Thread finish quality is poor

[LockTech]

Hello, I am wondering if anyone can point me in the right direction. Its been a while since these parts were run but as you can see in the pics the thread surface quality is definitely worse. They do function ok for our needs but they look like crap. Inspection of the drill bit and tap look fine.

Here is the setup,
22 HAAS ST10Y
Drill bit is #39
4-40 Form Tap https://www.mscdirect.com/product/details/00974774
Fusion 360
Hole and tap is using Radial live tooling


6061 bar is from two different suppliers but are supposed to be the same thing.
I believe we used the same tap and drill last run but cannot confirm it for sure. Also it is possible since the code gets tweaked occasionally that a setting in fusion is different than last time. Also, there is a couple operations being done between the hole being drilled and the tap op. Changed from Synergy 735 to Castrol Syntillo 9918.

This is the tapping portion of the program
(TAP 4-40 7)
M1
T101
M154
G28 H0.
G99
G97
S500
G54
M8
G19
M15
G0 C-41.043
M14
G0 Z-0.3606
X1.96 Y0.0098
X1.16
X1.1062
G195 X0.47 F0.025
G80
G0 X1.96
M135
M155

M9
M33
G53 Y0.
G53 X0.
G53 Z0.
M155
G53 G0 Y0.


Thanks in advance

 

[bigjon61]

Code looks good to me. Since you've changed coolant, have you tried using tapping fluid (I like Relton A9 for alum) to see if the problem is lubrication related?

 

[Donkey Hotey]

Somebody is going to jump down my throat for being a nationalist or racist or something but, have you tried a small batch of confirmed, US aluminum? Even if you have to machine the "stock" out of something else you have laying around, try a bar of Kaiser or something you know. When something like this went to hell for no reason, it was usually traced back to the material. The worst one happened to be small drills and taps in 1/2" square aluminum bar.

 

[Mtndew]

6061 bar is from two different suppliers but are supposed to be the same thing.

Did you get certs with that aluminum? What sources did you buy them from?

 

[kevin66]

We use Castrol 9918 coolant in most of our machines. It doesn't support tapping very well regardless of concentration. A9 or WD40 will probably make your problem go away.

 

[LockTech]

Code looks good to me. Since you've changed coolant, have you tried using tapping fluid (I like Relton A9 for alum) to see if the problem is lubrication related?

I haven't tried hand tapping it, using a tapping fluid such as Relton. But the coolant was one of the changes, I was hoping to get some feedback from anyone using Castrol Syntillo 9918 with aluminum.

 

[Houdini]

Agree with others, material, I doubt it is the coolant. try a WD40 shot.
could also be a booger on the tap, try a new one to confirm.
good times.

 

[LockTech]

Somebody is going to jump down my throat for being a nationalist or racist or something but, have you tried a small batch of confirmed, US aluminum? Even if you have to machine the "stock" out of something else you have laying around, try a bar of Kaiser or something you know. When something like this went to hell for no reason, it was usually traced back to the material. The worst one happened to be small drills and taps in 1/2" square aluminum bar.

I agree with you, that could be an issue. I'll search around and see if I can find some of our old stock.

 

[gregormarwick]

We use Castrol 9918 coolant in most of our machines. It doesn't support tapping very well regardless of concentration. A9 or WD40 will probably make your problem go away.

I doubt it is the coolant. try a WD40 shot.
could also be a booger on the tap

Hysol XF here, great coolant but tapping aluminium with it just does not work. Plenty of other coolants are the same.

My money is on build up on the tap as a result of tapping with coolant.

Another possibility is chipping on first couple of leads of the tap. This is a common failure mode of form taps and causes tearing.

Look at the tap under a microscope, or put it in some sodium hydroxide solution and see if it starts bubbling...

 

[Houdini]

Hysol XF here, great coolant but tapping aluminium with it just does not work. Plenty of other coolants are the same.

My money is on build up on the tap as a result of tapping with coolant.

Another possibility is chipping on first couple of leads of the tap. This is a common failure mode of form taps and causes tearing.

Look at the tap under a microscope, or put it in some sodium hydroxide solution and see if it starts bubbling...

Another check in my box of why full synthetics are junk.

 

[Ox]

It mentions "mineral oil" a cpl times, but also says "synthetic", so not sure which it is?

