# Help matching heights of tongue and groove bits



## joel74 (Jan 21, 2011)

Any ideas as to the best way to match groove and tenon heights when I'll be grooving with the pieces flat on the table while for the tenons, I will run the stiles clamped on a Woodpecker's coping sled – raising them about 1/2" off the table? I'd rather not have to change bit heights by trial and error since I believe my Freud slot and tongue set is designed to match heights if I don't change the router height. But, doesn't that require both bits to be "bottomed out" in the collet? Thought that was a no-no.

Should I clamp a board to the table and mill the grooves on top of it so they are "elevated" the same amount as the sled will elevate the stiles ? But, that demands being extremely precise with the board's thickness to make it a perfect match to the sled's thickness.

While I've done a lot of wide-ranging woodworking over the last 50 years, this will be my first major router table project. I've got a lot of stiles and rails to run – radius corners, groove and tenon, roundovers, etc. I've already got a good amount invested in wood and bits, etc. so I can't afford to screw this up. So, any hints, tips, suggestions would be greatly appreciated.

Thanks guys!

Joel


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## bobj3 (Jan 17, 2006)

Why Our Sets Are Best

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bigbit said:


> Any ideas as to the best way to match groove and tenon heights when I'll be grooving with the pieces flat on the table while for the tenons, I will run the stiles clamped on a Woodpecker's coping sled – raising them about 1/2" off the table? I'd rather not have to change bit heights by trial and error since I believe my Freud slot and tongue set is designed to match heights if I don't change the router height. But, doesn't that require both bits to be "bottomed out" in the collet? Thought that was a no-no.
> 
> Should I clamp a board to the table and mill the grooves on top of it so they are "elevated" the same amount as the sled will elevate the stiles ? But, that demands being extremely precise with the board's thickness to make it a perfect match to the sled's thickness.
> 
> ...


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## Cherryville Chuck (Sep 28, 2010)

One of the first things you will have to do is mark the bottom sides of the boards so that you have all of them referenced the same. If you mill one part with the face down then you mill the other one the same way.If you are making flooring I would keep the back sides against the sled or table. If you are mounting the faces to a frame then mill with the faces down.
It is very difficult to get every board the same thickness. Even if they start out the same humidity can change them.
You don't want to bottom bits out. When they start getting hot they stretch and can loosen in the collet if bottomed out. You can install a rubber grommet below the collet instead. Some bits come with lines etched on the shanks to show how deep you are in the collet. I would mill all one part and then try your 2nd setup on some scrap until you get it right.


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## joel74 (Jan 21, 2011)

Thanks for the reply Charles. When you say "If you are mounting the faces to a frame then mill with the faces down.", are you suggesting that I NOT use the sled for coping the tenons? How can I safely – and accurately – cope the stiles without the security of a coping sled? Not sure I'd trust myself to keep them ALL a perfect 90º to the fence, etc.


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## Semipro (Mar 22, 2013)

joel
This is reason I do not use a coping sled
push block, that way bits same height
This just the way I do it , by far not the law of the land


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## bobj3 (Jan 17, 2006)

Hi joel

The bearing on the bit is the fence,it's all ways perfect 90º to the stock so to speak..

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bigbit said:


> Thanks for the reply Charles. When you say "If you are mounting the faces to a frame then mill with the faces down.", are you suggesting that I NOT use the sled for coping the tenons? How can I safely – and accurately – cope the stiles without the security of a coping sled? Not sure I'd trust myself to keep them ALL a perfect 90º to the fence, etc.


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## Cherryville Chuck (Sep 28, 2010)

bigbit said:


> Thanks for the reply Charles. When you say "If you are mounting the faces to a frame then mill with the faces down.", are you suggesting that I NOT use the sled for coping the tenons? How can I safely – and accurately – cope the stiles without the security of a coping sled? Not sure I'd trust myself to keep them ALL a perfect 90º to the fence, etc.


I do exactly like John does, I use a push block. I've never had a need for a coping sled. Because there will probably be some variations in board thickness you need to either mill all the pieces with the face down or the back down to ensure they lie flat on the side that they will be mounted to. What are you planning to use the boards for?


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## WurliTzerwilly (Jun 9, 2013)

bigbit said:


> Any ideas as to the best way to match groove and tenon heights when I'll be grooving with the pieces flat on the table while for the tenons, I will run the stiles clamped on a Woodpecker's coping sled – raising them about 1/2" off the table? I'd rather not have to change bit heights by trial and error since I believe my Freud slot and tongue set is designed to match heights if I don't change the router height. But, doesn't that require both bits to be "bottomed out" in the collet? Thought that was a no-no.
> 
> Should I clamp a board to the table and mill the grooves on top of it so they are "elevated" the same amount as the sled will elevate the stiles ? But, that demands being extremely precise with the board's thickness to make it a perfect match to the sled's thickness.
> 
> ...


