I have spent a very long and unproductive day trying to cut a 5/16-24 thread
on a cut-off piece of 5/16 bolt.
I knew things were not going to go well when I could not get the
*never-previously-used* die to even bite. I chamfered, then chamfered again,
nothing. eventually I made the tip almost conical. I got some purchase but
a) the effort to cut was disproportionate and b) the end result was a thread
which was skewed - and not subtly!
I tried again with another piece of 5/16 rod - same result.

I hit the books to see if I omitted something glaring. Most of the texts I
have are big on starting *taps* straight but they did not stress the dies so
much.

In the end I borrowed the tap technique: I gripped the rod in the chuck of
my drill press. I clamped the die in my drill press vise (there is a little
shoulder that allows it to rest flat). I raised the table and centered and
clamped the vise with the rod touching. I turned the rod with a pair of
vise-grips while simultaneously feeding the spindle (it would be really nice
to have three hands!). After the first turn the feed took care of itself.
This way I cut a reasonably straight thread but the effort was much harder
than I expected. Also, the vise-grips make a mess of the rod.

I tried it again with the cut-off bolt. This time I turned the spindle of
the drill press directly by a makeshift lever improvised from the same stock
and inserted into the chuck key holes. It was even harder to cut this time
(I checked the diameter etc. - all identical).

I should mention that the whole workshop was swimming in Rapid Tap at the
end - no dry cutting here.

I suspect that the die is crap and I will go and get another one but the
whole process brought up some interesting questions. The most important of
them is:
How does everyone manage to get a straight thread when die cutting?

I think the method I use is OK provided the workpiece *can* be held in a
chuck but if not, I am stumped.

BTW, if using a drill press to start a tap in a hole how do you turn the
tap? Do you grind flat spots on your taps to get a better wrench purchase?

--
Michael Koblic,
Campbell River, BC

"Michael Koblic" wrote in message
news
I have spent a very long and unproductive day trying to cut a 5/16-24
thread on a cut-off piece of 5/16 bolt.
I knew things were not going to go well when I could not get the
*never-previously-used* die to even bite. I chamfered, then chamfered
again, nothing. eventually I made the tip almost conical. I got some
purchase but a) the effort to cut was disproportionate and b) the end
result was a thread which was skewed - and not subtly!
I tried again with another piece of 5/16 rod - same result.

I hit the books to see if I omitted something glaring. Most of the texts I
have are big on starting *taps* straight but they did not stress the dies
so much.

In the end I borrowed the tap technique: I gripped the rod in the chuck of
my drill press. I clamped the die in my drill press vise (there is a
little shoulder that allows it to rest flat). I raised the table and
centered and clamped the vise with the rod touching. I turned the rod with
a pair of vise-grips while simultaneously feeding the spindle (it would be
really nice to have three hands!). After the first turn the feed took care
of itself. This way I cut a reasonably straight thread but the effort was
much harder than I expected. Also, the vise-grips make a mess of the rod.

I tried it again with the cut-off bolt. This time I turned the spindle of
the drill press directly by a makeshift lever improvised from the same
stock and inserted into the chuck key holes. It was even harder to cut
this time (I checked the diameter etc. - all identical).

I should mention that the whole workshop was swimming in Rapid Tap at the
end - no dry cutting here.

I suspect that the die is crap and I will go and get another one but the
whole process brought up some interesting questions. The most important of
them is:
How does everyone manage to get a straight thread when die cutting?

I think the method I use is OK provided the workpiece *can* be held in a
chuck but if not, I am stumped.

BTW, if using a drill press to start a tap in a hole how do you turn the
tap? Do you grind flat spots on your taps to get a better wrench purchase?

--
Michael Koblic,
Campbell River, BC

Some dies and some die stocks have adjustable or replaceable guides to hold
everything square. Some dies and taps are of poor quality, are hard to
start, and require a lot of torque to operate. A two piece tap wrench (or
the clamp from a tubing flaring set) can be clamped tightly around the tap
to turn it in the drill press. I can generally get a tap up to 1/2" started
by tightening the chuck three times, once in each key hole. Once I get the
thread started, I generally remove the job from the drill press and finish
tapping by hand. A purpose built die holder or tap holder seems desireable
to hold everything straight and make it easier to turn. I have a set of
Snap-On dies that have double hex outsides (12 pointed like a box wrench or
socket) and I use these butted against the lathe tailstock to start threads
on work held in the lathe.

