Thread: Norris-esque Blade Adjuster

I have just been reading Jim Yehle's account of his making of a dovetailed smoother. He shares the same views as those made here about the adjuster and it's omission.

His adjuster is interesting in that it provides a large bearing surface for shaft rotation within the traveller. The St James Bay adjuster has very little bearing surface at that junction. Whether there is discernible play when the StJB adjuster is installed is another thing. It would be simple to make a one piece traveller incorporating the features of Jim's and avoiding the complexity.

Making a Dovetailed Infill Smoothing Plane - Jim Yehle

And Derek, I would like to see your adjuster and hear your comments if you have the time.

BT

For the engineer in you AB ...

(Quoted from this page ... OldTools Archive -- thread with message 34259 )

There is an interesting comment below "(Note that the Norris compound screw makes for a coarser adjustment, not a finer one as is sometimes believed.)"

I understood that the Norris adjuster was a small LH threaded rod inserting into a larger RH threaded rod (or vice versa) - thus counter-acting the action of each other at different rates at each turn of the knob in order to produce a very fine adjustment.

There is a problem that needs investigating here.

- - - - - - - - - - - - -

34489 Jeff Gorman <Jeff@m...> Jan-15-1998 RE: Stanley 604 vs. Norris A5

Ray T Smith wrote:
>
> I hope Jeff is asleep this time around....maybe I can slip this
> past him :^)

Refusing to rise to bait point-by-point, 8-), might one respectfully
suggest that those who wish critically to evaluate Ray's enthusiastic
summary, look into the depths of the archives where I estimate that
we have covered all his points (ad nauseam to some no doubt, with
only one ad vitriol that I recall).

Whazza 604 anyway? 8-).

However, since lever caps, adjusters, friction and all that have been
recent interesting topics, here's an previous posting from my store:

"Given a long and strong enough lever and a suitable fulcrum, it is said one
could lift any load. This is because the user's end can be made to
move a greater distance than the load end. The ratio of the distances
being known as the "velocity ratio" (ie the distance moved by the
effort divided by the distance moved by the load). It plays a
fundamental part in determining the efficiency of a machine.

The blade-shifting system in engineering terms, is a machine. The
distance moved by the effort is related to the diameter of the
adjuster knob.

I measured the increase in set by means of a dial gauge resting at
right-angles to the sole of a 51 year old Stanley #4 smoother and a
late production Norris smoother. The actual distance moved by the
blade, measured along a 45 degree frog will be 1.4 times the actual set.

(At Patrick Leach's instigation, a few of us discussed the bed angles
of Norrises some time ago, and those who a responded showed that most
have an angle, as near as makes not much difference, of 45 degrees,
ie the same as a standard Stanley smoother, whatever some writers may
say).

The diameter of the Norris adjuster is about 22.5mm. Playing
mathematicians tricks, one can say that the distance moved by the
effort will be 22.5 x pi. One revolution of the Norris produces a set
of approx 1mm. So the velocity ratio is 22.5 x pi/1 x 1.4 = 16pi. .

The Stanley adjuster diameter is 31.7mm approx. One revolution of my
Stanley #4 smoother adjuster knob, gives a projection of approx
0.3mm.
So the velocity ratio is 31.7 x pi/0.3 x 1.4 = 75.5pi.

(Sorry about the metric, but my dial gauge has seen the light).

So the velocity ratios, and hence the efficiency of the adjusters in
overcoming friction will be 75.5pi/16pi = 4.7.

(Note that the Norris compound screw makes for a coarser adjustment,
not a finer one as is sometimes believed.)

Of course one cannot fully quantify the difference between the
adjusters of the two planes because the actual relative frictions
between the frogs will not be known. However, the differences would
have to be in the order of 4.7 to bring the effort to be the same. This
would take some doing, so I reckon one could justifiably say that the feed
on a Stanley is significantly easier to adjust than on a Norris. Anyway my
fingers tell me so, so there! 8-). There are other factors, such as
the ability to tweak the adjustment of a Stanley smoother while still
retaining the grip on the tote.

The weaker adjuster might explain why I and some infill users /have
to/ ease the lever cap screw to adjust the blade, yet the Stanley/Record owner need not do so, and in fact until this discussion arose, I had never heard of a plane being adjusted with a cam-type lever cap released (and at one time I related to well over a hundred woodworkers).

Now I understand why a one-presssure lever-cam is OK for the Stanley,
but perhaps less suitable for the Norris. Of course, fine adjustment
of the lever cap is easy with this type of plane, but is not
accomodated by the design of a Bailey mechanism. Funnily enough UK
Record are now producing planes with a screw-adjusted lever cap. I
find it unsatisfyingly small in diameter.

One snag with loosening the Norris lever cap for a preliminary
adjustment is that if there is some give between the frog and the
blade (or maybe for some other reason), tightening the screw can
increase the set. In fact I was taught that this was the way to do
the final setting on this type of plane, and while this has been
confirmed by other users, it reportedly does not always work. It certainly does on my plane, and because this also upsets the lateral adjustment,
this is one reason why I don't use it. (No, it isn't for sale. It will do
as a photo prop sometime, 8-)).

The mechanics of the lateral adjustment is also interesting. For
homework, to the lateral adjustment systems, apply the principles
outlined above, /assuming/ that the blade pivots about a point just
behind the bevel."

Then ask yourself whether the Stanley, having independent feed and
lateral adjusters, is not a better-conceived design.

Apologies if the layout of the re-post section comes out badly
formatted at your ends.

Jeff
--
Jeff Gorman - West Yorkshire
Jeff@m...

Quoting from another good web page: The Norris story


The Adjuster Shortcomings

Although the Norris adjuster is without doubt an ingenious invention it is not without its problems and is considered by its critics to be not as positive or robust at the Leonard Bailey type adjuster in use as early as 1867 and still used on many makes of plane to this day. Apart from the “far too fast” observations the mechanism is easily damaged over time by rough handling with the lever cap set too tight whilst adjustments are made. On the double screw type this results in accelerated thread wear and bellmouthing to the internal threading on the main shaft.

Various modifications have been tried, based on the Norris design all having advantages and disadvantages. Some adjusters have been made having a double screw but having two right hand threads or differing threads per inch. This results in a plus and minus combination known as differential threading and can be calculated to give a very fine adjustment indeed. However the combination of the two threads still result in backlash and the same bellmouth problems. Perhaps the best solution is a single thread of 40 threads per inch on the main shaft coupled with a superior bearing on the sleeve of the floating ring, together with the grub screw in the rotating hub which is mounted in the base plate with a shouldered bearing and a back nut to adjust the lateral friction. I am lucky enough to have a brother-in-law who made such an adjuster and the result is microptic with a minimum amount of backlash. However one minor problem remains when ultra fine adjustment is required. The problem is brought about by the need to slacken off the lever cap in order to set both depth and lateral adjustments allowing the cutting edge of the iron to lift slightly off its bed adjacent to the mouth. Setting the plane in this mode the subsequent tightening of the lever cap results in the iron bedding back down giving a slightly coarser set. This is unnoticed by most users but has been observed by those preferring to use the time honoured tapping method on planes without adjusters. It would seem appropriate to mention here that I have fitted these adjusters when re-building other makes of planes broken beyond normal restoration. This has produced two superb user planes that would otherwise have been scrapped.

Another link:

The Norris Adjuster - Handplane Central