Tried parting a HSS shaft using a HSS cutoff blade last night and it
didn't even scratch the surface. What's the best type of cutoff blade
to use and are there any special tips? Also, will tin coated carbide
inserts be sufficient for turning down a HSS shaft? Thanks!
What's the heat-treat condition of the shaft you're turning? If it's
annealed, it is possible to cut it with a HSS tool, but it's truly
Carbide is a much better bet. It's also hard enough to cut fully hardened
HSS, but you need an absolutely rigid setup and a good, tight, and rigid
lathe for that kind of work.
BTW, the "tin" coating actually is TiN: titanium nitride. It helps with tool
life but it doesn't do much to improve the hardness of materials you can
cut -- after a few seconds of use, anyway.
Thanks Ed. After Googling some more, the general concensus seems to be
that Dremel plus abrasive cutoff wheel will work (shaft is only
3/16"). I should be okay there but need to turn down a portion of the
shaft from 3/16" to 1/8" after cutting. Is this a waste of time or
worth a try?
Oh, anything is worth a try. Since you're only knocking off 1/16" from the
diameter, you probably could grind that off with the Dremel, too, if you're
only talking about a short section. Just rig up something to hold the Dremel
in the toolpost and go *very* slowly. Cover your lathe bed and as much of
the saddle/cross slide/compound as you can. I like using aluminum foil for
that job but oiled newspaper works fine, too. Just leave a few spots
oil-free so you can tape the paper down.
For example, I have a table clamp, or whatever they call it, for my Dremel,
which holds it in position for hands-free grinding. If I take it apart I can
get the stem of the holder in my rocker toolpost. This is adequate for very
light and non-precision grinding, and probably would do the job for you.
I've even held the Dremel in place with duct tape when I had to. (I could
lose my amateur machinist credentials for that one. )
"Ed Huntress" wrote: (clip) Cover your lathe bed and as much of
See, this is an example of why it is good to check threads you think you're
not interested in. Here's a good suggestion that would be easily missed.
While we're on this subject, old machining books tell you to used oiled
rags. That was back when they told you to tuck your tie inside of your shop
coat. Don't do it -- rags have gotten caught in turning chucks and they can
Aluminum foil is neat and easy. Just don't slip up and dump the grinding
grit in your chuck or on the bedway when you take it off. I try to make a
sort of tray out of the foil, so the grit doesn't just fall off. Oil on the
paper will hold some of the grit, but don't count on that, either. I spray
the paper with WD-40 because it's easy, not because it's the best way.
And don't grind on a good lathe any more than you have to.
I'm sure most members here know these things but some newbie may find it
worthwhile to consider.
It depends on how crafty you are.
I do not grind long shafts on my machine, so I haven't had much experience
trying to make it all behave like a fancy way cover. I think it would be
Disaster! The tip of the insert broke off.
Here's the story....The drill chuck I have is limited to a capacity of
1/8" and I want to use a 3/16" countersink in it. Think I'll machine a
holder out of normal steel with a 1/8" shaft and wedge the countersink
in the holder. Thanks for the help.
Disaster! The tip of the insert broke off.
That's a mighty small drill chuck. I would be worried about springing it,
with a larger bit that has a reducing shank. Are you drilling steel?
Looks like it's my lucky day. The drill press manufacturer was able to
hand pick a 0JT mount Jacobs 5/32" chuck with capacity just greater
than 3/16". I'll just buy that along with some 0JT wedges. Thanks
Great. That sounds like a much better solution.
FWIW, you may be interested to know that typical HSS drill bits -- good
ones, that is -- are hardened at the tip and up through the flutes, but that
the butt end of the shank is left somewhat softer, to allow the bit to take
some bending stress without breaking. That's why it's so easy to raise big
burrs on even a quality HSS bit when the bit slips in the chuck under power.
So the part you were trying to turn is not very hard.
Even so, you saw how difficult it can be to turn or mill. Unless you have
modern production machines and tools that are made for hard turning, you're
going to find machining HSS to be nearly impossible, even when it's not
fully hard. If it's fully annealed, you can just do it. But machining it
hard, or somewhere in between (like drill bit shanks) is going to be very
difficult or impossible on flexible machine tools.
IIRC, there is a Jacobs chuck which is 3/16" which has a J0
Minimum Maximum Closed Length Open Length
Sleeve Diameter Hard Pin Grip Torque Runout
Model in mm in mm Mount Key in mm in mm
in mm Ft-lb Out Nm Out in mm
0 0.0135 0.000 0.156 4.000 0JT K0 1.450 36.800 1.100 27.900
0.850 21.600 2.00 2.71 0.004"@0.75" 0.10mm@19mm
O.K. This one is not quite as large as you would like -- only 0.156"
(4.000 mm), which is just below 5/32". This must be the one which I was
remembering. I had one of those and a 1/8" Albrecht which spent time on
a Cameron Micro Precision sensitive drill press.