The problem with the Woodpeckers coping sled is that the work piece sits above it. You would be better off if you can use the Woodpeckers Mini-Coping Sled, where the workpiece sits on the table surface and the sled acts like a super push block.

There's no reason that you can't bottom out a router bit, unless it has a 'K' mark which is the optimum placing for the bit. The more shaft in the collet, the less vibration etc. I'd always leave a slight gap at the bottom, to allow for heat expansion.


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## Dmeadows (Jun 28, 2011)

bigbit said:


> Thanks for the reply Charles. When you say "If you are mounting the faces to a frame then mill with the faces down.", are you suggesting that I NOT use the sled for coping the tenons? How can I safely – and accurately – cope the stiles without the security of a coping sled? Not sure I'd trust myself to keep them ALL a perfect 90º to the fence, etc.


Joel, in my opinion, a coping sled is totally unnecessary for any application I have found. The square push block works 95% of the time. For the rest, I clamp the workpiece to an auxiliary fence attached to my miter guage(yes, you need a miter slot for that). I use these procedures both on my router tables and my shaper. Have yet to find a job that one or the other won't accomplish.

There is an advantage to feather board hold downs to keep the boards tight to the table.


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## joel74 (Jan 21, 2011)

Thanks all. 

The project at hand is building 6 cabinet doors to match the still presentable 22 year old ones from Ikea. They have very odd roundovers including a roundover on the tongue edge of the rails and a half round on the grooves. Very unusual details but if I want to match the rest of the kitchen, I have to do this. I just can't afford a whole new kitchen nor do I have the time to build all new doors. If I were to build all new ones, I'd simply make shaker style doors without the unique detailing. That would almost be easier. 

Thanks for your comments, I'll try to rig up a push block and ignore the sled. Need to practice this a lot so I don't waste any of my good stock. 

Bob, I don't understand your comment: "The bearing on the bit is the fence,it's all ways perfect 90º to the stock so to speak..." I can see how "no-fence" works for the grooves, but what about the tongues?


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## Cherryville Chuck (Sep 28, 2010)

Joel, if you are using the boards for cabinet doors then all your milling should be done with the faces down on the table. That way the faces will all fit flat into the frames. The backs might be slightly uneven but that won't matter.


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## Dmeadows (Jun 28, 2011)

Cherryville Chuck said:


> Joel, if you are using the boards for cabinet doors then all your milling should be done with the faces down on the table. That way the faces will all fit flat into the frames. The backs might be slightly uneven but that won't matter.


I agree with you Chuck! Sooo, why do shaper cutter manufactures insist on making cutters that need to have one cut face up and the other face down? Most all do that now. I have some older cutter that don't, but rare these days!

An yes, I realize that I can turn them over, reverse the rotation and feed direction and cut them properly. But still...

Off topic, sorry.


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## Dmeadows (Jun 28, 2011)

bigbit said:


> Thanks all.
> 
> Bob, I don't understand your comment: "The bearing on the bit is the fence,it's all ways perfect 90º to the stock so to speak..." I can see how "no-fence" works for the grooves, but what about the tongues?


Although Bob is of course correct, I don't want to free hand what are essentially cope cuts on a 2" wide rail either!


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## joel74 (Jan 21, 2011)

Well, it seems I can't take advantage of the matching bit heights anyway. 

As was suggested, I bought an o-ring – 1/2' X 1/8" thick to make the 2 bit heights match. Dropped it in, then mounted the slot cutter and ran a 1/4" groove 1/4" off the table in a test stile. BTW, I used the fence which I prefer over the bearing which might "go around the corner at the start or finish. Then, I tried to replace the slot cutter with its matching tenon cutter without changing the router height. Under the table, I pushed in the spindle lock button but couldn't loosen the collet with my bent wrench from above the table. I have two bent wrenches but neither is shaped correctly or offset enough to reach down that far through the small opening in my Incra insert.

Since I'll have to set the tenon cutter height by trial and error, I guess the Woodpecker sled height difference won't matter and I may as well cope the tongues using the Woodpecker sled. At least it'll keep the rails from slipping which may very well happen with the push block technique.

Can't get back to this project until Tuesday. Hope my blanks don't warp on me just sitting there stacked and stickered. It's quite humid in my barn work shop... fingers crossed. 

