Hi everyone I am trying to learn how do I correctly draw, with a ruler (where are milimeters visible as much as possible) and pencil, on already given surface screw thread and on another surface (different task) how do I correctly draw, lets say, pair (or it can be just one too - study of drawing in this case is prolly the same) of (ball) bearings. Unfortunately I don't have an example of ''putting'' bearings on given surface but I am showing taskes, which we have done on university, how to draw screw thread on surface. From this, it might be obvious what I would like to do with ball bearing. To begin with, I am showing ''empty'' surfaces with different color HERE. As you can see on the link there are actually two the same taskes. Green color (given surface) and blue color (definited locations) shows what is given in the task, everything else (lets overlook the points which are given by teacher) is student's work. This screw thread contains bolt M10x40. The colors might be a bit annoying, so I am showing again, without colors HERE2. The upper picture is work of my mate who used to lend me the task. He got 50 points out of 50. The other picture, at the bottom, is my work. I got only 5 points out of 50. I won't ask how to draw this but is there any tutorial how to correctly draw screw thread as that one (Mzzxzz where ''z'' is the number) and also how to put on the surface ball bearings as I used to put the screw thread here? Another example, which we had on exam is THIS. Here is bolt M12 with length 55mm and screw (?) 36mm (36 is inside those 55mm of course). Surface is given, definited locations, which shouldn't be really necessary here, are also given. Everything else is my work. I got 4 points out of 20 on exam in this task. I know, I made big mistake in the ''head'' of the bolt already. If you look at it, a part of ''head'' is into surface and it should be outside. However, im afraid this is the only thing I know what I did wrong. Red colors shows teacher's correction - it could be obvious. So, I would also like to please if someone could check what I have learned so far - here are the following statements that I described while studying. I know the following statements aren't enough to draw the whole screw thread, thats why I asked for tutorial also. The only thing I would like to please in those statements, are to correct me if I am wrong. For better view at the task, I made ''additional zoom'' on the picture, so more details will be visible. Here it is: CLICK2 1. We usually begin with bigger size of screw - I could name that ''outside size'' also. Since bolt is M10x40, the length between Location 1 and Location 2 must be exsactly 10 mm. But is to which location do both lines go definited too? In the task could be a trick - part of surface (where location 1 and 2 end) wouldn't be there. 2. As I mentoined in the task we have the bolt M10x40. So the length between Location 3 and Location 4 is exsactly 40 mm. 3. I also study from THAT book. From it, I have seen an information that we can get the length between Location 3 and Location 5, on the following way: We know we have 40mm length (my previouns statement). From the tables I see the length from Location 5 and Location 4: 40 - 4.5 = 35.5 and because of this is 40 - 35.5 = 4.5 mm, so the length between Location 3 and Location 5 is 4.5 mm. This is the way which this book shows but on the drawing I really doubt if this is 4.5 mm. Keep in mind that I haven't really mentoined those tables in my post or locations on the network to see them. I have them near my hand thats why. If someone would like to take a look at my tables, please let me know and I will put them here for you. 4. Because of this type of the bolt (M10) the ''inside size'' (between Location 8 and Location 9) is exsactly 8.3 mm. If I look at the drawing, it answers exsactly this 5. Length between Location 4 and Location 7 is 7.3 mm. Here I am a bit in doubts. Is it really from Location 4 to Location 7 or is it from L. 6 to L. 7? Table and the book (not the one which I showed, I study from several books) shows from L. 4 but if so, I have absolutelly no idea what to do between L. 4 and L.6 - there might be also specific angle that we have to remember but, as we see at the end of screw thread, it isn't the only angle that is important. 6. Length between Location 3 and Location 10 is 7 mm. But how do we divide that? There are more other subjects that are important here but I still haven't figured them out yet. However, Im not sure what to do with ball bearings if I try to draw them like that. I haven't found explanation of this anywhere yet. While searching for explanation for screw threads, I haven't had much luck. Many sites show me something similar to THIS3 but it isn't really so useful for my opinion. Engineering standards that I used (just for screw threads) are: SIST ISO 724 / DIN 13 SIST ISO 6410 / DIN ISO 6410 / SIST ISO 3508 / SIST ISO 4755 / DIN 76 SIST ISO 24032 Thank you for any kind of help.