what is a parabolic taper

pdcue said:
Considerabley more so than analyizing it with a digitizing probe, but
you already know that.

Dale(who has every confidence in Joey)
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I'm not sure where the difficulty is.

I couldn't imagine using a CAM program for outputting code to cut a shaft or butt taper. They can be written in minutes using a calculator or a spreadsheet to get your numbers. If you setup your machine to run in diameter mode it's even easier because the numbers you program are your actual cut sizes.

I think the question about parabolic tapers is whether the curve of the taper actually qualifies as a "parabola". Most likely it doesn't. At least not all of it. I think the main feature behind "parabolic" tapers is that there aren't any straight tapers. They curve or change along the way.
 
I saw a shaft that a guy customized by himself one time. It was about the closest thing to a true parabolic that I have seen. Bell Bottom ferrule and all:grin:

Seriously though, My understanding of It is much the same as some others. most shafts that I see are a combination of straight and curved. From what I've heard or read in the past I don't associate that as being a parabolic. I have pulled a lot of tapers in by hand, and although some have a decent curve in them, they almost always have straight lines in them as well.
 
Take a arc segment out of any circle add a focus point and you have a parabola.A 29 inch segment with 60 foot radius can be called a parabola.

in simple G-code
G01 X0 Y0
G02 X29 Y0 R720.00
instant parabola

compound tapers are better for shafts to hit pool balls.
parabola works good for mirrors focusing light.

Maybe a parabolic shaft will help you see the balls better.

bill
 
vasilios said:
Take a arc segment out of any circle add a focus point and you have a parabola.A 29 inch segment with 60 foot radius can be called a parabola.

in simple G-code
G01 X0 Y0
G02 X29 Y0 R720.00
instant parabola

compound tapers are better for shafts to hit pool balls.
parabola works good for mirrors focusing light.

Maybe a parabolic shaft will help you see the balls better.

bill
Click to expand...

Its been a few years since I was fooling around with G-Code, but what you just programmed is an arc, not a parabola.

What do you mean by the word "focus point"? I haven't seen that in the G-code references for G02/G03, or otherwise?
 
parabolic taper

iusedtoberich said:
Its been a few years since I was fooling around with G-Code, but what you just programmed is an arc, not a parabola.

What do you mean by the word "focus point"? I haven't seen that in the G-code references for G02/G03, or otherwise?
Click to expand...

Beat me to it. An the confusion continues. Darn you DPK.
 
Focus point is definelty a mathematical entity of parabolas. You can see it on the wiki of parabolas. But to the best of my basic g-code knowledge (I hand coded probably 15 cnc metalworking projects 10 years ago), its not part of the g-code language.
 
RBC said:
I'm not sure where the difficulty is.

I couldn't imagine using a CAM program for outputting code to cut a shaft or butt taper. They can be written in minutes using a calculator or a spreadsheet to get your numbers. If you setup your machine to run in diameter mode it's even easier because the numbers you program are your actual cut sizes.

I think the question about parabolic tapers is whether the curve of the taper actually qualifies as a "parabola". Most likely it doesn't. At least not all of it. I think the main feature behind "parabolic" tapers is that there aren't any straight tapers. They curve or change along the way.
Click to expand...

This makes the most sense to me. It would be relatively easy to program a true parabolic curve by using a spreadsheet to generate the x,y values for short linear moves. You can also draw a parabola in a CAD program, and then use your CAM program to generate the G-code from the geometry. I never got into CAM (I stopped at hand-coding G-code), but my understanding of CAM packages is that they convert all the geometry from your CAD program into short linear moves.

So the question remains, does the cue maker who uses the term "parabolic taper" do any of the above, or are they very loose in their use of the word parabolic to include a taper with zero straight sections?
 
AtLarge said:
Paul, what do you mean by your last sentence? A straight-tapered butt is a truncated cone, right?
Click to expand...

I wasn't clear. I was referring to a butt section that had a portion such as the front section that when placed flush on top of a straight edge would show an arc of light between the tip of the front and the rear of the front. If it was a straight taper there would be no arc or any light at all. Yes, all cues are some version of truncated cones.

My cues use a compound taper which is composed of a steeper taper from the joint to the front of the wrap and a lesser taper from the front of the wrap to the butt cap end of the cue. If you place the handle section of one of my cue butts flush onto a straight edge, the joint will not touch and if you place the front flush on the straight edge the butt cap won't touch. What I and some other makers use is two straight tapers that change at the front of the wrap.
 
Those makers who use cnc to cut there shaft profiles basicly are playing connect the dots. If you were to cut to that same profile on a harder material like say aluminum, when viewing the shaft from the end down you could most certainly see the faceting.
 
Canadian cue said:
Those makers who use cnc to cut there shaft profiles basicly are playing connect the dots. If you were to cut to that same profile on a harder material like say aluminum, when viewing the shaft from the end down you could most certainly see the faceting.
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So what? A CNC works in principle by "connecting the dots". Its all about how close those dots are together to determine how smooth the resultant cut is.
 
what

Getting off track, but most metal taper bars or taper set ups are cut on cnc mills. It's a matter of how many arcs/lines you want to cut. Most cnc mills
have minimum inputs of .0001. So if you wanted to, you can mill just about anything you can draw. But they are still lines and arcs, just a whole lot of them.
 
iusedtoberich said:
So what? A CNC works in principle by "connecting the dots". Its all about how close those dots are together to determine how smooth the resultant cut is.
Click to expand...

