Hello all..............Help! I went to Rockler and bought a brand new
carbide coated 1/2 inch straight bit. Set up my router table with a 1
1/2 HP Skil plunge router. So far so good! Test cuts were ok .....all
seemed copacetic! I needed to groove 3/8 inch deep for 32 inches on
each of the four legs. I figured 3/16th's per pass would work. Take it
slow don't overload. Well about fifteen inches into the cut, the whole
world broke loose. Cacophony, screeching , rattling. I shut down just
in time to see the bit twirl out of the collet. I know I had it in
there real snug! After a few choice #&*@#'s, I regrouped and looked at
the gouge in the nice mahogany leg. Whew!,I can salvage
it............... Ok Regroup. I switched routers and put the old
Craftsman 1HP in the table. Mind you, I never had a problem with this
collet before in many years of service. Got it all set up again and
was sure all was ready. Bravely started the grooving again. Seemed ok
and then same thing, only not so bad. I aborted quicker this time.
After resetting depth, tightening collet again, going slow, clearing
chips, and so on, I finally got the job done. Badly..... but done.
What the hell went wrong? Are the 1/4 bits, such as this one, just too
stressed to function? Should I have made three passes? I now know I
must upgrade routers and get a 1/2 inch collet model with more HP, but
I would like to know the dynamics if anyone has an idea. Woodworking
isn't meant to be this much fun is it? Also any advice on which model
router might give me the least grief would be appreciated! Thanks so
Make sure you are putting the bit ALL the way into the collect, there
is typically a radiused area right at the base of the cutter that can
prevent you getting a good grip on the shaft, instead you tighten on
the radius, and as you cut it works up and all hell breaks loose
Some folks drop a fat 1/2 od Oring in to keep the router bit from
bottoming out and causing this
Otherwise, make SURE the router bit is NOT seated flush to the
collect, but rather give your self 3/16in space between the base of
the cutter portion and the top of the collet
With router tables it is very easy to just drop the bit all the way
into the collet and that leads to trouble
On 21 Jul 2004 20:27:59 -0700, firstname.lastname@example.org (mrmortise) wrote:
OK, he's a 1/4" shank, which I believe is most of the problem, compounded by
perhaps a bit of side pressure as the bit has both sides in the cut. For
this kind of cut I really favor the type of bit where the cutters protrude a
bit past the bottom of the steel or my spiral upcut.
The cut depth is a bit ambitious for a 1/4 inch shank, the bit is in contact
on both cutters, and the bottom of the cut is packing with dust. With all
that random load and vibration, sounds like a setup.
Think of how much more surface you have to grip at 1/2" and get a nice 1/2
capable router or collet for the Skill, if available.
I've got a couple of 1/2 inch router bits in two pieces (shank and
cutting head) in a box in the shop to remind me 1/4 inch shanks aren't
the way to go. Doesn't take much to overstress that 1/4 inch shank and
if it starts to run a little eccentric... you know the rest. You can do
a lot of work with one but you've got to take VERY small cuts and feed
gently, listening to the pitch of the motor. Get a router with 1/2 inch
collet. Life will be better.
I do a /lot/ of routing in my shop with a 5HP spindle. I
routinely make cuts three times as deep as the bit diameter at
feed rates varying between 1.25 and 2.00 inches/second at spindle
speeds of 18-22,000 RPM in wood, MDF, plywood, and plastic.
I normally work with 1/8", 1/4", and 1/2" bits. I've only /ever/
broken one bit - and that was by feeding too *slowly*.
When that happened, I did some digging to find out why: the wood
chips are the primary vehicle for removing the heat generated in
the cut. By feeding too slowly, I was increasing the amount of
heat generated per inch of cut and was decreasing the amount of
chips to carry that heat away.
I don't /know/ that this was your problem; but I'd like to point
out that reducing feed rate isn't necessarily the solution to
your problem - and a too slow feed may be a major contributor to
the unsatisfactory behavior.
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