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S&G 6730 vs S&G 6741 Tolerances

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Grain_ORice

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Post Sat Jun 27, 2020 10:02 pm

S&G 6730 vs S&G 6741 Tolerances

After looking through Sargent and Greenleaf's current catalog and the previous addition of their catalogue I noticed that the tolerances for the S&G 6741 and S&G 6730 were both +/- 1.25 in the current edition and +/-0.5 for the 6730 and +/-1.0 for the 6741 in the previous. I thought that maybe there was a change in machining and the two locks were made off of the same machinery thus the same tolerances. Regardless of what happened between the two catalogs I wanted to examine the two locks a little closer
20200627_091952.jpg

The 6741 on the left is a 2015 production run and the 6730 on the right is a 2019 production run.
20200627_092741.jpg

The 6741 Drive Cam had a diameter of 29.45mm, Contact Area of 8.96mm, and Contact Area depth of 4.24mm.
The 6730 Drive Cam had a diameter of 29.49mm, Contact Area of 10.94mm, and Contact Area Depth of 4.74mm.
20200627_093324.jpg

The 6741 Lever had a fence height of 2.47mm, Fence width of 2.78mm, Nose hight of 13.65mm, and a Lever length of 50.48mm.
The 6730 Lever had a fence height of 2.33mm, Fence width of 3.83mm, Nose height of 13.44mm, and a Lever length of 45.22mm.

We can also see the quality differences in the levers besides material. The fence on the 6741 is also rounded where as the 6730's fence is rhombic.
20200627_094204.jpg

The 6741 Wheel thickness is ~3.60mm, Wheel diameter is ~44.55mm, and Gate opening is 6.17mm.
The 6730 Wheel thickness is ~3.80mm, Wheel diameter is ~44.90mm, and Gate opening is 6.17mm.

The thickness difference is probably a cost reduction measure for the 6741, but note that the gate openings are the same on both wheel packs.
20200627_094254.jpg

The 6741 Fly width was ~3.78mm.
The 6730 Fly width was ~3.82mm.

There is less material on the 6741 fly's than on the 6730. This again is most likely a cost reduction measure.
20200627_094226.jpg

The 6741 Driver width was ~3.50mm.
The 6730 Driver width was ~3.52mm.

After going through this exercise we can see that the tolerances are tighter on the 6730 given the Fence, Driver, Fly, and Gate measurements verses the 6741. Statistically I should have at least 3 of each lock and preferably a larger sample size from the same production run, but given my lock budget this was the best that I can do at the moment. Having the two locks side by side like this did highlight some of the machining differences that I would have other wise not noticed, and that alone I found interesting. With the measurements done it was even more enlightening to see how the diffrances related to lock tolerances and manipulation. The nose on the 6741 does sit a little lower in the contact area than the nose on the 6730. I am able to manipulate the 6741 quicker than the 6730 that I have. However my manipulation times of the 6741 are still slower than the CDL-3 I have and the Chinese junk in the Sparrows Vault.

I hope this is of some interest to some out there.
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Riyame

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Post Sat Jun 27, 2020 10:04 pm

Re: S&G 6730 vs S&G 6741 Tolerances

Unless things changed I believe the 6741 is made in China at a much lower price point while the 6730 is still made in the USA.
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Grain_ORice

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Post Sat Jun 27, 2020 10:10 pm

Re: S&G 6730 vs S&G 6741 Tolerances

That would make since. I did not realize that S&G had anything over seas.
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Riyame

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Post Sat Jun 27, 2020 10:41 pm

Re: S&G 6730 vs S&G 6741 Tolerances

If you look on the silver label on the lock case it should say made in China, or somewhere over there.
PhoneMan: I always knew I'd say something stupid and it would be someone's sig
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MartinHewitt

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Post Sat Jun 27, 2020 10:48 pm

Re: S&G 6730 vs S&G 6741 Tolerances

R6730 from 1978:

Drive cam diameter: 29.40mm
Contact area: Don't know where to measure
Contact area depth: Don't know where to measure
Fence height: 2.325mm - 2.4mm
Fence width: 3.80mm - 3.90mm
Nose height: 13.325mm
Lever length: Don't know where to measure
Wheel thickness: outer ring 3.80mm, inner ring 4.55mm
Wheel diameter: 44.35mm
Gate opening: 6.90mm
Fly width: 4.05mm
Driver width: 3.10mm

After going through this exercise we can see that the tolerances are tighter on the 6730 given the Fence, Driver, Fly, and Gate measurements verses the 6741.

What do you mean here by tolerances?
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Grain_ORice

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Post Sat Jun 27, 2020 11:21 pm

Re: S&G 6730 vs S&G 6741 Tolerances

MartinHewitt wrote:R6730 from 1978:

Drive cam diameter: 29.40mm
Contact area: Don't know where to measure
Contact area depth: Don't know where to measure
Fence height: 2.325mm - 2.4mm
Fence width: 3.80mm - 3.90mm
Nose height: 13.325mm
Lever length: Don't know where to measure
Wheel thickness: outer ring 3.80mm, inner ring 4.55mm
Wheel diameter: 44.35mm
Gate opening: 6.90mm
Fly width: 4.05mm
Driver width: 3.10mm

After going through this exercise we can see that the tolerances are tighter on the 6730 given the Fence, Driver, Fly, and Gate measurements verses the 6741.

