What's your hold down method?

[ger21]

I use cam clamps and have no issues with lifting. Mine are just made from 3/4" pine, with a 1/4" bolt into t nuts in the table.
I finger tighten the bolt, so the cam is close to the table, and push down on the part while tightening the clamp. As long as the cam doesn't lift, the part shouldn't either.

[TwoWheelMikee]

Kosh - good looking out on the hardware find. I have seen something similar used in the machining world, Mite Bite I think. I hadn't thought to use something like that.

It may be a misunderstanding on my part, but I was thinking that a cam clamp was something different. I was refering to an eccentric type clamp. Basically a circle with an off-center hole. As its rotated it will squeeze the part more. I saw them somewhere, I forget where, and made a handful myself of them to try out.

I can see how the tapered/beveled in the front area would solve my problems. I may have to give them a rip. I did some google homework after I saw your link and found a Veritas product, sold by Lee Valley, called the bench blade.

Veritas® Bench Blade - Lee Valley Tools



Sent from my SM-G930P using Tapatalk

[Kosh]

It may be a misunderstanding on my part, but I was thinking that a cam clamp was something different. I was refering to an eccentric type clamp. Basically a circle with an off-center hole. As its rotated it will squeeze the part more. I saw them somewhere, I forget where, and made a handful myself of them to try out.

Correct, I was just pointing out similar....

I can see how the tapered/beveled in the front area would solve my problems. I may have to give them a rip. I did some google homework after I saw your link and found a Veritas product, sold by Lee Valley, called the bench blade.

Veritas® Bench Blade - Lee Valley Tools



Sent from my SM-G930P using Tapatalk

Good find! I can use those on spoil board too (I have 20mm holes bored as well). Maybe have to give them a try.

[micknm]

Legacy Woodworking has a set of clamps designed to solve that problem (they push in AND down):

https://lwmcnc.com/product/lowpro-t-track-clamps/

However, I have yet to get them to work correctly (and as well as their demo videos). This maybe due to how poorly their T-nuts fit into my custom t-slots. basically, when I try to tighten them they just move back in the t-slot. I'm withholding final judgment until I've had some better t-nuts made... but so far they are just collecting dust (and not from the CNC machine!).

I have a set of these and love them. I'm using them with Incra T-track and have had no problems with them at all. They are pricey, but they work and hold the parts down to the table as claimed.

[harryn]

Hi, I am also looking for some suggestions.

I am planning to make some parts that are approximately 18 x 28 inches from 3/4 baltic birch.

The starting blank is nominal 20 x 30 inch x 3/4.

For part types that are all square edged, I would like to just have it router them to size by cutting all the way around all sides. That way I don't have to worry about if the blank is perfectly square or not.

Some parts need to be rounded over on all 4 sides. There are also some features and holes to be cut inside the parts.

One idea I have is to make a sort of L fence on the table that is roughly the length x width to help hold those 2 edges from lateral movement, but I am still not clear on how to do the rest of the clamping. A vacuum table is a possibility (but don't have yet).

I have toyed with the idea of drilling some holes through the boards and using plastic screws to help hold things down. The idea is that if the router hits the plastic screws it isn't a crisis.

Open to suggestions.

Thanks

Harry

[TwoWheelMikee]

Harry-

See my post above, I use alignment pins, painters tape and super glue (CA glue). The pictures below show the piece just prior to running the gcode, in this case i will be cutting 16 brackets for a shelving system for my office out of baltic birch plywood. I also showed the finished product. For this operation i have only used the tape and superglue method. I also use plastic screws to hold down work, as well as my spoil board. They work great, but i rarely use them now-a-days. I started using this method for engraving plaques and then used it for cutting out a pinewood derby car for my boy, that one made me a bit nervous. Now I use it for everything that has a flat bottom. I would recommend leaving about .004-.005 of an onion skin though. Saves the spoil board and allows for maximum tape adhesion, although not necessary if there is tape holding it down.. I do not use tabs at all, i hate sanding them off of the curved edges.

