I ‘ve wanted to make a set of center drill holders for a long time. No matter what project I was working on, it always seemed like I spent half of my time with a chuck key in my hand swapping out center drills with drill bits. However, the thought of cutting a Morse taper (with no taper attachment) had always seemed daunting. After all, how in the world was I going to accurately cut a taper at 1° 26′ 16″? One degree 26 feet and 16 inches? What? … Just kidding.
Then it occurred to me that I could use my compound to cut a Morse taper since it has plenty of travel. I needed about 4″ of travel to cut a number 3 Morse taper (also known as a MT3, MT#3, or a 3MT). Excited, I set to work.
Here is an image of all the dimensions of a Morse taper (click the image to go to the Wikipedia article on Morse tapers). But you don’t have to calculate a single dimension if you follow my process for creating a Morse taper – it is very simple.
I set things up using a MT3 drill chuck arbor positioned between centers (the center in the 3-jaw chuck is a sacrificial center that I re-cut at 60° to ensure that it was perfectly centered). I didn’t have an extra arbor sitting around, so I removed the arbor from my lathe’s drill chuck and used that.
Using a dial indicator (attached to the compound with a mag base) I adjusted my compound to about 1.5° and began sweeping the indicator from one end to the other, making adjustments as needed until the indicator read zero across the entire length of the taper.
The Picture below is my attempt at a double-exposure to illustrate the process of sweeping back and fourth along the taper.
Make sure that the point of you dial indicator is on the centerline of the part, if it’s high or low you’re taper won’t come out right! Frank Ford built a special dial indicator holder that helps ensure that his indicator is reading exactly from the centerline of a taper. Franks special indicator holder can be found here. If you plan on making a lot of tapers, Franks tool would definately speed up the process and help make it more precise.
Here’s what 1° 26′ 16″ (one degree 26 minutes and 16 seconds) looks like on my compound – pretty precise … right? Which is exactly why it would be impossible to set up this angle using only the graduations on the compound – they’re not nearly precise enough.
Once you’re satisfied that your compound is set at the correct angle you’re ready to start cutting your taper. It’s a good idea to have a way to check the size of your taper occasionally. I used a Morse taper sleeve (4/3) for this purpose. Keep test fitting until the taper fits into the sleeve to the right depth. Be sure it fits far enough into the sleeve so that it can be knocked out with a drift, but not so far in that it bottoms out.
Here’s an image to illustrate how to use a sleeve to check your taper for proper fit. The taper on the top is still too large and doesn’t penetrate the sleeve far enough to be knocked out with a drift. The taper on the bottom has enough of the taper exposed to be knocked out by using a drift in the slot.
Here’s what I mean by using a drift to separate a taper from a sleeve. Get my drift? …
Once you’re satisfied with the size of the taper and the depth of the fit, you can fine tune the angle using layout die (or a Sharpie) and emery cloth. To test the fit draw a line along the taper and slide the sleeve over the taper giving it a few full rotations. The ink will be removed wherever the two tapers make contact.
Here you can see that my taper rubs in the middle more than at the ends, but it’s making contact along about 2 inches of the taper. With a little fine tuning (polishing with fine grit emery cloth reinforced with a flat backing) I should be able to improve the level of contact even further.
You’ll notice that my taper doesn’t have a tang. This is because my tailstock doesn’t have a slot in it so tangs are useless for my lathe – they just get in the way. Feel free to put a tang on your taper if you like.
However, if you decide to forgo the tang, be sure to turn down the first 0.300 so that you’ll have a protective “button” (for lack of a better term) at the end of the taper. This button is intended to absorb any abuse the arbor might experience over it’s lifetime (from being dropped or deformed by a drift). If the taper were to extend all the way to the end, any damage would cause the taper to not seat properly in the tailstock. Here is a picture of a manufactured live center with a black (hardened) protective button on the end.
I decided to cut several blank tapers while I had the angle set up. I’d advise you do the same. You can always think of uses for the tapers later! The long one on the left will be used to make a die holder. The third one from the left will probably become a slitting saw arbor. And the 3 on the right became the center drill holders shown at the very beginning of this article.
This was my first time cutting my own Morse taper, so If I missed anything please leave a comment. I’m sure there are several other methods of accurately cutting a Morse taper, so if you have one, please share your experience!
Update: There have been several comments on this project posted on the Machinist Workshop Forum. Feel free to visit the forum for more information and insight from others.
Update #2: Here’s a picture of the completed Steve Bedair style Die Holder.
It’s actually pretty similar in design to one that you can buy from LittleMachineShop.com. However, the LMS die holder fits smaller dies (13/16 and 1 inch). I made mine so that one end can hold a 1″ die and the other end can hold a 1.5″ die.
Also, the shaft is slightly longer than the sleeve, so you can pop the dies out easily when the set screws are loosened. Here’s a pic of the 1.5″ die being pushed out.
I’ve been thinking about trying my hand at CAD and drawing up a set of plans for the die holder with the dimensions I used. I haven’t seen plans for one anywhere else. If anyone is interested please leave a comment. If there is enough interest I’ll draw them up.