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  #21  
Old 03-02-2019, 06:43 PM
Lew Hartswick Lew Hartswick is offline
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Another point needs to be made wrt (with respect to) that word "Tollerences" .
I don't know why you keep referring to it as having many many decimal points. if + or - 1/16 of an inch is close enough for your work just put that down. Just so the guy making the darn thing knows what is good enough Same thing for finish, many could be "as cut" for the edges (for those shown maybe "sawn")
If you are making something, you know what is "good enough", but when you are having someone else doing it he NEEDS to KNOW how good you are THINKING. :-) OK?????
...lew...
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  #22  
Old 03-02-2019, 07:07 PM
Samcord Samcord is online now
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Hey Scootered,

There are a couple of things in your info page that have me worried, but even the conservative Christians (like me) here are generally tolerant and helpful.

We even get into political, religious, grammatical, and social discussions if you are up for that, and not overly sensitive. But that is a different area of the forum.

I haven’t read all the details of this thread, but it seems that the serrations are there for a purpose. Their intended purpose could impact the material choice and specs of the grooves. For example, if it is a handle, you probably don’t want it sharp enough to damage skin. Or if it going to be used in a dirty or dusty environment, you may want to be able to easily clean it out. What is for sure is that if you don’t specify what you want, you won’t get what you need.

But then again, a lot of us can appreciate a good puzzle, and a good guessing game once in a while.
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  #23  
Old 03-02-2019, 09:41 PM
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Quote:
Originally Posted by LKeithR View Post
The standard unit of measure for a machinist is .001"; many orders of magnitude smaller than even 1/32 of an inch.
Actually 0.001" and 1/32" (0.031") are only 1 order of magnitude different.

Quote:
Originally Posted by Ironman View Post
...50050 is ball bearing steel.
Bearing steel is generally 52100.
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  #24  
Old 03-03-2019, 12:23 AM
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Originally Posted by Scootered View Post
You're going to have to explain to me why you think "machinists think that way." I might only be in the 9th grade, but I've seen middle school kids more mature than those machinists. I don't believe that this ridiculous level of 53 decimal place precision is even close to being necessary.

:
One of the rules in today's society is, get it in writing.

Its not uncommon for someone to want something and use the excuse that it is not what I wanted done.
too many people have been burnt by not having an agreement and a drawing is an agreement how a part will be made.

A person who does not have a drawing generally does not know what they want. it is a red flag that the parts will not work the first time.

if the invention does not go as expected the blame can be directed on who made the part.
In the case of no drawing all you have to say is, that is not what I wanted.

And now the machinist has to spend another 8 hours remaking your parts.....

The only protection the machinist has is a drawing, on the other hand it is also a way to make sure you get what you want.
there are people out there that think they are a machinist and only pushed a green start button on a computer controlled machine.
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  #25  
Old 03-03-2019, 01:41 AM
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LKeithR LKeithR is offline
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Originally Posted by Scootered View Post
...Respectfully, my personal experience with many, many little tasks like this one is the exact opposite of what you've said. When I give people any more details than just the absolute barest minimum, they all stop thinking about what would work, and instead think of how to improve the overall final thing. I've seen the exact same thing happen over and over again. Even here, a couple of people stopped reading the entire post I wrote, and only responded to part of it, not answering what I asked, but what they thought I wanted...
Well, I'm afraid I have to disagree. In 45+ years of welding, fixing, fabricating and machining I've seen seen few situations where putting something in context and providing as much information as possible wasn't the best way to go. Let's face it, sometimes the whole project can be redesigned to make it better.

Quote:
...Steel is steel. Unless it's some surgical-quality stainless stuff, or high-strength aerospace stuff, plain old regular steel will do the job...
Unless can be a big word. There are hundreds of different steel alloys, many of which have been developed for very specific purposes. Without more information it's hard to determine which one might be the best. Mild steel will probably be just fine for your needs but there are many possibilities.

