Tool height: Glanze parting tool in Myford S7

[gabrielbParticipant @gabrielb]

I need to buy a parting tool for use on my recently purchased Myford S7.

Having done a bit of research I’m likely to go for a Glanze clamp-type 2mm insert parting clamp and blade, but my question relates to tool/cutting height.

The Glanze parting blade clamp comes in various size options, and the two I’m considering are the 8mm and the 10mm. My thoughts are the 10mm will obviously be more rigid, but will the larger clamp mean the cutting surface will be too high relative to centre? The lathe has a two position QC tool post, so has a degree of vertical adjustment as is normal on the QC tool holders.

Or should I just go for the 8mm clamp? I’m unlikely to work the lathe to the limit of it’s capacity, but I’m happy to buy a decent tool from the outset to enable expansion of my skill set as I get more experience.

Grateful for any thoughts or advice. Thank you.

[bernard towersParticipant @bernardtowers37738]

Myfords used to do a toolholder with a reduced portion underneath the dovetail part which allowed greater height adjustment when using larger tools. I have done this to 2 of mine as I couldn’t seem to find any at the time. they were done on a shaper.

[SteviegtrParticipant @steviegtr]

Hi Gabriel.

I have the S7 & tried various parting tools on the QC toolpost. You have to be very careful as the Myfords have a bronze headstock bearing. Not a roller or ball bearing setup. After having little success I made a rear parting holder to take various sizes of blade & height. Not sure if you may want to look at the builds but here is the youtube link just in case. There are 4 parts to the making of the holder & different size adaptors.

Steve.

[Andrew CrowParticipant @andrewcrow91475]

Hi Gabriel, I would use the largest tool shank you can, if it’s a fraction to high you can always machine a fraction of the bottom.

However, I would recommend a rear tool post for parting as Steve mentioned above. The George Thomas design from Hemingway’s is a good choice.

If you don’t want to make one, you could try to obtain a Myford one, they would take a tool shank up to about 16mm.

Andy.

[Andrew Crow]

On Andrew Crow Said:

Hi Gabriel, I would use the largest tool shank you can, if it’s a fraction to high you can always machine a fraction of the bottom.

However, I would recommend a rear tool post for parting as Steve mentioned above. The George Thomas design from Hemingway’s is a good choice.

If you don’t want to make one, you could try to obtain a Myford one, they would take a tool shank up to about 16mm.

Andy.

I’ll second the use of a rear mounted tool post. I struggled to part off on my S7 but since i purchased the Myford type  on ebay i have never had any problem parting since. The one I got of ebay was this type 256723904784 and I fitted it with link

https://www.eccentricengineering.com.au/products/for-front-or-rear-inverted-parting-tool

H

[gabrielbParticipant @gabrielb]

Many thanks for all your replies and advice.

One last question, if I buy a parting tool of the type I earlier described (parting blade in a clamp, such as Glanze or similar) can I use it in the front tool post right way up and also a rear tool post upside down, assuming I can get the cutting edge at centre height?

Or does such as thing not exist?

I’m just trying to buy one tool to start with, but if it has flexibility for the future so much the better.

 

[gabrielb]

On gabrielb Said:

Many thanks for all your replies and advice.

One last question, if I buy a parting tool of the type I earlier described (parting blade in a clamp, such as Glanze or similar) can I use it in the front tool post right way up and also a rear tool post upside down, assuming I can get the cutting edge at centre height?

Or does such as thing not exist?

I’m just trying to buy one tool to start with, but if it has flexibility for the future so much the better.

The short answer is yes you can.

Andy.

 

[John HaineParticipant @johnhaine32865]

Parting off for me was revolutionised by two things.  First, buying an inserted-tip parting tool.  At the time these were quite expensive but good ones are now quite reasonable from Arc (e.g.) like this one.  It is available with different shank thicknesses – mine is 12mm and fits a standard Dickson QC holder.  I use it in the front toolpost without problems.

The other thing was reading George Thomas who tells you to part at higher speed if at all possible and use self-act crossfeed. On my S7 big-bore speed was 215rpm and slowest self-act.  The first time I engaged the feed I was sure that was going to be a frightful bang and something would break, but actually it was a non-event, just a clean cut and a pile of curly chips.

The worst thing to do IMHO is to use manual feed and slow back gear.  When you first try it you are frightened by all the horror stories so your hand is unsteady and you approach the work v-e-r-y slowly, and find that the tool just starts rubbing and squealing.  So you apply more cut and suddenly it digs in because it’s too much and everything stalls.  You need the material to be moving quickly enough for the tool to cut which means that enough heat is generated at its edge to locally melt the material.  The feed needs to be even to get a sensible “tooth load”.

Now my S7 has CNC control so I can feed at any speed I like, and I have a VFD so I’m not limited by the fixed pulley speeds.  I often part small diameters at 800 rpm and about 4 – 5mm/minute feed rate.

