The Ultimate Trick: Cutting off with the Mini Lathe

[chuckorlando]

Well bubba, the more I think on this the harder it is for me to reason it. I think I might have to agree

That is very true but I'm not sure it applies for the turning cut. It would be like pushing the tool upwards and having the cutter on the lowest part of the workpiece and this is not the case. It works great for cutting cheese slides though. The phenomena seems to be related to the better rigidity for tangential cutters, but in a opposite way.

I do also avoid reverse turning by the reason you say. A rotating chuck that come loose is very dangerous, especially if it is a heavy beast and there are not many threads to hold it so it can happen within a fraction of a second.

 

[TTD]

FWIW, my personal experience on the 7" asian lathes: cutoff with a hacksaw, then face your part.

^^X2...that's what I've been doing for awhile now, especially with steel. A little more work/time, but way less nerve-racking and easier on the machine.

Although, after seeing this thread I just tried the "upside down/reverse" method a few minutes ago on some scrap pieces of brass/aluminum and have to admit it worked like a champ...not even a hint of chatter or diggin' in like before.

I "kinda-but-not-really" understand the theory behind it, but after trying it I can say that it definitely made a huge improvement...at least for me on my small, non-rigid machine.

 

[Micke S]

Well bubba, the more I think on this the harder it is for me to reason it. I think I might have to agree

I begin to think that this applies only for a tool holder or toolpost that swings to some degree as in the simulation. In such case it will combine hard cutting force with an automatic anti-jam function.

 

[Karl_T]

Although, after seeing this thread I just tried the "upside down/reverse" method a few minutes ago on some scrap pieces of brass/aluminum and have to admit it worked like a champ...not even a hint of chatter or diggin' in like before.

OK, have you got the balls to put a piece of 304 in your lathe? Then we'll know for sure. AND I haven't hurt my neighbor's lathe :rofl:

 

[chuckorlando]

The only thing I can think is it's pushing the tool post up instead of down which in effect makes the tool go back instead of in. Same principle as up side down tool on the back side of the work I believe.

 

[MozamPete]

It is working exactly the same as a rear mounted parting tool post which seems to be accepted as a better way to part off (at least on Myford lathes for which there are various designs around for home build ones and was available as a OEM accessory from the factory).

Other advantage of a rear mounted tool is that as it mounts directly to the cross slide you eliminate any possible slack/movement in the top slide (as well as obviously not having to run the chuck in reverse).

 

[TTD]

OK, have you got the balls to put a piece of 304 in your lathe?

LOL...not having the cajones to try something new has never been an issue for me (not always a good thing!)...it's more the thinking it through/possible ramifications process I have trouble with!...:biggrin:

Being a newbie to machining I'm sure it has more to do with a lack of experience on my part, but ya, if I had some 304 I would try it, if for nothing else than to share a horror story with you all!

 

[RVJimD]

I have a little Unimat out in my unheathed shop that I ALWAYS had trouble with parting off! I may just bring that little sucker into the shop today and give this a try just to see. It would really make a big influence on my decision to use the little lathe.

stay tuned for a video...

jim

 

[epanzella]

The only thing I can think is it's pushing the tool post up instead of down which in effect makes the tool go back instead of in. Same principle as up side down tool on the back side of the work I believe.

I think you've got the answer. The only real difference is whether the toolpost leans towards or away from the cut under load. An inverted tool at the rear is the only way you can get the TP to lean away if you can't reverse the spindle (threaded chuck). With a camlock spindle an inverted tool in front with the spindle in reverse would act the same as an inverted tool in the rear with the spindle going forward. IMHO. They would both cause the load to lean the TP away from the work.

 

[Wreck™Wreck]

The only thing I can think is it's pushing the tool post up instead of down which in effect makes the tool go back instead of in. Same principle as up side down tool on the back side of the work I believe.

One of the advantages of tools on the back of the part (up side down) is chip control, the chip falls into the pan below the tool, it also allows more room for tools on the front side (on a lathe that only has one cross slide such as a gang tool machine).