2023 Author: Philip Bishop | [email protected]. Last modified: 2023-08-25 07:54
- How to properly grind the collector surface
- How to center the rotor in a drill before grinding
- Manifold Grinding Process
- How to clean the grooves of the punch manifold
- How to control the condition of the brushes
Correct operation of the Makita 2450 rotary hammer with a collector motor is accompanied by slight sparking of the brushes in the collector area. A properly working electric motor has uniform sparking with a short tail.
By changing the sparking pattern, you can determine the nature and location of the malfunction in the Makita 2450, 2470 hammer drill.
The reasons for the increase in sparking in the electric motor manifold can be the malfunction of the brushes and their wear, short circuit or breakage of the armature, malfunction of the stator windings of the electric motor, breakdown or improper fastening of the brush holders.
Significant sparking in the collector area leads to the appearance of grooves on the collector, burning of the plates, and uneven abrasion of the brushes.
The occurrence of these defects causes rapid wear and the development of lamellas of the collector itself.
Since the hammer drill is a powerful tool, slight sparking is allowed without load, with significant forces on the tool, single sparks can run in a circle. In the event of severe sparking, the cause of the strong sparking must be investigated.
The most common malfunction on the collector is the increasing roughness of the sipes with increasing sparking of the brushes.
The increase in the surface roughness of the manifold of the Makita 2450 perforator is not only due to increased sparking. Copper oxide is formed on the copper plates of the collector, which is harder than the hardness of carbon brushes. The roughness value is influenced by uneven brush wear and carbon deposits from sparking.
Scratches are formed not only due to uneven wear of the brushes and different material structures, but also due to the ingress of solid particles from the air into the working area.
Improper storage of the Makita perforator can lead to the appearance of oxide on the copper plates of the collector due to high humidity or significant temperature changes during operation.
To eliminate surface defects of the collector, it must be sanded.
How to properly grind the collector surface
Before proceeding with the modification of the manifold of the Makita 2470 perforator, it is imperative to balance the rotor.
At home, grinding the manifold of the Makita 2450 or 2470 perforator is best done with sandpaper fixed on a wooden block already on a balanced rotor.
The end of the rotor shaft is secured in the drill chuck through soft copper or aluminum foil. A drill with a rotor is securely fastened in a vice or a homemade device.
While rotating the rotor, try to center it in the drill chuck.
How to center the rotor in a drill before grinding
The rotor is centered in the drill chuck to ensure minimal runout of the collector radial surface relative to the rotor shaft.
First check the runout of the chuck jaws. Fix the drill in a vise, install the drill of the largest diameter in the chuck.
While rotating the drill, bring the pencil to the rotating side surface of the drill, resting it on a simple stop. With minimal runout, the pencil will draw a solid line on the surface of the drill. If the runout is significant, change the drill chuck or select a drill with less chuck runout.
Now, instead of a drill, clamp the rotor shaft and in the same way determine the places of the beating of the rotor or collector.
Manifold Grinding Process
The process of grinding the collector must begin with the selection of emery material. It is recommended to use sanding paper or file to sand the manifold.
Choose sanding paper of several numbers, starting from # 100 and up.
Now start sanding. Attach a wooden block with a fixed sandpaper to the collector, rotate the drill and, without pressing the block strongly to the surface of the collector, grind.
It is recommended to use the grinding operation on rotors that have already been running with a small depletion of the collector.
If you have replaced the collector on the rotor of the Makita 2470 perforator, then after it is attached to the shaft, the collector must be pierced. This operation is performed to eliminate the radial runout of the lamella surface of the new collector relative to the armature shaft.
It is best to grind the manifold on a lathe using mandrels. But you can perform this operation at home. True, one cannot do without an additional device. The video will help to understand the collector groove.
As a rule, the brush holders on rotary hammers are mounted opposite each other. Prolonged operation of the brushes leads to the formation of grooves on the collector, which form waviness on the surface. This generation can only be eliminated on a lathe by turning the collector.
To reduce the formation of grooves on the manifold, you should try to arrange the brush holders in a checkerboard pattern.
How to clean the grooves of the punch manifold
But the cleaning of the grooves between the lamellas must be carried out, since mikanite, the material of the gaskets between the lamellas, is harder than copper lamellas and wears out less. Over time, micanite gaskets wear less and are higher than copper lamellas.
To align the heights, the grooves between the lamellas are milled, or, in simple terms, grooved.
Do-it-yourself milling is best done with a piece of a metal saw, sharpened to the width of the manifold grooves.
A metal ruler is applied parallel to the edge of the groove, the saw is pressed against its edge and pulled out with weak pressure. The groove is milled to the height of the copper lamella.
Milling the grooves ends with the removal of the remaining material with a hair brush and chamfering with a scraper made from a file. Sanding is best done with felt.
Any milling should be finished with sanding and blowing air.
The state of the bearings also affects the amount of collector output. Bearing wear leads to increased collector runout, which in turn leads to accelerated wear of the carbon brushes. To eliminate the runout of the manifold, it is recommended to replace suspicious bearings with new ones.
How to control the condition of the brushes
When installing new carbon brushes, it is recommended to always grind them in order to better adhere to the collector surface.
It is best to customize carbon brushes on a homemade lapping machine. The lap is a shaft on which sandpaper is fixed. The easiest way is to make the shaft from wood with a diameter equal to the diameter of the collector, turning the workpiece on a lathe. A metal rod is tightly inserted into the shaft along the axis. The device is attached to the chuck of an electric drill, the drill turns on, and the brushes are fed to the rotating emery wheel.
Fitting should be done carefully, periodically applying brushes to the rotor manifold to check for light.
After rubbing the brushes to the collector, it is recommended to check the correct attachment of the brush holders before installing. The brush holders are factory set to neutral to minimize arcing on the collector. If there are no factory marks, then the adjustment of the installation of the brush holders is carried out by displacing the brush holder in the direction opposite to the rotation of the rotor until the formation of a spark is minimal.
The brushes should not dangle in the brush holder, but firmly press against the collector lamellas. The clamping force is regulated by springs in the brush holder.
An increase in arcing on the rotor collector may appear in connection with a short circuit of the armature, breakage of the armature coils, short circuit of the windings to the armature body. All these malfunctions are eliminated only with a major overhaul of the rotor.
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