Was i being greedy? - router table advice

[fezman]

On Sunday i used my Trend T11 router in the CRT Mk3 router table with a 6.3mm twin flute straight bit from the trend starter set. The aim being to cut a 5mm dado in some ABW.

I managed about 13cm in length before the bit snapped at the bottom of the flutes.

I emailed Trend indicating I wasn't happy about the bit failing after so little use, their customer service was fantastic - replied Monday morning and dispatched a new bit which arrived this morning. I setup the router in exactly the same way (bit in the collett at least to the marked line), started routing the remainder of the pieces, and the new bit snapped in exactly the same place after less than 10cm of the passes.

I was very careful about the feed rate and took it very slowly. So my question is: Was i being greedy at trying to take all of the 5mm in one bite, or are the starter set bits not up to much? Would other forum members expect to be able to rout a 5mm x 6.3mm dado in one pass?

At the same time i took the advice of many members on here to purchase a similar bit from Wealden Tools. again service was first class - ordered late Sunday night, delivered today. This one being the solid carbide bit.
After the 2nd trend bit failed i tried the Wealden, but fear (or sense) got the better of me - i took the remaining passes in 2.5 mm depths. This worked flawlessly and I have to say the finish on these cuts is far superior to the trend bits. The bit seemed to pull the work through and seemed effortless. Does 2.5mm make that much difference or is it the difference in quality of bit.
thanks
Ian

 

[JWD]

Hi Ian

5mm doesn't seem like an aggressive cut in wood - but perhaps in a dense brittle polymer you might be pushing it, especially without a specialised bit! I seem to remember being told polymers more readily dull blades...

 

[fezman]

Hi Ian

5mm doesn't seem like an aggressive cut in wood - but perhaps in a dense brittle polymer you might be pushing it, especially without a specialised bit! I seem to remember being told polymers more readily dull blades...

Hi JWD

ABW = American Black Walnut - didnt go anywhere near polymers.

 

[Phil Pascoe]

5mm certainly isn't excessive although it could be cleaner with a small router to take two passes. You were using it at full speed?

 

[custard]

I'd definitely cut that in a single pass.

One thought, you might actually have been going too slowly. The cutter is cooled by moving into fresh timber, if you go too slowly the bit overheats and becomes blunt almost immediately, which then makes it vulnerable to snapping , this is especially true for cheap tooling which generally speaking isn't all that sharp to begin with.

 

[fezman]

Thanks Phil and Custard
Yes the router was at full speed.

I would never have known about the timber cooling the bit Custard, I would have thought going faster / too fast would cause the issue. i.e. was i exerting too much lateral pressure on the bit.

I have to say the wealden solid carbide bit seems much more robust - i'll give it another whirl later in the week at a faster feed rate and see if it copes.

 

[Mike Jordan]

I've had experience of this size of cutter breaking off at the base of the TC inserts with very little use or abuse. The solid carbide type have been very good and have been hard used. I also have a couple of single flute solid carbide cutters which I bought in the hope that they would be more durable. They have been very good but do make much more noise in use.

 

[Phil Pascoe]

How big a cut is possible, I hear you ask? Not recommended, but ages ago I tried a 36mm x 36mm Wealden straight cutter into softwood in one pass. It did it ..........not pretty or easy but it did it. :shock:

edit - hand held, not in a table.

 

[Geoff_S]

Just a thought, how far was the cutter shank sitting outside the collett?

I don't want to sound like "YOU DIDN'T WANT TO DO THAT", but I would have started the depth at 1/2 the cutter diameter, so about 3mm in this case and see what
it felt like. It was just a rule of thumb that I was told back in the mists of time on a router course I went on.

 

[PAC1]

How far was the shank in the collet. Trend usually have a insert line.

 

[Phil Pascoe]

Just a thought, how far was the cutter shank sitting outside the collett?

surely that's neither here nor there to where the things broke?

 

[julianf]

With a fulcrum long enough... The moment presented is greater. That said, I spend my life milling non ferrous, and it's normally "an event" that snaps bits, rather than just excessive protrusion.

 

[PAC1]

Phil, it will make a difference as the further out the more vibration and stress on the cutter.

 

[Geoff_S]

Just a thought, how far was the cutter shank sitting outside the collett?

surely that's neither here nor there to where the things broke?

It was illustrated to me by holding a pencil.

Grab a normal length pencil by the fist with just the tip protruding. Now try to wiggle the pencil by the tip. Little movement.

Now grab the pencil at the end and now wiggle the tip. Lots of movement.

Not very scientific, I know, but the guy who taught me just happened to have a pencil available. The longer the unsupported length the more
opportunity there is for movement and potential breakage.

 

[Geoff_S]

Hi Ian

5mm doesn't seem like an aggressive cut in wood - but perhaps in a dense brittle polymer you might be pushing it, especially without a specialised bit! I seem to remember being told polymers more readily dull blades...

Hi JWD

ABW = American Black Walnut - didnt go anywhere near polymers.

Oh. I am just coming to the end of a large ABW job, about 400+ metres that has been profiled, grooved and cut, many many times.

What was interesting to me was that lugging the planks backwards and forwards, just how variable the weights were of identical lengths. Also, when cutting or routing again, just
how variable the pieces could be in terms of pressure required. I'm having a coffee break right now having just cut the last (I hope) piece of skirting and funnily enough that
piece was noticeably tougher to cut than the previous couple of days of cutting.

So, could the ABW be another variable in this?

 

[Racers]

I had the same thing happen to me with some cheap 1/4" bits, I now have a solid carbide slot drill and it just won't blunt.

Its like this one.

https://www.ebay.co.uk/itm/1-4-6-35mm-S ... SwmmxW4We-

Pete

 

[fezman]

Phil, it will make a difference as the further out the more vibration and stress on the cutter.

All a little immaterial - as per my OP, the shank was fully inserted into the collet.

So, could the ABW be another variable in this?

While there could be some minor variation, all from the same board, about 2' long.

I had the same thing happen to me with some cheap 1/4" bits, I now have a solid carbide slot drill and it just won't blunt.

Pete

The wealden solid carbide bit did feel much better and provided a much cleaner cut. I will do a test later in the week (travelling around a bit for work for the rest of the week) to directly compare the Wealden bit cutting 5mm deep at same feed rate in a piece from the same board. Will let you all know.

 

[Bodgers]

I'd definitely cut that in a single pass.

One thought, you might actually have been going too slowly. The cutter is cooled by moving into fresh timber, if you go too slowly the bit overheats and becomes blunt almost immediately, which then makes it vulnerable to snapping , this is especially true for cheap tooling which generally speaking isn't all that sharp to begin with.

Also made worse if the bit is burried in the wood and you have poor or no dust collection as the chips build up, making the bit work harder.

How's the dust collection Fezman?

 

[fezman]

The dust collection was via the CRT standard exhaust port to a RP DX1000