Thanks for your great tips and suggestions. Joel


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## Cherryville Chuck (Sep 28, 2010)

bigbit said:


> BTW, I used the fence which I prefer over the bearing which might "go around the corner at the start or finish. Joel


That's why I like using the fence too. Just a little bit of insurance to make sure it goes right. You can use the sled if you like. However, I almost always take a second pass to make sure the cut is smooth so it doesn't matter if it slips a bit or not for me.


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## joel74 (Jan 21, 2011)

Chuck, thanks for your double-pass tip. Don't know why I always forget that good advice. Think I'll "retest" my push block technique since during a 2nd LIGHT pass, the rails won't be as prone to slipping or twisting. This should increase my confidence level.

Do you guys think this idea would work to take advantage of Freud's matching height bit set and allow all pieces to be run directly on the table surface? –– After routing the grooves, I'll use Triton's above-table crank to raise the collet until it's high enough for the bent wrench to work – while carefully counting the crank's revolutions. Then, swop bits and lower the router that exact same number of revs. Theoretically at least, the result will be precise "matched heights." Right???


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## Semipro (Mar 22, 2013)

Joel
Are saying that when you remove router table insert ring that you can not reach the collet nut ,should only be about 1" maybe 1 1/2" blow the top


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## Cherryville Chuck (Sep 28, 2010)

bigbit said:


> Chuck, thanks for your double-pass tip. Don't know why I always forget that good advice. Think I'll "retest" my push block technique since during a 2nd LIGHT pass, the rails won't be as prone to slipping or twisting. This should increase my confidence level.
> 
> Do you guys think this idea would work to take advantage of Freud's matching height bit set and allow all pieces to be run directly on the table surface? –– After routing the grooves, I'll use Triton's above-table crank to raise the collet until it's high enough for the bent wrench to work – while carefully counting the crank's revolutions. Then, swop bits and lower the router that exact same number of revs. Theoretically at least, the result will be precise "matched heights." Right???


There's no guarantee that it will work perfectly but it could be very close. The reason why is called "backlash" and it is the slight amount of movement in the screw and socket before any adjustment happens. This is true in all threaded adjusters. The threads cannot be made to zero tolerances or it would be too difficult to turn. You might be able to wiki backlash for a better explanation. Always do a test fit on scrap before you rout the good stuff.


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## WurliTzerwilly (Jun 9, 2013)

bigbit said:


> Chuck, thanks for your double-pass tip. Don't know why I always forget that good advice. Think I'll "retest" my push block technique since during a 2nd LIGHT pass, the rails won't be as prone to slipping or twisting. This should increase my confidence level.
> 
> Do you guys think this idea would work to take advantage of Freud's matching height bit set and allow all pieces to be run directly on the table surface? –– After routing the grooves, I'll use Triton's above-table crank to raise the collet until it's high enough for the bent wrench to work – while carefully counting the crank's revolutions. Then, swop bits and lower the router that exact same number of revs. Theoretically at least, the result will be precise "matched heights." Right???


I watched a UK demo last weekend of Trend tools and the guy there was making raised panel doors. His method was to cut all of one part first, then reverse a cut piece and use it to exactly line up the cutter for the matching pieces. There appears to be zero error and without any noticeable measuring or rev-counting, his rails and styles fitted together perfectly. I can only advocate what I saw.


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## joel74 (Jan 21, 2011)

John, it's not the depth of the collet that keeps the bent wrench from working. It's that the insert hole is too small to allow the offset part of the wrench to drop down and get a full grip on the collet facets. The bend itself won't fit in the hole so it reaches down on a steep angle.


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## MAFoElffen (Jun 8, 2012)

Here's my two cents... I have done a lot of restoration carpentry... so I hear you, but for a moment, just relax and read...

I look at the wood and pick all the "face sides" I want and mark those pieces to reference those sides of them. I cut the profiles with all pieces face down. My reference is from the face/table to the inside edge of the slot/groove/spline. If on a coping sled, a router sled, a adjustable angle sled... my reference is from the top edge of the sled to the inside edge of the groove/spline.

But I cheat. Cheat? Well I try to make something repeatable, repeatable.I set the bit to a piece of scrap I cut with that profile and kept as a guide. <> I set the bit to that. That way I can go back a year later and make that door again and match it. The trick is to get that set the first time. The first time I set the bit from table to the inside edge of the groove... On matching existing, I use existing to match the bit height to those same reference points. . In new profile, I always cut on scrap first, until I get what I want, then keep that piece and the other side of the joint, as a pair, for reference. So I cut the profiles for all the stiles. I cut the alike profile on the rails.

