Ya learn something everyday

[The3rd Earl Of Derby]

Did you know you can cut a half moon coving shape with your table saw on a length of wood just by using the correct angle to the blade and a decent enough lenght guide fence to pass it through the blade.

[Grumpy owd man]

Yup! Don't know if you can still get them but,...we used to use some things called 'wobble washers'. This was a bit like a spacer [thick washer] that was cut at an angle across the thickness of the washer. The saw blade was then sandwiched between the 2 faces and fitted to the circular saw. Result, one 'wobbling' blade which cut a channel in the wood to whatever width the washer / angle was.

[John Rumm]

Yup ;-)

There are quite a few spreadsheets and programs about that will help calculate the blade and offset angles required as well.

Not tried it, but there is a VB one here:

[dingbat]

Totally different thing, although strangely a wobble washer is one of the few things you can do with a table saw that's even more hazardous than making coving on it.

[Matt]

You could use a mitre saw instead, some of them have preset detents for just such an operation. The angles used are seriously wierd though!

[The3rd Earl Of Derby]

I don't think so.

1. there is no support long enough to hold the straight edge on whilst passing it through the blade.
2. you'd have to be ambidextous to hold and push it through the blade(if possible) and at the same time hold the blade down at the correct height.

[Matt]

You just lay the coving down face down with one edge flat against the back fence. With the blade at the correct angle and the cutting table rotated correctly you get *exactly* the result you are doing with a table saw. The coving stays still at all times and the cut is completed in seconds.

As I say, with the detents its a piece of piss to set up. Check out the online manuals on the Makita LS1013 if you still don't believe me.

[The3rd Earl Of Derby]

lol where talking different strokes here Matt.

[Stuart Noble]

Wobble washers used sensibly are perfectly safe. I once had a blade with precisely 7 layers of masking tape on each side which cut a groove to my specifications at a depth of about 12mm. The same thing at 25mm depth would have been slightly hairy maybe.

I'd say cutting coving would be a crazy thing to do. However you jig it up, you are essentially feeding timber to the side of the blade and the teeth aren't designed for that. Marginally safer on a radial arm saw I suppose but what kind of finish are you going to get anyway?

[LSR]

Norm Abram did this on "new Yankee Workshop" some time ago and he takes safety pretty seriously.

Anyway I'm not sure everyone follows what the OP was saying (ie you can create a cove by raising the blade just above the table and sliding the wood "across" the blade diagonally using one or two guide battens clamped to the table).

On my el-cheapo table saw I can create a dado by locking the fence out of parallel with the blade. I bet Norm can't do *that* with his Delta and Biesemeyer!

[Matt]

and in english?

[The3rd Earl Of Derby]

You are talking about cutting coving on a mitre saw,I'm talking about cutting a coving profile into wood.

Different strokes. ;-)

[Matt]

Now I have realised what you were doing. Cutting like that is bloody dangerous!

[The3rd Earl Of Derby]

Picture 4

[John Rumm]

It is safe enough providing that:

You clamp plenty of guide battens around the cove such that it can only move in one axis. You start with the blade fully retracted, and you only take very shallow cuts (by raising the blade) a small amount with each pass.

[dingbat]

Wobble washers are inadvisable because:

• You don't need them. Use a dado set with shims. The reduced error rate in mistaken too-wide grooves will pay for itself. 8-)

• They cut round-bottomed grooves. It's OK on narrow stuff, but for housings you produce a visible gap at the ends.

• They wobble. You're making what's potentially a large volume cut, you've taken your nice stable cast-iron cabinet saw and now you've turned it into something with the stability of a Happy Shopper tinplate special.

• They produce eccentric side-loads. If you slip with a straight dado set or a normal sawblade, then the saw always pushes in the same direction. You're usually OK with this, because it pushes against your push stick. With a wobble saw they bat things sideways, and that can lead to a throwing-the-workpiece-at-you incident.

I do it fairly often, but I'm only cutting decorative coves in cabinetry. I certainly wouldn't do it for the sort of big fixed millwork the Yanks are fond of cutting. If you need that, use a spindle.

Nor would I ever regard Norm as any sort of best practice to emulate.

[Guy King]

The message from Matt contains these words:

You're talking about cutting off a piece of existing coving.

Everyone else is talking about /making/ a piece of coving from stock by sliding it through the saw - in effect using the saw as an angled moulding machine.

[Guy King]

The message from Stuart Noble contains these words:

The main trouble with wobble-saws is they give a curved bottom to the cut. Not a problem on narrow dados but a right pain as they get wider.

[LSR]

Saws with a long-enough arbour to take a dado set are illegal in the EU.

[dingbat]

No they're not 8-(

(for one thing, I've got one)