I have an 11 inch swing Harrison gap bed lathe of 1960's origin here in the
UK. I use it for "bits and bobs" and cannot call myself a turner by any
stretch of the imagination. Parting off has always been a bit of a
nightmare for me with rough finishes and sometimes broken tools. I have
only ever bought brazed tip tools, as damage is not too costly

I now find myself in need of drilling 16 mm holes in 3 1/2 inch round bar
mild steel, and then parting off to make washers about 1/4 inch tick with
good finishes both sides. I need to make quite a few, perhaps 12 of them.
Is it worth buying a replaceable tip tool for this? I have no brazed tip
tools that have the reach to part something this thick. Any tips and what
tools do you recommend, as if I buy something it might as well be of a make
that I can stick with for other tools. Nothing too exotic though please,
and remember I am in the UK, so an Internationally available make please.
Thanks for reading.

Chris Wilson wrote:

I have an 11 inch swing Harrison gap bed lathe of 1960's origin here in the
UK. I use it for "bits and bobs" and cannot call myself a turner by any
stretch of the imagination. Parting off has always been a bit of a
nightmare for me with rough finishes and sometimes broken tools. I have
only ever bought brazed tip tools, as damage is not too costly

I now find myself in need of drilling 16 mm holes in 3 1/2 inch round bar
mild steel, and then parting off to make washers about 1/4 inch tick with
good finishes both sides. I need to make quite a few, perhaps 12 of them.
Is it worth buying a replaceable tip tool for this? I have no brazed tip
tools that have the reach to part something this thick. Any tips and what
tools do you recommend, as if I buy something it might as well be of a make
that I can stick with for other tools. Nothing too exotic though please,
and remember I am in the UK, so an Internationally available make please.
Thanks for reading.

I'm not an authority on this but to part 3 1/2", you are talking about a wide parting tool
(waste). I'd chuck and face one side. Saw, followed by facing the other side in lathe or
clamping the good side to a mill table and cleaning up the sawn side.

I've parted 4" but the tool was 1/4" wide.

Wes

Wes

On Fri, 30 Apr 2010 22:06:13 +0100, Chris Wilson
wrote:

I have an 11 inch swing Harrison gap bed lathe of 1960's origin here in the
UK. I use it for "bits and bobs" and cannot call myself a turner by any
stretch of the imagination. Parting off has always been a bit of a
nightmare for me with rough finishes and sometimes broken tools. I have
only ever bought brazed tip tools, as damage is not too costly

I now find myself in need of drilling 16 mm holes in 3 1/2 inch round bar
mild steel, and then parting off to make washers about 1/4 inch tick with
good finishes both sides. I need to make quite a few, perhaps 12 of them.
Is it worth buying a replaceable tip tool for this? I have no brazed tip
tools that have the reach to part something this thick. Any tips and what
tools do you recommend, as if I buy something it might as well be of a make
that I can stick with for other tools. Nothing too exotic though please,
and remember I am in the UK, so an Internationally available make please.
Thanks for reading.
==========
"Parting off" is one of the more difficult lathe operations.
The deeper the cut the more difficult because the blade must
be longer and it is more difficult to lubricate the tool and
remove the chips.

If I understand your question correctly you will be drilling
a 16 m/m [0.630 inches or about 5/8] hole in a 3_1/2 inch
round bar and parting off "slices about 1/4 inch thick or a
little less than 1_1/2 inches per side. This will be a
difficult but not impossible cut.

Given the material, I would suggest a good regular HSS blade
rather than a carbide insert. Insert or cobalt steel are
good for production, but because of cost, availability, and
reduced tendency to breakage, regular HSS will most likely
be a better choice. With a little care you can resharpen
using the typical home grinder or even belt sander.

You may wish to visit the several web sites with information
on parting off. A few of these are
http://start-model-engineering.co.uk...s/parting-off/
http://www.pdfqueen.com/pdf/pa/parting-off/
http://www.modelgeeks.com/Uwe/Forum....-up-front-back
http://www.lathes.co.uk/page13.html
"On small lathes parting-off operations are likely to cause
the greatest trouble. Using a rear-mounted tool post, in
conjunction with an inverted tool, is the best solution."

