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Parting off help!

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DMB28/06/2021 15:41:27
1169 forum posts
1 photos

MGF, not done it yet,

1. I dont seem to have any trouble with my HSS stock but perhaps because most was purchased a long time ago and also none from fleabay.

2. I have found that skimming the face of a metal bar and height adjusting by trial and error, eliminates the pip, no problem. Once the tool is working OK, lock the height adjuster screw then toolholder can be removed and replaced, pre- set, no further fiddling about. They were designed for such method.

3. Flimsy tools never worked for me, as previously stated, I end up with one part convex the other concave. Now only use 3/32" thick parting tool with success.

4. Probably have enough HSS in diff. sections to see me out so not really bothered about current availability. Once gave insert tools a trial. Not impressed but maybe because of the silly prices for a common lathe tool, I bought cheapo and was rewarded accordingly. HSS reigns supreme, IMO.

Vic28/06/2021 16:04:16
2920 forum posts
8 photos
Posted by AdrianR on 28/06/2021 13:41:13:

I am completely sold on T shaped blades with a hollow top. Similar to the ones Eccentric Engineering sell, although I have a SOBA 1/2" from Chronos. The swarf is folded slightly which makes it narrower than the slot so less chance of jams. No worries about grinding the top rake, and the tool is held at 0 degrees so no height issues.

Yes Adrian, I agree. Mine were originally from Chronos but I had to buy my last blade from Axminster. They do indeed work very well and must have saved me quite a bit on the cost of carbide parting inserts.

Howard Lewis29/06/2021 12:11:24
5348 forum posts
13 photos

Interesting that others have had poor experiences with inserted carbide tips.

They cut very well, but a dig in can ruin both tip and holder.

The original Carbide tip parting tools sits on the shelf, unused, while the 3/32 HSS in the back toolpost is used every time. the blade is set on centreline, but the holder is designed to flex slightly. It never leaves a pip, although I always face the work after it has been parted off, to clean up and improve the finish...

Howard

not done it yet29/06/2021 13:23:45
6350 forum posts
20 photos

As Howard, for me too. My one and only insert parting blade got damaged, years ago, in a dig-in on my first lathe. A whole length of HSS blade cost peanuts compared to a couple of inserts (never-mind the holder!). Insert types are cheaper these days but the rear tool post with HSS blade (whatever grade it might be) just works, so “it ain’t broke, so I ain’t going to try to fix it”!

It usually leaves a pip on one piece (depends on how I dab it on the linisher belt, I suppose). If the pip is on the wrong side of the cut I just dab it again, with a bit more care!🙂

IanT29/06/2021 14:42:12
1899 forum posts
184 photos

I've only broken two parting tools inserts and both times it was on interrupted cuts (e.g. square material). Other than the tool thickness (about 3mm), which tends to waste work material, my (rear mounted) insert parting tool works very well for larger diameter material. You do have to hold your breath and just 'go' straight in with it though.

For odd-shaped materials or smaller work, I also have a number of different sized HSS blades (and holders) and they generally work OK too - but when using them for deeper cuts, I do use the sideways-step method to maintain tool side clearance. Makes for a much more relaxed parting operation.

Regards,

IanT

Chris Mate29/06/2021 17:34:07
14 forum posts

I have a HSS cutting blade with V on top, as well as an ISCAR parting blade/inserts. I grind the iscar insert a bit sharper that way it cuts metal well no shudder so I find I use this one the most, must say the inserts is tuff even sharpened.

I see it this way, hope I am right, if you position the cutter tip above centerline, above possible bent down forced, it will dig in and be forced pass the centre hight maybe pulsating, it may cut forced by positioning rather by you pressing , if you set it at centreline it worked great for me, if you set it below centerline it may rub as a brake and make a constant noise. An experienced machinist told me to set it a fraction below centreline. I also saw a youtuber doing real heavy work, say he do not use quick change toolposts due to flex, so he use the standard toolpost that comes with the lathe all the time, heavy cuts.

Actually I must measure the flex on/near tool tip to see what it is.

William Harvey 107/07/2021 21:10:16
151 forum posts

OK so after having some trouble today, I thought I'd ask for help with parting, then I saw this thread. The problem however is that being a complete newbie, I have no idea what is being suggested to help. So here's my issue.

I have a Warco WM180 with this tool set, in the set is a parting tool, which I have only used once before on a smaller diameter piece of bar.

I am trying to part a piece of 25mm bar and am having a lot of trouble. I checked the tip of the cutting blade was level with the centre of the piece and it was.

A lot of chattering and squeeling and the occasional large / short roll of swarf and at one point the tool jammed and stopped the lathe!!

Lathe is running at 600 RPM.

Here's a video of it trying to cut.

I don't have any cutting fluid so was using 3 in 1 oil, what cutting fluid should I get?

