Thread: Which bit for cutting router insert hole

Hi kalium,

I've used a 6mm straight bit quite often and have never had one snap yet. (they were 1/4 inch shank)

I've used Econo-cut branded bits (cheap range of router bits made by Carbi-tool) and they went dull but never broke. For most of my work, Carbi-tool is my router bit of choice.

Maybe you were trying to take too much material from each pass, 6mm is quite a small bit.

When i'm routing using a template, I try to rough cut with a jigsaw close to the mark out lines and leave only a couple of millimeters for the router bit to clean up, and then move the router slowly while making the cut. This way you dont over-work the router and your bits last longer. Bigger bits help too.

Hope this helps you out a bit.

Steven.

Some of the small cheap router bits can be quite fragile. As a rule of thumb, the depth of cut should be no more than half the diameter of the bit.

Originally Posted by kalium

I don't have many bits yet (and yes, I have plans to buy a good quality 1/2" set soon), but decided to pick an 1/4" el cheapo (Aldi) 6mm straight bit for the job that I had lying around. It pretty much snapped straight away.

1. Dont buy tools from Aldi

2. Whether you buy tools from Aldi or not, dont put too much strain on router bits. They arent made to cut the full depth in one go particularly if you are plunging them into a solid piece. Only use the full depth of the bit if you are taking a small amount off the side of a piece either by following a template or using a fence handheld or in a table.

3. use 1/2" shanks where possible.1/4' bits are getting better but I still rather 1/2" bits where I can.

4. Stay well clear of sets of 10 or more router bits that cost less than two decent brand bits.

MDF is a bugger to cut. No matter what the tool, there's something about the open porous nature of the material that seems to instantly clog the gullets of many cutting tools.

You probably noticed, before your breakage, some smoke & burning/blackening. That's friction from the MDF fibres rubbing against each other. I'm guessing it's this heat that destroyed your bit's temper. A bigger diameter bit, in TCT running at a lower speed would help to reduce this clogging & heat build up.

It drills ok. Slower speeds I suppose & deep spiral relief. But if you try to use a holesaw there's nowhere for the swarf to go, it instantly clogs, blackens & if you aren't careful there goes the temper of the teeth. I used to need to cut a lot of holes in the stuff for electrical installations. For smaller holes, an auger or a spadebit (slowly rocked and twisted to clear the swarf) works well, but for holes bigger than 35mm I found it best to resort to a pilot hole & slow jigsaw, the coarser toothed the better.

Don't know anything at all about cheap router bits either. I've only ever really used Carb-i-tool ones. While not exactly "expensive" these days, I do remember buying a matched pair of cabinet door cutters, without even a bearing on either, that cost the equivalent of a fortnight's wages in the late 70s.

Smaller Carb-i-tool bits < their respective shank size tend to be milled from solid carbide, which stands up to heat much better than TCT or HSS. They should be regarded as disposable, as the cutting edge (often single) is simply lost in the sharpening if you try.

If you drill & glue a simple, slender wooden handle over the old cutting end, the shanks make a superb zero cost burnishing tool for scrapers and the like.

Originally Posted by Ratbag

If you drill & glue a simple, slender wooden handle over the old cutting end, the shanks make a superb zero cost burnishing tool for scrapers and the like.

Good idea, hadn't thought of that one

Cheers

Doug

Thanks for the helpful replies. I will not expect so much of a 6mm bit in the future (especially an Aldi one). And yes, there was a whole bunch of smoke before the bit snapped. A lesson learnt

I went out and bought myself a 1/2" shank Diablo flush trim bit (The best quality one I could get on a days notice). I reset my template to be flush with the hole I wanted to cut out, turned the table upside down and cut the hole out in one pass with the bearing being guided by the template underneath. It worked fine.

I went on to cut out the rebates for my Rosseau insert plate and it now snugly fits and has given a new lease of life to the old table.

Too late now, but any time you're doing through cuts with a pattern bit, it's generally best to remove as much material as possible by some other means first. For example if you were cutting a hole for a router plate, you would fix the template in position and then remove the bulk with a jig saw or something first, then trim to shape. Taking a full depth, full diameter cut in 19mm MDF with even a 1/2" router bit is not "best practice". It puts a lot of strain on the router and the bit.

Originally Posted by silentC

Too late now, but any time you're doing through cuts with a pattern bit, it's generally best to remove as much material as possible by some other means first. For example if you were cutting a hole for a router plate, you would fix the template in position and then remove the bulk with a jig saw or something first, then trim to shape. Taking a full depth, full diameter cut in 19mm MDF with even a 1/2" router bit is not "best practice". It puts a lot of strain on the router and the bit.

Gotcha. I am actually planning on making another router table (this one is just a stand in and sags a bit), so will definitely use a jigsaw for the hard stuff and save my router.