I don't know, Ed, when I've needed to turn down a drill shank I've just
chucked the drill in my lathe and turned it down - I never noticed a
problem - I don't remember picking up any special tool, but I probably used
either brazed carbide or an Aloris BXA-16 that has the triangle inserts - I
would think that in these days everyone with a lathe, even a little one,
would have a few suitably sized carbides - they are often cheaper than HSS.
My lathe is not a "modern" one, though it is not an antique
(Logan/powermatic 12 inch).
Carbide is the right tool material, and if it's sharp, and if your drill
shank is properly annealed (partly, I guess, or given their first tempering
at a higher temperature, because they aren't dead soft), it's probably not a
problem if you're practiced at getting everything right. But a 3/16" bit is
going to limit the overhang, and the OP says his HSS cutoff blade wouldn't
touch it and that he broke the tip off a carbide bit trying to turn it.
He may need some more practice, or maybe the shank of the bit is too hard.
But cutting stuff like that on an old toolroom-sized lathe or a small
Chinese lathe is not a job for someone just getting started, IMO. I was
trying to emphasize the importance of rigidity. And if the HSS is fully
hardened, that's a hard-turning job for a modern lathe, also IMO.
Similar scenario here, it's a Cameron MD-70 (deep throat) drill press
with the Albrecht 1/8" chuck. It's converted to CNC with 12"x8" XY
travel. In terms of drilling it's far more useful than the other drill
presses and the mill I have here except for the capacity. Need to
drill and countersink fairly precisely over 1000 holes for #2 flat
head screws. The drilling is the easy part, however, a 3/16"
countersink is needed for the countersinking. As stated earlier,
Cameron was able to hand pick a 0JT Jacobs 5/32" chuck capable of
opening beyond 3/16" so should be good there as well. Another
alternative they offered (at nearly twice the price) was a 1/4" 1JT
chuck/spindle combo. Thanks!
An alternative is to let the Cameron drill the holes, then use a
piloted countersink in a Micro-Stop ball bearing cage to control
countersink depth on a manual drill press. These piloted countersinks
and MicroStop cages are used for countersink rivets for aircraft use, so
there should be something available with a small enough pilot.
At least the hole location would be pre-determined by the CNC
modified Cameron so you just slide the workpiece until the pilot goes in
Best of luck,
P.S. It is amazing how much the cost of those has gone up. I paid
$150.00 for one which had just been used to demonstrate around
the lab for one day, then the orders were placed (including by
our particular section), and I bought the demo unit for home.
(I knew that it had been used only for that one day, because I
helped unpack it and pull the heavy-duty staples from the box.
Right now I'm using the Cameron to drill the holes then use a drill-
point countersink (aka center drill) in the mill and use the mill's
depth stop for countersink depth. Was using a collar at first but that
mars the surface too much. It's after seeing how quick and effortless
the drill routine was, compared to the countersinking, that I decided
to CNC the countersinking as well. Will be using a six flute
Tell me about it, mine cost me an arm and a leg 5 years ago. They
probably cost two arms and two legs today. No complaints though,
they're accurate, fast enough and easy to convert to CNC. Use it
mostly to drill PCBs and solder paste stencils.
A center drill? What angle of countersink do you need -- or
does it not matter -- just chamfering of the holes?
The MicroStop countersink cages don't mar -- very good thrust
ball bearings to serve as the stop, a wide smooth flange, and they are
available with nylon or some other soft plastic face on the flange when
you really need freedom from marring.
I've got a couple of them -- one with a full circle flange, and
the other with a cutaway so the flange covers perhaps 190 degrees or so,
cut away flat to allow you to work close to a step. Both of mine came
from eBay auctions, with a mix of piloted and pilotless countersinks and
a few cutters designed to cut a rivet head flush to the metal. The
"stop" part of the "Micro-Stop" can be adjusted in steps of 0.001" to
select the depth which really works best for you. You can even use
them with a drill motor -- or an air drill motor and still not get
marring or distorted holes.
O.K. The six-flute ones (Severance, I presume) I find I get
more chatter-free operation if I bring the cutter into light contact
with the workpiece, then start the motor, and plunge to preset depth.
(Obviously not MicroStop there, since they don't have the six-flute
O.K. That is what I got it for, but I've used it for a lot of
other things, including making keys for a rack-mount disk drive housing
with six plug-in disk carriers which came from a hamfest -- but which
did not have the keys, which were needed to turn the disks on after
plugging in. Luckily, they were unlocked, so I was able to take out one
switch-lock, pick it to a half-way point, measure the depth of the pins
(4-pin barrel key) and then use the Cameron with an index head for a
Unimat to drill them with a tiny end mill to the proper depths.
Yes -- I know that is pretty close to milling with a drill
press, except that I had no side motion, just plunge so it worked well
Does yours have the 1" travel dial indicator to determine plunge