Harbor Freight's on-sale $20 dado set has 4500 max RPM. My single-belt, 1.5
HP TS's arbor spins at 4700 RPM per the spec sheet.

- Is the 200 RPM difference ignorable?
- Any downsides to finding a slightly smaller (if my math is right)
pulley for the motor and running the dado at about 4000 RPM? Does anyone
run a "dual speed" TS this way?

Thanks.

-- Mark

On Thu, 02 Oct 2003 18:50:40 GMT, "Mark Jerde"
wrote:

Harbor Freight's on-sale $20 dado set has 4500 max RPM. My single-belt, 1.5
HP TS's arbor spins at 4700 RPM per the spec sheet.

- Is the 200 RPM difference ignorable?
I used to be a professional engineer, and the way I personally see
these things is: 4700 is only 4.4% out of spec. I would never have
designed anything that fails catastrophically if operated 4.4% out of
spec. So I'd give it a go and see if it cuts well.

- Any downsides to finding a slightly smaller (if my math is right)
pulley for the motor and running the dado at about 4000 RPM?
Yes - it's a pain in the neck, so why not try it at 4700 first?

Rob Bowman
Amateur woodworker, professional sawdust maker.

Feed the wood faster. The tablesaw will bog down to less than 4500RPM.
Seriously, this shouldn't be a problem. However, when you first fit the
blades and turn on the saw make sure you duck.

-Jack

"Mark Jerde" wrote in message
...
Harbor Freight's on-sale $20 dado set has 4500 max RPM. My single-belt,
1.5
HP TS's arbor spins at 4700 RPM per the spec sheet.

- Is the 200 RPM difference ignorable?
- Any downsides to finding a slightly smaller (if my math is right)
pulley for the motor and running the dado at about 4000 RPM? Does anyone
run a "dual speed" TS this way?

Thanks.

-- Mark

Rob Bowman wrote:

Harbor Freight's on-sale $20 dado set has 4500 max RPM. My
single-belt, 1.5 HP TS's arbor spins at 4700 RPM per the spec sheet.

- Is the 200 RPM difference ignorable?

I used to be a professional engineer, and the way I personally see
these things is: 4700 is only 4.4% out of spec. I would never have
designed anything that fails catastrophically if operated 4.4% out of
spec. So I'd give it a go and see if it cuts well.

(Sorry if this is a duplicate post.)

Doesn't the energy required to hold the carbide teeth to the blade vary as
the velocity squared? Ie, k.e. = 1/2mv^2 ? If so, (4.4)^2 is nearly 20%
more energy. (I have no idea if this is an applicable calculation.)

-- Mark

JackD wrote:

However, when you first fit
the blades and turn on the saw make sure you duck.

;-) I hope the scar on my left hand from a 100% preventable kickback
accident a couple months back is permanent. It serves as a good safety
reminder. Overreving a heavy dado set of known-to-be-not-Forrest-quality
seems unsafe... Like somthing you'd read in the first paragraph of a safety
article in a woodworking magazine. g "Though he knew the dado set was
spinning faster than designed, Mark started the saw anyway. When the oak
board he was grooving touched the blade, ... "

-- Mark

"Though he knew the dado set was spinning faster than
designed, Mark started the saw anyway. When the oak board he was
grooving touched the blade, ... "

Better:

"Though he knew the dado set would be spinning faster than designed, Mark
finished his 3rd beer & started the saw anyway. When the oak board he was
grooving touched the blade ... "

-- Mark ;-)

On Thu, 02 Oct 2003 20:10:52 GMT, "Mark Jerde"
wrote:

Rob Bowman wrote:

Harbor Freight's on-sale $20 dado set has 4500 max RPM. My
single-belt, 1.5 HP TS's arbor spins at 4700 RPM per the spec sheet.

- Is the 200 RPM difference ignorable?