Then for the ends of the rails, the tenons. I have a coping sled, but hardly use it. I've tried using just the bearing, but if you are pushing a little too soon at the start or too hard at the end, you color outside the lines and go over the edges and not get good clean corners. I have a jig I made to be my repeatable sacrificial block... I've talked about it before (it pictured in my uploads). It is just pieces of scrap to make a 90 degree angle with a replaceable sacrificial block near the 90. It stays in one spot near my table, I know it's 90 degrees and that it works fine along my fence. It's made so I can comfortably and securely hold the rails to it, keep them feeding along the fence.

Whether you are using a coping sled or off the table (like I do), setting the bit is still to that bottom edge of the groove. You can set that with a piece of scrap guide, gauge, rule, or from the stile you just cut/ again lining up the bottom edge of the groove.

When I assemble and glue panel glueups, I do that all face down and line up the faces to that side of the cauls, then clamp. When assembling doors, I assemble face down and line up the faces. So a pattern... The faces are the visual side. The face to the face side side of the groove is the reference point for all spline types of joints in furniture and cabinet work. (In flooring, it is opposite, off the bottom/support side).

So on the table or up on a coping slee, no matter... Same kind of measurement and reference. You match the bit reference point to where you want that point to be on your work... From the face to the inside dge of the groove. Not matter what kind of spline joint.

You get a matched set of spline bits (male/female) it means the profiles match up... Not that the shanks are the same length. It they where the same length, then maybe those profiles would match up... but since you don't want to go bottoming a bit in the collet, even shank length is not a reference point.

I'm reading your posts and I see a apttern where you have a little confusion on how to set those matched bits to get then to line up... I just think you need to take a breath, step back and look at it from a different perspective. Does what I do, make sense of that? I hope it brings some understanding. After a few times, it clicks right in.


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## joel74 (Jan 21, 2011)

Mike, Thanks so much for your detailed explanation and advice. I really appreciate the time you devoted to encouraging me in my first large router table project. Deep breath... 

I'm replacing 6 doors and 5 drawer fronts in my 20 year old Ikea kitchen which poses some unusual detail challenges. To match the remaining Ikea doors, besides the customary groove and tenon, I have to: Radius what will be the 4 outside door corners, roundover all edges and even roundover the INSIDE edge of the groove. (This unusual detail has trapped dirt and water over the years but to match their doors, I'm forced to do the same.) I bought a 1/4' half round bit which will mill a 1/8" roundover simultaneously on the front inside stile and rail edges and the inside groove edge where it meets the center panel. Also, roundover the front edge of the rails "directly over" the tenon. YES, Ikea has 2 roundovers facing each other where the stile and rail meet. I guess that was to "hide" less than accurate seams. I guess what's making me nervous is how many steps there are and how many "opportunities" to screw up along the way.


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## Cherryville Chuck (Sep 28, 2010)

I am not sure if I am reading you correctly. Is the profile on the edges of your doors the same as this bit would make? External Bullnose Bits — Full Radius - Lee Valley Tools Are you saying that it is rounded at the outer edge and against the panel? That would be a very unusual design.

Normally you would have only a 90 degree 1/4 round, not a 180 degree 1/2 half round there. If it is only a 1/4 round then the following below would be the case. If it is a 1/2 round then it might be a good idea to post some closeups of the inside corner of one of the doors and one looking at the joint between the rail and stile either looking straight up or down on it.

In a raised panel set of bits you have the cutter that makes the profile you see when you look at the inside edges of the frame but you also have a bit that is the reverse to cut the ends of the rails to match. So if you are putting a round over on the inside edges, then you need a matching cove on the ends of the rails. A bearing guided cove bit probably won't work because of the bearing but a round nose or core box bit should- providing that the two curves are a perfect match. They should be if they are the same radius but it depends on how accurate the manufacturing is.


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## joel74 (Jan 21, 2011)

Yes that's what I needed. I bought Freud's version of that bullnose bit to do the 2 roundovers on the 1/4" wood strip at the front of the groove in the same pass. (Not sure of the name for the "strips" that enclose the rebate.) 

I attached a photo which will hopefully, better illustrate what I'm trying to match. I now realize that it probably would have easier to remake ALL the doors with simple shaker stiles and rails but I've already invested enough money and time down the "partial replacement" path.


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## MAFoElffen (Jun 8, 2012)

I see, so everything looks like it has a slight radius... even the corners of the door is rounded. A technique. 

Well since you are matching, easier to hide imperfections on face heights that way. You don't have to blend things in. Good for a first project. Sounds like you are on the right track with that.


