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  1. #1
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    Question 45 degree slot through aluminum rod

    I have a need to put a 1/8" slot/channel through a 1/2" aluminum rod across a 90 degree arc. I need downward pressure on the rod to rotate the rod 90 degrees, so a pin holds the rod through this slot such that as the rod slides down, the rod will spin. Picture drilling a hole through the rod from 0 degrees to 180 degrees, then moving down the rod a distance equal to 1/4 the circumference, rotating the rod and drilling a second hole. Now picture connecting the two holes to make a slot/channel.

    I proto'd this with wood, and did this by marking at 0 and 90 degrees as outlined above, drawing a line between the marks, and using the drill press with a wood bit, then slowly walking the rod through that line. With metal, I'm assuming I'll need to make multiple shallow cuts, like you'd do when making a channel with a router through a piece of wood. Also, I'll need to make more than one of these cuts, so with that in mind, I am looking for some mechanism to make the travel of these cuts repeatable.

    I am thinking to use a drill press with a machining bit, but how to hold and move the rod?

    What would be really great would be a cross-slide vise that not only moved the work in the horizontal, but rotated the rod at the same time with a 1:1 ratio. Anyone heard of such a thing?

    The other option would be to build something custom. My first thought is to take a page from a lathe, and using a drill or lathe chuck that holds the 1/2" rod, put a fin on the shaft at 45 degrees to run against a rigid guide, then use a screw on the end to replicate the motion of the cross-slide. Another possibility might be to put threads at 45 degrees on a rod that can couple to the 1/2" project, then screw those threads through a matching nut. Anyone heard of anything with threads that course? Some sort of clamp assembly maybe?

    Hmm, I wonder if a corkscrew would work? Thinking out loud, clamp a piece of cork, run the cork screw into it, and use that to guide and repeat the movement and rotation on the rod for the cut. It wouldn't be too hard to increase the angle as needed by bending the coils in the screw... I don't love it, I think it'll need to be more rigid, but it feels like it could lead to other ideas...

    There is some wiggle room in this project:
    I don't need to stick with aluminum, but it is for a marine application, so it needs to resist corrosion like stainless steel.
    The diameter of the rod can be different, though it needs to stay under 1".
    The 45 degree cut is arbitrary, but it does need to travel the 90 degree rotation of the rod. I am taking advantage of incidental downward pressure on the rod to allow 90 degree rotation at a point governed by another guide. But, a 0 degree cut, essentially nearly cutting the rod in two, not only doesn't allow reaction to the downward travel, and makes the rod too fragile. Also, if the angle's too large, the rod has to travel too far to get to the 90 degree rotation.

    Thanks for anything you can suggest! Either in design or in the tools to use for the project. Note that I'm DIY on a budget. Something like a CNC is out of bounds unless I just break down and hire out to a shop.

  2. #2
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    Quote Originally Posted by coppertop View Post
    Anyone heard of anything with threads that course?
    Perhaps a high helix lead screw? https://www.abssac.co.uk/p/Lead+Scre...ead+Screws/70/
    Chris

  3. #3
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    Quote Originally Posted by coppertop View Post
    What would be really great would be a cross-slide vise that not only moved the work in the horizontal, but rotated the rod at the same time with a 1:1 ratio. Anyone heard of such a thing?
    To do this, a universal dividing head would be used and have the chuck rotate 90 degrees as it travels along. It would be a nasty thing to do, especially in stainless because it is a narrow but deep slot, but entirely possible. A dividing head would give you the repeatability you are looking for. My preferred way of doing something like this would be to put a pin through the rod and have the slots in the part that it runs in as I would be concerned about the loss of strength in the rod.

    How long is the rod and how many of these do you need to do?

    Michael

    (and welcome to our forum)
    Last edited by Michael G; 5th Jan 2021 at 06:52 AM. Reason: added a bit

  4. #4
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    Quote Originally Posted by jack620 View Post
    Nice find! This is the kind of thing I was looking for!

  5. #5
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    Jack and Michael, thanks for the great replies! Michael, to answer your question, I only need one for the project, but one of my designs has a need for two matched slots along the same shaft, and if I get the overall project working, there's a market to share this device. It's a niche in the fishing market that I've been hunting for a solution to and finally decided to just build something myself!

    I think I've thought up something that I want to try. A rod with a coupler to the 1/2" round bar stock. The guiding rod has a pin through it. I then insert the guiding rod in a piece of PVC pipe with a similar ID to the guiding rod's OD, just enough to remove slack, and of course I can shim materials in there to remove all slack. With this, I can use a mitre block to cut a 45 degree cut in the PVC, which would meet up with that pin. Then, like a bolt-action rifle, I have more repeatable distance and rotation guide. Then I clamp the PVC in a vise rod under the drill press, maybe with a couple V guides to support the project bar. It has the benefit of being cheap and I think I have enough spare parts around to put together at least a proto of that design.

    I'm also eying homopolymer (Delrin) rod of either 1/2" or 3/4" diameter as the project material. Much softer to cut in such an awkward way, and I think it'll be strong enough. I ordered a couple 3' pieces of both diameters this morning. It all comes down to how strong it is once that slot is cut in it.

