Ion exchange was carried out on a lithium-doped fluorophlogopite machinable glassceramic with composition, in wt%, 52.2 SiO2, 14.0 Al2O3, 14.2 MgO, 12.5 MgF2, 1.4 Li2O, and 5.7 Na2O, to study the strengthening effect. The crystalline phases after annealings were Na-fluorophlogopite and betaspodumene, with a volume fraction of about 2:1. Ion exchange of Li by K in the glassceramic at 770° C for 4 h improved 2.1 to 2.3 times the three point bending strength (TPBS). Hence strong machinable ceramic with TPBS of greater than 300 MPa can be made. Ion exchange increases 100% electrical resistivity and improves 21% chemical stability, due to a surface layer of about 100 micrometer enriched with K.