Scraping of plane surfaces - Course: Technique for Manual Working of Materials. Instruction Examples for Practical Vocational Training: Instruction example 6.5. Lathe bed

Scraping of plane surfaces - Course: Technique for Manual Working of Materials. Instruction Examples for Practical Vocational Training

		(introduction...)
		Introduction
		Instruction example 6.1. V-block
		Instruction example 6.2. Steel straight-edge
		Instruction example 6.3. Try square
		Instruction example 6.4. Centre square
		Instruction example 6.5. Lathe bed

Instruction example 6.5. Lathe bed

Practise planing of lathe bed

Material

Figure

lathe bed (base)

Hand tools

Wide and narrow flat scraper

Measuring and testing tools

Water-level (bubble level), measuring microscope, planing straight-edge, surface plate, if necessary, mating machine slide, locksmith’s hammer

Accessories

Measuring bridge, long bars (lever), various steel wedges, measuring wire Ø 0.1 mm with mounting, checking ink (black, red), inking block

Required previous knowledge

Testing, measuring

Sequence of operations		Comments

1. Arrange workplace Prepare working material		- Check for completeness

2. Remove planing marks from slideway by means of wide flat scraper (powerful rough-scraping)		- Work in long powerful strokes at right angles to planing direction until planing traces disappear

3. Align lathe bed (6) by water-level (1) - place a suitable measuring bridge (2) onto lathe bed; check cross and longitudinal direction by water-level without displacing the measuring bridge; to correct position, arrange steel wedges		- Guideways must exactly lie in parallel and horizontally - Lift lathe bed by means of levers, mount steel wedges

4. Check plane ways in order to realize variations from the horizontal - mark variations at the base		- Move measuring bridge and level in longitudinal direction, measure in longitudinal and cross direction!

5. Check lateral bendings (variations) of guideways:		- Place front and end in same position to guides!
	- tension a steel wire (4) of 0.1 mm dia. along the bed centre (rigid mounting (5!))	- Cross hairs matches the wire
	- mount measuring microscope (3) onto the measuring bridge and adjust to wire	- Read dimension of variation from microscope
	- move measuring bridge with measuring microscope along the bed - in case of variations the microscopic image is laterally displaced from wire
	- Mark variation point at the base

6. Remove measuring wire and measuring bridge, rub planing straight-edge or surface plate with a wafer-thin layer of black or red checking ink and slowly rub over the guideways (finished machine slide can also be used for checking)		- Avoid oil blotches on guideways!

7. Take off checking device and rough-scrape the entire surface having contact points - subsequently, remove variations (found in operations No. 4 and No. 5)		- Change scraping and checking until even contact points are reached!

8. Spot-scrape contact points in changing direction by means of narrow scraper until you can see enough contact points after checking		- First begin with spot-scraping when you had sufficiently rough-scraped!

9. Final check		- Function test with machine slide

Figure