Made scrap from parts due to a typo on LMS tap & clearance chart!

I use the LMS chart all the time. I like having the 2 columns, as others have mentioned, as it gives you different options. I've tapped holes where I've had to go below 50% thread engagement to be able to tap it without risk of breaking the tap, I've tapped others (especially thin material) at 80%. Then there are thread/ roll form taps. Sometimes I split the difference between the two columns, depending on material and thickness. Thread engagement doesn't need to be a fixed value, use what is appropriate for the material, thickness and application.
 
We all know the feeling when a tap starts getting tight and springy........but we are almost there so try for just one more turn.....pink!
 
yup, I've done that. It's pretty much guaranteed to be the last op on a part too!
 
Tozguy said:
We all know the feeling when a tap starts getting tight and springy........but we are almost there so try for just one more turn.....pink!
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Don't do that!
My heart was racing and I started to sweat as I read it.

You're damned if you go forward and you're damned if you go back........

A dreadful place to be!

-brino
 
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Not happy with the feel or the look.
Did some more today with 27/64 and all is well once again.
Hole size was spot on in both instances as well
 
finsruskw said:
Did some more today with 27/64 and all is well once again.
Hole size was spot on in both instances as well
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Can you save the ones you're not happy with?
-brino
 
Possibly, if i went with 9/16" but then mods would have to be made in the OEM part it mates with., don't think anyone would want to do that.

Not a big deal, small part and I'm not out that much in the way of material.
Will chalk it up to training!!

This part has to do with fore and aft movement and part of a lift rod ass'y for a hydraulic cylinder under load and I feel, it should have full thread engagement and stay tight in the sleeve it goes through.
It is also secured with a jam nut for added rigidity.
The piston clevis is pinned to it in this photo and moves in the same arc on the same axis with the white lift arm so has to remain tight.
 

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finsruskw said:
Why would they list a drill size that produces crappy threads in the material they spec it for??
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The threading charts on LMS are only basic references for the most common types of threads in the most common materials.. They are meant to be quick references for those knowledgeable as to where and when each apply. Much more comprehensive information about thread styles, forming, and cutting can be found in the Machinery's Handbook. Even then each edition doesn't cover all the thread types and methods to create them. Each edition covers those that were popular at the time it was printed. As time moves on some styles and methods are considered obsolete and deleted while others previously not covered are added. Editions from the 1930's and 40's barely touch on metric threads, and later editions largely pass over British Standard threads.

Looking at the 22nd (1986) edition there are nearly 230 pages covering thread types and methods of cutting or forming. As Mentioned previously this section only covers those deemed to be widely used in industry at the time of printing. I currently have over a dozen different editions of this publication to cover the types, styles, and methods of creating the ones I deal with on a regular basis. Thread cutting and/or forming is far from a one size fits all scenario. There are many variations depending on the material, method, and type of thread needed.
 
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