Parting off – front or rear

[Sam Longley 1Participant @samlongley1]

I no longer use the topslide on my Warco 250MV because everything is so flexible. I certainly cannot use the quick change tool post for anything other than with a light boring bar. I have a solid block of steel set on the cross slide with the 4 way tool post set onto that. It is about as rigid as one can get. I have made it so that most tools, such as indexible ones do not need shimming.

I have a 25mm deep cut off tool holder & I mount a 13mm* 2mm exide tapered steel blade in it. I just grind a bevel on the front that looks right & touch it up with a stone. The holder obviously does not fit in the tool post so I bolted 15 * 15 piece of bar on the side. I then milled it to 12 deep such that it fitted in the tool post & the cut off blade sits dead centre.It has a very slight curve in the bottom & by tightening the 3 clamp bolts unequally I can force the blade up or down .25mm as it rocks in the tool post by a few of thou. That gives me a solid holder in a solid tool post.

I find it works OK on steel at 180 RPM,with lovely curled chips if I can maintain an even feed. I would like to run slightly slower, but the lathe keeps stopping, as the variable speed is carp at low revs

As for cutting oil I find that chainsaw blade lubricant seems to work OK. I have found a particularly "sticky" one. Not sure of grade or make. They sell it locally

[Mick B1Participant @mickb1]

It depends on the work you do and your priorities. I use my vertical slide a lot on my Warco, and a rear tool post would just make mounting that a load more complicated, plus I don't have enough need for rapid parting-off, or enough difficulty doing so, to justify making one.

[Tony Pratt 1Participant @tonypratt1]

I too replaced my Warco 290V top slide with a solid CI block & didn't like it at all, I found it very restrictive with no swivelling facility, I also use a rear tool post so I couldn't fit the top slide back on as & when needed. My solution was to completely re-machine the Warco top slide to a decent stand of workmanship & I am now very pleased with it, plenty rigid enough now for heavy cuts, you can indeed make a 'silk purse out of a sows ear'.

Tony

[RobinParticipant @robin]

I thought this was a wrinkle for spindles running in bronze bushings.

Normal wear on the bushing is at the top.

By putting the parting off tool at the back upside down you could use the unworn bottom of the bushing.

If you have tapered roller bearings then it is for fun only.

I like fun.

I could be completely wrong about this, but not about the fun part

[Alan JacksonParticipant @alanjackson47790]

I use this vertical parting tool on my Stepperhead lathe

and a rear mounted HSS parting tool on my Chipmaster

Both work well

Alan

[Dimitri DVParticipant @dimitridv76237]

Nice to learn how we all try to get around some fundamental rigidity issues on our – mostly – smaller lathes.

The setup with the front rotatable compound Z-slide is flexible but a disaster in terms of rigidity. My posting above is about keeping the possibilities of this compound slide, having a fast Dixon-type of toolchanger and still being able to do some fast and heavy cutting in groove or part-off from the front side. And with CNC running things. Plus coolant spraying. For CNC runs, I lock up the compound slide with the four hex side screws. Not ideal.

To compensate for that flexing tower I need to part off in reverse as mentioned before.

I need the Dixon and the compound in some cases, otherwise I would have replaced the toolpost and compound assembly by a solid steel block instead like some of you have done.

Next step is CNC internal /external threading large diameters with a servo spindle and a modified controller.

[Howard LewisParticipant @howardlewis46836]

FWIW, having had problems with parting iff in the front toolpost on a Myford, after making and fitting a rear toolpost , never looked back.

When I changed my lathe, one of the first jobs was to make a four way indexing rear toolpost.

Am now so confident, with a very old HSS blade, that I often part off under power!

Trying a carbide tip parting tool, in the front toolpost resulted in jam ups, and finally damage to the holder!

Howard

[Author]

Posts