For some ideas on this style of tool holder see
http://www.hemingwaykits.com/acatalo...Tool_Post.html

and my own web page
http://mcduffee-associates.us/machining/rearcoth.htm


For example parting off kits and blades see
http://www.chronos.ltd.uk/cgi-local/...%23aINP2#aINP2

Everything considered, an alternate method of fabrication
may be better. Consider using 4 inch square pieces, 1/4
inch thick. Drill/bore the center hole, and then use the
center hole to locate. You can remove most of the material
quickly with a band saw, and turn the blanks to the exact
desired diameter. Unless you have a expanding arbor the
right size, you may have to fabricate a locator/arbor, but
this appears to be less work than attempting to part off
from a rod.


-- Unka George (George McDuffee)
...............................
The past is a foreign country;
they do things differently there.
L. P. Hartley (1895-1972), British author.
The Go-Between, Prologue (1953).

On Fri, 30 Apr 2010 18:20:48 -0400, Wes
wrote:

Chris Wilson wrote:

I have an 11 inch swing Harrison gap bed lathe of 1960's origin here in the
UK. I use it for "bits and bobs" and cannot call myself a turner by any
stretch of the imagination. Parting off has always been a bit of a
nightmare for me with rough finishes and sometimes broken tools. I have
only ever bought brazed tip tools, as damage is not too costly

I now find myself in need of drilling 16 mm holes in 3 1/2 inch round bar
mild steel, and then parting off to make washers about 1/4 inch tick with
good finishes both sides. I need to make quite a few, perhaps 12 of them.
Is it worth buying a replaceable tip tool for this? I have no brazed tip
tools that have the reach to part something this thick. Any tips and what
tools do you recommend, as if I buy something it might as well be of a make
that I can stick with for other tools. Nothing too exotic though please,
and remember I am in the UK, so an Internationally available make please.
Thanks for reading.

I'm not an authority on this but to part 3 1/2", you are talking about a wide parting tool
(waste). I'd chuck and face one side. Saw, followed by facing the other side in lathe

That's how I'd do it and have done it.

Chris,
I do this all the time, but your machine is to small. I have 3 Lathes an 18", a 13" and a 10". I do most of my parting operations
on the 13". My 10" is way too light. I have several different parting tools, but the best is a 1" HSS parting tool in an Aloris
holder. This tool is tapered on both sides and mounts at a 10 degree angle. Parting tools mounted parallel to the bed are simply
not as chatter free or smooth. The number 1 problem is chip clearance in this operation. Flood cooling is highly recommended, as
it aids chip clearance. I also use a Sandvik insert type parting tool on the 18". This is mounted in a very stiff tool holder also
at a 10 degree angle. This too works very well, but the inserts fail with the slightest bind and are very expensive, because of
this and my success with HSS, I refrain from using an insert solution. The deeper the cut, the bigger the problem. I will part up
to 4" bar in steel and 6" bar in aluminum. I have parted 6" in steel and 10" in aluminum, but I won't do it again. My
recommendation is to cut the washers in plate with a plasma torch. Drill the 16 mm hole in each and gang turn using a long 16"
bolt supported by a live center in the tail stock. Alternately, you could bandsaw from bar stock and face to size, but you will
find this far more time consuming.
Steve

"Chris Wilson" wrote in message ...
I have an 11 inch swing Harrison gap bed lathe of 1960's origin here in the
UK. I use it for "bits and bobs" and cannot call myself a turner by any
stretch of the imagination. Parting off has always been a bit of a
nightmare for me with rough finishes and sometimes broken tools. I have
only ever bought brazed tip tools, as damage is not too costly

I now find myself in need of drilling 16 mm holes in 3 1/2 inch round bar
mild steel, and then parting off to make washers about 1/4 inch tick with
good finishes both sides. I need to make quite a few, perhaps 12 of them.
Is it worth buying a replaceable tip tool for this? I have no brazed tip
tools that have the reach to part something this thick. Any tips and what
tools do you recommend, as if I buy something it might as well be of a make
that I can stick with for other tools. Nothing too exotic though please,
and remember I am in the UK, so an Internationally available make please.
Thanks for reading.

A couple of the most important factors required for a successful
parting/cut-off operation are machine rigidity and machine rigidity.

A huge lathe isn't the ultimate solution, but large lathes with a lot of
mass and firmly adjusted slides do work well.

