Granny's tooth bedding angle

[J_SAMa]

I've never used or even touched one of these so-called "granny's tooth" router planes (the type fitted with a plough cutter locked down by a wedge). The few example that's come up on eBay recently have extremely high bedding angles, at least 60, approaching 70. My understanding is that routers are primarily used cross-grain (at least the bevel-up 071 and 722 are), so how exactly do you plane cross grain with a blade that steep?

Can't post links to active listings, but here's a picutre so you know what I'm talking about...

It's not like you need to worry about tear out in a dado so how come so many routers were made like this :? ?

Sam

 

[MIGNAL]

I've just made a trial version of a Router plane. I pretty much got the idea from the Sellers poor man's router. The drawback of this type is that you can't see the actual cutters edge. With the more modern, metal bevel up versions you can see the cutters edge. Unfortunately those cutters aren't the easiest to sharpen. My version is supposed to address both issues. . .

 

[bugbear]

I've never used or even touched one of these so-called "granny's tooth" router planes (the type fitted with a plough cutter locked down by a wedge). The few example that's come up on eBay recently have extremely high bedding angles, at least 60, approaching 70. My understanding is that routers are primarily used cross-grain (at least the bevel-up 071 and 722 are), so how exactly do you plane cross grain with a blade that steep?

Can't post links to active listings, but here's a picutre so you know what I'm talking about...

It's not like you need to worry about tear out in a dado so how come so many routers were made like this :? ?

Sam

If the blade were low angle, you'd have serious access problems when routing recesses.

BugBear

 

[MIGNAL]

But why so steep? Why not at 45?

 

[Billy Flitch]

Mignal because at these high angles your not planing but scratching. A back saw is used to make the shoulders of a housing if it is a stopped housing a motice is cut in the stock and then the saw cuts into the mortice to make the shoulders the chisel is the reversed IE bevel down and the housing is cleaned out.
Then the old Woman's tooth is used to scrap the bottom of the housing so you know there are no high points.

So you are not using the tool as a modern router but to scrap the bottom of the housing.

 

[J_SAMa]

Is that to say they can't remove wood aggresively like the 071 does? What if I were to make one at a lower angle?

 

[Cheshirechappie]

I don't know why granny's tooth routers had highish bedding angles, but I'll have a guess or two. As Billy Flitch said, routers are mainly used to level the bottoms of housings, and in that application, you don't really need to bother about finish, just getting rid of lumps - something else will be bedded against the routed surface in the final piece of furniture or whatever. Secondly, you don't need such a big chunk of wood to make one if you use a highish angle. Also, I suspect that the irons of higher-bedded wooden routers are less prone to dig in than lower-bedded ones - but I stand to be proved wrong on this one; it's more a hunch than anything backed by experience.

There's no reason at all why you shouldn't make an experimental router or two with lower angles, and see how they work. My only slight concern is that we may end up with heated debates about the relative merits of bevel-up and bevel-down granny's tooth routers.....

 

[J_SAMa]

My only slight concern is that we may end up with heated debates about the relative merits of bevel-up and bevel-down granny's tooth routers.....

Uh oh...

I think the most probable theory so far is to prevent digging in, but in my experience not even the bevel up routers dig in so much.
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Could you maybe help me find some literature on building a granny's tooth? Most tutorials online only show the bevel up version...
Thank you
Sam

 

[bugbear]

Is that to say they can't remove wood aggresively like the 071 does? What if I were to make one at a lower angle?

The standard advice is to only use hand routers (both OWT or #71 style) to "finish to size", and that bulk waste removal is best done via saws, chisels and gouges.

BugBear

 

[AndyT]

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Could you maybe help me find some literature on building a granny's tooth? Most tutorials online only show the bevel up version...
Thank you
Sam

Did you call?

Go here on Gary Roberts' excellent site http://toolemera.com/Books & Booklets/booksplans.html

and download the Charles Hayward book on making tools. Among many other good things are the instructions you want. Bedding angle = 70°!

 

[bugbear]

I've just made a trial version of a Router plane. I pretty much got the idea from the Sellers poor man's router. The drawback of this type is that you can't see the actual cutters edge. With the more modern, metal bevel up versions you can see the cutters edge. Unfortunately those cutters aren't the easiest to sharpen. My version is supposed to address both issues. . .

There's a quite rare older style shaped like a coffin smoother where the steep blade is nicely visible.

(googly...)

How convenient; there's one on eBay;

http://www.ebay.co.uk/itm/Vintage-unusu ... 1438488987

(but note how much workpiece/clearance that style needs)

BugBear

 

[MIGNAL]

Here's the quick prototype (and obviously way oversized) that I came up with, pretty much inspired by the poor mans router. The small router planes with the L shaped cutter aren't the easiest tool edges to sharpen. The poor mans router (using a chisel) is obviously much easier to sharpen but has the disadvantage of not being able to see what is happening right at the cutters edge. You may need that facility, probably most of the time you don't.
The blade is bedded at 50. I still have to see how it fares when the blade is lowered into a deeper recess. Maybe the blade will start to chatter too much. I haven't really put it through any serious testing yet.
BTW. In the quest for tool development I pretty much ruined a honing guide. :wink:

 

[AndyT]

I've got one of the plane shaped ones as shown by BB and I can't check just now but I'd say the bedding angle was the common 45°. It was easier to use when levelling with the grain on this oilstone box than the old woman's tooth type

The high pitched OWT is fine on a cross grained housing in hardwood but I agree it's only really for a final levelling after chiselling most of the depth.

 

[MIGNAL]

That seems a better design in that you can actually see what the cutter is doing, either by peering over the tool or using it Japanese fashion.

 

[J_SAMa]

Coincidentally Paul Sellers just posted this odd little router:
http://paulsellers.com/2014/05/plane-bu ... ood-price/
It seems to be bedded around 45 deg and is locked down by thumbscrew. I think it's somewhat similar to mignal's honing guide version.
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What would you say about the level of finish the high angled router gives on cross grain? I don't imagine cross grain "scrapes" too well.

 

[MIGNAL]

I don't know. Mine isn't working too well in comparison to my Stanley 271, even though I'm pretty sure the 271 blade isn't quite as sharp. It works, it just doesn't seem to slice through the wood as effectively. The thumbscrews are also a bit of a pain. That's certainly where the Sellers router plane has a distinct advantage. I noticed that the cutter is housed in a little rebate, something I also used on my version.

 

[bugbear]

Coincidentally Paul Sellers just posted this odd little router:
http://paulsellers.com/2014/05/plane-bu ... ood-price/
It seems to be bedded around 45 deg and is locked down by thumbscrew. I think it's somewhat similar to mignal's honing guide version.

It's a shame you'd need brazing facilities to fit the threaded piece to the bent plate, other than
that it's a nice design for a woodworker to make.

The Preston pseudo-Bailey sounds nice;

After an hour the plane was peeling off full length full width onion skins perfectly


BugBear

 

[AndyT]

It's a shame you'd need brazing facilities to fit the threaded piece to the bent plate, other than
that it's a nice design for a woodworker to make.

I agree it's a nice design, but it's not really necessary to have the brass curve round either side of the notch. You could anchor the cutter with a rectangular plate of thickish metal with a woodscrew at either and a central hole tapped to suit a thumbscrew - which would be very basic metalworking.

 

[MIGNAL]

Brazing facilities? Blow torch, suitable solder and some flux. No?

 

[Racers]

You could rivet the brass collar on, a chamfered hole and a hammer and off you go!

Pete