Thread: Parting tool mounted on rear tool post advice needed

Hi All

I recently purchased a siege C4 lathe, I am thinking of putting a second tool holder on the back of the cross feed table and putting a parting tool in it upside down as I understand things, that I have read on the net. Could I get some feedback on this method of parting.
It is my understanding that it’s a lot more user friendly way of parting and reduces jamming given that tool is sharpened right I tend to use HSS most of the time. Thanks in advance Colbra

Hi Col,
I have never tried it but from what I have read it is a lot better especially for less rigid lathes.

Dave

Colbra,
I have a rear mounted parting set up on my lathe that is a bit bigger than your C4 and it works a whole lot better than a compound monted parting tool. My lathe is an AL1000D (14"-40"). A friend of mine has the size smaller Seig lathe than yours I think it is a C2 and we made up a rear parting set up for it and he can now part off. Using the compound for parting was a constant gamble and he broke plenty of blades. Do a Google search for one of the forums covering your lathe and I am sure you will come up with lots of good ideas to improve your machine.
Bob

I have one. I like the way it works. More here : http://www.woodworkforums.com/f65/pr...13/index2.html

BT

Thank you Gentlemen for your input on my questions, if I could ask a couple more please! My understanding of putting the parting tool at rear of the cross slide is that it is installed upside down! But the lathe run the conventional rotation, you can achieve a similar out come by running the lathe chuck in reverse and the tool upside down in the front and achieve the same outcome. Is my interpretation of this procedure correct.as I have already explained to Dave on other machining questions this is only the start of my journey in the metal side of this forum and although I do have some other machinery I have very little hand on experiences thank you Colbra.

Yes, you can Colbra - as loing as your chuck is not SCREWED on. If it is, any grab at all and it will unscrew and jump off your lathe. It it hits you or falls on your toes, you WILL be sorry you did that....
Joe

The difference is that with rear mount you remove the compound from the equation, which means more rigidity. But maybe that doesn't matter as much when cutting this way? I haven't tried it. But after tonight's episode I might. Every time I think I've got parting sorted it bites me.

Colbra,
By mounting the cut off tool at the rear you only have one set of dovetails, the cross slide set.Mounting at the front you have two sets, the compound set are also considerably smaller and more flexable, the result is a much less ridgid set up. This is why the rear mounting is the best. You do loose a bit of range when both setups are in use. When we did the smaller C2 lathe we made the rear toolpost a quick disconect style so it was only attached for parting off.
Bob

Does any one know if Hercus still do an extended cross slide for a 9" Model A so as I can fit a rear parting off tool post and also a taper turning attachment.

Regards

Garry

Originally Posted by Garry Edwards

Does any one know if Hercus still do an extended cross slide for a 9" Model A so as I can fit a rear parting off tool post and also a taper turning attachment.

Regards

Garry

Garry,

Mine is a 260 slide purchased new maybe 6 years ago from Hercus. It raises the height of the compound slide about 4mm. The Hercus TTA has an entirely different cross slide. I haven't bothered to see if the extended slide could be adapted to suit the taper attachment.

Bob.

Thank you Gentlemen for your answers, I have two lathes the bigger and older one is a AL330A, the attachment method is by cams for the chucks, and has reverse on the spindle head. So I would be able to invert the parting tool on the front on this lathe.

On the Sieg C4 there is no spindle reverse although it is possible to do this I think by this method Year of the Basement: Can lefthanded threads be made on the SIEG C4? if I am on the wrong track with this reversing method please advise me.

On Bobs and Joes advice I will make up a rear tool post for the C4 lathe with the feed table tee slots for the milling attachments, it should be easy to make this a relative simple thing I Hope
Byran I understand your frustrations with the parting off tool dilemma, I hope bringing this topic up, and the answers all these Gentlemen have given has helped you as much as it has helped, me

I am sorry for pushing back in Garry LOL
Colbra

HI Col,
another plus for parting off with a rear tool post is that any play in the headstock spindle is negated which in theory is the same as when using a front tool post and running the lathe in reverse.

