# burning plywood using straight bits



## mumbo (Feb 1, 2012)

I am trying to cut slots in 3/4 ply using straight bits (1/2 inch shank). The router is the big Triton, mounted in a table. I'm dropping the work on to the bit but meeting strong resistance when I start to move the work piece.

Thought bit was blunt so went and bought new ones ( basic kit, not expensive ones).
Lasted for one 4 inch cut.

Any ideas.

Thanks


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## jw2170 (Jan 24, 2008)

Hi Lloyd.

A straight cut through 3/4" ply is a big cut for any router and not normally suggested.

You are using a 1/2" shank cutter, but what is the diameter of the cutter?

It is normally suggested that the cuts in depth be no more that 1/2 the width of the cutter.

EG for a 1/2" cutter on 1/2" shanks only takes cuts of 1/4" on each pass especially in Ply and MDF which are full of adhesives and other gunk.

You may have overheated the cutters and ruined the steel / carbide.


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## Stick486 (Jan 4, 2013)

mumbo said:


> I am trying to cut slots in 3/4 ply using straight bits (1/2 inch shank). The router is the big Triton, mounted in a table. I'm dropping the work on to the bit but meeting strong resistance when I start to move the work piece.
> 
> Thought bit was blunt so went and bought new ones ( basic kit, not expensive ones).
> Lasted for one 4 inch cut.
> ...


time for a new improved and better quality bit or you are cutting too deep in one pass...
go for Italian or USA made bit.... leave the chinese bits on the store's shelf...


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## Stick486 (Jan 4, 2013)

mumbo said:


> I am trying to cut slots in 3/4 ply using straight bits (1/2 inch shank). The router is the big Triton, mounted in a table. I'm dropping the work on to the bit but meeting strong resistance when I start to move the work piece.
> 
> Thought bit was blunt so went and bought new ones ( basic kit, not expensive ones).
> Lasted for one 4 inch cut.
> ...


try an up spiral instead of a straight bit..


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## Skyewalker (Aug 30, 2012)

having the same problem with a 45' lock mitre bit. Burns like crazy, and it wasn't cheap! Is it possible to do lock mitre joint cuts in 2-3 passes without affecting the outcome ? And, yes, I'm cutting 3/4" Baltic Birch ply
HELP, me too.


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## mumbo (Feb 1, 2012)

jw2170 said:


> Hi Lloyd.
> 
> A straight cut through 3/4" ply is a big cut for any router and not normally suggested.
> 
> ...



That all makes sense to me but I saw the concept of cutting slots in a video by Guido Henn on FineWoodworking.com. He made it look easy !! I used a 6mm bit ...probably the cheapness didn't help.

Is it not realistic to attempt a straight through hole and then make a slot from there?
Perhaps the type of bit as suggested by Stick would be better


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## Stick486 (Jan 4, 2013)

Skyewalker said:


> having the same problem with a 45' lock mitre bit. Burns like crazy, and it wasn't cheap! Is it possible to do lock mitre joint cuts in 2-3 passes without affecting the outcome ? And, yes, I'm cutting 3/4" Baltic Birch ply
> HELP, me too.


hog off the bulk of the material/waste with your TS 1st...
cut enough of the lock miter so you can see what can be cut on the TS...


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## woodworker352 (Mar 19, 2012)

You may be cutting too much and moving too slow. I saw this demonstrated at a wood show once. Moving too slow causes the bit to burnish the wood instead of cutting and the bit heats up and burns the wood.


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## mgmine (Jan 16, 2012)

As Stick suggested use a spiraling bit they cut a lot better than a flat tipped straight bit.


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## Mike (Nov 22, 2004)

This photo is using a 1/4" solid carbide spiral up cut bit to make a through slot in phenolic impregnated 3/4" Baltic birch plywood. You can see in the photo that there is no burning. Once the slot is cut you can enlarge it in steps using straight bits with no problem.


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## Cherryville Chuck (Sep 28, 2010)

Lloyd, I'm curious if you've had any close calls by lowering your work onto the bit. This is something I avoid as it is easy for the bit to grab the piece and jerk it out of your hands. If you can do it with the router out of the table and plunge the bit into the work it would be safer and then you could also make multiple passes to get to the right depth.

What you are doing isn't something that can't be done safely, it's just difficult to do safely.


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## Phil P (Jul 25, 2010)

Hi Loyd

I'm in complete agreement with Charles. I do a reasonable quantity of deep plunge cuts onto doors with straight cutters (60mm plus depth of cut). I tend to set the turret to limit my first pass to a couple of mm or so. Once I've made the first pass I rotate the turret and manually step down to the final depth (i.e. I make intermediate depth cuts but not using the turret to limit depth), however _I'm using the router hand-held_ - *above* the work. You are attempting to use a technique called "dropping on" - something which is regarded as potentially dangerous (i.e. with significant risk of injury depending on the depth of cut) and to be avoided if safer alternatives are available

The approaches shown here with a plunge router are far and away safer as well as being what using a plunge router is all about. 

Loyd - do yourself a favour. You have a very well designed plunge router there. Take it out of the table and make plunge cuts to do your stopped grooves - it will be much safer and your cutters will last longer, especially if you limit the depth of cut per pass to no more that the diameter of the cutter as James has recommended above

PS Your cutters will need to be a plunge cut design - normally they have a additional piece of carbide brazed across the bottom of the cutter

Regards

Phil


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## mumbo (Feb 1, 2012)

Cherryville Chuck said:


> Lloyd, I'm curious if you've had any close calls by lowering your work onto the bit. This is something I avoid as it is easy for the bit to grab the piece and jerk it out of your hands. If you can do it with the router out of the table and plunge the bit into the work it would be safer and then you could also make multiple passes to get to the right depth.
> 
> What you are doing isn't something that can't be done safely, it's just difficult to do safely.


Yup..Charles you hit it in one. I did have that problem and assumed it was my inexperience. (it was!). Survived the throw and managed to get it right using the spiral bit suggested in this thread. Seems a shame not to use the table mounted router though but will take your advice next time. 
The first spiral bit I used seem to cause more of this problem. Could it be because it was a Down spiral perhaps? Throwing the work upwards maybe?

Thanks to all for your advice.... Luckily I'm only building a jig at this stage ..no "real" wood damaged.


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## Cherryville Chuck (Sep 28, 2010)

Lloyd, if you are using a down spiral it would want to push your work up from the table which would make it very hard to control. The real risk with the method you've used so far is that in your attempt to hold and control the piece, that when the bit grabs it your hand can get pulled into the bit. It can happen so quickly that it can be impossible to prevent.


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## mumbo (Feb 1, 2012)

Charles and Phil
I can't thank you enough for your very wise safety advice. From now on I use my other hand held router or take the "big" one off the table. I very nearly learned the hard way as the pieces did originally "bounce".

Cheers

Loyd


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## Cherryville Chuck (Sep 28, 2010)

Loyd, If you are ever not sure about how you are planning on doing a job don't be afraid to ask. You'll usually get several different ways to do the job and you can decide the one that either seems the safest or that best suits your skills and equipment.


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