Parting off and general HSS tool sharpness

[Ross]

Hello everyone.

I did a bit of turning on the lathe today just to test the various tools etc..

I centre drilled and drilled a hole (all technical stuff)   

And I turned part of the rod down to 10mm diameter. The standard cutting tool I used cut through the aluminium like butter as it should!

I put a little groove in the rod too, but the real trouble came to when I wanted to part off the piece I'd just done.

The metal wasn't having any of it and the tool was just making nasty marks and squeeking. Before. I snapped or broke something I gave up as parting off was like cutting through butter at college.

I'm not convinced that my parting off tool is sharp, I can run my finger all over it and it just doesn't feel sharp hence the nice marks it has left in my masterpiece!

What's the best technique to sharpen these tools if any?

And some pictures to show:

[-steves-]

Hi ya Ross

This is where you could do with the little diamond covered wheel that David (Stilldrillin) showed you, as the tools you have there (same as my first ones) as as blunt as anything I would suggest sharpening them as a first point of call and then see how it goes from there. Does it do the same on brass? After sharpening if its still no better, then check the rigidity (however its spelt?) of the tool, tool post, top slide, cross slide etc. Parting off on small machines takes a bit of a knack and a lot of setting up, sharp tools etc. I will freely admit, I put a small groove in now and then turn to the hacksaw to finish the cut, particularly on steel, though brass below half inch diameter isn't an issue.

I am sure the more experienced will give you better pointers

Best of luck

P.S. I don't think that is HSS in the picture..... I find that a sharp HSS tool will cut very well, but do go blunt quite quickly, again, particularly on steel. A really sharp tool is a god send 

[DMIOM]

hi Ross - it might also be worth checking that the tool height was correct

(p.s. belated welcome to the mad mob!)

Dave

[picclock]

Hi Ross

If that's aluminium then it should be very easy. First check that the tool height is correct by trapping a thin piece of metal (razor blade or similar ?) between the tip of the tool and the work. If the height is correct the thin piece will be exactly vertical. Sharpen the end of the parting tool with a stone or grinding wheel to give it a good edge. Fit the tool so that the overhang from the toolpost is just over the work radius size. Ensure that the tool is at right angles to the ways. Lock the carriage to the bed and ensure that the gibs are tight. Using a slow speed, say 150 rpm, feed the tool into the work. If the tool chatters it may be that the gibs on the compound slide are not tight or that the rigidity of the toolholder is poor. If the cut looks like its going to be OK douse the work with wd40 or paraffin and slowly advance the tool until done.

Most parting problems come down to rigidity of the setup and the correct tool height. I found that parting was much improved by removing the compound and replacing it with a steel block. Also I replaced the headstock bearings with taper roller ones which gave an improvement.

Good Luck

Best Regards

picclock

[Bernd]

I'll add my 2 cents worth here. First that looks more like a carbide grooving tool than a cutoff tool, and as mentioned else were it isn't sharp. I would try a HSS cutoff tool if you have a small bench lathe such as a 9 X 20 or smaller. It's not rigid enough to cut with a carbide tool.

Bernd

[Fergus OMore]

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[Ross]

Thanks guys, by the sounds of it parting isn't that suitable for lathes as small as mine? But I'll adjust the gibs again anyway.

Besides, I can always hacksaw through then face to length.


I have a 7x14 Mn lathe.

[Fergus OMore]

deleted

[Bert]

Hi Ross

 Your little lathe is just fine for parting. The variable speed will help a lot.Your little beast is a great introduction to machine tools and a year from now you will be surprised at what you and that little lathe are capable of . You just have a lot to learn that’s all.
The internet is full of good information regarding your little lathe. Search, read and absorb.
You have received good advice so far.
In real estate the axiom is    Location, Location, and Location.
In Parting it is ridged, ridged, ridged, sharp, sharp, and sharp.
“Read the chips.” is a term you will hear often and it is a skill you will develop over time. You will learn to hear what your lathe is telling you.
One thing that has not been touched on so far is the rate at which you feed in on the tool.
 When you have a sharp tool, set at the correct height ,the aggressiveness with which can, and should feed may surprise you. Once you begin to cut and form nice chips you most likely can advance the tool at a faster than you may think.     
Good luck and welcome to a great hobby.

[Pete.]

Hi Ross.

Looking at the pic of your tool you have a shiny mark on the front which suggests the tool height was too high or that there is no front relief. Too high I would say.

For parting, I cut pieces out of a tungsten-tipped sawblade and mount them in my parting tool holder. If you have access to brazing or silver soldering you could easily make something similar for a 4-way toolpost.

[jim]

i gave up trying to part off until i tried a rear tool post!

[DaveH]

Ross,

Parting off  is one of these perennial things.

