Router bit for plywood, and I got this ryobi 3 base kit figured out

[mleichtle]

First, I bought the cheap 3/4" blond hardwood plywood from Lowes to build some cabinets. It turns out that its not 3/4" but about a 16th less. Should I invest in one of those special plywood bits to cut the dados? Or just use a 3/4" straight bit. My bt is still in its original form, so I'm a little leary of cutting them on there, the cabinet is going to be 8' tall.

Also, I have the 3 base router kit from Ryobi, I also have the same problems as the other owners of this fine piece of machinery, the two solid bases that don't work.

First the cam lever is a poor design, so I'm looking for a source for a new one. Something like this http://www.hartvilletool.com/product...filiate_id=344 just might work, but the handle doesent look like it will go flat, but stick out perpendicular to the router.

Second, the moter doesn't fit in the solid bases. Well, I realized that the adjusting ring is plastic, and expands and contracts with the temperature, alot. I brought the one good base in the house and let it warm up, and the moter popped right in. So I'm thinking of adding a router base warm up routine to my base switching tasks.

I know, buy a new router. Believe me, I'd love to. But I can't right now without ryobi buying there garbage back, one because of finances, and two my stubborn German principles.

[JetDoc]

Sorry I can't help with the router.

As for the plywood. Right now mlcs has the plywood bit sets on sale for $20. They make life so much eaiser. 3/4" plywood is actually 23/32" unless you are buying the high grade cabinet stuff then it's a true 3/4".

Here's a link to the mlcs bit sets. http://www.mlcswoodworking.com/shops...s/setstrgt.htm

[BrazosJake]

No, make a dado jig for that router and use the next smallest size straight bit (like 1/2"). Plans abound on the internet, but in its simplest form, a dado jig is essentially two straight edges which act as guides custom-fitted to your routers' base for a certain-size bit, with a sub-base of something like 1/4" hardboard which fits right up to the cutline (just like a sawboard for a circular saw).

To make the jig, just glue/screw the guide to your subbase material, making the distance from guide eged to subbase edge slightly wider than the edge-to-bit offset for the router. Do this for each side of the router, and make the subbases wide enough so there's room to clamp and not get in the way of your router base. Then route the edges of the subbase.

To use it, clamp a guide square on your cut line, put in a piece of scrap from the piece that will be dadoed in, then clamp the second guide in place (all good & tight). Then route the dado in multiple passes.

You can get way fancier, but this works and a $2.00 piece of 1/4" hardboard or MDF from the BORG is all you need. Plywood varies too much in thickness, so it's best to cut to fit. Even if you buy a 23/32" plywood bit, it may not fit and a lot of the 3/4" ply nowadays is imported and really 18mm thick, even smaller than the 23/32 domestic.

[LCHIEN]

I'm not going to tell you which way to go on thebits, I'll list the pros and cons.

Fact #1, the plywood is not of a standard thickness but the general rule is it's 1/32nd smaller than the stated size for 3/4" plywood will be 23/32. OTOH, it's not uncommon for them to shave some more off so 11/16th would not be unheard of. You said you measured 1/16th less than 3/4, is this truly .0625" undersized or are you just guessing?

So Using a Plywood bit, you would use a 3/4" plywood bit which is really 23/32". The pro would be that this bit is precise, the con would be that the bit might not be exact depending upon the actual zsize of the wood you have (or might get next time). Another con in my opinion is that the slot you cut will not be as clean as a dado blade in a table saw makes.

Someone mentioned using a 1/2" bit and making two passes. The con is making two passes and getting it just right(e.g. the guides must be aligned better than 1/32 and kept absolutely parallel - but there are ways to do this)

Dado blade - the pro is you can adjust it just so and the sides will be perfectly parallel. The cut is usually quite clean. Cons- can't think of any other than setup issues.

[LarryG]

Someone mentioned using a 1/2" bit and making two passes. The con is making two passes and getting it just right(e.g. the guides must be aligned better than 1/32 and kept absolutely parallel - but there are ways to do this)

And here is the easiest way I know to do this:

http://www.bt3central.com/search.php?searchid=169847

Note that this method is extremely accurate since it uses a sample of the actual material to space the two halves of the jig.

As mentioned, a big drawback of undersized-plywood-size router bits is that while they're great if they exactly match the plywood you buy, there's often enough variation from one batch or source to another that the same size bit won't always be exactly right for every sheet of plywood you deal with.

