Routing Question

[Garno]

I have a 1/4 inch hand router and need to cut a 5mm channel in some wood.
The width of the channel is to be 9mm to run the whole length.
It will start 13mm from the top edge. (it's basically a rectangle with a 9mm channel running 13mm from one edge) I also need another through the middle of the wood 250mm

The problem I have is the flute to cut / router is only 6mm. So far using a straight edge clamped down I have cuts that are either too narrow (8mm) or too wide 10-11mm with no consistancy. I am basically putting the flute edge either on the line or slightly below the line and then butt up the straight edge to the router, and as I say the results are very haphazzard to say the least.

Is there something I can do to get accurate results each time I use a flute in a hand router? I am not sure where to measure from.

 

[Sideways]

Clamp a straightedge to some scrap, pick your cutter, make a cut, even two or three passes keeping the router base firmly against the straightedge.
Measure the (near) edge of the resulting groove from your straightedge. That's your offset with that router and bit
You will never get closer to the straightedge than that however much you wobble, unless you actually tilt the router off it's flat base.
You may need to note which side of the router you're using against the straightedge in case the base isn't symmetrical.

You can use the straighedge on both sides of a groove to cut any width you want without over cutting it.
Clean the middle out carefully freehand if necessary if you're making a wide groove and the two passes don't overlap.

If you're working close to an edge, either use a spare piece of timber to support the router and use the straighedge on both sides, or you need to take the extra measurement from the straighedge to the far side of your calibration cut, and then make all your cuts with the fence on the smae side of the cut. You have to be dilligent holding the router tight to the fence when doing this. Remember you are cutting with a the opposite side of the cutter, so the direction you feed along the fence should reverse for the second edge of the groove.

Use good clamps and measure carefully. I like to use steel rules with a veritas sliding stop or a good combination square to transfer offsets like these with minimum actual measurement. I would be looking for better than 0.5mm in my measuring of the straightedge position before I start to cut. Less if I'm using the ruler stop or combi square to transfer the offset. I'd check it two or three times each end as when you bring each end of the straightedge up to the correct offset, the opposite end always moves too. I find 3 or four iterations are often needed to get both ends close enough that I can't improve on it.

 

[Garno]

Clamp a straightedge to some scrap, pick your cutter, make a cut, even two or three passes keeping the router base firmly against the straightedge.
Measure the (near) edge of the resulting groove from your straightedge. That's your offset with that router and bit
You will never get closer to the straightedge than that however much you wobble, unless you actually tilt the router off it's flat base.
You may need to note which side of the router you're using against the straightedge in case the base isn't symmetrical.

You can use the straighedge on both sides of a groove to cut any width you want without over cutting it.
Clean the middle out carefully freehand if necessary if you're making a wide groove and the two passes don't overlap.

If you're working close to an edge, either use a spare piece of timber to support the router and use the straighedge on both sides, or you need to take the extra measurement from the straighedge to the far side of your calibration cut, and then make all your cuts with the fence on the smae side of the cut. You have to be dilligent holding the router tight to the fence when doing this. Remember you are cutting with a the opposite side of the cutter, so the direction you feed along the fence should reverse for the second edge of the groove.

Use good clamps and measure carefully. I like to use steel rules with a veritas sliding stop or a good combination square to transfer offsets like these with minimum actual measurement. I would be looking for better than 0.5mm in my measuring of the straightedge position before I start to cut. Less if I'm using the ruler stop or combi square to transfer the offset. I'd check it two or three times each end as when you bring each end of the straightedge up to the correct offset, the opposite end always moves too. I find 3 or four iterations are often needed to get both ends close enough that I can't improve on it.

Sounds so easy once I read it, I have spent hours trying to work out a way
Thank you

 

[Sideways]

we've all been there !
One other trick that I like :
if I was doing work like this on pieces up to about 300mm wide, I might set the router up with a set of long fence rods ( I have some about 500mm long) and a fence fitted on both sides. The long rods and second fence are things I've found very handy. One fence is "original", the other I've replaced the plastic wear surfaces with a 300mm length of maple that extends straight through side to side and has a clearance cutout to suit the cutters I typically use.

Snug the fences together so the stock is a smooth sliding fit between with no slop, then move the router along the rods between until it's lined up where I want. That will also put a groove where you want it with no wandering off.

Router with two fences is great for edge work of all sorts, including mortices for door locks. It's not as fast as by hand or with a chisel morticer and you will probably have to finish the depth by hand chisel but you can get a VERY clean tight fit if you want.

 

[peter-harrison]

If I wanted to make a precise 8mm groove using a 6mm cutter and a straight edge, I would set up the straight edge to make the first cut, and then take a second straight edge, clamp it so that it was touching the first one, loosen the first straight edge, and put two 2mm drill bits or other packers between the two straight edges, gently slide the first straight edge up, clamp it, remove the second one, and away you go.
If you want to move the first straight edge the other way, use the spacers between the two before you clamp no. 2 down the first time.
I hope that's clear- it seems a complicated way of describing a simple operation!