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Hi,

This is my first post and I'm not only a newbie here at routerforums but I'm also a total newbie to woodworking to the point that I haven't even purchased a router or table saw yet.

I have a very specific need for a project that will require making hundreds of evenly spaced dadoes/grooves and really need help figuring out the easiest way of doing it.

I'm making roughly 2' x 4' acoustical diffusers that will need to have a groove/dado that is only 3/16" wide (for undersized 1/4" plywood), 3/8" deep, and spaced exactly 1.5" apart.

I will be making at least 20 of these, and each one will have 12 grooves spaced 1.5" apart, only 3/16" wide and 3/8" deep.

I was originally going to buy a table saw and dado set but I cannot find a dado set that will allow me to cut under 1/4" wide dadoes.

I then thought about buying a thin kerf blade and regular kerf blade and just stacking them to make my own cheap dado set but I'm having a lot of trouble finding two blades that equal exactly 3/16" to fit my 1/4" nominal plywood.

To help visualize what I'm making (since I cannot post links yet) just think of slatwall panels only instead of t-shaped grooves they will just be flat/straight grooves and instead of the slats being 2.5"-3" wide, they will only be 1.5" wide.

I've looked at several home made exact width dado jigs for a router, but it would take forever (and probably wouldn't be very accurate and I do need accuracy for this project) to measure and line up 12 grooves per board and then do it 20 times or more... That's a minimum of 240 measurements, unclamping, clamping, etc.

I want to make a jig that will allow me to cut perfect 3/16" wide, 3/8" deep dadoes/grooves spaced 1.5" apart and make it as easily as possibly and fool proof as possible since I have no experience.

If only 1/4" plywood were really 1/4" I could use a dado blade and table saw and have no issues, but alas, I really need some ideas. :)

The only good news is that I don't need it to be adjustable because I'll always be using the same plywood and I'll always be making 3/16" grooves, 3/8" deep, every 1.5" apart. The bad news is I have no idea what the best tool to use is or how to design this for a finished product that will be roughly 2ft x 4ft with 12 of these grooves per board.

Thank you so much in advance for your ideas, help and support. I've spent about 30 hours in the last week researching this forum, YouTube videos, and Google, and have come up with many ideas, but none of which I really know how to engineer and build properly. I finally landed here, made an account, and hope to become a master at this and one day look back on this, my first post here, and chuckle at how inexperienced I "was" and see how far I've come.

--Jason
 

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Welcome to the forum Jason. Check out the jig that Otis (OPG3) posted in an old thread. It may give you some ideas. http://www.routerforums.com/general-routing/40389-totally-disgusted-2.html

A dado can be set to give the right width groove for uou. You would use one side plate and the 1/16 plate that comes with them and then use some dado shims (Lee Valley sells them for one) to fine tune the fit.

If you use the router bit 3/8" deep is considered too heavy a cut for a single pass in a 3/16" bit. The general rule is only as deep as the diameter per pass.
 

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Oliver (Prof. Henry)
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I think the easiest way would be to cut them on a table saw. Most table saw blades have a 1/8" kerf. I would make a 1/16" removable shim that runs the length of the fence and then:

1. Set the fence for the first cut with the shim in place and cut all the pieces.
2. Remove the shim and recut all the pieces (giving you your 3/16").
3. Move the fence to the next position. Put the shim back in place and rinse and repeat steps 1 and 2 until finished.

Whatever method you use will take time but this way you only have to make one set-up for each cut.
 

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You can stack saw blades if they both have the same number of teeth and are the same diameter. A dado blade assembled from one side blade and the 1/16 chipper with shims to get the spacing exact to fit your plywood would be the best way to cut accurate dados quickly on a table saw. If you cut some strips that are exactly 1 1/2 inches wide you can use them between the fence and the work, removing one strip for each pass. I would cut a dado in all of the boards, then remove one spacer and cut them all again, then remove another spacer, etc until all of the Dados have been cut. Tape or clamp the spacers in place to keep them from moving while making the cuts. This is an accurate way of getting the incremental spacing needed between the cuts. You don't move the fence at all. I hope I'm clear with this. If not, let me know and I'll try to describe it again.

