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  1. #1
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    6,439

    Thumbs up Poor mans toolpost grinder.

    Hi Guys,

    For long enough I've had a flexible shaft set in a mount that I could fit into the toolpost of my Myford lathe.
    Any way I needed to use it this morning to do a job. It only takes a few minutes to set it up.
    Five minutes later I switch on the Dremal that runs it and weeee, bang clatter bang, screech, all stop.
    The electronic speed control goes short circuit, and the motor goes into full bore. The grinding stone in the chuck decides that it wants to run around in circles and promptly seizes up.
    Net result the bearings in the flexible handpiece couldn't stand the strain of the grinding stone shaft bending through 90 degrees.

    So after getting over the shock and still needing to get the job done, and having another Lidl special Dremal tool, I decided to make a similar mounting for it so I could do the same as I had with the flexible shaft.


    30-09-2018-007.JPG 30-09-2018-008.JPG 30-09-2018-009.jpg
    I had I bit of 1/2" inch aluminium bar approximatively 50 mm X 38 mm. So I marked it out for a hole on the centre line, and 25 mm in plus 12 mm for the bit that goes into the lathe toolpost. Centre popped it. Stuck in in the four jaw chuck, and after centering it up, drilled a 16 mm hole with a blacksmiths drill. I then used a 12 mm slot drill as a boring bar to open out the hole to 18.5 mm to suit threading 2 mm pitch for the thread on the end of the Dremal copy. I used the same threading tool and carbide insert as I have shown before.


    30-09-2018-005.JPG 30-09-2018-006.JPG
    This is the threaded end on the Dremal. There was a plastic cap screwed on here which is where the flexible drive would be fastened to.
    Those threads are not the best I've seen. The damage to the first thread was caused by me trying to test fit without removing the mount from the chuck.


    30-09-2018-003.jpg 30-09-2018-004.jpg
    Here is the finished product fitted in my new Norman Tool Holder.
    The abrasive wheel and shaft is Identical to the one that bent and became bin fodder.

    I've spent most of the day doing what should have been a twenty minute job.
    I think I've earned my dinner today and a nice bottle of Australian Shiraz

    Thanks Guys.
    Best Regards:
    Baron J.

  2. #2
    Join Date
    Nov 2010
    Location
    Gippsland Victoria
    Posts
    733

    Default

    Hey BaronJ, well done.

    What sort of things do you use it for - I have always been a bit puzzled by tpg - are they mainly for working with veryvery hard materials that you cannot cut with a hss or tungsten carbide cutting tool ? Ie putting a fresh point on a mangled hard centre that got cooked one day long ago in the tailstock ?

    Bill

  3. #3
    Join Date
    Nov 2007
    Location
    melbourne australia
    Posts
    3,228

    Default

    Hi Bill,
    I won't speak for John, but here's one use for a small TPG. Drilling a 0.5mm hole in a fuel spray bar in a model engine carby. I've also used it to sharpen a large HSS milling cutter using the xanadu (Rob) method. Also great for drilling indexed holes (up to 3mm diameter) in a round workpiece. Many uses!
    Attached Images Attached Images
    Chris

  4. #4
    Join Date
    Jun 2007
    Location
    sydney ( st marys )
    Age
    64
    Posts
    4,887

    Default

    That's not a Tool Post Grinder, it's a die grinder of sought used in a tool post.

  5. #5
    Join Date
    Nov 2007
    Location
    melbourne australia
    Posts
    3,228

    Default

    Surely any grinder mounted in a tool post has to be a tool post grinder?
    Chris

  6. #6
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    6,439

    Default

    Hi Guys, thanks all for your support.

    I've done all sorts of what I call little jobs with the flexible held in the toolpost, using a similar bracket.

    Yesterdays job was to square up the end of a 6 mm slot drill, that I dropped on the floor chipping half the corner off one flute. Only a couple of thou. I then used the four facet drill grinder to put new cutting edges on it.

    In hindsight, I could have done the whole job using the drill grinder !

    Actually I I'm thinking about making another four facet grinder with a much bigger chuck capability, say 20 mm. at the moment 3/8" (9 mm) is about as big as I can go. The other thing is that the drill grinder doesn't have any stops, so you have to be very very careful not to catch the opposite flute when sharpening slot drills. I can just about manage a four flute but its very very tight, particularly with non centre cutting ones.
    Best Regards:
    Baron J.

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