Re: A big ol' chunk of delrin

On Sun, 20 Apr 2025 22:42:39 -0500, Snag <Snag_one@msn.com> wrote:

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 .

>
>
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.
>

 
   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.
>
-----------------------
>
 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" .

Don't be a wuss -chuck it in the 4 jaw and single point it. If you
grind your tool right you won't even need to heat form it - - - -