Router Work Creating Smoke and Cinders

[npr_geek 3]

On two recent occasions, once with my handheld router, and once with a new router table I just built, I've been seeing some disconcerting burning while using a 1/2" straight cut bit. In both cases, I'm obviously concerned about potential fire, but in particular, I'm concerned about embers getting sucked into my dust collector and igniting the ready source of tinder in there and becoming a much larger fire. 

Any help would be appreciated. I read somewhere it could be as simple as needing to clean my bit. Clearly I should also be aware about not trying to cut too deeply on each pass. Either way, what's your experience with fire danger? My router dust collection is a shop vac with a Dusty Deputy. 

Thanks in advance for your input. 

[krtwood 541]

What kind of cuts were you doing and how much burning?  A little burning on woods like maple and cherry is hard to avoid, but not to point of making smoke.  Moving the work too slow for the speed of the cutter is what causes burning.  You either need to be moving the work faster or lower the rpms of the router, or both.  Also if you were trying to plunge with a straight bit that isn't designed for plunging that can cause some issues.  

[curlyoak 710]

What krtwood said. Sometimes the desired rout is too much on one pass. I like to remove about 75% on the first pass if I have the power for it. Then i can move fast on the second cut which eliminates the burn. Lets see you bit. It could be dull or broken. Got a picture?

[pkinneb 3360]

Burning to the point of embers? Really? Are you thinking this or have you actually seen burning embers? I find it really hard to imagine burning embers in any type of router situation

[npr_geek 3]

I was plunging in the handheld mode, and possibly too deeply in one pass. This was into plywood while I was making channels for my router table fence. The second time was on the table itself, not plunging, but cutting 3/16" dados along the fence, also into plywood. Since the table is a new setup and I'm using a small dewalt router (DWP611 1.25 HP) maybe I need to be adjusting the rpms, because my feed rate was pretty smooth. I washed the bit last night and have not tried this again, but I'll take a picture tonight and post. Also possible it's dull, but I haven't really used it much as I'm fairly novice with routers. 

My primary question at this point is: Should I be worried about embers being pulled into my shop vac and igniting the sawdust in there? Would the dusty deputy make this worse or better?

And pkinneb: Yes. Using the handheld router, when I removed it from my project, there was a little pile of blackened sawdust that was smoking. I dropped it on the ground and stomped it out. There were some embers in there. 

Edited January 24, 2018 by npr_geek
Additional answer to another comment.

[RichardA 4975]

One other possibility.  Your router bit may well be a big box store inexpensive bit [AKA:  Cheap] and it's junk and burning.

[npr_geek 3]

RichardA: That's the best explanation yet. It very much is that. Bought in a cheap set from Amazon when I first got my router.

[Steve B Anderson 179]

I have found that running my solid carbide router bits at around 1400 SFPM (surface feet per minute) works well in hard wood. The formula for the rpm  equals surface feet per minute times 12 divided by diameter times pi. So for a 1/2” bit, rpm should be around 10,695 rpm round up or down for you particular application and adjust your feed as applicable.

[Mick S 2393]

2 hours ago, pkinneb said:

Burning to the point of embers? Really? Are you thinking this or have you actually seen burning embers? I find it really hard to imagine burning embers in any type of router situation

I see it fairly often (not in my work). Even some seasoned woodworkers don't understand the relationship between rpm, diameter, number of flutes and feedrate. I have heard instructors tell students to crank up the rpm's and leave it there because they'll get more torque from a handheld router at high speed. What needs to be remembered is that it's the chips themselves that carry the heat from the cut, so bit design, number of flutes and rpm all come into play as well as feedrate. If you're moving too slow at high rpm, you're not making thick chips. Thick chips carry more heat away. Skinny chips carry less heat so it stays in the cut. No chips (stopped) carry no heat and the friction can start a fire.

On the CNC side, I've had to replace several tables and a few machines because the operators kept slowing down the feedrate in the file without slowing the rpm also. "Well it was jus' cuttin' so fast we was working our butts off!"

[Coop 7300]

I’m a whole lot better at fire protection than woodworking. You do have a fire extinguisher in your shop, right? Seriously though, there’s not one comment provided above, that doesn’t apply to you. Not meant sarcastically. And hey, welcome to the forum. 

[woodbutcher74 408]

Probably a HSS and not carbide bit. Carbide bits are the only way to go.

[RichardA 4975]

2 hours ago, npr_geek said:

RichardA: That's the best explanation yet. It very much is that. Bought in a cheap set from Amazon when I first got my router.

