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Rif
03-30-2011, 12:05 AM
Hello,

Does anybody know where I could get a hollow mill without it being a special order? I need a hollow mill that has a 3/8" center hole.

Thanks,

Brian


Update: Never mind....I just checked e-bay. While I didn't remember seeing them on e-bay, I really never looked specifically for them.

PixMan
03-30-2011, 12:19 AM
Wish I knew what a hollow mill might be. Are you referring to an annual cutter? Got a photo, illustration of link to what one looks like? I'm curious.

Arthur.Marks
03-30-2011, 12:29 AM
PixMan,
Old, old, old type: http://www.brown-sharpe.com/102103.php
Typical HSS type: http://www.jtsmach.com/jtswebshop/MillingTools/M033.asp
New indexable type: http://www.sommatool.com/catalog/cutting.tools/hollowmill.asp

They're for turret lathe work. Rapid removal of stock.

PixMan
03-31-2011, 09:59 AM
I see now that the name is a misnomer as it's not really a milling tool but a turning tool. Not the kind of thing the average home shop machinist needs then is it? ;)

Toolguy
03-31-2011, 10:59 AM
They are often used to machine a boss or stud on a casting in a mill. It creates an exact size pin with a perpendicular base around it as quick and easy as drilling a hole.

Arthur.Marks
03-31-2011, 11:40 AM
Given Toolguy's use, are some of them able to be used in a rotating spindle (i.e. mill)? Or do they fly apart :cool:

Rif
03-31-2011, 11:56 AM
They are often used to machine a boss or stud on a casting in a mill. It creates an exact size pin with a perpendicular base around it as quick and easy as drilling a hole.


That is what I was looking into. I may have a job that will require that I make many off-center turnings of a 5/8" square brass rod. So, life will be good if I can use my milling machine to machine a boss on the end of the brass. Later I can use the boss to hold the whole thing in a 5c collet on my turret lathe.

I'll also need to use the hollow mill, on the turret lathe, to machine the other end of the brass bar. After those operations, I should have a 3/8" round bar with a big off-center square section in the middle.

Regards,

Brian

Arthur.Marks
03-31-2011, 12:09 PM
So did you end up with a Kutmore off of eBay? Thanks for widening my perspective on the use of these in the mill.

Rif
03-31-2011, 12:35 PM
So did you end up with a Kutmore off of eBay? Thanks for widening my perspective on the use of these in the mill.

Yes, I bought that set of Kutmore adjustable hollow mills. :D

I hope they do what I need.

Regards,

Brian

Toolguy
03-31-2011, 09:21 PM
Rif-
Why not use a 5/8 square collet with a stop and a vertical collet fixture in the mill? You could cut your bars to finish length to begin with, then simply do each end in the mill with a stop for the quill to come down against. That would go very quickly, especially with an air collet fixture. The cutting edges are held very securely and the hollow mill does not fly apart when rotating.

Rif
03-31-2011, 09:34 PM
Rif-
Why not use a 5/8 square collet with a stop and a vertical collet fixture in the mill? You could cut your bars to finish length to begin with, then simply do each end in the mill with a stop for the quill to come down against. That would go very quickly, especially with an air collet fixture. The cutting edges are held very securely and the hollow mill does not fly apart when rotating.


That would work nicely. There is only one problem. (Which I didn't mention and you wouldn't have known.) My biggest mill is a Hardinge TM horizontal. (My other mill is a Sherline 2000....let's not go there. :D )

Some day I would really like to get a mill, with a quill.

On the other hand, I do have two collet fixtures and would just have to get a square 5/8" 5c collet. (No air collet fixture; but, that would be cool.)

I'll certainly keep the 5c collet idea in mind. I was thinking about using a vice and a vice stop.

Best Regards,

Brian


I

Rich Carlstedt
03-31-2011, 09:41 PM
Rotabroach comes to mind

http://www.hougen.com/cutters/rotabroach_advantage.html

Rif
05-28-2011, 06:24 PM
Rif-
Why not use a 5/8 square collet with a stop and a vertical collet fixture in the mill? You could cut your bars to finish length to begin with, then simply do each end in the mill with a stop for the quill to come down against. That would go very quickly, especially with an air collet fixture. The cutting edges are held very securely and the hollow mill does not fly apart when rotating.

Hello,

I just wanted to add an update and thank you for this advice.

I was using a vise and, due to the small size of the brass at only about 1.125 long, I was scrapping a few pieces here and there as they wouldn't always stay in the vise properly. This was even after I tightened it up really tight.

So, I remembered your advice and tried it. Using a 5c collet fixture, with a 5/8" square collet, worked great. There was no more scrap. Even the hand cranking on the horizontal mill wasn't bad at all.

Here is a link to what I have been making: http://www.reprap.org/wiki/J_Head_Nozzle

Thanks!

