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"Grinder Sketch" progress and help sought
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* September 14, 2009, 12:50:59 PM
Hello all.  I posted this originally with a question on how to copy something but it has morphed into more than that so I decided to make a new thread to try to keep the subject line relevant.  Somebody please stop me if this thread doesn't belong here for whatever reason.

I decided to make this drawing for practice and learning how to use TC specifically and CAD generally.  I am enrolled in a class for AutoCAD at my local vocational school beginning in just a few days which will presumably help me get a better grip on the basics (this at the suggestion of a forum member here) but for now I've been using a training CD and help from this forum.

With all that said, here's the progress:  I added a "front" and "side" view of one of the nuts; there are two and the nuts are not the same.  One is left hand thread and the right hand threaded one has a set screw hole in one of the flats, but none of that is shown yet.  I do intend to try to show the set screw in detail but haven't done it yet. 

I drew the side view of the nut that shows two flats as a series of lines.  This I copied after creating a group and placed on the right hand shaft by using vector copy (I had to change the Reference Point to do this).  The second side view (that shows 3 flats) I placed on the left shaft the same way.

The "front" view of the nut shows the major and minor diameters of the screw thread; I wanted to draw a line tangent to the inner circle out to the outer circle to represent the starter thread but I'm not sure how to accomplish this or even if it's the correct way to represent a thread.

I would also like to show the threads on the ends of the shaft that protrude from the nuts.  These are square threads, as opposed to typical 60 degree "vee" threads, they are 8 tpi.  I have absolutely no idea how to draw these threads; perhaps that part of this project is going to have to wait. 

More immediately, I need to erase the shaft where it passes through the grinding wheels, flanges and nuts but can't seem to do it because I created a group of graphics in order to mirror copy the shaft after drawing it on one side. 

Similarly, I misplaced a construction line somehow (just below the lower flat of the nut) and can't figure out how to erase it!  Is it because it's on its own layer?  If so, how do I get to that layer to erase it??  In addition to that, the construction line which is supposed to pass through the points created by the intersection of the nut flats.  I snapped this line using the SEKE "i" thinking it would snap to the intersection.  When I zoomed in, however, I saw it is not.  Why did this happen?

Attached is the drawing in its current state.

Thanks for any interest and assistance!

[attachment deleted by admin]

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Eric


* September 14, 2009, 12:56:31 PM
#1
As usual, I forgot to mention I am using Version 12 Deluxe.

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Eric


* September 14, 2009, 01:24:42 PM
#2
To delete a construction line, open the Edit menu and select Clear>Construction, then click on the line to be removed. Then press the Spacebar to exit that mode so you won't inadvertently delete any others.

The "I" SEKE recognizes construction lines as entities; the misplaced construction line or lines might have snapped to point where a preexisting construction line intersects one of your object lines.

Remember that you can edit a group by selecting it and pressing Ctlr+G, then return to the main drawing afterward by pressing Ctrl+Shift+G -- or you can explode the group by selecting it and pressing Alt+Shift+E (keyboard shortcut for Format|Explode).

...Since you're going to all this trouble, Eric, why not consider modeling the thing in 3D? I think you'd enjoy the challenge. And if you need 2D drawings, it's easy to take them from a 3D model.

Henry H

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* September 14, 2009, 01:47:38 PM
#3
OK, I got rid of the offending construction lines and edited the groups involving the shaft ends.  What I did there was to erase everything but the ends of the shafts and draw new perpendiculars from there to the nut.

I'd be happy to model it in 3d... Only problem is, I haven't the slightest idea how to start!  I figured I'd have to master 2D first, then move on tho 3D.  The course I'm about to take only deals with 2D also.  I wondered about that, kind of thought maybe 3D drawings were generated from the several views of a 2D or something.  Last time I had any drafting instruction we were using H, HB and Non-Photo Blue.  3D was something you did with a vanishing point...  You think I can mange to do that at this stage?

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Eric


* September 14, 2009, 10:07:42 PM
#4
I'd be happy to model it in 3d... Only problem is, I haven't the slightest idea how to start!  I figured I'd have to master 2D first, then move on tho 3D.  The course I'm about to take only deals with 2D also.  I wondered about that, kind of thought maybe 3D drawings were generated from the several views of a 2D or something.  Last time I had any drafting instruction we were using H, HB and Non-Photo Blue.  3D was something you did with a vanishing point...  You think I can mange to do that at this stage?

