The Jig Borer and Jig Grinder

1. The Jig Borer and Jig Grinder Section 13

2. 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

3. The Jig Borer Unit 73

4. 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

5. Jig Borer

6. Jig Borer Parts • Variable pitch pulley drive • 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

7. Jig Borer Parts • Brake lever • 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

8. 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

9. Jig Borer Parts • Reference scales • 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.)

10. 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

11. 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

12. Single-Point Boring • Solid boring bar • 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

13. Single-Point Boring • Offset boring chuck • 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

14. More Tools • Single-Point Boring Tools • 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

15. 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