Parting off and general HSS tool sharpness

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Bert:
Hi Ross

Here is a link to tool bit grinding I am sure you will help you get a feel for what is involved.
This gent has put up a ton of useful info. Snoop around his other postings and you will learn a lot.
He is a retired high school teacher who just can't stop teaching.

The other thing you may want to do is a Google search for "mini lathe tuning" lots to learn and you will begin to understand all the variables that are involved in the workings of all lathes.
If you are looking for project ideas consider making metal handles to replace the plastic ones on your new lathe. Straight forward undertakings complete with patterns that you will find satisfying simply because they will personalise your lathe.

Regards Bert

raynerd:
Just my little addition to the conversation. I was having huge problems parting off until about 6 months ago when I purchased a tipped parting off tool which worked really well. However, a month after buying the tool, I had an accident with it and the blade snapped. Before ordering another tipped parting tool I went about trying with HSS blades and I can now part just fine!

I can also part with a hand graver on my 8mm watchmakers lathe so to say your lathe isn`t upto the job is totally wrong!

The blade you are using looks very thick! That isn`t to say it won`t go through but it`ll be certainly much less forgiving than a thinner tool.

1. Check your centre height of the tool. Everyone swears on having it bang on centre - I`m happy bang on centre or a hair below.
2. use a thinner parting tool.
3. Worse case, purchase a tipped tool to observe the profile and how it stripps off the metal - I transfered this shape to my tools after seeing how one worked!
4. Go for it - push into the work especially at the start. I use to say I couldn`t part and in retrospect, I don`t think I was pushing into the work hard enough. Don`t get me wrong, you don`t need to force it but just because it might make a bit of noise doesn`t mean it isn`t cutting - especially when it gets going!
5. Lock up all your slides so the only movement is the parting tool going into the work piece
6. Make sure the tool is sharp with good clearence.
7. Make sure the parting tool is perfectly square to the front face of the job.

I`m no parting god but I have been in your shoes and even posted messages on here saying that I can`t part! I am thankful I can part and persistance is everything, don`t keep jumping for the hacksaw.

All the best.

Chris

andyf:
I can't get on with my blade type parting tool; perhaps I shouldn't have bought a cheapie. I do better with a home-ground one shaped like yours, Ross, but in HSS with a bit of back rake. It will only go in 1/4" deep, but Πr2 means that on 1" round stock, that does 75% of the job, considerably reducing the hacksaw work.

On little lathes like yours and mine, sometimes it helps to go in 1/16"/1.5mm, withdraw, move the tool about 10 thou/0.25mm nearer the chuck, then go in to the same depth plus another 1/16", withdraw, move the tool back to where it started and repeat until you are finished. That way, much of the groove you are cutting is wider than the tool, reducing the tendency for chips to pile up and cause a jam.

It also saves expense on fuses to hover your left thumb over the red E-stop button so you can hit it quickly if the lathe stalls....

Andy.

Bert:

Hi Andy

If you find you get better results by moving your parting tool back and forth a bit it suggest 2 things that could be wrong. First you parting tool needs a bit of side relief. In other words you tool should be slightly narrower at the bootom of your tool than it is at the top. I if you have side relief, and still find it works better to move your too to the side then that suggests your your tool and tool holder are not 90 degrees to you work. Slide your tool post up to the chuck face and make sure they are parallel before you snug it down. In almost all cases the tool should intersect the work a 90 degrees. If your set up is correct parting completely off is the result. The ideal tool bit is the one that allows you to part completely off without disturbing your set up.
To improve results on the mini lathe it is desirable to make a carriage lock which makes the carriage immobile for parting operations. It is a very worthwile addition to the mini lathe and will
help considerably with parting .

Some parting info here

http://www.mini-lathe.com/Mini_lathe/Operation/Parting/parting.htm

Regards....Bert

AndyB:
Hi,

I would agree with all of the above, particularly Chris.

I run 2 Drummond M Types, a standard bed (for normal use) and a long bed (for special and thread turning...it has almost no wear) I have just acquired a Super 7 but I have not done all the experimentation with that one yet so don't use it much.

Don't go spending money to solve the problem, figure out why there is a problem.

I had problems when I first tried it with chatter being the first hurdle. It showed in the finish of the cut.
OK. Worked that one out. It was not flex so I had to try cutting height. Yep! Sorted that out with experimentation. Your cutting height is particular to your lathe!!!!! I have two identical lathes but the parting tool set up is individual for each! On the main lathe it does not cut to exactly centre but it is really clean so I don't mind the tidying up operation.

I grind the end of the tool at a slight angle so that the parting is next to the job.

Next. Problems with tools snapping on deep cuts. Worked that one out quicker. Tool not exactly square to cut so bending as depth increases. Ensure squareness of tool to work. Also, support the end of the job lightly if there is any overhang. One thing that snapped tools was the job bending when almost through.

Sorted!

I use HSS blades and off-hand ground HSS square. Take as long to set up as necessary if you don't keep a preset toolholder/toolpost.

It does need to know who is boss! Wind that feed through the part, the more constant the better; I use two hands on the wheel to get a more constant feed.

Hope this helps. It is difficult to suggest what to do without seeing your (or any) set up and watching the process through.

Good luck (and that is also something the old-timers talk about)

Andy

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