It'll be a challenge ;-)

I spent a little time on this, jes' fer fun. Had to guess at many of the dimensions, of course.

Henry H

*EDIT* Decided I didn't like the material for the machined surfaces, so here's a newer version of the pic...

[attachment deleted by admin]
« Last Edit: September 15, 2009, 08:47:14 PM by Henry Hubich »

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* September 15, 2009, 01:45:22 AM
#5
Eric, mechanical CAD isn't too far removed from something like Lego construction blocks.  There are refinements, but most manufactured items are assemblies of blocks.  3D CAD is learning or figuring out how to create and manipulate the blocks in the package you're using.  The refinements are glorified fillets and chamfers, or putting curved surfaces onto the blocks, while still maintaining relationships between features.  The picture shows that apart from the pedestal being an extruded polyline, everything else is boxes and cylinders.

Nice work Henry.  You're a master with materials.

[attachment deleted by admin]
« Last Edit: September 15, 2009, 04:21:03 AM by murray dickinson »

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* September 15, 2009, 07:40:57 AM
#6
Henry, that is fantastic! It even has a look similar to cast iron! 

Murray, did you "extrude" from the 2D sketch to do what you did?  That is fascinating as well. 

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Eric


* September 15, 2009, 08:52:21 AM
#7
Eric, the red polyline for the pedestal and the cylindrical inset bosses on it are actual extrusions.  The projection sketch gives snap features for diameter and height of the journal, shaft, wheel and collar cylinders, and length and height of all the boxes, z dimensions (depth) being the ones that Henry mentioned needing guesswork .

BTW, I followed your babbit casting adventures on the machinists' site, and remembered when you enquired about rpm, that plain bearings are rated in fpm.  I found this useful info:

 http://www.alchemycastings.com/lead-products/babbitt.htm

There wouldn't be a lot of loading on them if the wheels are reasonably well balanced.

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* September 15, 2009, 09:10:18 AM
#8
Murray, that info on babbitt bearings is very interesting!  Wish I had the sfpm info when I selected the babbitt.  As much searcing as I did I never came up with that site of info! Fun project, can't wait to get it all done!  It'll be cool to have the drawing to go with it, too.  Seems kind of funny to be doing it in the "reverse order"; that is, having the machine, repairing / restoring it and then doing the drawing.  It would be even more interesting to see the original drawings of it!  There is an interesting thread on that forum titled "old timey drawings" which I rather enjoyed.  I should post it here, I bet some folks here would get a kick out of it, though it is rather disparaging of CAD generally, lamenting the loss of the pesonal touch of the draftsman's hand in the drawings.  Nevertheless, it's an interesting thread with many interesting drawings posted in it.

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Eric


* September 15, 2009, 12:44:56 PM
#9
I have not ventured into the 3D world just yet.  Still grappling with how to mange drawing some features on the front view of the bearing blocks.  I drew the top view, which is not totally complete, but shows the part I'm struggling with on the front view.  The bolt holes are located in a section of the casting that is essentially an elongated cube with rounded corners on it, while the bearing blocks themselves are cylinders whose axes are perpendicular to the long axis of the bolt hole "boxes".  These boxes are also a bit shorter than the diameter of the theoretically cylindrical bearing blocks.  The drawing now shows the top view of these parts, which I drew on projection lines from the front view.

[attachment deleted by admin]

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Eric


* September 15, 2009, 06:05:11 PM
#10
There's a philosophical differentiation between engineering artisans and production-oriented engineers.  I know an architect who only worked on paper drawings and didn't reskill for CAD.  He's nostalgic for the old days, and doesn't practise now.  In fact, he's unemployable as an architect.  Most paper drawings carried the exhortation "do not scale from drawing!", the two most obvious reasons being that sometimes draftspeople make mistakes and that paper isn't dimensionally stable in most environments.  A "draft" copy is one that's considered lower-quality or unfinished.  Hand drafting, and even 2D CAD, is more likely to have errors than projections derived from a 3D model, and enhancements to 3D CAD like collision and interference detection (animated drawings of moving parts are 4D CAD) have probably saved billions of dollars in wasted time and prototype development.  Paper drawings can't convey curved surface definitions that can be created and reproduced to fine resolution with CAD/CAM.  Traditional drawings should be recognised as artisanship, but as production aids they're little more than a formal or standardised back-of-envelope or restaurant-napkin sketch, relying almost as much on the reader as the drafter for correct interpretation.   A designer conceives of something in 3D, and 3D CAD can communicate the concept unambiguously.  If the designer uses 3D CAD to sketch a concept, the production of drawings, to standards, is automated.  A Luddite's view of CAD is natural for a traditional draftsperson.