Charley
 

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I used a pair of cheep 7 1/4 inch circular saw rip blades and a small shim or two to get the desired width. One pass on the table saw for each dado.

Might take a little thinking to come up with a spacing jig.
 

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Sounds like the perfect job for an Incra LS system on a router table, using a 3/16" bit. Once you locate the center of the stock on the Incra system you could even change the bit size so that if you get a batch of 7/32" stock, you still get the same spacing between grooves.

Shoot, with a large enough table, the 32" Incra could handle doing the grooves in the 24" length across the 48" width. (the 25" could do the job in theory, but i'd not want to get that close to the limit of travel with accuracy being that important) Simply start in the middle and work toward the edges with each adjustment of the positioner. Easily repeatable system too.

earl

edit--if you did buy a table saw, and use Mike's suggestion of 7 1/4" blades--the LS positioner works on a table saw also.
 

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Hey, Jason; welcome!
You didn't mention what your 2' x 4' panels are made of? MDF or plywood?
If they're MDF you are going to be making a LOT of very nasty dust... please don't underestimate how bad this stuff is for your lungs. Plywood's not much better.
An alternate system could be alternating the vertical 'fins' with 1.5" wide full length spacers, butted up tight to the fin and glued to the base panel. Tight fit and no dadoing required. make everything from the same 1/4" plywood.
 

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Is this what you are trying to build.

If so:
1. Do you plan on buying a router?
or
2. Do you plan on buying a table saw?

In your profile I don't see any tools you have listed (such as a circular saw).
 

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Ross
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Welcome to the forum Jason
 

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I'm surprised no one has mentioned "undersized" plywood router bits. They are designed to cut dados for modern plywood that is slightly thinner than the stated width. Rockler has 'em but other outfits do as well. From the sound of it, that's exactly what you were asking for.
 

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Hi,

I have a very specific need for a project that will require making hundreds of evenly spaced dadoes/grooves and really need help figuring out the easiest way of doing it.

I'm making roughly 2' x 4' acoustical diffusers that will need to have a groove/dado that is only 3/16" wide (for undersized 1/4" plywood), 3/8" deep, and spaced exactly 1.5" apart.

I will be making at least 20 of these, and each one will have 12 grooves spaced 1.5" apart, only 3/16" wide and 3/8" deep.

--Jason
something the size of a Bosch Colt in a plunge base would be made to order for this...
Bosch PR20EVSPK Colt Palm Grip 5.6 Amp 1 HP Variable-Speed Combination Plunge and Fixed-Base Router Kit

your bit...
Freud Tools
Freud Tools | 7/32" (Dia.) Mortising Bit

FWIW... 3/8" is a might deep.. suggest you go for a 1/4"... or less
 

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Discussion Starter #13
Welcome to the forum Jason. Check out the jig that Otis (OPG3) posted in an old thread. It may give you some ideas.

A dado can be set to give the right width groove for you. You would use one side plate and the 1/16 plate that comes with them and then use some dado shims (Lee Valley sells them for one) to fine tune the fit.

If you use the router bit 3/8" deep is considered too heavy a cut for a single pass in a 3/16" bit. The general rule is only as deep as the diameter per pass.
Thanks for the info and suggestion.

I'm obviously a total newbie, but I've read all the wonderful tips and suggestions made in this thread up to this point and have spent some time researching the different jigs suggested.

Since I have so many panels to make and since they are so large, I keep coming back to wanting to use a dado set for a table saw.

I thought in order to use a dado set (please correct me if I'm wrong, as it seems I probably am if I'm understanding your suggestion correctly) you had to use two outside blades (which are normally 1/8" thick each) plus whatever chipper(s) and shim(s) between them, like a sandwich.

