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| Machining order and method for this part? |
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| raynerd:
I really appreciate your reply and sparky, thanks for the drawings! I`m at work, so must admit I`ve only had time to skim read the answers but will digest this afternoon. Just to give a bit of background on what this piece is for for those that don`t know. This piece is clamped to the pendulum rod and every 30 seconds, a trigger is pulled and an "arm" falls down by gravity and a bearing fitted to the gravity arm, rolls down the end of the pallet (on that critical radius as Stew mentioned) and gives it a push (i.e the pendulum a push). At which point an electromagnet kicks in to knock the arm back into a set position ready for it to happen again. I still can`t get my head around how to cut the end radius in the lathe but I think I just need to sit down and consider it more. My initial idea was to put the piece sideways in the vice and just use a large end mill or boring bar correct 0.75dia to cut the radius at the end of the rod but I realised this wouldn`t keep it concentric with the centre of the bore in the main body. Thanks again for all the adivce. I`ll be back to reply tonight as to my progress...or lack of it! |
| BillTodd:
Nice job Sparky! :bow: |
| sparky961:
The idea for the last step is that you clamp it to a rod, same as you would to the pendulum and use that to chuck the assembly. You could to this on a lathe or maybe have a chuck or collet block on a rotary table. With the lathe, you'd need a tool ground with a 3/4" 3/8" radius ground on the end, but you'd only need about 45 degrees worth of the complete circle to get the job done. On a rotary table, which now that I'm thinking about it might actually be easier, you set it up as described above and use a fly cutter set to 1.5" 3/4" to cut that last bit. No problem with the drawings. It was a fun and engaging challenge! I find that when I model a part in CAD, I'm always thinking about the order of machining operations and that helps out a lot when go to make that part. -Sparky |
| philf:
Hi Chris, I was surprised that the drawing calls for the surface to be concentric to the pendulum rod so I've just had a look at mine and you can see a witness line down the centre of the impulse surface which confirms that the drawing is correct. It would be relatively easy to do on a vertical mill with a dividing head (or rotary table mounted vertically). Personally, I'd use my boring head set to the correct radius and centre height. If you get stuck or would like to get any measurements off mine you can pop round any time. I can't quite decide how you adjust the height of the gathering pallet on the LBP INC design (unless you do it by bending the pallet support wire). It's certainly different to the original. The original is a pain because the adjustment is around the back of the block so you can't see what you're doing. I believe that the original pallet was a jewel. Mine is made from pot hard silver steel and has been running for perhaps 10 years without any sign of wear. Cheers. Phil. |
| raynerd:
Hello one and all. Unfortunately I`ve been laid up in bed all weekend with man flu. I made an effort to get in the workshop last night but felt rubbish after 10 minutes and gave up! Thanks for the offer Phil. I can actually get a jewel from Cousins website for £10 but I agree, people with less machining experience have had their synchronomes working using a bent paper clip with no problems! I might just go for silver steel! One thing that a few of you have refered to, is the radius on the edge (which is labeled - "Leave edge sharp" on the plans) Apparently this small radius concentric with the centre bore for the rod is important as it reduces wobble of the pendulum due to misalignment on impact with the gravity arm. So the method I had in my head of maching the piece as described by sparky and then I was going to mount on an arbor as Stew said, turn it on its side and use a mill or boring head to cut the curve. But this will generate a flat top and slope to the impact radius. I still can`t get my head around how this could be done on the lathe but in a wierd way can see how it will generate the radius needed!! I guess I`d mount it in an arbor and then would I just put it in a 3 jaw centred and use a 3/4" radius profile tool to cut the end radius (which would naturally generate the radius at the top concentric with the centre rod) Perhaps this is a very basic question, but other than marking it out well and cutting to the whitness marks, I can`t see any better way of controlling feed with a profile tool. I still can`t see how you could generate this profile using a rotary table and mill, despite the messages that have been posted here! Hummm, this is a tricky bugger! |
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