Don Young

Michael Koblic wrote:

BTW, if using a drill press to start a tap in a hole how do you turn the
tap? Do you grind flat spots on your taps to get a better wrench purchase?


Here is the way to hold a tap in a chuck.

http://s233.photobucket.com/albums/e...Tapholders.jpg
http://s233.photobucket.com/albums/e...hofholders.jpg
http://s233.photobucket.com/albums/e...hofholders.jpg

...lew...

On Jun 6, 8:02*pm, "Michael Koblic" wrote:
I have spent a very long and unproductive day trying to cut a 5/16-24 thread
on a cut-off piece of 5/16 bolt.
I knew things were not going to go well when I could not get the
*never-previously-used* die to even bite. I chamfered, then chamfered again,
nothing. eventually I made the tip almost conical. I got some purchase but
a) the effort to cut was disproportionate and b) the end result was a thread
which was skewed - and not subtly!
I tried again with another piece of 5/16 rod - same result.

I hit the books to see if I omitted something glaring. Most of the texts I
have are big on starting *taps* straight but they did not stress the dies so
much.

In the end I borrowed the tap technique: I gripped the rod in the chuck of
my drill press. I clamped the die in my drill press vise (there is a little
shoulder that allows it to rest flat). I raised the table and centered and
clamped the vise with the rod touching. I turned the rod with a pair of
vise-grips while simultaneously feeding the spindle (it would be really nice
to have three hands!). After the first turn the feed took care of itself.
This way I cut a reasonably straight thread but the effort was much harder
than I expected. Also, the vise-grips make a mess of the rod.

I tried it again with the cut-off bolt. This time I turned the spindle of
the drill press directly by a makeshift lever improvised from the same stock
and inserted into the chuck key holes. It was even harder to cut this time
(I checked the diameter etc. - all identical).

I should mention that the whole workshop was swimming in Rapid Tap at the
end - no dry cutting here.

I suspect that the die is crap and I will go and get another one but the
whole process brought up some interesting questions. The most important of
them is:
How does everyone manage to get a straight thread when die cutting?

I think the method I use is OK provided the workpiece *can* be held in a
chuck but if not, I am stumped.

BTW, if using a drill press to start a tap in a hole how do you turn the
tap? Do you grind flat spots on your taps to get a better wrench purchase?

--
Michael Koblic,
Campbell River, BC

dies
A lot of the dies out there are only suitable for rethreading,
particularly if you got them at a hardware store and they're hex in
shape. If it's Chinese, you've now got a nice paperweight. Round
split-button dies can be adjusted over- or undersize to fit the female
threads. About the only kind I have. You can order good ones from
MSC or the like.

5/16" bolt shanks aren't necessarily the right size for threading with
dies. They roll threads these days and cheap hardware store bolts
aren't necessarily precision stuff. Sure you didn't have a hardened
bolt?

Get a good die stock. The ones I use for freehand threading have an
"iris", a set of fingers that can be adjusted to the workpiece
diameter. I've seen these at True Value and Ace, the ones I use most
I bought at Sears decades back, before they peddled junk.

Most of my threading with a die is done in the lathe with a die
holder, ditto tapping.

Tap shanks are hard and will slip in a drill chuck, not recommended to
do it that way. You can buy/make a tap wrench with an extension that
can be chucked and slides up and down, a relatively cheap item, Enco
had them at one time. Another way is to get a decent T-handle tap
wrench with an accurately centered center hole, Starrett made the ones
I use, then put a center in the drill press to start the thing
straight. I do it this way in the lathe. Or you can make/buy a
tapping block to start things square. Get decent tap wrenches, the T-
handles with spring fingers made from the body should be junked, the
best sort have spring-loaded hardened jaws. Dog-bones are handy to
have on hand, too.

