Best way to machine steel dowels

[HWooldridge]

I'm not sure this hub was engineered for failure. In other words, many assemblies intended to give way under load have some type of singular shear apparatus that breaks across the axis of the pin - not in linear fashion. I might be more convinced if only a small portion of the pin is presented to the gear housing but I can't tell that from the pic. That is to say, maybe 20-30% of the pin diameter profile and not straight through the middle because shearing 12 pins lengthwise along the .250 diameter would take a lot of grunt! If the combined volumetric area of the pins (.250x12x1-1/16 = 3.1875) is greater than the gear teeth and the two materials have the same yield strength - then the pins won't shear first.

In addition, a hardened dowel could well have a case that is 60 Rc with a very soft core. This is quite common for many types of machined parts and might apply in this instance.

None of this is really helpful to your problem but I thought it would be interesting...:-)

[pieter]

We would have to have someone who has grenaded one of these hubs to tell us what failed to know where the weak point is.

It all boils down to the use of the truck and what abuse it will see...
Then, design changes can be made wither with "soft" dowels, the hardened dowels or something else...

Pieter

[Kevin in Ohio]

I ground some off both ends of the new dowel before Rockwell check and it IS 60 all the way through. Thanks for all the input guys but I would like to hear from someone who has broken one. Kevin

[Doc Dave]

I'm not sure this hub was engineered for failure. In other words, many assemblies intended to give way under load have some type of singular shear apparatus that breaks across the axis of the pin - not in linear fashion. I might be more convinced if only a small portion of the pin is presented to the gear housing but I can't tell that from the pic. That is to say, maybe 20-30% of the pin diameter profile and not straight through the middle because shearing 12 pins lengthwise along the .250 diameter would take a lot of grunt! If the combined volumetric area of the pins (.250x12x1-1/16 = 3.1875) is greater than the gear teeth and the two materials have the same yield strength - then the pins won't shear first.

In addition, a hardened dowel could well have a case that is 60 Rc with a very soft core. This is quite common for many types of machined parts and might apply in this instance.

None of this is really helpful to your problem but I thought it would be interesting...:-)

The pin shows about 33% exposure to the outer clutch in the assembly.
Thanks for the input on this question.
Dave

[John S]

FYI I have a old warn hub from a Dodge PW ,but not a m13 hub .The style same though. The pins are hard . I can not file them with a regular file.

[Doc Dave]

I talked to Bob Harmon today, who is the "hub man" in Tenn.
I told him of the disparity in hardness that Kevin found when he meaured the original pins and the "new" pins.
Bob said that he is pretty sure that Warn engineered the pins to be soft, to be sort of a shear pin of sorts, so that the hub would break first without damaging the drive line in the axle and/or differential under extreme circumstances.

[Doc Dave]

The hardened dowels will have no give to them. A jarring load on the hub might break those dowels easier than the originals. I would recommend copying the originals. That way you are not liable for the engineering.

I think you, and someone on Joe's forum, have the most likely explanation. That is that the soft pins are designed to absorb the shocks within the hub, so that the other hard parts, like the outer clutch and axle shaft hub are not as quickly damaged.
The parts mentioned above look very good, only the pins show some wear.