First of all, the spindle-bore taper as well as the taper of the arbor are cleaned. Then the arbor is fitted into the spindle and locked against the taper by a drawbolt. The hob is then fitted on the arbor along with spacing collars, and the tailstock bracket is brought in position to support the other end of the arbor. The nut is locked for locking the hob and spacing collars together. The runout of the hob is checked on the proof-diameter. This should be within 0.005 (0.0002’).
The work is then mounted on the table. The method of supporting the work piece on the table varies from job to job. However, this should ensure that the job runs true with the table-axis. In one off or batch production, this can be checked for every piece and corrected.
However for mass production, the fixture and blank manufacture should ensure that this runout is repeatedly maintained piece after piece.
Necessary change gears are mounted to select the proper speed ratio between the hob and the work piece. Hob head is then set according to the helix angle of the hob as shown in Fig. 9.11. Speed of the hob is dependent on the material of the blank (and the hob material).
Depending on the feed requirement, - radial, axial or diagonal – feed is selected. Feed rate is also dependent on the material and whether the hobb is being used for roughing or finishing.
Now the table is brought towards the hob so as to have the hob just touching the work piece. The dial on the lead screw for the table drive is set to zero. The machine is started without engaging the feed so that the hob makes light tooth markings on the outside diameter of the blank. These will indicate the number of teeth being cut. If these are equal to the required number of teeth to be cut, selection of change gears is correct. Now the feed is engaged. The table is fed to the distance equal to the depth of the tooth. After this setting and cutting the gear, the tooth thickness is measured. To thin the tooth further, if required, the table may be further fed.
The work is then mounted on the table. The method of supporting the work piece on the table varies from job to job. However, this should ensure that the job runs true with the table-axis. In one off or batch production, this can be checked for every piece and corrected.
However for mass production, the fixture and blank manufacture should ensure that this runout is repeatedly maintained piece after piece.
Necessary change gears are mounted to select the proper speed ratio between the hob and the work piece. Hob head is then set according to the helix angle of the hob as shown in Fig. 9.11. Speed of the hob is dependent on the material of the blank (and the hob material).
Depending on the feed requirement, - radial, axial or diagonal – feed is selected. Feed rate is also dependent on the material and whether the hobb is being used for roughing or finishing.
Now the table is brought towards the hob so as to have the hob just touching the work piece. The dial on the lead screw for the table drive is set to zero. The machine is started without engaging the feed so that the hob makes light tooth markings on the outside diameter of the blank. These will indicate the number of teeth being cut. If these are equal to the required number of teeth to be cut, selection of change gears is correct. Now the feed is engaged. The table is fed to the distance equal to the depth of the tooth. After this setting and cutting the gear, the tooth thickness is measured. To thin the tooth further, if required, the table may be further fed.
6 comments:
Gear cutting tool design and production requires much specialized knowledge, which has been acquired and refined over generations
gear hobs
For a gear hobbing machine which is a theoretical involute, the fundamental rack is straight-sided, with sides inclined at the pressure angle of the tooth form, with flat top and bottom. The necessary addendum correction to allow the use of small-numbered pinions can either be obtained by suitable modification of this rack
iftkhar
Plz show in vedio for setting
Gear Hobbing
very nice blog! Euro Gear goes the extra mile when it comes to gears. Using gear hobbing, we rapidly deliver long-lasting external gears, ensuring that we get you back to production quickly and cheaply.
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