Buying a quick change tool post – Which one?

[mgnbukParticipant @mgnbuk]

Maybe the Emco clamping design was to get around patents for the cam locking device ? Or cheaper / easier to make ?

For all the naysayers denigrating them I can’t say I have had any issues with Dickson toolposts, either at work (Harrison M300 / Harrison VS330 / Colchester something-or-other / Harrison Alpha 400) or at home (Myford S7 / Warco GH600). The kit I fitted to the S7 came from Myford’s Spares Counter (with the “W” marking) – subsequently purchased holders from RDG and all fit & lock up without issue. The GH600 post came from Ebay & is of Indian origin. Seems well made and is certainly hard – I had to bore out the base to fit over a cast-in boss on the compound slide & it put up a good fight. All the holders I have (which appear to come from a number of manufacturers) fit and lock up without issue.

Couldn’t use a wedge-style TP on the GH600 as not enough material in the TP base to bore out to fit over the compound slide boss & the compound slide is not really thick enough to leave sufficient thread engagement for the clamp stud with the boss milled off.

“Which tool post” discussions seem to be akin to oil threads on motorcycle or car forums – regularly discussed & respondents all have their favorites.

Nigel B.

[VolansParticipant @volans]

Hello, its me again,

Amongst the tool holders i got with the AXA tool post is an inclined cutoff holder. Luckily, I noticed that the bottom of the blade was slowly moving out from the holder creating a nice bevel effect chuck side. is this a common problem with these? or was I just unlucky, getting a naff holder? I am a bit miffed about this but can’t think of a way to correct it.

I still have my small QCTP which I could adapt to go at the back. This holder holds the blade solidly, having a wedge device at the top which clamps the blade in & down.

I’ve read that cutting off from the back is better, and also read that it is a waste of time.

[Clive FosterParticipant @clivefoster55965]

There are three advantages to a rear mounted parting off tool.

1) The mount, and usually the tool, can be pretty much permanently fitted so it’s worth making the effort to get the tool exactly aligned. By its very nature a parting tool is weak from side to side and the cut heavy. The chip also has to come out of a narrow slot so it’s prone to jam. Anything less than perfect alignment makes it harder to get a reliable, clean cut.

2) A rear mounted tool goes direct on the cross slide. Taking the sliding joint of the top slide out of the equation makes things seriously stiffer.

3) The feed screw is in tension pulling the tool into cut. Inherently far stiffer than pushing where the screw can bend or shift slightly in an attempt to run away from the load. The tool can also be drawn into the cut so so things are floating in the backlash region so  the tool isn’t properly under control.

It may or may not be instructive to note that capstan lathes invariably have a rear mounted parting off tool. At production quantities you need reliable parting off.

Clive

[DiogenesParticipant @diogenes]

What blade is the AXA holder designed to take? ..if it’s an HSS one, check that all the faces that should be ‘square’ are actually square – especially the top, if it’s kicking out at the bottom – some of the ‘ready-profiled’ blades have subtle bevels in unexpected places..  ..ask how, etc..

The insert type are pretty reliable and effective.

I have an AXA copy with a couple of home-made p/off holders, I will post if I can find a picture.

I part from the front on GH600, don’t really have any issues.

 

[DiogenesParticipant @diogenes]

..note special screw spacing, er, to avoid, um resonance issues.

[VolansParticipant @volans]

Thanks for the replies. Mod’s here I come.

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