frank brown | 15/05/2013 14:15:32 |
436 forum posts 5 photos | Just a little point has the tool got side clearance? Else the top edges of the tool will rub more and more as it cuts deeper. I would think that just stoning off the top corners, back to the cutting depth may help. Frank |
petro1head | 15/05/2013 14:28:46 |
![]() 984 forum posts 207 photos |
Posted by OuBallie on 15/05/2013 13:15:45:
That's the one. Next to a QC Toolpost, this is the best investment you could make. There is a square bar screwed onto the tip holder that will fit the Toolpost. A VFD comes ahead of these, having now had experience using such. Geoff - Cheese on toast then coffee. Edited By OuBallie on 15/05/2013 13:18:47 Whats a VFD? Edited By petro1head on 15/05/2013 14:30:14 |
David Littlewood | 15/05/2013 16:05:55 |
533 forum posts | Petro, VFD stands for variable frequency drive. It is a box of tricks which is used to drive a 3-phase motor (much smoother and more efficient than a single phase one) and to allow the speed to be varied on the fly (i.e. by twiddling a knob, not stopping to change belts or gears). I can confirm the the Q-cut sold by Greenwood Tools will fit quite comfortably in a size S00 Dickson toolholder (Myford 7-series size). I can also confirm, as a previous gent said (can't see previous page while typing this) that it's the best parting tool I have used, and I've tried quite a few. It's not just a bit better, it's in a different league; you can easily part off under power, and without resorting to backgear. It is however vital, whatever tool you use, to get it absolutely perpendicular the the bar being parted, or it will rub on the side as it goes in. David Edited By David Littlewood on 15/05/2013 16:06:31 |
Stub Mandrel | 15/05/2013 16:10:47 |
![]() 4318 forum posts 291 photos 1 articles | I have found that with the 1/16" parallel sided blades you don't need to do anything other than bring the end to a good finish with suitable clearance, and mount the tool at a suitable angle. It is, however, essential that the tool is properly aligned at right angles to the lathe axis or it will bend and start to bind. VFD - variable frequency drive - a combined speed control and inverter for 3-phase motors.
Neil - <lunch menu redacted> |
Bob Perkins | 15/05/2013 21:00:38 |
249 forum posts 60 photos | Hi Petro my two penneth.... I have a "mini lathe" and a similar parting tool to the one in your picky. I to had the same problems your having. Convinced I was doing every thing correctly and deciided rear tool posts and parting tools with inserts must be the way to sort out my parting.... Lets throw some cash at it. I took a step back and went back to basics. There is some excellent advice above. As a start, and don't laugh but my parting tool was in the holder upside down. I reduced the overhang, made sure the tool was square to the work and set to the correct height and locked up all the slides, correct speed and a constant feed. I even turn of radio 4 so I can listen to the cut, as you can hear when things are not right. Parting is now fine and I've even ground up a few parting tools for some fine grooves in my latest project. Keep at it. Bob.. |
Steve Withnell | 15/05/2013 21:40:34 |
![]() 858 forum posts 215 photos | The parting-off problem is quite often in the set up and actually difficult to resolve without using a rear toolpost. I think the geometry of a rear toolpost is more important than it being at the rear, but that's an opinion. If you take a standard parting off tool and holder in the toolpost, the cutting forces can have two quite big levers to play with. One is the distance between the centre of the tool post to the tip of the tool (across the bed) and the distance from the centre of the tool post to the axis of the tool measuring up the bed. A rear tool post eliminates the latter of these levers, and can minimise the former. I haven't tried a rear tool post at the front! Anyone done that comparison?
Steve |
ega | 19/09/2013 11:54:59 |
2805 forum posts 219 photos | Someone experiencing parting off problems would do well to start by reading the relevant passage in George H Thomas's book. My own experience improved radically when I built his rear toolpost some years ago. More recently, I invested in a Greenwood KIT-Q-CUT and had very good results using it in a custom turret on the GHT toolpost on a Super Seven. The Greenwood tool is based on a Sandvik p/o blade and insert and appears to be half a standard double-ended blade fastened by two countersunk screws to a rectangular block intended to be gripped in a clamp type toolpost. This design works but is not as robust as the standard Sandvik arrangement, the shear strength of the screws being the limiting factor. At some stage I added a third screw and later still three dowels. The beefed up tool also worked very well in the standard toolpost on my larger lathe until I had a major seizure and succeeded in breaking both tip and blade (I will aim to post a photo of the result). This happened shortly after I had bought two replacement tips including one of the new ones with an angle to reduce the pip. When I learned that the standard, double-ended Sandvik blade, costs about £70, I decided to try the Front or Rear tool advertised on this site and find it excellent. If anyone wants to take the two Sandvik inserts off my hands at cost less 10% they are welcome to message me. There are cheaper versions eg the Glanze but this is not as effective as the Sandvik in my experience. Happy parting! |
Danny M2Z | 19/09/2013 12:52:37 |
![]() 963 forum posts 2 photos | >>> The parting-off problem is quite often in the set up and actually difficult to resolve without using a rear toolpost. I think the geometry of a rear toolpost is more important than it being at the rear, but that's an opinion. <<< For minilathe owners (or anybody else with a bolted on chuck). A parting off tool may be mounted upside down in the front toolpost and the lathe run in reverse for the advantages of this method of parting off. You will probably need a quick change tool post to drop the cutting edge to centre height. Regards from the land ofd the kangaroo * Danny M * |
mechman48 | 19/09/2013 13:13:50 |
![]() 2947 forum posts 468 photos | I have the same parting off tool but have fitted it to the rear toolpost that I made from Hemmingways kit (disclaimer) & it works fine, have parted off Brass & 1" MS under power without any probs but ensured that I had neat cutting oil dripping on the mild steel. The tool, being horizontal, had some top rake ground on to approx 5-7* to help curl the cuttings,you can just see it in the pic (tool is upside down). Much more rigid & no flexing of blade or convex/concave washers.Just ensure that the blade is square on to the work. Cheers George |
jason udall | 19/09/2013 19:07:55 |
2032 forum posts 41 photos | George..your photos show one other secret of parting off...have a hole up the part... When the part off reaches the smallest radius the surface speed falls off dramatically. Of course with constant surface speed turning this particular problem goes away.. |
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