Another important factor is working (cutting) as close to the headstock as
practical. The tailstock isn't used for parting, so having the workpiece
securely held close to the headstock is somewhat vital. Proper headstock
bearing preload will reduce, or eliminate, but certainly minimize chatter.

A very good cutting lubricant (not engine oil or other improvised product)
applied generously will definitely assist the cutting operation.


I'm familiar with hand ground HSS parting tools, not carbide or carbide
inserts.
How the cutting tool is ground, and how it's presented to the workpiece are
also significant.
With too much front relief, the cutting tool may tend to dig into the work,
with too little front relief, the cutting tool may just rub the workpiece.
So, right in-between those 2 conditions is precisely the correct front
relief angle.
I've found that the correct front relief on my HSS parting tools is nearly
vertical, when held in the tool holder.
Many parting tool holders introduce some top relief angle, just in the way
the tool is held.
Setting the tool cutting edge height precisely on center with the
workpiece's axial center height is generally the best presentation.

Grinding a chip breaker into the front end of the cutting tool can greatly
improve the performance of the cutting action.
Grinding the tool with a top rake chip breaker, or a lateral groove (in line
with the length of the cutting tool) near the tip will help feed the chip
out of the groove in the workpiece.
Many HSS parting/cutoff blades are tapered down the sides, so a top rake
chip breaker should be kept to a minimum depth at the tip, as the cutting
tool tip will become narrower than the rest of the tool.
The tip of the tool needs to be square, looking down on the tip.. an angle
can cause the tool to tend to feed a bit sideways.

The cutting tool must be fed squarely into the work. Checking that the
cutting blade alignment is precisely parallel to the front face of the chuck
is a common practice.

I've accomplished cut-offs on significantly lighter lathes and 1/8" wide HSS
cut-off tools (and manual crossfeed), so there is a good chance that your
job could be done with your lathe.
Locking down the carriage is a common practice, but I don't know how well
that works with a gap-bed model with the carriage near the headstock.
Low spindle RPM is going to be of importance, especially near the OD of your
workpiece.

While I've found cut-off techniques that work for myself, the surface finish
isn't usually very good on my parts, but filing, grinding, belt sanding or
other techniques can improve that.

Since your parts will have a center hole, it's best to drill the hole first,
then the cut-off tool doesn't need to be fed in to the center of the
workpiece.

These are most of the aspects that I've found helpful in parting on my wimpy
lathes.
When you find the correct combination of techniques, your anxiety/nightmare
will fade.

When you find the right combination of cutting tool geometry, speed and feed
rates, it's very gratifying.

--
WB
..........


"Chris Wilson" wrote in message
...
I have an 11 inch swing Harrison gap bed lathe of 1960's origin here in the
UK. I use it for "bits and bobs" and cannot call myself a turner by any
stretch of the imagination. Parting off has always been a bit of a
nightmare for me with rough finishes and sometimes broken tools. I have
only ever bought brazed tip tools, as damage is not too costly

I now find myself in need of drilling 16 mm holes in 3 1/2 inch round bar
mild steel, and then parting off to make washers about 1/4 inch tick with
good finishes both sides. I need to make quite a few, perhaps 12 of them.
Is it worth buying a replaceable tip tool for this? I have no brazed tip
tools that have the reach to part something this thick. Any tips and what
tools do you recommend, as if I buy something it might as well be of a
make
that I can stick with for other tools. Nothing too exotic though please,
and remember I am in the UK, so an Internationally available make please.
Thanks for reading.

Not so much fun, of course, but you could try your local industrial
supplier.
They may have the washers you want.

Hum...

Hard to believe I just suggested this. Making special sized washers
was why I bought my first lathe ah.. a few years ago. :-)

DOC

Bogus beer...
http://bogusbeer.appspot.com/

On Apr 30, 5:06*pm, Chris Wilson wrote:
I have an 11 inch swing Harrison gap bed lathe of 1960's origin here in the
UK. ...
I now find myself in need of drilling 16 mm holes in 3 1/2 inch round bar
mild steel, and then parting off to make washers about 1/4 inch tick with
good finishes both sides. ...

