Larry Jaques wrote:
On Fri, 30 Sep 2011 13:51:19 -0700,
wrote:

Larry Jaques wrote:
On Fri, 30 Sep 2011 08:14:50 -0700,
wrote:

(...)

Question: Why would it be so bad upside down when it isn't right-side
up? Could it be the addition of the table thickness? Pull the shoe
and mount the beast to the new, thin table. Let me know how it works.

Read on. I agree with you that relative movement between
the workpiece and saw blade appears to prompt lateral
oscillation of the blade and results in grabbing.

Vertical or lateral? You didn't specify, so I took it to mean
vertical separation between the table and workpiece.

Lateral blade movement. It waggles in the kerf and
can appear to be a much wider blade than it actually is.
Bingo, we have a bind. One can also induce lateral blade
movement via insufficient base pressure against the
workpiece. (excessive vertical separation).

Wait a minute,
you just said "workpiece and blade". How is that happening? If it's
sliding up against the side of the blade, it will begin oscillation.

Yup. The end of the blade is totally unconstrained so it'll
break into oscillation if it taps itself against the inside
of the workpiece kerf once or a few times.

Gitfiddle wire'll fix 'er right up, overcoming that tendency.

If I were gonna do that, I'd figure out how to power a
hacksaw blade instead. Can't beat that for cheap and easy to
locate.
http://treadleit.info/sites/default/files/mainsite/OLDfiles/Scrollsaw-MillersFall-1886A.jpg
They will sell like hotcakes!

With 'His Stockiness' holding the saw conventionally, there
does not appear to be enough relative movement to cause
much oscillation, so very little grabbing results.

How thick was the additional table when you tried it upside down?
I don't think you addressed that.

I vaguely recall it was 3/4" ply clamped in a Workmate.

A foot alone couldn't provide the necessary force and still
allow the user to easily direct the cut.

(...)

Ayup. I've felt that with the recip saw many times. The 12" blades
are the worst.

And a Sawzall into a steel bolt clamped in a vise can
really teach you some dance moves, if you attempt to
use an unworn part of the blade.

Try cutting a sink out and find a subterranean tubafore lurking a
couple inches below the substrate. Instant pogo stick, all the way to
the top of the counter.sigh

Frustrating, that.

(...)

Drill the tip of the blade, run a guitar wire through it, and support
it at the top. It should end your troubles. Use the beaded end on top
so you can drop a holey piece on it for further cutting.

It just might, with enough vertical pressure.

I doubt it would take more than a dozen pounds. Give 'er a try.

Much cheaper and faster to put a transmission on my existing
band saw. I *know* that'll work.

A first - order test would be to clamp a workpiece in a vise
and attempt to cut it with much less base force than usual.

"base force"? Or run a ball bearing holddown right next to the blade,
springloaded at the top.

That is the BladeRunner approach except for the spring loading.
It does appear to work OK. It ain't fast, even in wood, though.

No. Bandsaws are light years ahead for speed in wood/metal cutting.

No. I agree with you, too.

(...)

That is my story and I'm sticking to it.

All the way to the San Josie Sanitarium, eh?

More highly paid men than you have tried that one, Larry!
They had to answer several Embarrassing Questions.

Oh! The Somesheimers Question, eh?

Exactly. Not all. Some.

My take-away:
What if you made a 'virtual' top guide, immune to swarf?
Several displacement sensors and electromagnets dynamically
phase - cancel lateral acceleration of the blade,
straightening it in real time.

Quick, cheap, and easy. You'll have it done in half an hour, wot?
Hurry, the patent office closes at 4 on Fridays.

I Can Over - Complicate Anything!

Talk to Bill over on the Wreck. He's one up on ya.

There are *two* of us? OMG.

--Winston