Boring / Grooving / Threading.

[benmychree]

I did not post any pictures of a lathe, and where did the discussion of boring sprockets come from? As to boring sprockets, one must, of course line up to the pitch diameter of the teeth, which should be the same and concentric with the OD of the teeth; many times this is not so easy with, especially a plate type sprocket with no hub; if it has a hup, the hub is likely concentric with the PD and OD of the sprocket, and likely if the sprocket has an existing bore, it can be used to indicate in the sprocket in the lathe chuck. Chucking the OD of a sprocket can be problematic, such as with a plate sprocket with no hub, but this can be accomplished by making a "pot chuck", a ring that has a shoulder in the ID and fits closely on the sprocket OD and is machined concentric in the chuck it is to be held in; after machining it, it is split with a saw cut on one side and acts as a collet to chuck a sprocket without damaging the teeth.

 

[Big Bore Builder]

OOps. don't know what happened here.

Ben,

What brand lathe is that and how do you set up a sprocket, so the center hole runs true to the o.d. of the teeth?

Real simple.

When sprockets are manufactured the center hole, or pilot hole, is the main index for the tooth milling.

Simply put, the blank, with center hole (called pilot bore by machinists} fits over the arbor in the milling fixture that the teeth are milled in.

So the teeth and pitch diameter are true to the pilot bore.

When machining a sprocket to a larger bore, as shown in my photo, the pilot bore and the face of the sprocket are indicated true to the lathe.

Now the pitch diameter is true to the lathe centerline.

Look close and you can see copper strips between the jaws and the sprocket teeth.

Machine away!

The lathe is a 14x40 Jet Gear Head that I purchased new in 1981. It has been a good machine, I have many thousands of hours on it.

 

[Chipper5783]

As to boring bars, my all time favorite when it comes to HSS is the line of Bokum tools, with solid (integral) shanks and the screw on types; they are made in lead, flat bottom, threading, chamfering and grooving styles from tiny to BIG, they are form relieved and all are sharpened by grinding ONLY the top surface of the tool.

Where can you get Bokum tooling? Are Ifanger and Hufnagel interchangeable with Bokum?