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 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

7. 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

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 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 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 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

13. 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

14. 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

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 in)
Precision end-cutting reamers
Provide fastest method of locating and sizing holes to within ±.0005 in
Acts as boring tool and reamer