Re: A big ol' chunk of delrin

On 4/20/2025 11:31 AM, Snag wrote:

On 4/19/2025 11:41 AM, Bob La Londe wrote:

On 4/18/2025 6:45 PM, Snag wrote:

   Since no one currently has X axis leadscrew nuts available for my RF45 clone mill , I must make one . So I ordered a piece of acetal/ delrin . I've been studying videos of heat forming a nut to your leadscrew, all looks fairly easy . I'll use a piece probably about 2X2X3 for the nut . I bought a chunk that turns out to be 2 1/2X3X12 ... just in case it takes more than one attempt .

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Let us know how it goes.  I first heard of heat forming Delrin nuts right here on this group years ago.  For my application I went with a spring loaded anti backlash Delrin nut from DumpsterCNC back then instead.  I don't think DumpsterCNC is still around.
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    This is interesting , your text did not show up in the post over on e-s but it did here on blocknews ...
    Now to the meat of the sammich . I have been out in the shop all morning making a tap* to match - pretty closely - the leadscrew on the mill . The plan as of right now is to tap the hole I have made in a chunk of that delrin . I'm hoping for a tight fit so I can heat the leadscrew to finish forming the threads without splitting the nut . If it's loose I'll slice the nut in half and heat/clamp to finish forming the threads . If it's too tight to thread on I can split one side to get it on the leadscrew and heat form from there .
   *I still have to form the flutes on that tap . I'm thinking a 1/2 or 3/8 ball end mill With the tap held in a 4 sided collet holder or maybe do 6 flutes since this tap is just under an inch . I used a chunk of 1.25" rebar for the tap since it was the closest in size to the finished product and I hate wasting material . I'm not planning on hardening it , this will likely be the only time it will ever be used .
   I also have 9 inches of 2 1/2 inch square aluminum stock coming to make a holder for the nut . Probably only use a couple of inches , but hay , I'll have stock for other projects down the road .
    shop break
   Well , the tap idea isn't going to work , I guess I'll stop and rethink my approach . But at least I was outta my wife's hair for the whole morning !

I actually made a second post talking about creating a makeshift tap from a piece of the the same acme or trapezoidal thread.  It never showed up.  I only post through ES these days, but I do read the group when I'm out of the office on narkive.
Making a single point tool, as others have mentioned, is an option, but a form tool that large can cause chatter, deflection, and other issues. An option is of course a narrower form tool.  Cut the thread, and then offset the tool until you get the width you need.
In any case you already have a gage you can use to make the form tool.
Internal single point can be tricky, but your tool bit can be short and held in an old school shop made boring bar.  Cross drill for the tool bit.  Drill and tap the end for a grub screw.
I realize you already have Delrin, but brass or bronze pinch nuts can make decent reduced backlash lead screw nuts.  Particularly bronze. Typically three screws.  Two pulling it together and one pushing it apart.  At the same time you can drill and tap for an oil line.  A fairly sloppy nut can be adjust to less than one thousandth backlash. My very first mill, the Taig CNC mill, used "precision" v-leads and pinch nuts on all 3 axis.  I could dial in to about a half thousandth backlash for precision work, or let it flop around at about 3 thousandths for faster running without losing steps on the motors.  I did have to decide what good enough was for the various capabilities.
My second CNC mill, (The Max NC 5) also used pinch bnut son V-leads, btu I changed it to spring loaded DumpsterCNC nuts on acme screws for X/Y and a ball screw on Z.
If you single point I think you can hand grind more than accurately enough to cut your nut if you don't have other options, but I seem to recall you do have some real tool grinding capability.
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Bob La Londe
CNC Molds N Stuff
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