2 questions – threading silver steel; tightening bar in the chuck

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2 questions – threading silver steel; tightening bar in the chuck

This topic has 41 replies, 15 voices, and was last updated 7 May 2010 at 21:00 by Sub Mandrel.

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14 April 2010 at 21:41 #50695
AES
Participant
@aes
Ladies & Gents,

Well it does say “no question is too stupid if you don’t know the answer”, so here goes:

1. I have not yet graduated to form tools for threading – so far I’m using only HSS taps & dies. I now “need” to put a male thread on a 10 mm dia silver steel bar. Can I do that (gently) with the die (in the die holder on the lathe, turned by hand – and having first turned the OD portion of the bar to the appropriate crest dia of course) with the silver steel bar in its hard (as supplied) state, or do I need to soften it first, then temper it after threading? Just for info, it’s going to be a new toolpost retaining stud for my Asian mini lathe.

2. I was always taught that when tightening Jacobs-type chucks (e.g. fitting a drill bit into a hand, or electric, or “windy” drill) that one should use every one of the chuck key holes and (as far as possible) tighten the chuck equally onto the drill bit from all 3 (or 4) chuck key holes. So what is the “best” way to tighten work into the lathe chuck (either 3 or 4 jaw, independent or self-centring – if there’s any difference). Please note that I’m NOT talking about putting an extension tube onto the chuck key tommy bar, nor am I talking about belting the tommy bar with a hammer – just “normal hand-pressure tightening”.

All guidance on the above 2 Qs from the many (clearly very experienced and knowledgeable) people posting here will be much appreciated.

Thanks in advance.

Krgds

AES
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14 April 2010 at 21:41 #5033
AES
Participant
@aes
14 April 2010 at 22:11 #50696
peter walton 1
Participant
@peterwalton1
HI

Silver steel rod is always supplied in an annealed state, so thread and then harden and temper if needed.

Never heard the one about jacobs drill chucks, heard it about lathe chucks as they have a scroll which can have play after some years of use(abuse etc)

My take on the chucks is, tighten up fairly hard but not excessive, do the machining or whatever but make sure you do it all at the same sitting so I see no point to the tighten in all holes etc.

If the work need to be replaced use a 4 jaw independant or a collet chuck.

peter
14 April 2010 at 22:11 #50697
peter walton 1
Participant
@peterwalton1
double post

Edited By peter walton on 14/04/2010 22:11:38
14 April 2010 at 22:30 #50699
Ramon Wilson
Participant
@ramonwilson3
That’s correct AES it isn’t.

Silver steel in it’s ‘as supplied state’ is not ‘hard’. It is however a ‘toughish’ carbon steel capable of being hardened by heat treatment. You should be able to produce a 10mm thread on a piece of silver seel without too much problem but you will probably need to ensure that the ends of the bar as supplied are cut off about 2-3mm before doing so. Sometimes, though not always, the very ends of these bars have been ‘hardened’ by the heat from the cut off process. By parting off that small piece you will ensure that your die lasts a little longer! Put a nice chamfer on the end, use plenty of cutting fluid – Rocol or Neatcut or the like and if possible ‘back’ the die up wih the drill chuck face (retract the jaws) to keep the die square as you start the thread. (That’s assuming you are using a hand held die holder not a tailstock version). Silver steel can be a bit ‘bitty’ to thread and produce a smooth thread form, but it can be done. If you decide to use ‘power ‘ put it in lowest backgear and make sure your fingers aren’t in the way -theres an awful lot of torque in back gear!

Chucking – well – Jacobs chucks, I’ve seen this ‘every hole’ method, have heard of it but never seen the need to do it myself – no problems so far.

Self centreing chucks, 3 or 4 jaw, – normally have one chuck key hole marked ‘0’ and this is the one that shoulld be used though again most of the time I forget and have no problem – normally only remembering when the piece chucked looks a bit eccentric. Slackening off, rotating the workpice and re-tightening normally does the trick for most of the time

The 4 jaw independant chuck is totally different. Each jaw as stated is independant of the others and is normally used when the workpiece is out of round or of unusual shape. Centreing the work then requires a different method. I would not put rough ‘black’ mild steel round in a three jaw as this can be well out of round and will strain the chuck. Use the 4 jaw first to establish a ‘chucking’ piece then if required this can be held in the 3 jaw safely.

