Routing a slot

[Nelly111s]

Currently I make a small product for which I route a 30mm slot in a 45mm wide piece of hardwood (see diagram). I need to scale this up, to route a 48mm slot in something probably about 62 mm wide. I use the router table for the current operation and its fairly simple since I have a 30mm cutter. I don't (yet) have a 48mm cutter, so I was wondering if I could route this slot using a 35 mm cutter (the widest I have). However, I can't for the life of me work out how to do this safely. I know I can cut a 35mm "relief" cut down the centre, but how do I widen the slot without removing the radius at the bottom of the slot or having a climb cut on the inside edge on the table (I won't do this). The piece of wood is approx 24mm thick, so holding it in a vice to get the router fence to it isn't really possible. I'm "sure" there's a simple solution, but I'm b******* if I can think of it!

 

[TheTiddles]

From the top freehand with a guide bush and a template

 

[Doug B]

From the top freehand with a guide bush and a template

Yep that’s the way I’d do it

 

[DBT85]

Do you want to keep the bottom of the 48mm slot U shaped or flat bottom U shaped?

I've not got a router table or needed to cut a slot like this, but can't you set up your fence, make one pass and then move the fence to make the second pass while avoiding a climb cut? I must be missing something?

 

[mikej460]

To do this without a template and a bush (the easiest way) and assuming you're using fence stop(s), first I would make a similar size piece out of scrap to test your set up. I would drill out the round ends first using a then adjust the vertical height to take two or three cuts along one edge, mark the position of your fence then move it to make the final cut along the opposite edge and mark that position. Rinse and repeat

hope this helps

Mike

 

[custard]

I'm with Tiddles. Except I'd likely use a router bit like one of these,

https://www.wealdentool.com/acatalog/Online_Catalogue_Housing_Rebate_698.html
Assuming the depth of cut is 15mm or less I'd use the 26mm wide cutter, and make a template from 6mm moisture resistant MDF. The template would be a secure fit over the workpiece, then the router bit can simply be run around with the bearing against the template and take the cut in either one single pass, or if you're router isn't beefy enough for that, then make the template from 12mm (or thicker) MDF and you can plunge down between passes and do it in two or even three passes.

If you've got loads to do Wealden sell bearing guided "Vari-tip" bits, with replaceable tips. That works out very economically. If on the other hand you need a super smooth finish or super fast cuts then there are spiral cutting bearing mounted bits.

In other words you can tailor your bearing mounted copy bit choice precisely to the task in hand.

 

[Nelly111s]

Thanks all for the input.
I’ve thought about templates because I have a set of guidebushes, but I’m not sure how I’d fasten the template to such a thin piece of timber so that the slot in the template stays central to the workpiece.

 

[Nelly111s]

Do you want to keep the bottom of the 48mm slot U shaped or flat bottom U shaped?

I've not got a router table or needed to cut a slot like this, but can't you set up your fence, make one pass and then move the fence to make the second pass while avoiding a climb cut? I must be missing something?

It’s holding the workpiece to use a fence that’s the problem is this case. The workpiece thickness is roughly the same depth as the fence.

 

[Farm Labourer]

If your stock is a constant size, then turn the template into a jig, so that it press fits onto the workpiece. The jig cannot move, ergo the slot will be consistent. To make the jig, screw strips to the template - think of an inverted box.

 

[Jacob]

It’s holding the workpiece to use a fence that’s the problem is this case. The workpiece thickness is roughly the same depth as the fence.

Modify the fence?
Add a face piece to the router face to reduce effective size of fence needed?
Make the slot in an oversize piece and then plane to size?
Make slots in each of the opposite sides of a piece more than twice the required depth, then band saw into two and plane to finished size?
Don't rout at all but make up the piece as a shallow box with two sides and a thick base?

 

[DBT85]

It’s holding the workpiece to use a fence that’s the problem is this case. The workpiece thickness is roughly the same depth as the fence.

I'm still missing something Just trying to understand

For your existing 30mm slots you set up your router table, and either a) drop your piece down onto the bit and then push through, or b) push through and do a stop cut. This gives you your U shaped channel that is stopped at one end. Am I right?

