Back to front parting tool.

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Back to front parting tool.

This topic has 27 replies, 13 voices, and was last updated 8 July 2012 at 22:48 by David Littlewood.

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30 June 2012 at 12:28 #93391
Lambton
Participant
@lambton
Eccentric Engineering of Australia are offering a new BTF (back to front) parting tool that is intended to be used in the normal front tool post with the lathe spindle running in reverse. this is probably fine for lathes that do not have simple screw-on chucks. Any attempt to use this type of set-up on a Myford lathe would result in the chuck unscrewing creating a dangerous situation for both the operator and the lathe.

I have attempted to email Eccentric Engineering alerting them to this as their sales blurb makes no mention of this problem.but their web site contact page will not accept my message as the telephone number field would not recognise a UK phone number even with the usual international prefix.

. i am sure the device offered will be very useful to owners of cam lock and similar lathes but must not be used with screw mounted chucks.
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30 June 2012 at 12:28 #22135
Lambton
Participant
@lambton
Dangers of using on Myford lathes..
30 June 2012 at 12:38 #93393
David Littlewood
Participant
@davidlittlewood51847
I must admit I have never been able to understand what all the fuss is about with upside-down parting tools, whether rear-mounted or front. If you get a decent tool, such as the Q-Cut which I have used for years with entire satisfaction, the fuss suddendly seems meaningless. I'm not, anyway, convinced by all the half-baked attempts to demonstrate that the upside-down thing is any more rigid. I was convinced by the Q-Cut when I saw a Myford demo of parting off under power cross-feed at a fairly high speed.

And yes, I have a larger lathe (M300) with a Camlock chuck, but I still wouldn't give the time of day to this mumbo-jumbo; I just use a larger equivalent to the Q-Cut – and under power feed.

David

Edited By David Littlewood on 30/06/2012 12:39:55
30 June 2012 at 12:52 #93394
chris stephens
Participant
@chrisstephens63393
Hi Eric, Perhaps the chap hopes we rich Brits, in the old country, are wealthy enough to own big bore Myfords that have screw-on, but lock-on-able, chucks.

I suspect the tool works well enough because of the top (or maybe in this case it is BOTTOM) rake he has built into the holder. If you put top rake in an ordinary right-way-up parting holder it will work too. The upside down tool is traditionally used on lathes that are a bit suspect rigidity wise, as the forces tighten the dovetails?

If there is a secret to parting it is having the confidence to keep a steady speed of cut, oh, and a sharp tool.

Stand by to hear all the rear mounted parters saying theirs is the only way.

chriStephens
30 June 2012 at 13:24 #93396
Donhe7
Participant
@donhe7
Posted by Eric Clark on 30/06/2012 12:28:47:

Eccentric Engineering of Australia

I have attempted to email Eccentric Engineering alerting them to this as their sales blurb makes no mention of this problem.but their web site contact page will not accept my message as the telephone number field would not recognise a UK phone number even with the usual international prefix.

Eric, I have pasted a copy of your post in the "Contact Us" section of their Website, on your behalf, and await an acknowledgement from them, but it being late on Saturday evening here in Oz, I don't expect a response from them until possibly Monday, but it seems that my email was accepted, we'll wait and see what happens

donhe7

Just checked my emails and your / my message has been acknowledged, so it at least made it to the company!!

Edited By Donhe7 on 30/06/2012 13:28:24
30 June 2012 at 15:28 #93407
Eccentric Engineer
Participant
@eccentricengineer
Hi All

Yes I did recieve the relayed email from Eric/Don, thanks for that.
Getting a bit late in Oz but I thought it easiest to just send a reply straight here.

There is a warning not to use the upside down holder on lathes with a threaded nose, it's on the product description in the shop section of the website, just above the buy it now tabs. I've also put a warning on the magazine ad and the email flyer that I've sent to previous customers. I thought that would be enough but I'll add one to the information page as well, just to make sure.