Sent from my SM-G930P using Tapatalk

[NotEZ2Beat]

I recently wrote an article about building clamps with your CNC.
You can read it here is you are interested: https://www.endmillsandmore.com/blog...you-have-a-cnc



Sent from my iPhone using Tapatalk

[fretman_2]

I also use painters tape when I can. Very simple, quick and strong.

[BrokenHorn]

I saw this on YouTube yesterday and think it’s a pretty neat system.

Granted I’m building my first CNC and have never used one so take my opinion with a grain of salt.






Sent from my iPhone using Tapatalk

[bill south]

Kosh;
What is the material your router table top is fitted with? Doesn't look like MDF to me! I'm getting ready to re-top my router so I'm researching top material and clamping methods (that is within my small budget).
Many thanks.
Bill

[harryn]

Harry-

See my post above, I use alignment pins, painters tape and super glue (CA glue). The pictures below show the piece just prior to running the gcode, in this case i will be cutting 16 brackets for a shelving system for my office out of baltic birch plywood. I also showed the finished product. For this operation i have only used the tape and superglue method. I also use plastic screws to hold down work, as well as my spoil board. They work great, but i rarely use them now-a-days. I started using this method for engraving plaques and then used it for cutting out a pinewood derby car for my boy, that one made me a bit nervous. Now I use it for everything that has a flat bottom. I would recommend leaving about .004-.005 of an onion skin though. Saves the spoil board and allows for maximum tape adhesion, although not necessary if there is tape holding it down.. I do not use tabs at all, i hate sanding them off of the curved edges
Sent from my SM-G930P using Tapatalk

Hi, thanks for the response. For some reason the photo wasn't coming through until today.

I think that I am missing something on your setup, especially referring to "onion skin". Is the final cut depth setup to be just a bit shy of full cut depth - leaving behind a little more to be hand cut with a knife? Isn't that approach likely to leave the risk of messing up the top laminate layer?

What do you do if you start with a board that is "almost the right size already (example previously cut on a table saw to perhaps 1/2 inch oversize) and want hold it down to route an edge around the outside, not just a straight cut, but for instance a round over? Or do you just avoid being in that position by always cutting inside of the board edge?

[Kosh]

Kosh;
What is the material your router table top is fitted with? Doesn't look like MDF to me! I'm getting ready to re-top my router so I'm researching top material and clamping methods (that is within my small budget).
Many thanks.
Bill

It really is just MDF.

[TwoWheelMikee]

Hi, thanks for the response. For some reason the photo wasn't coming through until today.

I think that I am missing something on your setup, especially referring to "onion skin". Is the final cut depth setup to be just a bit shy of full cut depth - leaving behind a little more to be hand cut with a knife? Isn't that approach likely to leave the risk of messing up the top laminate layer?

What do you do if you start with a board that is "almost the right size already (example previously cut on a table saw to perhaps 1/2 inch oversize) and want hold it down to route an edge around the outside, not just a straight cut, but for instance a round over? Or do you just avoid being in that position by always cutting inside of the board edge?

Harry,

The onion skin is exactly as you called it. Generally, it's four to six thousandths (material dependent) left at the bottom of the material after a cut out operation. I've seen it used extensively when a vacuum table is used to hold the stock down. The thought being that leaving the material would help to preserve the vacuum, depending on the material the benefits may be arguable. I use it as an alternative to tabs while cutting out multiple pieces from the same stock. I go this route for several reasons... first, the onion skin provides plenty of retention of the piece being cut out. Granted I save the cut out operation for last and only really accomplish the final finishing pass on the perimeter while the onion skin is all that is holding the piece in place. So no aggressive toolpaths that may impart a lot of side load into the piece. Second, because I use the tape/CA glue method of holding the work down, I prefer to keep the tape intact until the end and I peel it off. This gives me a slight warm fuzzy that the sheet or panel being cut isn't going to be slung across the shop. and lastly, I'm lazy by nature and I do not like trying the blend the tabs in by hand. The onion skin allows for a quick swipe with a utility knife and the piece is free. Anything left on the edge will be sanded away with no additional effort, other than the normal sanding. You could even just press the part out of the sheet/panel stock, once to get the process dialed in. But this could lead to some nasty tear out if you are not careful.

