as to be fitted in the recess of an operation panel 11 thereby to be mounted on the front face of the machine frame 1 a structure for supporting and attaching the operating keyboard 9 on the operation panel 11 includes a first code set consisting of a pin 12 projecting from the keyboard 9 and a hole 13 formed in the operation panel 11 the pin and the hole are positioned for each model such as to snugly fit in with one another while bolts not shown attached to in the operating keyboard 9 are inserted through corresponding holes of the operation panel 11 and secured by nuts not shown so as to fasten the two components 9 and 11 together in addition the operation panel 11 is mounted on the machine frame 1 in this regard a second code set consisting of a pin 14 formed on the operation panel 11 and a hole 15 formed in the machine frame 1 are positioned for each model such as to snugly fit in with one another while screws 16 16 are tightened to fix the two components 11 and 1 numeral 17 denotes a cpu central processing unit circuit plate which is principally composed of control circuits for controlling the stepping motors 7 and 8 the cpu circuit plate 17 is screwed to the back of the operation panel 11 and is electrically connected with the pattern indication circuit plate 10 fig3 of the operating keyboard 9 by a connector 18 numeral 19 designates a control circuit plate for.