Mark VII speed control breakdown

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The Mark VII speed control is almost identical to the Mark 5/v, except for the method in which the control sheave is moved. A single dial is rotated by hand. That in turn rotates a cam which bears against the control sheave. Two 'bullet' detents fall into notches in the back of the dial thus preventing drifting. The control sheave has a cam follower in place of the button/bearing.

The original cam was plastic and is one of the major design flaws. This machine had it's plastic cam replaced with what appears to be an aluminum casting.

First the logo needs to be removed from the face of the dial. Those three fingers really really hang on. That explains the outer edges of the logo being chipped off.

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The shaft is held captive by a retaining clip and a wave washer.

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That releases the cam and shaft, but removal is still not possible.

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The cam is secured to the shaft by a tension pin. I refrained from attempting the remove the pin at this time.

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The speed control base is attached to the headstock by the three screws in the 'slots'. At this point I am not sure why the base has such a large positioning range. The 'bullet' (spring loaded detents) can be seen near the top. Perhaps the base positioning range is related to the detents. An additional adjustable stop is located below the 'bullets'. As will be seen later, a stop pin on the back of the 'dial' rides in the inner groove and the adjustable plate provides the stop. I assume the combination of the base positioning and that plate correspond to a Mark 5/V high speed adjustment and dial calibration. Realize the cam and dial are indexed by the tension pin on one end, and the double flat on the other end of the shaft.

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Once the base is removed, the cam and shaft become free. That large 'snout' in the earlier pix is the rear of the base.

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The back of the dial has the detent notches and near the center the stop pin can be seen.

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I initially thought the dial need be removed to make the adjustments, but I think the 'high speed stop' screw is accessible with the dial set to highest speed, and the other three are accessible at the slowest setting as shown in the first pix.

This thread is linked to from https://forum.shopsmith.com/viewtopic.php?t=11373

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The original cam was plastic and is one of the major design flaws. This machine had it's plastic cam replaced with what appears to be an aluminum casting.


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There is a mark VII for sale on CL in the area. Can the cam be inspected without disassembly?

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There is a mark VII for sale on CL in the area. Can the cam be inspected without disassembly?

The M VII has an access hole like the M 5/V. The cam is quite visible from there.

The 'top' thread has a pix showing the 'view' in the second post.

A link to the 'top' thread is at the bottom of post #2 on this thread.



P.S. The cl pix looks like it is in great condition externally. The 'accessories' etc. will determine whether it is worth the asking price. I would not be in too much of a hurry - make an offer and wait if it is not accepted(at first).

Lot of nice SS stuff in Vegas!

[robinson46176]

My cam is good (so far) and I do have a spare good cam. Just to be safe though I may be unnecessarily lubing the cam follower bearing. I don't believe that fairly frequent oiling of that bearing by putting in a dribble of turbine oil through the oil hole and sitting the unit in the upright position (bearing down) overnight does any harm. I also run it maybe 15 seconds while it is upright.

I really like the look of that aluminum cam...

If the makers had quickly started supplying aluminum cams on new ones and as an "ask for one and we will send you one" part to Mark VII owners, they may not have gone under... That also applies to the way tube rack gear. Those were the only two actual failings of the Mark VII. I'm pretty fond of mine. Other than the rack gear it is in good condition and I think that they have a lot of things going for them.


.

[JPG]

My cam is good (so far) and I do have a spare good cam. Just to be safe though I may be unnecessarily lubing the cam follower bearing. I don't believe that fairly frequent oiling of that bearing by putting in a dribble of turbine oil through the oil hole and sitting the unit in the upright position (bearing down) overnight does any harm. I also run it maybe 15 seconds while it is upright.

I really like the look of that aluminum cam...

If the makers had quickly started supplying aluminum cams on new ones and as an "ask for one and we will send you one" part to Mark VII owners, they may not have gone under... That also applies to the way tube rack gear. Those were the only two actual failings of the Mark VII. I'm pretty fond of mine. Other than the rack gear it is in good condition and I think that they have a lot of things going for them.


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Since you brought the rack up, I have determined it is a 14.5 degree, 12 pitch gear rack A steel rack can be obtained, BUT it is 3/4" wide, too thick, and flat, not curved to 1 3/4" diameter. The headstock rack opening is only slightly greater than 5/8". 1/2"(flat backed) nylon racks are also available, but $$$$$:eek:.

I still have that cnc machined cam, but doubt I shall ever need it with the cast one.

[expressdlivery]

Does anyone know where I can get a Mark VII speed control cam or where I can get one reproduced in metal.

Thanks

[JPG]

Does anyone know where I can get a Mark VII speed control cam or where I can get one reproduced in metal.

Thanks

Forum member hdoilcan had a few made(I believe I was the only other member to participate up front). He offered them to others after he received them, but I do not know if anyone else got one. They be expensive, but are very excellent quality. PM him.

[jayp413]

You really hit the jackpot buying one with a metal replacement!

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You really hit the jackpot buying one with a metal replacement!

As well as other 'attributes'. This may have sold a few months earlier for 1/4 of what I paid for it. I still got a good price IMHO. Not flaw free, but functional.