Best method to taper 3/4 rod to 1/2 over 30
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    Default Best method to taper 3/4 rod to 1/2 over 30

    I need to make a batch of 300-400 spindles for a custom stair Im building and cant find an off the shelf part that works with the design. I need to taper 3/4 1018 bar down to 1/2 over about 30. Because of the slope of the stair Ill need two different angles as the taper length changes coming down the stair and I want to keep the start abs stop details the same. In an ideal world I could control taper as needed (turning) vs ridged tooling (forging/swaging)

    Ive though about forging these with a power hammer, but need a more machined surface finish.

    What kind of equipment make the spindles at a place like Julius Blum or King Architectural?

    So far the processes Ive come up with are

    Cnc lathe with some sort of steady rest to turn the taper abs then clean up the steady rest area as a second op with custom jaws to hold taper

    Manual lathe with offset tail stock and steady rest to machine taper. Same second op as above

    Large swaging machine, I do t know enough about the process to know what involved or what type of tooling is needed to get such a long taper.

    I know similar sized and shaped parts are made and sold so feel there has to be a better process than turning. When I get in the office later today Ill try to post a link.


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    Quote Originally Posted by Whetstone View Post
    I need to make a batch of 300-400 spindles for a custom stair I’m building and can’t find an off the shelf part that works with the design. I need to taper 3/4” 1018 bar down to 1/2” over about 30”. Because of the slope of the stair I’ll need two different angles as the taper length changes coming down the stair and I want to keep the start abs stop details the same. In an ideal world I could control taper as needed (turning) vs ridged tooling (forging/swaging)

    I’ve though about forging these with a power hammer, but need a more machined surface finish.

    What kind of equipment make the spindles at a place like Julius Blum or King Architectural?

    So far the processes I’ve come up with are

    Cnc lathe with some sort of steady rest to turn the taper abs then clean up the steady rest area as a second op with custom jaws to hold taper

    Manual lathe with offset tail stock and steady rest to machine taper. Same second op as above

    Large swaging machine, I do t know enough about the process to know what involved or what type of tooling is needed to get such a long taper.

    I know similar sized and shaped parts are made and sold so feel there has to be a better process than turning. When I get in the office later today I’ll try to post a link.


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    Send it to a swiss shop.

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    Quote Originally Posted by digger doug View Post
    Send it to a swiss shop.
    30" long Digger.

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    Quote Originally Posted by camscan View Post
    30" long Digger.
    Doable. Probably leave some witness marks that would need to be buffed, but doable. A 32mm machine has a stroke of over 12.5".

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    Rifle barrel mfgs have a traveling steady rest that follows the contour as the barrel is tapered. I think barrel mfgs are real busy right now but you could check with a few.

    Ed.

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    Quote Originally Posted by atex57 View Post
    Rifle barrel mfgs have a traveling steady rest that follows the contour as the barrel is tapered. I think barrel mfgs are real busy right now but you could check with a few.

    Ed.
    Thats a good idea, Id be really Curious to see how they move the follower with the taper

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    I think I would start with 12;14, we used to make shift levers from 5/8 dom tube with a .188 hole from 5/8 to 3/8 od from 6" to 30" in length, kind of like this video, the dom tube was gummy, 12l14 would be more fun. The overarm we made was much heavier and had 3 sealed roller bearings on it.

    Turning a Long Taper

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    Quote Originally Posted by kustomizer View Post
    I think I would start with 12;14, we used to make shift levers from 5/8 dom tube with a .188 hole from 5/8 to 3/8 od from 6" to 30" in length, kind of like this video, the dom tube was gummy, 12l14 would be more fun/

    Turning a Long Taper
    I need to be able to weld after machineing


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    Stressproof welds fine and turns better than 1018

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    Quote Originally Posted by TeachMePlease View Post
    Doable. Probably leave some witness marks that would need to be buffed, but doable. A 32mm machine has a stroke of over 12.5".
    Yup, and take out a sub tool, and put in a long support tool.

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    Quote Originally Posted by Whetstone View Post
    That’s a good idea, I’d be really Curious to see how they move the follower with the taper
    This has been covered before, check the archives, it still might be there.
    IIRC W&S made a box tool attachment that the tool followed a template,
    and IIRC the rollers were set ahead of the cut (constant dia. at that point)

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    Quote Originally Posted by Whetstone View Post
    I need to be able to weld after machineing


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    I have tigged a lot of 12L14. It is easy to weld. The welds may not have the tensile strength of comparable “weldable” steel but they are also not going to just be crap and will look like any other tig weld. Just for kicks try tigging a 3/4” bar to a 1/4 x2” flat bar. Then put the flat bar in a vice and try to break the weld. Good luck. So, for stair balusters, the welded 12L balusters will be a 100 times stronger than the common wood balusters used successfully for the last couple of thousand years.

