Half-Bull Nose?

[The_Apprentice]

I was experimenting with a project, and need a way to keep things on center for chamfering the edges (and other things).

So it would seem what would help me for chamfering the ends on the outside at least, would be a LIVE BULL NOSE.

The problem, is what if I want to chamfer the inside? I tried to look for a HALF-BULL NOSE. Unfortunately, these seem to be extremely rare? I am looking for one for a 2MT. Perhaps I have no choice but to make one, but maybe I'm missing a good reason these are hard to find. A simple solution that is not so obvious to my rookie mind.

Here is an example of what I'm working with... and why a bull-nose makes sense...

 

[benmychree]

I would do the chamfering in a steady rest if the part looked like it could get loose in the chuck, especially if it is lightly chucked to avoid distortion

 

[Bi11Hudson]

The first point would be; Is the end cut square?

To true the end properly, you would need to use a steady rest. You need one even if you use a cut-off tool. A cutoff tool should only be used near to the chuck, or steady. And never with a tailstock center. The cutoff end must be free to fall.(wobble, whatever) A facing cut would be the simplest. But for that, again, you would need the steady.

Most times I would cut with a chop saw and use a pipe reamer. But that wouldn't give a truely square end. Useable for what I do, but not truely square. A steady rest is the only practical solution.

And to use the bullnose it must be deburred first. Otherwise, it won't run true. I have heard of a half bullnose, but long ago and on a much larger machine than I have. For grease (lubrication). Which comes back to it must be deburred.

 

[The_Apprentice]

I will double-check the capacity of my steady-rest. I only used it once before-- for my on-going mandrel project. But I don't think it can support the diameter of this workpiece. So there is one of the problems I had. But I believe I understand what you mean, if you can't make sure you are facing a workpiece well to begin with, it is not going to sit with the bull nose proper either.

I have a few other things I will experiment with later on today in my poor-man's shop, (lol). Will be back with the details.

Furthermore, I think I will put in an order for a Live Bull Nose Center on Amazon soon. For a 2MT, $45 seem like a decent price? Yes, I know it's not a simple question as they can go for up to $300, which a lot is dependent on quality...

Once I get a mini-mill, I will definitely look more into machining my own tools. The half-bull nose will probably be one of them.

 

[Beerfan]

Square tool, chamfer inside and outside at 45 Deg.

If the job requires other then 45 Deg. grind a tool or use the compound at the angle needed.

This is what the compound is for, if indeed you need to make a large number of parts this way turn turn the compound with the handle facing the operator, it is much easier to use this way. Run the spindle in reverse and use a left handed tool in negative X.

 

[magicniner]

Bore all your parts first then use an expanding mandrel to give full support whilst machining the outside and ends.
Expanding mandrels are quick and easy to make.

 

[rwm]

I have a bull nose center but what is a half bull nose?
Robert

 

[magicniner]

What is a half bull nose?
Robert

A pointless exercise as it will damage the work and in this instance the supported work is to be machined away, you could use a custom internal or external roller guide to support the work if you wanted a more expensive and complex solution to a mandrel ;-)

 

[The_Apprentice]

This is what the compound is for

When I chamfer, I just turn the 4WTP 45 Deg and do it that way. Much quicker and I have seen a lot of machinists doing the same.

The compound, I will save for when doing a specific 60 Deg angle or something like interesting tapers.

 

[The_Apprentice]

Expanding mandrels are quick and easy to make.

I have taken a look at expanding mandrels for a few months now. And was planning to make a few out of cheap aluminum. I also looked at some prices of pre-made ones, and saw prices of $200 + shipping & taxes.

Hence, the desire to just make my own...