Brian

jugs
05-28-2011, 07:54 PM
PixMan,
Old, old, old type: http://www.brown-sharpe.com/102103.php
Typical HSS type: http://www.jtsmach.com/jtswebshop/MillingTools/M033.asp
New indexable type: http://www.sommatool.com/catalog/cutting.tools/hollowmill.asp

They're for turret lathe work. Rapid removal of stock.


Hollow mills ???
We know them as tangential box tools.

A hollow mill is like a Rota-broach.

But a broach is a shaped hardened rod, pushed through a hole to make a shaped hole / keyway/ splines / internal gears .......

Then we have
Taps you can't hit or get water from, Right hand tools cutting on left & Left hand tools cutting on right, :eek:
No wonder no one knows what we're talking about (including us :confused: )

john
:)

DATo
05-28-2011, 08:33 PM
I'm not really sure I understand what you're trying to do but you might consider grinding a broken or dull end mill to the shape of a lathe parting tool making sure to have a square bottom and then using the boring head and offsetting it such that the inside sweep of the tool generates the diameter of the boss. The process is called "trepanning".

EDIT: Check this out http://www.youtube.com/watch?v=Rvk8RKFVXwA

You'd be doing this in the mill of course with only one cutting edge if you use the single point tool method described in my post.

Rif
05-28-2011, 10:41 PM
Hello,

What I am doing is using a hollow mill to create a 0.150 long boss that is 3/8" in diameter on a piece of brass. Then I use that boss to hold the brass in a 3/8" 5c collet on a lathe. On the lathe, I then turn down the other end to 3/8". Check out the picture about 1/4 the way down this page: http://www.reprap.org/wiki/J_Head_Nozzle

Basically, I am doing off-center turning and I am using this method as a fast way to setup the piece in the lathe as opposed to fiddling with a 4-jaw chuck. The end that I cut with the hollow mill eventually becomes the tip of an extrusion nozzle that is used in a 3d printer.

I checked out that machine you have a link to. I don't think I could fit it in my basement. :(

Regards,

Brian



I'm not really sure I understand what you're trying to do but you might consider grinding a broken or dull end mill to the shape of a lathe parting tool making sure to have a square bottom and then using the boring head and offsetting it such that the inside sweep of the tool generates the diameter of the boss. The process is called "trepanning".

EDIT: Check this out http://www.youtube.com/watch?v=Rvk8RKFVXwA

You'd be doing this in the mill of course with only one cutting edge if you use the single point tool method described in my post.

DATo
05-28-2011, 10:58 PM
OK Rif , I got ya. A picture is worth a thousand words *LOL* I thought you were only interested in creating something that would look like an o ring groove.

jkopel
05-29-2011, 02:16 AM
@Rif
Take a look at the last image in this thread on PM
http://www.practicalmachinist.com/vb/general/proper-use-pot-chuck-step-collet-192877/
Looks a LOT like what you are trying to accomplish.

Rif
05-29-2011, 09:23 AM
@Rif
Take a look at the last image in this thread on PM
http://www.practicalmachinist.com/vb/general/proper-use-pot-chuck-step-collet-192877/
Looks a LOT like what you are trying to accomplish.


Hello,

Thanks for posting that link. I bought a pot collet and tried to machine it out to do the 5/8" square brass off-center on the lathe. But, I wasn't very successful with the square hole. Making up a master collet and using inserts is a great idea and a money saver given the price of those collets.

Regards,

Brian

3t-
05-29-2011, 11:47 PM
I have one of these http://www.jtsmach.com/jtswebshop/MillingTools/M033.asp
that came in a box of lathe tooling and chucks. I have it set aside to use in my turret lathe.

Can this also be used in a Bridgeport type mill in place of a standard boring head to machine a boss?

J. R. Williams
05-30-2011, 12:16 AM
Try (Geneseemfg.com) as they make a line of adjustable hollow mills. I have a set of four and have the smaller one loaned out. The cutter blades are carbide tipped and reasonable in price. The set just finished a 3K part run in brass. They save several operations and were used on a small Hardinge CNC.
JRW

Rif
05-30-2011, 01:19 AM
Hello,

Yes, it can. I am using an almost identical one to machine a boss. It works a lot faster than a boring head would.

Regards,

Brian



I have one of these http://www.jtsmach.com/jtswebshop/MillingTools/M033.asp
that came in a box of lathe tooling and chucks. I have it set aside to use in my turret lathe.

Can this also be used in a Bridgeport type mill in place of a standard boring head to machine a boss?

jugs
05-30-2011, 02:45 AM
I have one of these http://www.jtsmach.com/jtswebshop/MillingTools/M033.asp
that came in a box of lathe tooling and chucks. I have it set aside to use in my turret lathe.

Can this also be used in a Bridgeport type mill in place of a standard boring head to machine a boss?

Yes ... but make sure everything is locked down tight before you start cutting, or things could start flying about :eek: , once the cut is on, it's self centering. :D

john
:)

3t-
05-31-2011, 12:25 AM
Thanks, I appreciate the info.