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Thread: Carriage reverse for Grizzly G9729

  1. #1
    Join Date
    Oct 2008
    Posts
    8

    Default Carriage reverse for Grizzly G9729

    I've always wanted a lathe and mill but can't afford a real good one so I settled on a Grizzly G9729 combination unit ( http://www.grizzly.com/products/Combo-Lathe-Mill/G9729 ). It is an OK machine and it did take a while to get used to it (I worked at IBM for almost 16 years and as a shift mechanic, I had access to a Hardinge late, Bridgeport vertical mill, Brown & Sharpe surface grinder all of which spoiled me because they were so easy to use and accurate even for a "metal butcher" like me! LOL!).

    My main problem with the G9729 is that the carriage feed drive isn't reversible. It is directly driven off of the spindle drive through a set of gears which means that at the end of all cuts you have to move the cutting tool away from the work piece, move the carriage back to the starting point, then re-establish the last cut dimension (zero) plus whatever cut depth for the next cut.

    Has anyone built a carriage reverse for this lathe/mill tool and if so, can you share pictures, prints, parts, etc. that it took to build it.

    Any and all assistance will be greatly appreciated.

  2. #2
    Join Date
    Oct 2008
    Posts
    8

    Default

    I sat down with my AutoCadLt program and puzzled out a solution on paper (the real test will be to come up with the gears to implement it).

    Here's my idea: the gear that presently drives the carriage drive off the spindle (which I call #1) will be changed by boring it out and installing a sleve bearing so that it rotates on the spindle shaft. The spindle shaft will be extended to put so that a gear (#5) that will drive all the time BUT can slide on that shaft on a keyway. #5 will engage #4 which will be solidly keyed on a shaft with #3. #3 will engage an idle gear #2 with is engaged at all times with #1.

    Forward: #5 would disengage with #4 then it would engage #1 driving the carriage forward.

    Reverse: #5 engaged to #4 which rotates #3 which rotates #2 which rotated #1 in the opposite direction thus driving the carriage in reverse.



  3. #3
    Join Date
    Oct 2008
    Posts
    8

    Default

    Having NO time to build the reversing gear setup, I have been putting up with the Grizzly G9729 lathe/mill‘s non-reversing carriage drive.

    Then I read an article in an article in the November/December 2009 Home Shop Machinist that solved my quest. The article "Variable Speed for Your Power Tools - A DC Motor and Controller" by Jerry Pryor was exactly what I wanted--a simple way to install variable speed and reversing!

    I found a Bodine DC motor and controller on EBay for $100. I had all the switches, lights, fuse holder & fuse, wire, an 8" pulley, a 2" pulley and a fan belt from my car parts V-belt bin. All I lacked an enclosure to put all of it in, a motor mount bracket, and a cooling fan.

    I bought a 6' X 6" X 4" CPVC box at Robson Electric for $22. In retrospect, I should have bought a 6” deep one instead of the 4” deep one as it is a tight fit for all of the parts that need to go in there.

    I bought the 12 VDC 30 CFM fan at Unicorn Electronics for $10.

    The motor bracket I made from base plates 2 ea. 1/4" X 4" X 6" and face plate 1 ea 1/4" 4" X 4" hot rolled steel and a 3" hinge. Once all it was machined and assembled, the motor pivots on the hinge so that the belt drive can be tensioned.

    You may ask why the HUGE 8" pulley. In retrospect, had I known how slow a gear drive motor I needed, I should have opted to buy one with less output RPM. The Bodine 24A2BEPM-D3 has an output peak of 208 RPMs. What I should have gotten was one with 50 RPMs peak so that I wouldn't have had to put a 4:1 reduction on it. Although the 1/29 is adequate, I would recommend one of 1/8th HP or bigger.

    I’ve already used it on a few projects and especially LOVE having the carriage reverse and the “fast feed” option that the speed controller has.

    List of materials:

    Variable speed DC motor and controller. Motor with a max RPM of 50 and at least 1/8 HP.

    6” X 6” X 6” CPVC junction box with cover.

    DPST toggle switch.

    DPDT toggle switch.

    Power light assembly (I happened to have a 120 VAC neon light assembly but anything will do)

    Cooling fan. I chose a 12VDC one as it was small enough to fit into the junction box and I had a spare 12VDC transformer on hand.

    Male and female connectors. ALL the wiring in my project uses these connectors. It give me the capability to remove any single component without disturbing the wiring.

    Steel (or aluminum) plate for mounting brackets.

    ¼” hardware cloth for vent covering material. It keeps fingers out of the junction box while allowing for airflow in and out of it.

    A variable means of tensioning the belt drive. I used a tarp strap but a spring would also work.


    Picture of the installed assembly:



    Drive motor and the mounting bracket:



    Control box:


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