But the cheat sheet does confirm that tapping is not one of it's key apps.

https://msdspds.castrol.com/bpglis/FusionPDS.nsf/Files/B8D42ECF5700FFE480257FC4002D9E0F/$File/459389_XI_en.pdf

-------------------

I am Ox and I approve this here post!

 

[gregormarwick]

Another check in my box of why full synthetics are junk.

XF is semi...

And it is one of the very best coolants I've ever used by just about every other metric! I can tap steel with it all day long. Form tap stainless with it no problems. But no matter what I do it will tear in aluminium. Also it really doesn't work for turning aluminium, constant build up on the insert.

 

[Houdini]

XF is semi...

And it is one of the very best coolants I've ever used by just about every other metric! I can tap steel with it all day long. Form tap stainless with it no problems. But no matter what I do it will tear in aluminium. Also it really doesn't work for turning aluminium, constant build up on the insert.

I saw it said synthetic, so I thought full.
semi is da besterest.

 

[LockTech]

Did you get certs with that aluminum? What sources did you buy them from?

This batch came from American Metals Supply in Foley AL. These parts only have to meet our inhouse criteria so no certs were requested.

 

[LockTech]

We use Castrol 9918 coolant in most of our machines. It doesn't support tapping very well regardless of concentration. A9 or WD40 will probably make your problem go away.

That's good info to have. Thanks for the feedback. At he risk of sounding like I don't know what I'm doing, how would A9 or other tapping fluid be used in an "enclosed" type machining center? Or are we talking about making it a separate step?

 

[hanermo]

It seems to me that the piece D is either 1.16 in (inches, yes ??) radius or in diameter, don´t know the codes well enough to immediately identify.
And it seems You are starting with S500, spindle rpm of 500.

Suggest:
Start with spindle rpm of 3000.
(for 2" D workpiece 3000 rpm should be fine, and most/all chucks and collets are safe at this rate).
Your problem will probably go away.

Perhaps reduce feed/turn by 50% if needed.

Use ccmt inserts if needed, they will not tear the material, within reasonable conditions.

 

[LockTech]

Hysol XF here, great coolant but tapping aluminium with it just does not work. Plenty of other coolants are the same.

My money is on build up on the tap as a result of tapping with coolant.

Another possibility is chipping on first couple of leads of the tap. This is a common failure mode of form taps and causes tearing.

Look at the tap under a microscope, or put it in some sodium hydroxide solution and see if it starts bubbling...

Thanks for the feedback, I will look at the tap under our microscope.

 

[LockTech]

It seems to me that the piece D is either 1.16 in (inches, yes ??) radius or in diameter, don´t know the codes well enough to immediately identify.
And it seems You are starting with S500, spindle rpm of 500.

Suggest:
Start with spindle rpm of 3000.
(for 2" D workpiece 3000 rpm should be fine, and most/all chucks and collets are safe at this rate).
Your problem will probably go away.

Perhaps reduce feed/turn by 50% if needed.

Use ccmt inserts if needed, they will not tear the material, within reasonable conditions.

The part diameter is .95 in. I think the 1.16 is probably where it rapids to.

I'm a little confused, how can you speed up the spindle speed and slow the feed while tapping? Wont this just strip out the threads?

The threads are only 4-40, what ccmt inserts would apply to this?

 

[hanermo]

1.
You can specify any spindle speed and the threads/cuts will follow that.
Alu likes high speed and 1 " at 3000 rpm is on the low end.
-
Suggest changing the S500 to S3000.
It will probably fix the issue, at least cosmetically.

-
It gets really complex once You want to make really accurate threads really well -- but they won´t be done in alu in any way.

-
The feed rate depends on what you specify in the tapping cycle line.
There is often a short and longer form, where the longer form allows more control and specifying the feed/rev plus other stuff.
-
CCMT inserts come in all sizes.
I have no idea what 4-40 is, my threads come in like 0.25 mm/turn for very fine threads.
4-40 is probably similar.
-
CCMT is a positive cut, 7 degrees iirc, excellent general insert for anything from alu to steel to interrupted cuts in hard tool steel.
A new ccmt insert will cut 1 micron cuts in tool steel, no problem.
It wears the edges, so not too long, but great for making progressive gages etc.

 

[hanermo]

ccmt 21.25 iirc, small general insert-