You are absolutely correct, I wont argue that. My point was that technically speaking, a manual tracing attachment following a bent bar as I showed in my first post. Will more accuratly replicate a parobolic curve. Having said that I recognize that the difference between the two is very minute and not big deal. The other advantages offerd by cnc far outway this detail but that detail is still a legitimate point.
 
Canadian cue said:
Those makers who use cnc to cut there shaft profiles basicly are playing connect the dots. If you were to cut to that same profile on a harder material like say aluminum, when viewing the shaft from the end down you could most certainly see the faceting.
Click to expand...

Canadian,

Technically you are correct, but...

As has been stated, you can have points or dots that are very close together, so you would be able to see the facets.

Another thing you have to keep in mind is the cutter radius. If you were tapering with a .031" end mill, then minor changes in planes would be easily visible. However, if you were to use a 2" slot cutter then those changes all get blended together. So much so that you have to account for tool radius if you want to hold very exact tolerances on radius cuts.

Taper bars are great, but just keep this in mind. If you want a taper bar that is very exacting in tolerances, then it almost certainly will be machined with some sort of numerical control. I just don't know of anyone who can control 2 different handwheels at the same time to keep tapers and curves to tight tolerances. They can be scribed and ground by hand, but when you do it that way, tight tolerances are out the window.
 
Canadian cue said:
You are absolutely correct, I wont argue that. My point was that technically speaking, a manual tracing attachment following a bent bar as I showed in my first post. Will more accuratly replicate a parobolic curve. Having said that I recognize that the difference between the two is very minute and not big deal. The other advantages offerd by cnc far outway this detail but that detail is still a legitimate point.
Click to expand...

I understand what you are saying. Its like the viewpoint that analog music is more "pure" than digital.

Question about your picture of the taper bar (note, I'm not a cue maker, but did repairs for several years and have a full wood shop, and worked as a machinist, so I have a fair amount of general machining knowledge). How do you know the settings of your taper bar produce a parabolic taper?
 
iusedtoberich said:
I understand what you are saying. Its like the viewpoint that analog music is more "pure" than digital.

Question about your picture of the taper bar (note, I'm not a cue maker, but did repairs for several years and have a full wood shop, and worked as a machinist, so I have a fair amount of general machining knowledge). How do you know the settings of your taper bar produce a parabolic taper?
Click to expand...

My taper bar is a ground and "bent" flat bar, the bend is guided every two inches. My taper bar was not machined, if it were RBC's point would be valid. There are no truely straight lines in my taper bar. It is like a bow.
 
Just so it is clear, I am not saying my settup is superior to cnc. It is just a simple way of producing a parabolic curve. If I had a cnc setup I most certainly would use it. If I was asked to replicate a taper with exact dimensions, the cnc would be the best choice. I was only making the point that a simple bent bar replicates a parabolic curve better than a cnc program with a dozen points. Which most makers are using. I use cnc everyday at my job so I am well aware of its capabilities. I plan on having cnc at home but have not had the time to build one as of yet. I am not sure if my posts come off wrong, but if they offend anyone I do opologize. This is not my intent. I am a person who loves a good debate so I tend to be argumentative.:grin:
 
Canadian cue said:
My taper bar is a ground and "bent" flat bar, the bend is guided every two inches. My taper bar was not machined, if it were RBC's point would be valid. There are no truely straight lines in my taper bar. It is like a bow.
Click to expand...

Mine's much simpler.
One angle yeah long and one angle yeah long.
I learned it by writing G-codes manually and from so many cuts and cues and finally decide I want yeah forearm that fat and yeah handle that fat.
I used to " feather " the pivot. Not anymore.
Just made it much simpler.
5 angles on shafts do it for me.
 
Canadian cue said:
Just so it is clear, I am not saying my settup is superior to cnc. It is just a simple way of producing a parabolic curve. If I had a cnc setup I most certainly would use it. If I was asked to replicate a taper with exact dimensions, the cnc would be the best choice. I was only making the point that a simple bent bar replicates a parabolic curve better than a cnc program with a dozen points. Which most makers are using. I use cnc everyday at my job so I am well aware of its capabilities. I plan on having cnc at home but have not had the time to build one as of yet. I am not sure if my posts come off wrong, but if they offend anyone I do opologize. This is not my intent. I am a person who loves a good debate so I tend to be argumentative.:grin:
Click to expand...

No offense taken, I have enjoyed this thread. But the question, regardless of if you use a manual taper bar, or a cnc, or a knife to whittle the shaft:

How do you know your taper is parabolic? A taper with no straight sections does not mean its parabolic. That's the crux of the question, IMO.
 
parabolic taper

If I would have to use a manual taper bar, I would definitely use one like
Canadian Cues. I would think it would be easier to tweak than a milled bar.
Both cnc and taper bar can cut excellent shafts. No difference in the quality coming out of the machine.
Once you have cutter style /rpm/ and feed rate figured out, the finished product is the same. As a 1 man shop,
I use CNC for it's flexibility and start and forget capabilities. I have different tapers for different customers.
Cnc makes that really easy, but it could be done with multiple taper bars.
 
iusedtoberich said:
Its been a few years since I was fooling around with G-Code, but what you just programmed is an arc, not a parabola.

What do you mean by the word "focus point"? I haven't seen that in the G-code references for G02/G03, or otherwise?
Click to expand...

I did not say the term focus point is in the g-code language.you can take a arc and determine the parabolic focal point.the center point end of the radius is not the parabolic focal point.

bill
 
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