Take a look at Whiteside tools for your router bits.  If you find them to expensive, then Freud is your next best bet. Just know that better bits, give you better service.

[wdwerker 7646]

Keeping a router bit clean helps too.  I use a strong alkaline liquid spray to clean sawblades and router bits . Spray it on, scrub with an old toothbrush, rinse and dry throughly. Every bit of resin on a bit or blade increases the heat in that area which degrades the edges.

[npr_geek 3]

Thanks for all your help!

[curlyoak 710]

Amana bits are another top choice. 1.25 horse is underpowered for a big demand. But if you set up first for a partial removal then readjust for either a second or maybe a third pass. The less power the less stock you can remove each pass. 

[drzaius 2572]

12 hours ago, woodbutcher74 said:

Probably a HSS and not carbide bit. Carbide bits are the only way to go.

This is true. Particularly when used in plywood, MDF, particle board, or any  man-made wood product. Even in solid wood they dull so quickly that they're just not worth it.

The down side to carbide is that it's harder to get a good sharp edge, and that really shows in the cheap carbide bits. Right out of the package some of them are not sharp enough to be usable

[Unknown craftsman 265]

Wait a minute isn't there a song  "smoke on the router fire in the sky"  

Aj

[wdwerker 7646]

Circa 1972 !  You had your choice of album or 8 track in those days, maybe a 45 of the single. 

[treeslayer 3271]

9 minutes ago, wdwerker said:

Circa 1972 !  You had your choice of album or 8 track in those days, maybe a 45 of the single. 

Jeeezzz Steve how old are you ? I bought a 1981 Buick Skylark new, it had a factory 8 track player, must have been close to the end for them. I'm so old the first car i bought only had AM radio and the TV went off at midnight, just sayin', one old guy to another. sorry for the mini hijack OP.

[wdwerker 7646]

Old enough to know better, young enough to do it anyways !

[Steve B Anderson 179]

I actually had the album, Deep Purple Machine Head. aaah those were the days.

[curlyoak 710]

I have a makita triming router that is 1.25 horse. I use it for morticing hinges. A real shallow cut. Perfect for that router. So you are under powered. I was making dado's with my router on oak. Made it with ease in one pass. A 2.5 horse with a 1/2" shaft to the bit. So you are under powered and probably using 1/4" shaft bits. My guess is you have the wrong tool for the job. Concept is good that you chose a router. I never use 1/4" shafts except when using the makita for light work.

[Mark J 2135]

I want to echo the comments about plywood.  Probably 10% or 20% of what you're turning into dust is adhesive which is harder on the bit.

Also I think the natural tendency when a "cut" is not going well is to slow down.  As pointed out by others that only worsens this problem.

[MisterDrow 415]

Agree with everything that's been said and would like to reiterate the difference a quality bit makes. I used to buy the big-box blades, bits, etc. because I figured they would work just fine... and they did. They worked 'just fine'.

At some point, I needed a specialized router bit in a size I couldn't find anywhere (at the big box stores) and I headed to Woodcraft. I ended up paying $75 for that bit (tongue and groove set) and the thing cuts like butter. I've since bought all new router bits from there (either Freud or Wood River) and will never buy a big-box bit again. Same with saw blades... I ran a Diablo blade in my table saw for a long time and, for the money, it cuts really well. I recently purchased a Freud flat-top ripping blade for joinery and it cuts better and cleaner than my 40T Diablo combination blades ever did. 

There are times you can get away with the cheaper option on certain tools/supplies, blades/bits are where the magic happens and having a good quality one makes all of the difference in the world.

[npr_geek 3]

Thanks for all the great input. This is a really terrifically responsive community, so thanks for the warm welcome! For the record, I did a little bit of everything suggested, and it's all been an improvement. After I cleaned the bit, the burning problem went away. I used another bit and didn't have this same problem. I also purchased two new bits from Frued to replace my 1/2" and 3/4" straight cut bits, and expect to enjoy better results. Oh, I've also confirmed my fire extinguisher is A-Okay! 

For the record, since I'm new to routing, I've found it really useful to have a cheap set of bits getting started. This has helped me identify which bits I actually use regularly, and then I can now proceed to replace only those bits. Also, now that I've built this router table and realized how awesome it is to have in my shop, I'm already contemplating getting a bigger router to put in there. I was always aware that 3/4 HP was quite small, but my earliest use-case vision for this table was just doing round-overs and small dados. I can now see there's much more I can do if I up the power. 

Thanks again!