Grooving............On a Wednesday Afternoon! Router Problem!

[mrmortise]

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 much! Michael

[John]

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

John

[bridger]

the bit shank may be a few thousandths too big or too small....

[George]

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.

[Robert Galloway]

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.

rhg

mrmortise wrote:

[Morris Dovey]

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.