Routing beginner seeks tips and technique advice re. cutting a slot

Hi All I have a project in mind which will mean I have to do some routing for the first time. I happen to have a router + table (Ryobi), and enough knowledge to be dangerous... I am keen to maintain a healthy fear of this tool and would like to learn more about recommended approaches before tackling this job.
I basically want to cut slots along the full length of some wood (probably Douglas Fir). The wood is around 1.25" by 1.5" across, say 6 foot long. The slot should be say 8.5mm across, by 18mm deep (sorry about the mixed units), and needs to be sited dead centre within the chosen face. The slot will have straight sides and a flat bottom. Accuracy of the slot width (actually, distance from the edge of the timber to the slot face, and symmetry of this, is the most important criterion.
You don't seem to be able to get 8.5mm straight router bits and in any case I presume the approach would be to do this with a smaller diameter router in several goes. I'm hoping for bits of advice along the following lines:
- what size cutter should I buy? - should I do this: slot from one face at a shallw depth (how deep?); turn the wood round; slot from the other face increase the depth (by how much?); repeat or: slot from one face increase the depth slot from the same face ... until sufficient depth, then reduce depth; repeat above from other - how best to measure up all of this to ensure an accurate result - tips on feeding the wood in and similar - any specific safety points I should bear in mind?
I am expecting to to do some experimenting to get the right result, but don't want to waste too much timber, or any fingers, in the process...
Thanks a lot for any thoughts Jon N
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On 4/26/2016 9:10 PM, jkn wrote:

You don't say whether this is a quarter inch or half inch machine. The bigger ones have much more "oomph".
Cutter size perhaps 6 mm? I'd probably do it the first way. 18 mm is quite a deep "slot".
Practice on say 2 foot length until you have nailed the technique. For six foot lengths you will need supports at the right height on both sides of the table.
With this relatively small section timber I am not sure if a standard router table is really the right tool. If you have a sufficiently long workbench, it might be better to clamp the wood to the bench and slide the router either using its own adjustable guide, or sliding it against another fixed guide rail attached to the bench (i.e. fabricate yourself a jig a bit like a sawboard).
I make no claims to be a router expert, I find them quite difficult to use.
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I'm not one to ask about routers. But a piece like that is very flexible, a nd much more so when cut in half by a slot. How are you going to clamp it i n place without getting in the way of the router, and without the clamp los ing all grip as the slot is cut?
NT
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snipped-for-privacy@gmail.com writes

Can you start off with a larger work piece and reduce it to the finished size once the slot is cut?
My other thought is that I would not use a router for this particular job. Repetitive cuts with an adjustable depth of cut table saw will give an adequate finish and be marginally less hazardous:-)
--
Tim Lamb

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On 27/04/2016 20:35, Tim Lamb wrote:

I was going to suggest cutting the sides of the slot with a circular saw and removing the rest with the router.
--
Reentrant

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Reentrant wrote:

getting 0.5mm accuracy with a circular saw is ambitious ...
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Yes. Minimal final cuts where all the material is to be removed by the saw.
I doubt I could do any better with a hand fed router.

--
Tim Lamb

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Prompted by another poster, I remembered you may have to adapt or temporarily remove the riving knife. On my cheap Titan table saw, the riving knife is a few mm short of the cut and rises and falls with the depth adjustment.

--
Tim Lamb

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On Thursday, 28 April 2016 09:43:16 UTC+2, Reentrant wrote:

+1
Or even a chisel for the bulk of the waste in the middle.
- and even if you felt you needed a router quality finish on the slot, it might well be quicker/easier/safer to rough it out with a table saw, and then take the final nadge's whisker off with the router.
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Hi John, Bob and all
newshound wrote:

Thanks for the great pointers - that was exactly the sort of information I was hoping for.
The router has a 1/2" chuck FWIW - it's a Ryobi ERT 1500V. And I am pretty sure I have a 6mm straight cutter to suit ;-)
I have enough to go with now - it might take me a few weeks to get around to setting everything and making the necessary trials up but I feel much more confident now.
Thanks again Jon N
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jkn wrote:

Never use a cutter of the final size of a slot. It will tend to bounce from side to side and give a rough finish. Feed the wood in left to right so the side of the cutter furthest from the fence is doing the work. Do not use the router to climb cut other wise it is like to snatch the wood from you and self feed. Use 1/4" two flute cutter routing to 8mm wide by passing through with one face against the fence and then the other to keep the slot central - set up with a test piece of identical cross section. Increase the depth in say 5mm increments. Use 2 orthogonal feather boards to keep the work pressed down to the table and against the fence. Once at final depth, nudge the fence over by 0.25mm away from the cutter and pass through twice to get 8.5mm final width. Use vacuum extraction from below the table to remove the waste and avoid jamming the cutter in the slot. Keep the workspace clear and make sure you have no obstacles on either the indeed or outfeed side for at least the full length of the wood. Feed at steady speed listening for any change of sound to suggest the router is labouring. Ease off accordingly. DONT stop mid cut unless there is a problem otherwise a tell-tale mark or burn will be left on the wood.
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On 26/04/2016 21:10, jkn wrote:

A little fear is good ;-) However routers are not usually too scary unless you have huge cutters on them.

OK, so that tells you you need a cutter narrower than the final slot size, and you want to route, referenced both both sides of the wood. That will ensure that your final cut is dead centre.

1/4" Straight fluted cutter sounds like the cutter for this job

Depends partly on the power of the machine, however you will be using a smallish cutter here, so best not to try and take too bigger bite at t a time. I would suggest routing about 1/4" (or 6mm) depth per pass, taking three passes per side to get to full depth.

Yup, the second one - less setting up and re-setting.

Mark out your slot carefully on the timber (use a marking gauge if you have one) then use the fine adjustment of the side fence (if it has some!) to set the cutter offset from the edge of the timber.
To make it easier to start and stop at the ends, screw a longer wood batter to the fence - that way there is less chance of wobbling at the start or end of the cut where you may not have the full fence against the timber.
(this is a job you can either do handheld with a fence attached tot he router, or you could do it on the table with the table fence)

You want to route in the direction which pulls the timber against the fence - so visualise the leading edge of the cutter - it wants to be moving toward the fence - that will tend to pull the direction of travel toward the fence. (going the other way is called "climb cutting" and is not generally avoided for heavy cuts)

Take your time to setup. Make sure your workspace is clear enough. Do a dry run though the motions you will make to ensure you don't hit snags like running out of lead length or hitting some obstruction as you try to move about. You are looking for a nice steady feed rate without interruptions if possible. Listen to the note of the machine to judge how hard you are working it. Practice on a bit of scrap first.

--
Cheers,

John.
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Whealden do 8.5mm straight bits - 1/4 inch or 8mm shank with 20mm cutter length. (Not that that's
important as you'll want to do about 3 or 4 passes)
http://www.wealdentool.com/acatalog/rout_cat.pdf
As you've got a table.
First off , before mounting the router, drill with the plunge router an 8.5mm hole dead centre on a short length of board. Take as much time as you need on this, and as many attempts, as the accuracy of all subsequent slots will depend on this. Having drilled your hole, mount the router under the table with the cutter protruding. Slot the board with the centre hole onto the exposed cutter. Now clamp two fences either side of the router table with g-clamps tight to the sides of the board. You can chamfer the inward face of the fences to make feeding easier. You can also rub a candle along the fences. After removing the set-up board you can then feed the boards between the fences. The number of passes with probably depend on the timber, but 3 or 4 should do it. You do all the boards as a batch at the first setting raise the cutter by 3 or 4 mm. and repeat. In addition do one spare length. Use this to set the final cut. As you adjust the height for the final cut only feed in a foot at a time and then measure. Only when its correct should you feed in two feet, Check again Then do the rest.
michael adams
...
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