T type cut-off tools

From the EE website:

"For lathes with a screw on chuck the parting tool must be used in a rear tool post with the lathe running in the normal direction."

Gentlemen,
I was cautious enough to be open to other views. I have lathes which work really on the first three shears(. and presume John 's is the same) and how other lathes perform for thrust forces is open to comment.
I did fit the inverted rear parting tool onto the SiegC4 and found that it worked and having satisfied myself- satisfied myself and got on with life.

However, I do pose the question( again) as to what lathe that you witnessed his Tee parting tool was fitted. From what I have seen in his excellent videos on his tool and cutter grinder, he was using a much more solid lathe than my two Myfords.
I, have met Gary and his sister at a show but it was plainly too packed for much of a conversation. However, I am aware that his Turnado design is for both the Myford and the Sieg- but understandably, I cannot comment except to note that neither of then were at the last Doncaster Show to ask questions because his tool and cutter grinder is is kitted out to accommodate conventional hss parting tools. I have his plan book and an unfinished kit.
Whether is grinder will refresh internal vees in carbide is one of my unanswered questions.

So, having a high regard for him, I must remain in the 'Don't Know' category.
Consequently, I don't know what progress has been made in additions on his grinder

What I do know is having page after page of comment on the solving of the perils of parting off with hss tools.

Laughingly, the Sieg will not as bought, power feed an inverted rear parting tool.= and I have been holding on to a collection of parting tools- because mine fitted has refused to wear out like other formats.

Most interesting comments though and Thank You for them

Norman

I think Shakespear had it right when he said "Parting is such sweet sorrow!" He must have been a model maker.

This happened some while ago on a reasonably solid lathe of 12 inch throw and I'm still shy of using it to this day. I didn't think that a commercial grade parting tool could do this especially with the "V" groove carbide tips.
The bang was enormous and totally unexpected. I can see now why they provide the holder with two ends!

Hi Guys,

BaronJ aren't the forces the same with a rear mounted tool holder using the parting tool upside down and running the chuck in the normal direction? You don't have to worry about the chuck unscrewing but the tool body is still above the centre line and is still lifting the saddle.

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From the chuck's point of view, yes !
But you have to take account of using the rear tool post moves the top slide forward causing it to engage more with the dovetails increasing rigidity and stability, particularly with a longer top slide on smaller lathes.

But if it works for you

Hi John,

Thanks for your picture, I've seen the same or similar tool, that had gone bang like that as used on a 12 inch Colchester CNC auto parting a stainless steel bar, under power. Those big lathes simply don't stop if something bad happens.

Just about every one of the millions of capstan lathes ever made uses inverted parting tool in rear tool post. Never a problem. If you are worried about carriage lifting, apply carriage locking clamp. Standard operating procedure on Myfords and Drummonds for over 100 years now.

BaronJ said:

But you have to take account of using the rear tool post moves the top slide forward causing it to engage more with the dovetails increasing rigidity and stability...

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I’m not following you John. Can you elaborate?

Hopper said:

Just about every one of the millions of capstan lathes ever made uses inverted parting tool in rear tool post. Never a problem.

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I don’t think anyone is suggesting rear mounted inverted parting tools don’t work. The question is whether they work better than a front mounted inverted parting tool, and if so, why ( assuming you don’t have a screw on chuck)?

In the US, Little Machine Shop has Arthur R Warner Co blades. These are great blades and make parting a joy (my South Bend 13" and 9", plus the Enco 12"). However, Little Machine Shop's holder is Chinese which is un-usable until you replace the bolts and remachine to fit the blade!

https://littlemachineshop.com/products/product_view.php?ProductID=1728&category=

https://littlemachineshop.com/products/product_view.php?ProductID=1551&category=

(I was trying to figure out why Anthony of Eccentric Engineer, 'EE', was selling parting blades! https://www.eccentricengineer.com/)

I see the other EE is an Oz thing...

Hi
I think the root cause of many problems with parting is flank wear on HSS cutting blade. This tends to taper the flanks so looking from above, the tool is narrower at the cutting edge end. As the tool gets deeper into the work piece, the friction increases until disaster strikes.

The solution is to grind the flanks to reverse the taper. This makes the tool widest at the cutting end. As the flanks wear near the cutting edge, the tool needs to be shortened up.

The other option is to use carbide tooling. Much easier.

