The Shop > Tools

Boxford CUD poor cutting

<< < (2/3) > >>

chipenter:
Sounds like the problem is the saddle any dings on the bed or ware and it caan rock , http://www.pulse-jets.com/boxford/boxford_know_your_lathe.pdf another on to look out for is Southbends how to run a lathe , Boxford is a copy of the Southbend 9" lathe .

RussellT:
Start with the simple stuff first.  Tool angles are crucial, chucking is important.

How much do you have sticking out of the chuck?  Is it the same bit you faced?  Is the material the same?

If you can face stuff OK I don't think there'll be much wrong with the lathe.

Russell

diagnosticated:
Thanks for welcome and suggestions guys.  I will try to take some dti measurements.  I was just confused because of the free play in the cross slide that I have removed with a washer.  Is it normal for the cross slide to have nothing to take up play?  I have the boxford parts diagrams and they do not show anything other than the two thrust bearings. (although the pictures are poor)

DTI measurements: 1" dia bar 8" long.
Run out at 1/2" from chuck. 0.002"
Run out at  5" from this point. 0.008"
With the dti set to zero when I move saddle to the 5" point the dti shows a deviation of 0.002"

I was not sure about the bar so I swapped to a known parallel and repeated above at 1/2" from chuck and 2. 1/2" from that point.
Run out at 1/2" from chuck still 0.002"
run out at 2. 1/2" from this point. still 0.002"
With the dti set to zero when I move saddle to the 2. 1/2" point the dti shows a deviation of 0.001"

So my results suggest a run out of 0.002" at least over the first 2 - 3" from the chuck.  Is this good enough?
The results also suggest an out of parallel of 0.001" over approximately 2. 1/2" Is this ok?

RussellT:
Yes it's quite normal for there be nothing to take up play.

However there are two sources of play.  One is the backlash between the cross slide screw and nut - there's not much you can do about that.  Even new screws and nuts won't reduce it to zero.  Some more expensive lathes have nuts that you can adjust to reduce the backlash.

The other source is the clearance in the bearing on the cross slide screw.  You can adjust that to a minimum, the handle is screwed on to the end of the screw with a lock nut and a grub screw to lock it in place so you can adjust that.

None of this should prevent accurate work as each time you advance the slide you are pushing it into the work and you have taken up all the clearances.  If the material and tool geometry combine to pull the tool into the work that may cause a problem - you can solve that to some extent by altering the tool geometry and making sure the gib screws are snug.  If all else fails you use a gib screw to lock the slide during a longitudinal cut.

Russell

diagnosticated:
Thank you for helpful reply Russell. The free play was not backlash as such. I have very little backlash.  The free play was literally two much spare space on the fixed end of the screw.  I could not take it up with the handle because the handle was in its factory set position which was already in as far as it can go.  That is what seemed odd. I replaced the thrust bearings thinking that these must have worn but with new bearings the clearance was almost the same. That is why I have now added a shim washer. The clearance is more or less zero now but I still have backlash between screw and nut which I expect.  The tool post fitted is mounted on ball bearings. It only allows the cutting tool to sit at 90 or 45 degrees to the center line.  Could this be a problem with index tooling?

Navigation

[0] Message Index

[#] Next page

[*] Previous page