Brad93
Member
- Messages
- 18,175
- Location
- Essex, United Kingdom
The lathe at work is fitted with what i believe are soft jaws. They are of a style which has a groove cut into the face. The groove is about ⅜-10mm wide. I have found a plain steel ring which fits the groove in the jaws so I assume you clamp the ring in the groove to load the jaws with equal pressure as they would experience gripping work.
I have watched Mr. Renzetti and Mr. Crispins videos on grinding/hard turning chuck jaws.
So the jaws don't appear to have been touched up in some time - you can see the wear in the jaw. This lathe gets used with all sorts of diameter of shaft but mostly around the 40mm mark.
It does clamp quite concentrically (usually within 2thou) but I'd like to get it better as the shafts I'm working on need to run very accurately (rotors from roots blowers).
So first question:
I have this ring which appears to be made for the job. However if I chuck it up in the groove, the jaws may be set at 40mm currently - machining them will make them oversize for a 40mm shaft and then they may not grip as effectively.
Do I just take a little bit off the OD of the ring (on the other lathe which has conventional jaws).
In my mind this will make the soft jaws move inwards to give me some material to skim off and true them up to a 40mm shaft again.
Second question:
If i do the above i need to bore the jaws to 40mm exactly. Am I best to use a 40mm shaft or plug gauge to judge the size of the bore - as a telescoping gauge doesnt work across 120 degree?
Of course I can use the DRO and set my boring bar offset on a piece of tube etc prior to starting work on the jaws.
There may be more sets of jaws laying around at work so i could make a set for each common shaft size. So another question is:
If I remove one set of jaws for say 40mm shafts and fit a different set precut for 30mm shafts, will they continue to be concentric or will they need recutting everytime they are swapped? In which case I'd have to keep whittling down the clamping ring to give me stock to remove from the jaws.
I have watched Mr. Renzetti and Mr. Crispins videos on grinding/hard turning chuck jaws.
So the jaws don't appear to have been touched up in some time - you can see the wear in the jaw. This lathe gets used with all sorts of diameter of shaft but mostly around the 40mm mark.
It does clamp quite concentrically (usually within 2thou) but I'd like to get it better as the shafts I'm working on need to run very accurately (rotors from roots blowers).
So first question:
I have this ring which appears to be made for the job. However if I chuck it up in the groove, the jaws may be set at 40mm currently - machining them will make them oversize for a 40mm shaft and then they may not grip as effectively.
Do I just take a little bit off the OD of the ring (on the other lathe which has conventional jaws).
In my mind this will make the soft jaws move inwards to give me some material to skim off and true them up to a 40mm shaft again.
Second question:
If i do the above i need to bore the jaws to 40mm exactly. Am I best to use a 40mm shaft or plug gauge to judge the size of the bore - as a telescoping gauge doesnt work across 120 degree?
Of course I can use the DRO and set my boring bar offset on a piece of tube etc prior to starting work on the jaws.
There may be more sets of jaws laying around at work so i could make a set for each common shaft size. So another question is:
If I remove one set of jaws for say 40mm shafts and fit a different set precut for 30mm shafts, will they continue to be concentric or will they need recutting everytime they are swapped? In which case I'd have to keep whittling down the clamping ring to give me stock to remove from the jaws.