As to whether they work or not, all I can say is I've used mine every working day for the last five years, I've never had a jam, I'm still using the same blade, and it's only about 1/4" shorter now than it was five years ago (it's the same one that's in the video). The only slight inconvenience I've found with the BTF holder is having to stop the lathe and put it into reverse.

When I was still in the workforce I saw plenty of crashes in the workshop with a indexable tip parting tool (Sandvik), a couple of the crashes were mine . I just find the upside down tool is more forgiving.

Disclaimer : I have no connection with this business other than as a satisfied owner .

Upside down parting tools may not suit everyones circumstances, but here's a note I recieved a few weeks ago from a customer who'd just bought a second one.

I was so impressed with the BTF toolholder I showed a friend. He wanted one as soon as I showed him a sample of what it could do. I have a Colchester Student lathe but have never been able to part off using any of the standard parting tools. I was able to part off 30mm Al alloy and 25mm mild steel without any issues. Brilliant! LH diamond toolholder is a good addition as well.
Mark from Queensland.

Cheers all
Gary
Eccentric Engineering

I was so impressed with the BTF toolholder I showed a friend. He wanted one as soon as I showed him a sample of what it could do. I have a Colchester Student lathe but have never been able to part off using any of the standard parting tools. I was able to part off 30mm Al. alloy and 25mm mild steel without any issues. Brilliant! LH diamond toolholder is a good addition as well.
30 June 2012 at 17:31 #93416
chris stephens
Participant
@chrisstephens63393
Hi John,

That's a bit of a jaundiced view of tangential tools isn't' it? Granted they are no better than a well formed bit of HSS, they have many advantages. Not least of these is the ability to get a well formed and very sharp cutting edge, that a complete and utter beginner can get with perhaps, at most, 10 seconds tuition. This fact can help beginners to get a better finish on their work because they are often afraid to sharpen ordinary HSS , thinking it is complicated, and so opt for wholly inappropriate indexable Carbide tooling. I am sure that you are well versed in HSS grinding, as am I, but I would not give up my Tangential tooling for all the chip butties in London. Another advantage is that you do not need to hone the tool after re-sharpening, and there is no way that ordinary HSS will out perform a Tangential without honing! Yet another advantage is that you very soon learn that you do not need to have a different tool for every material, two if you count roughing and finishing, or have a different tool for facing and sliding cuts. One tool will do a more than adequate job and, in my view, often a better job than a piece of HSS held in the "old fashioned" way. Yet another advantage is the ease of setting tool height, not every body has the QC tool holders! I could go on but I expect you get the picture.

You are the only person that I know who rates this type of tool as "not very good", This last week I have turned brass, bronze, stainless, mild steel, aluminium and nylon, all have been done with just three tools, a tangential, a parting tool and a boring bar, four if you count drills. At no point did I think, "this is not very good, I wish I had wasted lots of time grinding up a piece of HSS". I do recommend you spend an hour or so making one and then say precisely where you find it is a let down.

Best Wishes

chriStephens
30 June 2012 at 17:51 #93418
michael howarth 1
Participant
@michaelhowarth1
Chris…..Have you got any more information on your tangential parting off tool? I couldn't get to AllyPally to see it in action but you did threaten to post some pictures a while ago. The time I spent making a tangential turning tool has been well repaid.

Mick
30 June 2012 at 18:07 #93419
chris stephens
Participant
@chrisstephens63393
Hi Mick,

Thank you for reminding me. Somewhere under the mass of papers on the floor around my desk is the charger for the camera. As the paper is getting to the self imposed four inch depth limit that I have set myself, I shall soon have a clear out and hopefully find the wretched thing, so I can take photos.

Glad you found the time spent making your tool to be worth while, perhaps we should organise a 190 year birthday for them next year. It was 1823 when Brunel's dad started using them, wasn't it??

chriStephens
1 July 2012 at 00:46 #93448
I.M. OUTAHERE
Participant
@i-m-outahere
I've been using a set of indexable tools and found the set of tips that came with the set to be rubbish and now have to spend even more money buying a set of quality tips .

I went back my tangential holder and if it gets blunt it takes only a minute to sharpen the tool , i also sharpen the other end so have 2 cutting tools ready to go .

