Over cuts on mounts.

[David McCormack]

I'm not talking about over cuts on the mount face but on the back. I've got my Ultimat Gold set up just nice but I do get over cuts on the back of the mount... that's normal right?

Anyway, just had some mounted work in on fairly thick board with very nicely cut windows but when I look at the back the corners don't show any signs of an over cut, not even a smidgen?

So is this a mount cut on a CMC or some magic I don't know about?

[poliopete]

As I have mainly used a Kimberly mount cutter over the years I can only comment on that and not yours David.

I must say I have never noticed over cuts at the back of the board and if so would that be a problem

Using my cutter I have got into the habit of "over cutting" large apertures so the drop out drops out cleanly without tearing the face of the board in the corners. On the other hand, I tend to slightly undercut the apertures for a small opening, say ciggy cards, and snick out the last fraction of corner with a sharp blade.

I know that does not answer your specific question but I need ait of a sit-down at the moment

Peter.

[poliopete]

That should read "a bit of a sit-down"

[kuduframes]

my Valiani Matpro, pneumatic cutter does not have any over or under cuts, same would go for any CMC I guess.
The action of the head id such that when you hit the engage button the blade enters the board exactly at the start of the cut and on release the blade comes out at exactly the end of the cut, then the head is rotated and same procedure is repeated, YouTube has several matpro videos which show this.
I cut up to 2.6 mm thick board on this.

[David McCormack]

Just to be clear, I'm talking about over cuts on the back of the mount which I get on my ultimat gold manual cutter and was wondering is that normal? I've never been bothered by it before until I noticed on the back of a mount cut by someone else that there wasn't a sign of over cuts whatsoever and I thought how is that?

Think I'll have a sit down with Peter, and a cuppa tea

[StevenG]

Speaking as someone who uses a Keencut - I've always had 'overcuts' on the back/bottom/underside - whatever it's called. On the visible top side it's fine. I also thought this was the norm

[David McCormack]

Thanks featurepiece, I feel better knowing you also have over cuts on your bottom

[StevenG]

Thanks featurepiece, I feel better knowing you also have over cuts on your bottom

Aye, the missus can get carried away some evenings

[David McCormack]

frankie_howerd.jpg (76.88 KiB) Viewed 7268 times

[kuduframes]

I also cut my teeth and other bits on a keencut gold....and overcuts on the back were normal.
Should have also said that the with the valiani the mount is cut face up.

[standrewsframer]

Overcuts on the back (but not visible from the front) are necessary when cutting a mount from the back. If a mount is cut from the front then there will be no overcuts at all (a slight incision mark left by the blade point of entry is a tell tale sign that the mount has been cut from the front - because of this cutting from the back generally gives the best result). Hope this makes sense.

[Steve N]

cutting mounts manually, you normally cut face down, so you will get overcuts on the back of the mount, because the angle of the blade is opposite the angle of the bevel, if you don't do overcuts, then the cut will not reach the corner on the face of the mount

CMC , normally cut from the front, you normally don't get overcuts on the back, but can still happen, if the angle of the cutting dge of the blade is different from the angle of the bevel

Done a very quick sketch

20190208_082423a.jpg (992.9 KiB) Viewed 7208 times

[David McCormack]

Nice diagram thanks

[grahamdown]

is it me or are both diagrams the same?

[Steve N]

Top one is cut face down on a manual mount cutter, the bottom on is cut face up on a CMC (computerised mount cutter), where the cutting edge of the blade is a similar angle as the bevel of the mount window, which is the exact opposite to the manual mount cutter, where the cutting edge is going in the opposite direction to the bevel of the mount window.
As I said, it was a quick skitch, and I had been in the workshop since before 4.30 am that morning