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browne92
10-15-2012, 03:52 PM
Again, I searched before I asked.

After reading some other threads about tapping, I'm looking at the OSG spiral point taps. Two questions:

1. They come in various thread limits..H1, H2, H3, H5. Which is best for the average HSM type hobbyist?

2. They come either in black oxide or electralube coated, whatever that is. Anybody tried the electralube? It's only a couple of bucks a tap more, I don't mind spending the money if it really does help.

Thanks.

Bill

BigJohnT
10-15-2012, 04:22 PM
OSG electralube taps are fantastic. Hand tapping is a breeze with them even though they are machine taps. I use H2 up to about a #6 then H3 up to 3/4". I don't tap bigger than that...

John

Rich Carlstedt
10-15-2012, 08:05 PM
First, congrats on recognizing some of the finiest taps made today,. ( OSG)
The Black oxide coating is a anti-galling surface that prevents any adherance of tapped particles from sticking to the surface of the tap.
This works well with steels and aluminums

While I have never used the Lubricated taps you mentioned, I assume they would work for the above and high friction materials like phenolics or where you have to dry tap materials, ( other than Cast Iron ).

General shop applications do not need this iin my opinion....the blackened tap being better.

H1 and beyond are clearance designations.
"H" being "High"
1 represents about 1/2 of a thousandth .
H2 means about .001" oversize and is a good average tap, as Big John pointed out above.
If you plan to heat treat a tapped steel piece, then use a H3 or 4, as the holes close up after heat treating and the oversized hole will reduce maybe 2 sizes

Rich

SGW
10-15-2012, 09:48 PM
The appropriate H number also depends on the size of the tap. To use an extreme example, H4 for a 0000-400 tap would be way too much, but it might be appropriate for a 2"-8 or something. It also depends on the precision of the screw going into the tapped hole, requirements (or not) for ease of assembly, etc. Mostly I don't worry about it too much and buy whatever is listed as most common for a given tap size.

Oh -- FWIW I bought a set of taps from McMaster-Carr the other day. Since McM-C doesn't lists brand names I was curious what I was going to get. They turned out to be made by Widia ( www.widia.com ). I had never heard of Widia, but the taps appear to be top quality. I haven't had occasion to use them yet though.