Mark VII Headstock Reassembly

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The rear wedge, the smaller flat washer and a lock nut complete the lock shaft. The rear wedge has the flat end facing the middle. The nut will be adjusted later.

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This lock mechanism resembles the 505-520 carriage lock(spring tension provides locking force).<<< Tain't so-spring provides release force.

According to the manual, a spring is missing that I believe goes into a through hole in the shaft. I am not sure of its purpose, but it most likely provides a detent in the normal/locked position of the crank. The two sides of the crank differ near the pivot pin.



EDIT: This assembling was correct, but, did not function correctly. Post #20 describes the problems and their correction.

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The quill reassembly is essentially the same as a Mark 5/V/7. NO, NO, NO!!! The quill shown here apparently is from a Mark V.
I have acquired a 'real' Mark VII quill, but have not disassembled it (yet). I will add to this thread at the end when I reassemble it.*

* That has been added at post # 25.

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The quill stop ring and rubber bumper are installed on the outside of the quill.

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The shaft and bearing are slid into the quill.

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The retaining ring is installed.

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And finally the knurled collar.

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I am suspicious that this quill assembly is not 'original'. The blox shaft and the two part shaft are why. TRUE! It Ain't!

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Much of what appears below is correct, but, in the end some major wear issues caused a different method for attaching the control knob to the shaft. I will add a link to a separate thread that addresses not only that 'issue' but some others as well.

http://www.shopsmith.net/forums/showthr ... post159029


The Reeves drive part of the speed control is essentially the same as the Mark 5/V, but the control is different. A cam replaces the pork chop etc. and a large knob replaces the crank. The original had a plastic cam that was its major weak link(many melted). This one had a third party cast aluminum cam. Still does!;) Notice the 'different' screw. Gotta make sure it goes in the hole already boogered by it.

speed control 1.jpg (446.72 KiB) Viewed 4474 times

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The cam is secured to the shaft by a tension pin. The shaft may be positioned either of two ways(it does not matter which since the hole and shaft flats are not offset). The cam hub notch faces the shaft. The pin is driven flush.

speed control 2.jpg (408.92 KiB) Viewed 4481 times

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Now a discussion re the cam follower on the end of the control sheave. The opening in the follower yoke is wide to allow for the changing position of the idler shaft when the eccentric is rotated for tensioning the belt. The yoke is also wider in one side(the pivot is not in the center). I believe the wider side must be towards the back side of the headstock(the same as the direction the eccentric is rotated to increase belt tension). EDIT: Ignore the underlined statement above. The follower is 'fatter' on one side than the other. The 'skinny' side faces the increasing diameter of the cam. That would be fat side 'down'. Since the pix are taken from the bottom, you are seeing the fat side.

This pix was taken with the eccentric adjusted to its rearmost position.

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This pix was taken with the eccentric at minimum tension setting.

This pix also shows the notch in the control hub. The cam notch and this notch allow the follower to move further towards the shaft at fast speed.

speed control 4.jpg (341.41 KiB) Viewed 4468 times

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Now for an explanation of how this control works.

The 'base' has two 'bullet' spring loaded detents(brass colored thingeys near the top). The knob has 29 'grooves' around the center. The detents are spaced two grooves apart. Normally the two detents are both in grooves, but at the ends of the grooves, the knob will move one more groove by having only one detent in the 'next to last groove'. This creates 30 distinct detented positions.

The three mounting screws are in curved slots. The base can be positioned for slow speed setting by rotating the base.

There is pin on the knob(6 o'clock in the pix) that rides in a groove in the base. At the top end of that groove is an adjustable stop. This is in essence a high speed stop adjustment.

speed control 5.jpg (301.52 KiB) Viewed 4465 times

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An extra(it is not shown in the manual) spring washer came with it.

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It was originally(as I acquired it) between the knob and the base.

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I put it together with the washer 'as found;. The retaining clip for the knob went on fairly easily.

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That caused the knob to be pushed out away from the headstock creating a large gap.

So I moved it to between the knob and the retaining clip(made getting the retaining clip on much more difficult!)<<<Not a good move! See post 19 below.

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Adjusted for slow setting.

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Then fast setting.

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Not sure I like the wave washer where it is. Knob turns hard. Not totally satisfied with limit settings. Time will tell if things stay as they are.<<<<<<<< Nope!

A lot of guessing about the way things 'should' be.

This has been addressed in post # 19 below.

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Another thingey not on a Mark 5/V is the carriage to headstock connecting rod. The headstock has a clamp that registers on the rod.

