mike 109444
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Just remember if you are doing internal boring then the reverse is true !!!
Yes you need to wind the toolpost in and not back it out, your doing it ass about face which is giving you the problems.
You should not drag the tool back along the previous cut (bad habit!). So at end of cut you would wind off say one turn of cross slide, return to home position (with the one turn of cross slide still there) then turn one turn back in on cross slide and any additional amount for a further cut, The back lash in the cross slide has now been (for want of a better description) pushed back so when tool makes contact with work cut it can't push the back lash as it is not there. Hope that makes sense!
Just remember if you are doing internal boring then the reverse is true !!!
If possible when you screw cut on a machine with this restriction you would try to wind the tool out as it approaches the end of the thread and then stop the motor. This takes a bit of practice !!!! and can lead to crashing the tool into a shoulder. Where possible have an under cut at the end of the thread to run into. Usual thing is to mark the dial or the bed at the point where the tool should be wound out. And of course internal threads are the revers !!! So easy to wind tool wrong way and screw job up (usually on the final cuts )The student has metric feed speeds, its just the indexing is imperial so you cannot disengage the feed at the end of your first pass or you will never get it to engage on the same thread, so you have to stop the lathe with the feed still engaged, back the tool away, wind it to the beginning and re start the feed. You have to repeat this until the required depth is reached on your thread. I am new to this and i may be wrong, this is all based on research, not knowledge.
I have the original 3 phase motor on mine and for metric threading I use this method.
Engage the threading lever and leave it engaged for the whole process.
Take your first cut and at the end of the cut simultaneously disengage the clutch and retract the tool.
Hit the motor reverse switch and re-engage the clutch which will wind the carriage back to the start and disengage the clutch again.
Put the motor switch back into forward, advance the tool and engage the clutch again to do your second cut.
Repeat till done.
You can only do this with the 3 phase motor as its happy to be switched into reverse while running.
If you have the single phase motor you do the same but you have to stop the motor and restart it to change direction each time.
You should be fine then, mine takes about a second to reverse direction.Thank you, I will try this. Mine is three phase (proper three phase, not phase converter or vfd)
I have recently purchased my first lathe, a mk2 Colchester Student.
I cannot feel any play in any of the slides, but there is a tight spot on the cross slide. I am struggling to get a reasonable finish on most materials at the moment but that is mainly down to the blunt inserts and my replacements haven't arrived yet. I have also ordered some hss stock for making my own tooling for turning mild steel.
If i switch the lathe off, or the power feed the tool will dig in to the work piece. It will also dig in if i get to the end of a cut, disengage the power feed and return to the start of the next cut without backing the tool away. This puts a reasonably deep "reverse thread" on the piece.
There is a reasonable amount of backlash on all of the slides and i do compensate for this by over turning the dial and backing off to the desired depth of cut etc.
I have no previous experience of lathes bar a brief spell at college many years ago and occasional use when i worked for a motorcycle restorer, again a long time ago. Is this behaviour usual or is there something i should look for? The chuck is LO taper mount three jaw and runs true.
I'll let someone else link to a video of how to be able to disengage feed while mixing standards for threadcutting
It is also possible to set tool up at back of cross slide and run machine in reverse so you are cutting from the shoulder out (away ) from the chuck direction. I am trying to picture the set up now as it has been MANY years since I worked the handles at BAe If I am thinking this out correctly the tool has to go up side down but you do have to be careful with this as the cut is now trying to "lift" the tool post rather than when at front where it is pushing "down" on tool (and tool post)
It's a spring cut. Don't worry about it, get close to size then take a spring cut for the finish. Look at doubleboost vids for help on this.
Compound ????Thats interesting knowledge too, so you then set the compound to circa -30* as opposed to the normal +30*? Assuming the saddle will move far enough to the left to allow this.
My understanding is you cannot disengage the screwcutting lead nut when cutting metric. Not on my older Colchester Student. You have to withdraw the tool, stop, then reverse the motor and drive the apron backwards with the half nut always engaged. When cutting imperial (on mine) you can use the screwcutting dial to re-engage the drive in the correct position.
For this very reason, I still haven't ever actually used mine to cut a thread!
S.
Compound ????
I mean the cross slide, assuming your cross slide will go far enough past the work piece or you have a rear mount for tool post
Ok i misread that, didnt realise we were behind the work piece, thought we were still in front but cutting left to right. So behind work piece, tool inverted, and compound set the same but wind it out to cut deeper ect as everything is backwards and need to be careful looking over the work piece to see. So as stated, only advantage is moving away from chuck, not towards it. Got there in the end but a handy one to remember if only to be used when needs must, like no relief at end of cutTo cut a normal right hand thread from the shoulder out the tool goes at the back, right way up with the chuck and feed in reverse.