Recommend me a machine shop/machinist for this part (USA, China)

[TimNJ]

Hi all,

Is this the right forum...? Worth a shot I guess.

I'm working on a blowby oil catch-can project for my car which has a GDI engine. I'm planning to use a Parker-Watts coalescing or particulate filter in line with the PCV line from crankcase to intake.

I got the idea from a post made by a guy named Dave who owns a small company called "Conceptual Polymers". He sent me the attached drawing of an extended tank for use with these Parker-Watts pnuematic air filters. He no longer makes it this part and recommended I find a machinist to make it. I need only 2 or 3 pieces.

Does anyone have a machine shop they can recommend? I live in New Jersey, so if anyone is in the area and has a recommendation, let me know. Otherwise, I'm thinking China or elsewhere may be a cheaper option. Anyone work with a Chinese supplier who was okay for really small one-off volumes like this?

Thanks,
Tim

[PartialDischarge]

For low volume pcbway has a CNC service, but my take is that they are only competitive for a few units. I asked for a quote of 100 plastic cnc parts and they quoted me more than double compared to a local machine shop

[bdunham7]

I really doubt you'll find a Chinese vendor interested in one-off custom runs from an overseas customer.  You'll probably need to talk to someone directly. I no longer own a machine shop, as is the case with most of the zillions of them that existed two decades ago.  I can however give you an idea as to how to proceed. 

First, don't make this out of a solid piece of aluminum, that would be a huge waste of effort.  I would get a few feet of 0.188 wall 1.50 O.D. 6061-T6 tube and a foot of 1.5 O.D. 6061-T6 round bar from onlinemetals.com. 

Then I would find someone that does manual lathe work (CNC is not always your friend) and show them the drawing and the metals I recommend.  They can make the tube section and a stepped end cap which can be TIG-welded on (my recommendation) or made with threads (if you don't like the appearance of the weld). 

[TimNJ]

Thanks to both of you.

Well, this sounds like a perfect time to jump down the M-CAD rabbit hole. I tried LibreCAD a few times over the years, but did not have the time or patience to figure it out. Maybe I'll give it another shot, maybe with Fusion 360 or something..

Per suggestion:  Go with 1.50" aluminum pipe. On one end, cap it off with a butt-welded cap or. a "stepped end cap". What do you mean by a stepped end cap? Is this a cap which has a ledge that "sits" on the end of the pipe? Example photo?

Then, the only real piece to make is the threaded "adapter" which adapts the pipe to the funky 1-7/16 - 18 UNF threads. This could be similarly butt-welded as the end cap. Maybe something vaguely like the attached? Is that an example of a "stepped end cap" by the way?

What do you think about brazing instead of TIG welding? I think, at most, the housing needs to handle ~10-15PSI. If brazing seems okay, I can probably do it myself with a Bernzomatic, and then all I need is the adapter piece by itself.

Thanks!

[bdunham7]

I don't know the function of the device, so I've no idea if the inside needs to be bored to that spec or not.  I chose metals that could be most easily machined to that spec.  "Stepped end cap" seems self-explanatory and indeed your photo (the top parts) resemble what I mean, just replace the threaded section with solid metal, not as long.

I don't think attaching a threaded adapter--if you can find one--to the tube is a good plan.  A skilled machinist could easily make that very neat and precise by machining the end of the tube as drawn.  I can't recommend brazing aluminum, especially with parts of different thicknesses.  This probably isn't a first-time DIY project unless you are aspiring to be Red Green.

[TimNJ]

I don't know the function of the device, so I've no idea if the inside needs to be bored to that spec or not.  I chose metals that could be most easily machined to that spec.  "Stepped end cap" seems self-explanatory and indeed your photo (the top parts) resemble what I mean, just replace the threaded section with solid metal, not as long.

I don't think attaching a threaded adapter--if you can find one--to the tube is a good plan.  A skilled machinist could easily make that very neat and precise by machining the end of the tube as drawn.  I can't recommend brazing aluminum, especially with parts of different thicknesses.  This probably isn't a first-time DIY project unless you are aspiring to be Red Green.

