Plywood bit advice?

[BrianStark]

Hi,

I am planning on making some garage cabinets as my first project with a new router. I plan on buying a 23/32" plywood bit for the project so that I can make some dado cuts for the 3/4" plywood that I will be using.

If this project goes well, I want to tackle some other project that will require plywood bits for 1/4" and 1/2" plywood.

I am open to the idea of buying a plywood bit set, as I believe I will use the other bits. Now what I have noticed is that some companies (Rockler and CMT) have plywood bit sets for 23/32, 31/64, and 15/64. Freud on the other hand has a set with 23/32, 15/32, 11/32, and 7/32 bits.

My question for those with experience using plywood bits is this -- is it better to have either a 15/32 or 31/64 bit for 1/2" plywood and likewise, it is it better to have a 7/32 or 15/64 bit for 1/4" plywood?

Or, is this one of those cases where I simply need the right bit for the size plywood I am using? In that case, it may make sense for me to pick up the Freud set, and then round out my collection with the 31/64 and 15/64 bits when needed.

Part of my confusion right now is that I am not sure if 1/2" plywood is more commonly found as 31/64 or 15/32 -- on the other hand, the difference in size doesn't seem that significant.

Of course, I can always pick up only what I need for right now and just get a 23/32 bit...

thoughts?

Brian

[drumpriest]

I have found that plywood bits aren't that great. The reason is that some of the plywoods out there aren't exactly 23/32 etc....

Lately I've been using my dado for that sort of work, as I can measure the ply with calipers and with shims get a really good fit.

For the 1/4" stuff, I measure and cut kerfs with my regular TS blade.

[LCHIEN]

I think the answer to your question is that the plywood varies from sheet to sheet. And some bits will work better with some sheets.

[BrianStark]

Thanks...

I think the answer to your question is that the plywood varies from sheet to sheet. And some bits will work better with some sheets.

thanks for the advice. it sounds like I will be better off in the long run if buy a caliper to measure the plywood (which I haven't purchased yet), and then decide if there is an appropriate plywood router bit I would like to purchase. In the meantime I will show some self-control and I will focus on picking up some other tools that are on sale right now -- knowing that I can use those regardless of the size of wood I will be purchasing at a later date.

Brian

[Uncle Cracker]

I have both the 1/32" under and the 1/64" under bits, and have used both pretty much the same amount. As stated before, all plywood is not created equal, so when I need a ply dado, I measure and use the bit that fits the best. Definitely cut a test groove to confirm the fit you choose. I have also found ply that fits neither, in which case I use the bit that's just too small, and hit the edge of the ply with the belt sander to get the right fit.

[cgallery]

I'm going to go one further than what has been said and add that plywood thickness sometimes even varies within a sheet. Extremely frustrating.

[BigguyZ]

I just ordered the plywood bit set from Holbren a few days ago. I'm hoping it wasn't a mistake... I have to make dados 18" accross some long carcass sides (about 44" each). I figured it'd be easier to use a fence and router than a TS with that large a piece, but if the bit won't work for the plywood I buy....

[bthere]

One thing that has helped a bit for me is to take your standard plywood bits and dado a small piece of scrap. When you go to pick your plywood, take the scrap and test fit it along the edge of the plywood. You can usually find pieces with the right thickness to fit your bit.

[LCHIEN]

I have both the 1/32" under and the 1/64" under bits, and have used both pretty much the same amount. As stated before, all plywood is not created equal, so when I need a ply dado, I measure and use the bit that fits the best. Definitely cut a test groove to confirm the fit you choose. I have also found ply that fits neither, in which case I use the bit that's just too small, and hit the edge of the ply with the belt sander to get the right fit.

That's kind of the solution - get the smaller bit, if the ply is a bit too thick (probably not more than 1/64th) then chamfer the (bottom) edge a bit with the belt sander, or even a sanding block at about a 15-20 degree angle, it'll make a nice wedge fit.

[LinuxRandal]

IMHO, the nominally 1/4" dado bits might be the only ones worth having. With plywood thicknesses varying, I use the piece I am setting into the dado, to set the thickness of my dado's. Then I use a smaller bit, and make passes, from one side (one line) to the other.

Searching here or google, or other sites will help you see how to do this. As an example, googling perfectly sized dadoes gave me this link:

http://www.woodworkingtips.com/etips/etip102700wb.html

For a 23/32 dado, use a 1/2" bit and two passes.

[LarryG]

I'm with Linux ... use ordinary straight bits and make two passes. I use exactly the technique he describes. This eliminates both the need to buy additional special bits, and the problems with variations in plywood thickness not matching those special bits.

And it may be that you don't even have to make an extra pass beyond what you're already doing (or should be doing). Instead of cutting the dado to its full width but only half depth on the first pass, and then to full depth on the second pass, you can make two passes at full depth. IOW, instead of deepening on the second pass, you widen on the second pass. (All this depends on the size of the groove you need vs the size of the bit you're using, of course.)

[gwyneth]

Amazon had Woodline's nine-piece straight bit set on sale a while ago. It's not billed as "plywood bits" but has over- and unders for 3/8, 1/2, 5/8, 3/4 (from memory).

IMO, the answer is accumulating a diverse set of straight bits by grabbing any high-quality one, of any size, when it's on sale. Maybe you don't need a 5/8 with a 1 1/2 cutting length now (hypothetical example), but if it's a good one and it's on sale for three or four bucks, get it.

[Uncle Cracker]

Can one really have too many router bits?? Methinks not!

[gwyneth]

Can one really have too many router bits?? Methinks not!

It's difficult to have too many router bits, but impossible to have too many straight router bits.

Perhaps that should be rephrased, though--it's pretty certain that nobody ever thought s/he owned too many. (No matter if others thought s/he owned too many.)

[LinuxRandal]

It's difficult to have too many router bits, but impossible to have too many straight router bits.

Perhaps that should be rephrased, though--it's pretty certain that nobody ever thought s/he owned too many. (No matter if others thought s/he owned too many.)

Gwyneth, not picking on you!

You all need to HOPE some people have too many bits! That is why Holbren had the raised panel bit sale. A good thing for us as consumers (tool addicts).

On the other hand, as an individual, you have too many router bits if :
A. You can't open your drawers because they are full of them.
B. You have no money for wood, because you have spent all your money on bits.

LOL