[MiniMe]

I watched this video (and many others) and this seemed reasonable and easy so I thought I would build it.

In the below picture, highlighted in blue is my base which is 1/4" thick, three layers, birch plywood (relatively flat)
On top of it I have an 11 layers piece of Baltic Pywood (3/4") and two Bessey STC HH70 toggle clamps . The clamps are an overkill for this sled but they are there on a temporary basis I can remove them and use them where I need (they are installed using insert screws)

To me this design has a flaw and that is that if you are using a thin base (to avoid having to lift the bit too much) the clamps will push the base downward and the base will bend or the base will be pushed upward putting pressure on the screws that connect the base of the sled (blue) to the base of the clamps (purple)

Should the base be much thicker ? I did try to adjust the pressure the clamps put on the piece of wood in order to avoid the base bending but it ends up with the wood that you are routing getting lose

My sled is longer but that is because later I plan to get it up to this design

 

[MiniMe]

also the design in the second picture seems to have an issue as well. It seems that the acrylic screen/cover is used to run the sled against the fence. The piece to be routed is sticking out of the base and it has no back support (unless a sacrificial piece is used).
I am considering the below design in which the side of the sled situated next to the fence and ahead of the purple
clamp base (yellow block) is cut in such away that would not allow the bit to reach the base of the sled because there is nothing there
(that yellow block was cut out)

 

[MiniMe]

No really
So what is wrong with it...

 

[MiniMe]

So the two problems I am seeing are real, itis not my imagination.
#1 the router base needs to be thin in order to not to have to lift the bit too high
#2 using those toggle clamps is not a great idea since they tend to push the thin base away from them and since this is thin it will bend.

Two contradictory requirements

I looked at that bit extension and a good one could be quite expensive. Besides that you need two sizes 1/2 and 1/4

 

[MiniMe]

Your base is not thin either -are you using a bit extender ?

 

[MiniMe]

Looks like it should work fine, Mine does. It’s only 1/4…

Not sure why mine doesn't -I am staring at it and I see the plywood bending

 

[MiniMe]

I went to Ikea this morning and I noticed they have various trays and cutting boards made of bamboo.
In particular the one below could be used (the slotted piece) -cost is 12-13CAD, the thickness is a little bit over 1/4"

 

[MiniMe]

Here is how much I can lift my router - do you think I can/should go with a nominal 1/4 or 5/8 or even 1/2 plywood for the base of the coping jig? Would I still need an extension bit?

 

[MiniMe]

I have checked the price for aluminium plates and they are reasonably priced ....I am evaluating the option to use one as base

 

[MiniMe]

If you can get the aluminum that’s great.

Hmmm I think that buying a bit collet extender will give me more flexibility in building future jigs

 

[MiniMe]

What went wrong ?
Same say this might ruin the router bearings but as far as I understand these are used for CNCs as well which use the same routers right (at least a good number of the CNCs can use a router that you have)

 

[MiniMe]

From what I am reading you are referring to an extension that ends with chuck like end not with a collet
Is that different ?

I am considering this one but I am now worried that 3 1/4" is way more than I need and I won't be able to sink the router under the table deep enough

Wolfride 1/2-Inch Shank Router Bit Collet Extension Collet Extender for 1/2-inch Shank Bits : Amazon.ca: Tools & Home Improvement

Wolfride 1/2-Inch Shank Router Bit Collet Extension Collet Extender for 1/2-inch Shank Bits : Amazon.ca: Tools & Home Improvement

www.amazon.ca

so if I go with 1/2"or 3/4" base for the sled I would need at most that much to extend the current bit

I am going to try 1/4" MDF first to see if that removes the bending I am seeing
Have you ever had any issues with not being able to raise the bits high enough because of the 1/4"base ?

 

[MiniMe]

Phenolic or aluminium is your base material if you want to go thin, but even with those materials there is no commercial sled made as thin as 1/4".

That article is good news thank you
1/4 aluminium seemed excessively thick to me, The article confirms that 3/8 should be ok. Now I need to find a good Amazon Canada source for that

 

[MiniMe]

Your guessing. I show pictures because it’s a fact. Not a guess. i don’t know what your doing wrong.

I think you way over clamp..

Well he quoted an article showing that bending is a problem for most of these jigs when clamps are used
I am having the same problem so I think you are doing something special not the rest of us )

 

[MiniMe]

There is two more variables that might be different in your case:
-the width of the wood piece you are routing -the narrower, the more concentrated clamping force and closer to the inflection point
-the length of the sled -two of your sleds are shorter that I would ever use. The first one is closer to what I am building and to what @Ola C is using. So for that one -what size are your wood pieces ? Are they panels or just narrow verticals ?

 

[MiniMe]

Researching the topic more I came across this design which makes more sense for me
Notice that the plexiglass screen is gone (that gets in the way when doing work) and also notice the two spacers meant to keep the aluminum base away from the bit and the fence

Also keep in mind, if your router table is made of aluminum there will be some serious scratching on both surfaces as they are never clean enough so plan for some HDMW on the back side

 

[MiniMe]

Hmm I have done some more experimenting this evening and I think I have a solution and an improved design that can still use 1/4" thin plywood for the base. The above design also has some issues in some situations. I will refine my design and experiment more over the weekend and if I get decent results I will post them here

 

[MiniMe]

OK here is what I am going to try to build today. The main target of this design is to reduce the bending when using a 1/4" plywood base or an MDF base. In order to achieve that you need to:
-reinforce the base from below by using a runner (this will lock the jig in this position and it can't be used in other ways)
-clamp the routed piece as close as possible to the purple piece that supports the clamps. This will reduce the momentum of the forces that are bending the plywood base. For this purpose I relocated the sacrificial piece parallel to the fence (still need to find an easy way to attach it there and to easily replace it or push it forward as it is being chewed by the bit) . Relocating the sacrificial piece is optional IF the runner is strong enough to keep the base flat
-use lighter clamps or lighter force when clamping -this is to reduce the force that is bending the base. Use enough just pressure to hold the piece of wood in place

Any combination of the above three measures or just some of them should fixt the problem

 

[MiniMe]

The problem: the base is bending/bowing when the clamps are toggled

Here is what I ended up doing to fix the problem. It turns out that the runner is enough to prevent the bowing/bending for the base. The mid clamp is a little off because I install it before installing the router. The second clamp is needed in my opinion if you want to maintain a relatively low pressure when calmping

Here is a link to he video showing that the bending is gone.
Pay attention to the pencil line on the fence, that is the refence, if the base is bending/bowing it will the line will not be visible anymore
I can't embed it because it is a short

 

[MiniMe]

I agree the jig with a runner is locked down to a degree.
Setting the fence parallel with the miter slot is not a problem, actually the jig helps with that, if I push the fence against the jig I know it will sit parallel with the miter slot and the fence line will traverse the center of the bit.
The problem that you are mentioning appears when the fence need to be way behind the bit. (that is an inland cut to say so and not at the end of the workpiece)