Drawer-Lock Bit tearout

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Forum topic by SteveT posted 04-11-2018 04:24 PM 1600 views 0 times favorited 15 replies Add to Favorites Watch
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44 posts in 1853 days

04-11-2018 04:24 PM

This is the first time that I have tried using a drawer-lock router bit. I am making drawers from 1/2” baltic birch plywood and using a new Freud 99-240 bit. I got it dialed in using 1/2” mdf then went to make the drawers. I am getting really bad tearout on the plywood. I am using a backer board, but the tearout is occurring as the board enters the bit.

The first time I was running the bit around 15000 rpm. I turned it down to 12000 rpm, but that didn’t help. I’ve seen videos where this worked great, but can’t figure out where I’m going wrong.


15 replies so far

View RobHannon's profile


330 posts in 1140 days

#1 posted 04-11-2018 04:28 PM

Never used a drawerlock but myself, but I suspect it is too big of a bite in one pass. If multiple passes isn’t an option, you could oversize the pieces and cut them down after or have a starter and backer board.

View Loren's profile


10477 posts in 4257 days

#2 posted 04-11-2018 04:36 PM

Are you using a zero clearance fence face?

I’d advise it.

View EarlS's profile


3433 posts in 2957 days

#3 posted 04-11-2018 05:14 PM

I second Rob’s suggestion to leave the boards a bit wide and rip them to width after you finish with the lock bit.

When I run that bit in my router I usually turn the speed as low as it will go and make a couple of passes to get through it. A good backer board also helps. Maybe try to clamp the board to the backer board for a tighter compression on the wood fibers.

-- Earl "I'm a pessamist - generally that increases the chance that things will turn out better than expected"

View SteveT's profile


44 posts in 1853 days

#4 posted 04-11-2018 05:21 PM

Multiple passes would be difficult because I tweaked the height with test pieces. Of course, that doesn’t mean that I couldn’t do it by lowering the bit and raising it slowly until I get it right again. It seems like that would defeat one advantage of this bit. Quick, strong drawer joints.

Or careful measurement. I wanted the sides to be flush with the ends of the front and back. The height is part of that.

I have a split fence whose clearance can be adjusted. I have it set very close to the bit. But no, I did not make a zero clearance fence. How does one do that with a large bit like this? Do I raise the bit into the fence, or lower the fence onto the bit? I admit that I am a little wary, scared :-) of a large bit spinning that fast. If I do the wrong thing, there is a lot of force to throw a board at me!

Thanks for the replies

View Loren's profile


10477 posts in 4257 days

#5 posted 04-11-2018 05:26 PM

Either cut into the ends of your split fence by
closing it around the running bit, or take the
fence faces off and make one continuous
fence face. Put the whole bit behind it and
turn on the router. Pivot the fence to make
a perfect cutout.

I know it sounds scary but it works fine.

View Bill_Steele's profile


636 posts in 2341 days

#6 posted 04-11-2018 07:27 PM

I agree with the advice provided. I use a lock miter bit with Baltic Birch and I experience some of the same problems you mention.

You need a zero clearance fence where the entry and exit to the bit is supported. Do what Loren suggests. You might also consider getting your split fences as close as possible to the bit and then cover (double sided tape) the entire front of your fence with a 1/4” piece of MDF and then cut through it with the bit.

I think making the drawer pieces a little wide is also a good idea so that you can cut off any entry/exit chip-out you get.

Consider making some sort of 90 degree pusher block to ensure that the piece being cut is held squarely to the fence (I got this from the Leevalley website)

View SteveT's profile


44 posts in 1853 days

#7 posted 04-11-2018 09:31 PM

I separated the 2 sides of my fence as far as they would go and clamped a piece of 1/2” mdf to my fence. I slowly moved the fence and mdf through the rotating bit. Not all of the way. I ran two test pieces through and they came out really nice. Hopefully tonight I can get some time to cut a new set of boards for the drawer and run them through the router.

I don’t think that I was clear in my original post. The tearout that I was getting was over 1/2” long, all of the way through the cut. Cutting wider and trimming wouldn’t have helped. In other words, I was really screwing up.

I had been using a guide like the one below. Thanks for the help. I’ll see how this goes and maybe make another fence. But this one seems to work well.

View Robert's profile


3602 posts in 2090 days

#8 posted 04-12-2018 12:58 PM

Ply doesn’t play well with drawer lock bits – or any router bits for that matter.

Edge chip out is easy to deal with as mentioned.

The surface tear out along the cut can be dealt with by pre-scribing a knife line.

-- Everything is a prototype thats why its one of a kind!!

View pintodeluxe's profile


6040 posts in 3423 days

#9 posted 04-12-2018 06:19 PM

Ply doesn t play well with drawer lock bits – or any router bits for that matter.

- rwe2156

That’s what I was thinking. If we want nice joinery on our drawers, we just have to use solid wood.
That said, I have had improved luck using my locking miter bit with two passes. I didn’t adjust the bit height, but rather secured a 1/4” mdf spacer to the fence for the first cut. Then I removed the spacer for the second cut. That was hardwood, but it really improved the cut quality.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View Loren's profile


10477 posts in 4257 days

#10 posted 04-12-2018 06:28 PM

I’ve made some plywood drawers using a
drawer lock joint. I found the problems
were not so bad with a zero clearance fence
and so forth, but I eventually concluded I
was making more fuss of it that was necessary
and stared using pinned rabbets instead.