Well..it's not so self-explanatory to me. "Stepped" often means many steps, to me. (Like a stepped drill bit.)

By threaded adapter, I didn't mean to find an adapter that would work, because that's basically impossible given the thread requirements. But, I understand that with a big enough wall thickness, should be able to machine the tube directly. Got it.

The function is simply to catch oil that escapes the crankcase, headed towarded the air-intake. It is a collection canister. The pressure seen by the canister will be pretty low, don't think it will ever get over 15PSI. Only reason I suggested brazing is because it seems it would be fine for low-strength/low-pressure application. If I couldn't find a machinist to do machining + TIG welding, I could suggest alternative and/or do it myself.

Thanks.

[james_s]

I know these guys: www.birdwellmachine.com/

I don't know if they'll be interested or not, but it doesn't hurt to ask. I know they occasionally do one-offs for random people when they're not swamped with high volume work.

[bdunham7]

I understand the catch can part, but I don't know what the part looks like that attaches to the threaded end nor how it seals.  It may or may not need to be very straight, machining it directly should result in very  straight, aligned threads.  Even if your brazing was strong enough, you might have porosity and all of your oil would just leak out when the system pressurizes.  Good TIG welders are perfectionists and I doubt you'd have any porosity.  Good luck hunting someone down that still does this type of work--they're out there, but the last few decades have been tough.

[jpanhalt]

I think this is what is meant by stepped endcap.  That avoids the butt weld.

[TimNJ]

Thanks all. I wonder if just making out of 3D printed plastic would make more sense from a cost standpoint. (These pneumatic filters are usually sold with a polycarbonate bowl, FWIW.) I've printed some parts (STLs the internet) with glass-filled nylon using HP multi-jet fusion and they were quite nice.

Not enough experience to know whether 3D printing will make good enough threads, guess I need to check what kind of resolution they can do and what resolution I might need to handle 1-7/16"-18.

Everything else is sounding quite expensive. Just an hour of set-up time in a machine shop is probably more than I want to spend altogether. Can't have your cake and eat it too, I guess.

[TimNJ]

Here is the normal filter assembly, attached.

[bdunham7]

So the goal is to simply make a longer version of the cup part?  Is that just for more capacity or for some other reason?  Do you know what material that part is made out of?  I think I've seen clear polycarbonate versions that are pretty long.

[Gregg]

It would be cheaper and easier to just purchase an automotive oil catch can already made similar to this:
https://www.amazon.com/dp/B06XK9PTP7
From my experience, coalescing filter elements have too fine of filter passages that would clog quickly with engine crankcase fumes and the replacement elements are really expensive.  I have used them on compressed air lines and soon discovered that the only way to economically use then was to install it after a standard filter/separator then a desiccant unit.

[andy3055]

If you Google for New Jersey Machine Shops, you get a whole lot of hits!

[CatalinaWOW]

If you want to do this yourself just substitute brass or copper for the aluminum material.  More expensive and heavier, but material costs won't be the issue.  You can easily solder these materials, probably good enough for 15 psi, or move up to silver solder or brazing.

Use of 3D printing has many issues.  Most extrusion printed 3D parts are pretty porous and you will have to come up with some way to seal them.  It can be done but finding sealants that are compatible with the plastic, can get into the pores and then not shrink on setting is a challenge.  Finally the thread question depends on the application.  I have had fairly good success printing threads, but there is a fair amount of surface roughness.  If your threads seal like plumbing threads there will be issues.  If the threads merely provide compression to an elastomer seal, or better yet just hold the part in place while an O-ring gland provides the sealing you should have no problem.

[joeqsmith]

I used to just zip tie a discarded soda bottle with paper towels and holes drilled in the top.  Super light weight.    The only problem I had with it was my newer motors have a lot more blowby and it was a pain to remove and drain. 

My current one uses no filter except at the vent.   I just put a tray under it and drain it out between runs.   Quick and simple. 

[TimNJ]

Thanks for all of your ideas and comments.

So the goal is to simply make a longer version of the cup part?  Is that just for more capacity or for some other reason?  Do you know what material that part is made out of?  I think I've seen clear polycarbonate versions that are pretty long.