Dazz

Another issue is heat so plenty of cutting oil helps a lot .
After watching a video on YouTube (winky’s workshop ) i decided to do a test of some different cutting fluids and came to the conclusion that front or rear mounted ,normal or inverted tools mad little difference and event the supported type as described in the video by winky still didn’t stop dig ins but it did make them more violent .
I tried carbide insert , brazed carbide and hss - all still had dig ins and i ended up destroying two insert holders !
Cutting fluids were tap magic , soluable oil both raw and mixed with water , wd40 , rp7 , trefolex ctd spray and the old smelly trefolex past ( i detest the smell of this stuff ) and lanotec spray .
Test piece was 50mm ( 2”) black steel round bar and speeds were varied to eliminate chatter as needed.
Every thing was applied with a brush at first then by drip feed on the second round except the paste which failed the first test miserably anyhow .
The list below are graded best to worse top to bottom ,
Wd40 - applied liberally by drip feed this stuff outshone everything else and the waste can be recycled if you put a drip tray under the cutting tool .
Ctd spray used as worked well but is expensive and a bit messy and can’t be re used .
Tap magic seemed the same as ctd .
Soluable oil mixed with water works but is messy and you have the corrosion issues if you don’t dry the bed off.
Neat soluable oil came next and is even messier than above .
Lanotec is not designed for this neither is trefolex paste .
Rp7 - this was really weird ! I started a cut with wd40 and thought i would give the rp7 a go and the tool seized in the groove immediately and i mean IMMEDIATELY! I tried agian using only rp7 and it just wasn’t going to happen , I don’t know what is in this stuff but I couldn’t get a result using it .
One standout with parting tools was a brazed carbide tool that was ground so the tip was wider than the flanks if you look down from the top and even though it was 3mm wide i ploughed its way through the bar with no issues .
Insert tooling also worked ok but cheap tips go blunt quickly and if you get a dig in chances are the blade will be toast !
The hss bits i tried were the std wedge ground shape and the t blade from eccentric engineering , i found the t blade to work better and even though i still got some serious dig ins it didn’t break , bend or chip . One thing i did notice with hss blades is the importance of having a good holder , the holder for the t blade supplied by eccentric engineering has been machined so it fits the contour of the blade and holds very firmly , i purchased a holder for the wedge blade from a local supplier that was machined to accept the taper on the blade and this also worked well ( many cheap holders allow the blade to cock as they tighten as there is no contact between the side of the blade and the holder . I also tried the style as shown earlier in this post ( has the sliding block that is pulled down the groove with a long screw ) this was useless as it only gripped the blade right at the front and not along its length so found the rear of the blade kept walking out as i performed the cut .
I will be using a pressure spray bottle modified to supply a contant drip feed to a nozzle stuck to the toolpost with a magnet to supply wd40 to where i m parting off - just got to get my a*se into gear and make it !

Ah Yes! I too have experienced what was called' The Big Bang' and whilst I only broke a thin Eclipse hss tapered blade, others such as the late Kenneth C Hart and author of Screwcutting in the Lathe book, had such a bang that it tore the slots out of his bing table
Years aago, I was given to see what I might do with it, a Myford Super7 top slide where the fixing spigot to the boring table was torn in half and whatever happened elsewhere on that particular lathe, I simply don't know. What Cleeve did, and it can be seen in his book, he had Myfords make up a steel boring table with only tee slots.
I bought a Super7 with gear box very cheaply which had experienced the Big Bang and which tore three of the gears in the box into scrap. OK, I cut a new gear and ran the machine with a Geo Thomas inverted rear parting tool with interesting things.
The bed and the underneath of the saddle were so worn that the cutting tool deflected inn and out of cut whereas the previous owner must have used a from parting tool which 'went into cut' rather that 'out of cut' and the Big Bang benefitted me as I was capable of organising a very extensive but inexpensive overhaul which included a slideways grind and Turciting the underneath of the very worn saddle.
So apart from a desperate need of painting, and improving/changing needle roller bearings it is almost back to factory performance.
Incidentally, I use purified lard oil. It smells a bit like MacDonald's when I get a bit excited but what is left of my ancient hands gets -what probably goes into ladies hand creams.
And Dig In's are only a fading memory.

Norman

Two oft-cited advantages of an inverted parting tool are:
1. Swarf falls out of the groove under gravity so does not get jammed between the sides of the parting tool and the job so readily.
2. Forces on the headstock spindle bearings are downwards, thus against the solid body of the headstock and not upwards against the more flexible and bolted-on bearing caps. (Or upwards against the headstock mounting bolts on Chinese lathes etc.)

My King 10” lathe has a screw on chuck but also has two “keepers” that bolt to the spindle driver and keep the chuck from unscrewing. It seems that this arrangement would be safe for a front mounted inverted parting tool running the chuck backwards. I emailed Eccentric Engineering to ask about this but no response so far.

You don’t have to use the tool inverted but if you must do it with a screw on chuck a rear mount toolpost would be best, that way you can run the tool inverted with the lathe spindle rotating as you would while turning .
I forgot to mention in my last post that the compound slide arrangement can also cause dig ins as it adds to the amount of flex in the machine . I was considering making a custom cross slide for parting off - a bit like what you might find on a capstan lathe

jack620 said:

That's what I'm thinking. I can't see the difference. If you watch the EE video he parts off an 8mm high-tensile bolt in a Sieg mini lathe without any issue. Having met Gary and visited his factory I'm very confident he wouldn't sell something that didn't work as advertised.

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After watching the video, I was convinced enough to order the cutoff tool and holder from EE.

Shopgeezer said:

In my last order to KBC I included a T style cut-off tool, since I have wanted to try one. The tool that arrived with the order was a standard parallel sided tool. No T shape. After a few phone calls the nice rep at KBC informed me that I had the right tool, that was what they sold as a T type cut—off tool..

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Back to your original question...I've ordered the exact tool you are talking about from KBC. They call them 'cut off tools' in the index btw. Page 158 of the catalog shows both kinds, the tapered and T section. Here are the links to the e-catalog

T-shaped cut-off blade
https://www.kbctools.ca/itemdetail/1-503-201

Cut-Off blade (ie. the this is the tapered profile)
https://www.kbctools.ca/itemdetail/1-503-101

It does not have to be carbide tipped to be T, that's just another flavor. The T shaped HSS M-2 or 5% carbide are ground that way from solid bar with side relief to yield the section shape. If you get the KBC folks to look at their catalog & use these PN's as an example, I'm sure they will figure it out. I also wouldnt be the first time something was packaged incorrectly, sometimes further up the supply chain before they grab it off the shelf. But I don't think there should be any ambiguity on this matter.