I was planning a project which calls for a simple milled t-slot in
some mild steel.
I don't have the cutter yet. What is the difference in a Woodruff and
Can a Woodruff cutter act as a T-slot cutter and vise versa?
Which cutter would have a dual purpose and be the most useful?
Thank you in advance for your help.
You're likely to discover that a T slot cutter is side cutting, whereas a
Woodruff cutter is not. Both can function in the same capacity. Woodruff
cutters don't have the ability to cut on their sides, but they are hollow
ground for relief, and can be stepped over and plunged to achieve slots of
A Woodruff cutter demands that the spindle be at a right angle to the cut,
otherwise there can be loading that isn't desirable. A T slot cutter will
cut in most any attitude, although proper head alignment is desirable.
I don't know that one is better than the other, although you may find one
has features that are more desirable for certain applications than the
other. Woodruff keys and keyways are expected to be held to a tight
tolerance, thus the lack of side cutting. T slots generally have a greater
tolerance, so if the cutter cuts slightly oversized, no big deal. Let
your need determine which would serve you best.
Many factors will play into the results you achieve, and the problems you
face. One of them is the size of the T slot, as well as the material you
intend to machine. Rigidity of the machines is also a huge factor. If
you have a large slot to machine and it's in steel, running a light duty
machine, you'd do well to rough the slot with an undersized cutter, one that
maybe is narrow in height and somewhat smaller than the full diameter (width
of the finished slot). Rough all of the features aside from the opening in
the slot, then take it to size. That can be useful in all cases, truth be
known. Be certain to lube the cutter well, although if you machine gray or
ductile iron, you likely will not need lubrication.
Steels of all kinds will demand more from the machine, and aluminum will
demand less. Do what you can to keep chips from accumulating in the cut.
Provide air if you have it available---to clear the cut. If you allow
chips to accumulate, you'll have grief.
The more area you have in contact with a cutter, the greater will be the
demand from the machine---in all ways. Minimize the amount of material that
is removed (per pass) and you'll lower the effort required. Opening the
straight portion of the T slot is a good way to eliminate a lot of material.
You can do that with an undersized end mill. Stop slightly short of
finished width and depth, then rough the T, leaving a few thou for a finish
cut. Go back and finish the slot with an end mill, then take your finish
cut(s) on the T with the cutter you chose to use.
Don't let the task intimidate you---take it easy and feel your way as you
go. Don't run the cutter beyond recommended surface speed, to avoid killing
the cutting edge-----especially if you run a carbon steel cutter.
Such cuts can go smoothly, or give you fits. Make sure you lock the saddle
and spindle when you take a cut with the table. Use good sense and you
shouldn't have trouble.
I've got the standard set of import qualtiy Woodruff cutters. Not a
fear here, 'cause I know that no way in hell would one of these cut a
T slot. Cutting the whole T in one pass ain't gonna work on any
machine a hobbyist owns. I hope these T cutters come in sets where the
top of the T gets wider so you could make several passes.
It does look like a job just asking to break cutters.
I've watched a t slot being cut in cast iron with a single point
cutter. slow feed and chonk chonk chonk chonk....
the centre slot had been cut and it was expanding out the ears of the
slot. did the cut in what appeared to be a single pass.
easiest way of overcoming a fear is to try it.
I feel blessed not ever having to do it! Now, I can just ask Tim (my
part-time machinist) if I need it done. In the six months I've had him,
he's done some stuff I never knew how to do or was even possible.
The Woodruff has cutting edges only on the circumference, and is
mostly good for cutting seats for Woodruff keys. It is tailored to cut
a recess for a specific thickness Woodruff key.
The T-slot cutter has alternate teeth cutting on the top or
bottom side (assuming a vertical shank) as well as the circumference. It
is designed to cut a T-slot a little thicker than the default T-nuts so
they slide freely.
I would not consider either to be dual purpose -- other than
perhaps finding a Woodruff cutter the right dimensions to use for
milling a long key slot for standard square keys.
As for "most useful" -- that depends on what you need at the
moment -- a T-slot or a Woodruff key seat. :-)
Sorry to not have good news for you.
[ ... ]
I had no problem the one time which I have cut a T-slot -- and
it was a circular T-slot at that.
I started with a two-flute end mill and cut the circular slot to
the desired depth, along with a short radial slot for entry, then
mounted the T-slot cutter, cut in from the edge to the proper radius and
around the workpiece following the original circular milled slot. I
used a small rotary table for workholding and motion for both
And all of this was done on an ancient horizontal mill -- which
actually helped clear chips somewhat compared to a vertical mill.
The main trick with the T-slot cutter is keeping a shop vac
close to it to pull out chips so they don't clog the slot as you form
T-slots are often cut in cast Iron, which usually cuts pretty nicely.
Also, the "chips" are nearly dust, and don't pack up much. I'd think
cutting T-slots in steel would be another matter entirely.