I have got a rear parting tool holder but it seldom gets used.  If you do go that route it is well worth forming a shallow “scallop” on the top face of the tool from the cutting edge back using a diamond needle file – this makes sure that the swarf curls inwards so it’s narrower than the cut width which helps it fall away and prevents clogging.

 

[Howard LewisParticipant @howardlewis46836]

As said, use the largest size tool shank that you can that will still bring the cutting edge to centre height.

Especially where parting is concerned, the greater the rigidity, the less will be your problems.

If you can install, inverted, use in a rear tool post.

The cutting forces involved will be better resisted by the lathe, and the swarf will fall away, rather than remain to clog the cut and facilitate jams.

If you can have a parting tool with a central groove, so much the better. There will be two, narrow, streams of swarf, curling inwards away from the surface to the work, lessening the risk of jams.

A steady, consistent gentle feed will lessen dig ins. The tool is neither rubbing, and being blunted, not forced too heavily into the cut.  Being brave, I use a power cross feed of 0.0025″/rev with an inverted, straight ground, HSS parting tool in a rear toolpost. Lubrication does help.

Jams are VERY infrequent, but do happen from time time with deep cuts

Howard

[DiogenesParticipant @diogenes]

The ArcEuro blade clamps in the sizes you are talking about hold the tool-tip at the same height as the thickness of the block – I don’t know whether the Glanze one is the same.

Dim.’e’ here;

https://www.arceurotrade.co.uk/Catalogue/Cutting-Tools/Lathe-Turning-Tools-Indexable/ARC-Indexable-Turning-Tools/SLTBN-Part-Off-Blade-Tool-Blocks-with-Part-Off-Blade

Edit – I use a blade-type backwards/forwards/up down etc. if you can get the tip on c/height it will be fine.

[duncan webster 1Participant @duncanwebster1]

Having had my fingers burned when buying stuff from abroad (handling charge of ~£20 to collect import duties of <£1) does anyone know how I can buy Eccentric Engineering stuff from  UK supplier? Or another supplier of the tee shaped blades with the groove in the top.

[duncan webster 1]

On duncan webster 1 Said:

Having had my fingers burned when buying stuff from abroad (handling charge of ~£20 to collect import duties of <£1) does anyone know how I can buy Eccentric Engineering stuff from  UK supplier? Or another supplier of the tee shaped blades with the groove in the top.

Have a look at the offerings from Chronos, I got some T shaped parting blades from them, not sure if they will fit your requirements?

Tony

[JasonBModerator @jasonb]

Just measured my 10mm Glanze one and the cutting edge sits 0.220″ above the bottom of the 10mm section.

[bernard towersParticipant @bernardtowers37738]

I think you’ll find the uk arm of eccentric engineering is no more.

[DiogenesParticipant @diogenes]

I think Tony is right, have a look at the Chronos ‘Chipbreaker’ ones, Duncan.

[SillyOldDufferModerator @sillyoldduffer]

Hope gabrielb isn’t worried everyone is suggesting a rear-tool post for parting off on a S7.  It’s not because the S7 is hopeless!  The problem is that below a certain size and weight all lathes struggle to part off because they’re not rigid enough.   If a correctly positioned cutter moves just a smidge, it binds or digs in. The risk is reduced with a power cross-feed rather than an unsteady human, but first move is to improve rigidity.

Any clown can part off on a big lathe, takes real skill to part off on a mini-lathe.    Myfords are stiffer than mini-lathes, but still not that heavily built as lathes go.      A lathe 50 or a 100kg heavier than a Myford will usually be rigid enough to part off with no fuss from the front, especially with power cross-feed.  However, putting a rear tool-post on a Myford (or similar) mostly fixes the problem because a hefty block of metal is far more rigid than a front tool-post.

Applying power-cross feed to parting off demands an act of faith the first time!  I felt my delicate skilled touch would do better than the machine, alas not.  Manual parting off is much more likely to fail than automatic.  Better to forget one’s pride,  use automatic feed, and do something useful: concentrate on keeping swarf out of the slot and applying lube!

Cutting speed, I always start with RPM = 10000/diameter of job, which is about right for mild-steel.

Dave

[SillyOldDuffer]

On SillyOldDuffer Said:

 

Cutting speed, I always start with RPM = 10000/diameter of job, which is about right for mild-steel.

Dave

Dave, I assume you mean the diameter in millimetres 😅

 

[BazParticipant @baz89810]

Duncan, Eccentric engineering stuff used to be sold in the UK by a Tania Sneesby who was related in some way to the proprietor in Australia. She stopped handling their stuff quite a few years ago. As others have said Arc do some T shaped blades.

[David George 1Participant @davidgeorge1]

This is my rear tool post parting holder and tool

It is solid and I can easily extend and reduce length of cutting tool to part off I have parted over 3 inch steel and ally with no problem. If you want any further ifo drawings etc just ask.

