Domino: Setting Specific Plunge Depths

[Powertoolman]

This is a follow-up discussion to Flowboy’s “Success!!” thread. I started this as a new thread because Rob’s original discussion was dealing with miter joints, and this discussion is about limiting the depth of plunge on either miter joints or butt joints.
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Today I had to make a drawer for my neighbor, and the material that I use is 1/2-inch Appleply, which is actually just 7/16 inch (11mm) thick, high density maple plywood (it’s like Baltic birch, but a much higher grade). In order to use Dominos, I had to limit my depth of plunge to 3/8 inch (10 mm), so I decided to try the idea I presented to Rob earlier, and it worked beautifully.

Because this material is only 11 mm thick, the Domino will bore all the way through on a face-side mortise. I needed to limit my depth of plunge to 10 mm, so I created the depth-limit tubes I discussed hypothetically in a previous dscussion.

Here is what I learned:
I used a scrap piece of thin-walled CPVC that I had laying around the shop, and placed it over the linear rail of the Domino. Mine had an ID of 18 mm, but it could have been as small as 14 mm and still fit over the linear rail.

It is important to not use any type of material that will scratch the stainless steel linear rail, as this will score the bronze bearings inside the motor housing. This is why I chose CPVC.

The length of the tubing needs to be 28mm minus the depth of your plunge. So in my case, I needed a 10mm plunge depth, so my tube needed to be 18 mm long (28mm - 10mm).

I then labeled the outside of the tubing with the depth of plunge it gives me, and what I use it for (label not shown in picture). This way I could have several of these pre-made for specific depths. For example, the mating plunge depth for this example needs to be 21 to 22 mm, but Domino only has 20mm and 25mm settings. So I would also have another tube that was 7mm long for the mating plunge.

By the way, I used my Radial Arm saw with a fine-tooth blade to cut the PVC tube because it is the most accurate saw in the shop and will cut this without leaving burs.

[Auld Bassoon]

Neat PTM!

I've been using various thicknesses of spacer block on the plunge face to cut shallow mortices, but your method is more elegant.

Are you using one depth of stop collar for each of the two linear rails, or just the one?

[Powertoolman]

It's only necessary to put a collar on one rail, and the numbers used above are for using the left rail. Even the built-in depth stop operates on one rail.

It just dawned on me as I was typing this that I screwed up the math yesterday. The length of the collar should be 28mm minus the desired plunge. With a 28mm collar, you will just scuff the surface, and using no collarat all will plunge to 28mm. I will edit the mathematics in the post above to avoid confusion.

[Flowboy]

Hi PTM,
It certainly does look elegant. Some points if I may.

1. You have shown the plastic collar, but not the starting depth to which you are cutting. I assume you set to 28mm.
2. If this is the case, you would require a collar for every desired depth reduction. I foresee a beautiful dovetailed box with a set of organ pipes within.
Also, you would need to a) unplug the Domi, b) Split the Domi, c) remove the collar, d) rejoin the Domi and e) replug the Domi everytime you want to change the cut depth.
3. You have not shown the finished mortise or proof of its depth.
4. You have said this works on mitres, but there are none in evidence. Can you show a cut into a mitre of 10-12mm in timber, rather than Chipboard showing the Domi before cut, mounted for cut and resultant mortise, with some form of confirmation of depth?
5. Maybe you could use strips of adhesive foam door insulation inside the collar to reduce the chance of dmage to the rail.

These are just my way of assessing the data to come to a rational decision in a scientific way. Pleas don't take offence.

Regards

Rob

[Powertoolman]

Rob,
I am not sure we are trying to accomplish the same thing. I thought we were but I may have been mistaken as to what you were trying to accomplish in your previous discussion.

My immediate need was to accurately plunge to a depth outside of the normal Domino depths (less than the normal minimum) so that I did not plunge a hole completely through the side of a drawer box or other workpiece.

