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Tapping a Thread

Posted: Tue Jan 23, 2018 12:15 pm
by silversurfer1947
I am trying to tap a thread onto thin brass rod - in particular 0.8mm. I am doing something wrong as I keep shearing the rod so I only get short lengths. Fortunately, I only want fairly short pieces, but it would be nice to know how to do it properly.

Re: Tapping a Thread

Posted: Tue Jan 23, 2018 12:27 pm
by jarndice
Richard if you start the thread with a tap that is only just touching the inner wall of the tube and make the thread and then using lots of thin oil wind in then out frequently over very few turns using a bigger tap,
The more taps of ever increasing size you can use the better,
You should avoid starting with the Tap that is going to make the final thread, Do make sure you are following the original thread each time.
Exactly the same method should be employed with using "Dies" to make threads on the outside of a tube or rod.
Shaun.

Re: Tapping a Thread

Posted: Tue Jan 23, 2018 12:39 pm
by silversurfer1947
Shows how much I know - using the wrong terminology. I'm trying to get a thread on the outside of a 0.8mm brass rod. First time I've tried this. Initially, the rod would not fit in what I now believe to be the die so I tried the next size up (0.9mm). This worked fine. I then tried to cut the 0.8mm thread over the previous thread. I tried clamping the rod in a mini vice which has rubber facings, but the rod just kept turning, so i finished up holding it in a pair of pliers. That was when it kept shearing into bits.

Re: Tapping a Thread

Posted: Tue Jan 23, 2018 1:12 pm
by jarndice
The best way to "Get" a thread on a soft metal rod is to PRESS it on under pressure instead of using Thread cutting tools.
Shaun.

Re: Tapping a Thread

Posted: Tue Jan 23, 2018 1:21 pm
by silversurfer1947
jarndice wrote:The best way to "Get" a thread on a soft metal rod is to PRESS it on under pressure instead of using Thread cutting tools.
Shaun.
Is it possible to do this oneself at home? If so, how do you do it?

Re: Tapping a Thread

Posted: Tue Jan 23, 2018 1:26 pm
by silversurfer1947
I think it might be easier if I just cut the heads of M0.8 bolts. I just wanted to try to do it all myelf.

Re: Tapping a Thread

Posted: Tue Jan 23, 2018 1:46 pm
by silversurfer1947
Thanks for all the advice. I will give it another go. After all, it's just my time and a small length of brass rod.

Re: Tapping a Thread

Posted: Tue Jan 23, 2018 2:47 pm
by rochesb
When I was taught metalwork at school 54 years ago, I remember we used to use split (adjustable) dies, first we would chamfer the end of the rod, then open the die up wide in the holder with a grub screw & if I remember correctly we were told to go half a turn forward, half a turn forward, then half a turn backward to clear the swarf, & repeat the sequence until the desired length was reached after which we would unwind the die off the workpiece , back off the grub screw holding the die open a bit & repeat the thread cutting action until the thread was right.

Apologies if I am trying to teach my granny to suck eggs.......

Re: Tapping a Thread

Posted: Tue Jan 23, 2018 3:28 pm
by silversurfer1947
No need for apologies. Never did metalwork, so this is a new black art to me.