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New Set of 10EE Knobs (The Devil's in the Details)

peterh5322

Diamond
Joined
Dec 15, 2002
Location
Monterey Bay, California
Forum member DaveE907 contributes this excellent narrative and photos album detailing the making of replacement knobs for his 10EE.

The text and photos are Dave's. The photo album is necessarily split across multiple posts.


After assessing the poor condition of the original zinc alloy knobs on my 1952 Square Dial 10EE I decided to make a new set of thirteen. There are lots of ways to make them, this is how I made my set.

I chose stainless steel to avoid and to ease machining used 303. In order to reduce cost and utilize material I had on hand they were made as two piece assemblies, a knob and a shank joined with high strength Loctite retaining compound. That way a 12 in. length of 2.0 round 303 bar on hand would be sufficient to make the entire set when coupled with about 18 in. of 1.25 round 303 bar.

Among the thirteen knobs are seven distinct variations. The first step was to measure them all and design their replacements. Of the thirteen, seven are identical and the remaining six are all individual designs in some respect. The only common dimensional features are knob OD, face profile and knurling pattern. All other characteristics vary. A chart of features was made and design sketches were made of the seven varieties.

My process was to make all the shanks to OD, length and finished bore (except for the .750 through bore for the upper left gearbox knob, it was rough bored undersize). The knob bodies were blind bored for .001-.002 clearance with their shanks (there are three different shank diameters) and turned the correct back angle taper for that particular knob. They were left at the 2.0 bar diameter and sawn off to the correct length for that knob leaving enough length for cleanup on the face.

Photo 1 shows some of them before bonding, and Photo 2 shows one shank and knob body bonded with the Loctite compound used to assemble them.

The face profile was designed as a 4.00 in. radius and they were produced by step turning.

Photo 3 shows the shop calculations made to produce the contour with .005 in. moves of the carriage. I like to make a chart with direct carriage positions and crossfeed dial numbers to make it fast and easy to machine the parts.

The chart I used is Photo 4.

Photo 5 shows the step turning operation, each knob face took about three minutes to turn. The knob 1.965 in. OD was then turned and the corners chamfered .020x45º.

Photo 6 shows most of the knobs after the faces and OD were turned.

The knob face profiles were worked on a 1x42 in. belt sander while being spun at 3600 rpm on an arbor in an electric hand drill. Just enough was removed to bring the surface to where the steps just disappear with a 180 grit belt. Both the backed up and flexible portions of the belt are useful and very good results were achieved. Surface finish was then refined on 220 grit and 320 grit belts, 320 was the finest grit I had on hand.

Photo 7 shows six knobs after working them on the belt sander. Each one took about 3 minutes to reach this stage.

Photo 8 shows twelve of them after the belt sanding process and ready for final polishing.

Now the knob with the .750 dia. through bore was drilled through the knob face and the bore was finished to size.

They were polished while being spun with the same hand drill at 3600 rpm. The shank OD, back taper and face were polished, the OD was not. 320, 400 and 600 grit with honing oil followed by Flitz polish made quick work of them.

Next they were knurled by cutting 160 90º notches .020 in. deep in the OD of the knob with a .375 dia. four flute end mill.

Photo 9 shows the shop calculations made to position the cutter to properly cut the notches. 160 notches was chosen as a close approximation to the original knurl pitch and also to be easy and fast to do with a 40:1 dividing head. Each move is one quarter turn.

Photo 10 shows the setup with a HSS end mill on the first part, I switched to carbide to speed things up on the rest of the knobs. Each knob took 9-10 minutes so each notch was cut in under 4 seconds. It was good exercise!

Photo 11 shows twelve of the completed knobs (except for engraving on those that require it) ready to be fit to their mating parts.

Photo 12 shows some of the old ones compared with their replacements.

They're a great improvement and feel good in the hand.
 