Hope this goes some way to help – I’m sure ohers will want to add and help too

Good luck with your endeavours

Regards – Ramon
14 April 2010 at 23:08 #50700
mgj
Participant
@mgj
M10 coarse from a die – depends on the size of the chuck, but there is a good chance of the job turning and possibly being scored.

Next question is how accurately does this thread need to be “squared”. If it has to be concentric concentric than you have two options;

Set up in a 4 jaw or collets, and screw cut to near finished size. Finish off with a die. (Best to finish off with the threading tool, but that method is pretty much OK.) you say you haven’t screwcut – well it isn’t very difficult and now is as good a time to learn as any.

If it doesn’t need to be truly concentric, then die it to size. I’d be inclined not to put it in any kind of self centring chuck simply because its difficult to get enough grip. Especially in a small 3 jaw.

If marking the material, even silver steel, is a problem, then use bits of ali or brass sheet under each jaw.

Last question – if its a simply a toolpost stud, why do it in silver steel at all? A length of M10 bright bar in free cutting mild will do very well and will be 10 times easier to cut and a lot cheaper. I have one in 7/16 on the Myford which has lasted 25 years or so serving exactly the same duty, and the 6″ lathe has one in 5/8″ 220M07 leaded free cutting which is showing (predictably) nil wear after 2 years.
15 April 2010 at 09:24 #50705
KWIL
Participant
@kwil
Silver steel screw cuts a treat, set the tool height correctly and use a little cutting fluid, but I agree, what is wrong with bright bar?
15 April 2010 at 10:12 #50706
AES
Participant
@aes
Thanks very much to all for the very helpful (and prompt) responses. I’ll try a couple of the tips re threading the silver steel bar (like cutting the 1st 2-3 mm off the end).

To those who have asked “why silver steel?”, it’s a fair question, and my answer is simple – “because it’s there!”

In other words, as I’m just starting out, I don’t have all that much stock to hand. For the toolpost stud job I have brass and ali (as well as silver steel), but no suitably-sized ms of any description in stock. As I’m sure many of you will appreciate, you don’t buy metal stock just like you buy a bag of sugar from the supermarket (!), and until I find a suitable supplier (none that I can see here in Switzerland who sells in “our” quantities, the nearest being Germany, France, or UK) there is the question of shipping cost/post, plus import duty to consider. In addition, not only is it costly “just” to order one piece of ms (I was waiting until I can place a reasonably-sized order with someone), there’s the “inconvenience” of waiting 7 – 10 days for the stuff to arrive. As the bug is biting fairly hard right now I wanted to try the job “NOW”!! And I need a better toolpost location anyway (see below).

For the same reason, I was waiting to order thread form lathe tools (and to try my hand at that) until AFTER I had a better/stiffer toolpost location – the as-supplied item is a bit wimpy and certainly allows some UP/DOWN movement at the tool tip, even on only light cuts.

Again thanks to all for the comments.

Krgds

AES
15 April 2010 at 10:17 #50707
AES
Participant
@aes
To add to my comments above – thanks for the info that as-supplied silver steel is not “hard” but “tough”. Something else I’ve learnt!

Krgds

AES
15 April 2010 at 11:12 #50709
Martin W
Participant
@martinw
Hi AES

Your comment about tool deflection interested me as I wonder whether this is associated with tool post stud flexing or elsewhere. I assume that the current tool post stud is 10mm and can be tightened down fairly securely. If this is the case then, unless the tool holder assembly bottom surface or top slide surface are not true, the stud only pulls these mating surfaces together and it is these surfaces which then take the brunt of the load.

I would be inclined to check if there is any movement elsewhere in the system starting with the setting of all of the gib strips. I too have a chinaman lathe, supplied by Chester UK, and it suffered very slightly from tool deflection, under heavy loading in my case, but after a good clean, lubrication and adjustment of the gib strips all is well and I can take relatively large cuts as well as parting off steel bars greater than 25mm dia without any problems.