[Tom Miller]

First, let me commiserate on the router -- I bought the same one, too, when it was on a very good sale. I am getting reasonable results from it, as I'm learning its foibles, so it's not the worst thing in the world. Just last week I bought a universal baseplate for it from Lee Valley, to fix one major weakness of the router. It's the only one I've found that had the hole configuration required for attaching to the Ryobi base.

I also vote against the plywood bits. A good dado fit only has a tolerance of about +/- 0.005" or so. You could have this much variation on one sheet of ply -- I've seen it. The style of jig Larry showed is a really good approach, as it allows you to fit each dado.

One of the reasons I bought the baseplate I mentioned is that it accepts standard PC bushings for template work, which is an alternative to the pattern bit that Larry's setup uses. You'll have to add in a spacer bar during setup to account for the extra width of the bushing.

Regards,
Tom

[cwsmith]

The Ryobi R1802 appears to have a reputation for this particular problem (hard to adjust). I called Ryobi last year and was told that some of these (I didn't expect them to admit to "all") have a defective motor housing, which apparently were oversized. I had mine replaced under warranty and since then it has worked okay.

I realize this is by no means the best router in the world, but I couldn't pass it up at the time for $80. (I also admit to being a bit ignorant of the whole subject at that time... still ignorant, but at least now I recognize it!)

The motor housing is only about $6 plus shipping and I believe it's available from either Ryobi or M and T mower.

CWS

[BrazosJake]

+

Someone mentioned using a 1/2" bit and making two passes. The con is making two passes and getting it just right(e.g. the guides must be aligned better than 1/32 and kept absolutely parallel - but there are ways to do this)

Dado blade - the pro is you can adjust it just so and the sides will be perfectly parallel. The cut is usually quite clean. Cons- can't think of any other than setup issues.

There's nothing especially tricky about making and using a router dado jig. I'm slower than most and was able to look at a picture, construct a simple one in about 30-minutes, and cut nice, tight dadoes. This is simply cutting to fit and assuming the edges are straight on the jig, about the only way to get out of parallel is if the piece that will be fitting into the dado is not parallel (since you register the edges of the jig against it), or the router bit is not perfectly centered in the base. The latter is addressed by always registering the router against the guide the same way. I find this preferable to keeping a big collection of straight bits for every possible material thickness I might want to dado.

I doubt if a dado blade would be a good option for an 8' workpiece, unless it's on a RAS.

[JetDoc]

Wow a lot of people are against the plywood bits. Sorry I said they're a good idea. Just kidding.

I guess I've just been lucky. I get my plywood from a pretty good yard and it has been very consistent in size. I usually take a scrap with a dado cut in it as a gauge block to check the fit. So far I've only come across a piece or two that have been slightly loose. To this point my plywood bits have served me well. If I should start having fit problems a dado jig will be the solution.

[drumpriest]

I have a set of the plywood router bits, and they do work well, but I have also run into plywood that is under the 23/32 size. Very frustrating and annoying.

Makes building a dado jig worthwhile, as it will always just work.

[Jeffrey Schronce]

I am the Anti-Jigist. I have never been a fan of spending lots of shop time making jigs if there is a viable cost effective alternative. Others love jiggery and if you are one of them then knock yourself out.

As Loring points out a dado stack in a TS is great. It does have some limitations and/or things that can be done more easily with a hand held router. Making shelf dados in a long, wide bookcase is a situation where I would use a plywood bit versus dado set in TS with crosscut sled. I think it is important to understand that only the best of dado sets are going to get you nice flat bottoms and little edge tear out. You seem to indicate that your not willing to spend a lot on money on this solution, therefore I don't think a dado set is the answer in your case.
I believe you will be well served with the plywood bit. I ordered a Whitesides for 3/4" from Holbren with free shipping and 10% discount for BT3ers. Link below. This bit is awesome.

http://www.holbren.com/product.php?p...2&cat=0&page=1

Edit : I note on some portions of the link it says 1/2" Ply but it is for 3/4" as noted on other sections of the same page.

Check out the dado below. There is zero enhancement, ie sanding, etc to this slot. It was created with the above mentioned bit. There is zero tear out on the veneer and the bottom is incredibly flat and smooth. Creates a very nice tight fitting joint. Only issue is that as Loring mentioned there is variance between each lot of sheet goods, so be sure to measure before you buy. Other than that, I can't think of a better answer for your original question.

[jgscott987]

Plywood sizing

Just another note on the sizing of cheap plywood... I think the "Blondewood" and "Sandeply" plywood at Lowes and the Borg respectively, are manufactured in millimeters. Most of the pieces I've bought measured an even millimeter thickness (18 or 19 mm for "3/4 ply" I believe)