My simple holddown clamp

[P.Passuello]

After searching this website and the internet for a holddown clamp for the Solsylva I am currently building I gave up and decided to design one myself.
I don't know if this has is a new design or not but it is simple to make, and very effective. A simple test with bathroom scales shows I can put up to 70lb of pressure onto the work being held down. The base of my router will have 1/2inch holes placed 6 inches or so apart which should allow any point to be reached with a clamp. The clamp simply drops through a hole and the washer and nut screwed up from below. It doesn't have to be tight as this will allow it to rotate to the required positioned and when the T-bar is tightened it will take up the slack. The clamping bar rests on the pin inside the body and it is then tightened down.The maximum thickness that can be clamped is limited only by the length of the threaded rod. Its maximum teach is limited by the length of the clamping bar, mine is 6 inches long. If you would like further info or have a better clamping system please post. As I said earlier I and still building and am will to change if something better can be found. These only cost $2 each to make and nothing special other than holes need to be added to the base of the router to make it work. I have already used them on my drill press with success.

I would value your comments good or bad.

Cheers
Peter

[Konstantin]

Interesting, thanks for sharing.
You used some rivets, right?


Konstantin.

[dertsap]

neat idea , the only thing i would add to the design are notches in the clamp bar so it will hug the pin it rests on in order to limit any chances of it slipping , other than that you ve got a brilliant idea there

[Geof]

It is a very nice idea; simple but very effective. The one thing you must take into account though is that when you fully extend the clamp bar as you show in the last picture the clamping effect is reduced by about 75%. The pin across your housing acts as a fulcrum and the end of the clamp is about four times further from the fulcrum than the screw is.

Making two sizes of housing so you can have a fulcrum further back when you want to reach out a long way will give better clamping.

[P.Passuello]

You used some rivets, right? Konstantin.

There are no riverts in this design. The swivel foot is held on with a 6mm diameter rod.The same rod is used for the pivot point and the handel on the T-Bar.

i would add to the design are notches in the clamp bar so it will hug the pin it rests on in order to limit any chances of it slipping

My original plan was to do as you have said but what I found is that even with 2 people pulling on it the bar will not slip out. The T-Bar bites into the clamping bar and this friction holds it tight. In all tests the piece being clamped started to slip not the bar. And that required forces so far above what is reasonable or even possible for a cnc machine to produce. The cuter would have snapped long before.

when you fully extend the clamp bar as you show in the last picture the clamping effect is reduced by about 75%. The pin across your housing acts as a fulcrum and the end of the clamp is about four times further from the fulcrum than the screw is.

Your 100% correct and your estimates. In fact I have made some longer body ones for my brother to use on his drill press for this same reason. I have redone the bathroom scale test and posted the photo here. This time I tightened the clamp down properly and packed the back clamp up to keep it semi level to reduce sideways pressure on the treaded rod. The clamp bar is fully extended so any pressure obtained hare can be considered a minimum. The results were 80kg or 180 lb of downward pressure (Thats more that I weigh ). I am unsure what pressure I will require but my first machine uses plastic spring clamps and only produce 12kg or 28lb and these seem to hold ok.

Thanks for your interest and comments guy's I appreciate them. If any of my tests or conclusions are wrong or you want more info or test let me know. I am only sorry I haven't finished building my new machine yet. I am waiting for motors from overseas so am using this time to get the clamps sorted. I am interested to see photo's of what other people use on their machines as it isn't to late for me to change my design.

Cheers
Peter

[CNCRob]

Pretty cool ideal. Thanks for sharing

[tobyaxis]

COOL CLAMP IDEA!!!!!!!!!! This can come in extremely handy. Gives some good ideas for an NC Table too.

Good Job!

Cheers!!!!!!!!!

[thkoutsidthebox]

Thanks again Peter. Can't wait to see pics of your finished machine.

[automizer]

T it isn't to late for me to change my design.

Don't change it this is a nice simple design. What is the time frame it takes you to put one of these together?

[P.Passuello]

DWhat is the time frame it takes you to put one of these together?

I made 6 in about 4 hours and most of that time was waiting for the bandsaw to cut the steel.

Cheers
Peter

[P.Passuello]

Can't wait to see pics of your finished machine.

Neither can I but this will have to tide you over.
I imagine you have no problem recognizing the design.
Need to spend a bit more time on it while I wait for my Xylotex steppers to turn up.

Cheers
Peter

[excelerate]

Great idea mate!!! after dealing with many "near miss" or bloody hands i made my boss buy "Kopel" clamps $1500au pair! same as yours but they use a cast ally block and a worm gear to screw the clamp down they work great really quick but way expensive. yours is also adjustible for lenght so even better. at a cost we all can have. (something to think of- if you use a cap screw and cut a stot in the side of your tube so a ball end allen key can get in when you use the clamp on a tee slot table you can fix it down or have it loose if you need to move it round. realy easy to use may need to use a thicker wall though