Screw cutting an internal Acme thread.
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- Опубликовано: 17 сен 2024
- Struggling to find time to edit videos - this job was done in December '22 (hence the long sleeves & background noise from a space heater) & I can't remember exactly what it was for! The original brass block was completely worn out & the screw was pretty worn also so I tried to just make the new block(s) to suit the old screw.
The blocks were machined to size & drilled in the centre in a milling machine, before being held in a four jaw chuck on our Colchester Triumph 2000 lathe for threading using the Ainjest rapid screw cutting attachment.
This was an interesting job, I enjoy watching projects like this. Thanks
Thanks for watching!
Nice job buddy👍
Nice one 👍
When cutting trapezoidal threads I could never decide whether to grind the tool to perfect dimensions and keep cutting deeper till the thread fits or grind the tool narrower, go to spec depth and then lengthen the cut, decisions decisions 🤔
I did design a special jig to grind the perfect angles for trapezoidal tools that could be used either on my surface grinder or using a cup wheel on the mill, perfect results every time, hopefully😂😂😂😂
If all goes according to plans it will be on the SMEE stand at the Midlands show next month, along with a 60 degree threading tool version.
I just happened to have the tool used in this video & I think it probably worked out better than one ground to spec (whatever that might have been!) for cutting the thread to suit the worn out screw...
What is SMEE?
@@MidEngineering Society of model and experimental engineers, they are celebrating their 125th birthday this year and the Midlands model engineering exhibition are helping them celebrate next month.
@@MidEngineeringif you are interested I put up a video of my grinding jig on RUclips yesterday .
Nice job and thanks for the interesting videos.
Bearing in mind that it’s the male part of the leadscrew thread that’s worn away; surely the width of the thread grooves in the new nut need to get narrower (thus leaving wider lands to fit into the worn grooves of the screw) to accommodate that wear… perhaps that’s what led to the loose fit
Yes, grooves needed to be narrower than standard but the profile on the tool was too narrow, so it needed the extra passes to make the groove wide enough. Being impatient to get rid of the binding led to the loose fit!
Much more confident than me. Straight in. Did you reduce the audio on the squeal 😊?
The Ainjest helps a lot. Would have been a LOT slower if it had been a metric pitch. Auto sound level on the camera turned itself down when the squeal kicked in...🙂
I watched this twice to insure I wasn't missing something and I don't believe I did. Your fitting segment confirmed typical ( none linear ) thread wear along the length of the screw. Resulting in the same none linear fit along the screw's length. IE: Good fit here or there but sloppy elsewhere. In the end you removed a little more stock to compensate for the badly worn lead screw. Logic would seem to confirm that lead screw Nut and Lead Screw should be machined as a matched set. Yes, I realize that Lead Screws are hard as hell and will probably need annealing before machining but what other choice do you have? Maybe turn a new one? Works for me cause I'll get to see another enjoyable video. Thanks! 👍💌
Wakodahatchee Chris
Yes, ideally, the nut should be a nice fit all the way along the screw & the only way to achieve that would be to re-machine the screw. I'm not sure that anyone ever does that! You might as well make a complete new one with the correct thread spec. Or get a standard ready made screw & machine the ends to suit. Luckily in this case, I think the screw just has to move something rather than do accurate positioning...