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Dovetail Cutter...Failed...

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John Stevenson:
Below is a drawing of an insert laid out in two positions.

The green insert has its leading edge [ green X ] on the centre line, it trailing edge can be seen to be greater that the swept yellow circle of the leading edge.

now if the insert is placed so it's seating is on the centre line as in the blue insert the trailing edge with always have clearance over the leading edge [ blue X ]



John S.

Darren:
Thank you for taking the time to show that John. So my biggest mistake (apart from the insert being too large in the first place) was positioning relative to the centre line then.

Very interesting. I wonder which line the cutting edge has the best advantage. What I mean is do we loose any efficiency having the cutting edge forward of the centre line?

I deff will have another go...... :D

John Stevenson:
No problem darren, it's a common mistake and the drawing has been on the computer for a while, it's alos been posted on a few forums, as i say it's a common mistake.

John S.

sbwhart:
Darren can you tilt the head of your shaper ?.

If you can tilt it over to the angle you want and feed it down to shape the dove tail, don't have to worry about having the form on the tool and taking a cut across its width.

Stew

Darren:
Hi Stew,
Yes that's how I did it last time, but it's not the easiest way to do it or to get right. I have to manually down feed while it's bouncing backwards and forwards. This does wonderful  things to accuracy...not...!!
Then there is matching both sides equally.....again not that easy to do.

And still the lifting of the clapper presents the same problems on it's return.


By having a form tool, the carbide tip is a perfect 60 deg...I only have to worry about feeding in one direction which is a simple matter and having set the depth it will be equal on both sides.
The actual size of the cut is no problem, shaper copes without a sweat and could easily manage larger I assume. Making the central slot not only reduces the cutting area but it also gives you somewhere to feed from. This is quite an advantage.

My only real problem with undercutting like this is the lifting of the clapper on its return stroke. I'm going to try to lock it. After all the carbide tip is identical on both sides so it should cut in both directions anyway. That might be an advantage? Forward stroke take the main cut, backwards stroke should take a skim off.

I will give it a go and report back, but it won't be today......got building work to do...... :bang:

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