Chart for threading with compound set at 29 or 29.5 degrees (2024)

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737mechanic
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Joined: Thu Jun 04, 2009 6:27 pm
Location: Dallas

Chart for threading with compound set at 29 or 29.5 degrees

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Postby 737mechanic »

Was doing some threading the other day and thought I would try to follow the numbers on the threading fish tail and realize they did not work the way I figured they would.

So after doing some research found they are calibrated for feeding straight in using the cross slide not the compound set at 29 degrees.

I have tried to find a chart or something that shows how much depth of cut it takes using the cross slide set at 29 or 29.5 but have not found anything. So does anyone have a link that shows the proper depth of cut to get a proper thread using the crosslide set at 29 or 29.5.

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ctwo
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Joined: Tue Mar 27, 2012 12:37 pm
Location: Silly Cone Valley

Re: Chart for threading with compound set at 29 or 29.5 degr

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Postby ctwo »

Standards are so important that everyone must have their own...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...

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warmstrong1955
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Joined: Thu Mar 18, 2010 2:05 pm
Location: Northern Nevada

Re: Chart for threading with compound set at 29 or 29.5 degr

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Postby warmstrong1955 »

Today's solutions are tomorrow's problems.

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SteveM
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Joined: Mon Jun 27, 2005 6:18 pm
Location: Wisconsin

Re: Chart for threading with compound set at 29 or 29.5 degr

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Postby SteveM »

warmstrong1955 wrote:Compound Travel = Thread depth (per side) / .8704

Would that apply to measuring the thread pitch diameter, i.e. if I measure with my thread pitch mic that I have 25 thou to go that I need to advance the compound 29 thou (0.025/0.8704=0.0287)?

Steve

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ctwo
Posts: 2996
Joined: Tue Mar 27, 2012 12:37 pm
Location: Silly Cone Valley

Re: Chart for threading with compound set at 29 or 29.5 degr

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Postby ctwo »

The formula calculates the hypotenuse of a 29.5, 60.5, 90 degree triangle, and the compound follows the hypotenuse with the acute angle measured between the cross slide and compound.

That will take a radial amount, so it depends on if your compound is direct reading (which now that I think about it, aren't they all?) or diameter.

How do you know the thread depth per side without using another chart?

BTW, I was trying to see the difference between national form tool and V form tool. What is it?

Standards are so important that everyone must have their own...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...

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GlennW
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Joined: Sun Apr 15, 2007 9:23 am
Location: Florida

Re: Chart for threading with compound set at 29 or 29.5 degr

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Postby GlennW »

The truncated tip on National Form vs the sharp V.

Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!

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warmstrong1955
Posts: 3568
Joined: Thu Mar 18, 2010 2:05 pm
Location: Northern Nevada

Re: Chart for threading with compound set at 29 or 29.5 degr

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Postby warmstrong1955 »

SteveM wrote:

warmstrong1955 wrote:Compound Travel = Thread depth (per side) / .8704

Would that apply to measuring the thread pitch diameter, i.e. if I measure with my thread pitch mic that I have 25 thou to go that I need to advance the compound 29 thou (0.025/0.8704=0.0287)?

Steve

Divided by two....yes.
Calcs are per side.

Bill

Today's solutions are tomorrow's problems.

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warmstrong1955
Posts: 3568
Joined: Thu Mar 18, 2010 2:05 pm
Location: Northern Nevada

Re: Chart for threading with compound set at 29 or 29.5 degr

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Postby warmstrong1955 »

ctwo wrote:How do you know the thread depth per side without using another chart?

Here....play with this.....

A simple thing I created to feed me numbers, without grabbin' a calculator.
Got seriously convoluted with 47 people askin' for me to "add this and add that".

I shoulda kept the original.....
But....here ya go....play....it's just math.....

FYI....I still use a chart...and a calculator.....it takes seconds....

Chart for threading with compound set at 29 or 29.5 degrees (8)

Thread-O-Matic 03.xls
(145 KiB) Downloaded 597 times

Today's solutions are tomorrow's problems.

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ctwo
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Joined: Tue Mar 27, 2012 12:37 pm
Location: Silly Cone Valley

Re: Chart for threading with compound set at 29 or 29.5 degr

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Postby ctwo »

Thanks Glenn and Bill. I had an inkling NF Tool meant with the tip ground. Who threads with a sharp point? I guess then that it will not be as easy as remembering .75/TPI

I like charts too, and the math. It's good to know where the charts came from, especially since I can never find them when I want them.

Standards are so important that everyone must have their own...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...

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Harold_V
Posts: 20319
Joined: Fri Dec 20, 2002 11:02 pm
Location: Onalaska, WA USA

Re: Chart for threading with compound set at 29 or 29.5 degr

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Postby Harold_V »

Unless the thread you hope to generate simply "doesn't matter", it would be my opinion that you should lose the notion of trusting a chart or formula. They work only in a perfect world, one in which your threading tool is precisely ground with the exact flat on the tip, and you have coordinated your dial setting with the major diameter of the part. All in all, too many possible places for error to occur when it's so easy to take measurements with wires.

The tolerance for pitch diameter is relatively close, and it gets narrower as the thread pitch decreases. It's way too easy to under or over cut by trusting dial settings and calculated depths.

Harold

Wise people talk because they have something to say. Fools talk because they have to say something.

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ctwo
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Joined: Tue Mar 27, 2012 12:37 pm
Location: Silly Cone Valley

Re: Chart for threading with compound set at 29 or 29.5 degr

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Postby ctwo »

Another "trick" that I've seen (and not to undermine anything Harold has said) is to place a clock to the tool holder to see the actual in-feed when working the compound.

Standards are so important that everyone must have their own...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...

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Harold_V
Posts: 20319
Joined: Fri Dec 20, 2002 11:02 pm
Location: Onalaska, WA USA

Re: Chart for threading with compound set at 29 or 29.5 degr

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Postby Harold_V »

That can serve to determine distance traveled, but it is totally reliant on identical setups. Theoretical travel may or may not be proper for a given pitch diameter, due in part to the variations in major diameter, as well as varying width of the flat of the tool in use. All in all, wires serve to provide a method of establishing where you are. Once you know that, calculations of travel can work, although for critical threads, one should always measure when approaching finish size.

I hope you understand that my position in this matter relates to having to satisfy specifications. For the guy trying to make one part fit another, there's certainly nothing wrong with using calculated travel. Hell, I've fitted more than my share of threads simply by ensuring a nut fits. Some times it just isn't critical. Chart for threading with compound set at 29 or 29.5 degrees (13)

Harold

Wise people talk because they have something to say. Fools talk because they have to say something.

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Chart for threading with compound set at 29 or 29.5 degrees (2024)
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