Centring, Drilling Counterboring and Countersinking, Reaming and Tapping on the Drilling Machines - Course: Techniques for Machining of Material. Instruction Examples for Practical Vocational Training: Instruction example 1.2. Gib

Centring, Drilling Counterboring and Countersinking, Reaming and Tapping on the Drilling Machines - Course: Techniques for Machining of Material. Instruction Examples for Practical Vocational Training

		(introduction...)
		Introduction
		Instruction example 1.1. Distance piece
		Instruction example 1.2. Gib
		Instruction example 1.3. Cylinder
		Instruction example 1.4. Prismatic guideway
		Instruction example 1.5. Stop

Instruction example 1.2. Gib

This instruction example describes the manufacture of prismatic workpieces with cylindrical through hole and counterbore by means of the techniques of centring, drilling and counterboring. Punch marking (determination of the centre of the hole to be machined by means of the scriber and centre punch) is presupposed.

In case of series production the use of fixtures (positioning of the workpiece in fixed position) is advisable.

Figure

Material

GGL 25 (GG - cast iron, L - lamellar, tensile strength of 25 - 250 MPa)

Dimensions

160 × 40 × 20 (premachined)

Tools

Twist drill of Ø 8.4; piloted counterbore of Ø 8.4 × 13

Measuring and testing means

Vernier caliper, depth gauge

Auxiliaries

Machine vice, drill chuck, taper sleeves, drill drift, parallels, coolant or lubricant

Required previous knowledge

Reading of drawings, measuring and testing, choice of cutting values

Sequence of operations	Remarks
1. Measure rough dimensions.	In case of undersize in length, width, height and shoulder thickness reject workpiece.
2. Clamp workpiece.	Kind of clamping: loose vice clamping, insert parallels. Clamp for size 40 mm. Note: Dead weight of the vice must be heavy enough to avoid distortions, otherwise clamp firmly. Clamping width must be at least 100 mm (if clamping area is smaller, intermediate clamping is necessary). Parallels must lie freely and not allow spot-drilling (width smaller than 6 mm). Press on firmly and clamp centrally.
3. Clamp tool.	Insert drill chuck into boring sleeve, use taper sleeves, if necessary.
4. Set cutting values.
5. Align.	Align vice with clamped workpiece for first centre punch. Keep in central position (with left hand).
6. Drill first through hole of Ø 8,4 mm.	Spot-drill and check for centre (centring is not necessary because of centre punching). Align in case of deviation. Make through hole of Ø 8.4 mm. Drill uniformly with manual feed.
7. Align.	Align for second hole according to working step 5.
8. Drill second through hole of Ø 8.4 mm.	Finish hole according to working step 6.
9. Align.	Align for third hole according to working step 5.
10. Drill third through hole of Ø 8.4 mm,	Finish hole according to working step 6.
11. Clamp tool.	Use drill chuck or taper sleeves (in case of taper shank).
12. Align.	Align vice with clamped work-piece for corresponding axial position between tool pin and work piece hole of Ø 8.4 mm. In doing so, insert pin into workpiece hole. Alignment is made by hand at low speed (approx. 15 r.p.m.).
13. Counterbore-first counter-bore of p 13 mm.	Choose the speed n to be less than 40 r.p.m. (multiple-edge tool). Guide the feed by hand and uniformly. Pay attention to size (counterbore depth of 8 mm).
14. Align.	Align for second counterbore according to working step 12.
14. Counterbore-second counterbore of Ø 13 mm.	Finish counterbore according to working step 13.
16. Align.	Align for third counterbore according to working step 12.
17. Counterbore third counter-bore of Ø 13 mm.	Finish counterbore according to working step 13.
18. Deburr, make dimensional inspection and visual check.	Deburr external contours of the Ø 8.4 mm and Ø 13 mm holes with suitable means (countersink, triangular scraper, twist drill). Surface inspection - pay attention to centre-distance displacement between Ø 8.4 mm and Ø 13 mm holes.

Gib