My 10" South Bend parts reasonably well to 1" diameter with a 1/16"
HSS blade and cutting oil dripped into the groove. It jams quickly if
I stop the oil. I use a hand-held needle oiler, several here think
that's too tedious. There are needles that thread onto grease gun hose
if you want to set up a drip system. A drop every few seconds seems to
be enough.

When I make parts from 3" round steel I part in about half an inch and
then take it to the 4"x6" horizontal bandsaw. I center the blade in
the groove and cut in about the height of the blade, then turn the
work a little, etc, all or most of the way around. Make a fresh start
if it wanders. This kerf guides the blade straight to finish sawing
off the part, even if the saw isn't adjusted quite square. It only
controls the blade on the entry side so maybe cutting half way around
is enough.

I clean up the sawn side of thin disks in the 3-jaw with reversed
jaws, using thin parallels to space them out from the step. One
parallel rests on two lower jaws, the other and the disk aren't too
fussy to hold if I jam the disk inward with something in the tailstock
chuck, leaving a hand free to tighten the chuck key. I take only light
radial cuts to avoid shifting the disk.

This method isn't fast but it lets me cut off pieces from stock that's
too long to part unsupported in the chuck, and to make the first
parting cut with tailstock center support. In case you don't know you
can't part completely through that way, it will bend and jam near the
end.

jsw

On Sat, 1 May 2010 05:03:20 -0700 (PDT), doc wrote:


Not so much fun, of course, but you could try your local industrial
supplier.
They may have the washers you want.


McMaster comes pretty close...

91117A235
Zinc-Plated Steel Jumbo Flat Washer 5/8" Screw Size, 3" OD, .23"-.27"
Thick
In stock at $13.61 per Pack
This product is sold in Packs of 5

Otherwise, I agree with Steve; cut the blanks from plate.

--
Ned Simmons

On Sat, 1 May 2010 05:03:20 -0700 (PDT), the renowned doc
wrote:


Not so much fun, of course, but you could try your local industrial
supplier.
They may have the washers you want.

And if they don't... bokers.com

Hum...

Hard to believe I just suggested this. Making special sized washers
was why I bought my first lathe ah.. a few years ago. :-)

DOC

Bogus beer...
http://bogusbeer.appspot.com/


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

Don Foreman wrote:

I'm not an authority on this but to part 3 1/2", you are talking about a wide parting tool
(waste). I'd chuck and face one side. Saw, followed by facing the other side in lathe

That's how I'd do it and have done it.

So what is the width and height of your parting tool? I like the tee type with a curve
ground down the length of the tool to help fold the curl.



Wes

On Sat, 01 May 2010 18:04:54 -0400, Wes
wrote:

Don Foreman wrote:

I'm not an authority on this but to part 3 1/2", you are talking about a wide parting tool
(waste). I'd chuck and face one side. Saw, followed by facing the other side in lathe

That's how I'd do it and have done it.

So what is the width and height of your parting tool? I like the tee type with a curve
ground down the length of the tool to help fold the curl.



Wes

My parting tool is 1/16" thick, about 1" high. I may have a 3/32"
thick parting blade too. I'd do like you said: face it, saw it, face
the other side and not use the parting tool at all on this job.

On May 2, 12:14*am, Don Foreman wrote:
...

My parting tool is 1/16" thick, about 1" high. I may have a 3/32"
thick parting blade too. *I'd do like you said: face it, saw it, face
the other side and not use the parting tool at all on this job. *

If you don't have a good bandsaw a shallow parting groove helps you
guide the saw cut.

jsw

On Sun, 2 May 2010 04:31:51 -0700 (PDT), Jim Wilkins wrote:

On May 2, 12:14*am, Don Foreman wrote:
...

My parting tool is 1/16" thick, about 1" high. I may have a 3/32"
thick parting blade too. *I'd do like you said: face it, saw it, face
the other side and not use the parting tool at all on this job. *

If you don't have a good bandsaw a shallow parting groove helps you
guide the saw cut.

jsw

Thanks to everyone for some gret info. I am in the UK and a few searches
haven't shown any commercially available steel discs or washers that I
could use or modify, so I think I'll either buy a plasma cutter, which is
something I would most likely use a lot for other jobs, or bandsaw the
stock and face it up. I am always amazed at the breadth of knowledge and
the willingness to take the time to post quite lengthy answers to help
others out, thanks ever so much guys