Tapping brass

[ozzie46]

A quick question about tapping brass. I know that you should not use a file on brass that has been used on steel,(it doesn't cut well). Is it the same way with a threading tap?

Ron

 

[gbritnell]

Hi Ron, I think there is a little confusion here. You should always try and use a sharp tap on brass but I don't understand why you shouldn't use one that has been used to tap steel other than the fact that it might be a little dull. I use HS taps down to 1mm in both steel and brass with no trouble.
gbritnell

 

[ozzie46]

Thanks gbritnell

I was just worried about difficulty in tapping. Have lots of holes to tap in both cast iron and brass. ;D ;D

Ron

 

[bmuss51]

i never herd of a don't, like using a file on brass after it was used on steel.but the thing i would and do suggest is to use a file card on the file after steel and before you use it on brass and make sure the file is clean of all build up so it won't gouge the brass.
as for the tapping of brass which is done the same way as steel and as aways be sure you use plenty of lube.but if you have alot of holes to tap i would suggest to tap the brass first with a sharp tap. before you do the cast iron because the cast will dull the tap alot faster. yes in my findings the cast will dull a tap faster than steel.and alot of this is because the cast will have hard spots and depending on the size and quality of the casting it could even be impossible to tap.like on some of your smaller parts.

 

[Jasonb]

The main thing is a sharp tap, use it dry on both brass and CI, neither need lub unless its SG Iron then I find that cuts better with soluable oil.

Jason

 

[ozzie46]

bmuss51
(i never herd of a don't, like using a file on brass after it was used on steel.)

I've read it in several old maching articles plus I have files that cut stell well but glide over brass. I use files never used on steel and they cut brass very well.

Thanks guys, I have a lot of holes to tap, 2-56 and 4-40, so I'm just trying to use every advantage I can. Have almost 300 holes to do,most in cast iron. I'm sure I will develop a great dislike for tapping. :big: :big:

Have ordered a few more taps just in case. : : :

 

[dwentz]

I think part of the file issue is that any small filings of steal will mar the brass. I do not separate mile files based on material, but if I am filing brass or aluminum I make sure the files are good and clean.

Same for taps, make sure they are extra clean before using in softer material.

Dale

 

[Noitoen]

Have almost 300 holes to do,most in cast iron.

I would get myself a couple of "machine taps?" don't know the correct English name for them (they're black and one tap does all), set the cordless drill's chuck torque limiter to a suitable value (lowest possible) and tap away. I've tapped hundreds of holes in copper bars using those taps and WD40 as a lubricant with great success ;D

 

[deverett]

...but the thing i would and do suggest is to use a file card on the file after steel and before you use it on brass and make sure the file is clean of all build up...

If the file card is made of steel, then it will tend to blunt the file. The best thing to clean a file with is a bit of flattened copper pipe. Push it along the line of the teeth and it will soon take up the profile of the teeth. The copper being much softer than the file will not do it any harm.

Dave
The Emerald Isle

 

[Tin Falcon]

"Machine taps come in a couple of flavors. Spiral flute for blind holes and spiral point for through holes you can use spiral flute in through holes but not visa versa. also forming taps for dutile material.

Tin

 

[ozzie46]

Thanks for all the info guys.


Ron

 

[rklopp]

I find that brass tends to squeeze down on taps, somewhat like plastic. I think this has something to do with the way brass makes weak chips. The only ways I see to combat it are to use fresh, sharp, uncoated taps, or to buy special taps with extra radial back-off, so less of the thread flanks rubs the hole. I have never tired to buy these special taps. You'd probably have to buy 1,000 to make it worthwhile on a cost-per-tap basis.

 

[Stu Miller]

Spiral point taps will work in blind holes with a bit of care. If you can drill the hole a bit deeper than you need to tap, you will provide clearance for the chip pushed ahead of the tap by the spiral point.. You can back the tap out after you feel it beginning to push down on the accumulated chips and remove the chip. Depending on tap size, a sheet rock screw, a sheet rock nail with a strong magnet on the head (for steel), or a long thin scribe will remove the chip so you can tap a couple of threads deeper.

You can also hit the tip of a spiral point tap with a grinding wheel to remove the alignment point plus a couple of incomplete threads to make an effective "plug" tap to gain a couple more threads.