I’m new to the machining shop and recently took the manual mill class. I’m interested in tapping some M3 and M5 screw holes in aluminum as practice for a project I’m working on. Any tips for doing this with the tools available at asmbly? Due to time restrictions, this wasn’t covered in the milling class.
I did some research online and found the following resources that use the drill press with tap and tapping handle:
We have a good quality set of taps in the machine shop from Gear Wrench. The use of a drill press to help align the tap is helpful until you get the full threads started. The 1st 7 threads or so on the typical tap is made to help start the tap. Once you are past that, you generally won’t need the drill press to keep the tap straight.
-I would use tapcon or some kind of tapping fluid.
-I would go slower and back off when you feel resistance. Especially with the M3. The straight flute taps need you to go slower so the chips can go down and up into the flutes. If you are doing more of production style. I would look at spiral flute taps. The upcut helix forces the chips upward.
-If you plan on tapping a lot metric holes. I would suggest getting metric drill bits. If you want to tap a m3 hole. You drill with 2mm drill bit.
All useful tips from Joe. I’ll add, we do have a set of metric drill bits in the metal shop. Typically metric taps are easy since your tap drill is just the thread major diameter minus the pitch.
We have some tap magic in the metal shop cabinet you’re welcome to use.
There are charts on the machine shop cabinet that tell you what size drill to use with each tap size (though it’s generally simple for metric), and we have all common drill sizes (fractional, numbered, lettered, metric). The oil in the lubricant cups in the metal shop is the same Tap Magic as in the cabinet.
The main trick that doesn’t seem well known is using a spring loaded tap guide:
We have several in the taps drawer. Once you know how to use a tap guide, you will never willingly manually tap a hole without one. Several people can show you how, but basically, you drill your tap hole on the mill, then put the tap guide in the chuck. It has a spring loaded pin that you put in the hole in the top of your tap handle. That will keep your tap aligned and prevent you from applying a torque that will break the tap. Taps that small are extremely fragile; this will save many.
Several people can show you how, but basically, you drill your tap hole on the mill, then put the tap guide in the chuck. It has a spring loaded pin that you put in the hole in the top of your tap handle. That will keep your tap aligned and prevent you from applying a torque that will break the tap.
Just to make sure I’m understanding right, you’re suggesting using the manual mill in a setup similar to the following:
Typically metric taps are easy since your tap drill is just the thread major diameter minus the pitch.
Okay, interesting! The pitch is the distance between the threads and for metric this also is the difference between the major and minor diameters of the screw?
Yeah pretty much. The reason people normally say thread diameter minus pitch is because it’s usually listed right on the fastener. So for your M5x0.8 standard pitch fastener, you’d use a 4.2mm drill.
