Some help with tapping

tcncj · Oct 18, 2017

I need some help with tapping thread.

I need to tap a bunch of M8x1.25 holes. And I bought some new taps (YG1) specific for Aluminum.
Machine got rigid tapping.
RPM 500
coolant on

I drill a hole (carbide 6.8mm drill)
chamfer the hole 45 degrees
And with my old taps this provides a nice thread.

But somehow I can't get nice thread with the new taps.
Yes they are for the same pitch haha. And they aren't form taps.
Thread is very loose. And it feels like the drilled hole is too small for the tap.

Left the new YG1 tap with some different chamfer sizes
Right my old tap

bw_4000 · Oct 18, 2017

Are the two taps the same thread class (thread tolerance)?

tcncj · Oct 18, 2017

Both 6H tolerance

Booze Daily · Oct 18, 2017

Check the minor dia. Is it in tolerance?
Check with thread gage. GO goes, NO GO doesn't? Don't worry about it.

AARONT · Oct 18, 2017

Are you holding them in the same tool holder and collet?

tcncj · Oct 18, 2017

Yes, ER16 collet

Booze Daily said:
Check the minor dia. Is it in tolerance?
Check with thread gage. GO goes, NO GO doesn't? Don't worry about it.

I don't have a gauge. But the thread is so loose I don't need a gauge to tell it's not good haha

Larry Dickman · Oct 18, 2017

did you indicate the tap in? Just because it's in a collet doesn't mean it's running true. Your RPM may be too low for that type of tap. Try a couple holes at 2000 rpm and see how they look.

michiganbuck · Oct 18, 2017

Agree with the old taps may be tapping tight but still with-in specifications // the new taps loser but sill in spec.

wore or dull taps tap tighter...

If not having a tap go/no go gauge you might try a highest grade bolt...

Drill point error would make both taps run poor...but drill hole should be checked for size..

We used to re sharpen dull taps with taking a small skim off the lead and the flute to bring taps back to spec after they began running near tight.

kevin66 · Oct 18, 2017

I would try to tap a hole with A9/Wd-40 to see if its possibly your coolant. Obviously the new tap is a chip puller style where the old one is a plug tap. In the past I have noticed plug taps hold size more consistently and are far less finicky than pullers when it comes to cutting parameters.

sinha · Oct 18, 2017

If the thread is too loose, 6.7 bore dia instead of 6.8 might help.

Bobw · Oct 18, 2017

I'm going to say the tap is running out a mile or so...

Have you rolled it on a plate? Big chip stuck in the collet?

YG stuff is usually pretty good.

tcncj · Oct 18, 2017

Both taps are new.
There is no runout on the collet (everything is brand new). Checked to be sure.
I swap both taps in the same holder.

Increased RPM to 1200.
Exactly the same settings used

Left: my 'old' taps (it pushes the chips forward)
Right: the new ones from YG1 (it pulls the chips back)

Chamfer settings are also the same.
The YG tap seems bigger. And doesn't run as smooth is my 'old' taps.
I could make the chamfer bigger. But previous tests didn't result in better threads.
Besides the finish looks horrible.

Dave K · Oct 18, 2017

How deep are you tapping with this tap? You look like you have a chip binding problem with the new tap.

NAST555 · Oct 18, 2017

I have a feeling that either they sent you the wrong tap or you ordered the wrong one... Blue band normally means for stainless... You are looking for a yellow band aluminium specific tap. Will make the world of difference in aluminium.

You will notice that spiral flute taps have loads more clearance towards the inside because it pulls the shaving out, making them weaker but also obviously the go to taps for short blind holes where you cant push the shaving with a spiral point tap. This and the clearance on the grind is probably not correct on your tap because it is not an aluminium tap.

Dave K · Oct 18, 2017

NAST555 said:
I have a feeling that either they sent you the wrong tap or you ordered the wrong one... Blue band normally means for stainless... You are looking for a yellow band aluminium specific tap. Will make the world of difference in aluminium.

You will notice that spiral flute taps have loads more clearance towards the inside because it pulls the shaving out, making them weaker but also obviously the go to taps for short blind holes where you cant push the shaving with a spiral point tap. This and the clearance on the grind is probably not correct on your tap because it is not an aluminium tap.

Yep, nailed it. They gave you the wrong tap. That one's for Stainless. Here's the one you want for aluminum.http://www.yg1usa.com/feature/item_...FED THREAD TAPS&pre2=&name=SPIRAL FLUTED TAPS

MattiJ · Oct 18, 2017

Does the chip eject in nice curl or ugly mess?

Maybe you got wrong tap? too hard to see the text on the pic to check it..
Edit: previous posters already pointed out that its most probably wrong tap

Something like non-relieved spiral tap welds easily with the material and makes a mess of the thread. (And fully relieved synchro tap can cut oversize if used on floating system)
http://www.ymwtapsusa.com/download/newsletters/Understanding-the-basics-of-spiral-fluted-taps.pdf

tcncj · Oct 18, 2017

It's a messy chip
And chips seems to bind

I bought these ones
YG-1 TC163 Series Spiral Flute Metric Coarse Machine Taps - Uncoated For Aluminium

gregormarwick · Oct 18, 2017

The tap is for aluminium.

Your old tap is spiral point, with at least 5 threads of lead. Your new tap is spiral flute with probably only 2-3 threads of lead, and cuts much more aggressively. It's like the difference between a taper tap and a bottoming tap. The fewer threads of lead the more lubricity is required to prevent tearing. As someone else suggested, try with oil (neat coolant if you don't have any tapping oil, WD40 also works very well on aluminium) and see what happens.

Limy Sami · Oct 18, 2017

While I agree YG is usually pretty damn good, simple way to check if it is the tap, .do a few threads by hand and if they're still bad, chuck it back at Cutwels, ..........it could be a mislabelled batch,

Dave K · Oct 18, 2017

tcncj said:
It's a messy chip
And chips seems to bind

I bought these ones
YG-1 TC163 Series Spiral Flute Metric Coarse Machine Taps - Uncoated For Aluminium

Must be different in the UK? The blue band here would suggest stainless tap. Oh well. If that hole is thru, I'd just stick with a spiral point tap.
That tap you linked to, appears to have a fairly mild twist to the flutes. I"m used to seeing a more aggressive spiral.

Some help with tapping

Cast Iron

Cast Iron

Cast Iron

Titanium

Stainless

Cast Iron

Titanium

Diamond

Aluminum

Titanium

Diamond

Cast Iron

Diamond

Stainless

Diamond

Titanium

Cast Iron

Diamond

Diamond

Diamond

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