Kickback protection in routers

[Windows]

Does anyone use a router with kickback protection? (Like the DeWALT DCW620B; are there others?) Is this an important feature?

I’m interested in the feature itself, but also considering - if there’s demand for this feature - whether Festool might be prompted to update their routers soon (due to this feature or others).

 

[9fingers]

Sounds like a gimmick to me.

 

[AJB Temple]

To Echo 9F, it's never crossed my mind. I've used routers for 30+ years and never had a kickback. I always lower the spinning cutter gently into the work, go slowly and the cutter speed is so high and feed rate so slow that a kickback seems unlikely? The only thing that has ever occurred is a Tungsten tip coming off a cutter and a Trend narrow cutter breaking. Not sure I would pay extra for kickback protection.

 

[Windows]

I hadn’t heard of this being an issue for routers, but I was aware that sudden torque in drills was an issue (and that Festool has kickback protection in some of its drills) and it didn’t seem outlandish that routers could see similar issues.

I guess it’s much more likely in drills than routers since they have to deal with such a wide range of materials. Coincidentally I just saw a video where someone was drilling a core through a stone wall and the bit got stuck and the drill smacked him in the face (no permanent damage in this case fortunately, but it had to hurt).

 

[RogerS]

I think it is down to torque. You need a lot more in a batery drill than you do in a router. My Milwaukee drill kicked back on me one day and nearly took my hand off. Never, ever had anything like that with a router.

 

[SamQ aka Ah! Q!]

Regrettably, when much younger (and greener, i.e. stupid) I did experience a router kickback. Thank any diety of your choice, it was not my DeWalt 625, but a skimpy, gutless B&D toy. It still hurt. 16,000 rpm, even if the cutter shaft is only quarter inch, is still a lot of kinetic energy.

I also have, somewhere, a tear sheet from the extinct "Router" magazine, where one of the professional contributors posted a picture of the impact crater 25 ft away on the wall from the router table where an attempt at creating at a moulding had gone irreversibly t.u. ....That was a half inch shaft, unforgiving triple gee-gee behemoth. Big Momma kickback.

I think we have all experienced 'bogging down', the precurser to kickback, but we've all had the wit to lift the router off, or release the plunge....hmmmm?? Common sense??

Therefore, I have mixed feelings about reading about a so-called "kickback protector". Will it inculcate a misplaced sense of complacency that 'the tool will automatically do the right thing'??

 

[Ovaloe]

I guess it’s much more likely in drills than routers since they have to deal with such a wide range of materials. Coincidentally I just saw a video where someone was drilling a core through a stone wall and the bit got stuck and the drill smacked him in the face (no permanent damage in this case fortunately, but it had to hurt).

That's why trade rated core drills need a good clutch, and why you shouln't ever exceed the maximum diameter of core bit specified by the manufacturer for your drill (my corded SDS is rated at a paltry 64mm). I know what you mean about hurt! Fortunately we are no longer in the days of the old massive Wolf (breast) drills which were notorious for their ability to snag and throw you off with remarkable ease, even at just 300rpm

 

[Trevanion]

I wouldn't have thought it to be a very popular feature as I can't see many scenarios where it could play a part in preventing an injury, kickbacks do occur on handheld routers but very rarely do they cause the router to "rotate excessively" out of the operators hands.

The only thing I can think of is that with it being a cordless tool DeWalt has the foresight to realise that people may use it in less than ideal conditions for work it may not be suited for and thus want to cover themselves by having the safety feature. People will pick it up because it's convenient to rout out a lot of material overhead and with an improper grip on the tool it catches on a knot and decides to throw itself out of the operators arms, it shuts itself off knowing that it's gone pear-shaped.

 

[Windows]

Indeed. My perception of dewalt as a brand is that they’re quite focused on American house building and renovation so perhaps they plan for their routers to encounter knots, nails, drywall fixings, electrical boxes, and so on. It’s surprising that the American market hasn’t pushed faster into safety features given litigation possibilities, but I guess litigation pressure is countered by weak worker protection laws.