Stan

"Michael Koblic" wrote in message
news
I have spent a very long and unproductive day trying to cut a 5/16-24
thread on a cut-off piece of 5/16 bolt.

Big Snip

The best method that I have used is to hold the die in a lathe. Make or buy
a die holder for the cross slide. Set up the lathe for screw cutting, at the
same pitch as the die. The die can be set square by running it up to a face
plate, and of course it must be at centre height. Mount the workpiece in the
chuck. Engage the leadscrew, and crank the lathe by hand. Very often, you
can just grasp the chuck to do this. with a good hefty chuck, the key can be
used as a handle. Use plenty of cutting oil, and don't forget to back off
every quarter turn to clear the swarf. The steel in most bolts is intended
for rolled threads, and may not be good for threading with a die or
screwcutting. Better to find some better stuff to practice on.


Steve R.



--
Reply address munged to bugger up spammers

wrote in message
...
On Jun 6, 8:02 pm, "Michael Koblic" wrote:
A lot of the dies out there are only suitable for rethreading,
particularly if you got them at a hardware store and they're hex in
shape. If it's Chinese, you've now got a nice paperweight. Round
split-button dies can be adjusted over- or undersize to fit the female
threads. About the only kind I have. You can order good ones from
MSC or the like.

*****Is this true of *all* hexagonal dies? I was looking at some Irwin dies
in the House fo Tools yesterday. They are hexagonal but nothing on the
package says "for re-threading only".

5/16" bolt shanks aren't necessarily the right size for threading with
dies. They roll threads these days and cheap hardware store bolts
aren't necessarily precision stuff. Sure you didn't have a hardened
bolt?

*****That I cannot tell. However, the rod I switched to I am pretty sure was
not, yet the result was much the same. If I absolutely had to use the bolt,
what would heating it up (annealing) do?

Get a good die stock. The ones I use for freehand threading have an
"iris", a set of fingers that can be adjusted to the workpiece
diameter. I've seen these at True Value and Ace, the ones I use most
I bought at Sears decades back, before they peddled junk.

*****Mine has just that. But...the iris is exactly concentric, the die in
the stock, when the screws are tightened, is not. This renders the
arrangement useless in this case. The openings are not lined-up.

Most of my threading with a die is done in the lathe with a die
holder, ditto tapping.

Tap shanks are hard and will slip in a drill chuck, not recommended to
do it that way. You can buy/make a tap wrench with an extension that
can be chucked and slides up and down, a relatively cheap item, Enco
had them at one time. Another way is to get a decent T-handle tap
wrench with an accurately centered center hole, Starrett made the ones
I use, then put a center in the drill press to start the thing
straight. I do it this way in the lathe. Or you can make/buy a
tapping block to start things square. Get decent tap wrenches, the T-
handles with spring fingers made from the body should be junked, the
best sort have spring-loaded hardened jaws. Dog-bones are handy to
have on hand, too.

*****Thanks. Food for thought.


--
Michael Koblic,
Campbell River, BC

Are you sure you don't have a hardened bolt? If the die won't get a
bite on the rod/bolt with a good chamfer, either the bolt is hard or the
die is soft.

Michael Koblic wrote:
I have spent a very long and unproductive day trying to cut a 5/16-24 thread
on a cut-off piece of 5/16 bolt.
I knew things were not going to go well when I could not get the
*never-previously-used* die to even bite. I chamfered, then chamfered again,
nothing. eventually I made the tip almost conical. I got some purchase but
a) the effort to cut was disproportionate and b) the end result was a thread
which was skewed - and not subtly!
I tried again with another piece of 5/16 rod - same result.

I hit the books to see if I omitted something glaring. Most of the texts I
have are big on starting *taps* straight but they did not stress the dies so
much.

