Hi Everybody. I hope someone can help me out to finish this project that I already started. I am building a jig to adjust the brake shoes on some cars I have. Reading other posts I came across a jig made out of wood and a metal threaded rod that gave me an idea of how to build mine. The original concept comes from the AMMCO 1750 tool. The concept on mine is pretty much the same as in the wooden one, I just changed the way to adjust the adjusting rods. This is the one I took the idea from: I made mine with some scrap stainless pieces that I found around the vessel where I am working at It seems that one of the guys that made one of those wooden calipers drilled the hole in the piece of wood that mounts on the axle using a 3/4 spade drill bit. My questions for you guys are: 1.- Is 3/4 of an inch a standard size for the threaded part of the axle? (RED ARROW IN THE NEXT PHOTO) 2.- I have a 1949 Desoto, a 1952 Plymouth chieftain, a 1949 Packard and a 1949 Chrysler that will need brake maintenance; Does those cars share the same shaft measures? 3.- Is the length of the threaded part on the axle from tip to the back shoulder (BLACK ARROW IN THE NEXT PHOTO) the same on all of them? What is the lenght of this threaded section of the shaft? 4.- Are dimensions in the front and rear axle the same? I am offshore at the moment and for obvious reasons I don't have the measures handy. I have a lathe machine onboard and I am trying to figure out a good snug fit between my axle hub piece and the axle shafts. If 3/4 of an inch is a standard size for those axles, then the hub I have is way to big to fit, but I have another pieces of stainless steel that I can cut to size. That hole in the middle is 24mm (3/4 of an inch is 19mm, they only use metric system onboard) so the hole would be too big for a 3/4 inch shaft. This other hub has a center hole diameter of 15mm, my plan is to cut this one to shaft size and boring a lateral hole to connect one of the rods. As you can see on this photo, the rear part of the piece would clear the shaft beyond the shoulder at the end of the threaded part of the axle I hope you guys can give me a hand with this.
Since threads can be buggered up sometimes, especially on old parts, I'd think you'd want to shoulder on the tapered part of the axle. And the chances that all those different vehicles have the same taper to their axles is really small. And cutting a taper inside a new hub is not an easy operation anyway. Do the hubs on your cars have separate drums? If so, just make an indicator that will bolt to your existing hub. Then spin it around without the drum to perfect your adjustment. If they don't have separate hub/drums, how about obtain a junk one from somebody and cut the old drum off. Then you can attach your indicator. As a non-machinist, these are just my armchair ideas.
@Sioux888 Another thought........drill three 1/4" holes radially in the hub and thread them for thumb screws or small bolts. Use a stock hex axle nut on each vehicle, attaching the fabricated hub to the nut with the radial bolts. You only need one full turn to check the shoes circumference.....even though the nut will thread inward on the axle, the movement will be small enough to be accommodated without hitting the backing plate. You will need to bore the center hole to fit the largest of the axle nuts. edit: you could use one of the radial threaded holes to attach the 'arm' which also would serve as one of the locking bolts........ Ray
Hi Alchemy. Thanks a lot for your advice man! My cars all have separate drums, I don;t really understand what you mean with an indicator. What I thought to do is to measure the inner part of my drum with a different caliper and then to use my jig to calculate half the distance of that obtained measure to calibrate my brake shoe, then I would slip a filler gauge to leave the shoes as per manufacturer specification.
Hey Brother! I thought about that idea too, then I thought " what if I machine the center stainless steel piece to fit the external diameter of a ball bearing (RED LINE ON THE PHOTO) that has 3/4 of an inch inner diameter? (WHITE LINE IN THE PHOTO) I reckon if other axels have different thickness, I can always remove the ball bearing and find another one with the same outer diameter but with an inner diameter that matches a different axle size, so I can use the jig for different models. The green line is just to show the lip that I would use to let the ball bearing sit on.
Do you really need a ball bearing. Could you not turn up a boss that has the same outside diameter and a inside diameter that would let it turn on the spindle. Then if another spindle is a different size make another boss to suit the inside diameter. That way you would not have to find suitable bearings which might be a struggle.
Hi Brading. I thought about it and I went for something simpler, I used brass this time, the piece is smaller, lighter and as you said, I can always make another one that fits a different size axle. It would be just very convenient if I could get the measurements I mentioned at the beggining of my post to fabricate the different size axle bosses while I am onboard before I get back home to not loose time and money visiting machine shops. The inside diameter of this piece is 3/4 of an inch. I made a flat cut on one side to thread the arm in there and make it sit flush, I think I will stick to this one.
Here is how I built mine. I used an old hub and made the angle iron bracket. The hole for the bolt is slotted and the cap screw through the top allows me to calculate how much I move the pin up or down. (one turn is .036 inch). I machined all contact surfaces parallel / square so the pin is parallel to the spindle. I also machined a register on the hub that allowed me to measure accurately the position of the pin. Thus I could measure the ID of the brake drum and adjust the pin to the correct place to give me like .015 clearance between the shoes and the drum. I used the rig to adjust the cam pin to get the shoes centered then adjust them to fit the drum. Worked great, put back together and did not have to adjust the shoes, stopped perfectly straight. I do not see how the one made from wood would be rigid enough to be accurate.
Wayne - O that jig looks great man!, I might steal your idea, just a shame I don't have any used hubs around here to work with, if I don't manage to make mine work, I might end up doing something similar than yours. Thanks for sharing bro.
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