    Denis

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    could a job like this be set up on a cylindrical/universal grinder? I have zero experience with either so excuse my ignorance

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    Live tooling, shaft between powered centers, on a planer.
    Seriously.

    If it needs a non-linear contour, either the tool can be set above/below/askew to the center of rotation (including raise one of the centers)say for hyperbolic curves. Or the center set can be mounted on a swivel plate with pattern edge attached, that follows a large dia follower on the planer column.

    Well that's how i make pool cues.
    Have sometimes speculated about doing it in stainless.
    Probably would require contriving a balanced steady in the middle. Or do half, in 2 set ups.

    smt

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    Ive done some research this morning and it seems like a rotary swagger will do it in about 30 seconds with the right tooling.


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    Quote Originally Posted by Whetstone View Post
    I’ve done some research this morning and it seems like a rotary swagger will do it in about 30 seconds with the right tooling.


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    That's what I have seen done in Furniture places.

    On the welding side, even if you do 12L14, it would still silver solder or braze just fine, no?
    Compared to the strength of wood glued in to wood, they should do just fine!

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    Quote Originally Posted by trevj View Post
    That's what I have seen done in Furniture places.

    On the welding side, even if you do 12L14, it would still silver solder or braze just fine, no?
    Compared to the strength of wood glued in to wood, they should do just fine!
    I've silver soldered plenty of 12L14 parts and it solders just fine, of course. But, for this assembly I would definitely weld it.

    Assume the balusters are to be fixed between upper and lower flat bars and guess the bars will be 1/4" thick. The quickest and neatest welds would be done by turning, say, 3/8" dia spigots 1/4" in length on each end of each turned baluster. Then drill the flat bars to which they are attached with correctly spaced 3/8 through holes. Assemble the balusters in the flat bars and tig the spigots on the "hidden" side of the bar where they come flush with the bar. No filler is needed. Just develop a puddle and proceed around the perimeter of the spigot. Each one will take 10 or 15 seconds. The welds will be plenty strong and hidden. Will they pass a formal welding inspection? Nope because leaded steel is not strong enough for highly stressed parts. But will they be many times stronger than needed for this application. Yes, indeed.

    Optionally just weld an exposed fillet. If you have decent torch skills the welds will look very workmanlike and will be attractive in their own right.

    Soldering or brazing would make a strong neat joint too, but would take me a lot longer.

    Denis

    Added: The spigot method will work on the horizontal portions of the railing. On the inclined (stairs) portion. to hide the welds, full diameter angled through-holes would have to be cut, After welding the excess could be sliced off with an angle grinder or room included in the wood mounting areas to accommodate the protruding parts of the baluster shoulders.
    Last edited by dgfoster; 05-26-2021 at 07:11 AM.

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    Quote Originally Posted by Whetstone View Post
    I’ve done some research this morning and it seems like a rotary swagger will do it in about 30 seconds with the right tooling.


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    Some commercially available contoured spindles I’ve gotten (made in Spain from Archetectural Iron in NJ?), were fairly thin wall tubing probably rotary swaged, but you want solid I’d think? I think They also need dedicated dies, so are really for volume production.


    Obviously a Swiss is going to be a pricy option just considering machine time (for a stair component), and a lot of Swiss shops would probably consider this a pain in the ass job, so would price accordingly?

    If you have a decent lathe and someone to run it, and it makes sense time and dollar wise, the offset tailstock might work. The follow rest config is the aspect that might suck.( doing a little searching, turned up a post that mentioned a barrel maker that supposedly used a lead weight and lever to keep the follow rest in contact! Also, pneumatic options… interesting.)

    Otherwise CNC, a shop with the follow rest solution Kenton linked to sounds promising.

    cylindrical grinders are for .0002” precision, way too slow and expensive. Unless you want the precision?

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    commercially, at places like King, these are all forged.
    the typical tolerances for ornamental iron do not justify the cost of turning on a lathe, in most cases.

    a blacksmith who does these will either free hand them, with a small amount of artistic variation, or make a big die, and do it on a big hammer. In both cases, experience and practice, along with the right equipment, make all the difference.

    Call up the guys at the Center for Metal Arts, in Johnstown, and get a recommendation. There are a ton of capable industrial level art blacksmiths within a half days drive of you.
    https://centerformetalarts.org/


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