Annealing Delrin Guides



Author Topic: Annealing Delrin Guides  (Read 275 times))

Offline Artie

  • Sharp Shooter
  • ****
  • Posts: 702
  • yes
  • Real Name: Richard
Annealing Delrin Guides
« on: February 14, 2019, 07:53:01 PM »
Today I ran across a BBS airgunning thread and one of the contributors recommended boiling delrin guides in water for 5 minutes prior to installation. He said he never had a broken guide after adopting the method.
This notion led me to some research on plastics and apparently Delrin does aneal at 320 F. My question is: has anyone else heard of this or ever experimented with it?
Incidentally, I've not broken an installed delrin guide but I have broken one shaving the shoulder in a lathe.
  • North Carolina

Offline nced

  • GTA Senior Contributor
  • ******
  • Posts: 3626
Re: Annealing Delrin Guides
« Reply #1 on: February 14, 2019, 08:40:03 PM »
Today I ran across a BBS airgunning thread and one of the contributors recommended boiling delrin guides in water for 5 minutes prior to installation. He said he never had a broken guide after adopting the method.
This notion led me to some research on plastics and apparently Delrin does aneal at 320 F. My question is: has anyone else heard of this or ever experimented with it?
Incidentally, I've not broken an installed delrin guide but I have broken one shaving the shoulder in a lathe.
LOL.....I've never had a Delrin guide break either.
Hummmm.......how does water at 212 degrees F anneal Delrin IF the annealing temp is 320 degrees F unless the water is pressurized?

Offline Artie

  • Sharp Shooter
  • ****
  • Posts: 702
  • yes
  • Real Name: Richard
Re: Annealing Delrin Guides
« Reply #2 on: February 14, 2019, 09:19:19 PM »
Excellent question Ed, my guess is it would require a pressure cooker.  That or the Brits got some special water in them pipes.
  • North Carolina

Offline Motorhead

  • Field Target Shooter .... AAFTA 2018 Gran Prix Hunter PCP High Point Champion.
  • GTA Senior Contributor
  • ******
  • Posts: 13763
  • "EXPERIENCE" ... Our Reward For Lifes Mistakes
  • Real Name: Scott
Re: Annealing Delrin Guides
« Reply #3 on: February 14, 2019, 10:02:41 PM »
Never had the need ... wear & tear already minimal & never broken one either ???
  • Northern California ... Old Hangtown
** Home of MOTORHEADS AG Tuning Services **
        ** PM me for further contact & tuning info.

       Sacramento Valley Field Target Club
#https://sites.google.com/site/sacvalleyairgunclub/

Offline Artie

  • Sharp Shooter
  • ****
  • Posts: 702
  • yes
  • Real Name: Richard
Re: Annealing Delrin Guides
« Reply #4 on: February 14, 2019, 11:01:01 PM »
I had a gun I'd turned a guide for. The setup had no spacers except for a thin thrust washer and an over-thick shoulder on the rear guide. It turned out the setup was coil bound (wouldn't latch). My choice was remove the thrust washer, cut a coil, or thin the rear guide shoulder by re-facing it.  I chose the latter.
The guide had very thin walls due to tight tolerances between the spring and latching rod. Tightening the chuck enough to prevent the delrin from slipping would've crushed the thin walls so I wrapped the guide with carpet tape to prevent slippage. It worked perfectly, didn't slip a bit when the shoulder snapped clean off.
Got's to be more careful next time, sneak up on it a few thou at a time I reckon..
« Last Edit: February 14, 2019, 11:11:42 PM by Artie »
  • North Carolina

Offline rgb1

  • Plinker
  • **
  • Posts: 137
Re: Annealing Delrin Guides
« Reply #5 on: February 15, 2019, 10:30:13 AM »
Annealing and stress relieving are two distinctly different processes, though
people in the plastics industry will oftentimes use them interchangeably.
Most delrin, but not all, will already be stress relieved by the manufacturer......
your supplier should have such information.
To ensure good dimensional stability on low tolerance parts, I use the boiling
water method (5-10 minutes depending on thickness) prior to any machining.


