- Thread starter ronan
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brightspark
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depends if your using for production or hobby use
ronan
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They go for decent money on fleabay.
Hood
I am obsessed.
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Die heads are much better than using a normal die as they open so you can reverse off the thread that has just been cut.
Finding them at a decent price though is pretty rare.
I have a CNC lathe so I don't really have a need although a die head would actually be quicker in most cases and they are still used on CNC lathes by some.
Finding them at a decent price though is pretty rare.
I have a CNC lathe so I don't really have a need although a die head would actually be quicker in most cases and they are still used on CNC lathes by some.
Coventry style die heads are designated by 1/4, 5/16, 1/2, 3/4, and so forth and are nearly always labeled as such providing the etching is still visible. The size refers to the Max diam of thread that specific head is capable of doing, that is the rule of thumb anyway. It is possible to get the die chasers ground so they are not as deep and it may be possible to get something like a M7 thread in a 1/4 die head (6.35mm) but as i said but there will be a limit due to the diam inside the head and its movement when it releases and enough space for swarf evacuation before it becomes a problem.
Normally you use the correct size of die head for the job in hand otherwise you will just end up straining/ damaging it. Obviously trying to do a 1/4 thread with a say a 1 inch die head will not end very well because a head of that size will have lack of sensitivity for small threads as its designed for much larger and will probably strip the thread when the die head releases. Die heads and and dies are not a particularly cheap pass time, you generally have different dies to suit different materials basically the rake alters on the grinding of the die to max out its potential like any tool. They are generally not suited to manual lathes but something could be rigged up but they do need a positive stop to release the die head so it does not chew up the thread. They can be used in both horizontal and vertical orientations so technically if you can you could use one in a pillar drill to produce quality threads and machines to use them in this orientation were used in past years, they are still a very fast and highly effective method to produce threads which is grossly underused these days...... mainly because people don't understand them as they are a bit old school now.
Die heads are particularly good at long slender threads that are still hard to achieve by other 'machining' means including traditional slant bed cnc machines. In the right circumstances they will outperform a cnc using single point cutting or make a thread possible a cnc can not achieve very easily like say a 5 mm thread 70 mm long as it will require a center and lots of side load. A die head does not have this problem as it only puts torque in the bar to be threaded and no side load. A cnc will typically use multi passes to produce a thread a die head can one hit machine a thread but as always its using the right tool for the right job at hand or what you have available that works.
I use die heads a lot and often do jobs for bigger cnc shops that cant tackle these kind of jobs with long slender threads
Normally you use the correct size of die head for the job in hand otherwise you will just end up straining/ damaging it. Obviously trying to do a 1/4 thread with a say a 1 inch die head will not end very well because a head of that size will have lack of sensitivity for small threads as its designed for much larger and will probably strip the thread when the die head releases. Die heads and and dies are not a particularly cheap pass time, you generally have different dies to suit different materials basically the rake alters on the grinding of the die to max out its potential like any tool. They are generally not suited to manual lathes but something could be rigged up but they do need a positive stop to release the die head so it does not chew up the thread. They can be used in both horizontal and vertical orientations so technically if you can you could use one in a pillar drill to produce quality threads and machines to use them in this orientation were used in past years, they are still a very fast and highly effective method to produce threads which is grossly underused these days...... mainly because people don't understand them as they are a bit old school now.
Die heads are particularly good at long slender threads that are still hard to achieve by other 'machining' means including traditional slant bed cnc machines. In the right circumstances they will outperform a cnc using single point cutting or make a thread possible a cnc can not achieve very easily like say a 5 mm thread 70 mm long as it will require a center and lots of side load. A die head does not have this problem as it only puts torque in the bar to be threaded and no side load. A cnc will typically use multi passes to produce a thread a die head can one hit machine a thread but as always its using the right tool for the right job at hand or what you have available that works.
I use die heads a lot and often do jobs for bigger cnc shops that cant tackle these kind of jobs with long slender threads
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Here is a link that gives you the head sizes etc. Somewhere out there there was a good page someone set up explaining all you need to know. I seem unable to find it currently.
https://www.threadtools.com/Products/Coventry-Die-Head-Chasers?gclid=COCrroCL19ECFRITGwodttkDqw
https://www.threadtools.com/Products/Coventry-Die-Head-Chasers?gclid=COCrroCL19ECFRITGwodttkDqw
On the left hand, second from bottom of this image is one such long slender thread. From memory these were actually M5 x .8. The shoulder for the thread was turned in one hit with from 7/16 (11.11 mm) 304 stainless so a 3 mm one hit cut probably taking no more than 15 - 20 seconds. Sometimes old school is good.
Wendelspanswick
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You can also get internal cutters - Coventry Tapping Heads?
I have a pair of heads that came in a job lot of bits, never used them.
I have a pair of heads that came in a job lot of bits, never used them.
