I need somone to set my expectations re: biscuit joinery.
I just got my dandy new PC557 (and 1000 free biscuits) last night and was
anxious to fire it up today. After giving the directions a good thorough
going over, I grabbed some 3/4" x about 15 or 16" and was gong to biscuit
join their edges - 2 #20's about 12" apart. The tool is really smooth - no
jerking or moving but still, you want to hold eveything flat and stable, or
I can see where it could try to move around a bit.
Well, dry biscuits in the slots have about a 32nd clearance, which of course
translates to the same vertical movement when the joint is together. I'd
hoped for a much more snug fit than that. You can also slide the 2 joined
edges laterally about an inch either way - but that's not a problem - you're
lining up on your original biscuit marks anyway - but the vertical movement
bugs me a bit.
After reading all the stuff here about how those biscuits swell, I thought
maybe with gluing them up, the swelling would stabilize the joint a bit. No
such luck - I even got aggravated and soaked a biscuit in a glass of water
for about 15 minutes - still loose in the slot. I just went back out to the
shop (about two hours later) and you can still slide the biscuit in and out
Have I set my expectations too high about how snug the joint would be with
this method ?
Sounds like undersized biscuits or slightly oversize cutter--is there a
burr on the edge of the cutter by any chance?
The slot w/ my Ryobi is snug enough that it takes a really firm tug to
pull a dry one out of the slot directly normal to the face.
Horizontal alignment is, of course there to allow some movement, but the
vertical slack shouldn't be anyways near 1/32"...
Or, more likely is the blade truly flat or did the cutter get dropped,
perhaps? Or is it aligned on the arbor or a small burr under it to make
it not quite true on the shaft (wobble)?
Make sure you hold the tool firmly on the surface of the workpiece and
don't let it tilt during the slotting operation...
I have a 557 (and a 555 before that).
My biscuits go in easily, but fit snuggly enough to not readily fall out.
Just for fun I did a joint up once with just water and it was pretty solid.
Occasionally if I am a little slow on my gluing, I have to really crank on
the clamp to get it together.
I would say your biscuits are undersized or you are not using the joiner
1) The biscuits could be bad (too thin). I buy Porter-Cable brand just
because I like the container. But check the biscuits. Most would be too
tight to fit, but supposed to slide in nice and snug.
2) The blade may not be tighten or may be crooked.
3) You should be holding the fence tight to the wood, thus nothing would
be able to slide or move, only a "take-your-time" push the motor straight
and back easily.
4) If all fails, take it back. If you still experience the same thing,
then it must be something you not doing it right.
After all is satisfactory, search for O'Shim (I forgot what name it was).
Well, sure, but they do expand when the glue gets them wet. Maybe they
aren't undersized, they're just compressed more than you'd expect, and
they'll expand to the same size once installed? Easy enough to test...
I have only used Porte Cable brand biscuits. I have found that the quality
control on the biscuits is not perfect. About 1 out of 20 will fit sloppy in
the slot, or won't go in at all. When this happens, I toss it and grab
another. As another poster stated, it could be that your cutter is
oversized, or burred, but I find this hard to believe. Have you trid cutting
multiple slots? Do they all do it?
Joe in Denver
my woodworking website:
I picked up my PC 557 this weekend (should have done it through Amazon,
but didn't plan far enough in advance.... sigh)
I also noticed the same thing about sloppy fit. I was able to align my
board edges (mostly) when I had the clamps put on with very light
pressure, and then finished tightening.
So - now I'm curious - what should the biscuit thickness and slot
thickness be? (I'll get out the dial calipers tonight....)
Hmmm...maybe a bad run of blades? That's sounds like the most likely cause.
Used to have the specs on this...no matter.
My DeWalt blade measures 0.157 on a tooth, and a cut slot measures the same.
From 1/2 dozen biscuits, I'm seeing 0.157-0.160.
Okay, just located Chuck Ring's notes, some of which came from Hank Metz, who
taught me about these things years ago, so this should be fairly accurate.
The slot should be 5/32 or 0.156 wide.
Biscuits are spec'ed at .0.148. (However, I've never seen them that thin.)
The biscuit should swell with water to 0.164, and stay close to that when it
I measured mine last night and did some more joints, and didn't have
the same problems I was having. The slots I measured came out right
at 0.156 to 0.157. The biscuits I forget exactly but I believe they
were 0.148 +/-0.002.
I assume that my problems were operator error on the first couple of
joints I made - not holding the tool or workpiece steady as I made the cut.
I still had some vertical alignment issues last night - but it is more
along the lines of being able to catch the fingernail as you slide
across the joint. I figure that is only a couple of thou difference and
easily taken care of by the sander.
I hadn't used a biscuit joiner until the last couple of days and I am
really liking it. Lets me make no-fastener joints in places I couldn't
before, and is SO much faster than using the doweling jig. Not to
mention a whole lot more forgiving on alignment issues than dowels. I
put some solid banding (2.5" wide) on some plywood last night using it.
I ended up using 16 biscuits and didn't have any major alignment
issues. I couldn't imagine trying to do that with dowels and not having
at least one hole be off just a hair - enough to be a pain in the....
It was somewhere outside Barstow when "Jim Bailey"
Why ? Get your vernier and measure it - slot too big, or biscuit too
Over-width slots are usually caused by wobble, Either you wobbling the
tool, or the blade having some wobble in it. I'd stick a dial gauge
on the blade and turn it over by hand to see if some teeth were higher
than others, either as a mis-aligned blade, or as a single damaged
As others have noted, it could be either the joiner or the biscuits. Years
ago, Ryobi had one that cut oversized slots with the same results. Many-many
past postings here from that one. I have seen some biscuits that were rather
loose, but nearly all became at least snug when wet. If yours are still as
loose, I'd bet on the joiner.
Either get ahold of some other biscuits to try or, better yet, get or borrow a
dial caliper to measure both the slot and the biscuits (both dry and wet). If
either set of numbers are off, you'll have the problem. While several
different things could cause the problem in the joiner, you really don't care
as long as you know who's at fault here.
In the meantime, don't bother trying to use this or you'll just have alot of
On Tue, 01 Mar 2005 19:42:59 GMT, "Jim Bailey"
Left and right movement is determined by the depth of the cut. That is
adjustable as a fine tune adjustment other than the coarse adjustment for
the other biscuit sizes. Left and right movement is good as it permits you
to be a little lax with cutter alignment and marking the wood.
Thanks to all of you ! Here's some answers to your questions and where I'm
1. I don't have a dial indicator available so it's going to be difficult to
check runout, or if the blade
tips might be offset from one another.
2. I do have dial calipers - the biscuits and the tips of the blades all
measure in the vicinity of .155
+- .005 with the blade tips being pretty consistently on the low end of that
3. I tried a couple of different woods just for completeness. Same results.
I was also very careful that
the unit didn't move around while I was cutting.
4. I called PC and they transfered my call to a local (90 miles away)
service center. They said that if I couldn't bring it in to them, to mail
it to them and they'd look at it.
5. The biscuits came in a PC box - I going to assume they're PC. They're
marked USA20. They we'er a prt of the Amazon package - 1000 free biscuits
with 557 purchase.
So - I guess it's mail it to them at this point. I'm a bit dissapointed.
Your blade and biscuits sound okay. Suggest you measure a cut slot. If that
comes out larger, it's the joiner. If the slot width is same as the blade
tooth, something's being missed here.
On Tue, 01 Mar 2005 22:25:46 GMT, "Jim Bailey"
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