Johnnybravo
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No issues with regrinding jaws as long as it’s done properly, which most people don’t
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prepman
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And even when they do they're left radiused, not flat as originally.
Kram
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When I chuck up a part, I look for light and use the smallest feeler gauge to check.
A problem with bell mouthed chucks is the jaws are hardened, it will be the body that is bent. Regrinding is unlikely to fix it over the full clamping range - so I have not tried.
A soft copper shim on each jaw will form itself to the gap and give much better clamping.
A problem with bell mouthed chucks is the jaws are hardened, it will be the body that is bent. Regrinding is unlikely to fix it over the full clamping range - so I have not tried.
A soft copper shim on each jaw will form itself to the gap and give much better clamping.
Johnnybravo
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Have a good look at a set of jaws. They are radiused from new. Well , the jaws on the Colchester Mastiff are, the jaws for my Bison are, the SWM auto blok ones are, as are the ones from my Hitachi Seiki
Johnnybravo
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I reground a set of jaws for the Mastiff using the jig I made in the photo. Totally transformed that chuck.
prepman
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Just been experimenting with headstock bearings. Fully slackened the retaining ring and it made little difference to deflection, which is barely discernable. Thickness of the pointer (if that). However run-out on my backing plate is about 0.8mm. I'll remove chuck clean and retry. If not improved I'll skim up. Think that's where my vibration is. Gearbox oil changed as it didn't look so good. Plenty of gear powder.
o
o
prepman
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I'll have a look, they didn't seem radiused to me. Or do mean you convex, which would be fine. Concave isn't what I would want, except on soft jaws.
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Johnnybravo
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Most chuck jaws are ground concave
prepman
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You are absolutely correct.
They are radiused. The chamfer fool me. Goes to show that's how they are produced. That's probably why the Chinese chucks are full of grit and need flushing out? My old chucks were so knackered that I presumed that has how they got a radius. However this a relatively new chuck.I used small square pieces in the chamfers of the jaws when I ground my Myford one, it has the same effect as yours, but is fiddly.
Excuse me...... I'm off to buy a hair shirt.
prepman
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Because of a pretty nasty parting operation and an indication of tapering, I needed to check alignment. I also adjusted the ball bearing feed safety clutch on the feed shaft and changed all oils. Clamped the saddle to test it. OK.
Next was to check alignment.
Did a few tests on the lathe. Clock gauges on the chuck to see if any change.
Slackened the headstock bolts tapped and retightened. Changed on cross axis.
Machined the test bar gripped in chuck and got 0.025mm difference over 200mm. I can live with that.
Then I used the test bar between centres.
Horrendous!
The results gave a ridiculous taper, didn't even need to measure it.
Ran the centres together....
Yipes! Thought I'd try a different centre.
More respectable. So lesson learnt.... using a tailstock centre to check tailstock alignment can give false results. The 1st centre is from the ML7 and needed a MT adaptor. I suspect there lies the answer.
Still haven't concluded anything on pre-loading the headstock bearings. Nothing seems condusive. Perhap Gamet cus serv will help, or not?
Next was to check alignment.
Did a few tests on the lathe. Clock gauges on the chuck to see if any change.
Slackened the headstock bolts tapped and retightened. Changed on cross axis.
Machined the test bar gripped in chuck and got 0.025mm difference over 200mm. I can live with that.
Then I used the test bar between centres.
Horrendous!
The results gave a ridiculous taper, didn't even need to measure it.Ran the centres together....
Yipes! Thought I'd try a different centre.More respectable. So lesson learnt.... using a tailstock centre to check tailstock alignment can give false results. The 1st centre is from the ML7 and needed a MT adaptor. I suspect there lies the answer.
Still haven't concluded anything on pre-loading the headstock bearings. Nothing seems condusive. Perhap Gamet cus serv will help, or not?
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prepman
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Now for something completely different......
When I checked the Student lathe to find out why the oil point on the leadscrew end bush was blocked. It turned out that the casting core had never been cleaned out. So for 60yrs it wasn't used. Must have been oiled from the ends.
On my Senior Major mill the suds pump belt wouldn't last. Turned out that the pump had never been completed. The relief valve for the positive displacement vane pump had not had all the drillings done and was overpressurising.
So much for 60's QC?
When I checked the Student lathe to find out why the oil point on the leadscrew end bush was blocked. It turned out that the casting core had never been cleaned out. So for 60yrs it wasn't used. Must have been oiled from the ends.
On my Senior Major mill the suds pump belt wouldn't last. Turned out that the pump had never been completed. The relief valve for the positive displacement vane pump had not had all the drillings done and was overpressurising.
So much for 60's QC?
Munkul
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Yup. Anyone who thinks Colchester/Harrison had great build quality is sadly mistaken. The castings and design- well enough... the assembly... barely better than chinese stuff today. Some really good machines out there... and some real friday/Monday machines
prepman
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Chinese quality has improved a lot. Made in Japan was the pits in the 60's...and now?
Munkul
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Absolutely, thats what i mean. Current chinese assembly quality varies a lot but on average probably about the same today as Colchesters assembly back then...
prepman
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As Sean Lock said " I'm practically Chinese" But didn't we used to be an engineering nation?
Munkul
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We still are, if you look around. Just not a manufacturing nation.
prepman
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'A nation of shopkeepers'
As I commented on my Harrison Mill thread.
It's a genuine mix of beautiful precision and half arsed bodgery.
Like the Lo-Vo Lite that is mounted on three screws that are drilled through into the gearbox so if you remove it then it leaks oil through them.
Or the two holes for the powerfeed electric power/control cables that are bored at different heights.
Or the wonky drilled holes in the control box.
Or the front control panel that turned out to be a trapezoid and fitting a rectangular panel means it looks "off".
Maker
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I've not noticed anything on my Chipmaster to suggest half assed bodgery. I'll be very surprised if in sixty years people are still selling 7x14" Chinese lathes from "the twenties" and discussing how good they are on forums.
