G76 Chamfer Haas end of Thread

G76 Chamfer Haas end of Thread

Tags :

Category : Haas Turn

G76 Chamfer Haas, this is another myth busting article about the G76 threading cycle.

It’s so easy to use cycles like G76 day in day out and never really fully understand how they work.

Haas make this simpler as they just use one line as appose to the two lines on Fanuc.

Haas

G76 X16.93 Z-25. K1.534 D.485 F2.5

Fanuc

G76 P010060 Q20 R.02
G76 X16.93 Z-25. P1534 Q485 F2.5

These days people say “It’s not rocket science”. Sorry but this really is fuckin rocket science it’s so complicated.

“It’s not rocket science” what on earth is that all about.

I hate these phrases that people pick up on these days.

I was watching my favorite TV show “How to Look Ten Years Younger”.

It’s this TV program where they take a miserable old bastard like me and make them look 15 again.

Now I don’t have a problem with people saying “Oh my god”. I mean people have said it since God was a lad.

But this woman kept saying “Oh…………….My…………..God”  with long gaps between each word.

I thought about how annoying it was and suddenly realized everybody is fuckin doin it and it drives me bloody shitless.

Back To G76 Being Complicated

Remember I was on about how people use these cycles everyday without really understanding them.

Anyway I didn’t fully understand it so one day I thought “Fuck this I need to know more” 

That’s when I sorted out the number of passes thing. If you don’t know how to calculate the number of passes in a G76 threading cycle then you should read the article above.

G76 Chamfer Haas, Setting 95 and 96

G76 Chamfer Haas

I have read so many articles on this and they either gloss over it, bullshit or just plain ignore it.

Why would you want a chamfer at the end of your thread anyway?

Well it’s obvious really.

Oh and by the way it’s not really a chamfer, which in itself is confusing.

It’s the thread running off the part.

If you kept tightening a bolt it would eventually shear. That shear point would be the weakest part of your thread. That is the point where the thread runs out.

 

G76 Chamfer

Setting 95 and 96 are to give you this run out. The tool comes out of the thread at an angle.

Now you might be thinking “I’ve done this for years and nobody gives a shit about it”.

Well you are wrong, if you ever worked for Rolls Royce you will know that aircraft threads are really strict on this.

This means if you screw a nut onto it, then it will tighten up as it gets closer to the end.

And obviously this takes away that shear point and makes the thread stronger.

Next time you are on a plane and it lands successfully without either of the wings dropping off you’ll know why.

G76 Chamfer Haas Setting 95

This is the number of threads you want it to run out over.

For example if you put 3.00 in here.

It would run out over 3 thread pitches. If your thread pitch was 2mm it would run out over a 6mm length (3 x 2 = 6)

G76 Chamfer Haas Setting 96

This is the angle of the thread run off.

If you put 20 in here it would run off at 20 degrees over the 6mm length above.

Be careful because the control doesn’t necessarily make sense of your figures. It’s up to you to make sure that the angle and the distance make sense.

See Below

G0 X22. Z3. G97 S1200 M3

G76 X16.93 Z-25. K1.534 D.485 F2.5

The one above has 5.00 in setting 95 and 45 in setting 96. 

So because setting 96 is 45 degrees it runs off at 45 degrees.

Setting 95 is 5.00 and the pitch is 2.5  (F2.5) so the length of run out is:

5 x 2.5 = 12.5.

It still finishes at Z-25. by the way.

The example above is a load of bollocks so please don’t try this at home.

No screw threads have been injured or destroyed in the making of this post.

You will notice the tool jumps back in the X axis. It is going back to its start point. That is the X22. on the line before the cycle.

Now Another Example

G0 X22. Z3. G97 S1200 M3

G76 X16.93 Z-25. K1.534 D.485 F2.5

The one above has 1.00 in setting 95 and 45 in setting 96. 

So because setting 96 is 45 degrees it runs off at 45 degrees.

Setting 95 is 1.00 and the pitch is 2.5  (F2.5) so the length of run out is

1 x 2.5 = 2.5.

It still finishes at Z-25. by the way.

This means your run-out will be in one thread pitch.

If you’re concentrating  you will notice the tool jumps back in the X axis. It is going back to its start point (X22.).

G0 X25. Z3. G97 S1200 M3

G76 X16.93 Z-25. K1.534 D.485 F2.5

Notice above that by putting a bigger X figure (X25.) you get more clearance.

Just One More Before You Go

 

The above one has 3.00 in setting 95 and 10 degrees in setting 96

What If I Don’t Want All This Shit?

M23 means you will get a chamfer.

M24 means you won’t get the chamfer.

Please note M23 is active unless you program M24.

M23 is the default

So if you hit reset or switch the machine off it will always do the chamfer unless you program M24.

So if you don’t want it you need an M24 just before the G76 cycle.

Note: This works for G92 as well.

Here is what Haas have to say.

Thanks for watching and reading

If you have been affected by any of the issues in this post or need CNC Counselling then contact me.

Siemens 828 840 Sinumerik Training

Or call us 

If you want to learn to program CNC Milling Machines

Look no further Contact CNC Training Centre

 

 


Log out of this account

Leave a Reply

CNC Training Centre
WP to LinkedIn Auto Publish Powered By : XYZScripts.com