I used to be a professional engineer, and the way I personally see
these things is: 4700 is only 4.4% out of spec. I would never have
designed anything that fails catastrophically if operated 4.4% out of
spec. So I'd give it a go and see if it cuts well.

(Sorry if this is a duplicate post.)

Doesn't the energy required to hold the carbide teeth to the blade vary as
the velocity squared? Ie, k.e. = 1/2mv^2 ? If so, (4.4)^2 is nearly 20%
more energy. (I have no idea if this is an applicable calculation.)

-- Mark


You're right about there being a square law involved, but wrong to use
an energy calculation. What you are alluding to is the FORCE required
to break apart the brazing of the carbide tips. Force is proportional
to w^2r where w (omega) is the angular velocity (commonly known as
rpm) and r is the blade's radius. So, as Rico pointed out, increasing
w by 4.4% increases the centrifugal force by 1.044^2, i.e. 9.1%, so we
are still not in doomsday territory here.
It's a personal choice: I wouldn't worry about it but if you are at
all nervous then don't do it.

Rob Bowman
Amateur woodworker, professional sawdust maker.

Did someone mention Sawstop (TM)?
Whatever happened to them...

-Jack


"Rico" wrote in message

Well, what if you rammed a hunk of steel into the blade?


Dick

This appears to have been said in jest but there is a good basis for it.
When starting anything, it is a good idea not to stand in line with it until
it has come up to speed.


"JackD" wrote in message ...
However, when you first fit the
blades and turn on the saw make sure you duck.

Mark Jerde wrote:

JackD wrote:


However, when you first fit
the blades and turn on the saw make sure you duck.


;-) I hope the scar on my left hand from a 100% preventable kickback
accident a couple months back is permanent. It serves as a good safety
reminder. Overreving a heavy dado set of known-to-be-not-Forrest-quality
seems unsafe... Like somthing you'd read in the first paragraph of a safety
article in a woodworking magazine. g "Though he knew the dado set was
spinning faster than designed, Mark started the saw anyway. When the oak
board he was grooving touched the blade, ... "

-- Mark


Appears you're answering your own question. Seem's like you know that HF
is less than Forrest quality and you know how fast your saw spins and
you ask if you should ..... Knock yourself out



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"Mark Jerde" wrote in message
...
Harbor Freight's on-sale $20 dado set has 4500 max RPM. My single-belt,
1.5
HP TS's arbor spins at 4700 RPM per the spec sheet.

- Is the 200 RPM difference ignorable?
- Any downsides to finding a slightly smaller (if my math is right)
pulley for the motor and running the dado at about 4000 RPM? Does anyone
run a "dual speed" TS this way?

Thanks.

-- Mark


Risk analysis says that you are exceeding the design spec by 9%.
Consequences of failure are a lump of sharp metal coming off the blade.
Possibly limit the risk with effective guarding. Further risk of the
shrapnel bouncing back into the blade and causing a grenade effect.
Work out the tip speed to really worry yourself. You won't see it coming.
Your risk.

John

You are right, this part was half serious. Stand to the side when machines
start up.

-Jack


"CW" wrote in message
. net...
This appears to have been said in jest but there is a good basis for it.
When starting anything, it is a good idea not to stand in line with it
until
it has come up to speed.


"JackD" wrote in message ...
However, when you first fit the
blades and turn on the saw make sure you duck.

Henry St.Pierre wrote:

Appears you're answering your own question. Seem's like you know that
HF
is less than Forrest quality and you know how fast your saw spins and
you ask if you should ..... Knock yourself out

My question is whether or not anyone runs a dual-speed table saw to run
blades such as these safely. I don't see any reason why it couldn't be
done, but I don't know very much about the engineering aspects -- as
evidenced by my misapplication of kenetic energy & binding of carbide to
blade.

On a single-belt contractor saw like mine, it would be trivial to build in a
multi-pulley setup similar to my drill press. I'm wondering if someone in
the group knows that this a Bad Idea (TM).

-- Mark