Form Tapping 316SS

[kccadcam]

High volume form tapping 8-32 threads in 316SS.
(120 holes per cycle running on a Makino A51nx Horizontal,,, would like to see 1200 holes in tool life)
I was looking at Kennemetal"s new Solid Carbide Form Tap but was told it will not work in SS.
What brand of form taps are you all using in SS?
I'm looking at Guhring, Emuge, and OSG.

Custom coolant thru #25 step drill to produce the hole and form the thread chamfer in one shot.

 

Kennemetal Solid Carbide:
https://www.kennametal.com/ca/en/products/p.t391-inch-form-e-bottoming-entry-taper-through-coolant-14-and-larger.3483113.html">//https://www.kennametal.com/ca/en/products/p.t391-inch-form-e-bottoming-entry-taper-through-coolant-14-and-larger.3483113.html

Amazing in 4340:
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Guhring:
https://www.guhring.com/ProductsServices/SizeDetails?EDP=9043770041660">//https://www.guhring.com/ProductsServices/SizeDetails?EDP=9043770041660

Emuge:
https://www.emuge.com/products/BU396A005006">https://www.emuge.com/products/BU396A005006

[CNCAppsJames]

Carbide form tap in SS.... I'm not aware of any tap companies where that is recommended. I've only seen recommendations in aluminum. Not to say it can't be done, I've just never seen that. I did do a turn-key in SS one time and the best form tap result I got was an OSG EXOPRO® XPF-OIL Taps. It was hands down better than Emuge (I was shocked), Kennametal, and Guhring. OSG's worth a cycle test.

(edit) and form tapping was the only way I could get through a whole pallet of parts on this particular turn-key. I do not recall the exact number of holes on the pallet, but I'm absolutely certain it was over 100 per pallet.

[gcode]

I did a bunch of 10-32 roll tapping in 316SS for the Solyndra boondoggle some years back
I forget what brand of roll tap I used...  edit .. I'm thinking it was OSG
I did make an interesting discovery though
The countersink makes a huge difference in tap life
We normally use 120­° c'sinks but tap life was terrible
Tap life got better with 90­° c'sinks, but 60° c'sinks were way better.. like 3 or 400% better

[MIL-TFP-41]

2nd for the OSG EXOPRO. We ran a bunch of 10-24 in 316. Had Guhring bring in their latest & greatest, didn't work in that material. OSG's were better by far. We tried with plain coolant (10% mix) and life was decent. Had operators use tapping fluid, life was great...but at the cost of putting tap fluid on each cycle. I could see 1200 holes with tap fluid...dunno if you can hit that with coolant. 8-32 is a lot easier than a 10-24...so maybe?

[HTM01]

10-32 we went with Emuge  rep said about 200 holes was still on same tap at 1000 with tap fluid

[gcode]

I did a bunch of 10-32 roll tapping in 316SS for the Solyndra boondoggle some years back
I forget what brand of roll tap I used...  edit .. I'm thinking it was OSG
I did make an interesting discovery though
The countersink makes a huge difference in tap life
We normally use 120­° c'sinks but tap life was terrible
Tap life got better with 90­° c'sinks, but 60° c'sinks were way better.. like 3 or 400% better

Okay G, edumakate the Newb!
Is this standard practice to chamfer the hole before tapping (roll or cut)?
Bearing in mind there's the lead on the tap....
I have always (we did at my place and we did at the previous place i worked at too) had the practice of drill (OSG EX-SUS-GDS so superb size) the ntap.
Then chamfer/first thread as last op when machine deburring all other holes and profiles too?
Granted 80% ally, but same process for titanium, stainless, yellow metals etc...

I have always chamfered threaded holes prior to tapping
Typically I do a 120° spot drill to chamfer size, then drill then tap
I use a 120° because a 90° c'sink kills the outside edges of the drill

In my Solyndra boondoggle project, the roll taps broke down quickly in holes prepped @ 120°
It got better when I tried a 90° edge break and really good @ 60°

So for that project it was
145° spot drill
drill
60° edge break
roll tap

It was an interesting project
We were building 316 SS weldments the size of a pickup truck bed
They were vacuum chambers used to manufacture Solyndra's magic solar cell tubes
We were allowed to roll tap on the outside of the chamber, but not inside the vacuum chamber.
That's because a rolled thread has a tiny groove at the crest of the thread and contaminates
can get in there and spoil the vacuum

[pmartin]

I did a bunch of 10-32 roll tapping in 316SS for the Solyndra boondoggle some years back
I forget what brand of roll tap I used...  edit .. I'm thinking it was OSG
I did make an interesting discovery though
The countersink makes a huge difference in tap life
We normally use 120­° c'sinks but tap life was terrible
Tap life got better with 90­° c'sinks, but 60° c'sinks were way better.. like 3 or 400% better

Interesting, Thanks! :_thumbup:

[gcode]

Thanks G
Yes agree - I've never spotted first - just straight in with the OSG drills.
 

When I first started working here I tried that.. but the guys refused to run it without a spot drill,
now matter how short a drill I used.
Management backed them up.. and I gave it up as a lost cause..
Every hole gets a spot check... then a spot drill ... no exceptions

[kccadcam]

Ok,,, going to go with the OSG EXOPRO XPF form tap.
Also going to go with the 60 deg chamfer on the custom coolant thru step drill.
no spot,,,, drill and tap....

[dcolin]

I'm not an expert with roll taps but I recently had great success rolling a difficult ISO M3x0.5 (depth 10mm along a 50mm wall) in Ti6Al4V.
I thought it won't work but it did nicely. About tool life it was a small batch and we did only 50 holes (with tapping oil though).
It was a Emuge tap so feel free to ask your application technician.

[CNCAppsJames]

My spot is always 2nd in the process because 90% of the time I'm pushing a Coolant Thru drill on a machined surface. If I'm pushing more than an 8xD drill, I'll nick the surface with a spot drill; just enough to clear the web, then send it. For more than 16xD I'm pre-drilling. Never tapping anything remotely that deep but I've had a few part over the years where the top of the DEEP hole was threaded for a plug/stop of some sort.

So Drill, Spot, and Tap/Threadmill and occasionally ream is my process.

I sometimes have to ream because inspectors can be idiots and refuse to take into consideration it's the HOLE location that matters and that the thread creation process will push burrs that can throw out True Position. Or rather, because they only know how to load the CMM and don't know how to truly inspect a part that the True Position is out. But, I digress.