The Jig Borer and Jig Grinder Section 13

Jig Borer Developed primarily to overcome problem of accurately locating and producing holes in precise locations Very important tool before age of computer-controlled machining centers Repeatedly position holes to within 20 millionths of an inch Has reduced use of jig borers to point, no longer manufactured

The Jig Borer Unit 73

Objectives Identify and state the purposes of the main operative parts of a jig borer Use various accessories and work-holding devices for setting up and boring holes

Jig Borer

Jig Borer Parts Variable pitch pulley drive Quill housing Operated by pushing button on electric control panel to provide spindle with variable speed range from 60 to 2250 r/min Quill housing Can be raised or lowered to accommodate various sizes of work if first quill housing clamp loosened and quill housing vertical positioning handle turned

Jig Borer Parts Brake lever Rapid feed handwheel Friction clutch Manually operated to stop rotation of spindle Rapid feed handwheel Allows spindle to be raised or lowered rapidly by hand Friction clutch May be used to engage or disengage handfeed of the quill

Jig Borer Parts Graduated downfeed dial Reads distance of vertical spindle travel Vernier scale: thousands of an inch Adjustable stop for hole depths Adjusted to allow spindle to move to predetermined depth for drilling or boring hole Spindle Revolves inside quill and supplies drive for cutting tools

Jig Borer Parts Reference scales Graduated dials Longitudinal and crossfeed Serve as reference points in moving table into position Graduated dials Allow table to be positioned quickly and accurately Uses micro-setting verniers on longitudinal and crossfeed screw handwheels (within .0001 in.)

To Insert Shanks in the Spindle Taper shank on tool being inserted and hole in spindle must be perfectly clean Protect taper shanks from finger perspiration Avoid inserting shanks too tightly, especially when spindle warmer than inserted shank When removing or replacing tools, apply brake firmly with left hand Wrench should be held carefully

Accessories and Small Tools Wide variety of accessories enable jig borer to meet three basic requirements Accuracy, versatility, and productivity Drilling accessories Key-type and keyless chuck hold smaller straight-shank spotting tools, drills and reamers Collets used to hold larger tools Setscrew in collet tightened against flat on tool shank eliminating twisting and scuffing

Single-Point Boring Solid boring bar Swivel block boring chuck Fitted with adjusting screw that advances toolbit over relatively short range Rigid, so useful in boring deep holes Swivel block boring chuck Provides greater range of adjustment Better visibility to operator while boring Disadvantage: graduations for adjusting tool travel vary depending on length of cutting tool

Single-Point Boring Offset boring chuck DeVlieg microbore boring bar Permits cutting tool to be moved outward at 90º to spindle axis of machine Possible to perform operations such as boring, counterboring, facing, undercutting and machining outside diameters DeVlieg microbore boring bar Equipped with micrometer vernier scale

More Tools Single-Point Boring Tools Collets and chucks Most accurate method of generating accurate hole location Wide variety of cutting tools High-speed steel with brazed, cemented-carbide tips Collets and chucks Assortment available for jig borer spindle to hold straight-shank spotting tools, drills, and precision end-cutting reamers

Reamers Used in jig boring for bringing hole to size quickly Rose (fluted) reamer Used after hole bored and provides accurate method of sizing hole (remove .001-.003 in) Precision end-cutting reamers Provide fastest method of locating and sizing holes to within ±.0005 in Acts as boring tool and reamer