I was trying to do a 1/4" dado with my Delta contractor's saw. My dado
set is a Freud.
There seems to be a spot on the arbour for the first blade (or any
blade for a non-dado cut) to sit and then there is a bit of a narrower
spot before the threads start. The outer blade has a lot of play in
that position. A chipper is wider and seems to be ok. The dado blade
sits ok when it is on the threaded part of the arbour.
In the end I couldn't get a flat bottom on the dado cut because the
leftmost dado blad had play on the arbour.
Anyone encounter this? Any suggestions?
Don't know if it's been damaged? How close a look have you given the
arbor? Spinning a loose blade could have damaged the leads, or your dado set
may be like mine, also a Freud, but with a greater problem. When I tuck the
blade up against the flange it seems loose by comparison, but seats well
enough, and I don't get any more of a cut on that side than the opposite.
My standard blades seem fine, so I thought it was just my Freud set.
Sure is fun trying to snake the cutters over that arbor, isn't it? Shims
are really a nightmare.
Often, the higher the blade quality the more difficult it is to mount
the blade because the high quality blade manufacturers hold closer
tolereances at the center hole for diameter, ovality, and true
position, offering less clearance in the arbor to blade fit. Of
course, that's a good thing.
Delta, (if this is a domestic saw) used functional go/no go ring gages
rather than multiple tri-mikes measurements to check dia. and ovality
because this guaranteed a functional arbor despite any natural process
lobing. Tri mike readings might miss the " lobes" of the machining
process and check good but not provide a functional fit.
But often the process of cutting an acme thread rolls up an almost
imperceptible burr. The arbor would allow easy mounting of
inexpensive blades with "large" center holes, but make the mounting of
very high quality blades a little more difficult.
I always recommended "touching" the arbor shaft (blade removed, bump
the saw on) with a strip of emory cloth to remove the burr and polish
In the OP's case, it sounds like some damage to that portion of the
arbor, or else the diameters of the blade center holes are at
different spots in the tolerance range. There are other
possibilities, but they are less likely.
I represent no one but myself
No, it's not damage; this is a known problem.
This is the reply I got from Freud when I thought the problem was the
"In almost 100% of the time it is not the dado but the arbor of the saw
that is the problem. Craftsman and some other contractors saw are a
problem because the threaded portion is undersized. This causes the
components to not be aligned properly so you never get a flat bottom."
On 2 Dec 2006 06:53:29 -0800, upand_at email@example.com wrote:
Not to belabor the point and I can't speak for Craftsman, but a no go
ring gage would go on an undersized arbor shaft causing it to be
rejected. My point was that you could measure it with a tri-mike, hit
the lobes, and think it was at the lower end of the range but
However it is a clearance fit. It has to be to get the blade/chippers
on the arbor. That means there can always be a variation in
blade/chipper efective OD by as much as two times the amount of the
And, holding close tolerance on the center hole on a blade is much
less difficult than holding close tolerance on a shaft.
And, having been involved with manufacturing both saws and to a lesser
extent, blades, I would suspect variation in the true position of the
blade/chipper center hole resulting in variable runnout as the primary
cause of variable bottom dados.
Opinions will vary.
Sounds like your threads are worn? My Delta is similar, but after close
inspection with a micrometer, I discovered that isn't actually a shaft
diameter difference between the threads and the "shoulder" up against hte
inside stop. It "feels" that way but it's not. And the "space" between the
smooth shoulder and threads starting is no larger than 1/32 so my dado
blades won't go into the space by any means.
I susped either the arbor is out of spec or something (a blade got "spun" on
the arbor) has worn the threads or something is out of round. That's my
guess, anyway. It's easy to guess; harder when you're the one with the
problem, I know.
Yes, I have encountered this exact thing, also with a Freud dado set.
I used a spacer to bring everything out onto the threads of the arbor.
I've seen small packages of very thin brass at a hobby shop that might
also be used over the threads instead of the shim. Then again, what
about a piece of tape wrapped over the threads. Or teflon tape. You
just need the height matched until you clamp down the arbor nut.
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