Wood Router, Snapping Cutters

[kingcreaky]

Hi All.

Just thought id offload one of those worries I have knocking round in my head. Its in regard to wood router cutters.

Something like this
http://www.mycncuk.com/attachment.php?attachmentid=15738&stc=1

I seem to go through them like hot dinners. and I wondered if anybody else has the same problem, or can perhaps advise me if I am missing something

Im using a standard 2.2kw chineese spindle, spinning at top wack 2200rpm? Ive checked its spinning in the right direction. all Im cutting is 3mm ply.

the workpeace is securely fixed down, and im only moving at around 2500mm/min @ around 4mm a pass

I seem to go through about one every hour, sometimes quicker. and at about £12 a pop its starting to take the biscuit

I even bought a couple of really expensive ones from ltc tooling http://www.itc-ltd.co.uk the guy said, he has never known one to break... my machine broke it in minutes

there doesnt appear to be any slop in the machine... (you can grab the neck of the spindle and hang on it, without feeling any play or movement)

any ideas, no matter how trivial they sound... would be appreciated. may have to post a video

in anticipation of your replies gents, thanks in advance

matt

[Ger21]

What diameter is the cutter, 6mm?

Drop your rpm to 13,000, and they should last longer.

Also, try using the shortest bit you can find. The longer it is, the more stress it will have on it.

[Clive S]

Im using a standard 2.2kw chineese spindle, spinning at top wack 2200rpm? Ive checked its spinning in the right direction. all Im cutting is 3mm ply.
Matt As Gerry has said drop your rpm down and feed rate up. 2500mm/min seems slow to me. Gwizard indicates with a 6mm 2 flute carbide slot cutting 4mm DOC 18450 rpm 7790 mm/min feed. rate

[cropwell]

Hi Matt,

Have a look at the cheap and cheerful cutters on toolstation http://www.toolstation.com/shop/Power+Tool+Accessories/d80/Router+Bits/sd2579/Router+Bit+Straight/p83429 (http://www.toolstation.com/shop/Power+Tool+Accessories/d80/Router+Bits/sd2579) they may not last any longer, but at the price the pain is lessened.

Cheers,

Rob

[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.
http://www.mycncuk.com/attachment.php?attachmentid=15739&stc=1

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? :unconscious:

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 . . .

[mike os]

what does it sound like when it cuts? i am wondering of your feed & speed are causing resonance in the cutter

[gorbo]

I use these cutters in Ply, hardwood and MDF, yes I have had some break ( I use 3mm single flute), but I found they cut better and broke less at a higher pass speed and lower RPM, I found at a low pass speed they over heated and snapped clean off, just a thought

[Tenson]

I just got some of the 1/8" (3mm) dia. single-flute cutters from toolstation for cutting 9mm birch ply. I'll let you know how it goes. http://www.toolstation.com/shop/p67412

Before these, I've been using 3mm 2-flute solid carbide. I've cut for hours on end with no problems. I've run 13000rpm and 2000mm/min and also 18000rpm and 4000mm/min. Both 4mm DOC. http://www.ebay.co.uk/itm/5Pcs-3-175mm-Round-Shank-17mm-Cutting-Length-2-Straight-Flute-End-Milling-Cutter-/361348864372?hash=item5422121974

However I wanted something with a thicker shank so I could extend it further out the collet for various reasons.

I've used spiral flutes but up-cutters leave a horrible finish on the top edge. Down-cutters make it difficult to leave a constant thickness skin on the bottom cut to maintain vacuum.

[gorbo]

I just got some of the 1/8" (3mm) dia. single-flute cutters from toolstation for cutting 9mm birch ply. I'll let you know how it goes. http://www.toolstation.com/shop/p67412

Before these, I've been using 3mm 2-flute solid carbide. I've cut for hours on end with no problems. I've run 13000rpm and 2000mm/min and also 18000rpm and 4000mm/min. Both 4mm DOC. http://www.ebay.co.uk/itm/5Pcs-3-175mm-Round-Shank-17mm-Cutting-Length-2-Straight-Flute-End-Milling-Cutter-/361348864372?hash=item5422121974

However I wanted something with a thicker shank so I could extend it further out the collet for various reasons.

I've used spiral flutes but up-cutters leave a horrible finish on the top edge. Down-cutters make it difficult to leave a constant thickness skin on the bottom cut to maintain vacuum.

I have brought some of those cutters too from Tool Station, see how long they last, I tend to use 3mm more than anything else

John

[Tenson]

Got some cutting on them today. I was about to post that they are working well and then SNAP!

I got about 2 hours continuous use on it. Birch ply @ 4.5mm DOC. Partly 2000mm/min at 16K RPM. Partly 4000mm/min at 20K RPM. Broke on a 4000mm/min 4.5mm DOC pass. Perhaps I'm asking too much of the little thing.

It worked well right to it's last breath. Cheap as chips so not too annoyed.

https://goo.gl/photos/KEqAuwNygLijbgoH7

https://goo.gl/photos/QNcDwZJaf82N3Lfm9

[Tenson]

I note however, that the red paint rubs off which means it is rubbing on the wood. This part of the cutter should be slightly under-sized so only the blade comes in contact with the wood. Perhaps this causes the heating and breakage? Maybe I'll sand it off first and see how long it lasts.

[gorbo]

I note however, that the red paint rubs off which means it is rubbing on the wood. This part of the cutter should be slightly under-sized so only the blade comes in contact with the wood. Perhaps this causes the heating and breakage? Maybe I'll sand it off first and see how long it lasts.


I would lower the DOC to 2mm and try again, you can`t expect top notch cutting from a cheap bit

[Tenson]

You are probably right but the job will take longer so I'll just throw cutters at it when they cost almost £1 each.

[Tenson]

To be fair GWizard suggests a DOC @ 2mm with 4000mm/min and 20K RPM.

[Jonathan]

Got some cutting on them today. I was about to post that they are working well and then SNAP!

I got about 2 hours continuous use on it.

I tried those a few years ago and they lasted both minutes ... so I guess you did better than me. The larger ones are not so bad though.

Personally I'd recommend single flute carbide cutters from aliexpress/eBay. The price is similar, they have more room for the chips and are stronger as purely carbide.

[Tenson]

Thanks Jonathan. Are you aware of any straight flute 3mm (or 1/8") solid carbide that have a 6mm shank? I need to extend them out the collet a bit to clear the dust shoe. It's asking a bit much of a 3mm shank.

Actually I think cutwell might have some so I'll pop over there for a look.

[Tenson]

Nice chips :)

https://goo.gl/photos/LM6BvaGZfuPFkc5L7

Cutwell do sell a 4mm dia. 6mm shank straight flue solid carbide cutter..... £23!!

http://www.cutwel.co.uk/routing/router-bits/single-flute-solid-carbide-straight-lmt-onsrud-61-400-series

[gorbo]

Tried those 3mm cheap bits today and they performed ok on Mahogany, no breakage yet

[Tenson]

I just bought another 9 of them. If you want a straight flute 3mm cutter with a 6mm shank I'm not sure there are many alternatives.

There are some similar ones on eBay with a shorter cutter length (7mm) which might last longer if you don't need a greater DOC.