Help with reading drawing units

[cso]

Our teacher gave us this drawing with no explanation and I could really use some help interpreting the dimensioning before I start.

 

1) What does RC-3, RC-5 and B.C. stand for?

There are 6 small diameter circles. On the bottom of the drawing it says "6 X R12", and then just to the right, it says "RC-5 6 X (Dia) 8 thru evenly spaced on a (Dia)100 B.C." It seems contradictory and makes no sense to me.

 

2) What is the Diameter of the center-most opening? 34? or is that the diameter of the outer part of the 4 notches?

[kencaz]

RC stands for Running Clearance and is used as a tolerance for bearings shafts and sliding parts.

 

B.C. They want 6 holes at a diameter of 8 evenly spaced on a 100 Dia Bolt Circle...

 

The 6X R12 if you look close the arrow is pointing at the outside radius and not the hole...

 

KC

[cso]

KC, Thank you, that helped a lot. As a follow up, is there an easy way or preferred way to make the small teeth along the 82 Diameter round? I understand the array command, but how would you actually cut in the teeth? Should I have done that at the beginning before I extruded everything? And, as a follow up to that can you array along a curved edge like the outermost part of the object?

gearhw4-19.dwg

[ReMark]

Personally I don't think those are teeth. I think it is "artistic license". If they wanted you to put teeth on an object they would have given you a gear to draw.

[JD Mather]

... way to make the small teeth along the 82 Diameter

 

I don't think those are teeth - artifact of the resolution of the image. Notice there is also stair-stepping along outside edge and lines for "shadows". And there are no dimension specification for teeth. My conclusion - those aren't teeth but a graphics resolution problem.

[ReMark]

I just opened my copy of Spencer's Basic Technical Drawing (see page 251) and I see the same conventions used. It appears as though the draftsman has placed a series of closely spaced lines to denote a "soft" edge (I can't think of another term at the moment - sorry). I see them used where both curved and/or straight lines would normally appear. Again, I think it is artistic license that has been taken with the images.

[MikeScott]

A "Soft edge" as opposed to an "outside edge" of the part as per this image.

 

It took me a moment to realize that was a projected collar rather than hidden lines showing something on the other side of the part.

 

Update.. likely a "broken" edge to indicate that the edges aren't sharp and need to be chamfered or rounded slightly.. probably the unmarked R2 marked at the bottom (as I'm not spotting any unmarked radii, and that's a pretty small radius)

[JD Mather]

... or rounded slightly.. probably the unmarked R2 marked at the bottom (as I'm not spotting any unmarked radii, and that's a pretty small radius)

 

I agree - representing the fillet - definately not teeth.

[ReMark]

I knew someone would provide the correct terminology. Thanks Mike.

[Dana W]

Eased, or relieved, if an operation is to be performed on an edge.

 

The woodworker part of me would merely run some 220 grit along those edges with a fingertip rather than a sanding block to ease them.

 

If the edges of a machined part were to be relieved there would be note for it. Otherwise, it may be just a way of showing an unprocessed soft outer edge or fillet at the inside corner on a cast metal billet.

 

As long as we're talking proper terminology...

It always bothered me a tiny bit that AutoCAD has taught people that a fillet can be found on an outside edge, when in fact they can only be found in inside corners. But, to correct that, they would have needed two commands, Fillet and relief.

[MikeScott]

Well, for the record, the terminology in our shop for machining metal is to "break the edge", meaning to break the edge away from being a sharp, true 90-degree surface that can cut you.. for safe handling purposes.

 

I've heard them use "releived' interchangibly as well, but we have a sheet metal shop, so when you start talking releived edges, people start thinking about relief cuts for bends.

 

Fillet, to me, always made me think of fish. I used to think it referred to taking the spine out of a corner, and used to pronounce it accordingly.

[cso]

Thanks everyone, I am enlightened once again! And, I have another question. I feel like a pain, but here goes. For the same drawing I am having trouble dimensioning it as shown. I tried moving the UCS to different locations including the center, the center pulled away from the drawing and the top of the circle, but the units seems to snap back close to the drawing and are not represented as shown. And, the leader line is not pointing to where I want it. Is there a "Dimstyle" setting I should be adjusting?

[ReMark]

I'm not sure I understand the nature of your problem. I threw three dimensions on the gear and ended up with this:

 

 

What happened to your arrowheads? Did the Apaches steal them?

[cso]

Lol, I'm not sure what the problem is either. In all of my other drawings I have been able to dimension a radius/diameter as you show it. All, I can think of is that I have a setting or settings set incorrectly. When I dimension it, it won't pull the dimension out away from the drawing, or show it between two lines. Or, the leader line gets hidden. It just has one leader and that always is bent when it first comes up and then when I push enter it snaps next to the object, and won't necessarily be pointing to the correct circle, but it does have the correct diameter. I did get the arrow to show, by changing the arrow size. I'll just keep trying different settings. Did you have to change the UCS location to get it to show? Thanks

[Dana W]

 

Fillet, to me, always made me think of fish. I used to think it referred to taking the spine out of a corner, and used to pronounce it accordingly.

 

Should I start a thread, "Where is the Fillay command? I can't find it, and I got a spline I wanna delete"

[ReMark]

I did not change the UCS position. I merely switched to a SE Isometric view and made sure to use my Osnaps for accurate picks.

[MikeScott]

Should I start a thread, "Where is the Fillay command? I can't find it, and I got a spline I wanna delete"

lol! Sounds like a good sig-line.

 

CSO: Maybe it'll make more sense if you turn off your ortho when you're looking to see what it'll do.. definately use your OSNAPS though, like ReMark said.

[cso]

OK, this is my final post on this object, as I am sure I have reached my quota for this problem! (and yes, I am successfully completing other problems in between!)

I redrew the gear and several other extruded circles to dimension on the attached. (I have my osnaps on and tried ortho both on/off)

 

 

1. The issue I would really like to figure out is: no matter what I do, the Diameter only has one leader instead of the Diameter spanning the circle with an arrow on each end as shown in the original drawing and ReMarks dimensioning. If I can figure this out, then everything else might solve itself

 

2. (pink and yellow gear on left)If I start by extruding the circles out in the positive z direction then the diameter arrows point at the edge of each circle, but on the same plane as the original center of the circle, so in the case of several extruded circles the diameter extension line is hidden.

 

3. (pink and yellow circle in the middle) Now, when the circles are extruded into (-Z), then the center of the circles is on the outside and the diameter arrows are pointing correctly. (good)

 

4. Pink and Yellow gear on the right. The only way I can fix it is if I move each UCS to the center of the individual circles, which seems complicated for a detailed object.

 

5. With my original drawing (gray) I copied it into this drawing and the dimesions are all screwed in the green dimensions, when I try to duplicate the original.

gear5.dwg