Advice on toolholders

[m_c]

OK thanks, I'll look into boring it out. Out of interest though, and please excuse my ignorance, why would it be worse than a screw on lathe chuck for getting stuck?

Big lathes, the tapers never turn against each other. They're secured using either bolts, or a retaining nut.

The only small lathes I've seen with screw on chucks, use locating registers, not tapers.

Once a taper locks, you need to physically force them apart. They generally will not spin against each other, especially if you still have pressure holding them together.

By all means try it, however I wouldn't be surprised if they seize together, and you have to machine the holder back out.

[lucan07]

If the key locates after insertion it should not overtighten locking the mechanism beyond the point you leave it, I pesume it has been designed to act in this manner, presumable the chuck operated the taper when working and threads etc would have been worked to locate and lock if a professional design

[m_c]

Lucan, no offence, but your suggestion won't work.
Tapers rely on being firmly held together. With your suggestion, you would either have to ensure the tapers never fully tightened, meaning the toolholder will be loose and rattle in the spindle, or risk never being able to get the key in.

[lucan07]

If the key is sprung it would be designed to act at a point to stop overtightening as well as aligning the thread to start at a specific it would only engage at a point beyond just beyond correct torque when milling, presumably you release it to with the chuck to undo otherwise it would engage and lock once on each rotation.

[Rabs]

If the key is sprung it would be designed to act at a point to stop overtightening as well as aligning the thread to start at a specific it would only engage at a point beyond just beyond correct torque when milling, presumably you release it to with the chuck to undo otherwise it would engage and lock once on each rotation.

I think m_c's point is that the toolholder can't be tight against the key and the taper at the same time - it has to hit one of them first. If you want that to the key to stop over tightening, then itwon't be tight on the taper. If it isn't tight on the taper then the tool will wobble. Thanks for taking the time to help though - there might well be something there related to keyways. I'll give it some thought.

Big lathes, the tapers never turn against each other. They're secured using either bolts, or a retaining nut.

The only small lathes I've seen with screw on chucks, use locating registers, not tapers.

Ok, that makes sense. I suppose the smaller angle the taper the more prone it will be to locking because the larger the radial force is for a given axial bolt tension. That also explains why a lathe chuck with a flat register (which I suppose can be considered as a 180 degree 'taper') is much less prone to locking.

If it makes any difference this is a small machine with a 1/2hp spindle motor.

[John S]

Questions,
In Fig 2 what is the diameter to the thing spindle part, the bit that holds the pulley.
What is the biggest tool you would be satisfied using ? Be reasonable here.

Any pictures as opposed to blocky diagrams.

[Rabs]

Questions,
In Fig 2 what is the diameter to the thing spindle part, the bit that holds the pulley.
What is the biggest tool you would be satisfied using ? Be reasonable here.

Any pictures as opposed to blocky diagrams.

Here you go. The spindle block is enclosed, with all bearings and pulleys concealed. At the top there is only an 18mm diameter shaft protruding. Ignore the bit of aluminium extrusion, it's just a temporary mount for a spindle speed sensor.


At the nose the spindle is 40mm in diameter


Here is the easychange chuck. To secure it you push a bolt from below, through the hole in the narrow end of the chuck and into a thread on the spindle. (see original post)


Here is one of the easychange toolholders:


And here's what the setup looks like as I received it:


Here is a tooholder I've knocked up with a stud at the top and how it looks screwed directly into the spindle. I've not used this yet on the back of m_c's warning.

I've made it with drive slots to fit the easychgange chuck but these could also be used for a spanner to release it from the spindle, with a normal spanner used on the flats at the top of the spindle.