Making a drawer box is something that I will do on a frequent basis, so I need a reliable and repeatable method for limiting the plunge depth to 10 mm. This collar gives me the most accurate and foolproof method of doing this. I doesn't matter what other settings Domino is set to, I cannot accidentally plunge through the side of a drawer box with this collar installed. However, this is not something I would be using during normal usage. In most cases, the standard Domino settings are sufficient.

Regarding your questions:
1) Regardless what the Domino is set to, the collar will prevent over-plunging (see question #2 too). If Domino is set to a shallower plunge, then that is what you will get, but you cannot accidentally over-plunge and make a hole all the way through your stock.

2) My method is not based on a reduction from the factory settings, but as an absolute value. It doesn't matter if Domino is set to 12mm or 28mm, my collar stops the plunge at 10mm.
Yes, I do need to install a new collar for each setting I desire, but this is not somthing I would be doing on a regular basis.

3) I didn't realize I needed to prove anything. I have the test-board sitting next to my desk as I write this, and I have measured the plunge depth with a dial caliper (0.398 inch), but I'm not going to take a new picture just for this purpose. Take it at face value, or leave it.

4) Yes, it will work with miters, but YOU are the one that needs to decide what depth you want depending on your application. The desired plunge depth will depend on the miter angle, fence height, and material thickness. This is not something I can calculate for you.

5) Stainless Steel is extremely hard. I don't believe it is necessary to go to this extreme. The only reason I mentioned scratching the rails in the original message is so someone didn't use a hard steel tube as their collar. You are not going to scratch stainless steel with a plastic collar.

[Flowboy]

PTM,

I think probably we are working with different goals in mind.
I don't take things at face value, too many chances of smoke and mirrors.
I don't believe the system will work for mitres using a 45 degree mitre on a piece of timber 10mm deep to produce a mortise of 5mm depth. You state categorically it will work with mitres, but haven't shown it. Like your statement "take it at face value, or leave it", I'll say Prove it or say it doesn't work.

Rob

[baltic]

Hi PTM,
Your PVC depth control method is and excellent idea, and very clear!
Thanks for your positive contributions to the Festo "domino" forum. Look forward to more suggestions,
Did you see my thread regarding the slide feed issues?
I don't think that the PVC would damage the slides?

Cheers,
Gary.

[Lignum]

If i have Peters permission to get of my soap box for a second to say that is a fantastic idea and im of to get some PCV in the morn:D Well thought out PTM:D

[Powertoolman]

Yes Gary I did notice your previous discussion about the slide feed. As a matter of fact, it was your discussion than made me think about the slides when I commented about using the PVC. Moreover, your comments have lead to better information for others to see. Thank You.

[Flowboy]

Hi PTM,

An apology.

Your system works beautifully regardless of the depth set on the Domino. New collars are so easy to make they are disposable or useful as tiny little plant pots. Still want to see it work on thin mitred stock, but may as well try it myself. Pics like I would have liked to see below. 8mm domi cut in 11mm Blue Gum.

Regards

Rob

[ozwinner]

Not my area, as I dont have one of these machines, but why not set up something similar to PTM with a thumb screw so you can set and forget?

Al :)

[patr]

PTM

An elegant solution, well described and very cost effective!

Good to see another disciple of the KISS principle (Keep It Simple Stupid) which allows even a numpty like me to understand and appreciate.

Pat



Removing the restrictive collars from the Frogs legs allowed a far greater leap. Vital for Stage 1, the treacherous slope of El Misti.

[Flowboy]

Hi PTM,

Another apology and a very big thanks!

I have just set up the domino with a restictive collar carefully removed from a passing frog and it's obvious it (both the domino and frog) will do what is required. I'll post pics tomorrow if anyone is interested.

Once again sorry and thanks.

A very skeptical by nature,

Rob

[TEEJAY]

a terrrible stutter you've got there Rob :D ;)

[scooter]

Good onya Rob :)