Subject: Re: Using Fly cutters

From: [email-masked] (John Barnwell)
Date: 8 Feb 1995 04:07:52 GMT

The problem with shell milling cutters is cost of tool
remember rec.crafts.metalworking shell mill can eaisly run over
a hundred bucks and 25 to 30 bucks to sharpen. All it takes is 
about 2 seconds of the wrong feed/speed to watch a $100 shell mill
become a $100 piece of Highspeed steel junk

A fly cutter with a HS tool can be sharpened at home many times perhaps
a 100 or more ( I have yet to sharpened away a piece of HS steel )
and a carbide cutter for the same fly cutter will go you about $2.50. 
carbide insert shell mills are in fact multi point fly cutters.

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From: [email-masked] (Mike Rehmus)
Date: 8 Feb 1995 07:36:35 GMT

In <[email-masked]> [email-masked] (John Barnwell) 

>carbide insert shell mills are in fact multi point fly cutters.

I'd like to sell you cutting tools, John.  A Niagra mill in 2-1/4 only 
costs $56 at the most expensive supply store in San Jose.  A good Bison 
R-8 adaptor was, I believe, $40.  BTW, I buy Bison mills for $26 at 
ENCO.

No matter what you say, the problem with a fly cutter is still going to 
be shock loads to bearing in machine tools that cost thousands of 
dollars.  The cost of a good cutter does not even come close!

Mike

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From: [email-masked] (Alden Hackmann)
Date: 8 Feb 1995 20:15:20 GMT

[email-masked] (Mike Rehmus) writes:

>[email-masked] (John Barnwell) writes: 

>dollars.  The cost of a good cutter does not even come close!

I will confess ignorance here (at the risk of starting some sort of flame 
war, probably) and ask - what is a shell mill?  I presently use a fly 
cutter set to a 2.00 diameter for cutting a shallow dished channel in 15" 
long pieces of wood.  If there's a better way, I'd like to know.  What 
are the advantages and applications of a shell mill?

Alden and Cali Hackmann
Olympic Instruments - makers of fine hurdy-gurdies
PO Box 166, Indianola WA 98342
360-297-7234 (that's right, 360)
[email-masked]

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From: [email-masked] (Doug White)
Date: 9 Feb 1995 02:30:22 GMT

In <[email-masked]> [email-masked] (Mike 
Rehmus) writes: 

>
>No flames, John and I are having a good time and probably learning 
>something in the process.
>
>
>A shell mill is essentially a milling cutter with a hole where the 
>shank would normally be found.  The cutter is mounted on an arbor and 
>a bolt/screw tightened to hold it on.  The driving forces are taken 
>by a pair of driving keys that fit into the backside of the cutter.
>
>The advantage is that you buy the arbor once and then only replace the 
>cutting portion.  You save $ by not having to buy a shank made of HSS 
>steel everytime.  
>
>This only works for large cutters.  The smallest that ENCO carries, for 
>example, is 1 1-4".  It has 8 flutes and costs $14.93  a 2-1/4 costs 
>$23.95 and has 10 flutes.  The arbor for the smaller shell mill costs  
>$21.95 and for the larger, $24.79.
>
>Where John's argument is somewhat more cogent is when one gets into the 
>much larger sizes.  A 6" is $215.
>
>A fly-cutter is not a bad tool for taking a finishing cut.  It just 
>cannot hog out much metal (or wood) at one pass.  I can literally 
remove 
>cubic inches of metal a minute if I want to apply coolant and listen to 
>the Bridgeport grunt a bit.
>
>BTW, the shell end mills cut along their sides too.  The 1-1/4 has a 1 
>height, the 2-1/4 has a 1-1/2 in cutting height.
>
>Another nice thing is that the bigger ones turn slow and don't throw 
>metal all over the shop so I reach for the 2-1/4 whenever I can.
>
>Best,
>
>Mike
>
>PS, you can also get indexing shells for using carbide.
>
>
I don't think using a fly-cutter on soft material is a problem.  I use 
one with about a 2 1/2" sweep on PVC plastic all the time with a .020 
deep cut.  I have a small Clausing vertical mill, which uses #2 MT 
collets and the largest shank it can handle is 1/2".  The biggest shell 
end mill I can find that fits a half inch shank is only 1 1/4" in 
diameter.  Hardly worth the trouble.

Doug White

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From: [email-masked] (Mike Rehmus)
Date: 9 Feb 1995 07:24:38 GMT

>diameter.  Hardly worth the trouble.

Doug,

The arbors are easy to make.  You could make one for any size 
you feel confident your mill can swing.

If I were cutting plastic, the fly-cutter would be a good 
choice, I think.

Best,

Mike

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From: [email-masked] (Tim Kirby)
Date: 9 Feb 95 16:54:20 CST

Alden  Hackmann ([email-masked]) wrote:
: I will confess ignorance here (at the risk of starting some sort of flame 
: war, probably) and ask - what is a shell mill?  I presently use a fly 
: cutter set to a 2.00 diameter for cutting a shallow dished channel in 15" 
: long pieces of wood.  If there's a better way, I'd like to know.  What 
: are the advantages and applications of a shell mill?

