Thread: What is this effect?

How much material are you trying to remove in one hit?

What is the brand of the bit?

"There's no discernable play in the router bearings and the bit still looks sharp."

There should be no play at all in the bearing - up/down or sideways.
Looks sharp?? - I presume you mean no nicks or burrs but this does not necessarily mean that the bit is sharp. El-cheapo bits are not really known for their sharpness or longevity. Not sure what you mean by "cutting on the upcut (?)" - there is an accepted direction for using a router - easiest is to get a diagram from google - there are times when it is necessary to reverse this accepted direction but I do not recall seeing the same result as your pix.

From the look of your pix I'd be leaning towards possibly trying to take off too much, possibly too fast. I don't think it is a grain issue but it a little difficult for me to tell from your pix.

Not sure if it helps,
Regards,
Bob

It's a woodrat bit, HSS and they are supposed to be decent quality.
WoodRat Australia: WR-H-S-50-10

I was taking off 9mm, 14mm deep at a rate of 30cm/40sec maybe?

I don't know how quickly quality HSS blunts but if that's the issue after only a little work in pine then I'm a bit disappointed. Still, I need to figure out what is involved in sharpening them myself.

I would suggest you are biting off more than the bit can chew.

Try with a smaller cut - in both directions.

I would agree with artme.

Too much at the one time.

Make multiple passes ie light cuts both for depth and width - work it both ways so that you have perhaps 0.5 ->1mm left for a very light "clean-up" cut. Practice your speed on some scrap - listen to the machine - the pitch should remain fairly constant - go too slow and the bits will scorch the timber.

I can't comment on the quality of Woodrat bits as I don't have any - but at least they are branded which means you can contact them and ask questions.

9mm x 14mm in one go using a HSS bit is making the bit and machine work quite hard - as a general rule Tungsten Carbide bits stay sharper longer.

I personally do not sharpen my bits - I send them to a tool sharpening service who have the gear and knowledge to do it properly. You could "touch-up" an edge using a diamond plate, just make sure that you lap the cutting edge the same number of times using the same pressure on both sides of the cutter - balance is important - also remember that sharpening will also change the diameter of a bit.

Hope it helps, regards,
Bob

Hi Bitslong,

yes, it's definitely no clean cut. Part of the wood has been torn off instead of having been cut cleanly. A second "smoothing" pass could remedy this. If it doesn't, your bit obviously isn't as sharp as it looks. Tungsten carbide tipped bits are not really necessary in pine; if there isn't too much resin in the wood and the temperature doesn't rise too high, ordinary hi speed steel bits will last a long time in soft wood.

I looked up the Woodrat bit number from the link you gave. It's a long straight two-edged bit with 10 mms diameter. This type is mostly used for making grooves, in which case every pass can get rids or 5 mms depth. A 10 mm diameter bit is too thin to shave of a 9 mm rebate in one go. It's just not ideally suited for such a task. You will probably have noticed that much of the wood has split off or splintered away, just forward of the advancing bit. That means there are a lot of unpredictable sideway forces between the cutting edges and the material. In such cases the bit may even bounce around a bit against the wood (noticeable as a coarse instead of a clean "planer" sound and visible as a rough result).
You would need a larger diameter bit for a rebate of that width, like 16 to 22 mms or so. The router will also behave steadier then, but also needs to be stronger due to the larger torque needed for the larger diameter, just like a 115 mms angle grinder will struggle with a 180 mms disc. To cut away 9 mm times 14 mm in pine, with a bit of 16 to 22 mm diameter, 1200 Watts input power would be more than enough with the forward pace you mentioned. More power is better, less will struggle. As for proper speed under load : three quarters of no-load rpm can be maintained continuously by even the cheapest of routers. If you're a bit musical, you can judge the amount of rpm-drop by the tone, since routers have no rpm-gauge. Listen to the machine at full idle rpm as try to remember the tone pitch. Three quarters of no-load pm will sound about half an octave lower. One octave lower equals an rpm-drop by 50%, only the best routers can survive that load contunuously, since at 50% rpm drop the cooling fan yield will have dropped to 25% of the airstream volume at no-load rpm.

Should you want to stick with this bit, try to shave off 3 mms at one pass. If the bit is sharp and the pace is steady and not too hasty, the cutting sound and the finish should be clean, too.

regards

gerhard