On 2012-02-22, wrote:
On 20 Feb 2012 05:11:58 GMT, "DoN. Nichols"
wrote:

[...]
The only *correct* tension on these machines is as hard as you
can twist the knob by hand -- and perhaps a little more. The tension
knob is too small for the task. :-)
[...]

Thank you all.

To answer some of the points that have been raised:

[ ... ]

3) The back guide bearings do not touch the blade when not cutting.

This eliminates my primary guess.

[ ... ]

d) The manual says this should be a M8 screw. This was clearly wrong,
the screw is 5/16-18.

You know that 5/16 is *very* close to 8mm?

0.3125" ~= 0.315" as I said, *very* close.

18 TPI calculates out as 1.411mm -- and the M8 is probably
M8x1.5, so it will go in a few turns before wedging.

So -- the *screw* may be 5/8-18, but the threaded hole is
probably M8x1.5. Did you try purchasing a M8 screw and trying it?

The two are close enough so I would expect my "screw chkr" to
not tell the difference. You would need a proper thread pitch gauge
engaging perhaps a half inch of screw length to tell for sure.

I have made that mistake, and put 5/8-18 setscrews in some
Phase-II BXA sized (Series 200) tool holders. To get them to go all the
way through, I had to run a proper 5/16" gun tap through the holes --
but this now means that all my tool holders use precisely the same Allen
key, and the threads were close enough so there was no ill effect other
than dulling that tap. :-)

I tried a different 5/16-18 screw to get into
the hole (I thought there may be an alignment problem) and it behaved
the same way - it would turn about two threads and then it would
become difficult to turn.

That again sounds like you need a proper M8x1.5 setscrew.

e) I cleaned the set-screw hole, blew it out with compressor, looked
down with a light, poked about there with a stick to no great benefit.
f) I run a bottoming tap as far as I could but still was not able to
get the screw in far enough to hold the wheel securely.

Because you could not get a through hole without succeeding in
pulling the wheel.

g) In the end I made a little 1/4" diameter plug, dropped it in the
hole and screwed the set-screw after it. This did the job.

Probably a good enough fix, now that the threads are some
combination between 5/16-18 and M8x1.5. :-)

h) The blade now runs much better after I re-adjusted the
tracking/tension. However, the driven wheel is touching the cover.

O.K

I left it at this point. I do not pretend to understand any of this. I
shall try cutting something on Thursday...

Good luck with that,
DoN.

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