Quote:
...So, a plain steel would be fine, as it isn't going to be used on anything but a little piece of wood...
Again, you're probably right, but consider this. Different steels have different machining characteristics. Some are much easier to machine than others. C12L14, for example, is alloyed with minute amounts of lead which makes it very easy to machine; something you have to consider if you're making multiple parts. An alloy like 4340, on the other hand, is tougher to machine but it can be heat treated to pretty high rockwell numbers and it's also very easy to achieve a really nice finish on.

Quote:
...If you'll forgive me for asking the obvious, how does any of that help me figure out how to put measurements on my drawing that make any sense to anyone other than me?
I suppose it really doesn't but seeing the big picture is usually the smartest way to approach a project...
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  #26  
Old 03-03-2019, 03:01 PM
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Originally Posted by Scootered View Post
Could I please start a discussion on how to describe these pieces in a way that they not only make sense to a machinist, but are correctly and properly detailed so that someone could make them if they chose to? That would, ultimately, be the goal. Finding someone to make them for me!

Thanks!!
1. You need a isometric drawing. With sizes and tolerances. And what alloy
steel you want to use. Surface finish, tolerances. Talk with the shop you
want to use and ask what alloys they have laying around. 1018 will likely
be fine but if they have 12L15, I would say run it. Both are weldable alloys.
You want to weld these things not all alloys are easy to weld...

2. You need to have a quantity in mind. It is not uncommon for me to have
a buddy machine parts for my work, I quote, "as many as you cant get from
the bar." Often the steel we use comes in random lengths, could be 11'6" or
12'6", one of the common parts is about 5" long. So we are going to get in
the low twenties for parts that is fine, we pay for what he delivers. Also it is
not uncommon for a part or two to be scrapped in setting up the job. So
you think you should get 24 parts from a bar, you might only get 22-23
parts do to set up.

Tolerances need to be determined around what how that part is supposed
to perform. When welding parts I often used to machine them to have
a .020-.030" loose fit. That kind of loose fit will make a machinist look at
you like you have 2 heads.
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  #27  
Old 03-03-2019, 04:39 PM
Scootered Scootered is offline
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Quote:
Originally Posted by LKeithR View Post
Once you spend a bit of time in a machine shop you will begin to see the difference in precision between wood and steel. Most woodworking projects are lucky if they're made to a 1/16" tolerance; high precision might be 1/32". The standard unit of measure for a machinist is .001"; many orders of magnitude smaller than even 1/32 of an inch.

Essentially that's just the way it is; the way that measuring machined parts has evolved over time. So many machined parts are designed to fit together with very close tolerances: pins in holes, pistons and rods in hydraulic cylinders, pistons in engines, crankshaft to bearing fits in compressors and motors. None of these parts would work if the closest a machinist could make the fit was 1/32 of an inch.

If you spend some time watching Youtube videos, reading and also talking to other people you'll soon begin to see the value--actually the need for tight tolerances. In any case that's the way it is and if you can't learn to comprehend the machinists way of doing things you'll never get a project like this off the ground. I have every confidence that you will but it's up to you to make the effort to learn and understand what you need to know.

The first thing I would do is buy a set of cheap 6" digital calipers. Learn to use them and start measuring things around you and you'll soon see the value of being able to measure in very small increments.

As to your question about the hardness of steel consider this. You're right in that all steel is 'hard' but there are varying levels of hardness. A piece of ordinary mild steel can easily be cut with even a cheap file but there are steels available that can be hardened to the point that the best of files will only skate across the surface when you try to file it.

Stay with it. You will learn. You'll learn a lot. You're young so you have a whole lifetime in which to figure this all out. Just remember that even us old farts who have been doing this for years still find ourselves learning new things on a regular basis. And the best part is that are many of us on this and other forums who would love to mentor someone like you. All you need to do is spend a lot of time listening and asking the right questions...
I used to hate school. And then I ended up with a teacher who sounded like you. She gave examples. Real examples, not just posing a problem and then giving the answer, and asking if everyone "got it" I went from barely passing to honor roll in a year. All because she didn't treat me like a stupid kid. Like you. Thanks.

I actually did go buy a cheap digital caliper. It only measures in two decimal places, but I got some specific measurements off my wood parts, and off the existing pipe. The sign at the store said "1-1/2 galvanized pipe" but when I got it home, it was more like 1.66" pipe. That's 0.16" more, or more than an eighth more. I saw immediately your point about tolerances. Talk about the lightbulb going off...

