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Need help with bolt and nut
steve_shubin
Member Posts: 1,096 ✭✭✭✭
Need some help. Not with regards to Onshape, but about basic nut and bolt design
Hoping someone could point me to a website regarding the basics of nut and bolt design, or to a supplier of high precision bolts and nuts.
For one thing, I am curious to know about the precision of the fit between a nut and bolt.
In my case, I’m looking for something with less slop than one of the typical 1/2” or 5/8” bolts and nuts that I have in stock in my basement
For instance, when I am holding one of the 1/2” bolts, I am able to wiggle the nut quite a bit along the length of the bolt and laterally also. Not good for what I want to do. I have a particular need for a tight fit without the slop.
In my case, I am NOT looking for something like a nyloc nut or spring nut. But rather, just a fit between the hex nut and bolt where there is less slop.
Any help, advice, or guidance would be appreciated.
Comments
A nice brief introduction:
This is a great series of lectures:
Also check out the Design and Analysis of Bolted Joints (DABJ) lecture notes by instar engineering.
And the Unbrako Engineering Guide is also a great resource.
Oh and actually, it sounds like you might actually want a 'lead screw', if you are using the thread for axial positioning.
@Oliver_Couch
Thank you for the links. Fantastic resources —— very interesting videos
The NASA video with all the considerations that go into the selection of a nut and bolt is quite something. And I really liked the ultrasonic method of checking how hard a bolt/nut is clamping down. I'd like to get me one of those devices one day!!
Though I have interfaced with machine shops and had them fab up some of my hardware designs, realize I am not a metal worker, but rather come from WOOD construction as in residences and lighter commercial structures for the most part. As such, my fastener knowledge is certainly on the sparser side.
So I'll put a more fine point on what I am looking for ————
Now a bolt has a helix and an axis for that helix —- and a nut has the same
With the bolts and nuts I buy from Home Depot, there is enough slop in the fit of the nut to bolt to where I am able to move the axis of the nut quite a bit, off the axis for the bolt, when holding both within my hands. In other words, when held in hand, I can make it so that the two axes are quite a bit off line with each other.
So I need to interject that I will not be using these threaded objects in a typical or in the most widely used manner.
What I’m looking for is a nut and bolt combination where there is hardly any off axis movement between the nut and bolt, when held in hand. Where the two axes stay in line with each other when not under tension. A very tight fitting nut to bolt, before the nut is torqued down.
What would be the name or description of such a tight fitting nut and bolt? Is there a particular spec. number that I am looking for?
Again, thanks for any help.
I missed this when typing my second post. Thank you. This is sounding like what I am looking for. I am going to check this out right now
Thanks again. !!!
If you are worried mostly about axial slop you should investigate "ball screws" and "ball nuts". Those generally have a much better fit than V-threaded fasteners/screws. They are also available in a range of fits/precisions and are a lot more expensive than the usual Home Depot screws and nuts. The axial slop is often referred to as "backlash" or "lost motion".
Here are some fairly inexpensive examples (more exacting components can run into the thousands):
https://www.mcmaster.com/products/ball-screws/
Hobbyist machinists will sometimes spring spring-loaded "antibacklash nuts" that are looser than ballnuts but much less costly, like these:
https://www.amazon.com/BIGTREETECH-Direct-Merge-Link-Screw/dp/B088THFKZ4
For radial slop you want to manufacture the screw and nuts threads for specific fits that bring the male and female threads closer together in pitch diameter. Search on "screw thread fit" to find a lot more info like this:
https://www.fastenal.com/content/feds/pdf/Article%20-%20Screw%20Threads%20Design.pdf
The Machinists Handbook has dozens of pages on thread forms with detailed tables of specs and lots of other examples, much of which is unchanged over the past 25 years or more. If this is an ongoing interest, you can sometimes find older copies on Ebay for $20 or so.
Very helpful information that you have posted.
Thank You.
I've just started looking at the McMaster Carr ball screws and nuts.
Thanks for helping me with the correct terminology.
Pointing me to screw thread fit is definitely going to help.
The Machinists Handbook looks like this is going to be a great resource
Thanks again.
By the way.
Both Olivers and Michaels posts above are answers to my post.
I would click an ANSWERED button if I could find one.
But maybe because I posted under GENERAL instead of as a question, is why I do not see any ANSWERED button to click on.
Anyway, here is my ANSWERED indicator