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  • 2. Bonding knob and shank.jpg
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  • 3. Knob face profile calculations.jpg
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  • 4. Step turning chart.jpg
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  • 5. Step turning face profile.jpg
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A continuation of the above.
 

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  • 7. Half through belt sanding.jpg
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  • 8. Ready for polishing.jpg
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  • 10. Milling knob knurling.jpg
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Engraving completed

Two knobs have letters on their shanks: the upper left hand and lower right hand gearbox selector knobs. To make it easier for the engraver to set up these parts the shanks were engraved before joining them to the knobs. They recently came back from the engraver who did a fine job on them. He was provided the original knobs so he could position the letters properly.

The photo isn't great but shows the finished engraving with the A-B shank joined to its knob and the C-D-E shank ready to be installed in its knob.

So far all but the three lower gearbox knobs have been installed to their mating shafts. Soon the gearbox will be on the bench which will make that task easier to accomplish.
 

Attachments

  • Monarch 10 EE engraved knobs 001 (Small).jpg
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Actually the speed control knob has engraving of sorts as well (at least on my machine (67))- it has an arrow in the same general area as the lettering indicating faster is this way.
 
This 1952 machine did have an arrow on the speed control knob directed toward the end of the shank and parallel to the axis of the knob. As it had no directional meaning I deemed it useless and deleted it. I'll start a separate thread on why and what I'm doing about the speed control.

Gashing knurling that way may seem wasteful or goofy but sometimes there are reasons to do it. Here the flawless results everytime with no setup fiddling or secondary machining operations coupled with limited number of parts and zero tool cost (everthing was on hand) trumped both rolled and roll cut straight knurls. It's also much faster to do than most would imagine.

Not applicable for these knobs but the technique also offers some aesthetic design opportunities if one chooses to utilize them.

Thank you for the kind comment.

The engraving was done by machine and at a very modest price. I tried doing some samples by hand but it's been too long since I've done any engraving in earnest and my results showed it. So far it's the only work farmed out on this machine.
 
Off with their heads!

Last month I made the lever ball ends for the square dial gearbox, the final parts of a full set of new knobs and levers for the lathe. They were made of 303 stainless like the knobs. Since three of the four levers incorporate ramps working against hardened steel ball end plungers as well as alignment slots guided by hardened dogpoint setscrews 303 would be a poor material choice for that portion of the lever. The original levers were heat treated steel, didn't measure their hardness but it was up there. Decided to utilize the original portion of the old levers for the ramp detail and make the exposed portion new. Best of old and new...

The photos show their construction, the parts were joined with high strength Loctite. Only the new portion of the levers are visible upon assembly.
 

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Dave:

I have polished stainless ball shapes to an "orange peel" free mirror finish and do not relish doing it again. It is work!
You have my respect and admiration for putting so much effort into a well deserving machine.

Best regards,

Amigo
 
Fitting the two right lower gearbox knobs

I discovered while fitting the two right lower gearbox knobs (gear selector below the square thd/feed plate and the B-C-D knob) that it was easier to fixture them on the shafts for taper pin fitting with only the shank of the knob present. The gearbox was off the lathe and partially apart but I didn't remove those two shafts.

End clearance was established with a .003 U shaped shim clamped under the shank. The shank and shaft were clocked as required, the shaft and shank were axially clamped together to lock them in place and then pin fitting was done.

Since the shanks and knob faces were assembled with Loctite it was a simple matter of heating to take them apart. If I was doing the whole job again it would be better to wait for final assembly of the shanks and knob faces until after taper pin fitting was done. However all but these two were fitted as assembled knobs.
 
It's been awhile since there has been time to work on this project. The photo shows the gearbox levers assembled and ready to go back on the gearbox.
 

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  • Gearbox levers.jpg
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Found this on the door of my office. I have had the same office now for almost ten years and just now noticed. I would not be surprised if it goes straight onto the 10EE.

IMG_0998.jpg

Sort of a shortcut I guess, but it might work.

Jerry
 








 
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