מסכת כלים

פרק כט משנה ד

חוט מאזנים

The cord of a balance (this was the cord by which one suspended a balance scale; the scale had a beam at either end of which was suspended a pan; and the cord was attached to the middle of the beam and functioned as the scale's fulcrum),

of goldsmiths

and of weighers of good purple wool,

three fingers (of the cord was considered attached to the scale for the purpose of tumah and taharah).

The handle of the hatchet from the back,

three fingers. (A person holds the wooden handle of the hatchet one handbreadth below its metal head; the "back" of the handle referred to here, according to most interpretations, refers to the length of the handle that extends below the person's hand.  Thus, the hatchet handle could be two handbreadths plus three fingerbreadths long; a handbreadth in the "front" going from the hatchet's metal head to its user's hand, the handbreadth held by the user's hand, and three fingerbreadths below that.)

Rabbi Yosi says

(if the back of the handle extends) a handbreadth (then the entire handle is too long to use properly, and) it is tahor. 

חוט מאזנים של חנונים

The cord of a balance of shopkeepers,

(or) of householders

a handbreadth  (of the cord was considered attached to the scale for the purpose of tumah and tahrah).

The handle of a hatchet from in front

is a handbreadth (see the explanation given in the previous mishnah regarding the "back" of the handle).

The remnant of a compass handle (this refers to a drawing compass used by carpenters to scribe a circle; it was comprised of two legs joined together with a hinge at one of their ends, and at their other ends were metal points; the handle is the part the extends from its top by the hinge and was used to hold the compass while using it to draw),

a handbreadth (i.e. if the handle broke, a handbreadth must remain for it to be considered an attachment to the compass for the purposes of tumah and taharah).

The handle of a chisel

of stone engravers,

(must be) a handbreadth (to be considered an attachment for the purposes of tumah and taharah).