one for the routerers...

[MontyVeda]

I'm making an internal router template for cutting a rectangular recess, and will be using a 12mm bit with a 24mm guide bush... I know for external templates I'd make the template 6mm smaller than the cut I need to make, but for an internal template, would it need to be 6mm or 12mm larger?

The cut i want to achieve is 120mm by 15mm.

edited to add... i think it's add 6mm all the way around, which would be 24mm overall.

TIA

 

[twentysix by twentyfive]

Not sure what you are asking. Draw a diagram - that should help your decision.

 

[Poacher]

I think you're

I'm making an internal router template for cutting a rectangular recess, and will be using a 12mm bit with a 24mm guide bush... I know for external templates I'd make the template 6mm smaller than the cut I need to make, but for an internal template, would it need to be 6mm or 12mm larger?

The cut i want to achieve is 120mm by 15mm.

edited to add... i think it's add 6mm all the way around, which would be 24mm overall.

TIA

I think you're right about making the template 6mm larger all round if using a 12mm bit.

Just a few thoughts on this, though. Will you be cutting more than one recess? Quite a lot of work is involved if just one mortice is to be made.
A 12mm bit will leave relatively large radii to be squared off to achieve a rectangular hole. Might a smaller bit be appropriate? e.g. 8mm would still only need two passes per depth of cut to make a 15mm recess. Is the 12mm bit needed in order to cut the hole deep enough, bearing in mind the thickness of the template required to accept the guide bush? I can't quite remember how I went about cutting the mortices for my greenhouse a couple of years ago, but in order to cut deep enough, the sole plate of the router had to be in contact with the timber - a guide bush template wouldn't have worked. I think I ended up with a piece of timber clamped either side of the piece to be cut, to give enough width to keep the sole plate stable, end stops clamped to these to limit the extent of the cut, and used the guide rail on the router to keep the cut parallel. I might have been organised enough to keep notes - if so, I'll try to find them to check this.
(I'm definitely not organised enough to be able to lay hands on them quickly!)
Does the hole actually need to be rectangular? If it's to receive a tenon, you could leave the radii in place and shape the tenon to match.

 

[MontyVeda]

...
Will you be cutting more than one recess? Quite a lot of work is involved if just one mortice is to be made.
...

Yes... hence making a template rather than setting up a fence. I could use an 8mm bit instead... I've already made template number one which is a little bit 'tight' and needs another mm or two taking off it... and knowing me I'll take a bit too much off and have to make another

 

[MontyVeda]

Not sure what you are asking. Draw a diagram - that should help your decision.

neither was i... googling before posting the thread didn't help... but i was getting my terminology mixed up and was searching for router jigs rather than templates, and for some reason thought my guide bush was called a collet Once i knew what i was trying to find i quickly found the information i needed

 

[twentysix by twentyfive]

neither was i... googling before posting the thread didn't help... but i was getting my terminology mixed up and was searching for router jigs rather than templates, and for some reason thought my guide bush was called a collet Once i knew what i was trying to find i quickly found the information i needed

Well done that man.

 

[MontyVeda]

Well done that man.

thank you... now I'm scratching my head trying to suss out the dovetail jig i bought years ago and still haven't got round to using... the instruction booklet is confuddling, and the youtube videos seem to demonstrate that its a huge faff even when you know how.

 

[twentysix by twentyfive]

Keeps the little grey cells fit tho'

 

[HertzvanRental]

thank you... now I'm scratching my head trying to suss out the dovetail jig i bought years ago and still haven't got round to using... the instruction booklet is confuddling, and the youtube videos seem to demonstrate that its a huge faff even when you know how.

I dont know how many dovetails you have to cut, but it is very satisfying to complete them with a bevel, dovetail saw snd chisel!

 

[MontyVeda]

I dont know how many dovetails you have to cut, but it is very satisfying to complete them with a bevel, dovetail saw snd chisel!

anything that involves cutting wood is satisfying