N58 Ground Casing Mandrels
These are solid steel mandrels used to remove dents from valve casings and to straighten casings if they are sprung. Easier, faster and more safe to use than reamers and almost impossible to damage a casing using these mandrels. They are not adjustable, so you must know the size you need or the brand and model of the instrument. Precision measuring is helpful.
The recommended procedure for use:
▪Mount the instrument on a wood assembly mandrel in a vise.
▪Thoroughly clean the casings with F7 Premiere Metal Polish and Z10 Cold Cleaner
▪Select the proper size mandrel for the instrument and insert it all the way into the casing.
▪When ready to hit the mandrel, STRIKE SHARPLY. It is the quantity of hits that raises the dents and straightens casings, not the force used. Strike firmly-not hard.
▪Use the side of a F5 rawhide mallet and strike the small end of the mandrel with many small and repeated taps. Use sideways and up and down hits. Aim at port intersections.
ORDER THE EXACT SIZE. THESE MANDRELS ARE NOT ADJUSTABLE
TO ORDER THE CORRECT SIZE—
Order by the O.D. of the piston. Example: Yamaha .664”. Due to the differences in manufacturing over the years it is highly RECOMMENDED to measure the valve piston.