Re: A big ol' chunk of delrin

On 4/20/2025 7:51 PM, Jim Wilkins wrote:

"Snag"  wrote in message news:68053d6b$6$5278$882e4bbb@reader.netnews.com...
 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 did see Bob's post on E-S.
For a single use tap you could flute it with one corner of a square ended endmill, perhaps one with dull corners that you beveled sharp again, using your endmill fixture at the back relief instead of the cutting edge angle. If a hard spot in the rebar dulls it you can regrind it the same way. It's my go-to endmill for roughing steel of uncertain parentage and upbringing.
A tap drill size pilot plug on the tap may help keep it centered and straight.
In aluminum at least unhardened steel dulls quickly.
I will soon try making a tool from a scrap of broken rock drill pipe, and see how easy to saw and turn it is.
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  I'm thinking at this point that I might try threading the inside with a boring bar and a cutter that is close but narrower than the groove width of the thread . This will make it necessary to split the nut and hot form the thread . My main concern about splitting the nut is whether the halves will fuse together into a solid unit during the forming process . I'm once more stepping off into unknown territory ... but you know what they say "keeping learning will keep you young" .
--
Snag
We live in a time where intelligent people
are being silenced so that
stupid people won't be offended.