Correct convention for modelled thread

[acadiron]

Hi guys,

 

I'm new to this site so please be gentle.

I've been a sporadic user of AutoCAD over the years and have just started to model a few things that I have made. I am currently using 2008 and I would just like to know the correct convention for modelling internal or external threads so they will show correctly when executing SOLPROF (I haven't actually used this yet) or similar command. I know to correctly model a thread is a pain so I am just referring to thread length, core diameter, thread diameter, tapping/boring diameter.

At the moment I am just using the thread diameter for internal threads but have not done an external thread as yet.

 

I hope this makes sense.

 

Thanks

[JD Mather]

Are you after Detailed, Schematic or Simplified representation?

[shift1313]

I believe the info you are looking for you will find on tap charts.

 

http://www.shender4.com/thread_chart.htm

 

That tap chart is for cutting threads using a tap(not thread forming).

 

Looking at the tap chart you will see major and minor diameters. This will give you the thread height. and 60degree will allow you to figure out the base length. Thread convention for that chart, 6-32, 32 threads per inch, #6. 1/4-20, 20 threads per inch, 1/4" major dia. Metric bolts are a little different. 6x1.5. 6mm and 1.5mm per thread.

 

 

 

There are different specs for different things for instance when tapping a hole with NPT sizes you are supposed to use a taper drill bit or drill undersize and use a taper ream. If not there is another drill size to use.

[acadiron]

Thanks for the info Shift1313 but I know all about threads as I'm a machinist by trade.

 

JD, I suppose I would be after a simplified or schematic representation. I can easily put a 6mm hole for an M6 tap or 5mm hole to represent the tapping size in my model. When I use the profile command I would need ACAD 2008 to show the tapping size and the thread diameter.

 

For an external thread I would need ACAD 2008 to show core diameter, thread diameter and thread length.

 

Does ACAD 2008 do this or does I need to be manually input into the 2D orthographic drawing?

 

Is that any clearer?

[shift1313]

typically this is done with references. For instance your minor diameter would be the hole size in your part and a dashed circle/cylinder would represent the major diameter and a callout would indicate tap size. This would probably be the fastest method in acad as it does not have a tap or thread function(that I know of).

 

like the image i uploaded. note, the hole diameters should be to 4 decimal places. .2010, .1590 and .1065

[JD Mather]

For Simplified Representation the lines (circles) are not drawn at true postion but rather at a nominal position. The reason for this is that for small threads the line (circles) representing the true depth of the thread would be so close together that they would essentially print as one line (circle). See Giesecke et al Technical Drawing.

 

The external diameter is normally drawn true size while the internal is offset a nominal amount. AutoCAD has no way of doing this automatically in solprof or any method used to generate 2D from 3D.

 

Modern CAD programs line Autodesk Inventor or SolidWorks take care of this automatically. In fact it confuses some people when the nominal lines (circles) are put into the drawing when they expected true dimensions.

[acadiron]

typically this is done with references. For instance your minor diameter would be the hole size in your part and a dashed circle/cylinder would represent the major diameter and a callout would indicate tap size. This would probably be the fastest method in acad as it does not have a tap or thread function(that I know of).

 

like the image i uploaded. note, the hole diameters should be to 4 decimal places. .2010, .1590 and .1065

 

Thanks for the info Shift, but I have no problem with 2D representation of thread convention. Maybe I'm not explaining myself clearly. Apologies if I sound patronising on this one.

 

1. I am creating a solid model of a component

2. I have a tapped hole in the solid model.

3. I am using a cylinder and subtracting this from the solid model to represent the tapped hole.

 

On a 2D drawing the convention is as you so correctly provided. AutoCAD 2008 enables a profile command (FLATSHOT, SOLPROF) to create a 2D drawing from the solid model.

 

My question is, how do I model the thread in the solid model so when the profile command is executed the 2D drawing shows the correct convention?

 

Similarly with an external thread.

 

1. I am modelling a bolt, say.

2. I use a cylinder to represent the external thread diameter.

 

How can I model the external thread so the core diameter and thread length are represented on the 2D drawing when the profile command is executed.

 

I am assuming now that Acad2008 cannot do this and maybe thread features need to be added manually on the 2D drawing.

[acadiron]

Thanks for the info JD!

 

How do you rate Solidworks? We use it at work but I don't have a chance to play as I'm on the shop floor but the programmer keeps on insisting he'll let me have a go.