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## Cherryville Chuck (Sep 28, 2010)

That looks pretty simple Joel. It looks like it is just a tongue and groove frame and panel where all the frame pieces were rounded over before put together using just this bit http://www.leevalley.com/en/wood/page.aspx?p=42910&cat=1,46168,62157. If there is any part you aren't sure of, practice on some cheap 3/4" pine first.


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## joel74 (Jan 21, 2011)

Actually, I also thought that the same 1/8" radius bit which rounds the outer edges would round over that inside edge where the S&Rs meet the panel. However, its profile is too wide to fit inside of the groove and would tear up the far side. I bought a bull nose bit that does clear the other side of the groove and would do both edges simultaneously. However, this means that since the bit routes both edges of the front 1/4" groove shoulder (or whatever you call that part), I have to be extremely accurate with the groove's distance from the table and hope my pieces tightly hug the table so that the thickness of that groove shoulder doesn't vary. I haven't had good luck with a hold down featherboard which adds friction and I can't push through as smoothly.


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## Cherryville Chuck (Sep 28, 2010)

Joel we may be having some problems with terminology here but I am adding a link to a wiki article about panel doors that may help a bit. Frame and panel - Wikipedia, the free encyclopedia From what I could see in the picture the roundover bit should be all you need to go with the tongue and groove set. You would make a groove all around the inside of the rails and stiles and you would make a tongue all around the panel and at the ends of the rails to join them to the stiles.

It is a bit of an odd design they made, normally the rails and stiles are flush at the joints. I suspect, as someone mentioned I think, that they did it to hide a potential mismatched joint surface. I've looked at the photo several times and I can't see where the bull nose comes into play. If I'm missing something maybe someone else could join in and let me know if I need new glasses.

If you read the Wiki article you will read that the center panel is supposed to float in the frame. Otherwise seasonal humidity changes could swell the panel and push the frame apart. The tongues on the panel should be at least 1/16" shallower in depth on the sides than the grooves in the stiles. They should also be just a hair narrower than the grooves on all sides so that they are free to move.


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## joel74 (Jan 21, 2011)

The bullnose bit is needed because the simple 1/8" roundover bit – which will do all the outside edges – will not "fit" inside the groove while rounding the edge that meets (kisses) the panel. It will tear up the far side of the groove while cutting. And, it would also mean that I'd have to flip my boards over and reference that cut from the back side of the S&Rs to roundover that second edge. I don't want to do that because there might well be a tiny taper to the boards making the back side not perfectly parallel to the front. Hope I'm being clear with my description. I have done extensive testing on these routs and don't see how the simple 1/8" bit can work unless I grind down its "shoulder" and make it small enough to spin inside the groove without touching the other side. And, that might weaken and destroy that bit. 

Also, to match the existing doors, (see earlier posted photo) my panels will be flat – simply 1/4" plywood so the only tongues involved in these doors are the tight fitting, glued tongues at the ends of the rails. And being birch plywood, which should not move with humidity changes, I was planning to glue them in for added strength.


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## joel74 (Jan 21, 2011)

If you guys will continue to be patient with my lack of door-making experience, I have another question:

The doors I'm matching measure – on average – 19.5mm thick which includes the paint on both sides. When I thickness plane down to final thickness, should I go thinner to allow for the added paint thickness? Or, is sprayed paint so thin that you don't allow for it?

Your replies have been extremely helpful... and confidence building. Again, many THANKS!

Joel


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## Cherryville Chuck (Sep 28, 2010)

I couldn't see the curve next to the panel in the picture. You are correct with the bull nose. That really is a goofy design on Ikeas' part. Just from what you knew and what you may have learned here, I'm sure you could have done a better job of them.

Your panel won't move but the rails stiles might move a little. Wood will swell and contract across the grain but moves very little along the length. I still wouldn't fit it tight to the bottom of the grooves but you probably don't need as much as I posted before.

A coating of paint or varnish is only a few thousandths of an inch thick, even if it is brushed on.


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## MAFoElffen (Jun 8, 2012)

Thickness- When matching, what you see up front, from the front is visual and what you notice. Charles is right in thickness, a finish doesn't add that much, even if laid on thick. By the time you assemble and sand it (sanding will take some away), then add stain and finish, you are going to be about the same... and visually, you won't notice a thickness difference as much as with other pieces and perspectives... By how our brain works and see's things, _visual perspective_ is more dependent on proportions than exact measurements. 

Unless someone goes up there with micrometers or calipers... But with the other doors being mass produced and probably done by CNC, but with age and humidity since then, they are probably as going to have as much or more of a variance from door to door (they are wood/not steel), so... not even be able to notice.


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