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Re: [atlas_craftsman] Re: cutting inside thread

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  • Donald Lewis
    The attachment shows the final configuration of the thread cutting rig I used. Then thread is cut The face plate screws onto the spindle fine. Due to lack of
    Message 1 of 3 , Aug 8, 2013
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    The attachment shows the final configuration of the thread cutting rig I used. Then thread is cut The face plate screws onto the spindle fine. Due to lack of fore thought, after doing the truing cuts on the face plate the spindle nose sticks through. Not a terminal problem but not what I had in mind. I have considered putting a shim behind it but that will effect repeatability. I may build up the register surface with weld and re cut to true. Or I could just cut another I can use the practice any way. I like the Allen wrench idea, I have a pile of those
      I now have the experience of making a boring bar grinding a threading bit, cutting a thread with a lathe and making lots of chips. Total money spent 0. That = a good week and it is only Thursday Thanks for all the help Don.

    From: cliff <ken@...>
    To: atlas_craftsman@yahoogroups.com
    Sent: Thursday, August 8, 2013 6:33 AM
    Subject: [atlas_craftsman] Re: cutting inside thread


    Good points and example pix, JT. Here's something I do that has worked out well over the years; I have many old Allen wrenches (I sometimes buy a bunch at yard sales or flea mrkts), anyway just pick the biggest size for the bore and grind off the shorter leg so it just can be ground to the cutter shape you need. Cheap, easy, fast, and the spring in the Allen wrench seems to be of the good kind --rather like the goose neck tool holders. As time goes by one builds up almost any needed shape or size 'bar' this way. Anyway this works well for me, maybe it will work for someone else also.

    --- In atlas_craftsman@yahoogroups.com, <jerdal@...> wrote:
    > If the attachment comes through, here is a picture of some boring/threading bars usable for inside threading. The left one next to the rule is a regular boring bar of the type taking a short piece of lathe tool /cutter in a square hole. (it has a grooving tool in it at present, not a 60 degree threading tool) The other two were ground out of solid blanks.
    > The boring bar has about the sort of tool stickout that you want.... as little as possible, just enough to allow cutting the feature you need, which is in your case threads. You appear to have an extreme amount of 'stickout", which usually has a very bad effect.
    > if you stick out the cutting tool too far, you get several problems... First, there is a lot of torque on the bar, which wants to twist it in the holder. Second, you are open to chatter, caused by the springiness of the tool and bar. The shorter the distance from the support to the cutting edge, the less the springiness, and generally the less the chatter.
    > For "completeness", I have to mention that properly controlled, springiness can actually reduce chatter, but that is with a specifically designed tool, one that reduces its depth of cut as it springs. Normally, a cutting tool tends to dig in as it springs, which increases chatter.
    > JT
    > ----- Original Message -----
    > From: Donald Lewis
    > To: atlas_craftsman@yahoogroups.com
    > Sent: Wednesday, August 07, 2013 10:37 AM
    > Subject: Re: [atlas_craftsman] cutting inside thread [3 Attachments]
    > [Attachment(s) from Donald Lewis included below]
    > OK Update. I have attempted to attach picks of my lantern tool post and my newly made boring bar. Now I need to grind a threading bit and with the information from David I may be on my way Thank you all. Don

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