Gallery, Projects and General > Project Logs
Clock wheel cutter
sbwhart:
Chris
Don't know what your doing wrong can you post a pic of the bits to give us a clue.
Stew
sorveltaja:
--- Quote from: craynerd on October 25, 2009, 07:30:59 AM --- :(
Stew, just spent a while in the shop making an arbour for this cutter as you suggested. The hole in the cutter is 5mm so I made the arbour and threaded it M5. As I predicted (because it has happened to me before) when I came to tighten up the bolt against the cutter and put some proper force against it, the bolt just started to spin and ruin my thread!
I`m using an M5 domer die but something is clearly not right with my thread. Any suggestions - as I described in my first post this also happened the other way around when I threaded my bore in the mandrel to hold the cutter blank when I tightened up the bolt it started to spin in the hole.
I`m using force but nothing excessive....
Anyone help?
--- End quote ---
Hmm.. what are the dimensions(diameters) you use, when making an M5 thread :scratch:? Be it tapping or an external thread?
raynerd:
Hi Guys, I`ll post a picture later, I`ve been at a family part all afternoon. I can thread the bolt on tight and then when I come to give it the extra "nip" it turns the bolt about half a turn and loses any sort of torque. I guess it must be stripping the thread? I`ve re-done it but I don`t dare give it that extra that it needs, it is really tight so I think I`m going to go with AndyF suggestion of an offset locating pin. Basically I have room to put in a short M4 stub off centre that will butt up against the cutter and give me added piece of mind that it isn`t going to slip.
Picture later.
Chris
raynerd:
Ok well, here it is at present. Sorry picture is rubbish, taken on my phone as I didn`t have the camera handy:
This new thread seems to have tightened up much better but I still don`t want to put on the extra little nip for fear of stripping it. As you can see on the photo, there is plenty of room to add a small pin at the bottom to stop it rotating. Now, I must confess, being new to this hobby I like to ensure everything is the best it can be for practice and if it isn`t, I start again but I did have a quite useful accident. I went to thread the ofset pin hole and I picked up one of my cheapo m4 taps, needless to say it snapped in the hole but with about 15mm depth and left a little stub about 4mm above the surface sticking out! Now I did consider grinding this flat and tapping the other side but to be honest, although it was a dreadful mistake, it is serving an excellent purpose so I` going to leave it. No picture but again I`ll take on tomorrow. I think this bolt has actually locked it up but at least I know it won`t spin with the stub in place.
So next job tomorrow is to try and harden it and then it should be ready for a trial wheel run. Certainly looks good and a bit of fine tuning of the method I should be able to make some pretty accurate cutters. I think I`ve learnt a lot from making this one.
Chris
andyf:
Chris, the end-on pic shows why holding it by a single nut is probably doomed to failure. The tool-tip will hit the work on the interrupted cut, and any tiny shift of the tool will be anti-clockwise. That will tend to loosen the nut, and the next contact will make things worse, so you will end up with the arbor rotating and the tool stationary :(.
Thinking about it, it might have been better to drill and tap the end of the mandrel and use a bolt to secure the tool. Your nut is probably only about 4 or 5 threads deep, and common or garden nuts are often a sloppy fit and made of something almost, but not entirely, quite unlike proper steel. A bolt 15mm into the mandrel would engage over about 18 threads. That might solve the stripped thread problem, though the tool and bolt would still be knocked anti-clockwise in the absence of something like a pin to support the tool.
Andy
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