Scraper - what is it: purpose and types of tools
Scraper is well known to experts in metalwork. With this tool, you can give a minimum degree of roughness to the surface finish of metal parts., and their geometric parameters - a high degree of accuracy.
Scraping the guides of the rear headstock of the lathe
How is scraping performed
The very word "scraping", which can be translated as "scraping", came to us from Germany. It very accurately corresponds to the essence of the technological operation, which denotes. In the course of performance of such operation from a surface of a detail to scrape off roughnesses, which allows you to make it as smooth as possible.
Shaberi, by means of which such operation is performed, are made of tool steel. The design of this tool consists of a handle four- or triangular in shape and cuts part. To give the working part of the scraper the required degree of hardness (64-66 HRC units), it is subjected to hardening.
Scrapers are made mainly of standard length (20-40 cm), and the width of their cutting edge depends on the type of operation performed. So, rough scraping is performed with a tool, the width of the working part of which is 20-30 mm, for the final this interval is equal to 15-20 mm.
The type of scraping performed also affects that, what value is the angle of sharpening of the tip should be formed on the tool. Locksmiths recommend the use of such sharpening angles:
- 75-90 ° - for roughing;
- 90 ° - for pure scraping;
- 90-100 ° - for finishing operations.
It should be borne in mind, that the sharpening angle of the cutting edge of the scraper is measured relative to its axis.
Sharpening depends on the shape of the working part of the scraper
Geometric parameters of the tool for execution of a scraper are not regulated by any GOST, although many ignorantly try to find such data in the standard number 1465-80. Meanwhile, GOST 1465-80 refers to files and has nothing to do with scrapers. As for the scrapers themselves, in the relevant GOSTs you can find only the requirements for the metal for their manufacture, as well as the rules for accepting such an instrument, belonging to the locksmith group.
Types of tools for performing shabreniya
To date, experts use different types of scrapers, differing from each other in several respects. One such parameter is the shape of the cutting part of the tool, depending on which among scrapers allocate flat, triangular and shaped. Unlike flat and triangular tools, shaped scrapers have a working part, completely repeats the shape of the surface of the workpiece.
Scrapers with different working parts
A triangular scraper with a wooden handle
Tool, the working part of which has several faces, cylindrical and concave surfaces are mainly treated, and flat scrapers successfully cope with the processing of various grooves and grooves. In practice, disc and ring-shaped scrapers are often used. By means of the first processing of details with wide surfaces is carried out, and others carry out scraping of products, having a round shape.
By design, the scrapers are solid and collapsible, one thing- or bilateral. Bilateral scrapers are more durable, which differ from one-sided topics, that they have two working parts, located on both sides of the handle.
The device of the folded scraper
The working part of the scraping tool in its position relative to the handle can be flat or curved. Shaberi, the working part of which has a curved shape, most convenient to use for soft metals, as well as details, having sharp corners.
Relatively recently, only hand scrapers have been used in metalwork, and today many manufacturers offer tools, equipped with a pneumatic or electric drive. You still have to manipulate this tool manually, but this requires much less effort, than when using a hand scraper.
BIAX universal scraper
Areas of application of scrapers
With the help of a scraper, the specialist removes the thinnest layer of metal from the workpiece, the thickness of which can vary within 0,005-0,7 mm, which allows you to bring the degree of surface roughness to the desired level. With the help of such a technological operation, parts are often processed, which will be further connected and moved relative to each other. The most common details, for finishing which different types of scrapers are used, is:
- details of machines and high-precision devices;
- elements of plain bearings;
- various measuring instruments and devices for control operations;
- blades of cutting tools (for their sharpening the so-called nail-neighbor is used).
Scraping - bringing the guides of the lathe caliper
One of the advantages of scrapers - versatility, therefore, their scope is not limited to the above points. These tools are used to perform engraving on the surface of soft materials, process edges of details, remove the old coating. They are also used in cosmetology, with their help manicurists carry out the manipulations.
Scrapers used to solve various problems can be distinguished from each other even by photo, because they have different design and geometric parameters. So, miniature manicure tool is made in the shape of a spatula with a comfortable handle, and devices for scraping dimensional workpieces can be produced in the form of carbide plates. Guess what, that such a plate is a scraper, non-specialist is quite difficult, even if he sees her live, not in the photo. To use this tool, requires a special clamp, is equipped with the convenient handle for performance of metalwork manipulations.
The scraping technology depends on both the size and configuration of the workpiece, and the hardness of the material, of which it is made. Specialist, who is going to perform such a technological operation, must correctly choose the angle of sharpening of the working end of the scraper relative to its axis. This angle when processing different materials should be within the following limits:
- when scraping soft metals - 35-400;
- when processing surfaces of details from steel - 75-900;
- when performing scraping of cast iron and bronze parts - more 900.
Here are some tips for using a scraper tool
That the tool for performance of a scraper served you as long as possible and allowed to receive high-quality surfaces, it is necessary to follow simple recommendations for its operation. The main of these recommendations, Of course, is the right choice of tool.
Many locksmiths have whole sets of scrapers, from which they choose the optimal one for solving a specific technological problem. You can do differently and buy a universal tool with replaceable plates, which are quickly replaced by those needed in a given situation.
Homemade head for scraper plates
It is not necessary to start scraping at once, if on the surface of the part, which needs to be processed, there are large scratches and other defects of considerable size. Such a detail must be subjected to rougher processing in advance, for which you can use a milling machine or other equipment.
Once the surface is prepared ??before scraping, must be found on the details of the site, which should be given special attention. To do this, apply a thin layer of special paint on the test plate and spend on its surface, which is processed. As a result of such simple manipulation, all protrusions on the surface of the workpiece will be painted. From them it is necessary to begin sabrenie. It is necessary to use a test plate with paint repeatedly, after the end of each processing cycle.
Drafts (peel off) scraping is used to remove from the plane of the hardened top layer
To perform scraping, the part is securely fixed in the vise, and large products are processed on site. The tool itself is held with both hands in the middle of the handle and moved towards you. It is very important to maintain the angle of the scraper in relation to the treated surface (it should be close 800).
Starting to scrape, should be borne in mind, that first of all the most convex sites are processed.
