I put an motor-driven feed on my lathe
(http://www.MWDropbox.com/dropbox/ServoPowerFeed.pdf) which I built to
give a minimum feed of .003. I don't know why I chose that value - it's
probably the smallest that the change box will do.

I was just watching a Tubal Cain video on YouTube about the power feed
he put on an Atlas lathe. The Atlas gears only went down to .0046
(IIRC) and he wanted much finer. (His other lathes went to .0016 & .00076.)

My first thought was to modify my feed to go much finer/slower. But I
got to thinking that there must be some limit. It seems that if the
feed was too fine the bit would just rub until enough feed had
accumulated and then the bit would bite and jump. And the bit's edge
would be critical - razor sharp or better.

How fine do you feed? What are the considerations in doing a very fine
feed?

Thanks,
Bob

Bob Engelhardt fired this volley in
:

How fine do you feed? What are the considerations in doing a very fine
feed?


You can feed as fine as you wish. A lot of industrial precision cutters
take off mere microns per pass.

Your concern about "skating, then hogging" is only a legitimate concern
with positive-rake, fairly dull tooling.

Do the same with a zero or negative rake tool _that_is_sharp_enough_, and
you can take a 0.0001 cut (or a 0.000001 cut), if you wish.

Basically, if the cutter edge has a radius of a small fraction of the
feed distance, and has a small enough rake to NOT pull itself into the
work, it will do just fine.

If you're using HSS tooling, I'd keep the feed above 1.5 thousandths.

Lloyd

Lloyd E. Sponenburgh wrote:
Bob Engelhardt fired this volley in
:

How fine do you feed? What are the considerations in doing a very
fine feed?


You can feed as fine as you wish. A lot of industrial precision
cutters take off mere microns per pass.

Your concern about "skating, then hogging" is only a legitimate
concern with positive-rake, fairly dull tooling.

Do the same with a zero or negative rake tool _that_is_sharp_enough_,
and you can take a 0.0001 cut (or a 0.000001 cut), if you wish.

Basically, if the cutter edge has a radius of a small fraction of the
feed distance, and has a small enough rake to NOT pull itself into the
work, it will do just fine.

If you're using HSS tooling, I'd keep the feed above 1.5 thousandths.

Lloyd

My Logan is geared right now so that it feeds .0022 on the finest feed .
Stock setup feeds .0044 , but sometimes that isn't fine enough . Lloyd ,
re-read your statement about feed rate vs tool radius . I find I get the
best finish if the tip radius is larger than the feed rate ...
--
Snag



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On Sun, 15 Dec 2013 19:39:18 -0500, Bob Engelhardt
wrote:

I put an motor-driven feed on my lathe
(http://www.MWDropbox.com/dropbox/ServoPowerFeed.pdf) which I built to
give a minimum feed of .003. I don't know why I chose that value - it's
probably the smallest that the change box will do.

I was just watching a Tubal Cain video on YouTube about the power feed
he put on an Atlas lathe. The Atlas gears only went down to .0046
(IIRC) and he wanted much finer. (His other lathes went to .0016 & .00076.)

My first thought was to modify my feed to go much finer/slower. But I
got to thinking that there must be some limit. It seems that if the
feed was too fine the bit would just rub until enough feed had
accumulated and then the bit would bite and jump. And the bit's edge
would be critical - razor sharp or better.

How fine do you feed? What are the considerations in doing a very fine
feed?

Thanks,
Bob

It largely depends on what your tool nose radius is.

This may be of some assistance


http://www.custompartnet.com/calcula...face-roughness

Google "tool nose radius surface finish"

75,000 hits

Many/most of my clients use .007-.009 feed rates at speeds up to 4000
rpm. In fact..its largely the "standard" feed rate for roughing and
even finishing. And it really..really depends on the tool nose radius.

Use a sharp, pointed tool..and finish is gonna suck..really suck.
Increase the "roundness" of the tip of the tool..and it gets better
and better. Many of my clients standardize on .016 tool nose radius
for most operations from roughing to finish. Some go to .030 for
finish.

If your lathe is worn badly and is loose..then doing all your cutting
with a very round tool nose is indicated.

Gunner

--
"Owning a sailboat is like marrying a nymphomaniac. You don’t want to do that
but it is great if your best friend does. That way you get all the benefits without any of the upkeep"

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"Snag" fired this volley in news:lkuru.147492
:

I find I get the
best finish if the tip radius is larger than the feed rate ...
--


You mis-read my statement. I did not say "tip radius", I said "EDGE"
radius. Even a 'perfectly' sharp edge doesn't come to a perfect angle.

If it did, it wouldn't withstand any cutting forces. That tiny radius on
the edge has to be a small fraction of the cut depth, or skating will
occur.

