b'\x1b\x1a\x19 \x1f\x18\x1d\x17\x16 Machinists CornerMILLING FORCESBy Brandt TaylorI nmypreviouscolumn,Iwent through how to hold an 11"-dia.-by-2"-thick workpiece on a 6" mill-ing vise. This column will showcase a little math to estimate forces in-volved with aggressive metal re-moval. In this way, it is possible to machine economically and safely. The drawing shows the problem.This 190-cubic-inch piece of stock is going to turn into a 75-cubic-inch finished part. To begin, 40 cubic inches will be removed from the outside diameter above where the part is clamped in the vise. When roughing, I use corncob endmills that have little bumps on the flutes, but the math that I use is adaptable to whatever tools you like.In the drawing, when the tool moves laterally into the workpiece or moves radially around the work-piece center, it will make tangential cutting force CF, which will resolve itself into a horizontal and a vertical component determined by angle a. At the tool, that produces vertical force VFT, which is CF tan a, or CF times a/d. The important thing to consider is the vertical force at the vise jaw clamping surface VFJ, which is higher than VFT because of me- B. Taylorchanics. VFJ equals VFT times d/d-c. The project is shown.If VFJ gets close to the vertical holding power of the clamping sur- so thats 1,800 lbs. per surface. workpiece with the size and num-face, then there will be trouble. InCutting speed and chip thicknessber of the chips will give a useful the article about the vise jaws forare best determined the normal waynumber.this part, it was determined thatto maximize tool economy, but theCF = TGNHJR/W3,600 lbs. of vertical force could bedepth and width of cut can be ad- Whereresisted by the steel back jaw hold- justed for good, safe metal removal. T=tensilestrengthofthe ing this aluminum part. There areDetermining CF is the key to theworkpiecetwo clamping surfaces on this jaw,puzzle. The tensile strength of theG = width of the chips (for some 12SEPTEMBER 2022MachinistCorner.indd 12 8/16/22 11:34 AM'