Creating a curved rebate

[RogerS]

I need to crate a curved rebate. My thoughts have got as far as 'I need a template' but then I'm looking for a miracle for the next idea.

Thoughts were some sort of bearing guided cutter using different offset bearings ?

However, the curve is not part of a circle nor an ellipse but a freehand drawn curve. I was thinking that if I had the right trimmer/bearings etc then I could create just the one template by using a different bearing to get the offset for the ‘rib’.

 

[Malc2098]

If it'll fit on my CNC, I could import your hand drawn curve into my CAD/CAM and machine the template for you.

You could then use a bearing guide template cutter to cut the rebate.

 

[RogerS]

If it'll fit on my CNC, I could import your hand drawn curve into my CAD/CAM and machine the template for you.

That's very kind of you, Malc. It's 340 x 760mm

You could then use a bearing guide template cutter to cut the rebate.

My mind always goes blank at this point. This cutter will work if the line is straight.


But as it's curved, don't I need two templates...one offset by the depth of the rebate ?

 

[Malc2098]

I could mill two templates, one of the main curve and one of the offset.

The first template will allow you to mill the main curve. The offset one will allow you to mill the rebate.

I'd include some way of locating each of them in exactly the same place on your work pieces.

You would only need one cutter.

Or —— you could have one template and use a bearing guided rebate cutter giving you the correct rebate offset.

 

[RogerS]

I could mill two templates, one of the main curve and one of the offset.

The first template will allow you to mill the main curve. The offset one will allow you to mill the rebate.

I'd include some way of locating each of them in exactly the same place on your work pieces.

You would only need one cutter.

Or —— you could have one template and use a bearing guided rebate cutter giving you the correct rebate offset.

I prefer the first option as the offset needs to be at least 10mm and I can't see anything suitable.

Do you photograph the hand-drawn sketch ?

 

[Malc2098]

PMd you

 

[Lons]

There's an easier way surely Roger.

Use 2 different screw in guide plates on the base of your router, they usually come in sets. make the template with allowance for the large plate and cut the main shape then swap to a smaller plate for the rebate..

 

[Trevanion]

Homemade ring fence with rebate block in the spindle moulder?

 

[Jonathan]

Rodger, as it's a freehand drawn curve could you not cut the curve out on a bandsaw/jigsaw, finish it with scratch.
Then with a router/spindle use a rebate cutter with a bearing guide to create the rebate.

Or if you want to do it all with the router and not wanting to go free hand maybe a CMT flexible template would help.

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[RogerS]

Homemade ring fence with rebate block in the spindle moulder?

I did think about that as it's a damn good idea but for one thing. As you've probably guessed it's that front door and it weighs a ton.

 

[RogerS]

There's an easier way surely Roger.

Use 2 different screw in guide plates on the base of your router, they usually come in sets. make the template with allowance for the large plate and cut the main shape then swap to a smaller plate for the rebate..

Doh.....I've got those. :eusa-doh:

 

[RogerS]

.....
Or if you want to do it all with the router and not wanting to go free hand maybe a CMT flexible template would help.

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Thanks Jonathan...not seen that and bears much further consideration. :eusa-think:

 

[spb]

Or —— you could have one template and use a bearing guided rebate cutter giving you the correct rebate offset.

I prefer the first option as the offset needs to be at least 10mm and I can't see anything suitable.

Wealden's standard series rebate cutter will do anything up to 15mm width with the right bearings, and there's a large series for bigger ones. Will that not do the job?

 

[Woodbloke]

There's an easier way surely Roger.

Use 2 different screw in guide plates on the base of your router, they usually come in sets. make the template with allowance for the large plate and cut the main shape then swap to a smaller plate for the rebate..

Yep, that's the way I'd do it - Rob

 

[RogerS]

This has been a very good example of Team-Think ! Lots of excellent ideas and suggestions.

