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wow 34 views and not one comment . did i forget to shower this month lol.
first build hi all . ive been scanning many threads for a while , and now well into my first build.a 36 x 60 gantry style cnc for cutting defron and balsa .yep im a crazie rc er with to much time on my hands.so far things are coming along pretty well . but now its time for my 1/2 '' acme rods to go in. what im not sure about is how to best make the ends work for me , with no slack or backlash, and is there a reason why you cant use acme bolts welded to a washer to move the components, instead of delrin nuts .i would also like to use 2 acme rods under the table to move the gantry about 18'' apart to eliminate twist.is this a good idea and were can i get this pullies , belt , and tensioner from.a man ,im righting a book here better stop for now.
wow 34 views and not one comment . did i forget to shower this month lol.
I'm no expert, but why not use a delrin nut?
Its not hard to tap, it's quite slippery, and not too expensive. Heck, I even made a tap out of a piece of rod by tapering it with files on a drill press and cutting flutes down the length with a hacksaw and files. I don't reccomend this (takes alot of effort to tap the hole with this) but it does work. If I had to do it over again, tho, I'd spend the 70 bucks for a factory-made tap.
What I did is tap a 1/2-10 acme hole through a delrin block. Then I drilled a smaller hole through the block parallel to the tapped hole.
Then I used a bandsaw to cut through both, though not completely through the entire block.
I use the smaller hole to run a bolt through the two halves of the block and tighten the "mouth" with a nut. This causes slight binding of the nut against the leadscrew, taking up any backlash in it.
Hope this helps.
thx for your reply andy. i think im going to go and buy the nuts so theres no future problems with this point of my build.my only other problem is should i go with 2 stepper motors to drive my gantry , or a pully system to drive both srcews, what do you think.
Here's a way to take most of the misery out of the process, if you want or need to make your own tap: Use a dremel tool to cut the flutes.Originally Posted by OneAndy
I use the cutoff wheel and cut lengthwise along the screw to make the flutes. You'd be surprised how fast the it goes. Another nice advantage is that the dremel can make deep flutes without rounding off the cutting edge of the flute as you might if you slipped with the file.
Here are a couple of photos from what a friend did.
You can see the hole that was tapped.
hi oneandy i was just wondering what a delrin was made up of, is it a plastic of some sort that is not brittle. i have some plastic that i got it from a indoor skating rink that they threw out , its quite hard and is very slippery, i made my end bearing blocks from it and it worked really well. i have 1/2 '' acme rod and would like to try it out , to see how it works . now that i know how to make a tap , what size drill bit do i need to use before i tap this stuff out.not sure how to attach a pic yet so ill just put it the photo gallery.thx cheers.
The real problem with making a tap yourself is that, unless you have access to a mill/lathe, you can't machine down one section of the threads to be shallower than the others.
I think on most taps, the leading edge threads are a bit taller. Otherwise, what you get is the threads all the way around just dragging on the material. I had to start mine by hand, but then I found the easiest way was to chuck the tap up in the drill press and run it at low speed until the motor stalled.
Then I clamped the tap in a bench vise between wood blocks and backed the tap out of the hole with a pair of vise grips. Rinse, repeat.
I was using gun lube as I didn't have any cutting oil handy. Seemed to work better than nothing.
I think delrin is the dupont brand name for acetal. I believe for 1/2-10 acme, you're supposed to drill the hole .405 or .410. Go with .410, you should be fine.
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