Further to the left are the revision notes. The revision
notes are concise, but clearly tell the changes made to the print and the dates
made. They are useful to the machinist for making changes to the machining
program. We highlight these when the
print goes out to the shop.
Finally on the bottom left, the Notes indicate important
features that can’t be shown on the part views.
One of the notes indicates a sample is available. Machine shops love samples. Samples have clues that tell us how the part
was made previously and what the customer expects. We can see how
another shop has made the part and save some time by eliminating
guesswork. We can also sometimes improve
on the methods used by them.
View by View
Normally, views are not named. I have named them in the sample print for clarification.
Starting in the upper left is VIEW 1. This view has number call-outs that are two and three places to
the right of the decimal point. In
this print, the standard indicates that 3 decimal places are a plus or minus
.005” tolerance. Don’t use three(or four)
decimal places unless it is necessary to the function of the part. It adds cost without adding value. I have seen a few prints with all numbers
out 4 places past the decimal point. In some cases, it has unnecessarily doubled
the price of the part.
VIEW 2 is basic. The
only thing I will say about it is that the smaller diameters are facing to the
right. This is the way a round part
would be put on a lathe and makes programming easier.
VIEW 3 is somewhat confusing. The radii of the slots are very close to locations of the 4-40
tapped holes. I have added notes and
center marks to help the programmer distinguish between them.
VIEW 4 is an isometric of the back of the part. It has no callouts and is only used to
clarify. A sample could serve the same
VIEW 5 is a section through the part showing a typical
tapped hole, the 2.20 inch through hole and a typical groove. Again three decimal places are only used
where necessary. It also has notes with leaders to indicate where the finish is polished smooth.
VIEW 6 is another “iso” showing the front side of the part.
In this small space I can't cover all of the necessary items that go into the making of a great blueprint.
I hope this short article has been helpful. I made some changes to the print as I was going along. Proof that there is no such thing as
perfection! Any suggestions or
criticisms are welcome.
2010 Cambridge Machine Works. Inc.