# Help Reading A Drawing



## Pontiac Freak (Mar 22, 2015)

I am reading a drawing but am not sure if I am reading it right.  In the picture you will see 2 items circled.  The first one shows the bolt size and thread and quantity.  The second one I am assuming means 3 holes .250" diameter with a depth of .5"  is this correct?  Does anybody have a quick easy cheat sheet for symbols?

thx in advance!


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## Tony Wells (Mar 22, 2015)

No see pic


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## Pontiac Freak (Mar 22, 2015)

Oops!


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## Wreck™Wreck (Mar 22, 2015)

3 holes .25 Diameter X .500 deep.


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## Tony Wells (Mar 22, 2015)

Those are only a couple of standard GD&T symbols. You can search Google and find whatever depth you desire on learning them. Not all are used all the time, but it pays to be familiar with at least the basic ones if you are machining to a standard manufacturing drawing.


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## RJSakowski (Mar 22, 2015)

What is missing on the drawing is the depth of the tap.  It would be represented by the flaccid arrow sign followed by the depth. (same notation as the drill depth).  The tap depth spec will determine whether you use a taper, plug, or bottoming tap or if you need to threadmill the hole.


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## kd4gij (Mar 22, 2015)

Those would be the counter bore for the m6 bolts I do belive


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## T Bredehoft (Mar 22, 2015)

Yes, a 6mm tap will clear a quarter inch hole by .014, no threads at all.


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## tbell (Mar 22, 2015)

Like the man said tap depth missing. 3 holes .250 dia by .500 deap. Tbell


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## Bill C. (Mar 22, 2015)

means depth.   I have never used it in my drafting classes. I had to search Google to find it.  Not sure what the designer is having you do.  You are drilling and taping then re-drilling the same hole.  A three place decimal could be a reamed on size hole as well.  There should have been a front view of the drawing showing the holes for clarity.  

The Best with your project.


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## RJSakowski (Mar 22, 2015)

Bill C. said:


> shown below.   means depth.   I have never used it in my drafting classes. I had to search Google to find it.  Not sure what the designer is having you do.  You are drilling and taping then re-drilling the same hole.  A three place decimal could be a reamed on size hole as well.  There should have been a front view of the drawing showing the holes for clarity.
> 
> The Best with your project.


It is a confusing drawing!  tbell is right; it is a clearance hole for M6. 

That said,  there is no drill spec  for the tapped holes.  The convention that I normally would use is as shown below.  Drill .0983 hole to .300 depth, tap M3 x .5 to .2400 depth.  If I wanted to provide for clearance hole above, say for a shoulder bolt, it would be on a third line expressed as a counterbore ( l_l , my attempt at the c/bore symbol) giving diameter [ c/bore symbol] c/bore depth. A final note: the drill depth is to the shoulder of the drill, not the point.


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## kd4gij (Mar 22, 2015)

The op hasn't been back yet. But he didn't show the whole drawing. So there is probly somethings we haven't seen.


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## T.B.C.801 (Mar 22, 2015)

Looking for anyone who has  machined Hymark snowmobile heads. I plotted it with a dial but if anyone has the actual  dimensions, I would be eternally grateful. They are off an RMK 700. Thanks in advance.


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## Pontiac Freak (Mar 22, 2015)

Thanks everybody for your help!  The drawings are some that I found on the internet for a ball turner and they seem to be missing some crucial info in some areas for a beginner.  I did have to do some adjustments as .5oo on all the holes would have left hardly any threads on the 2 outer holes.   That is why I was confused, seems it should have read a different depth for the middle hole than the 2 outer ones.


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