segments could be constructed of cut steel plate with a web such as shown in 16 39 also of cut steel plate bent and welded to form a right angle with the semicircular segment an abrasive saw shown generally at 22 in fig4 is pivotally attached to a carriage means 20 which is adapted to engage and ride upon track means 16 the carriage 20 shown in cross section in fig5 comprises an upper support bracket 36 which carries a wear pad 34 engaging the upper surface of track 16 pad 34 is for example a low friction polymer such as polytetrafluoroethylene commonly sold under the trademark teflon or equivalent polymer materials alternatively a metal wear pad may be utilized also attached to the upper support bracket 36 is an upper guide roller 46 which is adjustably mounted in adjustment slot 48 of upper support bracket 36 roller 46 may be adjusted to provide the proper angular orientation of the carriage 20 with respect to the track 16 extending upwardly from the upper surface of upper support bracket 36 is saw pivot 32 which pivotally mounts saw arm 30 web 33 extends downwardly from the upper bracket 36 and engages lower bracket 38 and fasteners 40 fasteners 40 are readily removed to permit the entire saw support assembly to be dismounted from track 16 as shown by dotted lines in fig5 the lower bracket 38 carries.