequently removed) or hanging thread that one plans to draw back, he is rendered unclean (because these are considered attachments of the material). If one touches wool on the distaff or spool, he remains clean. If one touches the spindle weight before it’s exposed (from being covered with yarn), he is rendered unclean; after it’s exposed, he remains clean.
Keilim 21:2
Regarding a ritually-unclean plow, if one touches the yoke, its connecting pin, its collar cushioning or its ropes, even while they’re being used, he remains ritually clean (because these are not considered attachments to the plow). If he touches the handle, the “knee” (the part of the plow that drags on the ground) or the rudder, he is rendered unclean (because these are considered attachments to the plow). If he touches the metal ring, the side blades or the plowshare, he is rendered unclean; Rabbi Yehuda says that one remains clean if he touches the side blades because their purpose is just to loosen the soil (so they’re removed when not in use and therefore not an inherent part of the plow).