Colchester Bantam Carriage Feed Speed

  1. Ianb Member

    Messages:
    210
    Location:
    Lymington, UK
    I am aware of the lever on the front of the lathe with the 6 selectable speeds, is there anything else that can be changed/selected to increase the feed speed as I am sure it used to be faster than it is now?

    Thanks
     
  2. Agroshield Member

    Messages:
    934
    I do not know how familiar you are with the machine, so apologies if this is too basic.

    You have two methods of producing 'feeds' on the machine: via the threaded leadscrew and via the keywayed lower shaft.

    The leadscrew is only supposed to be used for screwcutting and is joined to the carriage via the lever at the headstock end of the apron. Where the leadscrew enters the gearbox is a six-splined dog clutch to allow disengagement (non-rotation) when not in use.

    For everyday sliding (towards and away from headstock) and surfacing (towards and away from centreline of rotation) feeds, the lower shaft is used. This is engaged by the lever at the bottom, middle of the apron and sliding or surfacing selected by the three-position pull knob above it. The speed at which the lower shaft rotates determines how fast your feeds are.

    Its speed depends on a few factors. First, the change gears that link the lathe spindle to the gearbox input. If you have changed these, the shaft's speed will change. Second, there is an A, B, C range lever. This effectively gives a multiplier of '1' at B, '0.5' at C and '2' at A. Finally, you have the six position lever which controls which of six gears the gearbox is in. There is another lever as well but this is a simple forward/reverse.

    Look very well at the charts on the front of the machine and learn what they are telling you. There is a comprehensive data pack on the Bantam here

    https://drive.google.com/drive/folders/0B7dYs3wo6x0fcVlxbzdYX3ZEWjg?usp=sharing
     
    Last edited: Jul 14, 2020
    Dieselkid 63 and daleyd like this.
  3. xstian Member

    Messages:
    51
    Location:
    Norfolk
    I change my speed with the a,b,c range lever on the left, front of gearbox. This has enough adjustment for what I need. Also the carriage speed changes in relation to the rpm of the motor/piece you are turning.
     
  4. Agroshield Member

    Messages:
    934
    Yes and no. On a lathe, the feed rate is expressed in units of length per revolution (mm/rev. or inches/rev.). This will not change with spindle speed. Of course, if it is spinning faster, it will take less time to move that distance.
     
  5. Ianb Member

    Messages:
    210
    Location:
    Lymington, UK
    Thanks for the detailed responses, I am using the keyed shaft rather than the lead screw, but the lathe has been used to cut threads since I last used it so the change wheels may have been swapped for different ones and/or the A,B,C lever changed I will check, thanks.

    Does the A,B,C lever and change wheels just alter lead screw speed or keyed shaft speed?

    EDIT - Thanks for the help, just had a play with A,B,C lever and it seems like that will give me the speed I need.
     
  6. Muzzer New Member

    Messages:
    2
    Location:
    Lancashire, UK
    To answer the OP question - yes, both the screwcutting and power feeds are affected by the change wheels. The default gears are shown on the label but you can change the feeds by fitting different gears. IIRC, the gearbox input rotates slightly faster than the spindle in the default setup.

    Have you got the user manual? That shows how to set up feeds and speeds.
     
    Ianb likes this.
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