My starting point was how to create the template(s). Malc kindly offered to make one or two for me but I still had the problem of getting the hand-drawn curve (in white chinagraph) on the door into a medium that would allow Malc to create it. Lots of possibilities for error-creep on my part.

Then Jonathan came along with a 'blinder'....that CMC template which can be screwed directly to the door. I simply screw, bend, screw, bend faithfully following my hand-drawn curve.

Then the question of the rebate was next and Lons reminded me about guide-bushes (which I have) and so I don't need to worry about bearings et al. May well be able to get away with existing router cutters in my possession which is always good for the wallet.

Fingers crossed I have enough plunge depth on the router.

Will do a WIP in a separate thread when the time comes.

 

[Jonathan]

Rodger, if you go the flexible template route, I believe they are made of HDPE, so if you have any kicking around you could make it yourself.
Or failing that pop around and I'll give you some, I throw away loads of the stuff. This bag in the photo is ready for the skip

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[Lons]

You want one of the long kitchen worktop 1/2 straight cutters Roger, usually a good 50mm cut. They aren't expensive as a cheapo will work for odd jobs like yours, I have some if you're anywhere near and want to borrow.

E.G. Something like this for a tenner https://www.amazon.co.uk/Trend-BR01X1-2 ... r=8-5&th=1

 

[RogerS]

You want one of the long kitchen worktop 1/2 straight cutters Roger, usually a good 50mm cut. They aren't expensive as a cheapo will work for odd jobs like yours, I have some if you're anywhere near and want to borrow.

E.G. Something like this for a tenner https://www.amazon.co.uk/Trend-BR01X1-2 ... r=8-5&th=1

Don't think that will work, Bob. I need a template trimmer since I'm working straight off the template. Or were you thinking about the 'rebate' cut ? :eusa-think:

 

[RogerS]

.....
Or failing that pop around and I'll give you some, I throw away loads of the stuff. .....
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Many thanks for the offer, Jonathan, but I've already ordered the CMC. Whereabouts are you, anyway ?

 

[Lons]

You want one of the long kitchen worktop 1/2 straight cutters Roger, usually a good 50mm cut. They aren't expensive as a cheapo will work for odd jobs like yours, I have some if you're anywhere near and want to borrow.

E.G. Something like this for a tenner https://www.amazon.co.uk/Trend-BR01X1-2 ... r=8-5&th=1

Don't think that will work, Bob. I need a template trimmer since I'm working straight off the template. Or were you thinking about the 'rebate' cut ? :eusa-think:

You don't need anything apart from a straight bit if you use the screw in template plates I suggested. They work instead of a bearing on the cutter, you just need to work out the offset and cut or fix the template to suit

 

[Jonathan]

Rodger, I'm in Andalucía, just up the hill from Marbella.
Regards cutters you probably know this but the Flexi template works best with a flush bearing on the bottom of the cutter, in a router table.
Then rebate cutter with wheel for the rebate.... I'll post a photo of rebate router cutter in the spindle moulder

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[RogerS]

I thought that was where you were ! You threw me with 'if you're passing by'.

 

[RogerS]

You want one of the long kitchen worktop 1/2 straight cutters Roger, usually a good 50mm cut. They aren't expensive as a cheapo will work for odd jobs like yours, I have some if you're anywhere near and want to borrow.

E.G. Something like this for a tenner https://www.amazon.co.uk/Trend-BR01X1-2 ... r=8-5&th=1

Don't think that will work, Bob. I need a template trimmer since I'm working straight off the template. Or were you thinking about the 'rebate' cut ? :eusa-think:

You don't need anything apart from a straight bit if you use the screw in template plates I suggested. They work instead of a bearing on the cutter, you just need to work out the offset and cut or fix the template to suit

Mmmmm....I think going down that route (for me) lies in tears.

 

[Lons]

Mmmmm....I think going down that route (for me) lies in tears.

