DIY repair of caliper guides on a lathe

In detail: do-it-yourself repair of caliper guides on a lathe from a real master for the site my.housecope.com.

During the overhaul of the lathe, the accuracy of the bed guides is restored. When choosing a restoration method, they are guided by the degree of their wear. When the error does not exceed 0.15 mm over a length of 1000 mm, then they are restored by scraping. With greater wear, they resort to mechanical processing: grinding or planing. When the guides are hardened, the main repair method is grinding.

Scraping of guides or scraping with subsequent lapping is still the most effective way to restore their geometric, technical accuracy. And now this method is often used, for many decades, demonstrating an excellent result of the repair of the bed. First of all, it is necessary to inspect the condition of the guides, to determine the degree of their wear. The place where the wear is minimal is taken as the base level, and the measurement data are entered into the table, on the basis of which the repair will be carried out. In a lathe, the location of the tailstock is most often taken as the base surface, which practically does not wear out during the operation of the equipment. The method includes the following steps:

installation of the machine bed on a rigid base (repair stand), the longitudinal and transverse position of the bed should be set exactly in the horizontal plane with wedges, shoes or using jacks;
after the completion of the preparatory work, a rough (preliminary) scraping is performed with a scraper working width of 20-25 mm, while the length of the strokes on the surface of more than 10 mm is maintained and 4-6 spots are achieved when testing for paint in squares of 25 × 25 mm. This achieves a breakdown of large spots into smaller ones;
semi-finishing scraping is performed with a 12-16 mm scraper, strokes 5-10 mm long until 8-15 spots per square are reached;
finishing (finishing) scraping is performed with a scraper 5-10 mm wide and 3-5 mm strokes long to achieve 20-25 spots in a square.

Video (click to play).

Since the guides of the lathe bed are quite long, processing is carried out according to beacons with a breakdown of the total length into sections. The first beacon is always the place of maximum production. At a distance less than the length of the straightedge, the second beacon, located in the same plane with the first, is scraped from the first beacon. Then the entire surface between the beacons is scrubbed, followed by a transition to an adjacent area. A ruler with paint should be applied periodically to assess the condition of the guides and the quality of work.

Watch the video of rough scraping

The unhardened parts of the lathe guides are subjected to such processing, the method guarantees the achievement of a high surface accuracy (0.002 mm per 1000 mm length). Formed after scraping, the smallest holes are able to hold well and evenly distribute the lubricant. The quality of scraping depends entirely on the professionalism of the worker.

It is not always possible to use continuous planing or longitudinal milling machines for repairs due to the large length of the lathe bed. In this case, the bed guides are restored using a portable device with a grinding head, which is installed directly on the equipment bed.

Repairs can be carried out on site, without removing the machine from the foundation. This method provides high accuracy of repair, low surface roughness, it is also indispensable when processing a hardened surface.This method is many times superior in productivity to scraping, but experts still prefer finishing planing. Image - DIY repair of caliper guides on a lathe

This method is less tedious than scraping and less expensive sanding. For example, the average repair time for machine guides is:

scraping: about 35 hours;
by grinding with a special abrasive head: 8-10 hours;
finishing planing: 4-5 hours.

When wear is more than 0.15 mm, manual scraping is replaced by machining on a planer with a centralized method of organizing repairs in a repair shop or at a specialized enterprise. The reason is simple, you will have to remove the bed from the foundation and carry out installation and alignment on the rigid table of the planer.

Planing bed guides

At the first stage, a test planing is performed once to obtain a base surface, which will allow determining the deviations along the entire length of the bed. To do this, the cutter is alternately brought to the most worn surfaces and the metal layer is removed until the wear is eliminated. Finish planing is carried out in at least two passes with fine wide carbide cutters. The last pass is performed with a cutting depth of less than 0.05 mm, constantly wetting the cutter and the surface of the guides with kerosene. When the wear exceeds 0.4-0.5 mm, the guides are subjected to rough and fine planing. The main disadvantage of this repair method is the considerable time spent on dismantling the bed, transporting it, installing the bed on the planer table, aligning and removing the restored bed.