I still maintain that my pieces (let's call them "parts" from now on, sounds more "machinist-like" ) won't really need any close tolerances like are found on machines, engines, etc. In fact, they won't ever come into contact with each other in use. One will get welded to the pipe, and the other will be bolted on, but there will always be something between them when they're being used. If I were making something that had moving parts, then it would be way different.

Thanks for not sounding like some of the teachers I've had.
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  #28  
Old 03-03-2019, 04:47 PM
Scootered Scootered is offline
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Originally Posted by Whitetrash View Post
I'm just throwing this out for discussion. But, do these pieces have to be steel? You might be able to use aluminum and rough in the curved side with a router. Then finish it with a file and save the cost of machining.
Honestly, I did think about doing them in aluminum. I have another friend who has one of those little forge things he made out of an old propane tank, and we could melt down aluminum cans to pour into a bar shape, and then work them from there. We could even make the mold almost exactly what we needed it to be. Except, I don't think you can weld aluminum to steel. Something about dissimilar metals in contact or something. I suppose I could make a sleeve that fit around the pipe that had grooves on it, and then another hinged part that holds the other side on, and only have to have one wingnut to clamp them together, but then it would be a hugely more complicated project than the way I am planning to do it...

Sorry, I don't mean to sound like a smart ass, but what you suggest is another type of project entirely, and not anything about me doing the one I am talking about.
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  #29  
Old 03-03-2019, 05:57 PM
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Pipe is "measured" by ID (in reality it is more complicated than that); tubing is measure by OD.
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  #30  
Old 03-03-2019, 06:01 PM
Scootered Scootered is offline
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Quote:
Originally Posted by Samcord View Post
Hey Scootered,

There are a couple of things in your info page that have me worried, but even the conservative Christians (like me) here are generally tolerant and helpful.
It's okay. I won't hold any of that against you, as long as you don't try to impose it on me.

Quote:

We even get into political, religious, grammatical, and social discussions if you are up for that, and not overly sensitive. But that is a different area of the forum.
Sadly, no, I'm not "up for any of that", because none of it is relevant to me trying to figure out how I'm going to do this. Thanks anyway. You wouldn't be able to change my mind on any of it.

[/QUOTE]

I haven’t read all the details of this thread, but it seems that the serrations are there for a purpose. Their intended purpose could impact the material choice and specs of the grooves. For example, if it is a handle, you probably don’t want it sharp enough to damage skin. Or if it going to be used in a dirty or dusty environment, you may want to be able to easily clean it out. What is for sure is that if you don’t specify what you want, you won’t get what you need.

[/QUOTE]

I can see that I'm going to get manhandled into giving up the details on what I am making. When that happens, everyone will start either redesigning it to make it better, start telling me how it can't be done, or looking down their nose at it because it isn't necessary. Or, they'll tell me that there are other things out there that will do what I want, without having to go through this, why don't I modify one of those?

It's going to "grab" a small piece of wood. That piece of wood is no bigger than say, 1-1/2" in diameter. The grooves are running perpendicular to the force that will be applied to the wood. One of the two metal parts is going to be welded to a 1.66" diameter galvanized steel pipe, and the other will be attached with bolts that run through the whole thing. Let's see... 1.66" for the pipe. .25: for the first metal part. 1.5" for the wood. .375" for the other metal part. That comes up to 3.785" so I'' have to find some 3/8" machine bolts 5" long, and matching wing nuts. I hadn't thought that far ahead to calculate the length of bolt I'd need.

Quote:

But then again, a lot of us can appreciate a good puzzle, and a good guessing game once in a while.
The only "puzzle" should be about the parts, and how to define their shape in a way that gets across the point that woodworking-level tolerances are good enough for this, and I don't need 47 decimal place accuracy. I would like it to be fairly durable, so that it will last for a few hundred to a few thousand uses. (steel wearing against wood, the steel should win, even with repeated rubbing, which there won't be)

When I finally get it built, I'll put up a video of it being used, so everyone can see that I wasn't some stupid kid.

Fair enough?
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