You're over thinking it Roger it's dead easy, stick in the cutter and plate, measure the distance between edge of cutter and outer edge of the circle guide e.g. say that's 20mm then your template needs to be 20mm away from your desired cut. Once done leave the template where it is, change the guide to a smaller one to give the required rebate and it's job done. It's easier and you get a cleaner cut with no burning if you take the bulk out with a jigsaw first.

I do it regularly and all the time when fitting kitchen worktops. Have a practice on scrap with what you have and you'll see what I mean

 

[RogerS]

Mmmmm....I think going down that route (for me) lies in tears.

You're over thinking it Roger it's dead easy, stick in the cutter and plate, measure the distance between edge of cutter and outer edge of the circle guide e.g. say that's 20mm then your template needs to be 20mm away from your desired cut. Once done leave the template where it is, change the guide to a smaller one to give the required rebate and it's job done. It's easier and you get a cleaner cut with no burning if you take the bulk out with a jigsaw first.

I do it regularly and all the time when fitting kitchen worktops. Have a practice on scrap with what you have and you'll see what I mean

I see where you're coming from. I've used these before with great success..just that I'd got locked into thinking template trimmers.

I now realise that there is another VIP reason for going down your route...namely that rebate. Very difficult getting the right length trimmers - not to mention a clean bottom cut. Thoseguide bushes remove all of that angst. Plus bits are cheaper :eusa-dance:

 

[Malc2098]

I now realise that there is another VIP reason for going down your route...namely that rebate. Very difficult getting the right length trimmers - not to mention a clean bottom cut. Thoseguide bushes remove all of that angst. Plus bits are cheaper :eusa-dance:

I use short template bearing guided cutters. Once the cutter has cut a rebate to the offset of the template, the rebate itself becomes the template and you descend as far as you need.

£22
https://www.screwfix.com/p/trend-c1...guided-template-profiler-12-7mm-x-9-5mm/343xg

Just sayin'

 

[RogerS]

Missing something obvious here, Malc, as I can't see that working in my scenario. Below is the first pass. First problem is matching the right length cutter that will allow the bearing to run on the template (which isn't that high) but just kiss the bottom of the rebate.

Then I can't see how to finish off the trim of face B?

 

[Lons]

I can see what Malc is saying Roger ( I think). Use a short bearing cutter to take out maybe 15 - 20mm, you wouldn't do the cut in one pass anyway then when you drop the cutter to take the next cut the bearing will be guided by the edge of the first cut.
No reason why you can't do that if you can get enough depth.

edit. That cutter from screwfix has a depth of cut of 9.5mm and 6mm shank so you would need to take 3 passes, personally I'd want a 12mm shank if I'm cutting hardwood that depth but I'm a wimp and I've seen what a snapped cutter can do at 20,000rpm :shock:

 

[spb]

Missing something obvious here, Malc, as I can't see that working in my scenario. Below is the first pass. First problem is matching the right length cutter that will allow the bearing to run on the template (which isn't that high) but just kiss the bottom of the rebate.

Then I can't see how to finish off the trim of face B?

Personally, I'd be doing it in the opposite order. Make your template to exactly match face B, and use a straight template bit to cut that face to the full thickness. Use multiple passes if your cutter isn't long enough to do it in one, with the bearing running on the area you just cut in the previous pass.

Once that's done, then take a 10mm bearing guided rebate cutter and reference from your newly cut face B. You'll almost definitely need multiple passes for this step to get down to depth, unless you have an exceptionally chunky rebate cutter.

 

[RogerS]

....

Once that's done, then take a 10mm bearing guided rebate cutter and reference from your newly cut face B. You'll almost definitely need multiple passes for this step to get down to depth, unless you have an exceptionally chunky rebate cutter.

I like thjat suggestion. Am I right in saying that the door is flipped over between the two operations ?

The bearing references off face B. I can't see how you can make multiple passes unless you have lots of different bearing diameters.