When machining by cutting a flat prismatic surface of the guides, tiny metal particles of various sizes and shapes are pulled out of the bed solid. Furrows, grooves appear on the surface, forming a rough surface. Therefore, sometimes after machining, scraping or vibration rolling is indispensable. This increases the strength of the guides due to plastic deformation (changes in the structure of the material). Vibration rolls achieve smoothing of microroughnesses and irregularities by translational movement along and across the axis with specially processed balls or rollers.

Repair of lathe guides by one of the described methods is an element of complex work related to the restoration of full operability and accuracy of metal-cutting equipment. But do not forget that the quality of repairs with a minimum period of its implementation depends significantly on the degree of preparation of the machine for repair and the qualifications of the locksmith.If you find an error, please select a piece of text and press Ctrl + Enter.Scribing machine guides is one of the most effective ways to restore the geometric and technical parameters of a given unit of turning and other units. It is used very often and shows excellent repair results.Any specialist knows that the implementation of repairs of machines used in various enterprises, according to a schedule drawn up in advance, is considered a very important procedure. When carrying out scheduled repairs, various mechanisms of the processing units are restored, including the guide beds.Also, the restoration of the guides may be required outside of the schedule if they require immediate repair. The amount of their wear is determined by a special method, which we will describe. Inspection of the condition of the guides is carried out using probes and a control ruler. The length of the latter is always chosen so that it is at least 2/3 of the extent of the surface to be checked. Image - DIY repair of caliper guides on a lathe

The scheme for establishing the amount of wear is as follows:

the surface of the node of interest to us is cleaned in order to remove serious seizures and nicks from it;
the ruler is placed on the guide and the gap between them is measured using probes (measurements are taken every 30-50 centimeters along the entire length of the machine element).

The place where the gap is maximized is defined as the area where there is a maximum change in the straightness of the guide (that is, there is obvious wear). Next, the next stage of verification is carried out, which makes it possible to establish the flatness of the guide. This is done like this:

a ruler is placed on tiles of the same geometric parameters;
with the help of probes, the distance between the measuring tool and the investigated surface is determined.

A similar operation is performed at 2-3 points along the length, and in different directions. Experienced technicians make verification even easier. They take small sheets of very thin paper (for example, cigarette paper, the thickness of which does not exceed 0.02 millimeters), lay them on guides in several areas, and then press them with a ruler.

Further, from under the measuring device, these leaves are pulled out one by one. When the straightness of the part is not broken, you can only break off the ends of the pieces of paper, but not pull them out. The condition of the horizontal guides is verified using a level and a bridge:

they are placed on that part of the bed that visually seems to be as worn out as possible (in such a section, the bubble in the level will deviate in different directions at approximately the same distance);
moving the measuring instruments to the adjacent zone, where the deviation of the bubble is noted, entering the reading in the graph-table;
then move the bridge further and record the result obtained again.

Based on the table, it is subsequently easy to determine where exactly the wear occurred.

The bed is placed on a hard floor covering or on a special stand, after which the level is examined in the longitudinal direction (the above-described check is carried out), and then in the transverse direction. Using wedges or shoes, they adjust the position of the bed as accurately as possible.It can also be placed on the jack bolts. In this case, the adjustment of the position of the bed will be very simple, you just need to lower or raise it by screwing or unscrewing the bolts. The operation of giving the bed the correct position is continued until the bubble in the level is fixed at the zero mark. Image - DIY repair of caliper guides on a lathe

After completing the alignment, they are determined with the base surface. It will serve as a reference for tracking the parallelism of the restored guides. When it comes to a lathe, those guides that go under the headstock (rear) are most often chosen as the base ones. Practice shows that it is they who wear out the least during the operation of the equipment. It is advisable to pre-trim the selected as the main guides. This will remove minor wear and tear.

After that, you can start scraping the bed, constantly checking the parallelism of the machined surfaces. In some cases, an indicator is used to check the curvature (spiral) of the restored element. But its use is currently recognized as unreliable, due to the deviation (up to 0.01 millimeter) of the base guides from the horizontal. Such a deviation will give a considerable calculation error, which will be the higher, the longer the holder of the verification indicator has.

