Domino mortises - Clean vs ragged

[4nthony]

This has been happening to me enough lately that I thought I'd ask for some advice. I'll get a clean mortise on one plunge and a ragged mortise on the next. I'm using a Domiplate and plunging vertically. I feel like I'm using a consistent plunge speed and there's enough pressure on the plate and fence so the tool feels pretty secure and I don't feel any tipping/movement.

Could I be plunging too fast/slow? Is there some tipping or movement that maybe I'm just not feeling? I'm sure I just need more practice as my technique feels consistent but I'm sure it's not.

Suggestions appreciated!

- The picture shows two different mortise widths but this happens with all widths.
- The edge stop was used for the left mortise; the right was free

Thanks!

 

[squall_line]

Does it happen on all bit sizes, or just this one?  How old/young is the bit?  How clean is the bit up the sides?  Any chips?

If it's across the board, then I'd guess too fast before I'd guess too slow.

 

[ChuckM]

Agreed. The ragged edges shouldn't be a result of the plunges being too slow.

If the bit was free of damage or defect, tipping could be a potential cause.

Did you wait until the bit was completely retracted before withdrawing or moving the machine?

 

[4nthony]

Does it happen on all bit sizes, or just this one?  How old/young is the bit?  How clean is the bit up the sides?  Any chips?

If it's across the board, then I'd guess too fast before I'd guess too slow.

I've only used the 5mm bit that it came with and it looks clean. I didn't notice any chips or other damage on it. The bit has probably cut less than 300 mortices so I don't think it's the bit/tool but rather my technique. I'll find some time this weekend to do a bunch of test plunges in some scrap and see if I can get more consistent. There's probably some tipping or movement happening that I'm not noticing through the vibrations of the tool.

I noticed in the Seneca video, he's holding it by the knob, but I tend to hold mine using my thumb like the left picture.

Did you wait until the bit was completely retracted before withdrawing or moving the machine?

Yes. It's certainly possible, but that's one thing I'm pretty aware of as I've screwed up enough board faces moving a plunge router before retracting it.

 

[ChuckM]

Please hold it by the machine's T-handle (front) for stability when making vertical cuts.

 

[4nthony]

Please hold it by the machine's T-handle (front) for stability when making vertical cuts.

If I grab the T-handle, my thumb gets in the way of the plunge. It feels secure but I don't have the clearance. I've been kinda pinching with my thumb pressing into the Domiplate and my fingers pressing down on the t-handle, which feels less secure but allows me to plunge w/o hitting any fingers.

When I hold the ball of the Domiplate, I feel like I could potentially get lift on the plate if I'm not applying some forward-horizontal pressure while plunging.

 

[Vtshopdog]

Your photos show cuts in BB plywood.
Do you have similar ragged cuts when mortising in solid stock?

 

[4nthony]

Your photos show cuts in BB plywood.
Do you have similar ragged cuts when mortising in solid stock?

All of my Domino projects have been using BB or MDF so I haven't plunged into hardwood yet. I've got some scrap oak I can use to make some test cuts. I'll give it a try and see what happens.

 

[ChuckM]

Please hold it by the machine's T-handle (front) for stability when making vertical cuts.

If I grab the T-handle, my thumb gets in the way of the plunge. It feels secure but I don't have the clearance. I've been kinda pinching with my thumb pressing into the Domiplate and my fingers pressing down on the t-handle, which feels less secure but allows me to plunge w/o hitting any fingers.

When I hold the ball of the Domiplate, I feel like I could potentially get lift on the plate if I'm not applying some forward-horizontal pressure while plunging.

Got it. You have big hands/thumbs, unlike me. I have issues with my thumb getting in the way somewhat only occasionally.

Your second way of holding is definitely far better than the one shown in your previous photo.

I always wonder why Festool didn't design a bigger fence and a bigger support bracket as the problem you encountered must have been known to them if they did enough user tests. A bigger support bracket is also helpful when mortising vertically on a flat service. I made a cradle jig to do just that. I've also made a front vertical handle to replace the T-handle when necessary.

 

[Crazyraceguy]

Just my 2 cents, but I would never hold it by the knob that is out there hanging in space. (the right side of the pic) There is no stability there. The wrap-around grip in your later photo is much better. The key is to find what works for you though.

Veneers can just be touchy no matter what you do. You could have perfect technique every time and still get that ragged fiber or two. MDF, particle board, and plywood all act slightly different, so your plunge speed may need some adjustment when swapping between them. Bit size and even age can contribute to this too.

Above all though, do not get these bits re-sharpened, even if you can find someone who can/will do it.
I have done it, because of easy access to it, and there is an issue with the results.
They did a fine job, the bits cut well, but the sharpening happens on the end (like a drill bit). With a drill this is not a problem, but the Domino bit oscillates at a specific angle. When the bit is shorter, the resulting slot is not as wide. On the tight setting, the Dominos do not fit. You can force them, or sand the ridges off of the side, but that gets laborious, or just use the wider setting. None of these work-arounds are worth the trouble. As long as you stay away from metal objects, the bits last a long time, so a genuine replacement makes better sense. Keep the old one for something that may seem sketchy.  [unsure]

 

[squall_line]

Just my 2 cents, but I would never hold it by the knob that is out there hanging in space. (the right side of the pic) There is no stability there. The wrap-around grip in your later photo is much better. The key is to find what works for you though.

Some insight on the knob on the Seneca plate in case anyone is curious why it's hanging out there like that:

The domiplate was designed to create an easy reference distance for centering dominoes on either 1/2" or 3/4" stock without having to set the fence depth or worry that the fence will come loose and "drift".

As a result, the Domino machine itself is used "upside-down" compared to using the stock fence when plunging horizontally; the knob takes place of the knob on the stock fence.

 

[usernumber1]

i get this tiny tearout all the time on junky plywood veneer.
never thought much of it. if the bit is dull you'd know and if it's technique it doesn't really matter since the domino fits fine

i do not get it all the time and definitely not on solid wood, even soft pine cuts clean.

i tried a few times to just plunge super slow and that seemed to help. i think it happens with the beginning of the plunge, when the front of the bit cuts the veneer.

 

[Birdhunter]

I agree with the tearout happening as the bit is entering the wood. Could be dull bit or technique. Since the tearout doesn’t happen every time, I’d guess technique plus soft wood.

 

[bertv]

The fasteners on the Domiplate tend to shake loose somewhat if not tightened well. I always check after doing a few mortises.

 

[ChuckM]

I checked several of my plywood mortises, including this known crappy ply sheet (image). No tear-outs. I'd say it's most likely a technique issue, which could be due to tipping, plunging too fast (symptom: chatter sound), or moving the machine before the bit completely exits the mortise.

 

[Crazyraceguy]

Just my 2 cents, but I would never hold it by the knob that is out there hanging in space. (the right side of the pic) There is no stability there. The wrap-around grip in your later photo is much better. The key is to find what works for you though.

Some insight on the knob on the Seneca plate in case anyone is curious why it's hanging out there like that:

The domiplate was designed to create an easy reference distance for centering dominoes on either 1/2" or 3/4" stock without having to set the fence depth or worry that the fence will come loose and "drift".

As a result, the Domino machine itself is used "upside-down" compared to using the stock fence when plunging horizontally; the knob takes place of the knob on the stock fence.

Oh yeah, I am aware of the "correct" use of the plate and knob in it's commonly used position when registered on the face of the material. I was meaning that it was unstable when hanging out there in that edge position.