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outback
10-07-2014, 11:04 PM
I seem to get poor results using the Titanium nitride coated (Gold colored) taps. Today I was tapping 6-32 in A-2. First hole went well but after that the tap was ready to break. Then I used the same tap in 1020 cold rolled with plenty of oil and the tap seized. I managed to get the drill press shut down and reversed before the tap broke altogether. I have experienced this before in
the past.

I also have 4-40 taps coated with titanium nitride and they seem to work great. I tapped about 50 holes in A-2 with one 4-40 tap. At the end the 4-40 was still like new.

Coated taps seem like a great idea since the coatings are hard and slippery but I have mixed results.

Anyone else experience this?

Jim

Toolguy
10-07-2014, 11:41 PM
In my experience, you have to have a quality tap under the coating for it to hold up. The coating will help with wear resistance, but if the metal underneath is not up to the job the coating won't help it. The same with the Chinese TiN coated drill bits and end mills.

J Tiers
10-08-2014, 12:00 AM
All too many of the drills appear to be "hardened 1018" with the "gold pixie dust" on them. Th rest are glass-hard, and about as tough as glass, too.

I wouldn't think of taps as another market for the "pixie dust", simply because everyone thinks they know how to use a drill, but a lot fewer think they can use taps. However, you never know..... maybe the drill market is saturated

outback
10-08-2014, 03:59 AM
These were Cleveland brand taps made in the USA. I avoid cutting tools made in China or India.

I just noticed the TIN coated taps cost less than the OSG Black Oxide or OSG Electalubing. Maybe I'll try OSG taps.

Taps are not the place to save money.

Jim

Old Hat
10-08-2014, 04:40 AM
You need to supply the tap-drill size you used for each thread mentioned, and what resulted diameter said drill gave you.

You need to keep your effective thread %age under 70% to ensure trouble-less tapping.

outback
10-08-2014, 07:11 AM
Tapping in tool steel I went one drill size larger. For 6-32 the normal tap drill size is #36 so I used a #35 and the same for the 4-40.

Jim

Old Hat
10-08-2014, 08:06 AM
Good, I ask because I'm supplyed with drills from small number drills, all the way to 2 1/2"
from all over the world. I now stop after the first peck or two and check hole diameter.

I'm getting holes from size on size to so bad It takes several resharpennings to get a good size.
I've found misshapened gullets in most cases. The gullets offen not even close to symetrical
shape or web off to one side.

Your 4-40 tap-drill could have given you a wide hole, and your 6-32 could have given your a near size hole.
Now if your tap is of lesser quallity or a non-preffered flute type, or a less effective tapping fluid
it won't have much chance.

PS;
6-32 and 1/4-20 are just about the weakest tap sizes, due to tooth size to diameter ratio being so large.
Long ago some tool-shops would turn away work, if not allowed to go to the stronger fine thread options.
One in particular wouldn't build a tool if 1/4-20s were mandated instead of 1/4-28s.

Fasttrack
10-08-2014, 10:04 AM
I prefer bright taps from OSG but I have been known to use Hertel taps, too. Despite being made in China now, the Hertel ones hold up well. I even had a 4-40 that put several hundred threaded holes (under power) in 304 SS with never an issue. Anyway, I prefer bright because I have been doing equal amounts of work in steel and aluminum. Many of the coatings gum up with aluminum.

If they are through holes, I highly recommend spiral point taps. If blind, I recommend spiral flute taps. Speeds things up quite a bit!

michigan doug
10-08-2014, 10:05 AM
My biggest improvement in tapping performance was when I switched to gun taps (aka spiral point taps) Note that spiral point taps are VERY different from spiral FLUTE taps.


The other thing I have decided is that sets of taps are generally lower quality that taps purchased individually. There are exceptions, but they are exceptions...


Spiral point taps eject the chip forward out of the hole, and so work best with through holes. You can use them in blind holes if you drill it a little deeper than normal, or you stop and remove the tap several times to remove the chip load.

Normally you just drill the hole, lube with your fave lubricant and drive the tap through. No stopping, no forward/reverse to break the chip. Just zoom and you're done. Of course, hole size and tap speed is still a big deal, and you lose very little strength dropping from an 80% thread to a 70% thread if you're in a difficult material, etc.

I don't even look at the coating any more.

I avoid cheap generic chinese taps.

Old Hat
10-08-2014, 11:17 AM
For hobby machinist's consider dropping a 20 or a 50 on a "lot" of cutters, or taps, or drills
or the whole sheBang.
http://www.ebay.com/itm/MACHINIST-LATHE-MILL-Lot-of-Machinist-Taps-for-Threading-Wax-Coated-for-Protect-/171484245491?pt=LH_DefaultDomain_0&hash=item27ed41edf3
On any day 15 lbs of tooling might cost you less than lunch for two.

I regularly run a page or two and see what pops up.
This outfit has a rare favorite today.
A magnetic cylindrical square !!
see it pays to check it out.
http://www.ebay.com/itm/MACHINIST-TOOLS-LATHE-MILL-Ralmikes-Tool-Die-Makers-Square-in-Wood-Case-/191133474015?pt=LH_DefaultDomain_0&hash=item2c80715cdf

One day I found a 9" Level and an 18" grooved scale !! Two of my most usefull tools.