Circular Segment - Radius Platen

Sam Salvati said:
Just find a 5' circle and use it to scribe a line :D Wagon wheel rim....55 gallon drum....string and a piece of chalk set to 2.5' from the center to the chalk layine out a big circle is not too hard.
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You were supposed to do this for me Sam... I am still willing to send you my address. haha
 
blindhogg said:
Screw math, let the fancy schmancy program do it for you.
CW

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No Chris, that sets a BAD precedent.
More people NEED to understand how to do this type of thing.
In our parent's and grandparents era, most people could, and we, as a nation, thrived.
I assure you metalworkers could.

And doing the math is faster, guaranteed.
Took me a grand total of 16 clicks, and my hand never left the mouse.
So what is that, less than 20 seconds from seeing the question to having an answer?
I do keep a shortcut to the Windows calculator at the very top of my start menu though.

Understanding basic geometry and trig is critical to modern metalworking.
We can all get there using software, but it take no knowledge or understanding to do so.
More people need to understand what, how, and why.
 
A friend told me this calculation, he uses it for doing arch top windows using the height and width but I forget it right now....

Ryan, if you still want me to do it, I'll start looking for a 5 foot round and do it in 3/8" by 2".

BRIAN IS CORRECT people need to know how to do this
 
my first one befor nate started amkign dsthe killer plattems
first platen made of wood was done with strind and a sharpy as its not the best but it worked fo one or 2 knives
 
We need to prod Nathan into making some more platens...

As far as having the program do the math for you, that works great too, but I typically don't want wash up and go in the house and fire up autocad every time I want to get a dimension. Having even a very basic understanding of right angle trig(soh cah toa and pathagorean) is pitifully easy to learn and retain and is incredibly usefull with the whole knife making thing we got going on here. Too each their own I suppose. I work as a draftsman and typically have autocad or inventor running on my computer and I still use the math for figuring out simple things I want. I'm sure if you talked to most guys in a machinest shop they would give you a similar opinion. A thing I do a lot of with work is make up spreadsheets that use a lot of formulas for This kind of thing that saves me a ton of time. Without the math I would be stuck with hours of layouts or I can put together a simple spreadsheet in 3 minutes and know the value of h for thousands of different platen sizes(if that's what my work called for... )
 
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Alright, alright, I will get my son to walk me through it. The sad thing is I learned all this and have not used it over the last 20+ years. Old Dogs and new Tricks.

Sam I will work it out, I appreciate the offer!
 
Anyone making it to the 9th grade or so is forced to learn it we just aren't given very compelling reasons to retain it. I'm a fairly young guy and even in my own profession that relies heavily on it I'm always shocked at how many of my coworkers are so detached from it. I don't mean it in a judgmental way as I realize this is a hobby for most people here and if people aren't going outside of the box of their own experience(sticking to what they already know, figured out from trial and error) there really is not an incentive to learn. I also understand that some people enjoy a trial and error approach. I personally want to know exactly how high my new 8inch grinding wheel will raise the bevels on a knife grind long before I even purchase it. But I am kind of anal, not that my experience level allows my to show the full extent of my anality(is that a word?) ;)
 
Fellhoelter said:
No Chris, that sets a BAD precedent.
More people NEED to understand how to do this type of thing.
In our parent's and grandparents era, most people could, and we, as a nation, thrived.
I assure you metalworkers could.

And doing the math is faster, guaranteed.
Took me a grand total of 16 clicks, and my hand never left the mouse.
So what is that, less than 20 seconds from seeing the question to having an answer?
I do keep a shortcut to the Windows calculator at the very top of my start menu though.

Understanding basic geometry and trig is critical to modern metalworking.
We can all get there using software, but it take no knowledge or understanding to do so.
More people need to understand what, how, and why.
Click to expand...

I do my calculations in cad too. I have this
books
for when I need to remember how to do them. :)
 
Sam, you're a philanthropist of the highest caliber, but they just don't speak our "booga booga" language.

Did you see the easy, easy technical way? Hell my background is in advanced computing, but I left machochism behind (tounge in cheek) for smithing. :/

Nathan; please stand up!

Canofcorn: no offense brother, but I've got another Daniel Tosh quote for Omahanians that explains your fixation on math; it involves "Storm Chashers" ;p
 
Damn boys, we are all sitting in front of computers with internet connections.
I Googled Circle Calculator, and the 3rd link is this.
http://www.1728.org/circsect.htm

You can find a calculator for just about everything with just a few seconds of searching.

And often, inadvertently learn some new things in the process.
 
Hey guys,

The steel is here (152 pounds of A2), and the cutters are here. I just need the machining center to free up so I can run them. I'm making room in my little shop for another machining center, so I should have something open soon. :thumbup:

Thanks
Nathan
 
canofcorn said:
R angle trig(soa cah toa and pathagorean)
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No to be a dick, but I think the soa part of you post is wrong. If you're saying what I think you're saying it should be soh.
Sin= opp/hyp
Cos= adj/hyp
Tan= opp/adj

Some old horse, caught a horse, taking oats away. Thank you Mr. Kauffmann, 7th grade algebra. He also made us memorize the decimal equivalents down to 8ths between 0 and 1. Best two things I ever learned. Im in the process trying to memorize them down to 32nds, then 64ths.

He always said, if you know the formula, you're halfway there. Now I say it to my kids. I learned more about practical use algebra in 7th and 8th grade than I ever did in high school.

Again, not trying to be an ass, but we need this post to be correct in case someone uses it for reference some day.
 
As blindhog indicated, the chord height for a 10" chord on a 30" radius circle is about .42".

Take a 2X4 board and put a hinge on one end. Put a 10" board as a "T" on the other end, so the total length is 29.5" from hinge pin to "T" surface. Tap the 10"X2"X.5" platen blank for the mounting bolts, and bolt it to the "T" from the back side. Don't worry if the bolts stick out, they will get ground off. Mount the hinge on a saw horse, and set it in front of the belt grinder with a contact wheel on it ( any larger size). Swing it up and down as you move the sawhorse in to make contact and it will grind a perfect 30" radius on the plate. It will take some time and care to repeat this from a coarse belt up to a 400 grit surface, but is doable.


OR - buy one from Nathan.
 
Nathan the Machinist said:
Hey guys,

The steel is here (152 pounds of A2), and the cutters are here. I just need the machining center to free up so I can run them. I'm making room in my little shop for another machining center, so I should have something open soon. :thumbup:

Thanks
Nathan
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I'll drop you an e-mail!
 
stacy wouldnt that make a 60 inch wheel as if the radius is 30 making the diameter 60
a 3 foot wheel lwoudl be 18 inch and a 4 footer 24 9i know cause the first string drawn platten was an 8 footer by mistake
 
Nathan the Machinist said:
Hey guys,

The steel is here (152 pounds of A2), and the cutters are here. I just need the machining center to free up so I can run them. I'm making room in my little shop for another machining center, so I should have something open soon. :thumbup:

Thanks
Nathan
Click to expand...

can i send you a plate of cpm10v :)
 
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