How do you rout a chamfered patch?

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EastCoastChris

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Hi All,

I'm really hoping someone knows the answer to this one! :confused: The chap who did some repairs on my hull appears to have done the following....

Routed out the area that needed replacing with a chamfered edge (hard to see in the photo). I presume he used a template as you can see the pieces of tape with registration marks on them for lining the template up.

4061950962_cf8ec8d43f.jpg


He's then routed a replacement piece from new ply to exactly fit into the area he had previously cut out. The piece fitting in has an exact reciprocal chamfer.

4082831707_47baee870a.jpg


You can see from the image below he's got a very tight exact fit.

4082837635_413f2c1a73.jpg


I'd really like to know the easiest method for doing this, does anyone know how it's done? The only method I could think of requires a chamfer bit with a guide bearing at the top and these don't seem to exist. :confused::o

Thanks :D

Chris

P.S. I've not found any more problems with my hull, I'm wanting to use the technique for dropping a piece into my foredeck.
 
Get a bit with a bearing on the bottom and work from the other side . Add batterns to take the bearing if you need to . Another way would be to slip a bearing over the shank of the cutter , you must be able to get on the right size from somewhere ? Although i have never tried this method .
 
Would it not be possible to ask the guy how he did it? Most routers come with a top guide for the 'plate' to follow moulds. And I have dovetail bits with top bearings. The problem is the ramp needed to get the scarf angles. And holding them onto the hull,plus coping with the hull curve. I have only done flat scarfed sheets, so it looks a bit more complicated.
Might not your foredeck be easier with hand tools, plus some carefull use of a power plane or even an angle grinder(!!) All have worked for me.
A
 
Cuchilo said:
Get a bit with a bearing on the bottom and work from the other side ... slip a bearing over the shank of the cutter
Click to expand...

He definitely did it all from the outside, there are two bulkheads and a frame that would have made it very very tricky from the other side. A chamfer bit without a bearing and adding a bearing over the shank was the way I was heading, but before I go spending money, I just wanted to check I wasn't missing something ingenious :)

DownWest said:
Would it not be possible to ask the guy how he did it?
Click to expand...

He takes some getting hold of and aside from it being a bit cheeky, given it's how he earns his living I'm not sure he'd be that keen to give away his secrets. He's done me a cracking job, he doesn't really deserve me putting him in an awkward position.

I'm guessing you must need two bits with matching angles, cut the hole with the top bearing on the template and cut the infill with the second running the bottom bearing along the template? That doesn't work though as you're too small by the diameter of the bottom bearing? :confused:

Chris
 
this may seem a very dim suggestion, and it's from a rather inexperienced woodworker, but ...

1 router a determined shape to be the infill piece

2 tack the infill piece on to the transom and use it as the template for routing out the area to be removed.

Using one piece as infill and template with bitwo bits, one negative angle and one positive - surely they must match up exactamento ?

Or have I missed something basic ?
 
yes, I'm now visualising this more clearly, you're right.:o.

Second suggestion. Tack infill piece with the large chamfered edge adjacent to transom, mark out, and use a jig saw set with an angle inwards.

It's great in theory :)
 
I would have thought two templates have been used with a collar and chamfer router bit? Strikes me the only way to get a chamfer to meet the other internal wood work.


Does look a very good job.
 
stav said:
I would have thought two templates have been used with a collar and chamfer router bit?
Click to expand...

I've been wondering about a two template approach, what has me puzzled is cutting the second template (for the infill) accurately enough is much the same problem as just cutting the infill.

Chris
 
It would be quicker to rough out the hull with a skill saw set at the depth and at 45* and clean up by hand than make two templates . Thats probably how i would do it anyway .
 
I'm a bit puzzled by this. Chamfered router bits are usually only around 45 deg. Whereas the scarf needs 8:1 slope. There are some special bits for door panels, but you cannot use them hand held, only in a table.Pricey too..
I built a scarfing jig that guided the router by two ramps, one either side of the work. The router had had an extended plate (basicly two square tubes) so that it could travel across the cut, as well as down the ramps for the slope. But this was for stacked sheets to make long hull panels.

