Pressing metal nipple into rubber duct
Discussion
I am replacing an intake hose on Mrs D's Honda S2000. Whilst doing some other work I noticed that on the duct from the airbox to the throttle valve the rubber had started to deteriorate around one of the branches, so am replacing that duct.
I have hit a snag: one of the branches into this duct is mated via a metal nipple/bushing, and the corresponding hole on the new duct is a blind hole, see pic.
This picture shows the metal piece that I have removed from the old duct, and the hole it is meant to go into.
The next two photos show what the finished item looks like (sort of... This is actually the duct from an early S2000 and the nipple is slightly different. Also, they came pre-fitted with the nipple for the early S2000s).
This is how it looks when assembled in the car (the hose goes off to the secondary airpump)
The blind hole in the new duct isn't a bung, I have checked thoroughly. It's simply how the rubber has been moulded, presumably for manufacturing reasons.
My options seem to be:
1) Drill the hole out. This doesn't seem a great idea as rubber is far too pliable to drill accurately and I'll also probably end up chewing the sides of the mating surface.
2) Use some sort of hole punch. Really no idea what would do this
3) Hammer or press the metal piece in and use this to cut the hole. I've seen this with outdoor electrical boxes, no idea if that's the intention here. The complication is that it's a squishy hose, so I think I would need to slide a piece of wood into the duct, fasten the wood into my vise and start hammering in the nipple from the outside.
3 seems to me to be the way to fit it. Has anyone come across the same or similar, and if so how did you tackle it?
I have hit a snag: one of the branches into this duct is mated via a metal nipple/bushing, and the corresponding hole on the new duct is a blind hole, see pic.
This picture shows the metal piece that I have removed from the old duct, and the hole it is meant to go into.
The next two photos show what the finished item looks like (sort of... This is actually the duct from an early S2000 and the nipple is slightly different. Also, they came pre-fitted with the nipple for the early S2000s).
This is how it looks when assembled in the car (the hose goes off to the secondary airpump)
The blind hole in the new duct isn't a bung, I have checked thoroughly. It's simply how the rubber has been moulded, presumably for manufacturing reasons.
My options seem to be:
1) Drill the hole out. This doesn't seem a great idea as rubber is far too pliable to drill accurately and I'll also probably end up chewing the sides of the mating surface.
2) Use some sort of hole punch. Really no idea what would do this
3) Hammer or press the metal piece in and use this to cut the hole. I've seen this with outdoor electrical boxes, no idea if that's the intention here. The complication is that it's a squishy hose, so I think I would need to slide a piece of wood into the duct, fasten the wood into my vise and start hammering in the nipple from the outside.
3 seems to me to be the way to fit it. Has anyone come across the same or similar, and if so how did you tackle it?
Drills don't really work on rubber, esp for large diameters in thin sections.
Make your own punch! Simply sharpen the end of a suitably sized piece of pipe, or an old socket (being rubber it's not like it's critical to 2 decimal places!) Or you may find that your metal spigot will suffice. But yes, you'll need a stout bit of wood inside the hose to serve as an anvil.
Make your own punch! Simply sharpen the end of a suitably sized piece of pipe, or an old socket (being rubber it's not like it's critical to 2 decimal places!) Or you may find that your metal spigot will suffice. But yes, you'll need a stout bit of wood inside the hose to serve as an anvil.
Thanks all for the advice and ideas. Update on how I did in case it helps anyone in a similar situation.
Firstly, I grabbed a nice new holesaw and arbour, thinking more sharp = more better, plus being new it had zero nicks and burrs on the saw that could damage the rubber. I wrapped some self-fusing silicone tape around to ensure the flutes wouldn't snag on the rubber and potentially to reduce friction if there was a touch against the rubber (although I knew I would be using very slow drill speeds).
