Best way to machine steel dowels

[Doc Dave]

I am rebuilding some M13 hubs I found on the net. It took me close to three years but I was able to buy three working condition hubs, two to use and one back up.
The hubs are in fairly good conditinon, but in dissasembly I noticed that the internal drive pins (steel dowels), that look like loose roller bearings, have some deep scratches/ small gouges in them.
I would like to replace them in the reassembly.
Its a problem that Warn does not support obsolete products, period.
I was, through an intermediary, able to get a schematic but that is about as far as it got as to help from Warn.
I have been able to find steel dowels close to what I need. Mc Master has dowels that are .250 inch in diameter and 1 1/8 inch long. What I need are dowels the same diameter that are 1 1/16" long.
I have been told that the best way is to have a machine shop put them on a surface grinder to take off the 1/16 inch length. I realize that this will soften the steel slightly on the end.
Any comments from the group who are knowledgeable on this?
I tried various sources for pins the proper length and have not been successful...I tried some bearing sources as well as MSC, etc.

[OLD DODGE]

A dowel pin should be hardened all the way through. Taking 1/16 off one end or 1/32 off both ends should not affect the durability of the part. A machine shop should have a coolant system hooked up to their grinder to prevent overheating the part.

Have your machine shop examine your old parts. They should be able to tell the hardness of your originals. They could be soft, case hardened, or hardened all the way through. You could run into durability/breakage issues if your replacements aren't the same.

[Charles Talbert]

I really don't think what you need to do is an issue at all as far as the integrity of the part. Taking a very small amount of material per pass on a surface grinder doesn't generate a lot of heat. I would go ahead & purchase the pins as near the spec as I could, take them to a REPUTABLE machinist for grinding the ends to length. If this process is handled correctly, I see no problems.

[Jake]

Correct

Keep it cool as you grind it and use the right stone and you should end up with a perfect match to the original pins.
Heat will definitely change the temper in the steel so that is the thing to watch for.
Hope it works out for you.

[monkeymissile]

If I were doing this, I'd pop them into a collet-chucker lather and face off the extra .0625" with a carbide tool instead of grinding them. Much faster, less heat, easier set-up and after the finished length is achieved, you can easily chamfer the edge. Holding a 1/4" pin upright in a surface grinder is a pain and since you can only take a few thousands off at a time, it'll take forever and you'll have to use coolant so you don't take the temper out of the pin. Not sure, but I think dowel pins are fully heat treated and not just case hardened at that diameter. Larger ones may be case-hardened.
My $.02.......

[Kevin in Ohio]

Dave,
Just saw your post. If you haven't gotten it done yet I'll do it for you if you pay return postage. Suface grinding done CORRECTLY will NOT change rockwell. I grind hardened shape punches for a living and EVERYTHING we do is hardened when we start grinding on it. We take up to .400 a pass albeit slowly with mist coolant. Let me know the exact length you want and can easily hold +/- .0005 Or normal tolerence is .0002 total ;). Email me and I'll give you my address, Kevin

[Kevin in Ohio]

Monkeymissle,
Holding rounds on a surface grinder is very easy. Just use a V block or we have snap fixtures made to do it. To give you an idea we .get .009 of and hour to bring an overall length to +/- .001 from a part .025 oversize. In other words you have to do 110 parts in one hour. Hard is doing a punch with a .030 or less body, bringing in the .125 diameter head thickness. We have to wrap the head with clay to keep from spitting them off! we deburr with a scotchbrite wheel when were all done on a normal bench grinder. Kevin

[Doc Dave]

Kevin, check your email

[monkeymissile]

grinding

Monkeymissle,
Holding rounds on a surface grinder is very easy. Just use a V block or we have snap fixtures made to do it. To give you an idea we .get .009 of and hour to bring an overall length to +/- .001 from a part .025 oversize. In other words you have to do 110 parts in one hour. Hard is doing a punch with a .030 or less body, bringing in the .125 diameter head thickness. We have to wrap the head with clay to keep from spitting them off! we deburr with a scotchbrite wheel when were all done on a normal bench grinder. Kevin

Kevin,
That's the great thing about machine work, there's always several ways to achieve the same end result. I fondly remember one week I spent grinding a complicated profiling tool for one of our production turret lathes (this was well before CNC lathes). It was a total pain, but worked beautifully the first time. I got all the clearances just right!
I just loved how those grinders can kiss off .0001". I briefly worked at a custom electric motor shop that had this crazy grinder that could grind motor armatures to within .000001" concentricity!

[Doc Dave]

Thanks to all for your input, and
Merry Christmas

[Kevin in Ohio]

Need some help from those of you in the know on these Warn Hubs for the WM300 Power Wagons. Dave sent me the pins he wanted ground to size. When I checked the Rockwell the stock pins were dead soft. The replacements he sent tested 60 which is basically the same as A2 hardened tool steel.
My question is, is this a designed breaking point? There about 12 of them per hub and hate to have the wrong part break in a pinch. Pins are alot easier to replace the the machined gears. Thanks for any help, Kevin

[pieter]

I have not seen this hub, nor do I have a schematic, but if these dowels are used to give the hub it's strength/weakness, then with the hardened dowels that you have, it will not break at it's designed intent.

Since the originals are "soft", 12 "soft" dowels would have a specified shear capacity. All assuming that these dowels are what gives the hub it's bite. For example, one the Selectro external hubs, there is a toothed gear that gives the hub it's strength/weakness.

Having one in the hand or at least a schematic will help to determine if this is the "fusible link"...

Norm, Jimmie, where are you... your slipping. Help this guy out!!!
I know it is rainy & snowy out there in California, but us Midwestern guys are freezing!! :-))

[Kevin in Ohio]

That's basically what I was thinking/fearing. I was just wanting to know for sure where they are supposed to break. I'll post an exploded view from the April 1999 issue of the PWA. Thanks for the input, Kevin

[pieter]

As they say "a picture is worth a thousand words!"

The fusible link in the hub with this design is two-part.
The outer clutch would be one part and these dowels would be the other.
The dowels connect the outer clutch to the outer housing to the outside
and then to the axle shaft hub, or so it seems.

Upon breaking this type of hub, either these dowels would bend/shear or the outer clutch would grenade.

I'd say, replace with "soft" dowels. I know you are doing this for the other guy. Another option would be to not put all 12 dowels back in. It all depends on what this vehicle is being used for in the long run.

Pieter

[OLD DODGE]

The Tree That Doesn't Bend Will Break

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.