Some help needed

Emgee07/07/2021 22:55:57
2161 forum posts
265 photos

William

For more rigidity it is best to part off closer to the chuck.
Sounds as if your tool is rubbing, do you have enough front clearance. ?

I have experienced a similar noise and the surface looked like a straight knurled surface, after dropping the speed down to 200rpm all was well, the tool cutting as it should without any chattering.
I was using a neat cutting oil.

Emgee

Chris Crew07/07/2021 23:40:21
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135 forum posts

We have been through all the issues on parting-off so many times. On numerous occasions I have parted-off 5" & 6" noggins of mild steel in a Colchester Student to make back-plates for the Myford with no trouble whatsoever (if only because I had a lot of heavy steel bar to hand). On 'normal' size work I just part-off as a matter of course. And the 'secret', if indeed it is a secret for deep parting cuts is this: Use a sharp inverted tool in a rear tool-post and pump coolant into the cut because dabbing it on or the odd squirt is pointless I.M. (humble) O. I suppose because it keeps the tool cool, lubricates the sides of the cut and swills out the swarf. Keep a steady cut going once the 'plastic flow' starts. If it squeals your starting speed is too high, but don't be afraid to increase the speed as a deep cut progresses, say at steps of a third of the diameter. Aim for a nice 'hiss' as in all successful turning. Keep the cut as close to the chuck as is practicable making sure the work is securely held.

If you still have trouble, read what George Thomas had to say on trouble-shooting parting-off issues, but don't waste your time making his rear tool-post, I did and found it to be flimsy and useless, but that's just me. Rear tool-posts with parting tools securely fitted 'live' on my lathes. Forgive me, but I sometimes fail to understand why so many people seem to have so many problems with parting-off which to me is a straight forward basic lathe operation, probably the second operation we learnt to do after reducing a diameter in the apprentice training school I attended in the 1960's when we were introduced to turning and we didn't have rear tool-posts on the lathes back then.

OK, upon consideration, I am being a bit 'sharp' and forgetting that I have a fair amount of experience which makes things easy and almost 'second nature' whereas 'newbie's' have no background to fall back on. I apologise for that and merely offer my advice in the hope that it will help somebody somewhere to overcome their difficulties and add to their education.

Edited By Chris Crew on 07/07/2021 23:53:01

William Harvey 108/07/2021 07:30:25
151 forum posts
Posted by Chris Crew on 07/07/2021 23:40:21:

We have been through all the issues on parting-off so many times. On numerous occasions I have parted-off 5" & 6" noggins of mild steel in a Colchester Student to make back-plates for the Myford with no trouble whatsoever (if only because I had a lot of heavy steel bar to hand). On 'normal' size work I just part-off as a matter of course. And the 'secret', if indeed it is a secret for deep parting cuts is this: Use a sharp inverted tool in a rear tool-post and pump coolant into the cut because dabbing it on or the odd squirt is pointless I.M. (humble) O. I suppose because it keeps the tool cool, lubricates the sides of the cut and swills out the swarf. Keep a steady cut going once the 'plastic flow' starts. If it squeals your starting speed is too high, but don't be afraid to increase the speed as a deep cut progresses, say at steps of a third of the diameter. Aim for a nice 'hiss' as in all successful turning. Keep the cut as close to the chuck as is practicable making sure the work is securely held.

If you still have trouble, read what George Thomas had to say on trouble-shooting parting-off issues, but don't waste your time making his rear tool-post, I did and found it to be flimsy and useless, but that's just me. Rear tool-posts with parting tools securely fitted 'live' on my lathes. Forgive me, but I sometimes fail to understand why so many people seem to have so many problems with parting-off which to me is a straight forward basic lathe operation, probably the second operation we learnt to do after reducing a diameter in the apprentice training school I attended in the 1960's when we were introduced to turning and we didn't have rear tool-posts on the lathes back then.

OK, upon consideration, I am being a bit 'sharp' and forgetting that I have a fair amount of experience which makes things easy and almost 'second nature' whereas 'newbie's' have no background to fall back on. I apologise for that and merely offer my advice in the hope that it will help somebody somewhere to overcome their difficulties and add to their education.

Edited By Chris Crew on 07/07/2021 23:53:01

Excellent advice, thank you. A rear tool post for a Warco WM 180 Hobby Lathe, does such a thing exist?

Martin Connelly08/07/2021 08:34:01
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1901 forum posts
205 photos

No pussyfooting. Go at it. This is where experience helps. Chris above says he has lots of experience and no problems. So he probably either feeds by hand and knows how fast to go or uses power feed and knows what settings work. The earlier posts tell you about 0.1mm to 0.15mm per rev or about 0.004" to 0.006" per rev for inch based machines. Once you start to rub and not cut because you are not feeding fast and consistently you will blunt the edge of a HSS tool. This is easier on a machine with back gearing to slow the spindle and increase the torque because the tool is wide and can slow the spindle and even, as you have found, stall it if spindle torque is low. If the spindle starts to slow back off a bit to allow it to speed up again and not rub to tool. Then go back in at a reasonable rate.