Well, the easiest description would be
        "it looks like an end mill but much bigger"

I assume the "shell" is because they are not usually solid, being an inverted
cup shape.
           (anyone have a better explanation?) 

Advantages? more cutting faces, better rigidity, probably a better finish
(I say probably because that sort of thing is so dependant on the operator)

Tim
--
Tim Kirby                    - [email-masked] -                +1-(612)-683-5390
Software Division System Support ________________ Cray Research, Eagan MN, USA
----------------- Ask not for whom I speak - I speak for me ------------------
If you are sure you understand everything that is going on,
you are hopelessly confused...                                - Walter Mondale

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From: [email-masked] (Mike Rehmus)
Date: 10 Feb 1995 04:37:30 GMT

In <[email-masked]> [email-masked] (Tim Kirby) 

>(I say probably because that sort of thing is so dependant on the 
operator)

Shell because they have a hole in the ---back--- to accomodate the 
arbor.

mike

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From: [email-masked]
Date: Fri, 10 Feb 1995 22:46:01 GMT

There is a good picture of a shell mill in operation on page 18 of the 
Feb 95 issue of Projects in metal.  For putting shallow dished channels
in wood, I use a table saw with the blad set at the depth of channel
desired, and then feed the board across it on the diagonal to control
the width.  This is no good of course, if the precise radius is critical.
If you do much woodworking you already know this of course, but on the
chance you missed it...

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From: [email-masked] (Mike Rehmus)
Date: 9 Feb 1995 01:46:08 GMT

A fly-cutter is not a bad tool for taking a finishing cut.  It just 
cannot hog out much metal (or wood) at one pass.  I can literally remove 
cubic inches of metal a minute if I want to apply coolant and listen to 
the Bridgeport grunt a bit.

Best,

Mike

From Bruce Taylor Tue Feb 14 00:06:24 EST 1995
Article: 9600 of rec.crafts.metalworking
Path: bigblue.oit.unc.edu!concert!news-server.ncren.net!news.duke.edu!godot.cc.duq.edu!newsfeed.pitt.edu!gatech!howland.reston.ans.net!math.ohio-state.edu!caen!crl.dec.com!crl.dec.com!nntpd.lkg.dec.com!tpwosf.tay1.dec.com!taylor
From: [email-masked] (Bruce Taylor)
Newsgroups: rec.crafts.metalworking
Subject: roll pin advise...
Date: 8 Feb 1995 14:04:05 GMT
Organization: Digital Equipment Corporation
Lines: 18
Distribution: world
Message-ID: <[email-masked]>
Reply-To: Bruce Taylor
NNTP-Posting-Host: tpwosf.tay1.dec.com

Folks -

I'm in the process of repairing an old drill press, and I need to take the
spider handle off the quill feed shaft. It's attached with a roll pin
driven flush with the surface of the handle hub. Now normally, roll pins
are no problem - you just drive them through with a drift punch; but on
this hub I can't find the exit hole for the pin! It could be that the
pin only goes through one wall of the hub and the [possibly hollow] shaft
and I can drive it through as usual. However, if I'm wrong, then I'm left
with a pin bottomed out in a blind hole - yuk.

So what should I do? Should I go ahead and try driving it out, figuring that
*everyone* uses a through hole for these things, or try to figure some way
of grabbing it and pulling it out? Anyone have any ideas for how to do the
latter?

				- bruce

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From: [email-masked] (murr rhame)
Date: 9 Feb 1995 19:33:07 -0500

>are the advantages and applications of a shell mill?

A shell mill is a multi pointed mill cutter with replaceable insert teeth. 
I have worked with tools having as few as 2 inserts on a .5" body and as
many as 28 inserts on a 6.3" body.  The simpler tools use a screw though a
hole in the insert for attachment.  Some of the larger mills have
adjustments each for tooth using a jack screw and clamp system.  IMHO, the
easiest ones to use out have a spring loaded clamping system made by
Sandvik.  

A shell mill will outperform a fly cutter in most applications regarding
the rate of material removal.  For home shop applications cubic inches per
minute is not usually a big issue.  It is impressive to watch and hear a
6.3" mill explode cast iron chips from a 6" wide by .250" cut at a couple
hundred inches per minute feed...  Most of us don't have 50 horse peak T50
spindles in our back yard shops. 

All of the shell mill units I've worked with were for metal cutting.  Some
of the high positive rake designs might work well in wood.  Most of these
tools have seed limits in the low thousands of RPM.  This may restrict
their use when it comes to making sawdust. 

Also IMHO, the shock issue on fly cutters is being a bit overplayed.  If
the chip load is light compared to to mass of the cutter the machine does
not see much shock.  The inertia of the cutting head carries the cutter
though on most cuts.  The heavier the cutter head the better.  You can't
take a very high horse power fly cut without loosing the finish anyway. 
I've swung fly a cutter over 8" in radius (over 16" dia.) on a Bridgeport. 
This had a massive 416 stainless head ~6" diameter and used a hand braised
carbide tip to form cut a pot metal casting.  It had to be this large to
reach over an obstruction.  The head was tilted to 45 degrees.  Not
something I would recommend doing everyday but it worked. 

-- 
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