LLoyd

"Snag" fired this volley in news:lkuru.147492
:

Lloyd ,
re-read your statement about feed rate vs tool radius . I find I get
the
best finish if the tip radius is larger than the feed rate ...
--

And yes, you do require a larger tip radius than the feed rate.

The thing about the edge radius is important, because most folks don't
have the ability to hand sharpen and hone a tool well enough to take off
a mere tenth. I don't think I do anymore, and certainly not at the
cost/time of decent insert.

LLoyd

On Mon, 16 Dec 2013 05:41:35 -0600, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

"Snag" fired this volley in news:lkuru.147492
:

I find I get the
best finish if the tip radius is larger than the feed rate ...
--


You mis-read my statement. I did not say "tip radius", I said "EDGE"
radius. Even a 'perfectly' sharp edge doesn't come to a perfect angle.

If it did, it wouldn't withstand any cutting forces. That tiny radius on
the edge has to be a small fraction of the cut depth, or skating will
occur.

LLoyd

Blink blink...blink...okay......


--
"Owning a sailboat is like marrying a nymphomaniac. You don’t want to do that
but it is great if your best friend does. That way you get all the benefits without any of the upkeep"

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On Mon, 16 Dec 2013 05:45:54 -0600, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

"Snag" fired this volley in news:lkuru.147492
:

Lloyd ,
re-read your statement about feed rate vs tool radius . I find I get
the
best finish if the tip radius is larger than the feed rate ...
--

And yes, you do require a larger tip radius than the feed rate.

The thing about the edge radius is important, because most folks don't
have the ability to hand sharpen and hone a tool well enough to take off
a mere tenth. I don't think I do anymore, and certainly not at the
cost/time of decent insert.

LLoyd

What..no edge grinder???


--
"Owning a sailboat is like marrying a nymphomaniac. You don’t want to do that
but it is great if your best friend does. That way you get all the benefits without any of the upkeep"

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Gunner Asch fired this volley in
:

What..no edge grinder???

G I said, by hand... A lot of hobby shops don't have anything but a
bench grinder, and don't even _know_ about honing an edge. (some do... I'm
not casting everyone in the mold, Gunner).


Lloyd

Lloyd E. Sponenburgh wrote:
Gunner Asch fired this volley in
:

What..no edge grinder???

G I said, by hand... A lot of hobby shops don't have anything but
a bench grinder, and don't even _know_ about honing an edge. (some
do... I'm not casting everyone in the mold, Gunner).


Lloyd

I keep a piece of hard Arkansas stone right next to my bits . Amazing how
much difference a little polish on the edge can do . And Lloyd , I get what
you meant about edge radius . A controlled breaking of the edge makes a
smoother cut than the random breakage on a microscopic level you can get
when a perfectly sharp edge contacts the work .
--
Snag



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In article ,
"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote:

Your concern about "skating, then hogging" is only a legitimate concern
with positive-rake, fairly dull tooling.

I'd venture to say that it applies in spades if cutting stainless steel,
which work-hardens as you cut it - you can't sneak up on a final
dimension there, IME.

--
Cats, coffee, chocolate...vices to live by
Please don't feed the trolls. Killfile and ignore them so they will go away.

On Mon, 16 Dec 2013 07:20:48 -0600, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

Gunner Asch fired this volley in
:

What..no edge grinder???

G I said, by hand... A lot of hobby shops don't have anything but a
bench grinder, and don't even _know_ about honing an edge. (some do... I'm
not casting everyone in the mold, Gunner).


Lloyd

(Grin).

Get em tiger!


--
"Owning a sailboat is like marrying a nymphomaniac. You don’t want to do that
but it is great if your best friend does. That way you get all the benefits without any of the upkeep"

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"Bob Engelhardt" wrote in message
...
I put an motor-driven feed on my lathe
(http://www.MWDropbox.com/dropbox/ServoPowerFeed.pdf) which I built to
give a minimum feed of .003. I don't know why I chose that value - it's
probably the smallest that the change box will do.

I was just watching a Tubal Cain video on YouTube about the power feed he
put on an Atlas lathe. The Atlas gears only went down to .0046 (IIRC) and
he wanted much finer. (His other lathes went to .0016 & .00076.)

My first thought was to modify my feed to go much finer/slower. But I got
to thinking that there must be some limit. It seems that if the feed was
too fine the bit would just rub until enough feed had accumulated and then
the bit would bite and jump. And the bit's edge would be critical - razor
sharp or better.

How fine do you feed? What are the considerations in doing a very fine
feed?

I think I would use a nice sharp variable radius corner cutter.




