I'm building the Shopnotes 121 router lift. On one end, it has two lock nuts sandwiching a bottom plate. The lock nuts seem to be "sided" with a top (sort of rounded)and a bottom (flat). the flat sides are against the bottom plate. Two problems:
1) The "inside" nut (on top of the plate) doesn't want to catch the screw threads so it can go on, which makes sense, since that is upside down (starting it with the locking end first).
2) I can't hold the threaded rod tight enough to put the nut on correctly and screw it on as far it needs to go -- about 10 inches.
Any advice on how to attack this? I've already got one nut started (the one that will be on the bottom of the sandwich), but it's stuck now that the plastic has grabbed. As mentioned, I can't hold the rod still so I can continue to turn the nut. I don't want to damage the threads on the rod.
I'm tempted to put some heat on the stuck nut to melt the nylon and take it off, then switch to regular nuts and Locktite to hold them.
Put two normal nuts onto one end of the threaded rod. Tighten the nuts against each other so they lock together i.e. "jam-nuts". Hold the jam-nuts with a wrench while you thread the nylock nuts onto the rod.
Voila. :-) you can hold the rod without damaging the threads.
You probably have to thread both nylock nuts on in the correct direction - so one nut you may have to turn a thousand times. Alternately, you can try threading the nylock nut fully onto the rod in the correct direction, then remove the nut, turn it over, and see if you can get the nut to engage with the formed threads.
The correct answer Can't beat a nut and a jam nut for gripping a threaded shaft.
I've not seen the design in question, but I doubt a lock nut is the best solution, especially if it needs to be threaded over 10" of length! Nylocks are the best of a bad idea - avoid the swaged nuts like the plague unless your threaded rod is replaceable too! I prefer to use a locking pin, jam nut, or split lockwasher, in that order of secure locking - high to low. The sure thing is a cross hole and pin. For every day applications, a split washer is a better solution than a nylock.
Thanks guys. Since I had extras of the lock nuts, I used my propane torch and removed the one that was stuck. It spun off very easily once that plastic melted. Made me think maybe I could just heat the one that had to go down the whole length of the rod, but I think it might set the plywood base on fire by the time I got it that far.
I'm going to to stop on the way home and see if I can find some regular 3/4-16 nuts and split washers. Washers shouldn't be a problem, but all I've been seeing at Lowe's, Ace Hardware, etc., are 3/4-10 nuts. There's one other place to try in town. If I whiff there, I'll order them.
By the way. Can anyone just walk in to a Fastenal and buy a couple of nuts & bolts or is it strictly a wholesale/bulk order outfit?
I don' t understand the details of this construction but will Locktite and regular nuts solve the problem?
The fastening companies will gleefully sell to anyone that walks through the door because if you have not negotiated an account with them they charge a whole lot more.
Look at McMaster Carr before walking in to Fastenal. I use my retiree badge from Caterpillar at Fastenal and that reduces the price about 40%. I look at eBay for a lot of odd fasteners too. Got a tremendous deal on some 3/4" collars on there in a bag of 10. The price for 10 on eBay was less than the price of 2 at Fastenal. At the reduced price!
So I got regular nuts and split lock washers today. Put them on and if I tighten them all they way down, then the rod won't turn, which it needs to do to raise and lower the carriage that holds the router. So, I'm thinking that there's going to be a sweet spot where they're tight enough to hold the rod in the right spot, but still let it turn freely.
there is a carriage with a coupling nut that the rod will go through and when the rod is turned, it will raise & lower the carriage. Here's a picture of what's going on. Perhaps when the rod is threaded through the coupling nut, it will sort out some of these problems? Maybe putting some loctite on, as Bill suggested will help too. Here is a picture of what I'm trying to describe.
When I was in college I worked for AEM assembling their narrow belt sanders. I learned a lot about machine assembly
On one machine there was an adjustment like that. Two jam nuts on each side were used. Jam nuts are half the thickness of regular nuts. The washer side nut is adjusted and held with a thin open end wrench. Then toe other one is snugged up and tightened against the first. Rock solid. Same can be done with regular nuts if you have linearsnspave
Running a tap through the ‘upper’ nylock nut in the pic might allow you to thread it on ‘backwards’. Threading it on the long end then chucking the threaded rod in a drill is possible too. Not a great option because that would grind off so much of the nylon locking insert material. It might loosen later
Can’t ever go wrong using Locktite in critical assemblies
How will the coupling nut be attached to the carriage? It will need to be firmly attached or it won't move the carriage. Sometimes people use threaded inserts but they have to be good ones. One way I've done something similar is to make a thick steel plate and tap it to make a "nut" and drill holes for screws to fasten the plate to the carriage. Another way often done in commercial designs, for example on farm equipment, is to weld the nut onto a thinner plate or bracket. This is my first choice since I have metalworking and welding capability in my shop.