David

 

 

[Martin of WickParticipant @martinofwick]

Very nice tool holder David.

Is the the turret for the blade simply split horizontally with the hold down bolt providing the tool clamping pressure? Did you mill an undercut at the top and bottom of the blade slot?

[peak4Participant @peak4]

A couple more ideas to chuck in the pot from my own workshop, seen here on a Warco 720, which is a Super 7 clone.
I appreciate that none answer the question in the opening post, but might come in useful for others.
Firstly left to right
Rear blade parting toolholder; Solid lump of cast iron, so should be easy to replicate with a 3mm insert.
I don’t know the original source, as I picked it up second hand, but they were readily available new a good few years; I can’t find a current supplier though.

Centre is a Dickson style holder, designed for ½” HSS parting blades, here sporting an all-hard hand hacksaw blade segment, to make a very thin parting blade.

Right on a normal Dickson style toolpost, is a specifically designed blade holder, with a 2mm insert.
It works OK, but only with great care as there’s lots of overhang.

Next, the other two setups I have; There is another rear toolpost similar to David’s but not as well made, so I rarely use it.
Left is a spare Indian (?) Dickson style, mounted on a riser block, shown here with an inverted screwcutting tool, but could obviously be used with a parting one. When I bought the Warco, it came with a spare toolpost, so it either gets used like this, or moved over to the genuine S7

I also have a GH1330, which came with the 250 size wedge toolpost. I spotted a clearance sale one day, where a full toolpost with holders was cheaper than just a set of holders.
On the right is that extra dovetail wedge toolpost, on a riser plate, replacing the whole Myford/Warco topslide.
It makes for a pretty rigid setup, along the lines of a Gibraltar toolpost, but with changeable toolholders, though there is rather a lot of overhang with the parting blade one.
The riser plate was carefully ground, so that the tool centre height is correct on both the GH1330 and the Myford clone. It looks odd in the photo, but that’s just parallax error, front and rear tools are on centre height.

Bill

[David George 1Participant @davidgeorge1]

The blade is clamped between two steel plates with a dovetail on each half which holds the blade. Just unclamp with the cap screw and slide the blade forwards and backwards to suit the job in hand. The blade can get very close to the chuck so helps the cut. no need to adjust height as it was cut to match centre height. Only used two tips in over 2 years of use on many diferant metals.

 

David

[Neil LickfoldParticipant @neillickfold44316]

Coolant is needed to keep things from getting hot. If it gets hot, is when things fail.  The important part is that the blade runs true with the cross slide. No matter where it is.  As discussed previously, the machine needs to be fairly well locked down and rigid. So lock the top slide and lock the saddle for best results. Not too much wear in the cross slide nut and leadscrew.

Remember coolant to wash away chips and to keep it all from getting hot. The expansion is what causes the tool to jam up and to be grabbed.

The rear toolposts work well, because they have so little overhang from the mounting position.

Some people who do not do alot of taper work, replace the compound slide with a large solid block, and mount the tools onto that unit. With the added rigidity , parting grooving from the front is just as easy as from the back.

In my case, I have the slides fairly well adjusted with little movement. The only time I have had an issue with parting has been when I ran low in coolant in the bottle.

The tip inserts have a very nice geometry in curling the chip to make it smaller than the slot to prevent jamming. The tips will past a long time as well. Only when needed do I part off to the centre. Otherwise, I part to about 2-3mm diameter and hand was the last little bit. Most damage to parting blades occurs at the near zero diameter.

The last tip, is to try and feed at a constant rate, about 0.02mm/rev to 0.1mm/rev depending on the material being cut and how rigid the assembly is etc.

Often I part off at about 300rpm or so, that way the coolant makes a lot less mess than running 500rpm or so. Again speed is material dependent and its diameter.  My normal parting surface speed calculator is 318.3 x diameter(mm) divided by the surface speed (M/Min). Steels, mildsteel, to 4340 high tensile, I use 100m/min   Stainless and Bronze I use 60m/min, Titanium I use 20m/min,  Aluminium and brass I use 150m/min.   This is the max speed for the maximum diameter of the part. If the part is large in diameter, so over 40mm, then with the VFD control I will speed up in some cases to a max of 500 rpm as it gets closer to the centre. I don’t have a power cross feed, so hand feed all grooving. At 300 rpm I am hand feeding at about 0.1mm per second to 0.2mm per second. I watch the forming of the swarf more so than the absolute feedrate. So some materials definitely are feeding faster than others.

When the tool starts to dull, more pressure is required to part off and more heat is created. To get more life from the inserts, I have the inserts in a box and mark it for the material used. So when parting Ali, will use the insert from the Ali compartment for example.

Hope this helps those with any parting or grooving problems.

Neil

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