Homemade round benchdog design - will it work?

[Assaf Oppenheimer]

Hi all,

TL:DR will this design for a round spring loaded bench dog work?

I have FINALLY finished the front top of my workbench! I have some holes drilled out at a 2° lean for the tail vise and I was thinking about the benchdog design. A commonly read complaint about the spring loaded round dogholes is that over time the spring can groove out the hole in the bench preventing it from pivoting and reducing the grabbing power of the hole. I don't know if the threat is real, only that I have read it a bunch of times.
as a result of that and rainy weather that prevents me from getting work done I tried to come up with an alternative.

I would love to hear the creeks thoughts on the design - basically would it work, if no, why not.
the design is my own, but if anyone feels like it is worth it, they are free to use it non commercially.


anyway here it is:
476559
The idea is to wedge a dowel into the hole in the center of the benchdog that is slightly larger than the drilled hole (say a 1/64") this should cause the "legs" to seperate and act as the spring against the sides of the hole. the dowel would then be flushed with the dog.

any *constructive* thoughts?

[Jim Koepke]

If you can find a source of bullet catches they are easy to make.

Years ago Lee Valley had a clearance on catches without latches, that is where mine were acquired.

See it here > https://sawmillcreek.org/showthread.php?207672

The cut away at the top is at a slight angle.

Search Amazon if they are in Israel for bullet or ball catches. It looks like some might be available for ~50¢ each USD.

jtk

[Assaf Oppenheimer]

Bullets look much easier

what size should I get? I can get them on Amazon

[Luke Dupont]

Looks like it might split, or just make the dowel too big to fit in the hole. I also don't think you'll get much spring action.

I always wondered if you couldn't do the same with a round dog as you do with a square one: rip a piece out of the side about 1/8" thick, and then plane an angle into the bottom face of the dog and glue it on to make a spring. But then nobody does that for some reason, so I have to ask myself "why not."

I also would like a design that avoids using bullet catches, because it's always difficult to find such specialized hardware, especially overseas.

[William Fretwell]

One of the round dog issues is the depth for the flat face. Worst case you halve the strength of the dog. As you move the face forward a little the strength improves greatly with little loss of width. You can draw a graph if you like of end grain area for each mm forward of half way. The strength gains are substantial in the middle of the dog. All the round dog users I’ve seen come forward from half way. 65% seems a good number.

One benefit of round dogs/holes (perhaps the only one), is they are easy to make and replace!

[Jim Koepke]

Bullets look much easier

what size should I get? I can get them on Amazon

Mine are 1/4" if my memory is working. I'll try to remember to check today.

There are advantages to round dogs and square dogs. As an example what is good for one might not be good for the other. A square dog will not turning in use can be an advantage. A round dog being able to turn for round or odd shaped work is also an advantage.

Many bench accessories are made to fit in round dog holes.

Square dog holes can be used to set up a make-shift pole or treadle lathe.

It is fairly easy to add round dog holes.

jtk

[chuck van dyck]

Old bandsaw/jigsaw blades work pretty well.

Edit: sorry I missed the part about trying to avoid the spring wearing the doghole. I wouldn’t worry, that seems a lot more like theoretical/arm chair woodworking than actual woodworking.

I have seen your design before though, only rather than a dowel, they just used a small shim.

[Phil Cyr]

To get spring action I think you need further relief past the hole with the dowel. The dowel can't exert a load on the legs that extend past it, so all the force of the dowel is going into creating a split. If there are two holes with a separation you can exert the load on the intermediate span and attempt to release the splitting force with a second hole.

I tried it this morning. It kind of works, but honestly I would probably get proper springs.

476604

[James Pallas]

It will most likely work for a while. Depending on how often the same position on the bench is used the more the wood fibers will be crushed. The wedge type where you tighten with a screw will probably work longer, but with another thing to do. Give it a try see how well it works. It may work really well for your method of work.
Jim

[Jim Koepke]

Bullets look much easier

what size should I get? I can get them on Amazon

The small drawer holding my bullet catches/ball catches also had an old note:

476610

These may be different in Israel. The ones available to you may be metric. The drilling with the brad point bit was to make a recess for the flange at the top of the brass casing.

jtk

[Thomas Wilson]

My round steel bench dogs have a longitudinal wire spring that compresses into a groove as the dog is inserted. The same idea should work for wood. The groove leaves most of the dowel for strength.

[Assaf Oppenheimer]

Looks like it might split, or just make the dowel too big to fit in the hole. I also don't think you'll get much spring action.

Thanks, I was considering using a spokeshave to thin out the middle if it bulges. I didn't consider it splitting - you may be right


I always wondered if you couldn't do the same with a round dog as you do with a square one: rip a piece out of the side about 1/8" thick, and then plane an angle into the bottom face of the dog and glue it on to make a spring. But then nobody does that for some reason, so I have to ask myself "why not."

Round dogs would require a round spring. the middle would be much thicker than the sides and not flex well

[Assaf Oppenheimer]

I don't buy much woodworking equipment in Israel.

shops here are generally overpriced, and lack decent customer service. since I am "trained" (self taught) from Youtube, books and this site I am almost strictly SAE with my woodworking. It's easier when most of my tools are SAE
I ordered some from a well known chinese website. 3/8"

Thanks for the help though

[Assaf Oppenheimer]

wow thanks a lot for that feedback!