Suggestions on How to Mill a -6 AN fitting for Braided Steel Hose

[flyinphill]

I have a part that I am looking to manufacture, but I am not sure the best way to go about making it. The part is a fuel rail for a fuel-injected motorcycle throttle body. It needs to have 2 male -6 AN threaded receivers on it. The thread part is easy, a thread mill will do this job nicely. But my problem is how to machine the 37 degree taper that makes up the sealing surface. This is not a common angle that you can easily find a tapered end mill. And even if you could, it needs to be a very smooth, continuous surface to seal properly. I doubt that circle milling would give a good enough blend to acheive this.

I have seen several fuel rails from other companies that have done this very task, and the taper on their parts looks perfect, almost like it was done on a lathe. But the design tells me that there is no way it was done on a lathe, it had to be completely machined on a mill. So does anybody have an idea how to do this? Is there some type of tooling designed to act like a boring head, but creates the shape of a cone?

[Mitsui Seiki]

It can be done with a surface.

[flyinphill]

Do you mean produce a 3D surface, and machine it with a ball mill? I never really considered doing it that way, but I guess it would work. But I still don't think that is how the others that I have seen were done. The surfaces are just too smooth to have been done that way.

[mc-motorsports]

You can't just make a female thread and screw a fitting in?
I would't use a ballmill, you'll never get a good sealing surface. Maybe just make a 37* tool out of HSS and use a boring head and just plunge.

Can you post a pic of a similar TB with the built in fitting? You said other companies make them similar, would help to have a visual.

[Mitsui Seiki]

Originally Posted by flyinphill Do you mean produce a 3D surface, and machine it with a ball mill? I never really considered doing it that way, but I guess it would work. But I still don't think that is how the others that I have seen were done. The surfaces are just too smooth to have been done that way.

Yes,That's exactly what I mean.
You can get a very smooth surface if you do it right.
If you don't do it that way I think you need a custom chamfer tool.
Seco tools can make on for you.Minimasters.
http://ecat.secotools.com/

Click on Milling and then Minimaster.

[Caprirs]

I would contact a local tool maker and have them grind a piece of carbide to the correct angle. In fact, have them grind the tool shape on both ends of the carbide blank. They should be able to do this for $50-$100. If you're making the fittings from aluminum, that tool will makes thousands of fittings before needing to be re-sharpened.

If you're making one fitting from aluminum, then the ball end milled surface would likely work as the aluminum is ductile enough to get a decent seal for typical fuel pressures (~40psi).

[tstom]

I would try starting with a carbide drill mill and have it ground to a 75 deg (JIC flare is acutally 37.5 deg )included angle I think with a circle mill or contour tool path using lead in and lead out with overlapping end points would be plenty smooth you could also leave .010 or .02 for a finish pass
As one of the previous posters said you could make a lot of fittings before the mill dulled

You could get it smooth enough with a ball mill and a small stepover...say .005" but it will take a lot longer if ou are making more than one part

[wms]

Good chance they where cut with a custom "Hollow Mill".


http://www.geneseemfg.com/geometries/taperspoints.php

[Geof]

Have you tried contacting tooling suppliers. I don't have the links available, but I have seen catalogs listing tools ground for doing all the standard hydraulic connections like ORB. Flare fittings are very common and I would expect the tooling is available off the shelf.

[Delw]

Originally Posted by flyinphill I have a part that I am looking to manufacture, but I am not sure the best way to go about making it. The part is a fuel rail for a fuel-injected motorcycle throttle body. It needs to have 2 male -6 AN threaded receivers on it. The thread part is easy, a thread mill will do this job nicely. But my problem is how to machine the 37 degree taper that makes up the sealing surface. This is not a common angle that you can easily find a tapered end mill. And even if you could, it needs to be a very smooth, continuous surface to seal properly. I doubt that circle milling would give a good enough blend to acheive this. I have seen several fuel rails from other companies that have done this very task, and the taper on their parts looks perfect, almost like it was done on a lathe. But the design tells me that there is no way it was done on a lathe, it had to be completely machined on a mill. So does anybody have an idea how to do this? Is there some type of tooling designed to act like a boring head, but creates the shape of a cone?

Do you have a picture of what you want?
Surfaceing will give you a very very nice finish on a part that small it won't take long to run but you will have a long program. so DNC or lots of memory is needed.

Most Fittings are done on a lathe then put onto the pipe and the flare is made, I've made literally milions of AN fitings for many different applications.
on tight fitting spots were it is hard to flare , you can buy a cheap flaring set and grind or mill down the tool so it fits on the pipe, I have cutdown and made flaring tools for clearance as little at 1/8 on tight bends.

Remember that AN fitting MUST spin on the pipe/hose other wise you won't be able to get it on your application.

if the Application MUST be made on a mill there is a few things you can do. cut the angle with surfacing then get a small motor even a drill motor will work.
lock the drill into place some how lock the AN assembly into place somehow( vise's) then get a vacumm cleaner belt and hook the drill chuck to the fitting
turning on the drill chuck will spin the fitting, then take light sand paper and wd-40 and light clean up the surface..

This also works for redoing old antique asemblies that you dont want to cut off. I olny done this for my own projects in the past. Never on a production level.

A drill with a chuck and a vacum cleaner belt are really handy at times.

[flyinphill]

The hollow mill looks like what I had pictured in my mind to do this. And as someone said, AN flare fittings are very common , so I would expect that tooling for them would be a fairly common production part. But to this point, I have been unable to find it in an off-the-shelf tool. But then, I am not really in contact with a lot of specialty tool makers.

My business is primarily in the high performance engine department. I have a 3-axis mill that we run maybe one day a week to make various small-run parts. We used to farm them out to other machine shops, but I have experience in the CNC business, and we decided to just bring as much stuff as possible in-house. As a result, I don't have tons of tooling like a typical CNC shop that had been in business for many years would have.

Also, this would be a low production part, maybe only a few dozen parts at a time. We do very specialized work for serious racers, so we just don't have a huge market for our parts. That is one of the reasons we bought our own machine; shops just didn't want to mess with the small productions we needed. But the small production numbers also make it cost-prohibitive to buy a really expensive tool to make these parts. That is why I asked on this forum, and I have gotten some good suggestions, and I still welcome additional ideas.

BTW: I will take a picture and post it up so that you can see what I am talking about doing, but it might be after the holidays before I do it.

[jstiltner]

Having not seen the part I could be very wrong on this one, but I would go with the simple drill and tap a hole, then use a commodity fitting in it. This would make the surface sealing quite trivial, and would allow the racer to replace the fitting if it was damaged by frequent fuel line removal, or any other number of reasons. Or sell it as having say 5/8" npt hole, and let the user decide on the fitting themselves.