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Delrin gluing ?

axkiker

Aluminum
Joined
Jan 27, 2009
Location
Louisville ky
Im needing to make a part for an antique fishing reel I use. Its simply a knob on the side which controls the spool tension. The original was nothing more than a machined aluminum cap with internal threads that fit over the spool shaft. The problem is that the original never had any way to make sure the knob wouldnt back off as it was being used. As you fish it gradually would back itself off until eventually you re-tighten, or it falls off. As it did, and why im now making a new one.

So my thought was to make a new knob out of delrin, slightly smaller than the original. This way it would be fairly tight almost like an aircraft nut. Then make an aluminum cover that I would epoxy to the delrin. Just curious if its even possible to glue aluminum to delrin, and if so by what means.
 
I thought about that, but was unsure if it would hold over time. Its a fairly small part. roughly .5" x .25"

To me, press fits are an elegant and reliable way of joining things. I'd worry
more about the delrin threads wearing out than a proper press fit slipping.
 
Detents

A really nice solution might be spring loading a tiny ball in the nut and using a ball end mill to make a matching array of 12 to 16 recesses in the reel body. I can feel it clicking crisply and can hear the satisfying tic-tic-tic as it is adjusted to just the right tension. Really not that hard to do with a little careful mill work. Of course, you might not want to alter the reel if it is a collectors item or there might be other reasons. But if the button is a quarter of an inch thick, that is a lot of room to hide a 1/16th ball and and a spiral spring in a hole. Figure the coordinates for the recesses and away you go....

Fun to think about.
Denis
 
I did an extensive search for adhesives that would work with Delrin. I talked to many material and adhesive application engineers. The short answer is nothing sticks very well to Delrin. I would make sure your part design does not require gluing delrin.
 
I did an extensive search for adhesives that would work with Delrin. I talked to many material and adhesive application engineers. The short answer is nothing sticks very well to Delrin. I would make sure your part design does not require gluing delrin.

I recall that you can glue delrin if you use glue that is designed to work mechanically and rough up the surface of the delrin. I used a contact cement to glue delrin 'feet' to the bottom of a cheap plastic timer. I used epoxy the same way to afix a delrin 'cap' to a pushbutton.

Dan
 
Making the surface rough will help a bit, but the shear strength will still be very poor. I tried because I did not believe the app engineers. I was sure that I would find a way. I did not. It will work if you only need a weak bond, but any significant stress will break it. Be my guest - give it a shot.
 
Circa 1975, I designed a part in Delrin that would need to be modified for each application. One solution was to make two pieces and trim each to get the individual configuration. At that time, we were told that the only glue that would stick was also very toxic and not recommended for assembly workers. I think your only option is to make something that mechanically locks together.

BTW, the part was immersed in India ink. The first ones were Nylon, which worked, but they absorbed water and grew for months. Delrin, or Celcon, the same thing, absorbed a little moisture on the surface quickly and that was that. It's great stuff as long as you don't have to glue it.

Bill
 
There's a hobby cyanoacrylate that's advertised to work with Delrin, "Mike's Glue" might be the name- Google it. Nothing works well with Delrin and I wouldn't trust any glued joint. Is there anyplace you can use some small screws?
 
Might be worth looking into double sided adhesive tapes. There are varieties out there specifically made for handling difficult materials with differently formulated adhesives on the two sides. As I understand it the gluing properties of a non absorbent material are related to a thing called "surface energy" which has to be fairly well matched between the materials being stuck and the adhesive. Apparently better match means stronger bond. Delirin and many other plastics materials are difficult to bond due to the surface energy being very different to metals and other common materials. Hence its hard to find a glue to match the pair. For chemical reasons most glues don't match the surface energies of plastics very well so common offerings aren't very good at this job. Double sided tapes effectively cheat. Priming / chemical etching the plastic also helps.

A decade or so back I managed to get hold of a sample reel of special tape to solve a similar problem. Prolly a couple of metres for "£ not too much".

Clive
 
I did prototyping in plastics for many years. Nothing really adheres to delrin. Roughing up the surface with a coarse wood rasp gives a hairy surface for an adhesive to try to stick to. For this app, I always use Devcon Plastic Welder[22045?]. It's part epoxy, part meth-methacrylate[dental acrylic]. Seems to work better than most other types of adhesives for non-bondable apps. Be aware, it's somewhat flexible when cured, making it good for flexible substrates[PP,PPE, delrin, nylon], maybe less so for rigid ones. YMMV. JinNJ
 
Well maybe I should be looking at using a different material or method. I like the idea of having a small ball and detent which would allow that "click" as you turn, but the part is just too small and the machine work is probably above my ability. My only reason for thinking the press fit might not work is because there wont me much delrin there to be pressed in. The delrin is acting almost like the plastic in an aircraft nut is acting. Its only there to provide the friction to keep the knob from backing off.

So can someone recommend another material to be used, or do you feel a press fit would work.
 
I'd go with the press fit , I see no reason why it wouldn't hold up , though it may take some experimenting to find the right amount of press , another plus is that the al. cap will help keep the threads tight .
 
You should post a picture of the design.

It's not like you're doing a butt joint, so I bet it will adhere well enough for what you're doing.

A loctite applications engineer recommended this for delrin to aluminum.
Rough up delrin
770 Prism Primer
Loctite 401
McMaster has all of it.

Again, depends on the design. The Loctite will help your part stay put. It's not like there is zero adhesion.
 
Make aluminum knob, bore from outside end 50% depth. Press delrin into knob. Drill undersize. Thread aluminum, and taper thread the delrin(slightly). Put an aluminum cap over the delrin if you don't want it to show.

You have to use Delrin cause we know you have leftover from the shift knob.;)

Ben

Can you bore the knob thru, thread it thru, and make a threaded jam knob for it. If function is the problem, this would work, but not cosmetically.
 
Make aluminum knob, bore from outside end 50% depth. Press delrin into knob. Drill undersize. Thread aluminum, and taper thread the delrin(slightly). Put an aluminum cap over the delrin if you don't want it to show.

You have to use Delrin cause we know you have leftover from the shift knob.;)

Ben

Can you bore the knob thru, thread it thru, and make a threaded jam knob for it. If function is the problem, this would work, but not cosmetically.

Shift knob ????
 
Sorry bout the shift knob, got reading too much at once. Delrin on my mind, I think. Getting old and easily confused I guess.

Pressing the delrin from the outside would allow you to drill and pin it if worried about slipping.

Ben
 








 
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