sketch circle diameter much smaller than circle on plan of same size

Hi, I am a SW newbie. Have gone new part, used Front plane, used sketch insert picture, (a jpg of a plan at 1:1 scale of the item to make) and smart dimensions and sketch and
circle, entered diameter say 50mm, yet on plan this is a much smaller size than 50mm circle on the plan. Whats gone wrong ?
I did a file > save as before drawing anything as was told otherwise the image vanishes ! I continued and chose spiral, entered values for radius, pitch , revolutions and chose anticlockwise, hit enter and got a spiral clockwise, but lost the plan image. How do I get the image back ?
Also can one place guidelines on the plan to snap to ? I found a centreline tool but it wouldnt autoscroll when i reache edge of window and found continuing it a struggle, well i didnt manage it as I couldnt see how to extend it and make the final end match my plan datum line.
Many thanks Steve
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wrote:

When you enter the sketch picture you will have to customize the size to fit your dimensions. It will probably not enter in true 1:1 with a .jpg. I suggest making a sketch object of a known size and comparing it to an object in the sketch.

When you complete the spiral command, SW automatically hides the sketch used to make it. That sketch contains the image. What you need to do is just unhide "Sketch1" (or whatever it is). Click on the (+) next to Helix/Spiral1, then right click on the sketch and click "show". If your spiral is backwards, it means you are probably looking at it from the back.

This is a 2D cad technique that is now "obsolete" in SW. You can actually use it (there is extend and trim tools), but they aren't used for most sketch features. What you want to do is create an approximate line, then use constraints and dimensions to make your lines exactly as you want them. If you need help with this idea I suggest you use the Tutorials found with Solidworks, they are of great help.
Charles

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Charles <It will probably not enter in true 1:1> oh dear, I am so used to images displaying in graphics vector progs at 1:1.
Can that default hide be turned off on images after spiral executed ?
Guidelines... This is a 2D cad technique that is now "obsolete" in SW. You can

I need the guides to trace over the picture, I usually create accurate structures (plans) in 2D vector progs, I have many guides by the time I have finished and cannot see a better way of sussing the shape of the real thing than doing it this way.I am currently trying to solve a tricky shape I have photos of and again guides are invaluable. My two most used tools are pen tool and guides, and I create accurate plans of items from photos. need guides for datum lines, edges, etc. It may be that SW achieves this without. Of course in graphics, I need guides just to draw a circle to fit to a circle location and of a certain diameter. Placing a circle exactly at a certain point on a picture see guide adde, circle drawn then dragged to snap, no doubt SW can position that circle using data boxes but that may mean various attempts at the figures until it sits where it makes a best fit. Guess I shall have to try it and see.
Steve

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