 

[Nelly111s]

I'm still missing something Just trying to understand

For your existing 30mm slots you set up your router table, and either a) drop your piece down onto the bit and then push through, or b) push through and do a stop cut. This gives you your U shaped channel that is stopped at one end. Am I right?

It's b) - push through and do a stop cut. You're right

 

[TheTiddles]

My eggy sauce compatriot makes a good point. Although I’ve come over more to guide bushes as you’re less likely to catch the template I find, the size of the dado compared to the stock material might favour a bearing cutter, maybe one with a larger bearing than the cutter

Aidan

 

[Nelly111s]

If your stock is a constant size, then turn the template into a jig, so that it press fits onto the workpiece. The jig cannot move, ergo the slot will be consistent. To make the jig, screw strips to the template - think of an inverted box.

I love the analogy - I think it makes sense now. I could either make a 3 sided jig to use the fence on the 4th side (against the workpiece) or make a template with strips/battons to locate the piece. The stock is consistent width and the thickness varies by about 1mm, so enough to just alter the depth of cut. I have quite a few bearing guided cutters (mainly Wealden), so I'm sure I can find a combination that fits...

@custard The depth of cut is only 8mm and I have a Trend T11 or T5 so depth of cut shouldn't be an issue.

@Jacob I think the "Make the slot in a bigger piece" idea might also work. I'm trying to do two "one-offs" before making this a longer term solution, so that solution makes sense.

All, thanks for the quick replies - its been bugging me for a couple of days and I couldn't think my way out of the problem, despite using templates and jigs for all sorts.

 

[Nelly111s]

Here's a picture of the original that I currently make. I route the slot, then undercut with a small bearing guided cutter to hold the "lid" of the capsule/pod.
Perhaps should have posted this first ... (Homer Simpson moment)

 

[DBT85]

It's b) - push through and do a stop cut. You're right

ok.

So why can't you do that with the router fence in position A and then move it to position B and route again?

EDIT: Now I see your pic I see that it would mean you wouldn't have the rounded stop that you want. It would be a flat bottomed U at the bottom.

 

[TheTiddles]

Here's a picture of the original that I currently make. I route the slot, then undercut with a small bearing guided cutter to hold the "lid" of the capsule/pod.
Perhaps should have posted this first ... (Homer Simpson moment)

View attachment 103555

Ah, the modern equivalent of the oxo cube dispenser.
I’d still make a template and go from the top, use an under cutter bit on the same template afterwards, an l-shape could be used in a vice to hold the workpiece and the template in one hit. If you had one router per bit that’d speed you up
or, laminate them, you could cut material costs and remove the need to get a decent finish on the bottom of the cut which isn’t so easy
Aidan

 

[mikej460]

ok.

So why can't you do that with the router fence in position A and then move it to position B and route again?

EDIT: Now I see your pic I see that it would mean you wouldn't have the rounded stop that you want. It would be a flat bottomed U at the bottom.

That's why I suggested he drills it out? If he used a 48mm forstner it would work but a decent Famag is £56! You can get cheaper ones of course but it may be a case of biting the bullet and buying a 48mm cutter. I would have thought that with either a stop cut on a table would work fine but agree the bush and template approach would also work. I'm not sure if you can get the correct sized all in one cutter with an undercut. If Wealden don't have one then I doubt they're available which then leaves the bush approach using the existing cutter(s).

 

[Nelly111s]

@TheTiddles I have two routers, so I can speed things up. But I then slow them down by having to change bits to put a keyhole slot in the back! The under-cut / slot bit has a bearing which gives me 4mm depth of cut (3mm slot width), so that is fairly straightforward.

Not sure about laminating - do you mean aperture and backplate as two separate items?

@mikej460 I did think about a drill, but a forstner would leave a centre hole where I don't want one (on show). I can get a 50mm cutter from Wealden that is £50, so that will be an option if this new size has a longer term future. I don't think I can get an "all-in-one" slot cutter with undercut, but since I have two routers and already have the slot cutter (Whiteside one) then I'm OK with that.

 

[TheTiddles]

Yep, just that, a separate back plate and a top slotted part. Might not be such a good plan with those thin sides but with a batch cut at the same time as a panel it could work, then cut in half and into lengths
Aidan