 

[AJB Temple]

I wouldn't have thought it to be a very popular feature as I can't see many scenarios where it could play a part in preventing an injury, kickbacks do occur on handheld routers but very rarely do they cause the router to "rotate excessively" out of the operators hands.

The only thing I can think of is that with it being a cordless tool DeWalt has the foresight to realise that people may use it in less than ideal conditions for work it may not be suited for and thus want to cover themselves by having the safety feature. People will pick it up because it's convenient to rout out a lot of material overhead and with an improper grip on the tool it catches on a knot and decides to throw itself out of the operators arms, it shuts itself off knowing that it's gone pear-shaped.

That's a good point. I must admit I have always found routers to be a bit scary. Mainly because the rotation speed is very high and you have your head close. There is no way I would use it in any position other than straight down. That said I have seen first hand in the US a timber framer using a 16" hand held circular saw both vertically and above his head. The saw was a beast.

 

[Cabinetman]

I’ve given up commenting on dangerous practices I see over here, it’s almost seen as heroic and the more dangerous the better, everyone else (me) is a wuss and pathetic. But of course I just rise above it and it wouldn’t be nice to have the last laugh at someone else’s accident.

 

[Trevanion]

I must admit I have always found routers to be a bit scary.

The operator is always the most dangerous aspect, there are certainly tools with a higher frequency of accidents and injuries compared to others, however I will still maintain that it is entirely down to operator error.

A more common one recently I believe are small trim routers, especially when fitted with flush trimming bits and performing heavy cuts, the trim router is inexpensive when compared to full-sized 1/4" or 1/2" routers and can still fit 1/4" bits up to whatever will fit in the machine which makes them an attractive option for hobbyists who aren't trained and do not necessarily understand the risk. I have seen several people misuse these routers and they end up getting wrenched out of the operators hands when they do eventually "catch". There's a video on YouTube where the router comes out of the operators hands after it catches during feeding the bit the incorrect way, does a flip in the air and the cutter lands on the back of the operators hand, all in a split second. I suppose in this case if the router had "rotation detection" and had shut off perhaps the injury would have been lessened.

Here's the video if you want to see it, it's not particularly gruesome for the more squeamish members, it shows the accident at around 4:44.

 

[AJB Temple]

Well that fool with the router seems almost proud of it. He's got a tool running with a spinning blade poking out of the bottom and can't really see what he's doing and the work is loose on the bench. It's real Darwin award stuff.

I do actually have a trim router. It's a Stanley one with all metal body that screws down to set the depth of the bit. It came with two other routers I bought SH as a bundle from a guy on UKW I think. It was a big Hitachi that I actually wanted. I've never used the trim router as it struck me as an accident waiting to happen. If I have to do work like that I rig up a support to make sure the router can't tip over and I simply wouldn't do the kind of job he's doing without clamping the work down. But I know I am accident prone so I have to take steps to protect myself

 

[Ovaloe]

... so perhaps they plan for their routers to encounter knots, nails, drywall fixings, electrical boxes, and so on.

As someone who periodically has to push a router cutter through knots, nails (both wrought and modern hard steel), drywall screws, steel back boxes, etc (mostly unintended) all I can say is that even with a cordless 1/4in router such as the Makita DRT50 and a reasonably sharp cutter you rarely get much kickback - you're far more likely to experience it when using an over large cutter (for the size of the motor), a blunt cutter or perhaps more commonly when climb milling. Of these the latter is the most dangerous as it can leave you with a zipper pattern up the front of your sweat shirt (or worse).

I always find "trim router" to be a bit misleading - the original laminate trimmers were single speed, one-handed tools intended to trim overhanging laminate. In that scenario one-handed use is OK because the forces acting on the router aren't huge. Use a small round over or chamfer cutter and it really isn't much worse. What makes them an accident waiting to happen is when you strap on a large cutter and attempt to use the them single-handed - but that's why manufacturers sell two handled plunge bases, isn't it?

Not sure of the practicality or necessity of DW's new a feature if you switch brain on before inserting cutter, especially given that we've had corded routers without such features for more than 100 years. In any case it's really just something else to fail in due course..

