Corner Notcher Mystery

[awemawson]

A recent addition to my sheet metal working kit is this Kingsland W3 Corner Notcher, reputedly able to cut a corner notch of 75 mm x 75 mm from 1.6 mm plate.

It would be extremely usful if it did what is says on the tin, but it doesn't 

[awemawson]

This is potentially very useful when folding up trays and boxes.

The massive 75 mm square punch is foot driven and arranged by having the cutting face tilted, so that a progressive cut is made. First contact is at the rear, with the shear action progressing forwards to the corner, then from left to right across the other face of the corner.

Now the punch was pretty blunt and someone looked to have titivated it with an angle grinder  However I brought it down parallel to what looks to be the original face giving clean cutting edges. As the face tilts in two directions but is a plane, it was a tricky bit of setting up.

It now cuts very happily on its first fore & aft edge, but with the 1.5 mm plate I've been using it is virtually impossible to progress the cut on the side to side direction.

Now if you look at the two sides of the cutter block, they have markedly differing angles to them.

[awemawson]

Now the fore & aft cutter changes in height by 11 mm in its 75 mm length, whereas the side to side one only changes by about 2.5 mm

Surely this cannot be correct 

Anyone with experience of these things, or has one who can make comparative measurements for me?

I have a feeling I may need to dig out some of my hoard of O1 tool steel blanks and make one with equal angles, but it's a bit of a bind to have to go to that trouble

[RussellT]

What do the other two edges look like?

Is it possible that the cutter could be mounted in the wrong position?

Russell

[shipto]

I was just about to suggest it was in the wrong way, I havent ever used a non hydraulic one but the ones i have used (as far as i can remember) tend to have the leading point pressing out the center first. I believe this would stop the tendency for the cut to push the work away from the stops.

[shipto]

This page seems to show what i suspect is the correct position http://www.cottandco.com/lots/fj-edwards-corner-notcher-on-stand click on the last picture

[awemawson]

Now that is an interesting suggestion which I will investigate, and I thank you both. However the angles are set in stone (or rather tool steel!) and even if I can twirl it round they will still be unequal.

[awemawson]

A bit of progress. It turns out that a firm under the name of Kingsland is still operating out of Sheringham in Norfolk, and although no-one there has ever seen one of these foot operated notchers, a helpful chap in their service department managed to dig out a pamphlet with illustrations and scan it for me.

Seems that the direction of cut is set the same as mine and that the differing angles are original, and he was as puzzled as me how it ever worked on the side to side cut 

[RussellT]

This link has some pictures of another one.

http://www.cottandco.com/lots/kingsland-w3-corner-notcher---1

The pamphlet you've put up suggests you can do square notches - which suggests a third cutting edge - but the table looks different so I'm not clear that it's the same machine.

Russell

[awemawson]

Russell thanks for those pictures - interesting as they imply the cutting action starts at the point of the corner which is contrary to the manufacturers picture (which is how mine is set up). Also the angles look similar in steepness on both faces.

The .jpg I posted of the pamphlet is much lower resolution than the original .pdf that I have, and looking closely at the pictures the square notcher and triangle notcher are alternative punches that were available

[shipto]

I would suspect that whoever owned the one in russels link figured out that it doesnt push the work out that way. Although the first bit might need a fair bit of force in 1.5mm sheet.

[mechman48]

It would suggest the shear force starts at the rear left of the blade & progresses toward the centre point where the second shear force on the front takes over from the side hence giving you only one blade edge shear action at any one time, the stops would prevent the plate from moving either way, imagine trying to cut initially from the centre point on two sides, the amount of shear force required would be enormous     ,  that's my 2 penn'orth anyway.

Cheers
George

[awemawson]

I've resolved to make a new punch block with the same angle on the front shear as is currently on the fore & aft shear. Just need to find the roundtuit 

[Arbalist]

This link has some pictures of another one.

http://www.cottandco.com/lots/kingsland-w3-corner-notcher---1

Russell

This one looks right to me, cutting the corner first as Shipto says. I think the reason they are at different angles is to reduce the pressure required (as they are cutting at different rates) to complete the cut. I think yours is just fitted the wrong way round awemawson.

Making a new one with both angles the same is unlikely to improve things.

[Arbalist]

This one is similar to yours. And has the same angles?!

http://www.baileighindustrial.co.uk/sheet-metal-notcher-sn-f16-fn

If you click on the video it shows it cutting back to front first (then left to right) so perhaps yours is not mounted back to front?

There seems to be two different approaches to these corner notching machines but in both cases they use different angles. I can understand this when the machine cuts the corner first but not sure why if it uses the other cutting method!
Perhaps the blade can be rotated for some reason???

[shipto]

This one is similar to yours. And has the same angles?!

http://www.baileighindustrial.co.uk/sheet-metal-notcher-sn-f16-fn

If you click on the video it shows it cutting back to front first (then left to right) so perhaps yours is not mounted back to front?

There seems to be two different approaches to these corner notching machines but in both cases they use different angles. I can understand this when the machine cuts the corner first but not sure why if it uses the other cutting method!
Perhaps the blade can be rotated for some reason???

Your quite right I am wondering about my advice myself now