I spent the last 20 years grinding cutting tools from tool steel and still do so if needed but i find my tangential tool does 90% of what i need with less hassle .

If i need an extra fine finish i use tha tangential tool to rough it and finish with a custom ground tool , it only takes a second to index it around on the toolpost and means this tool does a minimum of work and will stay sharp for longer .

I put a small radius on the corner of the tool to aid in a better finish and this is done along the corner over the entire length of the piece of tool steel using a diamind file i also grind the other end so its tip uses this radius as well .

I have a small chineese lathe and for what it cost i have no complaints other than it not having a reverse gear for the leadscrew but this will be sorted by about lunchtime today .

I use a rear mounted tool for two reasons :

Ridgidity – the compound slide on these machines are relatively small and flex very easily so need to be removed and a higher toolpost mounted , something similar to the Gibraltar type of toolpost .

This means more work as you need to remove and replace the compound slide as needed but by setting the compound slide parrallel to the cross slide helps a little as the forces are acting along the dovetail of the compound slide and not across them .

I went to the rear toolpost and never looked back !

More versatillity – the rear post also allows more tools to be mounted , say for instance a chamfering tool and the parting tool on the rear post and cutting and threading tools on the front post .

I find a tool with a tip ground with a point that has a 90 degree included angle is good for cutting 45 degree chamfers and saves having to change the angle of the front cutting tool .

IAN
1 July 2012 at 02:40 #93451
chris stephens
Participant
@chrisstephens63393
Hi John,

I know that you produce work of the highest calibre and imagination, but I suspect that you are "classically" trained. Thereby hangs the problem, all too often myths are spread from one tutor to his pupils, who in turn become tutors themselves. To produce accurate work you need an exemplary finish, for as you know you cannot measure a rough surface, and you can get an exemplary finish in almost all materials with just the one tool. You will note I am talking here solely about what are known as "finishing cuts", for roughing or bulk removal there are far far better tools. Again I am talking about home environment, where time is of little or no importance but end results are everything.

As for inappropriate tips, they are made by the manufacturers for very specific purposes, very few of which are small light home lathes nor for chasing tenths. There are of course some truly brilliant tips, if you know which ones to buy, that will leave a finish on mild steel that is almost indistinguishable from a chrome plated one, as anyone who has seen my test piece at shows.will attest.

But, if you don't like tangential tools that is fine by me, there is never ever just one way to do things engineering wise, but some are more convenient than others. The DRO on your lathe is a classic example, a great convenience of which I am jealous, but I am not as rich as you so I will have to wait. I have to do it the old way of cutting and measuring and taking a final cut to take the last half thou of diameter, for which a tangential works just fine.

I hope to are keeping well, I miss your write ups on the various forums.

very sincerely

chriStephens
1 July 2012 at 02:54 #93452
clivel
Participant
@clivel
As a novice one of the biggest hurdles I had to overcome was the thought of grinding and sharpening lathe tools.

Books and magazine articles catering to beginners list a variety of "necessary" tools each serving a different purpose and each accompanied by sketches of the relevant angles for back clearance, front clearance, side clearance, top clearance etc etc which only served to reinforce the notion that tool grinding is a black art acquired only after years of experience.

Not having a nearby ME club or friend with machining experience to show me the basics, it was only after I acquired a few indexable tools that I plucked up the courage to actually start making things on my little Unimat lathe. However, and probably very much related to my inexperience, but try as I might I could not get a decent surface finish on some metals especially steel.

So after having read a number of good reports on the Diamond toolholder I decided to splash out on what seemed like a relatively expensive acquisition. When the tool arrived I mounted the supplied bit in the supplied grinding jig, turned on the newly purchased bench grinder and 30 seconds later had what appeared to be a correctly sharpened tool bit. I mounted the tool holder and bit on the lathe and attacked the same material I had been struggling with before. I was stunned at the result. The finish was excellent, silky smooth. I now find that the tool serves most of my turning needs (which may of course change as I gain experience).

