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In this video I will be showing you how to make a nylon jack pad. The reason for making this is that I wanted something which wouldn’t damage the pinch weld on my car. The jack used a metal pad which isn’t great for lift the car on the pinch weld and there’s a high risk of deforming it.
At the end of the video, I’ll have a photo of the jack pad with all the dimensions for a reference.
Removing the old jack pad which is only held in with a cotter pin that clips into a dowel in the center. It’s nothing overly complicated, essentially I’ll be copying the original base, however, the nylon insert will have a slot where the pinch weld fits into place.
For this, I am starting with a piece of 3” diameter nylon. I’m not sure on the grade, I purchased this from a local metal supplier and this is what they had lying around. Delrin would also be an option, however, nylon is stronger with a tensile strength rating of about 10,000 or higher. Nylon is a form of plastic used in a variety of applications, including industrial and can be found on bushings, wear pads, wheels, seals, etc. Nylon has great wear resistance and is self-lubricating.
The total height of the nylon insert will need to be 1.5”, this includes the dowel, where the insert fits into the cup on the jack frame and above for the pinch weld height. This is fairly specific to the jack’s design and my car.
Unfortunately, I don’t have a parting bit that can go deep enough for the nylon so I’m forced to cut this by hand. While nylon is a softer material, it isn’t as easy to cut as I was expecting. Switching between a coarse tooth wood saw and a hack saw blade, there was no quick method. The wood saw gave a wider cut, however, the saw was binding. With the wider cut, I could go in with the hack saw and it has a thinner blade and made the cutting slightly easier.
Cleaning up the ends facing them on the lathe. Keep the lathe speed high first roughing in the surface manually ensuring it’s square, 0.020 cuts to start running at about 600rpm. Make sure your tool bit is sharp, here I am using HSS.
Nylon gets very stringy, especially when making heavy cuts. A chip breaker doesn’t work here so the only real way of breaking that strand is by stopping your feed. I don’t recommend breaking it by hand while the machine is on as you may hurt yourself.
As a final cut, I set up the power cross feed at a lower rate at about 0.002 and the last cut was 0.005 which achieves a smooth final finish. This can be one solid cut, the strand will be very hair-like, thin and breaks away easily so it shouldn’t create too much of an issue. I’m not using any cutting fluid either for any of this.
Putting the part back into the chuck, just to be safe I set up my dial indicator to check for runout and made adjustments as needed. With the jaws snugged up, using my mini dead blow hammer, the part is tapped into place so it’s running true.
Cutting the dowel, first roughing it in just like before. Due to nylons' lubricating qualities, even with the jaws tight, if you do take heavier cuts, it does tend to slip in the jaws so be mindful of it. The dowel will only be used to hold the pad into place on the jack, it won’t have a cotter pin installed like the metal pad. Turn down the nylon slightly to clean up the outside. The overall diameter isn’t overly critical, however, it will be larger than the recessed area it fits into.
Flipping the part around, now cutting the correct diameter so the pad fits into the cup of the jack.
There is a radius on the inside edges of the cup so there will need to be matched. The tool slight is rotated to the appropriate angle and this will be changed a couple of times so the radius is roughed in. After that those angles were shaped into a radius using a file. Finished up using 320 grit sandpaper.
For the slot, install the vertical milling attachment. The part will be mounting in this and an end mill will be used in the spindle. The squareness of the milling attachment was checked using a dial indicator and adjustments were made as needed. The part is then clamped into place and just to be safe I did verify it’s position with a dial indicator.
The vertical position of the part was to determine using a center drill in the chuck. This was just done by eye. Using a 3/8” end milling in the chuck, the slot was then cut. First, it was roughed in close to the appropriate depth. Again a 0.005 was cut for the final finish. Same 600 rpm as before with the 0.002 feed rate. With the milling bit, the edges did have some burs and this can be easily cleaned up using a razor blade.
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