Are you saying I could use just one 1/8" blade and a 1/6" chipper, and nothing more, to get a 3/16" dado? If so, I believe this, along with some spacers suggested in another post will probably be the easiest and fastest (and cheapest as I will only need a table saw instead of both a table saw for my ripping and a router for my dadoes) method to cut my grooves/dadoes.

I've been researching 1/4" stock and am finding that actual widths aren't 3/16ths after all, and in fact they range from .201" to .230" roughly, so I suppose I'd need some shims, too.

Instead of purchasing a whole dado set, is it possible to just purchase a 1/16" chipper and some shims and then just use a regular 1/8" kerf blade?

I've also thought about purchasing the Vermont American Wobble Dado set because it's cheap and the only one I've seen that allows dadoes below 1/4". I've read they have a bad reputation, but it seems that comes mainly from wide dadoes. Do you think it would be a good way to start, or should I stick with trying to find a regular stacked dado set that will work for my narrow grooves?

Based on my reply, do you think I understand your suggestion correctly and do you think this would be the best way to go?

Thanks again for all your help!

--J
 

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Discussion Starter #14
You can stack saw blades if they both have the same number of teeth and are the same diameter. A dado blade assembled from one side blade and the 1/16 chipper with shims to get the spacing exact to fit your plywood would be the best way to cut accurate dados quickly on a table saw. If you cut some strips that are exactly 1 1/2 inches wide you can use them between the fence and the work, removing one strip for each pass. I would cut a dado in all of the boards, then remove one spacer and cut them all again, then remove another spacer, etc until all of the Dados have been cut. Tape or clamp the spacers in place to keep them from moving while making the cuts. This is an accurate way of getting the incremental spacing needed between the cuts. You don't move the fence at all. I hope I'm clear with this. If not, let me know and I'll try to describe it again.

Charley
I LOVE this idea and quite frankly it is my favorite idea so far because it won't require any measuring if I'm understanding correctly!

So "IF" I can figure out how to get the exact width dado I need for the nominal 1/4" stock I'll be using (seems to actually be .203" and not 3/16" like I originally thought) then I can just cut my thirteen 1.5" x 4' pieces first and use the actual pieces I've cut as my new "fence" position, removing one for each new dado. This should ensure accuracy that the 1.5" pieces will fit tight between each groove/dado since I'll be using the actual stock as my template.

So I'm back to figuring out what to buy to get a .203" dado, but I really like this idea because it's cheap, easy, no measuring, and nothing more to buy.

Any further suggestions?

THANKS!!

--J
 

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Discussion Starter #15
I used a pair of cheep 7 1/4 inch circular saw rip blades and a small shim or two to get the desired width. One pass on the table saw for each dado.

Might take a little thinking to come up with a spacing jig.
Do you mean you would use two Thin Kerf blades stacked together with a few shims from a dado set and that would be all I would need to make my dadoes?

If this would work and would get me to the roughly .203" dado size I need, then I can use the method in the previous post as my "jig."

I've also found a video on YouTube at youtube dot com /watch?v=f9MdXzCrTmU&list=PLkmV4CVyBSn63oSkBtq0kotOCpG6H4jl0&index=30 (I cannot post links yet so you'll have to "fix" this link to see what I'm talking about) called "No-Measure Evenly Spaced Dadoes" where the guy sets the fence just for the first dado, then uses just one spacer, and for each additional dado he simply aligns the previous dado back over the saw blade, puts the same spacer back in, locks the fence, and cuts the next dado.

The video is only a few minutes long and explains it much better than I can in a few lines of text, but I would like to get everyone's opinion here as to whether or not this would be an accurate and good way of making my repetitive dadoes or if I'd be better off using the previous suggestion of lining up all 13 of the 1.5" pieces (roughly 2' worth) and just removing one at a time and sliding the workpiece over for each dado.