    Any further thoughts or suggestions on improvements or alternatives are welcome! Both with the original ask and with this potential solution!

    It'll take me a couple days to get back to this project, but if it works, I'll post a reply!

  6. #6
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    This may give you an idea of machining.

    Go to the "Home Shop Machinist" web site look in forums, then general and go to about page 6 looking for a posting done on 16/12/20 titled "Two directions at once". Its a video showing a novel machining process.

  7. #7
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    Is the OP trying to describe a helical slot?
    Gold, the colour of choice for the discerning person.

  8. #8
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    Quote Originally Posted by .RC. View Post
    Is the OP trying to describe a helical slot?
    From what I understand, yes.

    I think a pin in the rod and slot in the sleeve (direction he is now checking) will be more robust though.

    Michael

  9. #9
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    I have a suggestion but it depends on how tight a clearance you are trying to maintain and how long the slot is.

    If you look at a helix from the top it is a straight line. I used this method to make a motorcycle throttle control once.

    I set the piece of pipe up an angle of 45 degrees across the mill table. I then may have machined across the pipe to a depth of half the diameter.
    What I was left with was a helix slot that gave a bit less than 180 degree rotation.

    If I remember correctly the width varied and I did a second one. My memory is a bit fuzzy but when I set it up I think I put a piece of steel as a fence at 45 and clamped it against the fence. I went for less depth (maybe 1/4 diameter) and when I was almost across I left the cutter down, wound the table back to near the start and rotated the pipe using the fence and cutter as a guide. In theory you could keep taking bites and do a full length helix.

    Steve

  10. #10
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    Yes, if I understand the term correctly, this would be a helical slot. I didn't follow Raidy's post with the tail pipe cuts.

    Basically, I think, if you mount the rod with a statically mounted pin through the slot, as the pin travels through the slot, or rather the rod moves along it's length across that pin, the rod will rotate 90 degrees.

    What I'm looking for is a mount to hold that rod such that I can drill through the side through the center of the rod, then place a cutting bit through that hole. Then move the rod horizontally through the cutting bit, rotating as it moves in a 1:1 ratio. A helix of 1:1 slotted through the rod and just long enough to rotate 90 degrees, a quarter turn of the rod.

  11. #11
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    Lots of stuff on youtube about rifling barrels.
    Might give you some idea's.
    John.

  12. #12
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    Thumbs up Baynet Fasteners !

    Hi Coppertop, Guys,

    jv271203erl_04erl.jpgBaynet-fastener.png

    Is this the sort of thing that you are after ?
    Best Regards:
    Baron J.

  13. #13
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    Quote Originally Posted by BaronJ View Post
    Hi Coppertop, Guys,

    jv271203erl_04erl.jpgBaynet-fastener.png

    Is this the sort of thing that you are after ?
    Interesting, those might work as guides when drilling/cutting, but the project would be through a solid rod/shaft. Imagine taking round bar stock and creating a slot in the side all the way through about the length of 1/4 the circumference of the rod. Then imagine the rod is made of rubber, grab each end of the slot and twist until one end of the slot goes through horizontally and the other end vertically, which would now make the slot between the ends twisted at about 45 degrees.

  14. #14
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    Trying to describe something you are trying to make is VERY difficult at times, if you could post a pic or sketch of what you're trying to achieve will get you more direct answers, instead of us guessing what you are trying to do.
    It's a bit like, how long is this piece of string???
    HTH
    Kryn
    To grow old is mandatory, growing up is optional.

  15. #15
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    I was overthinking it. I haven't tried the PVC I mentioned previously, but while I was getting ready to make the V supports out of some leftover 2x4 chunks, it occurred to me to just make the whole thing out of 2x4. Take a 6-12" length of 2x4, use my 1/2" 12" long drill bit to bore all the way through lengthwise to hold the project rod. Then use a 2" or so hole saw to make a "window" in the middle of the 2x4 to expose the rod for drilling, milling, and cutting.

    Now I have a secured support and holder for the rod. All that's left is the guide for the 90 rotation, which is done with a skill saw cut through the top half of the 2x4 at 45 degrees to that bored hole, just deep enough to bisect the top half of it. Now I have the guide for the slotted cut I want to make in the rod. The cut actually would make 180 degrees of travel, so I'd have to come up with some stops to limit that to 90 degrees of travel.

    With that one piece of 2x4, I have a solid support and guide design that I can then secure to the drill press table with a couple c-clamps. I think I like it...

    To hold and push the rod, I'm looking at this coupling. 1/2" ID, 1" OD, 8 set screws. Plus the set screws are 1/4-20, which I have screws all day long in that thread. I kayak fish, and that is very common size for all the little racks and holders and tracks. I take a 3" 1/4-20, replace one of the set screws with it, and now I have my rigid pin to travel through the 45 degree cut. I'd just have to open up that end of the 1/2" hole I bored to 1" to accommodate the coupler. I'd also need to mitre that 45 degree cut above so I can take a couple cuts at it so it's wide enough for the 1/4 inch screw. It's $12, but that'd be the only thing I have to buy.

    This feels like a solid solution and not too expensive!

    Thanks for all the great suggestions. They all came together with just simple fact of having to explain this to others to help me work it all out! i get it working, I'll post a picture or two...


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