Ask 10 guys "How to part off" and you will get 20 different answers.  So what is one to do, - keep trying (when you feel like it) eventually you'll hit on a way that will suit you and your particular set of circumstances.

In the meanwhile just cut it off with a hack saw.

Enjoy it and have fun 
 

DaveH

[John Swift]

Hi Ross ,

the parting tooling your photo is only is roughly shaped and needs sharpening
as it is it has a zero top rake that's OK for brass but needs to be reground for steel or aluminium
to give you a positive rake , also it looks a little too wide

while  at school in the 70's , parting off tools usually broke before I could  cut  one part off

years later while making some electrical repairs to an EMI-MEC "plug board" automatic capstan lathe
watching them part off every few minutes , I realised why I broke so many parting off tools on the  Myford lathes

first  a 2.5 to 3 mm wide parting tool is too wide !! for small  lathes - they are under powered and not ridged enough
you need to part off as close to the chuck as possible .

once you start you need to keep going , the feed rate needs to be constant , no stopping halfway through


I've recently re learned the art on a smaller version of your lathe ( machine mart CL300M)
first time I tried ,the tool deflected downwards, as it metal bar climbed onto the tool-,,,,,crunch !!
you could see the toolpost move ,due to  the play in the slides !!

I replaced the gibbs on the top slides with brass ones from to reduce the play ,the originals didn't fit too well ,

( with no milling machine I took the easy way out and bought them from Arc Euro Trade )

I reground the parting off tool so its  now about 2 mm wide and the top rake about 3 degrees ( angle needs to suit the material)
the tool will get thinner as the cutting edge is  resharpened
 
my second attempt with the correctly  fitting gibs was successfull 

as other have said its very important the tool is at the correct height

one problem with aluminium is it friction welds its self to the tool

with practice , you will know by the sound from the tool when its cutting correctly

John

[SKIPRAT]

Ross

What a can of worms to open up on Christmas Eve "Parting Off" there are many theories on the "Black Art" concerning parting off you will however if you persevere get it right and look back on the problems you had and say it was not that difficult.I will first outline a few requirements for successfull parting off   1/ machine rigidity such as Gib's correctly adjusted spindle bearings ,mass of machine 2/horsepower available 3/ tool sharp and on centre 4/correct speed and constant feed of tool into material 5/ adopt a technique that suits you and your machine 6/ make sure the saddle is locked or restrained. the tool needs to be as narrow as possible as it takes a lot more force to push a wider tool into the material and on a smaller lathe you only have a limited amount of horsepower.also do not have the material too far out of the chuck rule of thumb no more than 3 diameters you will get the hang of it in the end .

Cheers Paul

[S. Heslop]

Ross,

Parting off  is one of these perennial things.

Ask 10 guys "How to part off" and you will get 20 different answers.  So what is one to do, - keep trying (when you feel like it) eventually you'll hit on a way that will suit you and your particular set of circumstances.

In the meanwhile just cut it off with a hack saw.

Enjoy it and have fun 
 

DaveH

This is great advice.

I wish I just started grinding any old tool bits from the get-go, instead of spending far too long reading about it in books and online. All the experts online scared me to death, with anecdotes and facts on how if I was just a degree off in my rake angle, I was almost certain to gouge the tool into the metal and blow my motor. It didn't help that the values they'd then give almost always conflicted with everyone else's.


Oh also is your lathe set in forwards and not reverse? It's kinda embarrasing to admit, but when I first tried grinding parting bits I ruined two good blanks before realising I'd somehow set my lathe in reverse.

[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

[Pete.]

 Ilike the drummond toolpost, it's perfect for a small lathe. Must be one of the earliest 'quick-change' toolposts fitted on a lathe I think. I made quite a few adapters for my dad's 'm'

[AndyB]

Hi Pete,

What is not to like about Drummonds?

I have set up rear toolposts and find that parting with those to be much easier, but for those who struggle, try your standard set up until you figure out the pitfalls, then your investment in time/money in a rear toolpost will work first time. Another bonus, the chips fall out so don't clog the cut.

Andy

[Stilldrillin]

Hi Ross.
Late again! Sorry.......

What a crackin' thread. Umpteen replies, almost all different......... None of 'em wrong! 

I've just parcelled up, one of my slightly redundant, blade type tools for you to practice with. Will post tomorrow. 

Give it a go.
When you understand each other, you'll probably want buy something a little different...... Or not! 

Enjoy!

David D

[Ross]

 

I got Davids parting tool in the post and set it up down the shed. I put the tool slightly lower than center like you guys said and it cut through the aluminum like butter!

Thanks everyone for the help and David for the tool.

Below are some pictures of the two tools compare and the parted off bit of aluminum.





Ross

[Stilldrillin]

Well done Young Man! 

Learning the techniques, one at a time......... 

David D