In your case, I would suggest temporaly fixing some wooden ramps (wedges) either side of the hole and screwing the router to a bit of 12mm ply so it can follow the wedges with the bit protuding below to make the cut. BTW, from your photos, it looks as if the edge is stepped i.e. not feathered to the edge. This makes for a much tidier job and would require stops on the ramps (screws) so as to make a straight edge at the step.
The reality is, unless it is a big job, like the hull patch, and you are set up for it, doing it by hand is probably swifter.
Andrew

Just looked in Axminster's catalogue and there is a raised panel cutter that might do some of it (and cut the step) Item 800183-05, not bad at £30. BUT, it says not hand held, so..
 
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You can get 30 degree bevel bits - http://www.wealdentool.com/acatalog/Online_Catalogue_Bevel_plunge_664.html - it is my understanding that these sort of operations are done with battens and homemade guides or templates. Battens for the straight edges either tacked on or using double sided sticking tape; homemade templates for the radius cuts, affixed in the same manner (although the "internal" radius is likely to be the natural radius of the cutter bit - especially if 30 degrees as this will be a substantial cutter; the external radius i.e. that of the patch will require the template).

If you set the plunge depth using the stop, you will have a constant offset for the top edge of the bevel (this is normally determined with trial cuts in scrap timber), allowing you to set the battens the correct distance away from the finished cut. A similar process is carried out for the patch, only this time cutting from the internal face. Using a guide bush, this is made more manageble - http://www.woodsmith.com/issues/158/videos/using-router-guide-bushings/

Like most router work the actual cutting is about 5% of the job, much of it is the setup and preparation.

P.s. I've just looked closer at your 1st picture and enlarged it - there does not appear to be much if any bevel on the cut-out...
 
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The best way I think is to make up a jig to the size you want to remove and rout it out with a giude bush and shamfered cutter then use the waste as a giude to rout out the new to fit. That way any slight miss with the first will be reapeated on the second ? Try it out on an off cut first. Good luck:)
 
EastCoastChris said:
I've been wondering about a two template approach, what has me puzzled is cutting the second template (for the infill) accurately enough is much the same problem as just cutting the infill.

Chris
Click to expand...

Making two templates is easy if you have access to a largish CADCAM router, but even if not it should be able to make two templates to better than 1mm accuracy. The inner template can also be made from the offcut from the larger template.

An alternative approach would be to make the inner template and then have some spacers and make the outer template from stripes fixed around the first template and the spacers, if that makes sense?
 
When testing solid timber and ply joints to destruction using epoxy resins and a variety of additives I found the best results had a minimum layer of not less than 2.5mm and a maximum of 5.5 mm, using West System.

has this gap been taken into consideration when setting up scarf joints?
 
It's not a scarf joint, it's a butt joint with backing straps etc. But bevelling the edge adds extra strength to the job. In the context of my foredeck repair, having the 45 degree chamfered edge reduces the risk I could break the joint when I heave on the anchor and happen to be standing right above the corner of the patch.

I've ordered a suitably sized 45 degree chamfer/V cutter which goes to a point (no bottom bearing) and a guide bearing sized to the top diameter of the cutter. I think if I do the following it should work:

1. Run this top bearing around the template routing the chamfer in the deck

2. Turn the template over and put it on the new ply and rout out the infill piece running the bearing along the template

3. Invert the new piece of ply and drop it into the deck as cut in step 1.

I think the infill should be an exact copy (as the outside edges are identical from following the same single template). If I didn't invert the template I'd get a mirror of the whole in the deck when I turned the infill the right way up.

Have I missed something obvious, or does this sound like it should work? (Needless to say I'll cut a few test goes first!)

Chris
 
router guide bush collars

take a look at

http://www.axminster.co.uk/product....router+template&user_search=1&sfile=1&jump=96

This is a collar that fits over the guide bush mounted on a router. It is removable, allowing you to compensate for the diameter of the cutter (ie not producing a patch smaller by the cutter diameter)

Use a chamfer bit without bearing

basically, make a female template of the cut out, rout the hole in the deck using router with guide bust AND collar, then, off the boat, make the infill piece using the template and guide bush without collar.

Clear as mud!
 
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