I find nylock nuts perfect for the lower plate you show. I assume you want to be able to adjust the nuts to remove excess play in the threaded rod. I think they would be easier to adjust than two nuts on each side, each with a lock washer jammed between them. They would also be much easier to adjust than two conventional nuts glued to the all-thread rod with loctite although you could loctite an upper nut and use a nylock under the plate. (Use the blue loctite or it will need a torch if it ever needs to be removed.) I assume there will be two washers like the one shown in the photo, one above and one below the plate. Lube and tweek the nylock nuts until you get smooth motion with no play.
Another way to do this is with just one nylock nut and washer on the bottom and a washer and a roll pin (spring pin) on the top. Drill a hole sized for the rool pint through the all-thread rod just high enough above the plate to leave room for the washer. Insert the rod from above, put the roll pin through the hole, put the washer under the roll pin, then put the rod through the lower plate and add the lower washer and the nylock nut. Adjust the nylock nut for smooth motion. I'd use a hardened, ground steel washer (never a cheap, plated stamped washer) Roll pins are hardened spring steel and will bear nicely against the washer. This is a common way to constrain one end of a rotating shaft, sometimes with two roll pins or a flange at the end if the clearances are not critical. Cotter pins are easier but not as smooth in operation or as robust in the long run.
BTW, an easy way I like to hold a threaded rod for turning rather than jam two nuts somewhere: grind or file a couple of flats through the threads and down a bit into the solid metal. This will let you put a wrench on the flats to hold it. Grinding away part of the threads doesn't prohibit threading nuts on the shaft. I don't have a good photo but with some imagination you might see the flats I ground on the left end of the 3/8" drawbar in this picture and in near the middle of the 1/4" drawbar:
Thanks again gents. I appreciate the suggestions. to answer a few of the questions:
The coupling nut, according to the instructions is epoxied into the hole after grinding down its points so you can get the hexagonal peg into the round hole. There is a busing in the bottom plate, but it's the same thickness as the plate, so there's really nothing for the washers to bear against.
As I was stewing on this before I got back here to check on replies, it occurred to me that I could put a lock nut back on the end and either use loctite and a regular nut on the top or use the two regular nuts to jam together above the plate. I don't think that extra height of two nuts will hurt.
Ok, their pic explains why they spec'd nylocks.... I would use a couple jam nuts to do that. A better way would be to find or make a close fit bronze bushing to go in the plywood - keeps the rod from wearing on it's hole, and if you leave it a little long with a couple flat washers for the nuts to bear against they won't wear on the plywood either.
Another thing you could do is loctite, super glue, or epoxy on the nuts. Loctite and super glue are generally reversible with some heat. Epoxy is too, but it stinks like it's something super toxic
You said "The coupling nut, according to the instructions is epoxied into the hole after grinding down its points so you can get the hexagonal peg into the round hole."
I always take a small hand chisel and make the hole a hexagon shape. The flats are tight to the wood and help hold it from turning along with the epoxy.
Appears the nyloc nuts are replacing shaft collars in a thrust situation as the router is lifted. Not sure why you tried nuts & split washers.
Run two standard nuts on the lower end of the thru hole and tighten them up against each other. A washer is needed between the two nuts and the wood to keep the nuts from chewing into the wood. On the other side, to the same thing in reverse, but as you tighten the second set of nuts, screw the first nut to the washer, then back off a half or full turn. Hold this nut with a wrench. Screw the first nut to the second nut and tighten it to the first without rotating the first nut. This should allow the threaded shaft to turn within the wood.
Don't imagine that you will be able to build something out of wood with no backlash in a threaded lead screw like you are making. Nearly impossible even in the machine trade.
Can't beat a nut and a jam nut for gripping a threaded shaft.
