SAE-8 Banjo Fitting Autocad

[tomrscott]

So here's a shot after profiling the radius a bit more, getting ready to begin the second port:

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[tomrscott]

Then I used a center drill to mark the center of the first port sleeve, and drilled it with an 1/8", 1/4", .406", and .5" drills. The first three drills I drilled through to what will be the core of the banjo, but with the 1/2" drill I stopped at 1/2" depth to make a shoulder to stop the tubing.

The profile radiusing is almost impossible to get very smooth by hand. I just don't the proper trig calibration in my hands to CNC it manually. /forums/images/graemlins/smirk.gif The last thing you want to do is to cut too far, so I left it a little big. I will be cutting a similar radius profile at a right angle to this which will allow me to take some of the roughness out.

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[tomrscott]

This shot shows the sleeve bore shoulder-stop for the tubing.

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[tomrscott]

This is a larger view of the drilling setup.
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[tomrscott]

And here's another long shot of the lathe at this setup. /forums/images/graemlins/smirk.gif

Next I will take the part out of the 4-jaw and set it up for the second port sleeve.

 

[tomrscott]

I forgot to take shots of cutting the second port, but of course that would have looked just about like the first port. I got kind of distracted because I had gotten impatient and fed the starting 1/8" drill too fast and snapped it off. Steel is pretty unforgiving of impatience. Anyway, it was just the very tip and I was able to drill past it with the through hole and then push it out with a drift punch (ie: I got lucky).

This shot shows the piece turned flat so I can face it, and drill the 3/4" through hole. I set the piece as flat in the chuck as I could get it, and then cut a clean face. Then center drilled the piece, drilled with an 1/8" starter drill, 1/4", 3/8" 1/2", 5/8", and finally a 3/4". I did a bit of deburring and here it is.

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[tomrscott]

I took this one with the flash while it was cutting the 1/2" hole, you can see the chips peeling out as it spins. /forums/images/graemlins/smirk.gif

 

[tomrscott]

Here's a shot after finishing the 3/4" drill /forums/images/graemlins/smirk.gif

 

[tomrscott]

In this shot you can see that I decided to put some stubby bolts in the braze sleeves to spread out the chuck jaw pressure. With the violence of boring a 3/4" hole, I had to clamp down the chuck jaws real tight and it would have left deep impressions on the braze sleeve ends. This way they came out without a scratch.

This shot is a bit misleading. It looks like the profiling is about done, but the far corners are still pretty rough and will get profiled more in another setup.

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[tomrscott]

Finally a quick deburr with the tool bit that I used to face the piece (forgot to shoot that process).

I've left the whole body a bit oversize on purpose. I can cut it down if I want to later, but I was thinking that since this is a two port banjo, maybe I'd make it a bit oversize inside for increased flow. I would rather cut the inside bore first and leave a little extra beef for now.

I am not trying to follow the print exactly, but having the print handy keeps me from overcutting and it is real hard to "cut it bigger."

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[tomrscott]

This is the latest variation of the Autocad drawing that I am loosely following. It has the dual port, and some additional dimensions that would not be needed for a CNC job, but when doing it by hand, it's handy to be able to measure how far a cut should go or something. I find it useful to have more dimensions than are actually necessary so I don't have to do any calculating at the bench that I might screw up.

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[tomrscott]

Well I played hookey from the homework I should have been doing tonight (taking some business classes at night at the local college to finish a bachelor's degree). But this is way more fun! /forums/images/graemlins/blush.gif

So here's the pics of the rest of the process:

After drilling out the bore to the 3/4" through hole size, I needed to overbore the core. This boring bar is good and stout, but I had to find a broken bit and sharpen a new edge to get one short enough to fit inside the bore, and with the shape I wanted. Doing it over again I would have radiused the corners just a bit, but that's not real critical. A couple things to notice: I left some flats on two sides of the outer body to be profiled later. I knew the drilling and boring would be a lot of torque and wanted the chuck to have a good solid bite. Also you will note the stubby bolts left in the braze sleeves to reinforce them and spread out the chuck jaw forces. This gave me a good deep overbore, deeper than the factory stock fittings, for a little less flow restriction.

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[tomrscott]

A trick I was taught for lineing up a boring bar or anything you want to get in a chuck straight: Grab it with the tail stock chuck while the tool post is loose and will move around, and then adjust the tool post slides to be nicely centered and clamp the tool post down. Now you know it is well centered and parallel with the bore.

Works pretty well for parts too. I wanted to trim up one of the braze sleeves after I had taken it out of the 4-jaw, so I put the sleeve I wanted to work on in the tail stock chuck and then carefully tightened the 4-jaw around the part, being careful to go slow with the jaws and not move the part around. Worked pretty well.

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[tomrscott]

After I got the boring done, I just re-chucked it twice more to finish the outer body profile. This part is real tedious, takes a lot of time, and is never perfect. The pictures make the result look better than it is, but fortunately the profile isn't a functional requirement.

Oh yeah, and I forgot to snap a pic of facing the second face, but gosh it would look just like facing the first face. /forums/images/graemlins/blush.gif

You just have to be careful to get them very parallel so the faces will seal well. The threads will accomodate a few thousandths of out of parallel, but you want to get it as close as you can.
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[tomrscott]

And here's a few shots of the finished product with a factory through bolt. /forums/images/graemlins/smirk.gif

 

[tomrscott]

And one showing the tube sleve bore: /forums/images/graemlins/smirk.gif

 

[tomrscott]

And one last shot with the bolt through it.

Lathe work is a lot of fun, but it takes patience and planning. And it would sure help to have sine and cosine calibrations in your right and left hands for those spherical profiles! /forums/images/graemlins/smirk.gif

 

[Henro]

Tom,

Thanks for taking the time to post all the photos of your work!

Really enjoyed the thread. Always wanted a metal lathe...hasn't happened yet... /forums/images/graemlins/frown.gif

Great job! /forums/images/graemlins/cool.gif

 

[JerryG]

Tom,
Looks like your in business, looks good. Let us see the completed project when you get it all plumbed.

 

[MadReferee]

Nice job on the profiling.

Several years ago I made a mainfold similiar to what you did. I did not do any profiling as I was charging by the hour and the guy didn't want to spend all that much.