 

[meccarroll]

It sounds like the comments in this thread have pretty much covered any problems assiciated with a router including possible kickback so no need for me to comment further on the subject.

One interesting thing I have learnt since using a CNC router machine is that using the correct feed and speed is really a must to cutter life and quality of finish. When using a hand held router I used to think turning up the speed to the maximum and going slow would achieve the best results but it doesn't all that happens is you create dust and very quickly burn out the cutter. I am not sure if anyone has found the best speed/feed for whan cutting laminated worktops with a handheld router but it would be interesting to hear if there is one.

 

[Trevanion]

One interesting thing I have learnt since using a CNC router machine is that using the correct feed and speed is really a must to cutter life and quality of finish. When using a hand held router I used to think turning up the speed to the maximum and going slow would achieve the best results but it doesn't all that happens is you create dust and very quickly burn out the cutter. I am not sure if anyone has found the best speed/feed for whan cutting laminated worktops with a handheld router but it would be interesting to hear if there is one.

Friction is the enemy of all sharp edges. Traditionally, this would have been worked out as how many "cut marks to the inch" you had for a given cut taking into account feed rate and RPM of the cutter, it was generally accepted with planing machines that somewhere around 20-25 cuts to the inch was about the best before you had diminishing returns in the lifespan of your knives but with routers this is practically impossible to achieve because of the speed of the bit. I personally think that 40-50 cut marks to the inch is better for moulding work to achieve a crisp profile.

A 25mm two-cutter bit spinning at 24,000RPM will engage the work 800 times in a second between the two cutters, and the rim speed will be in the region of 70MPH. A 125mm four-cutter spindle moulder rebate block spinning at 4800RPM will engage the work 320 times in a second between the four cutters, and the rim speed of the block will also be in the region of 70MPH. For the router to achieve 50 cuts to the inch you would be required to feed the work at 80 feet a minute, whereas with the rebate block you would need to feed it at 32 feet a minute.

Aside from the contact with the timber itself causing a dulling effect on the cutters, because the router bit is engaging with the work twice as often as the rebate block it is generating twice the friction and has more of a propensity to burn the work, particularly at slower feed rates, this also drastically reduces the lifespan of the cutters.

 

[duke]

Hand held routers can get out of control easily as already mentioned. When I use them I tend to be really focused with the task at hand.
Have experienced minor kick back but that was due to me not easing the cutter onto the cut and knowing how the cutters react to different woods helps. I usually do test cuts on scraps first.

 

[Ovaloe]

When using a hand held router I used to think turning up the speed to the maximum and going slow would achieve the best results but it doesn't all that happens is you create dust and very quickly burn out the cutter. I am not sure if anyone has found the best speed/feed for whan cutting laminated worktops with a handheld router but it would be interesting to hear if there is one.

If by "laminated worktop" you mean HPL (or solid high pressure laminate), then you are into a whole different field. Softer plastics require the spindle speed to be reduced, often to 12k to 15k (assuming a hand held router with a standard 1/2in diameter 2-flute straight cutter), whilst the feed rate is increased as much as possible. The bigger the motor the better TBH. Harder plastics, such a phenolics, can be cut at slightly higher spindle speeds, but fed equally quickly. The idea is to create a stream of curled chips as opposed to dust

I personally won't tackle HPL or post formed laminate tops with anything less than 2000 watts of 1/2in router. Good dust extraction helps to keep the cutter cooler by reducing chip churn in the gullets. Solid upcut carbide spiral cutters do take less power, but require greater collet clamping pressure to avoid them being pulled out of the collet - so your collet needs to be in good order. Another downside is that they don't tolerate metalic or calcified inclusions in the chipboard core (if that is what you are cutting) chipping very badly if contact is made

Larger diameter cutters have more metal in them and bigger gullets, so the do run cooler - mainly a CNC thing, though.