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On Mon, 16 Dec 2013 09:26:15 -0800, Gunner Asch
wrote:

On Mon, 16 Dec 2013 07:20:48 -0600, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

Gunner Asch fired this volley in
m:

What..no edge grinder???

G I said, by hand... A lot of hobby shops don't have anything but a
bench grinder, and don't even _know_ about honing an edge. (some do... I'm
not casting everyone in the mold, Gunner).


Lloyd

(Grin).

Get em tiger!

Cheap screw solution 5$

Get an abrasive bristle nylon brush on a shank that mounts
in a drill motor or drill press. Lightly and quickly "buff"
the bit for a small radius, buff longer for a larger radius.
Blue fine grit suggested.

sample
http://www.amazon.com/Dico-541-784-4.../dp/B00004YYD9

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message . 3.70...
"Snag" fired this volley in news:lkuru.147492
:

Lloyd ,
re-read your statement about feed rate vs tool radius . I find I get
the
best finish if the tip radius is larger than the feed rate ...
--

And yes, you do require a larger tip radius than the feed rate.


http://classes.engr.oregonstate.edu/...nish%20lab.pdf

The thing about the edge radius is important, because most folks don't
have the ability to hand sharpen and hone a tool well enough to take off
a mere tenth.

Mostly (for hss) you just need to use an exceptionally hard and fine grit polishing stick..

I don't think I do anymore, and certainly not at the
cost/time of decent insert.

http://platit.com/files/Edge_Prepara...Diego_2007.pdf

LLoyd

"PrecisionmachinisT" fired this volley in
news:QvqdnVI_fvUeETLPnZ2dnUVZ_jadnZ2d@scnresearch. com:

http://platit.com/files/Edge_Prepara...Diego_2007.pdf

Good stuff! Thanks.

Lloyd

"PrecisionmachinisT" fired this volley in
news:QvqdnVI_fvUeETLPnZ2dnUVZ_jadnZ2d@scnresearch. com:

Mostly (for hss) you just need to use an exceptionally hard and fine
grit polishing stick..

True enough, but most amateur folks (and more than I'd like to say of
professionals) don't have it in their dialog to hone the edge they've
just ground on a fairly coarse wheel.

You know that "feels sharp" isn't quite the same as "is uniformly sharp
across the edge".

I'm lucky to have a microscope with a good measuring graticule. If I
don't get what I need from a cutter, I _can_ examine it. Seldom is that
necessary, and it's a waste of time for most jobs. But if I want to take
off just swarf, it can be worthwhile to do. (and, completely eliminated
by buying good inserts).

Lloyd

On Mon, 16 Dec 2013 17:39:46 -0600, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

"PrecisionmachinisT" fired this volley in
news:QvqdnVI_fvUeETLPnZ2dnUVZ_jadnZ2d@scnresearch .com:

Mostly (for hss) you just need to use an exceptionally hard and fine
grit polishing stick..

True enough, but most amateur folks (and more than I'd like to say of
professionals) don't have it in their dialog to hone the edge they've
just ground on a fairly coarse wheel.

And fewer still know what ScarySharp(tm) is.


You know that "feels sharp" isn't quite the same as "is uniformly sharp
across the edge".

Absolutely right.


I'm lucky to have a microscope with a good measuring graticule. If I
don't get what I need from a cutter, I _can_ examine it. Seldom is that
necessary, and it's a waste of time for most jobs. But if I want to take
off just swarf, it can be worthwhile to do. (and, completely eliminated
by buying good inserts).

An extra minute or three on the sharpening end can give you a lot more
time on the cutting end, so it's usually worthwhile.

Lloyd

--
I merely took the energy it takes to pout and wrote some blues.
--Duke Ellington

Ecnerwal wrote:
In article ,
"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote:

Your concern about "skating, then hogging" is only a legitimate
concern with positive-rake, fairly dull tooling.

I'd venture to say that it applies in spades if cutting stainless
steel, which work-hardens as you cut it - you can't sneak up on a
final dimension there, IME.


Hmm , I have to disagree there , a lot depends on how fast you turn the
work . I've had times when I had to take less than a thou off of SS , and it
can be done with a very sharp properly ground 8% cobalt steel cutter M42?
..
--
Snag



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"Snag" fired this volley in
:

Hmm , I have to disagree there , a lot depends on how fast you turn
the
work . I've had times when I had to take less than a thou off of SS ,
and it can be done with a very sharp properly ground 8% cobalt steel
cutter M42?

I have to agree, there. I spent the first 2/3 of my machining experience
with shop-sharpened HSS tooling. I do a LOT of 18-8 and 316 SS stuff,
because of the corrosive qualities of the materials my machines must
process.

I still like high quality carbide inserts the best. (not for interrupted
cuts, though, NO!).

Lloyd