If the blind end of the bunghole was flush with the inside of the duct I could have used a piece of wood as my anvil and it would have cut through no issues, however as it was about 1cm up from the duct the rubber cut around halfway around the perimeter of the hole and then just stretched around the holesaw. The usual tricks of changing angle of attack and getting the drill up to speed before contact did nothing, because well.. It's rubber! I think I'd have had the same issue if I'd gone to the back-up plan of a sharpened piece of 15mm copper pipe; you really do need an anvil to put a (nice) hole through rubber, to stop the rubber moving away from the tool.
I then remembered I'd recently seen a random hobby knife kit I'd bought and stuck in the workshop. Amazingly, I found it. I then used the finest scalpel to cut the rest of the hole out.
I don't know if the holesaw had scored the rubber but I was able to make the hole neat enough, and then of course I un-neatened it when I tried to fettle it into even more roundness. This was my offering to the gods, to hopefully avoid further cock-ups.
Then, I placed the nipple in my bench vise and tightened it just enough to stop it wobbling without turning it oval. To make another offering to the gods I of course deliberately neglected to use soft jaws or to wrap the nipple in tape, hence the apprentice marks into the yellow passivation layer that are definitely deliberate and don't annoy me whatsoever. I then positioned my new hole over the protrusion and pushed, wiggled and twisted until it popped neatly into place. No oil to ease its passage, I went in dry. Like a man. If that hadn't worked I would have used a smear of engine oil - there is a PCV system on this car so the materials here should be resistant to engine oil. I really wouldn't use silicone grease; maybe I'm overthinking things but silicon contamination in fuel destroyed a lot of engines some years back, so I'm in no rush to introduce it into my intake system!
Finally, as the duct had some fine dust inside (possibly from manufacture, possibly from storage as I don't know when it was manufactured) I gave it a jolly good washing out and left it to dry. This duct carries filtered air to the throttle so if that dust happened to be something that shouldn't be in the engine, I don't want it there!
Firstly, I grabbed a nice new holesaw and arbour, thinking more sharp = more better, plus being new it had zero nicks and burrs on the saw that could damage the rubber. I wrapped some self-fusing silicone tape around to ensure the flutes wouldn't snag on the rubber and potentially to reduce friction if there was a touch against the rubber (although I knew I would be using very slow drill speeds).
If the blind end of the bunghole was flush with the inside of the duct I could have used a piece of wood as my anvil and it would have cut through no issues, however as it was about 1cm up from the duct the rubber cut around halfway around the perimeter of the hole and then just stretched around the holesaw. The usual tricks of changing angle of attack and getting the drill up to speed before contact did nothing, because well.. It's rubber! I think I'd have had the same issue if I'd gone to the back-up plan of a sharpened piece of 15mm copper pipe; you really do need an anvil to put a (nice) hole through rubber, to stop the rubber moving away from the tool.
I then remembered I'd recently seen a random hobby knife kit I'd bought and stuck in the workshop. Amazingly, I found it. I then used the finest scalpel to cut the rest of the hole out.
I don't know if the holesaw had scored the rubber but I was able to make the hole neat enough, and then of course I un-neatened it when I tried to fettle it into even more roundness. This was my offering to the gods, to hopefully avoid further cock-ups.
Then, I placed the nipple in my bench vise and tightened it just enough to stop it wobbling without turning it oval. To make another offering to the gods I of course deliberately neglected to use soft jaws or to wrap the nipple in tape, hence the apprentice marks into the yellow passivation layer that are definitely deliberate and don't annoy me whatsoever. I then positioned my new hole over the protrusion and pushed, wiggled and twisted until it popped neatly into place. No oil to ease its passage, I went in dry. Like a man. If that hadn't worked I would have used a smear of engine oil - there is a PCV system on this car so the materials here should be resistant to engine oil. I really wouldn't use silicone grease; maybe I'm overthinking things but silicon contamination in fuel destroyed a lot of engines some years back, so I'm in no rush to introduce it into my intake system!
Finally, as the duct had some fine dust inside (possibly from manufacture, possibly from storage as I don't know when it was manufactured) I gave it a jolly good washing out and left it to dry. This duct carries filtered air to the throttle so if that dust happened to be something that shouldn't be in the engine, I don't want it there!
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