Or... If I should look more closely at a third option. ;)

Thanks again for all the great ideas and please keep them coming.

--J
 

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Discussion Starter #16
Sounds like the perfect job for an Incra LS system on a router table, using a 3/16" bit. Once you locate the center of the stock on the Incra system you could even change the bit size so that if you get a batch of 7/32" stock, you still get the same spacing between grooves.

Shoot, with a large enough table, the 32" Incra could handle doing the grooves in the 24" length across the 48" width. (the 25" could do the job in theory, but i'd not want to get that close to the limit of travel with accuracy being that important) Simply start in the middle and work toward the edges with each adjustment of the positioner. Easily repeatable system too.

earl

edit--if you did buy a table saw, and use Mike's suggestion of 7 1/4" blades--the LS positioner works on a table saw also.
Thanks so much for your idea, but I have two concerns with this suggestion.

First, this jig is well over $300 and the table saw I'm thinking of buying is only $279, so it's a bit more than I'd like to spend. With that being said, if this does end up being the best suggestion, then I will just bite the bullet and make the investment.

Second, and most importantly, I've watched several videos on this system and read a bit about it, but since I don't own anything more than basic tools at this point and really have absolutely no experience, I'm afraid I honestly don't understand how I would use this jig easily to make 12 grooves 4ft long each in a 2ft wide sheet of MDF.

I just can't find any videos of this system doing dadoes or anything close to what I'm wanting to do and cannot visualize it due to my inexperience.

If you could point me to a video(s) and/or article(s) on how to use this jig to do the types of dadoes/grooves I want on large pieces and explain your suggestion a bit better I'd be very grateful.

Thanks,

--J
 

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Hey, Jason; welcome!
You didn't mention what your 2' x 4' panels are made of? MDF or plywood?
If they're MDF you are going to be making a LOT of very nasty dust... please don't underestimate how bad this stuff is for your lungs. Plywood's not much better.
An alternate system could be alternating the vertical 'fins' with 1.5" wide full length spacers, butted up tight to the fin and glued to the base panel. Tight fit and no dadoing required. make everything from the same 1/4" plywood.
Hi there, and thanks for your input.

I was planning on using a 1/2" or 3/4" sheet of MDF cut to 2ft x 4ft for the bottom, which is what will have the biggest amount of cutting, since there will be 12 grooves that are 4ft long each. However, this part won't actually be seen as it will be covered by risers and fins (there is a link in the very next post after your original post showing exactly what I'm building other than the dimensions - I cannot yet post links) so if another material would be easier to deal with and not too much more expensive, or better yet, less expensive, by all means please make a recommendation. :) Thanks for your concern about the sawdust. I hadn't yet considered that. I'm looking for the cheapest and easiest method to building these and up till now at least, it seemed to me that MDF would fit the bill.

The fins will be 8" tall each (these are what will sit in the grooves) and I was just going to use 1/4" hardboard which turns out to be roughly .203" in reality. So the plan to make these was simply to buy a 4'x8' sheet, cut it in half to two 4x4 sheets, then rip each 4x4 sheet down to six 8" pieces, giving me the exact number (12) of fins I need in one full 4x8 sheet. Does this sound like the best method to you or would you do it another way and/or use a different material?

I was going to buy precut 1x2's to save time for the risers that go between each fin, and just nail them in at the top and the bottom, so no sawdust there.

So the only things I have to cut are the grooves in the bottom 2'x4' sheet and the dadoes in the top and bottom of the 8" x 2' sections so the fins will be supported on 3 sides.

I LOVE the idea of no dadoing required, but to be honest, I don't quite understand your suggestion.

Would you care to elaborate?

I'm looking for the fastest, not necessarily the cheapest, but the fastest and easiest way that unskilled labor (I want to make it as idiot proof as possible using jigs/templates so I could possibly even hire some neighborhood kids to help since I will be making tons of these) could produce these one the plans, jigs, templates, etc are all figured out.