 

[spb]

The multiple passes go in the other direction - the 10mm width from the bearing to the edge of the cutter is the same every time, but there aren't many rebate cutters out there that are 31mm tall. Let's say you had one of the larger Wealden standard series rebate cutters with the appropriate bearing to do 10mm wide rebates. It has a max depth of cut of 18mm top to bottom, so you'd (a) make sure that when you cut face B the dressed surface extends to within less than 18mm of the top, (b) cut a rebate 10mm wide only 18mm deep (i.e. the top 18mm as it is in your diagram), then (c) extend the cutter further below the router base and cut the same width further down, to reach the full depth of the rebate.

Hopefully that makes sense - I'd draw a picture but that'll have to wait until I'm back home.

 

[RogerS]

The multiple passes go in the other direction - the 10mm width from the bearing to the edge of the cutter is the same every time, but there aren't many rebate cutters out there that are 31mm tall. Let's say you had one of the larger Wealden standard series rebate cutters with the appropriate bearing to do 10mm wide rebates. It has a max depth of cut of 18mm top to bottom, so you'd (a) make sure that when you cut face B the dressed surface extends to within less than 18mm of the top, (b) cut a rebate 10mm wide only 18mm deep (i.e. the top 18mm as it is in your diagram), then (c) extend the cutter further below the router base and cut the same width further down, to reach the full depth of the rebate.

Hopefully that makes sense - I'd draw a picture but that'll have to wait until I'm back home.

I will gladly wait for a picture, Stephen !

 

[spb]

OK, here goes:

 

[Jonathan]

Stephen, the problem with that process is if Rodger uses a flexible guide he only has approximately 15 to 20mm to sit his router bed on and the cut will be all over the place......
Now if you turn that position 1 process upside down and have the bearing on the bottom of the cutter your golden.

Or again turn position 1 upside down and work from a router table.

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[RogerS]

Many thanks, Stephen. That is, indeed, an elegant idea. I guess my one reservation is taking out 10mm of sapele in one go. I know that one can gradually drop the cutter dwn the face but, still.. . a big ask ?

 

[RogerS]

Stephen, the problem with that process is if Rodger uses a flexible guide he only has approximately 15 to 20mm to sit his router bed on and the cut will be all over the place......
Now if you turn that position 1 process upside down and have the bearing on the bottom of the cutter your golden.

Or again turn position 1 upside down and work from a router table.

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Filler piece the other side of the template to support the router ?

Router table is out of the question. I can't even lift the door by myself !

 

[spb]

I had absolutely no problem routing 9.5mm square rebates in sapele last time I tried, and that was with a little 18V 1/4" trim router - with a chunkier 1/2" one I'd have no reservations about cutting that sort of size. If it does start to struggle then as you say you can raise the bit up and do more passes to reduce the chip load.

 

[Jonathan]

Rodger.
I was presuming that the head would be shaped before it was fitted to the Stiles.
If the doors is made up then a filler piece would work.



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[RogerS]

Many thanks to you both :eusa-clap:

We have a plan. Just glad the door is still up on the bench. I'm hoping for some help to do the fitting in due course.

 

[RogerS]

Template (as recommended by Jonathan) screwed into an offset position.

I decided I didn't want to try and plough my way through and so removed a lot of scrap with the jigsaw. I wasn't too confident whether the blade would remain vertical and so erred on the side of caution.
Also put in temporary supports to let me remove the scrap in a controlled fashion.


I added some supports for the router base - hot glued in place


Using Stephen's approach, got this chunky cutter fitted to my DW625


and promptly climb-cut


After I'd changed, slowly but slowly hogged out the line


Now faced with making the second pass with a different cutter, I realised that I needed support for the router on the inside


I've cut off some scrap to give me room for the cutter but I realise that if I'm clumsy then the cutter will catch that support and I'll climb cut again . There's a hell of a lot of power in that DW625

Also, I really need an assortment of bearings so that I can take small cuts and as I don't I've chickened out and will try my hand at steaming some wood to form my 'rebate'.