Secondly part off as near the headstock as possible. If using a chuck as in your video the parting point should be as close as possible to the jaws, your example is some way away from the chuck. If you have to part off away from the headstock the much recommended rear tool post helps because its reaction forces push the workpiece and chuck down against the bearings where gravity has already seated the mass. The front cutting tool tries to lift everything and the long leverage away from the headstock helps this to occur. If you have a suitable steady you can fit near the parting off point this may help.

The parting off tool needs to be as short as possible and only stick out as far as is necessary to avoid sideways deflection.

If you have a top compound slide wind it back to reduce overhang as well. Try to ensure the cutting point is over a solid support and the top compound is not sticking out unsupported. This is important on smaller machines.

The clearance rake below the tool is very important when parting, more important than the top rake, since poor clearance will keep the cutting edge away from the workpiece and any wear of the cutting edge will do the same.

I've never tried 3 in 1 oil as a cutting oil so can't pass judgement on how well it works. I think it will be okay as I use RTD tapping and drilling oil when parting since it clings on to the metal better than watered down "soluble" cutting oil.

Get some plastic rod to practice on if you want to gain experience of feeding correctly without the issues of tool jamming or spindle stalling, progress to something easier like brass rod (expect flying bits of brass not curls) then practice on steel. You really don't want your first parting or grooving job to be on a real piece of work. There have been plenty of posts by people who have suddenly found they can part off once they have experience and confidence to feed in correctly.

Consistency from power feeding gives consistently good results, this is from parting off stainless steel.

img_20160714_181532.jpg

Martin C

 

Edited By Martin Connelly on 08/07/2021 08:35:31

Howard Lewis08/07/2021 18:17:55
5348 forum posts
13 photos

AS martin says, keep everything as short as as rigid as possible, and keep a steady gentle feed, don't let the tool rub!

I use no top rake at all, so the tool goes into the work on the centre line, but has clearance at the front and sides..

Being in a rear toolpost, has the advantage of the swarf falling away so that it is less likely to clog in the cut.

Is HSS good value? This one, sceondhand, has been in use for over twenty years and is still only just under half the length of when I received it.

No rear toolpost?

Make one! I did, as have many others. In fairness, mine is a match for the front 4 way post, so is bigger, heavier and more complicated than usual. BUT it does the job. I am now so brave as to part off under power!

Even if it is a one tool post, make it heavy and rigid (Akin to the Gibraltar front toolpost )

If a toolpost is overly rigid, the only problem that you may have is space. It is not sufficiently rigid, you will have a variety of problems, most of them bad!

Howard.

William Harvey 108/07/2021 20:50:04
151 forum posts

So today I checked:

1. That the cutting tip of the tool was at centre height, by lining up with the tip of a dead centre - done.

2. That the cutting tool was at 90 degrees to the material being cut , by squaring up the tool to the chuck face - done.

3. That the parting tool was as close to the chuck as possible - done.

4. Locked the cross slide.

I tried several different speed, adjusting between 150 RPM - 400 RPM.

Manual feed and dabbing with oil.

The noise is better (more ridgid setup), but the tool is just rubbing and not cutting.

This is a carbide tip Parting Tool so maybe I just ruined it and now it won't cut.

I have a basic clarke bench grinder with a couple of stock (the ones that came with it) grinding wheels, but probably need to now get some HSS parting tools. Can anyone point any out for me, so I get the correct ones.

It seems there is not rear tool post available for this cutter, so a guide on how to make one would be useful?

I have a bit of brass - and maybe some plastic and I'll try and have a practice in the meantime.

I'd really like to crack this nut

Emgee08/07/2021 21:37:02
2161 forum posts
265 photos

If you have a green grit wheel you can cut some relief into the front of the carbide tool, to start with aim for about 7 degrees for general use.

To confirm you have the tool at centre height take a skim off the face of a bar, there shouldn't be any pip but make sure that's not because the tool is above centre.

Emgee

William Harvey 109/07/2021 10:57:36
151 forum posts
Posted by Emgee on 08/07/2021 21:37:02:

If you have a green grit wheel you can cut some relief into the front of the carbide tool, to start with aim for about 7 degrees for general use.

To confirm you have the tool at centre height take a skim off the face of a bar, there shouldn't be any pip but make sure that's not because the tool is above centre.

Emgee

I only have a Clarke 6" Bench Grinder with the Wheels it came with.

Local tool shops are now few and far between and don't sell Green Grinding Wheels.