                                                                                         Ron
  • IN

Offline Artie

  • Sharp Shooter
  • ****
  • Posts: 702
  • yes
  • Real Name: Richard
Re: Annealing Delrin Guides
« Reply #6 on: February 15, 2019, 12:11:14 PM »
Thank you for the clarification Ron. It's all very interesting to me. One issue is perhaps genericized trademarks, Delrin for example. Homopolymer vs coplymer, selling acetal under the Delrin tradename when it's actually unbranded copolymer acetal, distinctions I was blissfully ignorant of until yesterday. I highly doubt it makes any difference for spring guides but it does complicate Google searches.
So now I know of two people that boil Delrin or acetal. One boils after machining, the other before machining. You comments are knowledge based, the other guy's comment was empircally optimistic, "I don't know why it works but it does." The assumption is he had a problem with broken guides before the boil. I'm gonna try it your way.
Next question, do you use your wife's sauce pan or her pressure cooker?
« Last Edit: February 15, 2019, 12:21:02 PM by Artie »
  • North Carolina

Offline Vee3

  • Marksman
  • ***
  • Posts: 392
  • yes
  • Real Name: Victor
Re: Annealing Delrin Guides
« Reply #7 on: February 15, 2019, 11:44:47 PM »
FWIW, in machining 1000s of acetal parts of all shapes and sizes, I found that the white (natural) stuff was always more brittle than the black. I have no idea why.
  • CA

Offline Artie

  • Sharp Shooter
  • ****
  • Posts: 702
  • yes
  • Real Name: Richard
Re: Annealing Delrin Guides
« Reply #8 on: February 16, 2019, 09:28:02 AM »
FWIW, in machining 1000s of acetal parts of all shapes and sizes, I found that the white (natural) stuff was always more brittle than the black. I have no idea why.

Go figure. I placed an order yesterday.. white
  • North Carolina

Offline nced

  • GTA Senior Contributor
  • ******
  • Posts: 3626
Re: Annealing Delrin Guides
« Reply #9 on: February 16, 2019, 02:28:26 PM »
FWIW, in machining 1000s of acetal parts of all shapes and sizes, I found that the white (natural) stuff was always more brittle than the black. I have no idea why.
Hummmmm.....according to McMaster Carr it seems that both black and white have the same specs regardless of the color..........


Delrin vs Acetal...........
https://www.iplasticsupply.com/plastic-materials-list/acetal-delrin-celcon-basf-pom-pomalux-sheet-rod/

According to this "applications box" of the above link, there are times that Delrin is actually stress relieved before the final finish cut..........
"This materials is an excellent machining material a favorite of machinists. Works like a soft brass, and has exceptional dimensional stability. It comes as a stress relieved material, however if you plan to do extensive machining, you may need to stress relieve the parts prior to final pass. Rods are machined well in lathe and mill, sheets are machined or cut in most common machine tools."

Doing some comparisons on the McMaster Carr site and found some interesting stuff.........

Price:
Delrin....1 1/4" diameter......$7.00/ft
Acetal....1 1/4" diameter......$7.62/ft

Tensile Strength:
Delrin....9,000 psi (Good)
Acetal....6,400 psi (good)

Anywhoo, I really never paid much attention to "black vs white" or even "inherent center-line porosity in the Delrin Homo-polymer version" simply because about 10mm of the rod center is drilled out for clearance with the piston latch rod.

A while back I bought some Acetal Homopolymer called (Rod, Acetal, 150, Wht, 1-1/8" Dia x 1 ft. L" (labeled 2XMH2) for $6.90/ft.
This site which claims a tensile strengtht of 11,000psi..........
https://www.grainger.com/product/DELRIN-Rod-2XMH2
The "(Rod, Acetal, 150, Wht, 1-1/8" Dia x 1 ft. L" (labeled 2XMH2)" worked just fine, however so did all the other materials I used.

Here is a pic of my rods.........




Offline Vee3

  • Marksman
  • ***
  • Posts: 392
  • yes
  • Real Name: Victor
Re: Annealing Delrin Guides
« Reply #10 on: February 16, 2019, 10:54:35 PM »
FWIW, in machining 1000s of acetal parts of all shapes and sizes, I found that the white (natural) stuff was always more brittle than the black. I have no idea why.
Hummmmm.....according to McMaster Carr it seems that both black and white have the same specs regardless of the color..........

Company I worked for never bought name brand Delrin. It was always one or another supplier's acetal. Maybe it's a Coca-Cola vs Kroger cola kinda thing, lol. You could dig your fingernail into the black stuff and leave a ding, where the white stuff was more resilient.
  • CA

How do you word it... "Air Guns" or "AirGuns"?
Sponsored Ad:
 

Sponsored Ad: