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Why isn't my router table flat?

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insert plate question router table router table insert plate
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10K views 24 replies 15 participants last post by  JoeLyddon  
#1 · (Edited by Moderator)
I've been lucky enough to be able to move to a large-than-cupboard-sized workshop, and one of my first tasks was to make a new (version 3) router table.
I do almost everything on my router table (which is why it's the only tool you can see in the 'shop), and I thought I'd treat myself to a "manufactured" router table insert plate, rather than using the "hole in a bit of plywood" approach I've used before.
I've always found TrendUK to be a reliable company - I like their bits and they ship to Portugal with no fuss. So I thought I'd buy their plate…

Image


Full specifications of which you can find here.

Feature 6 on the list is…
"Moulded with slight crown (0.8mm) for distortion free cuts."

They're right - it isn't flat - my straight edge rocks slightly, but nicely, when on the crown of the plate.

So - I have 2 questions…
  1. Can someone explain to me how a non-flat plate aids in producing "distortion free cuts"?
    I just find it weird to use - not very very weird, just a bit weird - and I'd like to know if there's some benefit (I can see the insert rings could be useful, but I don't use big bits and a single sized hole was never an issue for me), and if so, how I reap that benefit, before I remove it and just drill a hole like I've done before.
  2. Aside from the removable rings, are router table insert plates really any better than "just a hole", and if so, why?

Thanks in advance for the wisdom I know will be brought to bear here on my behalf.
 

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#2 · (Edited by Moderator)
Myself I just installed a brand new router table and an insert.
I cannot figure out how a non-flat insert would help you make better cuts.
Why don't you ask the manufacturer of the insert what its theory is?

When I click on the link above I get this:
Product Not Found

Sorry the product you have requested is no longer available.

This could be the answer to your question.
May be this design just doesn't work very well.
Is it working for you?
If not, can you return it?
You should ship a carton of Port wine my way, I love it.
Bert
 
#3 ·
The general idea is that the crown would flatten out when the router is attached.

I don't know who came up with this idea, but 1, if it's necessary there's an inherent weakness/problem with the router plate design, and 2, they probably never used a router table.

The trend plate looks a lot like the jessem plate, also "designed" with a slight crown. The rings are a major PITA to remove.

In regards to your second question, if you can make due with a single sized hole, and get your table absolutely flat, then a plate offers no real advantage except for easy removal of the router. You can rout a recess on the underside of the table where the router goes to lessen the thickness that the router mounts to, giving you more depth.

I plan on buying the incra aluminum magnalock plate. I do use a variety of different sized bits, and I like how easy the rings are to swap out and you can adjust them to be level with the top via set screws. A very well made plate, I'm just not a big fan of the gold color, but whatever works.
 
#4 · (Edited by Moderator)
I have the Veritas steel router table plate and it too, is deliberately and ever so slightly crowned.
Here's the reasons.
First of all, many routers are heavy and can cause the router table top to sag just enough so that the work has to ride down in the depression and then back up out the other side. That makes an irregular pattern on the work.
The other reason is that wood isn't always perfectly flat, so if the table is crowned at the point where the bit works the wood, the ends of the workpiece don't raise the work in the middle.

That's what the folks at Lee Valley said when I bought it and it has always worked well for me.
Incidently, I like the steel top because I use the Magswitch devices to secure the fence and featherboards in front of the fence.

Check out this link to their page : http://www.leevalley.com/en/wood/page.aspx?p=41793&cat=1
Don
 
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#6 ·
in my old home built router table, eventually it ended up being concave where the router was. What happens then is that the depth of cut depends on pressure across the router bit… not what you want. a small crown would seem to work against this - i could see it being very handy.
 
#9 · (Edited by Moderator)
I use the inserts because, if I use a feather board pushing down on the work, a larger hole will allow the front corner to sometimes dip into the hole. AND, a close to zero clearance makes my "in the fence" DC system work a lot better.
The Jessem solid anodized aluminum plate is an excellent plate. Comes with the lift, though.
 
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#10 · (Edited by Moderator)
My first question would be; is it made in China. If it is then that is also most likely your answer too.
If not, are all the bolts torqued the same during assembly?
I know not where it was made, but it is designed to have this 0.8mm rise in the middle.

When I click on the link above I get this: Product Not Found
Strange - it works for me, the full URL is…
http://www.trend-uk.com/en/CZ/product/RTI_PLATE/3/240/router_table_insert_plate_.html

I've thought some more about this - say I'm routing a thin square slice out of a 10mm square length of wood - this drawing, to scale, shows the angle I'm going to be getting!
Image

that's a long long long way off 90°

I also find it strange when I have a longish piece of perfectly flat wood, that it's only actually on the table at one end. And, as I route along it, at some point it's going to "tip" from being down on one side of the table to the other side.

I agree with Aaron - slightly raised is way better than slightly dipped.

As for the weight arguments - well - that may be true, but it seems to be a "one size fits all" approach - I imagine some routers weigh a lot more than others (mine is pretty light).

I have written to Trend, drawing their attention to this discussion - we'll see what they have to say.

Thanks for the replies - it seems I'm not going crazy after all!
 

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#13 ·
Think about the geometry of the table and bit. If the table were slightly depressed at the bit, you would either have to use quite a bit of downward pressure to get your cut - or put up with slight variations in the profile depth.

With a slight crown, the wood will be at the correct height at the bit without using excessive downward pressure. The wood will "roll" slightly as it passes the bit, but always be at the correct height.

A perfectly flat table would be ideal - if the workpiece was also perfectly flat. A workpiece with a slight bow would route better on a crowned table than a flat (or depressed) one.
 
#14 ·
I would NOT want such an insert plate in my router table…

Mine would have to be FLAT with the table…
... and the table would be strong & reinforced so that it would NOT warp / sag.

... just my opinion…
 
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#15 · (Edited by Moderator)
Plywood is flexible. So is plastic and most any other material usable for this purpose.
Suitable reinforcement with these materials, designed to prevent ANY deformation would be rather clumsy. By that I mean large, thick and still, a discernable flex could be measured because of the stresses caused by a 10 pound router working a large bit at 20,000 rpm or more.
So, just as semi trailers that carry large loads are arched so they do not sag under load, a good, well designed router table top can make good use of the idea.
The idea of starting out with a perfectly flat table and having it remain flat under working conditions is a great idea, but I'm afraid it's not very practical.
I bought my Veritas table with full knowledge that it was slightly arched and additionally, for the excellent router attachment device that allows me to remove and replace the router and not have to fuss with centering it.
I believe we have all stated our beliefs and preferences.
So I'm going to bow out of this thread.

Don
 
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#17 · (Edited by Moderator)
I think the general idea is to reduce friction and keep the bottom of the piece at exactly the right height. To those of you who think this is a design flaw, I doubt it. Trend are a well established company making sawblades, router bits and accessories, and industrial tooling. If they put a crown on their router table insert, you can be sure they did it after a lot of R&D. The different size rings aid dust collection and prevent the front of the piece digging into the back of the ring once it's passed the cutter - which could happen if you had a big ring with a small cutter.
 
#19 ·
I think you will find that the slight crown is present even with a router attached.
While we always focus on the idea of flat - if you are routing a profile or a groove - the only distance that matters is the height of the bit to the table 'Where the bit is" and not versus the rest of the router table.

this feature ensures that if you are cutting a cope and stick joint in a cabinet door - and you adjust the bit to cut the groove 1/2 inch above the table - - that is exactly where it will be - regardless if the rest of your table is perfectly flat or not.

It is the same reason you check your jointer fence for square at the cutter head, because that is the spot where the cut happens. - - being square 18 inches away on the outfeed side doesn't help - - the cut already happened!
 
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#20 ·
I have written to Trend, drawing their attention to this discussion - we'll see what they have to say.

Just for completeness…
I did write to them, that very day, 44 days ago…
I said…

I'd like to draw your attention to this thread on LumberJocks, discussing the Trend router table plate.

http://lumberjocks.com/topics/39338

I, and they, would be interested to hear your response/reasoning for the design feature discussed.
If you don't want to join and comment there directly, you can reply to me and I'll post it "from you".

Thanks in advance

Shock - I have yet to receive a response.
 
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