Hard time tapping brass

[kd4gij]

When taping NPT in harder material I usley bore the taper first it makes taping alot easer.

 

[george wilson]

Typical of brass to squeal and make tapping too tight.

I expect your tap is just not SHARP enough. The brass seems to SQUEEZE back onto the tap,making it too tight. Here's a parallel: I know you only tapped aluminum with your tap. But if you file brass with a brand new file,then file steel with it,and go back to filing the brass,you'll find it doesn't file as good. I suspect that something has taken the prickly sharp cutting tips on the tap off just a bit,at least. A little sand in the aluminum casting? Paraffin doesn't hurt,as said.

Nothing wrong with 360 brass. BUT,IF YOU SOLDER IT,DON"T TRY TO USE LEAD SOLDER. 360 likes lead free,or silver solder. Lead won't work. Remember this. And most round stock is 360 unless it's bronze.

 

[kd4gij]

Where I used to work we always used a new tap for brass. Never one that had ben used on steel. But that isn't practical for a hobbyest.

 

[Bill C.]

My Tip

When putting gas threads in brittle materials like brass use your lathe if you can as it's safer and more accurate , to get it all centred and solid .
Put the tap in the tailstock chuck , set the tailstock lock to a slight free slide and advance the taper tap into the hole with the tailstock feed screw then gently rock the lathe chuck back and forth about 1. 6 of a turn and advance the tailstock feed in as you do it . Progress like this till you have two & a half full revolutions of the lathe chuck , it won't be long before you get the first few threads made and from then on it's a case of turning the lathe chuck back and forth about 1/4 of a turn at a time several times in each place then advance the tap a bit more to form the perfect thread.

If you have a carriage stop place it in front of the tailstock to give you an indication of when to stop so you don't go & break the tap by bottoming it out or start pushing it too far down in to a thin wall weakening the item . .


In a previous post someone said that brass does not need lubrication , for some strange reason I seem think that 50 years ago I was taught to give such things a squirt of paraffin to flush out the swarf , this stops it squealing and the tap binding up on the swarf which may cause the fitting to split .


Don't use compressed air as you're like as not liable to stick some metal in yourself especially in your eyes.

I seem to remember kerosene and paraffin mixture. Using enough kerosene to soften the paraffin to make a grease like consistency.

- - - Updated - - -

So I made my first actual part from scratch on my lathe. Everything before was simply maching down or facing stuff. I am really happy and excited that I actually made something I needed and it worked! Not to mention I couldnt even find the part.

I got a free air hose reel for my shop, no hose, but I had a good one for it. When I go to put a fitting on the inlet, I found it was cracked. Its made from brass. I take it off and apart. It looks pretty simple. I figure I could make a new one.
I got a peice of 1 inch brass round stock from ebay, and long story short, made a new one.
My problem was when it came time to tap the ends. One end was just regular threads to go on a mounting stud, the other was pipe threads for the inlet. When I went to tap the holes, it was extreemly difficult to tap. I mean so tight that I thought the tap was going to break! It also squeeked when doing this. I have tapped many things before, lots of steel and never had this much trouble tapping a hole. I tried 3 different types of lube, two made for cutting/tapping, and one that wasnt, all with the same result.
Why were these holes in soft brass SO hard to tap? Is this normal for brass? This is the first time I have really worked with brass. Machining was super easy, but tapping almost impossiable.

The part itself is the inlet, it has 2 grooves for o-rings. Another peice rotates around this, which is what the hose attaches to. It also has a snap ring to hold it on. I simply used a parting blade to cut the o-ring grooves, and actually to cut the larger center groove also. I then ground it down real thin to cut the snap ring groove. Drilled it for the air and milled two flats for a wrench, since it was made from round stock, instead of hex like the original. I made it a little longer on the end with the snap ring because I dont have a bottoming tap, and I wanted it to thread all the way on the mounting stud. I left the inlet end bigger, cause I wanted it thicker, thats where it cracked on the old one. Once I put it together, it works like new!

Interesting project, The pipe tap you used was it a stub style, short without much lead? I learned this the hard way, assigned to make nozzles on a turret lathe. A normal pipe tap was to long and I ended up having to make the nozzle opening bigger than it should be.

 

[kwoodhands]

So I made my first actual part from scratch on my lathe. Everything before was simply maching down or facing stuff. I am really happy and excited that I actually made something I needed and it worked! Not to mention I couldnt even find the part.

I got a free air hose reel for my shop, no hose, but I had a good one for it. When I go to put a fitting on the inlet, I found it was cracked. Its made from brass. I take it off and apart. It looks pretty simple. I figure I could make a new one.
I got a peice of 1 inch brass round stock from ebay, and long story short, made a new one.
My problem was when it came time to tap the ends. One end was just regular threads to go on a mounting stud, the other was pipe threads for the inlet. When I went to tap the holes, it was extreemly difficult to tap. I mean so tight that I thought the tap was going to break! It also squeeked when doing this. I have tapped many things before, lots of steel and never had this much trouble tapping a hole. I tried 3 different types of lube, two made for cutting/tapping, and one that wasnt, all with the same result.
Why were these holes in soft brass SO hard to tap? Is this normal for brass? This is the first time I have really worked with brass. Machining was super easy, but tapping almost impossiable.

