Life was simple back when I believed steel was the definition of rigidity. Then Robin Renzetti brutally dispelled my overly simplified grasp of materials, and I had to get a grip on 'everything is made of rubber'. I started putting indicators on stuff just to see / verify that cutting forces actually did that. They did. Now I try to think about where internal and external forces are going to make my tools and workpiece move. There's a lot less "I don't understand why that didn't work".
Love the explanations. The thin wall machining shows why 6 jaw chucks exist. Not that they make things perfect - there is still a gap between the jaws - but they are better than a 3 jaw. Obviously a collet would be better again - particularly an ER type (or similar) rather than a 5C, but of course NEVER for black stock.
6 jaw chucks are a bit of an odd one. I worked in a place where they turned thin wall tube and they helped with that, but with anything more substantial, you can't guarantee all the 6 jaws will be in contact (bit like the 4 jaw scroll chuck from a few months back)
@@occasionalmachinist Absolutely, it always concerns me when I see people using 6 jaw chucks as their STANDARD chuck. Looks good but doesn't mean that it is the right thing to be using. For those that may want to know why.... or TLDR 😀 Its kind of like weight ratings for casters (solid wheels), to use an example that may explain another "oddity". The caster may have a rating of 100kg but 4 of them will have a rating of 300kg, because you can only guarantee that 3 will be contacting the ground. (like a 4 legged stool). If you keep adding more casters the rating shouldn't change because you still can't guarantee more wheels will be carrying the weight, as the wheels (and the ground) don't deform. To get a higher rating total than 3X for a given wheel rating you would need to change to a flexible wheel (e.g. pneumatic) or suspension of some sort so that ground contact can be assumed. Back to chucks - 3 is the best as they must all be in contact - as you have said 4 or more do not GUARANTEE that there are more in contact. However with a THIN walled workpiece, or at least as it gets machined, the workpiece deforms (as you showed). The method of holding determines how much and where it deforms. The extra jaws limit how far it can deform. If the outer surface is already "machined" in some way (ground, bright etc) then all six jaws will be in even contact (or very close) and the deformation will be very limited. An ER collet will be better as there is so little distance between its 6 "jaws" 3 front and back over its 1mm clamping range). A 5C collet has small gaps to its 3 "jaws" - but it only has the front jaws, but due to its limited range (~0.1mm) works. Somewhere in-between I would guess is the Pratt Burnerd collets (3mm range) but narrow jaws. My lathe came with 5C and PB collets - I will be adding ER40 to match the milling machine..... then it will be choices/choices..... 🙄
I did - it's the video entitled "Look what the metric system made me do", but I got a couple of comments suggesting making a whole new part was not the easiest way of doing things. This is an explanation of the issues that those ideas may have problems attached to them.
@@occasionalmachinist Ok I get it now, I think. I don't know why your friend wanted to change to a metric in the first place. If it isn't broke, why fix it? As far as everything you said in this video, I agree.
@@opieshomeshop It was originally 20mm but a previous "fix" converted it to ¾" and the bores in the band wheel modified to suit an imperial bearing. That ended up as a failure so this was taking it back to the original specification.
Nicely explained. The thing has a hole through it to allow the adjuster so the bushing idea was a nonstarter.
Very well explained Mr. Thanks for your informative films. Cheers from Sweden.
No problems - the stuff in there is the sort of thing that is learnt by experience and rarely spoken of.
Life was simple back when I believed steel was the definition of rigidity. Then Robin Renzetti brutally dispelled my overly simplified grasp of materials, and I had to get a grip on 'everything is made of rubber'.
I started putting indicators on stuff just to see / verify that cutting forces actually did that. They did. Now I try to think about where internal and external forces are going to make my tools and workpiece move. There's a lot less "I don't understand why that didn't work".
I have a similar view - everything is a spring. It helps a lot when thinking about how things might move, or how they will behave.
yes it was enlightening,, and very useful!!!!
Very interesting. Nice work sir
Thanks.
Love the explanations. The thin wall machining shows why 6 jaw chucks exist. Not that they make things perfect - there is still a gap between the jaws - but they are better than a 3 jaw. Obviously a collet would be better again - particularly an ER type (or similar) rather than a 5C, but of course NEVER for black stock.
6 jaw chucks are a bit of an odd one. I worked in a place where they turned thin wall tube and they helped with that, but with anything more substantial, you can't guarantee all the 6 jaws will be in contact (bit like the 4 jaw scroll chuck from a few months back)
@@occasionalmachinist Absolutely, it always concerns me when I see people using 6 jaw chucks as their STANDARD chuck. Looks good but doesn't mean that it is the right thing to be using.
For those that may want to know why.... or TLDR 😀
Its kind of like weight ratings for casters (solid wheels), to use an example that may explain another "oddity".
The caster may have a rating of 100kg but 4 of them will have a rating of 300kg, because you can only guarantee that 3 will be contacting the ground. (like a 4 legged stool).
If you keep adding more casters the rating shouldn't change because you still can't guarantee more wheels will be carrying the weight, as the wheels (and the ground) don't deform.
To get a higher rating total than 3X for a given wheel rating you would need to change to a flexible wheel (e.g. pneumatic) or suspension of some sort so that ground contact can be assumed.
Back to chucks - 3 is the best as they must all be in contact - as you have said 4 or more do not GUARANTEE that there are more in contact. However with a THIN walled workpiece, or at least as it gets machined, the workpiece deforms (as you showed). The method of holding determines how much and where it deforms.
The extra jaws limit how far it can deform. If the outer surface is already "machined" in some way (ground, bright etc) then all six jaws will be in even contact (or very close) and the deformation will be very limited.
An ER collet will be better as there is so little distance between its 6 "jaws" 3 front and back over its 1mm clamping range).
A 5C collet has small gaps to its 3 "jaws" - but it only has the front jaws, but due to its limited range (~0.1mm) works.
Somewhere in-between I would guess is the Pratt Burnerd collets (3mm range) but narrow jaws. My lathe came with 5C and PB collets - I will be adding ER40 to match the milling machine..... then it will be choices/choices..... 🙄
*_I must have missed a past video. Why not just make a whole new part?_*
I did - it's the video entitled "Look what the metric system made me do", but I got a couple of comments suggesting making a whole new part was not the easiest way of doing things. This is an explanation of the issues that those ideas may have problems attached to them.
@@occasionalmachinist Ok I get it now, I think. I don't know why your friend wanted to change to a metric in the first place. If it isn't broke, why fix it?
As far as everything you said in this video, I agree.
@@opieshomeshop It was originally 20mm but a previous "fix" converted it to ¾" and the bores in the band wheel modified to suit an imperial bearing. That ended up as a failure so this was taking it back to the original specification.
@@ericparsonage7938 I see. Thanks for clearing that up. 👣👣👣👣👣👣👣👣👣👣👣