A not-bad looking joint with plywood can be
made by joining the corners with glued rabbets
or butt joints and then after the glue is dry
drill holes and put lengths of dowel rod in
them. It’s strong, gives the impression they
were built with care, and doesn’t take a lot
of time.

View Lazyman's profile


4545 posts in 1997 days

#11 posted 04-12-2018 09:35 PM

I assume that you are having the problem when cutting with the board laying flat (front or back of the drawer)?

I am a little confused by this statement:
“Or careful measurement. I wanted the sides to be flush with the ends of the front and back. The height is part of that.”

If you set the height correctly to cut the sides, then you should not have to change the height for any other cuts. It is the fence position when cutting the front that determines whether the side is flush with the ends of the front or inset. For the first cut, position the fence so that it doesn’t take a full cut and then move it so that the next pass makes a deeper cut. This shallow scoring pass will help reduce chip out. Since you don’t want to fiddle with the final depth, a simpler approach would be to attach a shim (1/4” PW, masonite or MDF for example) on your backing jig with double sided tape for the first pass. Alternatively you could add the shim to the fence itself. Then remove the shim and make the final pass. You could even use 2 shims when routing plywood to make even shallower cuts in each pass.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

View Rich's profile


5152 posts in 1199 days

#12 posted 04-12-2018 11:19 PM

I’m also confused by some of the ways cuts are being described. The bit is designed to be set up once for bit height and the distance from the tip of the bit to the fence. The drawer sides are routed vertically with the drawer inside face against the fence and the front/back are routed laying flat with the inside face down on the table. Done right, the side of the drawer will be flush with the ends of the drawer face and back. It doesn’t matter if the drawer sides and back are 1/2” or 5/8” and the drawer front is 3/4”. One setup does it all, just like it does with a lock miter bit.

The only time you would make any change to the setup would be to move the fence back if you were doing a rabbeted cut on the drawer front. If I were doing that, I’d do my basic setup, make all of the cuts on the front, back and sides. I’d then set the fence back to whatever amount I needed for the rabbet and run the drawer fronts through a second time. The bit height never changes.

I have the same Freud bit that the OP is using. It should have less tear out due to its large diameter compared to the drawer lock bit that Whiteside and others sell. I’ve had no problem with mine on plywood. One trick is to spin the bit a little faster than you might spin another bit of that diameter, and to feed the board slowly, particularly the drawer side since, as has been mentioned earlier, slicing across the face grain of plywood is not ideal.

I did a detailed blog post a while back about setting up a lock miter bit and locking down the numbers so that future setups could be done without trial and error. The same concept applies here, but only to the fence setting. I have found that with the Freud 99-240 you will get good results by setting the bit height to 0.390”, regardless of board thickness, and the distance from the tip of the cutter to the fence set to the side thickness divided by two plus 0.06”.

That is:

Where T = thickness of the drawer side
F = the distance from the tip of the bit to the fence

use F = (T/2) + 0.06

-- Half of what we read or hear about finishing is right. We just don’t know which half! — Bob Flexner

View Luthierman's profile


222 posts in 1696 days

#13 posted 04-13-2018 01:09 AM

My first thought went to if the OP is using actual Baltic Birch. The stuff sold at the big box stores like the depot, menards, etc, do not sell BB. It is some sort of material made of chinesium. It has a micron thick layer of birch and is full of voids. Looks great until you touch or dare to put a tool to it. I have had massive tear out on that stuff. That’s my two cents.

-- Jesse, West Lafayette, Indiana

View SteveT's profile


44 posts in 1853 days

#14 posted 04-13-2018 02:45 AM

I really appreciate all of the feedback. I’ll try to respond to as much as I can. I haven’t had too much time to continue with this. I hope to have some time over the weekend.

The baltic birch was purchased at Rockler.

The confusion over my statements about setting it up are due to my ignorance about using the bit. I’ve been learning though. When I first started to set it up, I was not sure how height and distance from the fence effected the two different cuts. I’m starting to get a handle on it. I did create a template after I got it set where I wanted and the settings seem similar to what Rich posted. I have the height set at slightly under 10mm which converts to about .390 inches. I have the distance from the fence at 9mm. After making the zero clearance fence, I had to re-adjust the fence. It was very quick to do using the template that I had made. I intend to make a better one.

I like the suggestions to use a 1/4” spacer on the fence and do 2 passes. I will try that. It seems like it would be quick to setup and run the boards through using this technique. I’m adding a few pictures of my adventure.

This was without the zero clearance fence

This is using the zero clearance fence. There is some tearout on the sides

This is the fence I have at the moment.

View Loren's profile


10477 posts in 4257 days

#15 posted 04-13-2018 03:32 AM

Next time you can try scoring a line before
cutting. A marking gauge with a knife on it
would work well for that. You could also
try a shallow pass on the table saw to sever
the fibers using a finishing blade.

I think I had decent results using 1/2” prefinished
maple. Perhaps the finish controlled tearout.
The bit I used was also not the cheapest.

As mentioned above, I decided eventually it
wasn’t worth the hassle. Looks cool though.

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