In the end I borrowed the tap technique: I gripped the rod in the chuck of
my drill press. I clamped the die in my drill press vise (there is a little
shoulder that allows it to rest flat). I raised the table and centered and
clamped the vise with the rod touching. I turned the rod with a pair of
vise-grips while simultaneously feeding the spindle (it would be really nice
to have three hands!). After the first turn the feed took care of itself.
This way I cut a reasonably straight thread but the effort was much harder
than I expected. Also, the vise-grips make a mess of the rod.

I tried it again with the cut-off bolt. This time I turned the spindle of
the drill press directly by a makeshift lever improvised from the same stock
and inserted into the chuck key holes. It was even harder to cut this time
(I checked the diameter etc. - all identical).

I should mention that the whole workshop was swimming in Rapid Tap at the
end - no dry cutting here.

I suspect that the die is crap and I will go and get another one but the
whole process brought up some interesting questions. The most important of
them is:
How does everyone manage to get a straight thread when die cutting?

I think the method I use is OK provided the workpiece *can* be held in a
chuck but if not, I am stumped.

BTW, if using a drill press to start a tap in a hole how do you turn the
tap? Do you grind flat spots on your taps to get a better wrench purchase?

Michael Koblic writes:

How does everyone manage to get a straight thread when die cutting?

Chuck work in lathe. Position die in holder by hand at the end of the
work. Push up against opposite side of die with tip of closed drill chuck
in the tailstock, so it keeps the die "normal" to the work. Turn die
handles back and forth by hand while feeding tailstock.

This holds the die in two angular degrees of freedom, "pitch" and "yaw", if
you will, and in the Z axis. Does not constrain the "roll" (which you want
to spin by hand anyway), nor the X and Y, which are roughly constrained by
the self-centering tendency of the die around the work.

Reality is always 6 degrees of freedom that must submit to your will via
tools.

On Jun 6, 10:02 pm, "Michael Koblic" wrote:
I have spent a very long and unproductive day trying to cut a 5/16-24 thread
on a cut-off piece of 5/16 bolt.

I hit the books to see if I omitted something glaring. Most of the texts I
have are big on starting *taps* straight but they did not stress the dies so
much....

Because external threads are so much easier to cut on a lathe.

...How does everyone manage to get a straight thread when die cutting?

It isn't easy, and so-called 'drunken' threads were common way back
when threads were cut by hand. Your drill press technique or some
variation on it helps. If you can turn or file down the end enough
that the die slides on or at least cuts easily it's more likely to
start straight, though not always concentric. I've used a vee block to
square the die and line up the shank of a cut-off headed bolt that was
too big for the chuck.

You might be able to sharpen the die by grinding the holes with a
Dremel. Most of my larger taps and dies came from second-hand stores
and I resharpened them until they cut satisfactorily. Carefully hand-
grinding the front face of a cutting edge, where the chips flow,
shouldn't affect the geometry of the edge enough to matter for home
use. Take a small equal cut off all edges and check, then repeat,
rather than trying to do each one completely, so they stay about the
same size. A sharp edge doesn't reflect light.

The dies sold in hardware stores are good for cleaning rust and dings
off old threads, not so good for cutting them from round stock. As
others have written, dies from an industrial supplier are much better.

See why we buy a lathe? I cut the thread part way on mine and finish
with a die, using the tailstock to start it square.

BTW, if using a drill press to start a tap in a hole how do you turn the
tap? Do you grind flat spots on your taps to get a better wrench purchase?

I have but if they are deep enough to not slip they weaken the tap
considerably. On a two-flute tap I grind shallow wrench flats into the
shank end of the threads.

I chuck the tap, loosen the belt and turn the pulley by hand to start
the tap straight. Just before (or when) it slips I switch to a tap
wrench, being careful to apply equal pressure to both ends of the
handle so the tap isn't pulled sideways until there are a few full
threads to hold it straight. The long straight types of tap wrench
that clamp in the center work best here because they fit in under the
chuck.

Another solution is a good tee-handled tap wrench that can be guided
at the upper end. The smaller ones fit into a loosened chuck, some
have a center hole and you can chuck a guide pin, there is a type with
a separate guide on the top. The trouble with them is they stack up so
high you may have to raise the head to use them and lower it to drill,
losing position.