I guess I should order a decent Green Grit Grinding Wheel for this grinder, as this will get a lot of use grinding all the various tool bits. Should I get 120 Grit. What about small sharpening stones?

William Harvey 109/07/2021 11:22:29
151 forum posts

So I have been watching the BlondiHacks tutorial on parting and have read through this thread. I am considering some HSS Parting Tools. I have this QCTP set, which comes with a 250-007 Parting Tool Holder.

The only info I can find on the tool bit is here which suggests a 1/2" parting blade.

The BlondiHacks video I have been watching, recommends a 'T' profiled parting blade, but they don't seem to be available in the UK, so I will be looking for a 'V' shaped tool.

For the 250-007 Tool Holder will the 060-060-04105 (1.5mm x 13mm x 85mm) as sold by ARC Eurotrade be the correct fit? But these looked to be non profiled.

What about these, also from ARC Eurotrade, the 13mm ones?

William Harvey 109/07/2021 11:58:44
151 forum posts

Just read this thread on grinding wheels. And here is a what I believe is a suitable green grinding wheel, with reducing bushes and a dressing tool. Will the green discs be suitable for HSS as well? Or will I need two grinding wheels?

JasonB09/07/2021 12:10:03
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Moderator
21467 forum posts
2455 photos
1 articles

Chronos do the Tee shaped blades in 1/2" height here

If you can fit 13mm in then the second ARC link for the tapered blades will do.

You only need the green grit for carbide just use the supplied grey wheels for HSS and HSSCo

Edited By JasonB on 09/07/2021 12:12:09

SillyOldDuffer09/07/2021 14:28:59
Moderator
7574 forum posts
1681 photos

Parting off is difficult because everything matters. It's much harder to part-off on small lathes than big ones, so expect a WM-180 to struggle a bit.

In no particular order, my list of trouble makers, most of which multiply the chance of failure:

  • Lack of rigidity is probably the single biggest cause. Gibs have to be well-adjusted, overhangs minimised, saddle locked, work supported and the cut taken without anything moving.
  • Difficult material
  • Wrong speed
  • feed rate too fast or too slow.
  • Blunt cutter (which soon happens if the cutter is allowed to rub.)
  • Cutter over the centre line or much too low (which isn't far)
  • Cutter not at 90° Note that although it may be square before cutting starts, it won't be if any part of the lathe moves when pressure is applied. Even tiny movements cause grief.
  • cross and top-slides are quite bendy, and more so if the tool is in a QTCP. Parting off from the front tends to lift the saddle at rear right. Therefore it's best to part off with a rear-mounted tool-post of the Gibraltar type. This is a hefty solid block of metal bolted firmly to the saddle, and, if the lathe is run in reverse, cutting forces are transferred straight down to the bed, rather than twisting the tool, tool-post, compound slide and saddle on the way.
  • Swarf jambing the slot.
  • Inadequate or intermittent flow of cutting oil. (Use CT90 or similar.)
  • Varying feed rate - must be steady. Wobbly fits and starts are punished! My lathe has power traverse and - so far - has never failed to part-off in that mode. Sadly,. about about 1 in 3 manual partings go wrong, despite same setup. Failures are due to me failing to feed steadily. Yes it's true, I'm a wobbly machinist.

Tempting to rush about trying different shaped cutters, and I'm sure some work better than others, but the real problem is everything about parting off is a bit critical. Any of several things can go wrong and they all need to be nailed down. I was able to part Brass on my mini-lathe, but Aluminium was prone to stick and steel required too much pressure for the lathe's tiddly tool-post. Parting off on a mini-lathe isn't impossible, and no doubt I would have improved with practice, but it was less bother to accept the situation and saw off. In comparison parting off under power with a WM-280 is a doddle, even without the rear tool-post. Main reasons are the big lathe's extra rigidity and it's ability to maintain constant cutting pressure.

Dave

 

Edited By SillyOldDuffer on 09/07/2021 14:29:33

William Harvey 102/09/2021 18:34:33
151 forum posts

Iv'e been really busy over the summer and had lots of in impromptu visits to deal with, so not a lot of time in the workshop.

I bought a tapered HSS Parting Blade from ARC (this one) which fits in my 250-007 Tool Holder. I placed a slither of tin can behind it to ensure it sits vertical.

QCTP Now, I could try this in my QCTP but, my QCTP does not fit particularly well (the stud is not really long enough), can I buy a longer one?

Reverse Parting I have seen in this thread about running the lathe in reverse, unless you have a Screw on Chuck. I cannot find whether the Warco WM180 has such a chuck?

If running the lathe in reverse how do you invert the tool?

Rear Mounted Tool Post This appears to be the preferred option, but for the Warco WM180 what would be the most cost effective solution.

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