What do you mean here by tolerances?


I knew you were going to make sure I understood what I was trying to do.
The contact area depth was measured along the circumference line around the drive cam.
The contact area depth was measured from the circumference line straight down words the center of the drive cam.
Lever length was measured from the top of the lever to the edge of the screw hole closest to the top of the lever for connecting the lever to the bolt.

If I'm correct the tolerances of the lock (i.e. +/- 1.25 numbers on the dial) would be a result of the sum of machining variables like fence width, gate width, drive/ fly width.
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Grain_ORice

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Post Sat Jun 27, 2020 11:28 pm

Re: S&G 6730 vs S&G 6741 Tolerances

Riyame wrote:If you look on the silver label on the lock case it should say made in China, or somewhere over there.


Nothing about China. I did get the 6741 without the back plate so maybe it was there.
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L4R3L2

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Post Sun Jun 28, 2020 7:02 am

Re: S&G 6730 vs S&G 6741 Tolerances

The 6741 is made to be more economical, granted. But, I have never seen anything indicating they are made in China.

The chief differences are in the materials. The lever and drive cam are die-cast in the 6741, and the wheels are Zamac and aluminum, whereas the components of the 6730 are primarily machined brass. As for tolerances, I've always understood the main difference is in the width of the fence. I will say I'm surprised that S&G makes different flies for the 6730s and 6741s. It doesn't really seem all that cost effective to do so. Another cost cutting difference is the absence of the torque adjuster in the 6741.

What you have are single examples, which is not enough to do a significant comparison in some regards. Differences in thickness of wheels is insignificant. I'd bet the wheel posts are the right height for three of either type of wheel to be installed, with spacer washers. I've never seen any warnings about mixing parts, so I'm surprised about the significant difference in fly thicknesses. S&G used to publish a parts catalog, but I haven't seen a current one.

Thanks for posting.
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MartinHewitt

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Post Sun Jun 28, 2020 8:16 am

Re: S&G 6730 vs S&G 6741 Tolerances

Contact area: The long blue line is about 15.9mm. The same distance along the circumference is 16.7mm.
Contact area depth: With your definition measured on the photo it is 5.6mm.
Lever length: 45.3mm

Attached a blank image so you can take your own measurements. Resolution is 600dpi.

For the dialing tolerance the driver and fly are not relevant. They change only how the lock behaves when the dialing rotation is reversed.
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In case you wonder ... Martin Hewitt is a fictional detective in stories by Arthur Morrison:
Martin Hewitt, Investigator Chronicles of Martin Hewitt
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Grain_ORice

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Post Sun Jun 28, 2020 1:53 pm

Re: S&G 6730 vs S&G 6741 Tolerances

L4R3L2 wrote:The 6741 is made to be more economical, granted. But, I have never seen anything indicating they are made in China.

The chief differences are in the materials. The lever and drive cam are die-cast in the 6741, and the wheels are Zamac and aluminum, whereas the components of the 6730 are primarily machined brass. As for tolerances, I've always understood the main difference is in the width of the fence. I will say I'm surprised that S&G makes different flies for the 6730s and 6741s. It doesn't really seem all that cost effective to do so. Another cost cutting difference is the absence of the torque adjuster in the 6741.

What you have are single examples, which is not enough to do a significant comparison in some regards. Differences in thickness of wheels is insignificant. I'd bet the wheel posts are the right height for three of either type of wheel to be installed, with spacer washers. I've never seen any warnings about mixing parts, so I'm surprised about the significant difference in fly thicknesses. S&G used to publish a parts catalog, but I haven't seen a current one.

Thanks for posting.


I understand the material difference, but I was surprised at the difference in the wheel pack construction (thickness of the the wheels and flys). The torque adjuster was a given to reduce cost and the torque washer in the the 6741 has a pretty good bend in it compared to some other locks I have using a washer for the same purpose. I wish I had more to compare against, but it was interesting to look at them in this way.
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Grain_ORice

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Post Sun Jun 28, 2020 1:56 pm

Re: S&G 6730 vs S&G 6741 Tolerances

@MartinHewitt, I understand the purpose of the flys in revers rotation, but doesn't their width also add to how precise the operator has to dial in the number?
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MartinHewitt

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Post Sun Jun 28, 2020 2:57 pm

Re: S&G 6730 vs S&G 6741 Tolerances

No. In the opening direction of a number the fly is a hard stop. It might be sooner or later depending on the width of the pins and flies and the movement range of the flies, but with a key change lock this all doesn't matter. Actually if you want to consider the width of the pin and flies relevant, than you need also to determine the movement range of the flies. With optimally sized pins and flies the gap between right edge of the fly on the left positions and left edge of the fly on the right position is exactly the size of the pin.
In case you wonder ... Martin Hewitt is a fictional detective in stories by Arthur Morrison:
Martin Hewitt, Investigator Chronicles of Martin Hewitt
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kenneth_v

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Post Thu Nov 19, 2020 1:05 pm

Re: S&G 6730 vs S&G 6741 Tolerances

I replaced the cast white metal cam wheel in a 6741 with a brass one from a 6730. Not sure if it is in my head but it seems more challenging to manipulate.

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