Note the fact that the parallelism of the guides under the headstock in relation to the mounting planes of the travel roller and screw, as well as the feed box, is often violated. Deviations from parallelism become the greater, the more planned repairs the unit has undergone. Each time, the repairmen have to spend a lot of time assembling the equipment, since the process of fitting the designated roller, screw and feed box to the place is really laborious and complicated.

After completing the preparation of all surfaces, proceed to scraping the guides. In the process of performing the procedure, their spiral twist and parallelism are constantly monitored.

The scribing of specific surfaces is done in a specific sequence. It can be different for each machine, so we will provide a flow chart for performing this procedure for a conventional screw-cutting lathe (for example, for a 1E61PM machine). In this case, the order of scraping the machine guides is such that first, as you understand, the guides for the headstock (back) are processed, and then the following guides: Image - DIY repair of caliper guides on a lathe

Under the clamping strips and directly under the carriage. Deviations from parallelism along the length of more than 15 microns are not allowed.
Caliper (transverse). In straightness, the error is possible up to 10 microns, in parallelism - up to 15 microns (indicators are controlled by a verification bridge and a surface plate).
Carriages (counter guides). During work, make sure that the difference in parallelism between the screw axis and the guides does not exceed 35 microns, using a triangular ruler.
Carriages (longitudinal guides). If these elements of the unit are worn out badly enough, it is imperative to use antifriction compounds to restore them. At the described stage of work, it is important to achieve adequate alignment of the shaft (running) and its landing zone, the reliability of the engagement of the longitudinal movement rack with the rack gear, the perpendicularity of the spindle axis and the movement of the caliper in the transverse direction.

In the future, restoration is carried out using the anti-friction composition of the tailstock guides. The purpose of these procedures is to achieve:

parallelism of the bed guides and the quill axis (at a length of 20 cm, an error of up to 30 microns is possible);
the alignment of the hole of the quill and the spindle (in the horizontal plane, permissible deviations at a length of 30 cm are 10 microns, in the vertical plane - 30 microns).

In metal work, for the manufacture of cylindrical (conical) parts, a lathe is used. There are many models of this production device, and they all share almost the same layout of similar assemblies and parts. One of these is the machine support.Homemade latheFor a better understanding of the functions that the lathe support performs, you can consider its operation using the example of the common 16k20 model. After reviewing this information, it is possible that some home craftsmen will have an idea to create a homemade lathe with their own hands for carrying out work on metal.This is a rather complex node of a metal lathe, despite its apparent simplicity. From how correctly it is made, installed, adjusted - the quality of the future part depends, and the amount of time it took to make it.
to the menu ↑The support placed on the 16k20 machine can move in the following directions:

transverse - perpendicular to the axis of the rotating workpiece for deepening into it;

longitudinal - the cutting tool moves along the surface of the workpiece to remove an excess layer of material or turn the thread;

inclined - to expand access to the surface of the workpiece at the desired angle.

The support for the 16k20 machine is located on the lower slide, which move along the guides fixed on the bed, and thus longitudinal movement occurs. The movement is set by the rotation of the screw, which converts the rotational force into translational movement. Image - DIY repair of caliper guides on a lathe

The lathe support is designed to hold and move the cutting tool

On the lower slide, the caliper also moves transversely, but along separate guides (transverse slide) located perpendicular to the axis of rotation of the part.

A rotary plate is attached to the cross slide, with a special nut, on which there are guides for the movement of the upper slide. You can set the movement of the upper slide with a swivel screw.

The rotation of the upper slide in the horizontal plane occurs simultaneously with the plate. Thus, the installation of the cutting tool occurs at a given angle to the rotating part.

The machine is equipped with a cutting head (tool holder), which is fixed on the upper slide with special bolts and a separate handle. The movement of the caliper occurs along the lead screw, which is located under the travel shaft. This feed is done manually.

In the process of work on the 16k20 machine, there is natural wear and tear, loosening, loosening of the caliper fasteners. This is a natural process and its consequences must be constantly monitored through regular adjustments and adjustments.

The main components of the lathe

The following adjustments are made on the support of the 16k20 machine:

During the transverse and longitudinal movement of the support of the 16k20 machine tool along the slide, wear of the screw and their working surface occurs due to constant friction.

