Domino DF 500 Q malfunction

[TedBaker]

I have run into a very strange malfunction, which causes the mortise slot to, apparently randomly, be displaced left of center by approximately half the full domino width. Festool customer service says they have never had this problem reported before. Has anyone else experience this?

The first time it happened, I figured it was my own error, perhaps not paying attention to the pencil mark. The next slot was OK, and the next, but then it happened again, and again, sporadically. I ran a test on some scrap, and it varied, sometimes allowing me up to 10 correct slots, before the problem recurred. The failure has left me stalled now. I have owned the tool for years, but only used on a half doze or so projects. On those, up to now, I had experienced no problem.

 

[bobtskutter]

I've not experienced this issue with my DF500. Is the mortice still perfectly formed, is it the proper width? Can you put a domino in the incorrectly positioned domino? I can't see what's wrong in the photo you attached labelled "ruinedpieces" the picture appears to show a bunch of mortices on the wide setting.

You probably need to send the tool back to Festool.

Bob

 

[onocoffee]

Looking at your phot, I'm presuming that you mean it's "off" because the mortise on the right is completely to left of your marking line? This seems physically impossible if you have lined the mark correctly.
Peerhaps you could shoot some video of you making the mortise? That might help diagnose the issue.

 

[TedBaker]

Yes, the mortise is perfectly formed, but offset to the left to the center line on the tool, by approximately half the width of the mortise. The photo of the "ruined" pieces shows the result of two passes using the same pencil mark on the center line. The first slot was off center. When I repeated it, using the same center line, it was on-center. So, I glued dominos into the wrong-positioned slot. I will saw them off, and re-cut the mortise in the right position, once I can be assured that the machine will consistently cut the slot centered on the guideline. I am 100% certain this is not a case of user error, since I have now done dozens of cuts on scrap pieces. Most of them come out with the slot consistent with the centerline of the machine, but a few come out offset to the left, always by the same amount. Yes, I am sending the machine back to Festool, but am bracing myself for the possibility that they will only test it a few times, and declare that nothing is wrong with it.

 

[raylaray]

are the left and right ends of the slot skewed or angled when cut into the wood? If the slot is cut straight (i.e. the walls are perpendicular to the surface) then not sure how on earth the machine could cause that to happen without somehow the whole machine being positioned or moved to the left, given that the cutting bit pivots from the middle of the machine.

 

[luvmytoolz]

Yes, the mortise is perfectly formed, but offset to the left to the center line on the tool, by approximately half the width of the mortise. The photo of the "ruined" pieces shows the result of two passes using the same pencil mark on the center line. The first slot was off center. When I repeated it, using the same center line, it was on-center. So, I glued dominos into the wrong-positioned slot. I will saw them off, and re-cut the mortise in the right position, once I can be assured that the machine will consistently cut the slot centered on the guideline. I am 100% certain this is not a case of user error, since I have now done dozens of cuts on scrap pieces. Most of them come out with the slot consistent with the centerline of the machine, but a few come out offset to the left, always by the same amount. Yes, I am sending the machine back to Festool, but am bracing myself for the possibility that they will only test it a few times, and declare that nothing is wrong with it.

Instead of sending it straight in to Festool which as you note may or may not resolve the issue, do you have the equivalent of what we call Men's Sheds here in OZ where you could bring the Domino to and get some advice and have it tested there to see what they find?

The other thing to note is that if the Domino is being held in place correctly and not moving under use but it creates an offset mortise, the mortise itself must then be angled on the inside, as the sides can only be perpendicular if it's centred to the line, and therefore the marking on the Domino.

 

[grmaxx]

Looks like an operator error to me.

 

[bobtskutter]

The other thing to note is that if the Domino is being held in place correctly and not moving under use but it creates an offset mortise, the mortise itself must then be angled on the inside, as the sides can only be perpendicular if it's centred to the line, and therefore the marking on the Domino.

This is the logic of why I was asking if the mortice was perfectly formed.

It's physically not possible for the machine to create a mortice with parallel sides that's offset towards the left or right.

If the DF500 was being aligned with pencil marks and there was something wrong with the clear plastic that has the cross hair on it, could that cause the problem. I'm thinking this could be caused by parallax of trying to line up a pencil mark with the cross hair.

Is the DF500 fence being held against the workpiece correctly?

@TedBaker please can you post some photos of how you're aligning the DF500 to make the mortices?

Thanks
Bob

 

[TedBaker]

I figured some of you would not believe me, quick to dismiss the problem as operator error.
Sorry. Can't hold mortiser in place with less than two hands, and camera also takes two hands to operate.
In any case it would not provide any useful information or prove anything.
I have used this machine to make hundreds of similar mortises on other projects in the past, with no problem.
Even on this project, I can do between two and a dozen perfect mortises, right before encountering one of these anomalies.
I have been very conscious of alignment all along, especially since this problem cropped up.
All I can guess is that something is screwed up in the gears that cycle the bit left and right, so that it cycles from center to left and back.

 

[smorgasbord]

so that it cycles from center to left and back.

In that case the mortise would be only half width.

 

[luvmytoolz]

Sorry. Can't hold mortiser in place with less than two hands, and camera also takes two hands to operate.

Clamp it between two pieces of wood so the cutters extended and can safely operate without hitting anything, and then see if there's any deviation more to one side of the line.

 

[bobtskutter]

OK, not user error. I honestly can't think what could be happening and strongly suggest getting some video and sending it back to Festool.
Bob

 

[smorgasbord]

Can't hold mortiser in place with less than two hands, and camera also takes two hands to operate.

Cameras fit on tripods.

As @luvmytoolz says, clamp boards to stock on either side of the Domino fence so that it literally can't move side to side and see what happens.

If you really think it's in the gearing, then one thing to check would be if it varies with different mortise depths.