Apologies for the rant, I've had this conversation before!
« Last Edit: September 15, 2009, 06:14:38 PM by murray dickinson »

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* September 16, 2009, 01:33:48 AM
#11
No apology necessary as far as I'm concerned.  I mentioned the "old timey drawings" thread because I thought if folks found my old grinder interesting they might also find the drawings and illustrations in the couple of threads that had them interesting as well.  But I thought, this being a CAD forum, a bit of advance warning of that sentiment would be appropriate.  In fact, I went through the 2 threads I was thinking of again to have another look at the drawings there and found that there were more illustrations or renderings than engineering drawings, though there certainly were some of those.  I did some pen and ink drawing when I was younger and really like the look of it and was amazed at the quality of the ones seen there.  Same for the architectural renderings I've seen.

OTOH, I am amazed at the capabilities of a CAD program in the hands of someone who knows how to use it.  And I am enjoying learning how to use TC, and look forward to the class on AutoCAD which begins tonight!  And for that matter, the renderings I've seen from TC astound me as well.  The training cd I have has a gallery of them, and some of them are so realistic as to appear almost as a photograph! Similarly I am very impressed with what Henry did with my sketch in 3D and what you did with it also.  My reaction to that 3D model was something like, "Holy Smokes, there it is!"  I have to think anyone who disputes the value of that is fooling themselves.

I certainly didn't mean to raise anyone's ire or open a debate about CAD vs. traditional (for lack of a better word).  I just like old stuff and drawing generally, and thought I'd share it if anyone else was interested.

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Eric


* September 16, 2009, 11:31:20 AM
#12
I have made some progress but hit a couple of snags:  First of all, I created a group of graphics with the concentric circles directly beneath the bearing blocks.  I did this in order to move them having discovered they were placed inaccurately.  With that task done I have added a keyslot to each hole and tried to trim the circle to the sides of the keyslot.  No luck.  I think because the circle is a part of a group it won't let me trim it.  I tried to do it directly on the drawing and when I figured out the group was preventing this I selected the group, then "Ctrl+G" to edit group and tried again.  Still can't do it.  I've tried several combinations of things including deleting the keyway and drawing it while "editing group" and then trim the circle, still no luck.  Is there a way to "uncreate" this group so it can be treated as any other ordinary object? 

The other issue is that I'm not at all happy with the representation of the squarish part of the casting which contains the bolts for the bearings in the front view.  I drew the top view first, then projected construction lines to get the outer edge of the radius and drew those, as well as the top and bottom edges.  But now it looks like a couple of rectangles on the front view, which the object does not when actually viewed from the front.  Any suggestions?  I've added a quick side view of the bearing block for visual assistance. 

[attachment deleted by admin]

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Eric


* September 16, 2009, 03:17:47 PM
#13
re: Is there a way to "uncreate" this group?

Use the "Explode" tool, "Format / Explode".

Select the Group for the left keyway, then in the Selection Info palette expand it (click the plus+ sign). You'll see that you have a Group within a Group. Explode this twice and you have the two circles and three lines. At this point you could make this a group again. Prior to exploding this part, there are 4 lines on top of this group (overlapping the previous lines) that should be deleted; they're not needed .

The right keyway has to be handled a bit differently. You'll notice in Selection Info that one circle is a Group, then you added a circle and grouped again. Explode this "once", then hold the Shift key and deselect the inner "Circle", then Explode the remaining Group. If you had exploded twice, the inner circle would've turned into a polygon. 

hope this helps some.


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John R.

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* September 17, 2009, 05:03:30 AM
#14
Thank you, John, it helps a great deal.

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Eric