A Better Lathe Banjo Pt. 3
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- เผยแพร่เมื่อ 16 ก.ย. 2024
- Part Three of my lathe banjo upgrade project. I had a small issue with the audio, so please bear with me.
Related links & information can be found in the associated blog post here:
www.dans-hobbie...
It's a good project and excellent idea to make up the 3 banjos since that will drastically speed up any changes as you mentioned. A couple of minor points though. That would be a fixture not a jig. A proper definition of a jig is it guides the cutting tool, like drill jig bushings do. A fixture guides or orientates the part in the correct position to the table travel or angled to it like yours was. It's more than common for people to get the two terms mixed up.Since it was a non critical dimension, then scribing lines and setting those true by eye with a parallel laying flat on top of the vise jaws to give you cutting clearance should have been within .005"-.010" if your vision is half decent. Myself I would have clamped all 3 parts together with your Cant Twist's and set them by eye and then clamped in the mill vise. Then face mill one side of all 3 at once. If a bit better accuracy was wanted? Since you know your size at each end and the length of the taper then the taper per inch is easy. Set a indicator on the top of the clamped together banjos, then run the table in the X axis exactly 2"- even the full 6", keep angling the part until your rise or fall on the indicator matches what your calculated taper per inch should be. That way is almost as accurate as a sine bar and your using tooling you already have.
What you did obviously worked well and was good practice, but even setting it almost exactly with an indicator and face milling both sides of all three should have taken maybe 20-30 minutes tops. I used to put a great deal of extra time into fixtures as well, if it's really needed I still do so. But learning some other ways can still get the job done well within tolerance and a whole lot faster sometimes. From a hobby perspective, end mill cutting edges get expensive if you can't resharpen them yourself. If I can face mill the part then that way is a lot cheaper per cubic inch of material removed than endmills are. You need to buy your tool & die maker father a beer, he's obviously shown you a lot of the better methods. I wish I had a proper mentor. Without one it takes a huge number of mistakes and time while learning the basics.
Excellent use of a simple jig set up to accomplish the angle milling. This is one video where I've definitely learned something. Thanks for doing this series.
If you have a couple of pieces of, say, 1/4" flat-bar maybe 1.5 wide and at least as long as the leg of your triangle step-block, just set that spanning the T-slot and voila! a good surface to set the step-block on.
Nice set up. Since the angles aren't critical, you might have gotten by with just sighting in the vise instead of the jig, but nice get some experience in the work holding in case it need it in the future.
To avoid the issue of your hold down block barely straddling the T-slot, you could have laid some parallels (or other metal plate) on their side and then put the block on top of the parallel.
Nice work holding solution.
Seems like you could have also angled the part in the vise with a short pin of the proper size under one side to offset the part at the required angle. Similar to the way one would use a sine bar.
You could also use pieces of scrap to span the T-slot under the triangles.
Great work! What brand twist drills are you using here? They seem to run pretty true and have a real nice grind.
I've been slowly converting over to Triumph Twist Drill, as I really the ThunderBit line they have.
triumphtwistdrill.com
Sine Bar?
I don't own one yet.
Since you've gone to the trouble of making a production jig, are you going to be offering the banjo kit for sale? :)
lol, no way, making these things would put me in the poor house. :-) I do have all the blueprints up on my website though for anyone who wants to make one.
Dan, love your videos but I cringe every time you swipe your hand over a freshly machined part to wipe away the chips.... stock up on bandaids..... lol