But more importantly, this gentle introduction to tool grinding also gave me the confidence to grind a boring bar from scratch when I needed to bore out the cylinder of my first oscillating engine a few days later. Something I wouldn't have dreamed of attempting before.

As a beginner I can wholeheartedly recommend the diamond toolholder. It works well; far better than the expensive indexable tool set I was using before, it leaves a lovely surface finish and is extremely easy to sharpen. The only minor irritation for me, and that is because I also use the lathe as a mill and drill, is the constant need to set the toolpost to 12 degrees every time I replace it.

Of course none of this may apply to the more experienced machinist, but for now it serves me well. And although not cheap, I consider it money very well spent.
1 July 2012 at 15:04 #93489
chris stephens
Participant
@chrisstephens63393
Hi Clive,

Another convert!

I do feel that having a tool that is p*ss easy to sharpen opens the door to the possibilities. A it gives you the confidence to use a grinder and B it shows you what sort of a finish you can expect to get

I, too, don't like moving the tool post about , once set square for parting purposes i am loathe to move it. Eccentric now ,I understand, make a "square on" tool holder but as a model engineer why not make your own square on one, there are many deigns to be found on the 'net.

chriStephens
1 July 2012 at 16:43 #93494
_Paul_
Participant
@_paul_
I have used the Original Eccentric Engineering tangential tool for years with great success it's surprising what you can make it do a little ingenuity.

IMHO It's most endearing factor is the single facet sharpening.

Cutting with it toward the headstock will if you angle it correctly really peel metal off same tool same angle only cutting away from the headstock will produce a really good finish, how many traditional tools will do that?

I bought mine after watching Rudy Kouhoupt using it.

Paul
2 July 2012 at 07:40 #93530
Anonymous
There has been much mention of a 'good finish' in this thread, from this tool or that. I'm confused as to whether I'm achieving a good finish or not on my turned parts. Do I stick with my current methods, or do I need to investigate new tooling?

So what exactly constitutes a good finish, and how do I know if I'm achieving it?

Regards,

Andrew
2 July 2012 at 09:11 #93533
Lambton
Participant
@lambton
"Good finish" is a bit like a movable feast it depends very much on the function and interface fit of the component being machined. For example the piston and cylinder for a small IC engine will require a very much better finish than the non critical outside surfaces of an item of workshop tooling.

There is of course the aesthetic argument that a good finish always looks good and is the mark of a skilled workman.

For years I was in charge of the engineering department of a manufacturing company in the midlands. When young graduate engineers fully trained in CAD drawing started to arrive I had great difficulty in getting them to only call for fine finish and close tolerances when they were really required as both cost more money to achieve. They were in the habit of setting uniform finish and tolerances for all surfaces regardless of the practical needs simply because the CAD program allowed them to without having to put too much thought into what they were doing.

I also taut them to select available materials from suppliers catalogues rather than from BS specifications as many of the grades in the BS specn. may not be available at any price.

A spell of practical work in the tool room soon made them understand the practicalities involved in making good functional items that fulfilled the intended purpose. From then on their CAD work became a much more realistic and they mostly became first class "real" engineers.
2 July 2012 at 20:19 #93564
clivel
Participant
@clivel
Posted by Andrew Johnston on 02/07/2012 07:40:07:

There has been much mention of a 'good finish' in this thread, from this tool or that. I'm confused as to whether I'm achieving a good finish or not on my turned parts. Do I stick with my current methods, or do I need to investigate new tooling?

So what exactly constitutes a good finish, and how do I know if I'm achieving it?

Regards,

Andrew

In general, if surface finish does not affect functionality as would be the case of for example pistons and cylinder bores, then it is purely a matter of aesthetics.

When using carbide insert tooling on my little lathe the surface finish I was getting on the pieces of CRS I had at hand looked and felt like a poor attempt at screwcutting.

Now I have no doubt that this is probably due to my inexperience but despite trying various combinations of feeds and speeds and depths of cut I was unable to generate turned surfaces which I found aesthetically pleasing

After many hours of unproductive experimentation I ordered the diamond tool holder. Within minutes of fitting this to my lathe I was producing smooth surfaces that I found pleasing to the eye on the exact same pieces of CRS that I had struggled with before.

