Thread: Tapping Hard Material

I find the H&F tap setts to be just as good as Sutton.

As for sharpening them give it a go as it cant hurt anything.

I have sharpened up taps myself with both a dremel with a cutting disk on it and a angle grinder with a tin 1mm disk on bigger taps and both approaches worked fine.

As you say the 6.8mm drill should make it a lot easier on the tap, must be hard stuff, though his drill went through it fine by the sounds of it.

Dave

Maybe the drilling has work hardened the holes - I've had this happen to me several times.
I'm not sure if you have drilled all the holes already but if not make sure the drill is freshly sharpened and drill the holes using copious coolant so they don't work harden.

John how urgent is it? I'd suggest trying another quality tap, Sutton is sadly not what it used to be. Likewise, I wouldn't touch cheap taps with a barge pole, been there done that. I buy my taps and dies while overseas with work, but failing that ebay is a good source. I was shocked the first time I used a really good quality tap just how different it could be, and from then on just slowly built up my tap/die collection with very good quality units and have never had a problem since.

Likewise I highly doubt you'd get a really good result with a diamond file. If you compare a really good tap and a mediocre tap side by side they can look identical, yet they're quite different to use. A cutter grinder will hold tight tolerances and you're just not able to achieve that by hand. Having said that, if the tap is blunt then give it a go, it's buggered already so you really have nothing to lose.

Pete

I agree with Pete on this, a good quality tap is a joy to use over a cheaper one. Is the sutton HSS? I use mostly gun nose dormers, I couldn't find a 5/16 BSW on ebay in the gun nose, but i did find a no.1 DORMER 5/16 - 18 BSW HSS E531 No1 TAPER FIRST TAP | eBay and a UNC DORMER E055 POWDERED SPIRAL POINT THREADING TAP FOR STAINLESS UNC 5/16-18-2B | eBay
I've never broken a dormer tap, and i have absolutely destroyed a few Suttons, Frosts etc. They are worth the extra dollars IMHO.

Just to throw a little cold water around, a previous employer used to have parts machined from Bisalloy and some of those had tapped holes although this was usually avoided if possible. The most favoured trick was a softer (eg normal steel) insert or welded on pad for the actual tapped thread. However, occasionally holes were tapped directly. Never by hand. Always using a CNC machine so that there was a rigid (and constant) squareness to the tap, lots of coolant and powered down feed. Quality taps were a must.
You might be able to tap hard stuff by hand but you can't afford the tap axis to wiggle around and it has to be fed into the hole so that it bits and cuts. Skating on the lip of the hole is not going to do any good.

Michael

I have broken a couple of Sutton taps (using tapping fluid) in recent months. I broke one off when tapping a crankshaft journal. It has me thinking they are made of cheese. The last one that let go was an M4 a couple of days ago in Aluminum. I spent 1 1/2hrs drilling it out with a carbide bit. The Bordo taps are not much better unfortunately. Next up it will be Dormer for me which I hear are exceptional and reasonably cheap from Ebay UK.

Originally Posted by Michael G

You might be able to tap hard stuff by hand but you can't afford the tap axis to wiggle around and it has to be fed into the hole so that it bits and cuts. Skating on the lip of the hole is not going to do any good.

Michael

Agree. I've been doing a pile of 316 and 304 recently. I hate tapping stainless especially anything less than 10mm - at least you can use a fair bit of force on an M10 tap.

Buy good taps, save the cheap ones to lend to your friends. They'll bugger a good tap anyway, this way it doesn't matter.

PDW

Guys,
thanks for all the comments and advice.
I will follow up on the Dormer links.

The original Sutton tap is marked "Z3 HSS".
The only tap I could get this afternoon was a Sutton Tungsten Chrome - it only got half-way through one hole when I called it quits.

To add insult, the intermediate tap in the Sutton set is marked "Goliath L.H." - the mate can take that up with his supplier.

Discussions are scheduled for Friday.
John.

Hello John, a procedure I have had success with is to use all three types of tap in order then repeat the process. That is, use the taper tap until it becomes tight, remove, next the intermediate then the bottom tap and then the taper again etc. until finished. The theory being that each tap type cuts a different, smaller part of the thread and is therefore easier to use, there is less chance of a breakage and wear is distributed across three taps. This procedure does take more time but probably less time than removing a broken tap, it is also useful if you are trying to tap a hole in position with limited access.
Mm.-Phillip.

Job done.
Another two new Sutton HSS taps.
Both taps are distinctly worn with some broken edges.
The Goliath L.H. tap was a wring-in by the mate.
I tried tapping grease, but formed the impression that fluid works better.

Final technique was:
- rigid clamp to table with tap in 3-jaw drill chuck,
- fluid applied to hole and tap,
- tap entered with high downward pressure,
- no back-off to clear swarf - continuous tapping until tap slips in chuck,
- transfer to bench vice, remove tap and clean hole and tap,
- more fluid and tap with hand wrench without back-off,
- complete hole.

Now reviewing a possible method to sharpen the taps.
Dremel clamped horizontally to mill head on Y-axis , Spin Indexer on table along X-axis with collet to hold tap.
Tap rotated in collet until top and bottom cutting edges are equally spaced sideways from tap centre.
The offset should give the cutting edge clearance.
Z axis sets depth, Y-axis sets cut, X-axis feeds the tap under the grinding wheel, indexer rotates to next flute.
A sharpened taper tap may need the intermediate tap to follow to get size correct in the job, depending on relief provided behind the tap cutting edge.

Thanks for all the help,
John.

Hi John,

Glad to see you got the job done.

Here's a related question, has anyone got any experience using solid carbide taps for tapping hardened steel?

Apart from the price, which is already a killer for me, how well do they work? Carbide Taps | Allen Benjamin

Ebay

5 16 18 Solid Carbide 3 Flute Tap Allen Benjamin | eBay

Regards
Ray

I mostly favor imported top quality HSS taps, except when knowingly tapping into stuff that is likely going to ruin my expensive good HSS tap....

Carbon steel taps are much cheaper than HSS, and, incidentally, carbon taps are slightly harder that HSS taps. And easier to remove if broken (yes they are brittle and break easier than HSS, but then they can be shattered out of a hole with a punch, which HSS cannot). The problem is that most carbon taps sold today are cheap crap quality, and/or not sharp to begin with because cut instead of ground. But there are still well made, properly ground carbon taps being made and well worth buying. And probably a good choice for exactly the sort of job described here by the OP. One can buy 3-4 ground quality good carbon taps for the price of one good HSS tap. Chris

Genuine Dickson toolholders are around 62 to 64 HRC on the surface and Carbon steel taps are between 58 and 60 HRC. A HSS tap from any decent manufacturer will be 63 to 65 HRC so I know which one I would choose in a difficult situation like this.