After the Army I worked as an assembler building custom equipment for
the auto industry so I got plenty of practice locating, drilling and
tapping holes by hand on large machines. After a week or so I stopped
breaking taps and eventually learned to tap with a reversing power
drill. It just takes sharp tools and practice to learn the feel.

They made me go through all the assembly, machining, wiring and
drafting positions before promoting me to project engineer. It was a
very useful experience that unfortunately can't always be imposed on
fresh engineering graduates.

Jim Wilkins

On Fri, 6 Jun 2008 19:02:24 -0700, "Michael Koblic"
wrote:

I have spent a very long and unproductive day trying to cut a 5/16-24 thread
on a cut-off piece of 5/16 bolt.
I knew things were not going to go well when I could not get the
*never-previously-used* die to even bite. I chamfered, then chamfered again,
nothing. eventually I made the tip almost conical. I got some purchase but
a) the effort to cut was disproportionate and b) the end result was a thread
which was skewed - and not subtly!
I tried again with another piece of 5/16 rod - same result.

I hit the books to see if I omitted something glaring. Most of the texts I
have are big on starting *taps* straight but they did not stress the dies so
much.


I had the identical problem with a new chinese die. 1/2 inch national
coarse thread.

I persisted until I got the rod threaded. beautiful thread in the end.
.....but 1.2mm under spec diameter! no wonder it wouldnt engage on the
rod.

I went out and bought an australian made die and had not a problem
threading the rod. and it was bang on spec diameter.

throw your die at the neighbours cats and get one made by a quality
manufacturer. your die is more than likely a piece of garbage.
Stealth Pilot

"Jim Wilkins" wrote in message
...
On Jun 6, 10:02 pm, "Michael Koblic" wrote:

See why we buy a lathe?

The HoT 7x12 lathe just gone on sale from $999.0 to $750.0. I suspect it is
too small, though. Furthermore, it would be a really big step in that I
would not really know what I am buying.

I am looking at local colleges for a course on lathe/mill machine use. I
have a long and relatively successful history of teaching things myself but
I have feeling this would be one of those activities where time and money
might be saved by learning on the actual instrument rather than from books
(come think of it, there might be DVDs, too).

Of course, if my Better Half returned from Toronto and found a lathe in the
garage I just might get my gonads removed.

Now here is a very basic question: I need a new drill press. Rather than
buying a bigger and more expensive one, would it make sense to add to the
pot and buy a mill? I.e. will mill do what drill press does as well as the
milling?

--
Michael Koblic,
Campbell River, BC

On Jun 7, 7:34*pm, "Michael Koblic" wrote:
"Jim Wilkins" wrote in message
On Jun 6, 10:02 pm, "Michael Koblic" wrote:
See why we buy a lathe?

I am looking at local colleges for a course on lathe/mill machine use. I
have a long and relatively successful history of teaching things myself but
I have feeling this would be one of those activities where time and money
might be saved by learning on the actual instrument rather than from books
(come think of it, there might be DVDs, too).

I was more or less pointed toward the Bridgeport and told to have fun
with it. The kid who used it showed me how to change speeds and left.
I burned and dulled the first end mill by overspeeding and overfeeding
it but was OK after that. Likewise the checkout I got on a CNC Bridgie
was turn it on, let it boot, home it, this is jog mode, now make some
chips.

Having someone around to answer questions was very valuable, though.


Of course, if my Better Half returned from Toronto and found a lathe in the
garage I just might get my gonads removed.

Now here is a very basic question: I need a new drill press. Rather than
buying a bigger and more expensive one, would it make sense to add to the
pot and buy a mill? I.e. will mill do what drill press does as well as the
milling?
Michael Koblic,

Generally yes, with the exceptions that a floor drill press can drill
into the end of a much longer piece, and you can clamp a bench drill
press onto a large beam or plate to drill it. IMHO a drill press might
be equal or slightly better for woodworking, but a vertical knee mill
or mill-drill is excellent for drilling metal. I don't know enough
about new equipment to suggest any of them.

