Sun Oct 25, 2020 3:14 pm by mrjim2017
And another rainy day to screw up my weekend working outside on the truck. So got some inside brake work done.
[b]KB5 Rear Axle Felt Seal Replacement How-To[/b]
The 1948 KB5 box truck rear axle uses felt oil seals as opposed to the modern lip seal. My felt seals were worn on one side and looked to have been replaced on the other side. Trying to find a felt seal to replace mine proved to be futile. Hmmm, NAPA just didn't stock them. LOL
So my option was to make the seals myself. Never did this, but did a little researching and found some articles on cutting out circles in cloth and other paper materials for home crafting. Compared different circle cutters. So had an idea of what I needed to do. Here is what I did and you may have your own way as well.
The KB5 axle uses 2 different means of felt oil seal application. The inner seal goes behind the bearing and race and sets inside the drum. It is a sandwich deal with a large flat round steel washer on the outside of the felt seal which the axle passes through and the felt fits snuggly around the axle tube an inner lip of the rear drum.
Pic #1 - The outer felt actually sets into a groove/channel on the backside of the axle nut that holds the brake drum on the spindle and rests up against the axle flange to create the seal.
I measured the larger inner felt oil seal and is 4.50" OD x 3.25" ID x .40" thick. The smaller outer felt oil seal measures 3.12" OD x 2.62" ID x .40" thick. This may not be 100% accurate as I do not have any specs or old catalogs giving me dimensions.
I could not find any category F5 dense felt material used for oil seals that was .40" thick - 13/32. What I did find was the needed type F5 felt at Grainger in a 12" x 12" sheet. I purchased a sheet of 3/16" thick (6/32 - $10.66) and a sheet of 1/4" thick (8/32 - $13.49) that when combined together put me at 14/32nd, which was close enough and the felt will compress.
Next I purchased a circle cutter, NT Cutter C-1500P off Amazon for $27.07. Simple to use and pretty straight forward. The tool has a pin on the bottom that can be used to spot the cutter. I placed a dot on the felt and lined the pin on that dot so if I had to move the cutter, the dot would be my reference point to go back to. Just make sure you have enough edge for the outside cut and don't go off the felt - you want to do your inner cut first, then the outer cut.
When you make your cuts, you will use the radius dimension of the felts, not the actual inside & outside diameters. Since I had to divide my felt sizes in half to get the radius', I decided to convert inches to millimeters which is just a click of a button on my digital micrometer. I also wanted to go a little larger on the OD and a little smaller on the ID assuming that compression/wear may have changed the actual sizes. For the larger oil felt I went with an ID of 40mm (half of 3.25" is 1.625" or 41.2mm) and outside diameter of 58mm (half of 4.50" is 2.25" or 57.15mm). I could have just as easily used the inches and added a little to the OD and subtracted a little from the ID - its just how I did it.
Using my micrometer, I first make my inside diameter cut which was 40mm, and adjust my micrometer to 40mm and lock it down. Then I use it to measure the distance from the center pin on my circle cutter and the small cutting blade. The arm the blade is attached to slides in and out, so I got my distance of 40mm and then locked the cutter into place. The cutter blade can be adjusted for thickness of materials, so adjust the length of the blade slightly more than the thickness of the felt being cut.Then set it on your reference dot holding down the pin on the felt using thumb pressure on the cutter's hold down knob, and slowly work the cutter knife blade around in circles using only a little pressure and letting the blade cut through. Once cut, leave the cut center in place as you need this position the pin on the cutter. Then adjust the blade arm to the OD of the felt seal (58mm) using the micrometer, tighten it down, and place the alignment pin back on your dot and cut the felt. Once cut, then you can seperate the felt seal parts. If you did not cut all the way through, keep the felt center in place, and put your cutter back on and re-cut. I had to drop the blade a little a couple times to get all the way through.
You will want to make 2 felts to match the factory inner oil felt thickness. So cut one felt in 1/4" and another in the 3/16". I will lay them on top of each other and put a couple dabs of sealant on them just to keep them together when I install them.
You can test fit the felt seal on the axle to make sure it is snug and test fit it into the brake drum to make sure it is snug. I actually had to make a couple felts before getting it right - a learning curve. So if you have to adjust your cutting ID & OD numbers, do so.
I did the same thing for the smaller seal for the outer bearing nut and used the thicker 1/4" felt. Again, I went with millimeters, 33mm for the ID cut and 40mm for the OD cut. When I inserted the new felt seal into the spindle nut groove, it extended enough out that I can just use the 1/4" thick felt and not add the 3/16" felt with it. I will put a small layer of oil resistant silicone behind the felt when I am ready and then install the felt and let the axle flange set the felt depth were it needs to go.
Felts get oiled up before installation, they don't go in dry.
Picture #2 shows the felt material, NT Cutter, digital micrometer, the spindle nut with my new felt seal installed, original seal below it, and my new felt seal for the other drum. Next to that is the inner bearing seal and how it is a sandwich type set-up with the original felt in the middle, and an example of my new felt seal above it.
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