best material for making a quill

[MattiJ]

This does have a lock with a slit. I've tried snugging the slop out of it but noticed the tighter it's snugged, the sooner it stops retracting on its own which tells me the quill has a taper on it. Another reason for a new quill.

I wouldn’t yet jump to conclusion about tapered quill. Could be also number of other things so better measure it.

[nickel-city-fab]

And if it's egged out bad, well guess I'll then be asking how to get it honed out straight and round.

I would make an aluminum or brass lap that is about 2x as long as the bore. Unless you have access to something like a Sunnen sizing hone (automotive shop...) if the lap is longer than the bore then you can avoid bell-mouthing.

[Doozer]

... It is for a small bench mill with a little over 3" of quill travel. ....

Just doing a reality check here, but....
This is going to be more work
than you mill is probably worth.
Just saying. It's either for love
or money, and this one sure ain't
for the money. Ask yourself, do
you love this mill that much ?

-D

[Barefoot]

Just doing a reality check here, but....
This is going to be more work
than you mill is probably worth.
Just saying. It's either for love
or money, and this one sure ain't
for the money. Ask yourself, do
you love this mill that much ?

-D

Definitely not love...more of a necessity thing due to lack of space for the machine I want.

[Barefoot]

I would make an aluminum or brass lap that is about 2x as long as the bore. Unless you have access to something like a Sunnen sizing hone (automotive shop...) if the lap is longer than the bore then you can avoid bell-mouthing.

Please elaborate. I've made crude laps out of wood dowels and strips of 320, but nothing on this scale. Would a lapping compound be used with this?

[nickel-city-fab]

Please elaborate. I've made crude laps out of wood dowels and strips of 320, but nothing on this scale. Would a lapping compound be used with this?

Yes, a compound or slurry -- the grit is easy to embed into softer metals, which is the idea.

[Barefoot]

Yes, a compound or slurry -- the grit is easy to embed into softer metals, which is the idea.

Ahh, it's embedded.... well that makes sense.

Now how is diameter of the lap determined for an egged bore?

[JHartley]

I think that for this to come out an improvement, you will need to become familiar with both internal and external lapping. The suggestion of a internal lap 2x the length of the quill is a good start. Remember, there are, at least, 2 kinds of lapping - 1) where you embed (charge) the abrasive into the lap and 2) where you use non-embedding free abrasive. To my limited knowledge, either will get the job done. Internal laps usually have a mechanism to expand as the lapping proceeds. See: https://www.helicallap.com

Similarly, external laps are shorter than the work and also need a mechanism to shrink as the lapping proceeds.

This is going to be tedious precision fiddly work. Your skill and patience are going to determine the quality of the result. Good luck.

[old mart]

The head of the mill could be set up in a large lathe for a clean up of the bore before making the new quill.

[nickel-city-fab]

Ahh, it's embedded.... well that makes sense.

Now how is diameter of the lap determined for an egged bore?

You could make the diameter whatever you want, to suit the new quill... presumably this will be slightly greater than the egged bore.

[nickel-city-fab]

I don't lap things very often, but when I do it needs to be right. I spread my abrasive out on a piece of plate glass, and shove the lap down into that as hard as I can, with my entire weight. This forces the grit into the aluminum or brass. I usually lap with kerosene or a very light oil. I have done hydraulic parts in this way with good luck.

[oxford]

OP, what’s the make and model of the mill you have so we can get a better idea of what your working with.

[Galaxie]

A lap 2X the length of the quill sounds unwieldy even for a mini mill. Wouldn't 2X-3X the diameter be sufficient?

I successfully did a 2.06" bore with a lap ~1.5X the diameter, but I had to be very careful. I used a Duplex-style lap (see figure 16): http://www.modelenginenews.org/duplex/duplex_laps.html

[darryl]

I'm wondering what kind of setup you'd be using to ensure the bore is aligned. I presume it would be set up on the carriage and fly cut using a boring bar held between centers. At least I think that's what I'd do to get the bore straight and remove bell-mouthing. Not sure that lapping would be the right operation here-

[Bented]

The question may not be suitable material but material condition when the part is finished.