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A tension pin stop and a shaft guide are pushed into holes in the front of the headstock from the inside.

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The control rod is inserted into its hole in the headstock, then connected to the latch and the latch is placed onto the shaft guide.

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The screw, washer and lock nut loosely secure the latch.

The rounded end of a spring is inserted into the control rod hole in the latch.

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This pix is wrong, see below.

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[ATTACH]20441[/ATTACH]The other end of the spring sits in a small 'well'. Looks weird, but works quite well.

Pesky detail, but, the spring is not inserted properly in the last two pix. See below.

And the tinnerman nuts get us prepared for mating to the motor pan etc.

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The operation of the clamp will be come clearer when the carriage is done.

"below"

The spring goes to the hole above the linkage, not below as shown(wrong) above. In the two pix below the spring is on the opposite side of the linkage(sorry the pix are reversed, but hopefully you can see the difference).

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In spite of my previous comment re its working well, this makes it better!

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Wear problems caused some changes to the assembly of the parts below. A separate thread addresses those changes. That thread is the same as the one mentioned above. I will provide a link to it here also.


http://www.shopsmith.net/forums/showthr ... post159029



The sheaves and key slide together with nothing securing them. The key is like the Mark 5/V with a 'hook' end that nests into a shallow bore in the idler shaft.

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The assembly is slipped through the poly-v belt and into the eccentric bore.

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I taped the sheaves to prevent the control sheave from sliding off.

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The stop screw and washer prevent the eccentric from sliding out the bore as well as positioning it flush with the casting.

The eccentric is then secured with the screw, lock washer and nut.

The eccentric is rotated to provide proper poly-v belt tension(about 1/4" deflection when pressed from the side.

The screw is tightened to just fully compress the split lockwasher.

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As I mentioned above, the speed control knob has become way too stiff(difficult to turn).

So I revisited it and gained a better understanding of some 'details'.

The slow/fast extremes are limited by some simple 'details'. The cam cannot push the control sheave any further than its very end will push it, but the sheave will bottom out against the idler sheave before that occurs(even though the idler sheave can also move on the shaft). The cam follower is limited in the other direction(fast) by its interfering with the control shaft.

The control knob has another 'set' of details. The indications around the dial are fixed relative to that 'stop' pin on the back side that rides in a groove. That groove has a 'slow' end that limits dial movement. The detent notches are also fixed relative to them. So slow speed adjustment consists of merely positioning the dial to the slow end of the groove, and rotating the base to align the pointer with '700'. The detents will more or less self position. After securing the base, the high speed stop can be 'adjusted. I believe it only serves as a way to make the stop coincide with the last detented position.

Also the cam follower has details that I missed earlier. The major non-symmetrical feature is a sloped shape that I missed earlier.

The edge is narrower on one side -

cam follower 1.jpg (402.13 KiB) Viewed 4407 times

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than the opposite side.

cam follower 2.jpg (391.11 KiB) Viewed 4406 times

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It needs to be positioned to the cam so that the slope helps the cam move the follower. EDIT: The skinny side provides provides the same clearance as the fat side since the cam diameter varies as it passes through the follower.

cam follower 3.jpg (403.68 KiB) Viewed 4404 times

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This is needed most when the cam is pushing against the follower.

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Finally the spring washer works best where I found it(between the knob and the base).

EDIT: Notice the skinny side faces the larger diameter direction of the cam.

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I was not satisfied with either the feel(not smooth but grating) nor the locking function. The front wedge was totally ineffective, and the tension needed to be maxed out for the rear wedge to clamp.

Two things were apparent. The 'spacer' and front wedge did not slide in the bore, but were jamming. There were some small burrs caused by dings and wear. The bore had a protrusion that I believe was caused by the screw that fastens the worm gear bracket bottoming out in the threaded hole. After gentle filing of those parts, they moved in the bore with no restrictions.

Even after cleaning that up, the original problems remained. I finally came to the conclusion that the grating was caused by the extreme tensioning. So after much examining, and much head scratching, I concluded that the spacer between the front wedge and the handle 'cam' was worn to the point of being too short. I slipped a retaining ring on the shaft between the spacer and the front wedge. This acted as a shim to effectively lengthen the spacer.

All is now 'better', but the 'shim' dimension is critical. Too thin and it is ineffective. Too thick and the front wedge will not release from the front way tube completely. I will try different amounts to achieve a reasonsable 'compromise'.

I did not take any pix of this 'activity'.


The shim was located between the spacer and wedge in the bottom right in this pix.
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