Wood Router, Snapping Cutters

[Earle]

As you are breaking so many you may be able to answer this - are the bits breaking when you plunge into the wood or as its cutting along a length?

The reason I ask is that the cutter does not have a cutting edge all the way along the bottom edge, so if you are plunging vertically into the wood as opposed to a ramp effect you may be putting loads of force onto the cutter! anyway that's my experience with that type of cutter.


Earle

[mitchejc]

Hi Matt, below are just two examples of the same problem you have. I even tried to go with 6mm with a 1/2" shank and that broke just as easy and trust me these on the photo were not the only two I broke:-) I even managed to break a quite expensive WP 1/4" x 1/2 shank cutter, it lasted a longer but not much. Unless I ran these 6mm straight flute cutters with air blast, at low feed and shallow depth of cut they broke long before they get remotely blunt. They break while slotting straight or curved sections and never broke during a plunge or ramp-in. If I want to break a brand new one within 10 seconds I just cut some of those dark brown HD fibre board at the feed/speed/DOC you mentioned above. Gmmf, they die so gracefully, no real nasty sounds, nothing gets flung across the workshop, the spindle just leaves half the cutter behind in the slot... :-)

Earl has a point, not all of these straight flutes can plunge straight down. I normally bought the ones that can plunge but it did not make much of a difference in the results I got, nether did changing brands.

I don't know but I think its got to do with limited chip clearance or something. I'm not saying this type of cutter is junk but I for one, had no luck with them in 6mm. The larger ones like 1/2" x 1/2" straight flute cutters never breaks and lasts till they are blunt but they also don't like aggressive cut depths while slotting, in my experience. On the larger diameter ones it takes quite a but if cutting force at more aggressive DOC. Try one in a hand router and you'll understand what I mean.

For 6mm dia go for single flute or even two flute spiral cutters and you will have MUCH more joy, faster feeds and you'll cut them till they are properly blunt without breaking and you'll save money.


I would be curious to know if other CNC'ers are using these straight flute 6mm cutters at reasonable feed/speed/DOC with success in ply or harder types of wood.

[Robin Hewitt]

You would think it was inability to clear swarf, but that is not really a possibility in 3mm ply.

Next favourite is a build up of gunge that dulls the edge so it stops cutting and starts bending.

Perhaps it is the material. Is the glue in the plywood transferring to the cutting edges?

[Boyan Silyavski]

Hey Matt,

Try the classical 16000rpm feed 60IPM 1 diameter cut depth. 17000rpm for harder wood. Thats a speed feed depth combo that must work on any machine even a crappy one. Works even on chattering machine and i use the similar cutters until they stop cutting at all.


Its spinning on the right or correct direction?

Do you climb cut or conventional? I climb cut natural and conventional cut man made wood.

[Clive S]

Boyan In post one the op has said it is cutting in the correct direction. If the feed rate is too low that could gum the cutter up

[Boyan Silyavski]

Boyan In post one the op has said it is cutting in the correct direction. If the feed rate is too low that could gum the cutter up

The rate i suggest will not clog the cutter, rest assured Clive. I am cutting same on flimsy machine all day long for 2-3 days until i waste a cutter. He is not cutting with 200$ cutters, big spindle and perfect hold down to go industrial fast like 400IPM. I am just suggesting to try that and see if that still happens.

[routercnc]

I was cutting a load of 25mm MDF a while ago with a 6mm cutter like the one in the first post. About £3-£4 I think on eBay. I broke one about every hour or so until I swapped to an 8mm cutter and had no problems. The 6mm bits have that tapered section and this is exactly where they broke. The 8mm bits don't have that and the main body is straight with the cutting bits sticking out welded to the sides. Without that stress raiser that seems to make them more durable and with the thicker body they probably vibrate less. Worked for me . . .