The ornamental design for a filterthreadconverter, as shown and described.
FIG. 1 is a top isometric view of a filter thread converter according to an embodiment of the invention;
FIG. 2 is a top plan view of the filter thread converter of FIG. 1;
FIG. 3 is a bottom view of the filter thread converter of FIG. 1; and,
FIG. 4 is a side view of the filter thread converter of FIG. 1, the right and left sides begin identical.
The broken line showing of parts of the drawings is included for the purpose of illustrating use and environment and forms no part of the claimed design.