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Posted by Michael Koblic on June 6, 2008, 10:02 pm
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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
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Posted by Don Young on June 6, 2008, 10:37 pm
Please log in for more thread options
>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
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Posted by Lew Hartswick on June 6, 2008, 10:37 pm
Please log in for more thread options 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/ee238/LewHartswick/?action=view¤t=9-Tapholders.jpg
http://s233.photobucket.com/albums/ee238/LewHartswick/?action=view¤t=Abunchofholders.jpg
http://s233.photobucket.com/albums/ee238/LewHartswick/?action=view¤t=Abunchofholders.jpg
...lew...
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Posted by on June 6, 2008, 10:43 pm
Please log in for more thread options > I have spent a very long and unproductive day trying to cut a 5/16-24 thre=
ad
> 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 agai=
n,
> 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 thre=
ad
> 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 littl=
e
> 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 ni=
ce
> 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 sto=
ck
> 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
Re: 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
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Posted by Michael Koblic on June 7, 2008, 12:14 am
Please log in for more thread options
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
|
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>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
>