Dado techniques

[BillG]

I am looking at a new job which will combine solid wood and plywood, with solid wood being the main component.  I need to rout some dadoes into the solid wood to accept a plywood panel, and here is the question.  Plywood is "undersized", but depending on what one means, that can be nominal size or metric - maybe it's both.  How do you guys who use lots of plywood handle this?  Do you search for a bit that fits, or do you use a bit you have that is slightly smaller and then rout a rabbet on the edge of the plywood so that you get a snug fit?

I am looking at 1/4" ply.  I already know that if I use a 1/4" bit, the plywood is going to flop around loose.  I found bits for 7/32", which translates into 5.56mm. I have lots of 5.56mm stuff lying around here, but it ain't a gonna fit in a router.    I also found 5.5mm bits, which is smaller still.  Do I need to buy my plywood first and then look for a bit or just plan on an extra step of routing a rabbet? 

 

[bpitch]

Simple answer to your question

1/2" shank

http://www.amazon.com/Whiteside-SC218-2-Flute-Straight-Router/dp/B000K2CC3G/ref=sr_1_3?ie=UTF8&qid=1344983564&sr=8-3&keywords=sc218

1/4" shank

http://www.amazon.com/Whiteside-Straight-Cabinet-Router-Plywood/dp/B000HRYRGY/ref=sr_1_1?s=hi&ie=UTF8&qid=1344983638&sr=1-1&keywords=whiteside+sc13

Other manufacturers also make router bits in these sizes. and usually they are called straight dado cabinet bits.

 

[pugilato]

You might want to consider Bridge City Tools' Kerfmaster. With this gizmo you can accurately make any size kerf (a dado is a kerf) very accurately. Paul Marcel has very kindly put a video together on how to use it.

Good luck

 

[rjwz28]

What you could do is what a lot of people do including myself is to make an "exact fit dado jig".  Look it up on the net.  There's a bunch of designs that do the same thing.  You use an undersize bit and cut the dado to the exact width of your ply.  Even if you have variations within the same size the jig will make it perfect. It is real easy to make and works great and you don't need exact size router bits.

Rob

 

[rmwarren]

I use any bit smaller than the dado that is needed, with a top pilot bearing, and a couple t-tracks as guides. Set the gap between the t-tracks to the width of the plywood, clamp them to the materials to be dadoed and run the pilot bearing against the track.

[attachthumb=#]

[attachthumb=#]

Infinitely adjustable. You can forgo the plates joining the track together and just clamp each one to your hardwood individually.

RMW

 

[BillG]

Thanks for the replies.  I am going to check out the dado jig.  In the meantime, I went the fast and easy route (or is that rout?).  I found a Whiteside bit locally at our Woodcraft store that is the right size for this particular plywood. 

 

[sancho57]

I am looking at a new job which will combine solid wood and plywood, with solid wood being the main component.  I need to rout some dadoes into the solid wood to accept a plywood panel, and here is the question.  Plywood is "undersized", but depending on what one means, that can be nominal size or metric - maybe it's both.  How do you guys who use lots of plywood handle this?  Do you search for a bit that fits, or do you use a bit you have that is slightly smaller and then rout a rabbet on the edge of the plywood so that you get a snug fit?

I am looking at 1/4" ply.  I already know that if I use a 1/4" bit, the plywood is going to flop around loose.  I found bits for 7/32", which translates into 5.56mm. I have lots of 5.56mm stuff lying around here, but it ain't a gonna fit in a router.    I also found 5.5mm bits, which is smaller still.  Do I need to buy my plywood first and then look for a bit or just plan on an extra step of routing a rabbet?  

I use a 6mm spiral cut bit using my 1010

I like the ones from infinity

http://www.infinitytools.com/searchprods.asp

 

[woodie]

+1 on the Bridge City Kerf Master. I ordered one for the same reason after watching Paul's video. It does require two or more passes with a router but the fit is dead-on and all with standard sized router bits.

 

[BillG]

+1 on the Bridge City Kerf Master. I ordered one for the same reason after watching Paul's video. It does require two or more passes with a router but the fit is dead-on and all with standard sized router bits.

I checked their site out, and it looks good, but it also looks to be unavailable.  I can put my name on a list, which if they get enough names they will make another run...