The part itself is the inlet, it has 2 grooves for o-rings. Another peice rotates around this, which is what the hose attaches to. It also has a snap ring to hold it on. I simply used a parting blade to cut the o-ring grooves, and actually to cut the larger center groove also. I then ground it down real thin to cut the snap ring groove. Drilled it for the air and milled two flats for a wrench, since it was made from round stock, instead of hex like the original. I made it a little longer on the end with the snap ring because I dont have a bottoming tap, and I wanted it to thread all the way on the mounting stud. I left the inlet end bigger, cause I wanted it thicker, thats where it cracked on the old one. Once I put it together, it works like new!

The drill size is marked on the tap in most cases.This is for 75% of the thread. Drill with one size larger for about 60% of the thread. I use Castrol MolyDee lubricant .I am told it is not sold anymore but Castrol has a new lubricant to replace the MolyDee.
360 and naval brass are the two brass alloys I am familiar with. 630 brass machines well but tends to grab cutters.A bottom tap would come in handy, make one. Mill flutes on a steel round,bevel the end slightly and run a die over it.You only need a few threads if you reduce the diameter of the shank less than the threads. The improvised tap is harder than brass and should work without hardening for several holes at least.I have done similar work and used drill rod. Did not harden and temper as it was a one time use.

mike

 

[Round in circles]

ha, just realised paraffin is a wax for the USA folks .. the paraffin UK style I was referring to is what you guys over the pond call kerosene


Tapping there are four types of tap I know of :-
(1) A taper or first tap this is to form the first three or four full threads , leaving several part formed threads below these full threads .
(2) Then you can go to a second tap which has hardly any taper .
(3) Lastly is the bottoming tap this only has a slight taper on the first two threads even if the tap is a full taper along its length gas tap as its name suggests it's for taking down to the bottom of a blind hole. This is where a decent depth gauge comes in handy , so you can calculate how deep down the tap is before you bind & break it at the bottom fo the hole .
(4) The skip tooth tap previously mentioned .



When machines are used to tap holes the feed & speed are critical , as an apprentice we spent many an hour working out the feeds and cutting speed of all manner of materials g
All hell was let lose us if we got it wrong and bust a drill or self extracting tap that was being use to semi auto tap holes using the pillar drill stand & table . Nowadays with CNC and all manner of available programmes it just so easy apparently as all calculations are done for you if you have the debugged programme to hand & everything is rock solidly clamped up for precision and no vibrations.

Getting tight & squeaking in brass ......always use a first and second tap whenever possible , all you need do is back off the tap so the flutes of the tap breaks off any burr behind it and move it forward another 1/4 turn and repeat till the hole is done.
After a while of using first and second taper taps in brass it's a doddle to tap brass , as you'll have like as not broken a couple of taps getting the experience.

 

[chuckorlando]

It sounds like you are but worth a mention none the less. Make sure your breaking the chip often. If not that sucker will lock up on you real fast. If possible get the chip out of the way as well

 

[KevinD]

Given I've never tapped brass, but have drilled a fair bit, I'm wondering if it might be worthwhile modifying the tap as one does a drill bit to cut brass. Since a sharp drill bit bites on brass, chamfering a chisel bit on the cutting edge of a drill bit allows it to cut brass could the same work for a tap? I suppose the cutting face of the tap is already, kind of, a chisel face. And it would require a second tap to make the finish cut, just wondering. I'm talking myself out of my own idea already )

Kevin

 

[Bob Korves]

So I made my first actual part from scratch on my lathe. Everything before was simply maching down or facing stuff. I am really happy and excited that I actually made something I needed and it worked! Not to mention I couldnt even find the part.

I got a free air hose reel for my shop, no hose, but I had a good one for it. When I go to put a fitting on the inlet, I found it was cracked. Its made from brass. I take it off and apart. It looks pretty simple. I figure I could make a new one.
I got a peice of 1 inch brass round stock from ebay, and long story short, made a new one.
My problem was when it came time to tap the ends. One end was just regular threads to go on a mounting stud, the other was pipe threads for the inlet. When I went to tap the holes, it was extreemly difficult to tap. I mean so tight that I thought the tap was going to break! It also squeeked when doing this. I have tapped many things before, lots of steel and never had this much trouble tapping a hole. I tried 3 different types of lube, two made for cutting/tapping, and one that wasnt, all with the same result.
Why were these holes in soft brass SO hard to tap? Is this normal for brass? This is the first time I have really worked with brass. Machining was super easy, but tapping almost impossiable.

The part itself is the inlet, it has 2 grooves for o-rings. Another peice rotates around this, which is what the hose attaches to. It also has a snap ring to hold it on. I simply used a parting blade to cut the o-ring grooves, and actually to cut the larger center groove also. I then ground it down real thin to cut the snap ring groove. Drilled it for the air and milled two flats for a wrench, since it was made from round stock, instead of hex like the original. I made it a little longer on the end with the snap ring because I dont have a bottoming tap, and I wanted it to thread all the way on the mounting stud. I left the inlet end bigger, cause I wanted it thicker, thats where it cracked on the old one. Once I put it together, it works like new!

There are tapered pipe reamers available to use after drilling so the hole is tapered like the tap. That should make tapping a tapered thread easier, but I must confess I don't have any and have never used one.
-Bob Korves