On standard laminated chipboard worktops I've found that replaceable tip carbide cutters produce the best results - typically deWalt DWE625, 1/2in TC-RT @ circa 16 to 18k rpm, 3 incremental depth passes on the "off" side of the jig followed by a full depth cut (i.e. a 0.5 to 1mm cut) on the good side

As it happens any softer more deformable plastics such as nylon 66 or UHMW (aka high density polyethylene) benefit from making a flrst pass at 0.5 to 1mm oversize, conventional cut, followed by a final size cut at high feed, reduced spindle speed, but using a climb cut. So not for the router beginner and best performed on a CNC!

 

[SamQ aka Ah! Q!]

Trevanion and Ovaloe? What a cracking pair of replies! It is so good to see properly contextualised, informed reasoning instead of the usual 'foaming at the keyboard' inflicted upon us by so many digerati. Shame on them.

 

[meccarroll]

If by "laminated worktop" you mean HPL (or solid high pressure laminate), then you are into a whole different field. Softer plastics require the spindle speed to be reduced, often to 12k to 15k (assuming a hand held router with a standard 1/2in diameter 2-flute straight cutter), whilst the feed rate is increased as much as possible. The bigger the motor the better TBH. Harder plastics, such a phenolics, can be cut at slightly higher spindle speeds, but fed equally quickly. The idea is to create a stream of curled chips as opposed to dust

I personally won't tackle HPL or post formed laminate tops with anything less than 2000 watts of 1/2in router. Good dust extraction helps to keep the cutter cooler by reducing chip churn in the gullets. Solid upcut carbide spiral cutters do take less power, but require greater collet clamping pressure to avoid them being pulled out of the collet - so your collet needs to be in good order. Another downside is that they don't tolerate metalic or calcified inclusions in the chipboard core (if that is what you are cutting) chipping very badly if contact is made

Larger diameter cutters have more metal in them and bigger gullets, so the do run cooler - mainly a CNC thing, though.

On standard laminated chipboard worktops I've found that replaceable tip carbide cutters produce the best results - typically deWalt DWE625, 1/2in TC-RT @ circa 16 to 18k rpm, 3 incremental depth passes on the "off" side of the jig followed by a full depth cut (i.e. a 0.5 to 1mm cut) on the good side

As it happens any softer more deformable plastics such as nylon 66 or UHMW (aka high density polyethylene) benefit from making a flrst pass at 0.5 to 1mm oversize, conventional cut, followed by a final size cut at high feed, reduced spindle speed, but using a climb cut. So not for the router beginner and best performed on a CNC!

Yes that's what I was looking for in an answer. I tend to use a speed of 14000 to 18000 rpm but mainly around 14000 rpm which seems to coincide somewhat with what you have written. I have some worktops coming up so will follow your advice. I am starting to learn that creating chips and not dust is the way to lean. Many thanks.

 

[meccarroll]

Friction is the enemy of all sharp edges. Traditionally, this would have been worked out as how many "cut marks to the inch" you had for a given cut taking into account feed rate and RPM of the cutter, it was generally accepted with planing machines that somewhere around 20-25 cuts to the inch was about the best before you had diminishing returns in the lifespan of your knives but with routers this is practically impossible to achieve because of the speed of the bit. I personally think that 40-50 cut marks to the inch is better for moulding work to achieve a crisp profile.

A 25mm two-cutter bit spinning at 24,000RPM will engage the work 800 times in a second between the two cutters, and the rim speed will be in the region of 70MPH. A 125mm four-cutter spindle moulder rebate block spinning at 4800RPM will engage the work 320 times in a second between the four cutters, and the rim speed of the block will also be in the region of 70MPH. For the router to achieve 50 cuts to the inch you would be required to feed the work at 80 feet a minute, whereas with the rebate block you would need to feed it at 32 feet a minute.

Aside from the contact with the timber itself causing a dulling effect on the cutters, because the router bit is engaging with the work twice as often as the rebate block it is generating twice the friction and has more of a propensity to burn the work, particularly at slower feed rates, this also drastically reduces the lifespan of the cutters.

A lot of information which you have spent a lot of time to produce which is very informative and much appreciated. Thank you...It reminds me of when I was at college on my City & Guilds.