Jim Wilkins

Now here is a very basic question: I need a new drill press. Rather than
buying a bigger and more expensive one, would it make sense to add to the
pot and buy a mill? I.e. will mill do what drill press does as well as the
milling?
Michael Koblic,

Generally yes, with the exceptions that a floor drill press can drill
into the end of a much longer piece, and you can clamp a bench drill
press onto a large beam or plate to drill it. IMHO a drill press might
be equal or slightly better for woodworking, but a vertical knee mill
or mill-drill is excellent for drilling metal. I don't know enough
about new equipment to suggest any of them.

Jim Wilkins

one comment on mills versus drill presses - some mills (mine for example) do
not have a handle for lowering the quill like a drill press does so to drill
things you raise the table - you have no feel for what is happening that
way, so I find I like to have both.


** Posted from http://www.teranews.com **

On Jun 8, 3:43*am, "William Noble" wrote:

one comment on mills versus drill presses - some mills (mine for example) do
not have a handle for lowering the quill like a drill press does so to drill
things you raise the table - you have no feel for what is happening that
way, so I find I like to have both.

Is it a new machine or an antique?

One of the few things I like on the RF-31 mill drill is its 5" quill
stroke. The 3" stroke on my mill is more typical, and adequate to
drill a hole but when I have to use several different tools at the
same place it's limiting. It helps to buy tools that are all
approximately the same length, such as large 1/2" shank drill bits
that are about as long as a stub-length pilot bit in a chuck. Taps are
a problem. I've seen shop-made tap holders that used 4 setscrews to
clamp the square end.

Jim Wilkins

"Jim Wilkins" wrote in message
...
On Jun 8, 3:43 am, "William Noble" wrote:

one comment on mills versus drill presses - some mills (mine for example)
do
not have a handle for lowering the quill like a drill press does so to
drill
things you raise the table - you have no feel for what is happening that
way, so I find I like to have both.

Is it a new machine or an antique?

One of the few things I like on the RF-31 mill drill is its 5" quill
stroke. The 3" stroke on my mill is more typical, and adequate to
drill a hole but when I have to use several different tools at the
same place it's limiting. It helps to buy tools that are all
approximately the same length, such as large 1/2" shank drill bits
that are about as long as a stub-length pilot bit in a chuck. Taps are
a problem. I've seen shop-made tap holders that used 4 setscrews to
clamp the square end.

Jim Wilkins

My machine is an Abene VHF-3 - they are still made, though this particular
machine was made in 1970 - 6 hp spindle, 2 hp ways - what is good is that
it's horizontal/vertical because the head rotates and it has an overarm.
But the quill downfeed was optional and I've never seen an Abene mill with
that option - if I saw one, they go cheaply enough I might buy the whole
mill just to get it.


** Posted from http://www.teranews.com **

One can extend the ability of the floor standing (or bench - mount 180 degrees
from normal and over the bench edge... Use strong bench /metal plate...

You can use a screw up table - Z table IIRC from the floor jacking up the part.

Martin

Martin H. Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
TSRA, Endowed; NRA LOH & Patron Member, Golden Eagle, Patriot's Medal.
NRA Second Amendment Task Force Charter Founder
IHMSA and NRA Metallic Silhouette maker & member.
http://lufkinced.com/


William Noble wrote:
Now here is a very basic question: I need a new drill press. Rather than
buying a bigger and more expensive one, would it make sense to add to the
pot and buy a mill? I.e. will mill do what drill press does as well as the
milling?
Michael Koblic,

Generally yes, with the exceptions that a floor drill press can drill
into the end of a much longer piece, and you can clamp a bench drill
press onto a large beam or plate to drill it. IMHO a drill press might
be equal or slightly better for woodworking, but a vertical knee mill
or mill-drill is excellent for drilling metal. I don't know enough
about new equipment to suggest any of them.

Jim Wilkins

one comment on mills versus drill presses - some mills (mine for example) do
not have a handle for lowering the quill like a drill press does so to drill
things you raise the table - you have no feel for what is happening that
way, so I find I like to have both.


** Posted from http://www.teranews.com **


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