So to answer your question, beauty is in the eye of the beholder and if the surface finishes you achieve are rough enough to scour a pot, yet satisfy your sense of aesthetics there is no need to change your methods or your tooling.

Clive
2 July 2012 at 21:34 #93571
chris stephens
Participant
@chrisstephens63393
Hi Guys,

First off i must apologise to the OP we seem to have got of the original topic a bit, but no harm has been done especially if we have given hope to some who can't get as good a finish as they had hoped.

Now about finish, here is a little test for those who think they already get a good finish. Make a fine cut of no more than say 5thou depth of cut and stop every 1/4" or so and if you can't see where you stopped the travel, your tool is cutting well, if you can see a polished witness mark, oh dear!

chriStephens
2 July 2012 at 21:43 #93573
John Stevenson 1
Participant
@johnstevenson1
Posted by chris stephens on 02/07/2012 21:34:59:

Make a fine cut of no more than say 5thou depth of cut and stop every 1/4" or so and if you can't see where you stopped the travel, your tool is cutting well, if you can see a polished witness mark, oh dear!

chriStephens

Any body working for me using 5 thou cuts and stopping every 1/4" or so would get my boot up his arse.

John S.
2 July 2012 at 23:15 #93580
chris stephens
Participant
@chrisstephens63393
Hi John,

You have to tke lots of 5thou cuts to make the job last longer, especially good if you get paid by the hour.

chriStephens
2 July 2012 at 23:45 #93582
Anonymous
Oh dear, I get paid by the hour to design electronics, but machining jobs are normally done at fixed cost. So on that basis I'd have to kick myself up the posterior for taking 5 thou cuts, if that's anotomically possible.

Andrew
2 July 2012 at 23:53 #93583
chris stephens
Participant
@chrisstephens63393
Hi Andrew,

If it wasn't going even more off topic there are , I am told, clubs you could go to if you can't manage it yourself.

chriStephens
8 July 2012 at 12:01 #93913
Anonymous
Plenty of food for thought here. Ultimately there's no substitute for actually seeing a finish that is described as 'good' in order to make a comparison with ones own efforts.

I tried, and failed, both the tests mentioned above. For milling I used a 2 thou depth of cut, using a carbide end mill running at 2000rpm, on the side of a 22mm thick slab of hot rolled steel. I was climb milling. The finish at a feedrate of about 10mm/min was definitely worse than at a speed of about 200mm/min. The finish at the higher speed was smooth, but not a mirror finish. For turning I used a piece of 7/8" diameter EN3 from the scrap bin. Turning at 1200rpm, depth of cut 5 thou and feedrate of 2 thou/rev I stopped and started the feed a couple of times. A witness mark was just about visible.

Still, I'm not downhearted; I normally expect to achieve a finish on the order of 1 to 2µm Ra, sometimes better, sometimes worse, depending on material and the finish I actually need.

As an aside, last weekend I designed and machined some jigs for a company to allow them to hold a part for coating. As part of the design exercise I normally get the part and its associated drawing to allow me to design the jig. One area of the part had quite a coarse finish, almost like a fine thread. For that area the drawing actually called out a specific insert tip radius and feedrate. First time I've seen that.

Regards,

Andrew
8 July 2012 at 13:46 #93919
Bazyle
Participant
@bazyle
Back to the original topic.

With a rear mount the cross slide lift is held by the plate commonly fitted under the bed. WIth a front mount and reverse spindle the holding force is the added apron weight and the probably loose fitting rack pinion with possibly something in the feed power takeoff.

Is this significant? (for hobby lathes not production sized stuff)
8 July 2012 at 14:06 #93921
blowlamp
Participant
@blowlamp
I don't know how significant it might prove to be with regard to the use of this tool, but as far as I'm aware, lathes such as Boxfords don't have keep plates under the front vee slide to prevent the carriage assembly lifting when the spindle is reversed.

Martin.
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