Yes...just to make more capacity, no other reason. The original part is cast zinc. Polycarbonate is the more populare type. I chose the zinc version because it would be subject to continuous high heat. I talked to the guy who gave me the drawing and we are working to put together a lower cost kit: http://www.conceptualpolymer.com/

Long story short, I think I'm just going to put my filters up on eBay, and go with his solution.

If you Google for New Jersey Machine Shops, you get a whole lot of hits!

Very true. In today's world, and for something pretty "simple", I figured being local might not even matter...and I didn't want to send dozens of messages to random shops if someone already knew someone who might take on the job.

If you want to do this yourself just substitute brass or copper for the aluminum material.  More expensive and heavier, but material costs won't be the issue.  You can easily solder these materials, probably good enough for 15 psi, or move up to silver solder or brazing.

Use of 3D printing has many issues.  Most extrusion printed 3D parts are pretty porous and you will have to come up with some way to seal them.  It can be done but finding sealants that are compatible with the plastic, can get into the pores and then not shrink on setting is a challenge.  Finally the thread question depends on the application.  I have had fairly good success printing threads, but there is a fair amount of surface roughness.  If your threads seal like plumbing threads there will be issues.  If the threads merely provide compression to an elastomer seal, or better yet just hold the part in place while an O-ring gland provides the sealing you should have no problem.

Thanks for the insight. Yeah, I have no real experience with 3D printed materials for anything other than small mechanical parts or enclosures. On the original assembly, the threads themselves do not do any sealing. As you say, they just provide compression against the buna-N ring on the top.

It would be cheaper and easier to just purchase an automotive oil catch can already made similar to this:
https://www.amazon.com/dp/B06XK9PTP7
From my experience, coalescing filter elements have too fine of filter passages that would clog quickly with engine crankcase fumes and the replacement elements are really expensive.  I have used them on compressed air lines and soon discovered that the only way to economically use then was to install it after a standard filter/separator then a desiccant unit.

Well....you see, I was going to pick up one of these cheap tanks, and then I got sucked down the rabbit hole of believing that they are "not good enough" or at least "could be better". I read one too many anecdotal Amazon review saying "didn't do anything!" and I sold myself on a more elaborate solution.

What you saying about the coalescing filters is right in line with what Dave@ Conceptual Polymer has found. Now, he recommends a lower density particulate filter, and better yet, a particulate filter after a even lower density stainless/bronze mesh filter.

I used to just zip tie a discarded soda bottle with paper towels and holes drilled in the top.  Super light weight.    The only problem I had with it was my newer motors have a lot more blowby and it was a pain to remove and drain. 

My current one uses no filter except at the vent.   I just put a tray under it and drain it out between runs.   Quick and simple. 

Oh wow, that's a bigass catch-can...I suppose you made that yourself?

[joeqsmith]

Well....you see, I was going to pick up one of these cheap tanks, and then I got sucked down the rabbit hole of believing that they are "not good enough" or at least "could be better". I read one too many anecdotal Amazon review saying "didn't do anything!" and I sold myself on a more elaborate solution.

I just have this picture now of some snake oil salesman claiming a bunch of horse shit about the purpose for it.  More horse power, better millage, improved performance.....  Some idiot buys into it and then you get the review, it didn't do anything....   

Its in the rules and required by the tracks.  You don't want to spread oil around causing down time.   

I used to just zip tie a discarded soda bottle with paper towels and holes drilled in the top.  Super light weight.    The only problem I had with it was my newer motors have a lot more blowby and it was a pain to remove and drain. 

My current one uses no filter except at the vent.   I just put a tray under it and drain it out between runs.   Quick and simple. 

Oh wow, that's a bigass catch-can...I suppose you made that yourself?

Look at the catch can on a Top Fuel dragster.   Now those are big!   Yes, the can is home made to fit where there was room.  It holds about a pint which is plenty for my setup.   There's a baffle built into the can (used to be paper towel in the soda bottle) but the only filter I have is the vent, just to catch any mist.  Everything has a place and there is little room wasted.   

What are you doing that requires it?   What are you driving?