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

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