prepman
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prepman
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Probably because of the amount of recycled steel in it?
Seadog
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pressbrake1
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Too low in carbon
pressbrake1
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Bearing deflection and wear will prevent a lathe from turning chucking work true
Worn chucks feel like they’re gripping well but the job is moving which will cause taper
And a worn bed on a elderly machine
Worn chucks feel like they’re gripping well but the job is moving which will cause taper
And a worn bed on a elderly machine
pressbrake1
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Alcohol is filth
Seadog
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Hush your mouth, Sir!
prepman
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Chuck was trued with grinder/jig prior to and is relatively new, bearings are good no deflection.
PS: chuck wasn't used it was in a morse holder with drawbar for final 3 tries.
prepman
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Straight from the horse's mouth.
prepman
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pressbrake1
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I mentioned chuck for future reference for others
prepman
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Unfortunately the thread gas meandered (as usual) away from what I wanted to discuss. Which was an attempt at using a laser to check for bed twist rather than using sensitive levels.
The fact that I'd produced a taper was a side issue. Although many helpful comments appreciated.
My theory being that once the beam had been centred from tailstock to head stock, at both ends of bed, traversing out and doing the same over the length of the bed would indicate a twist if any present, with a rise or fall of the point of the target. This can be amplified using a simple angled mirror, A technique quite common in instrumentation.
Anything indicated can only be twist and not wear.
Pete.
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I actually typed a response to using a laser and didn't post it before so here it is now.
The dot on the laser is massive, in terms of lathe alignment. You'll be lucky if you can get it down to a 10 thou diameter IF you can turn down the intensity. If you could get it to 1 thou it would still be too fat IMO.
The dot on the laser is massive, in terms of lathe alignment. You'll be lucky if you can get it down to a 10 thou diameter IF you can turn down the intensity. If you could get it to 1 thou it would still be too fat IMO.
addjunkie
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Id agree having played with a laser edge finder in both mill and the old lathe.
prepman
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Point taken....But that is surmountable IMHO. If you are looking for deflection the size of target image is irrelevant. However variance in size would be. But providing the centre of point can be determined it should be possible.
prepman
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Using trig' it appears that to get a 0.002 reduction on radius requires a vertical shift of 0.010 i.e.
On a 20mm shaft (10mm radius ) to reduce by 0.01mm radius (r) requires a vertical tangential shift of 0.1(y) as the shift gets greater the reduction ratio dramatically increases.
(r²) -(x²)=y² therefore
(10²)-(9.998²)=y²
= 100-99.96=(0.04)
= sqrt = 0.2mm
Need to check calcs but a small reduction in diameter needs a much larger shift in height?
On a 20mm shaft (10mm radius ) to reduce by 0.01mm radius (r) requires a vertical tangential shift of 0.1(y) as the shift gets greater the reduction ratio dramatically increases.
(r²) -(x²)=y² therefore
(10²)-(9.998²)=y²
= 100-99.96=(0.04)
= sqrt = 0.2mm
Need to check calcs but a small reduction in diameter needs a much larger shift in height?
Screwdriver
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An interesting method for using a laser would be holographic interferometry. I'm not even kidding.
Dunno why it's only just occurred to me, I wrote a thesis almost forty years ago. Using the same laser you could easily achieve an accuracy of 1/4 the wavelength of light! Not only that, the end result of the method for determining deflection is a zebra stripe pattern of interference bands which you simply count up to measure deflection.
Does involve faffing about with glass plates (holographic "film") but like I said, I am suddenly struck by the notion such a measuring system would be perfect for a large stiff oddly shaped casting and or it's accessories. You could even bolt the apparatus to the bed.
I might have a crack at making such a thing. The theory is horribly complicated but it's a super simple setup and I literally made everything except the laser.
Ironically, considering this sudden epiphany, made on a lathe!
Dunno why it's only just occurred to me, I wrote a thesis almost forty years ago. Using the same laser you could easily achieve an accuracy of 1/4 the wavelength of light! Not only that, the end result of the method for determining deflection is a zebra stripe pattern of interference bands which you simply count up to measure deflection.
Does involve faffing about with glass plates (holographic "film") but like I said, I am suddenly struck by the notion such a measuring system would be perfect for a large stiff oddly shaped casting and or it's accessories. You could even bolt the apparatus to the bed.
I might have a crack at making such a thing. The theory is horribly complicated but it's a super simple setup and I literally made everything except the laser.
Ironically, considering this sudden epiphany, made on a lathe!
pressbrake1
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I sincerely apologise and I will never blight this forum with my 34 years experience as a machine builder again.
prepman
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Go in peace my child......