I'd love to hear more about your idea for no dadoes and spacers, but if I understand what you're saying, wouldn't that take a lot more material and a lot more time?

Thanks,

--J
 

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Discussion Starter #18
Is this what you are trying to build.

If so:
1. Do you plan on buying a router?
or
2. Do you plan on buying a table saw?

In your profile I don't see any tools you have listed (such as a circular saw).
YES!! That is almost exactly what I'm building. I cannot post links yet which makes it difficult to explain certain things so I appreciate you finding that.

The only differences with mine will be that it will be roughly 2' wide and will be 4' tall instead of square, plus instead of 7 wells/dividers it will have 13. But yes, that is what I'm building, and will be building a ton of them.

To purchase these devices, they range between $400-$600 each and I just cannot afford that, plus I can customize it and make a better one all while saving tons of money if I can just figure out the best jig/template/method to use.

I will have to purchase a table saw no matter what, in order to rip the plywood/mdf for the back and for the fins which will be 8" x 4' so I am hoping whatever solution we come up with will not require both a router and table saw at this time.

You're right, I didn't put anything in my profile yet because I haven't made my final decision.

If I have to buy a router, I honestly don't know what I'm going to buy yet.

I plan on purchasing the Porter Cable 6 gallon 150PSI 3 tool air compressor combo kit from Home Depot for $199 which will give me a brad nailer, finish nailer, and stapler which will help with assembly.

I plan on purchasing the Kobalt KT1015 Table Saw from Lowe's for $279 unless you guys think I could get something better for around the same price.

I will also be purchasing a digital micrometer, am looking for a package deal on mostly long (with a few short) clamps, as I have none, and was thinking of purchasing the Vermont American Wobble Dado blade since you can "dial in" the setting and it goes down to 3/16" where, according to the specs listed, all stacked dado sets only go down to 1/4" even though there has been a previous suggestion of purchasing a stacked dado set and using only one 1/8" blade, one 1/16" chipper, and some shims, in order to get to my necessary dado/groove width of .203" (The spec of 3/16" I mentioned before is incorrect) but I really need suggestions on what to buy.

IF I have to buy a router, I really don't know where to begin. I've spent a lot of time watching video reviews and reading reviews on the aforementioned items in order to narrow my list, but just don't know anything about routers, bits, and where to begin.

I currently have a 10" compound miter saw, a circular saw, jigsaw, hammer drill, regular drill, dremel tool, reciprocating saw, and other misc household hand tools that most homeowners have.

I really don't have anything else at all and don't know what else I'll need other than some type of sander but don't know what kind would be best for building these diffusers although I was leaning towards a random orbital sander.

Would it be appropriate to list all the items I already own (since they're pretty standard and nothing special) in my profile or is the above reference good enough for now until I make the bigger purchases mentioned above?

Thanks again for posting that link and I hope this answers your questions.

I look forward to your suggestions and recommendations and truly appreciate your time and effort in assisting me. It's fund to spend other folks money, eh? ;)

--J
 

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Discussion Starter #19
Rockler Router Fluting Jig - Power Router Accessories - Amazon
I like that jig, but it is only for up to 8" x 9.25" I believe and my pieces are 2' x 4' so I don't see how it would work.

I can't visualize how I'd use it for what I'm building but if you think it will work for my 2ft x 4ft sized projects I'd really appreciate it if you could explain to me how I'd use it.

Thanks for your time,

--J
 

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Welcome to the forum Jason
Thank you! I'm already enjoying my time here immensely and think I'll really learn a lot. I cant wait to look back at this, my first thread here, one day and laugh at how inexperienced I was and how far I've come.

My brain hurts from the amount of research I've put in over the last few weeks and the lack of sleep I've gotten, but in all honesty it's been fun, and I've gotten to meet you guys!

Thanks again,

--J
 
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