To your question about marring the bottom laminate layer on plywood, I actually find that the onion skin helps to prevent this. My machine does not have the muscle to push a compression bit at the minimum DOC to engage the flutes in both directions so I generally use a down-cutting bit and save the last couple of thousandths to do by hand and get a better finish then if I use any of my power tools, especially on plywood. As I mentioned earlier though, a careless removal of the piece can quickly tear out the pieces.

About using pre-sized material. I would not use the onion skin method. I do a lot of plaques or similar items and my work flow is close to what you described. I will rough them in at the table saw and individually tape/CA glue them to the CNC table top. I will accomplish the vcarve and pocketing as required and then dress the edge how ever the job requires (round over, ogee, etc). The final edge rounding operation will cut through the material entirely. Since it's only one piece, I do not need to use the onion skin method. Side note: using the tape does lift the material about .009-.011 of an inch off of the table which helps preserve the spoil board in some cases.

Hopefully that helps, I apologize for the length.

[CitizenOfDreams]

One of my favorite methods is gluing the workpiece to a sacrificial fiberboard square with silicone. That gives me two advantages:

1. I can cut a part out without using tabs.
2. I can use the entire stock with very little waste.

[harryn]

Harry,

The onion skin is exactly as you called it. Generally, it's four to six thousandths (material dependent) left at the bottom of the material after a cut out operation. I've seen it used extensively when a vacuum table is used to hold the stock down. The thought being that leaving the material would help to preserve the vacuum, depending on the material the benefits may be arguable. I use it as an alternative to tabs while cutting out multiple pieces from the same stock. I go this route for several reasons... first, the onion skin provides plenty of retention of the piece being cut out. Granted I save the cut out operation for last and only really accomplish the final finishing pass on the perimeter while the onion skin is all that is holding the piece in place. So no aggressive toolpaths that may impart a lot of side load into the piece. Second, because I use the tape/CA glue method of holding the work down, I prefer to keep the tape intact until the end and I peel it off. This gives me a slight warm fuzzy that the sheet or panel being cut isn't going to be slung across the shop. and lastly, I'm lazy by nature and I do not like trying the blend the tabs in by hand. The onion skin allows for a quick swipe with a utility knife and the piece is free. Anything left on the edge will be sanded away with no additional effort, other than the normal sanding. You could even just press the part out of the sheet/panel stock, once to get the process dialed in. But this could lead to some nasty tear out if you are not careful.

To your question about marring the bottom laminate layer on plywood, I actually find that the onion skin helps to prevent this. My machine does not have the muscle to push a compression bit at the minimum DOC to engage the flutes in both directions so I generally use a down-cutting bit and save the last couple of thousandths to do by hand and get a better finish then if I use any of my power tools, especially on plywood. As I mentioned earlier though, a careless removal of the piece can quickly tear out the pieces.

About using pre-sized material. I would not use the onion skin method. I do a lot of plaques or similar items and my work flow is close to what you described. I will rough them in at the table saw and individually tape/CA glue them to the CNC table top. I will accomplish the vcarve and pocketing as required and then dress the edge how ever the job requires (round over, ogee, etc). The final edge rounding operation will cut through the material entirely. Since it's only one piece, I do not need to use the onion skin method. Side note: using the tape does lift the material about .009-.011 of an inch off of the table which helps preserve the spoil board in some cases.

Hopefully that helps, I apologize for the length.

Thank you for the explanation. The length and details were very useful, at least for me.

[VGcustomshop]

Cool hold down setup!