The presence of such free space leads to uneven movement of the caliper, jamming, oscillation during lateral loads that arise. Excessive clearance is removed using wedges, with which the carriage is pressed against the guides.
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Backlash appears in the helical gear. You can get rid of it without disassembly. using the fixing screw, which is located on this caliper movement device.
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During long-term work on metal on the 16k20 machine, wear and clogging of the oil seals occur, which are located at the ends of the carriage protrusion. Visually, this is determined when dirty stripes appear during the longitudinal movement of the caliper.

Lathe front cover with oil seal

In order to eliminate this phenomenon without disassembling the unit, it is necessary to rinse the felt padding and soak it with machine oil. If the worn out oil seals are completely unusable, they should be replaced with new ones.
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This lathe device wears out over time under constant significant loads in metal work.

Significant wear is easily identified by the surface condition of the guide slide. Small depressions may appear on them, which will prevent the free movement of the caliper in a given direction.

With timely regular maintenance, such repairs may not be necessary, but in the event of a defect of this kind repair should be done, and in case of severe wear - replacement.

The 16K20 caliper quite often requires carriage repair, which consists in restoring the lower guides that interact with the bed guides. Particular attention is required to maintain a stable perpendicular position of the carriage.

When repairing the caliper, it is necessary to check on both planes using a building level.
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The turning device with which metal work is done can be very simple. You can assemble a homemade machine with your own hands almost from improvised means, which are taken from mechanisms that have fallen into disrepair.

Homemade lathe

You should start with a metal frame welded from a channel, which will be the bed. From the left edge, a fixed front headstock is fixed on it, and a support is installed on the right. A self-made machine, made by hand, provides for a ready-made spindle with a chuck or faceplate.

The spindle receives torque from the electric motor through a V-belt transmission.

When the machine is working for metal, it is impossible to hold the cutter with your own hands (in contrast to working with wood), therefore, you will need a support that will move longitudinally.A tool holder is installed on it with the possibility of alternating it transversely to the direction of movement of the support itself.

The movement of the slide and the tool holder is set by the specified amount by means of a screw with a flywheel, which has a ring with metric divisions. The handwheel is manually driven.

In order to assemble a turning device with your own hands, you will need:

hydraulic cylinder;

shaft from the shock absorber;

corner, channel, metal beam;

electric motor;

two pulleys;

Belting.

Homemade lathe on a channelA homemade lathe with your own hands is assembled in this way:

A frame structure is assembled from two channels and two metal beams. When working in the future with parts longer than 50 mm, materials with a thickness of at least 3 mm for the corner and 30 mm for the rods should be used.

The longitudinal shafts are fixed on two channels with guide rails with lugs, each of which is bolted or welded.

For the manufacture of the headstock, a hydraulic cylinder is used, the wall thickness of which must be at least 6 mm. Two bearings 203 are pressed into it.

A shaft is routed through bearings with an inner diameter of 17 mm.

Hydraulic the cylinder is filled with lubricant.

A nut with a large diameter is installed under the pulley to prevent the bearings from being squeezed out.

The finished pulley is taken from a used washing machine.

The caliper is made of a plate with cylindrical guides welded to it.

The chuck can be made from a piece of pipe of a suitable diameter, with nuts welded on it and holes made for 4 bolts.

The electric motor of the same washing machine (power 180 W), connected to the headstock by a belt drive, can serve as a drive.

In situations where the turning equipment is out of order, it is absolutely not necessary to purchase a new expensive unit. After a competent repair, lathes will again be able to efficiently and efficiently perform all technological operations for metal processing. Before understanding such a process as the repair of a lathe, you need to remember what turning is and how the equipment for its implementation is arranged.It is not always possible to buy new equipment. There is only one way out - repairWhen carrying out turning, the problem is solved to reduce the diameter of the workpiece, which makes a rotational movement, being fixed in the spindle of the machine. Removal of the excess metal layer (due to which the diameter of the workpiece decreases) is performed by a cutter equipped with a cutting edge.It can move in the longitudinal (feed) and transverse directions. By setting the parameters of these movements (rotation, longitudinal and transverse movement of the cutting tool), it is possible to regulate the thickness of the removed metal layer and the shape of the chips and influence the quality of the processing performed.