understanding taps and dies

[aggromere]

Well, now that my new metal mini is on the way I thought I would begin to understand the concept of internal and external threading, but I have a long way to go.

I understand that taps do internal threads and dies do external threads and that when I get the hang of it I will get me a triple start set. I have a wide range of questions and if anyone else has questions I didn't ask, go ahead and throw them into this thread.

1. How do you know which size hole to drill to go with which tap?

2. How do you know which size dowel (or whatever piece you are using) is for which size die?

3. What do the numbers mean? In looking at taps and dies I see a series of numbers, I think 3. I guess one is threads cut per inch, but what are the rest of them?

4. I have a pen blank with a pattern. I cut it in half for upper and lower barrels. I drill one piece for internal threading and cut a tenon on the other piece for external threading. I thread them. When assembling the two pieces is there anyway to make sure the pattern lines back up? (Would I have to cut a rod the size the tenon should be, thread it, then put it in the threaded hole, then drill out the other blank to accept the rod, then line them up, mark and then glue the rod in place?)

5. When cutting external threads on a pen barrel do you drill out the blank first and then thread, or thread and then drill (like for the nib end of a pen). I would be just threading the blanks so they would fit back together in the final pen. I would still be using tubes and kit threaded couplers to hold the nib in.

6. Before I buy a triple start set, what 2 or three sizes of taps and dies would you recommend I get to start with that would be useful in making pens?

Any input would be most appreciated. I'm going to get me a bunch of plastic rods and practice on them when I get my lathe.

 

[mredburn]

Here is a link to the recomended drill sizes for different tap sizes. http://www.victornet.com/reference/Tap_Drill.html
The dies are usually marked for the diameter of the rod they will work on ie. 1/2-16 1/2 rod 16 threads per inch.

in order to match patterns on outer diameters you may have to file or trim the end that is tapped (female) down until the male side will line up. If your new lathe will do threading you can thread both inner and outer threads at whatever diameter you want to make it. your not constrained to standard set sizes. This something you really need to learn, ALthough you can use taps and dies to thread with it constrains your parts to diameters that fit in the tap and die set. Most of the time the tubes and blanks will either not have enough material to use one size and the next size up will make your pen heavy and awkward. ALmost all the thread sizes on the kit parts you may want to match up to are non standard sizes. Your tap and die set wont work.

 

[randyrls]

4. When assembling the two pieces is there anyway to make sure the pattern lines back up?

The only way to do this is to use single start threads. Multi-start threads are different, but can be postitioned at one of 3 or 4 positions.

6. Before I buy a triple start set, what 2 or three sizes of taps and dies would you recommend I get to start with that would be useful in making pens?[/quote]


Multi-start threading is certainly doable on the metal lathe, but I would think of this as "advanced threading". You would not need the tap and die, but could do single point threading. Take a look at some of the videos by "tubalCain" on YouTube.


Internal multi-start threading is way up there on the difficulty scale.

 

[workinforwood]

The tap and the die are matches. M7x.75 is metric and the tap and the matching die will say the same thing. The hole for a tap will be 7 - .75 which equals 6.25 drill bit. The OD for the die will be 7 mm. So you need a set of metric bits in the .25 range. Lots of people have them. I really like to use single threads in the .75 metric range. They look good, they hold good, they do not come unthreaded easily like a triple thread can. The sizes I use most often are between M6 and M10. Always oil your taps. Makes the threading better and the taps last longer..especially if you get into threading aluminum and brass which tends to stick to the taps and dies. Running a thread with a tap or die, requires hitting it nice and square to the stock..this is the key to success really. If you try and tap or die something and you are not running square on, then you are likely to strip out the threads, not to mention if the threads to work, the pen will not go together straight. Cutting threads using the machine is very simple to do as well, but that's not a lesson I can give online. It's more of a hands on thing.

 

[workinforwood]

4. I have a pen blank with a pattern. I cut it in half for upper and lower barrels. I drill one piece for internal threading and cut a tenon on the other piece for external threading. I thread them. When assembling the two pieces is there anyway to make sure the pattern lines back up? (Would I have to cut a rod the size the tenon should be, thread it, then put it in the threaded hole, then drill out the other blank to accept the rod, then line them up, mark and then glue the rod in place?)

not really the best way to do it. You can do it that way, but if it is a fountain pen, then how do you get inside the tennon to refill the pen? If it is a rollerball, how do you change the refill? A quality kitless pen is a lot more work than what you might see in a finished picture. You need to build the parts, just like kit parts. Pull a fountain pen kit completely apart and see all the pieces..you need to make most of those. They are done like this for reasons. To refill the pen is one, and then you have to think about how the pen cap will go on and come off without unscrewing the nib section at the same time. This is why a kit pen is several peices. You have a coupler piece and a section that screws into the coupler. The coupler connects to the pen. You can make the pen body with a tennon and the tennon is the coupler, but then you still need to make a grip to go into that tennon and the nib feed screws into the grip which screws into the coupler. Got all that?

Rollerball pens are just the same as fountain pens, but you have a cone instead of a fountain nib..so there is one less piece to do..your nib cone and your grip can be a single piece but still needs to screw into a coupler..the coupler being your threaded tennon on the pen body. Or...you can have a threaded cap on the back of the pen to change the refill and the rest of the pen all one piece...but..how you going to drill out the nib cone with that much depth ??? There's a lot of engineering in a good kitless pen. Now you have more questions to work out.

 

[rherrell]

When using a tap and die the size you need all depends on the material you're threading. If I'm making outside threads on plastic I might take 2 or 3 thou. off nominal. If I'm doing the same threads in steel I might take off 20 or 25 thou.. Same with inside threads, I use a smaller drill for soft materials (alum.,brass, Delrin, plastic) and a larger one for harder materials.
You can use a chart to get you in the ballpark but it's really going to take alot of trial and error to get the right combination, at least that's how it works for me.:biggrin::wink:

 

[Minotbob]

For those of you that have an iPod or iPhone there are a couple of $.99 apps that you might like. One is CaliperTool. The other is TapDrillTool. Just search for these on iTunes Store.