Register

[mickri]

We throw the terms "register,""registered" and "registering"around and I think that I understand what it means.

Right now I am making an adapter to mate a 4 jaw chuck I recently bought to fit the spindle on my lathe. The threads are slightly loose. I have a very, very tight fit on "A" in the picture below. So tight the that adapter really doesn't want to go up against "B" in the picture.



Would this mean that the adapter is registered on "A?" Should the adapter register on "A" and "B?" Or just on "B" with a slightly loose fit on "A?"

And how do we know when something is registered? I don't want to go any further with this project until I get this figured out.

I am probably using incorrect terminology here.

 

[darkzero]

A is what I call a register or a boss. B is what I would call the mating face that the backplate would seat against when tightened. Others may call them differently but whatever the names they serve the same purposes

The register is what provides most of the repeatability for accuracy. So your backplate should have a fit as close as possible with A without binding. This is what the backplate is registering on so having slightly loose threads won't matter. The backplate should also be square with the bore for register on the adapter so that it seats against B flat.

 

[DavidR8]

Good question!
On the backplate I just made there was clearance between A and the backplate bore but it ran right tight against 'B'

 

[darkzero]

My lathe has a cam lock spindle but here's an example that I made just last week for a couple of micro 3-jaw chucks, same concept.

 

[BtoVin83]

Typically threads are considered non-self centering so you need something to make it run concentric, the register "A". The face "B" keeps the face running true so now the chuck is concentric and face running true.

 

[mickri]

I am glad that I asked this question. I had always thought that having a good fit against face "B" was most important and that was the register.

I made my adapter like in Darkzero's first picture. Chucked my piece of mystery steel bar in the 3 jaw and faced off the end. Then bored and threaded the hole to fit the threads on the spindle. Now I am at the stage where I am enlarging the hole to fit on surface "A." I think that I am too tight on "A" and will take another thousand off.

Thanks for clearing this up for me.