Phil

The other plus of a rear parting tool is that usually the position the rear parting off tool occupies is such that the cross slide is using a relatively unworn section of screw - less movement.
The whole parting off thing comes down mainly to rigidity - if you haven't got it, you will have trouble. This requires (as Phil said) no headstock play (worn bearings, not enough pre-load, loose chucks); work piece and tool rigidity (parting off next to the chuck, no excess stick out of parting tool, enough material in the chuck to securing hold the work) and no (minimal) cross slide play (gibs tightened up correctly, no backlash, tools tight in holders/ posts). Other axis should be firm too - lock them if in doubt.
A spot of lubrication does help, your tool does need to be on centre height (close enough is not good enough here) and often overlooked, needs to be square to the machine axis - I do this by setting parallel to the chuck or faceplate.
The tool should of course be sharp but if you are using parting blade with a taper or T section, only sharpen the top and front - not the sides. I have a cheap diamond hone that I use to touch up the cutting edge before use. Some people grind the front of the tool with an angle to remove the pip on a parted piece but I find that that tends to steer it in the work (=jam). Lots of sources say that you must slow down for parting but I run at normal cutting speeds (the steel doesn't know you are using a parting tool and so doesn't adjust itself to cut efficiently at a lower speed when you change tools). Feed in slowly but evenly.
A lot of the problems seem to be due to the tool binding in the cut, so clearing chips out is important - some people grind a groove in the middle of the parting tool that (I'm told) folds the chip so that it will clear better. With deep parting I sometimes plunge in for 2 or 3mm, back off, move sideways a 1mm or so, plunge again to a 2 to 3mm beyond the first cut and repeat. This prevents chips accumulating and jamming in the cut between the material and the tool.
A thin parting tool is better, but you must balance that off against (sideways) flex. Unfortunately mini-lathes are at a disadvantage when it comes to parting off as they haven't got the mass, power or rigidity of a larger lathe but should still be able to part most materials. With the more difficult materials it's back to the bandsaw...
I hope these thoughts are useful.
Michael

Originally Posted by Michael G

The other plus of a rear parting tool is that usually the position the rear parting off tool occupies is such that the cross slide is using a relatively unworn section of screw - less movement.
The whole parting off thing comes down mainly to rigidity - if you haven't got it, you will have trouble. This requires (as Phil said) no headstock play (worn bearings, not enough pre-load, loose chucks); work piece and tool rigidity (parting off next to the chuck, no excess stick out of parting tool, enough material in the chuck to securing hold the work) and no (minimal) cross slide play (gibs tightened up correctly, no backlash, tools tight in holders/ posts). Other axis should be firm too - lock them if in doubt.
A spot of lubrication does help, your tool does need to be on centre height (close enough is not good enough here) and often overlooked, needs to be square to the machine axis - I do this by setting parallel to the chuck or faceplate.
The tool should of course be sharp but if you are using parting blade with a taper or T section, only sharpen the top and front - not the sides. I have a cheap diamond hone that I use to touch up the cutting edge before use. Some people grind the front of the tool with an angle to remove the pip on a parted piece but I find that that tends to steer it in the work (=jam). Lots of sources say that you must slow down for parting but I run at normal cutting speeds (the steel doesn't know you are using a parting tool and so doesn't adjust itself to cut efficiently at a lower speed when you change tools). Feed in slowly but evenly.
A lot of the problems seem to be due to the tool binding in the cut, so clearing chips out is important - some people grind a groove in the middle of the parting tool that (I'm told) folds the chip so that it will clear better. With deep parting I sometimes plunge in for 2 or 3mm, back off, move sideways a 1mm or so, plunge again to a 2 to 3mm beyond the first cut and repeat. This prevents chips accumulating and jamming in the cut between the material and the tool.
A thin parting tool is better, but you must balance that off against (sideways) flex. Unfortunately mini-lathes are at a disadvantage when it comes to parting off as they haven't got the mass, power or rigidity of a larger lathe but should still be able to part most materials. With the more difficult materials it's back to the bandsaw...
I hope these thoughts are useful.
Michael

Very useful, Michael, a good summary.
Bruce

Originally Posted by colbra

On the Sieg C4 there is no spindle reverse although it is possible to do this I think by this method Year of the Basement: Can lefthanded threads be made on the SIEG C4? if I am on the wrong track with this reversing method please advise me.

Im not sure what you mean but spindle direction is changed by simply hitting the reverse button.

Changing the idler gear reverses the direction of the lead screw relative to the direction of the spindle. So the the spindle will rotate in forward but the lead screw will work in the reverse direction. This allows for left hand threading and power feed from the chuck towards tailstock.