Is this router coping sled design OK ?

3215 Views 67 Replies 6 Participants Last post by MiniMe, 5 mo ago

MiniMe

Discussion Starter · 5 mo ago (Edited)

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

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Rebelwork Woodworking

· #41 · 5 mo ago (Edited)

You have to do your own thing. You only need to hold the part from vibration..This allows me to go through the cutter and back without incident..

My door material is 13/16 and it is set without any problems..

My leg taper jig has a 1/4 bottom.,

“You who are saying 1/4" plywood will withstand toggle clamp force.” Thats going to depend on how much force you apply…

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MiniMe

Discussion Starter · #42 · 5 mo ago

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 ?

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radio_davio

· #43 · 5 mo ago

Just started designing and gathering materials for my first sled. Using 1/4" G10 for the base. Haven't chosen (or scrounged) a toggle clamp yet, but yours look good. Am also looking at the style with a moveable stop to lock the work pieces on three sides. Thanks for posting.

Rectangle Output device Gadget Machine Circuit component

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MiniMe

Discussion Starter · #44 · 5 mo ago

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

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MiniMe

Discussion Starter · #45 · 5 mo ago

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

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MiniMe

Discussion Starter · #46 · 5 mo ago

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

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Rebelwork Woodworking

· #47 · 5 mo ago

You need a clamp only at the runner location. I wouldn’t put one on each side. This could cause bowing..

look at the picture I showed you. This has worked for almost 20 years..

MiniMe

Discussion Starter · #48 · 5 mo ago (Edited)

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

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Rebelwork Woodworking

· #49 · 5 mo ago

I got all kinds of plywood like you use in your jig. I wouldnt use it, but if it works for you , go for it

Ola C

· #50 · 5 mo ago

I would recommend not using a runner even if it improves the bending issue.

Reason 1. If you use fence as length reference this needs to be absolutely parallell to the miter slot. That will be extremely annoying trying to dial in every time for each setting.

Reason 2. If you not use the fence as length reference you will have no support in that direction when you make the cut. You can put a block on the fence before the cut for length reference, but you will have no fence support during the actual cut.

Btw. Check with a straight edge on the backside of the base if it bends, a short pencil line on the fence is not much of a reference for measuring this.

Rebelwork Woodworking

· #51 · 5 mo ago

I would always have a runner for this application..

Ola C

· #52 · 5 mo ago

Rebelwork Woodworking said:
I would always have a runner for this application..

For what reason?

Rebelwork Woodworking

· #53 · 5 mo ago

Guarantees the part is against the cutter.

Jig does all the work…

Ola C

· #54 · 5 mo ago

Rebelwork Woodworking said:
Guarantees the part is against the cutter.

Jig does all the work…

How do you ensure the length position of the workpiece?

Rebelwork Woodworking

· #55 · 5 mo ago

Bump it against the fence

What are you trying run?

Ola C

· #56 · 5 mo ago

Rebelwork Woodworking said:
Bump it against the fence

What are you trying run?

Ok, so then you always make sure the fence is parallell to the miter track?

Rebelwork Woodworking

· #57 · 5 mo ago

No different than a table saw fence, blade and miter slot.,

Ola C

· #58 · 5 mo ago (Edited)

Rebelwork Woodworking said:
No different than a table saw fence, blade and miter slot.,

Big difference. A router fence doesn't need to be parallell to the cutter (it can't be parallell to a round shape) and very seldom travels parallell to a miter slot since it complicates the guiding of the fence considerably. I wouldn't make a coping sled that requires the fence to be absolutely parallell to the miter slot at all settings. On the table saw you will get away with the miter slot not 100% parallell to the fence since you never use both at the same time to guide the workpiece. Here you won't get away with that, they need to be spot on parallell if you use both in this operation.

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Rebelwork Woodworking

· #59 · 5 mo ago (Edited)

#1….. I use both fence and slot along with fence on the the table saw for tenons.
#2…You treat the router table or shaper the same.
#3… This is why we have Forman’s/ lead mans in place to keep things setup correctly and safe ..l

its your shop, do as you please..

Ola C

· #60 · 5 mo ago (Edited)

Rebelwork Woodworking said:
#1….. I use both fence and slot along with fence on the the table saw for tenons.
#2…You treat the router table or shaper the same.
#3… This is why we have Forman’s/ lead mans in place to keep things setup correctly and safe ..l
its your shop, do as you please..

OK, some people cut tenons like that I agree, but on a table saw you have a system for setting the fence parallell to the miter slot, on a router table you most often haven't.

....and most people don't have a foreman setting up their machines for a cut. It's not my shop we are discussing here, I'm trying to come with good tips to @MiniMe

Still consider a coping sled that requires parallellity between fence and miter channel a non preferred solution if you don't already have a system where these two automatically travels perfectly parallell to each other.

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