making templates

[burraboy]

I've got a few small projects coming up where I would like to inlay some etched 2mm brass plates flush into timber frames. These brass plates will be different shapes and I would like to use the router to cut the recesses to hold them. I can vaguely remember some technique for cutting templates from the original shape and then using those templates with different size cutters and template guides to cut the recess. Can someone point me in the right direction?

[glenn k]

search Template Tom

[rayintheuk]

He now posts as Tomod

Ray

[burraboy]

Thanks fellers, I found and read this thread http://cdn.woodworkforums.com/images/icons/icon1.gif <!-- google_ad_section_start -->Routing with the aid of template guides<!-- google_ad_section_end --> . It was a little hard to follow in spots, but I think I got my head around it.
I think I can summarise it this way;
You start with an original shape and produce a 'female' template from it, using one of the two possible methods.
You can use a straight cutter with a bearing to follow the original shape, assuming the cutter and the bearing are the same size, this will give you a female template bigger (by a value of x, say) than the original and here x' = c, where c is the diameter of the cutter.
You can also use a straight cutter without a bearing, using a guide bush to follow the original instead. In this case, x'' = (g+c)/2, where g is the diameter of the guide and c is the diameter of the cutter you use.
So far so good?
Then comes cutting the hole to recieve the original piece. You need an new guide for you router, I think for this operation that g' needs to be >2x. Calculate the diameter of the cutter you need from the equation (g-c)/2 = x.
An added bonus to having this female template is that you can then reproduce the original shape. The maths required to work out your guide and cutter sizes becomes, I think, (g+c)/2=x, but in this case, start with g<2x to begin with. This becomes useful if you make your original shape freehand from scrap material, you can then get into mass production for your patterns and still use the one female template for both the patterns and the pattern hole.
Can someone (tomod?) have a look at this and tell me if I'm making a big mistake somewhere?

[Fencepost2]

Sorry I am a bit thick in the head to check on all your formulae, and I have possibly got it wrong, but, if you are "circumnavigating" a template with a straight cutter with a bearing, the female shape will be bigger by two times the diameter of the cutter.
I have never tried this method, but I worry about the reliance on keeping the bearing tight against the template all the time. Any slight drift off the close contact will result in a bigger than expected female shape at that point. I always like to have situations where drift away from the template is into waste wood. Please keep up the thread on this topic, I am keen to learn.

[malb]

You can buy an "Inlay Kit" comprising a cutter, and a special template guide with detatchable bush. Using these you can create a single template which will create the female and male parts for the inlay (recess and insert). One part is cut with the expander bush installed, the other without it. The expander bush system compenstes for the difference between cutter and guide diameter.

Provided that the brass inlay was of the softer variety, I suspect that it could be routed to shape using this system, but would suggest buying a seperate cutter and dedicating it to the brass work.

The other issue that you face is the actual curve radius that you can use, the guide with the expander bush installed is about 10mm while the cutter is about 3mm. This would limit the fine detail possible.

Here is a link to a Woodsmith/Shopnotes podcast (http://www.woodworkingonline.com/2007/03/05/podcast-14-router-inlays/)you could download to explain the system in detail.

[glenn k]

Burraboy I can make sence of your first part (x=(g+c)/2) but not the second; it may make sence but I can't follow it.
Rather than complicated formula why not make it simple.
If you are going to use the same female template to cut a hole and a plug to fill the hole, you will need two guides one 2x the diameter of the cutter larger than the other.
The diagram shown will work so would a 10mm cutter with 30mm and 50mm guides. Unfortunately these things usually come in inches so it is more complicated.
Malb your way sounds better. Wish you had posted a bit earlier.

[tomod]

Thanks fellers, I found and read this thread http://cdn.woodworkforums.com/http://cdn.woodworkforums.com/images/icons/icon1.gif <!-- google_ad_section_start -->Routing with the aid of template guides<!-- google_ad_section_end --> . It was a little hard to follow in spots, but I think I got my head around it.
I think I can summarise it this way;
You start with an original shape and produce a 'female' template from it, using one of the two possible methods.
You can use a straight cutter with a bearing to follow the original shape, assuming the cutter and the bearing are the same size, this will give you a female template bigger (by a value of x, say) than the original and here x' = c, where c is the diameter of the cutter.
You can also use a straight cutter without a bearing, using a guide bush to follow the original instead. In this case, x'' = (g+c)/2, where g is the diameter of the guide and c is the diameter of the cutter you use.
So far so good?
Then comes cutting the hole to recieve the original piece. You need an new guide for you router, I think for this operation that g' needs to be >2x. Calculate the diameter of the cutter you need from the equation (g-c)/2 = x.
An added bonus to having this female template is that you can then reproduce the original shape. The maths required to work out your guide and cutter sizes becomes, I think, (g+c)/2=x, but in this case, start with g<2x to begin with. This becomes useful if you make your original shape freehand from scrap material, you can then get into mass production for your patterns and still use the one female template for both the patterns and the pattern hole.
Can someone (tomod?) have a look at this and tell me if I'm making a big mistake somewhere?
Better answer this before New years eve sets in
My method of inserting inserts.
If I make a template circular/elliptical and using a 30mm guide with a 10mm cutter I rout out to the depth I require. Secondly with the material that has to be inserted secured, I use the 16mm guide with a 4mm cutter,using the same template.

As I read it your problem is producing the initial template to suit the material to be inserted.

We start the procedure by measuring the size that has to be inserted and make the template 20mm larger all round then you are all set to begin, this could be done using the original shape(subject to it being thick enough to work on) and select a 16mm guide with a 4mm cutter to rout round the external edge Then you have your template 20mm larger all round. Rout out your shape 30mm guide 10mm cutter and the original will drop in. (Subject to your cutters being true size as they could be smaller after a number of sharpening s)

I hope I have made it clear anyway give me a pm and I will hopefully answer your questions
Happy New Year
Tom

[burraboy]

Thanks all. It looks like that maths holds, but wouldn't you know it, there's a kit on the market that will do the job without needing to do the sums! The only worry I have is the relative sizes of the bits involved, the kit is pretty fine compared to tomod's suggestions. I can see advantages and disadvantages in that too.
Thanks again!

[Mike Wingate]

I have just watched the above video. Here is one I made earlier, I guess I was lucky.

[burraboy]

Looks alright to me Mike, what did you use in terms of router bits and so on?

[Mike Wingate]

I used an 1/8" kit from MLCS, Harbor Freight have got one for $10us.
MLCS router inlay set (http://www.mlcswoodworking.com/shopsite_sc/store/html/smarthtml/pages/router_inlay.html)
- Harbor Freight Tools - Quality Tools at the Lowest Prices (http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=99552)