While it won’t necessarily help you I ordered a Dixon type quick change tool post from RDG and fitted this to my lathe. The increase in stability was massive partly due I suspect to a stiffer tool holding assembly and the greater mass near/supporting the tool. Another point is to keep your tool overhang to the minimum for the task in hand as this helps to stiffen things up and helps to prevent tip deflection.

If I am teaching my gran how to suck eggs then I apologise. The lathe I have got is the Chester Model DB7V so you can compare this with you machine for size and functionality.

Cheers

Martin
15 April 2010 at 12:03 #50711
AES
Participant
@aes
Thanks for the comments Martin – and don’t worry about my granny, she doesn’t even know ehat an egg looks like ….

Your comments about tool deflection are very perceptive, because I’m really caught in a bit of a vicious circle. First, the toolpost stud as supplied is a bit “floppy” in the female thread on the cross slide. I tried an ordinary off the shelf 10 mm bolt and that too was a bit loose – in other words the manufacturer has cut the female thread a bit on the big side. I thought about drilling out and re-tapping the next size up, but then the clearance hole running through the centre of the toolpost would result in not all that much meat remaining in the centre of the toolpost (I thought).

So the “solution” I’ve settled with is to cut a new 10 mm toolpost stud (using sliver steel!) with its thread cut as “big” as I can possibly make it (die very slack), and use plenty of Loctite in the female hole when finally re-assembling. But to add to the rigidity of the toolpost stud fixing I also tried a standard 10 mm nut (cut down to 5 mm thickness) on the upper surface of the cross slide – trying this out with a bolt definitely improved the rigidity of the whole set up. And yes, thanks for the reminder, I have already re-set the gibs on both the top slide and the cross slide to the point where turning the handles is now pretty stiff.

To add to my problems I have already bought a QCTP (the “A2Z” device, bought from Little Machine Shop in the USA), and although it does fit my lathe it requires some small mods including a packing piece underneath to get the right tool height and to allow the toolpost locking lever to lock down on to the existing toolpost stud.

So right now I have both the original toolpost plus the QCTP sitting on top of my 5 mm thick locknut, which incidentally measures 19.5 mm across the peaks of the hex – a lot less than the base area of either of the toolposts. Clearly this NOT the ideal situation!

So my thought now is to counter bore the under surface of both toolposts out to 19.5+ mm x 5 mm deep, thus allowing the full base surface of the toolposts to contact the top surface of the cross slide once again.

The trouble with that idea is that I haven’t got a 19.5 mm dia drill (and doubt that I could turn it if I did have one – and it wouldn’t fit the lathe drill chuck either). So up to now I’ve been packing the gap (5 mm) between the toolpost base and the edges of the locknut and then (having already drilled the 1st part of the counter bore as far as I can with a drill – 13 mm) I’ve been trying use the boring tool to bring the counter bore out to the 19.5+ mm required.

Guess what? The whole thing is still not rigid enough, so unless I use VERY light cuts (less than an Imperial thou) the whole thing flexes so much that I can’t bore at all!

So it looks like it’s going to take me a month of Sundays to get set up for a rigid toolpost mounting – unless you or anyone has any other ideas?

And all because (NOT “the lady loves Milk Tray”) but because lathe manufacturer cut the female thread for the stud a bit too “floppy” in the cross slide!

I apologise for the length of this reply – I hope it’s clear.

Again, any and all comments welcome (unless it’s “Why don’t you take up stamp collecting) ….

Krgds

AES
15 April 2010 at 12:19 #50713
Martin W
Participant
@martinw
A quick addition to my previous post. The RDG stock number for the quick change tool post is 725MYFORD and while I said it was a Dixon style the larger version they sell is compatible with Dixon type assemblies (so they say).

I had to make a plate to fit this tool post onto the top slide and increase the locking stud diameter from 10mm to 7/16ins to match the through hole on the tool post but with 10mm thread top and bottom to mate with the top slide and to keep the locking system the same. I had already dispensed with the supplied locking handle, bruised palms, and replaced this with a 10mm nut with existing thick washer. The stud was made from EN1 steel and works fine which supports what mgj says above.

The only other thing I did was to make new height adjusters for the tool holders to bring their adjustment to mid range for the tooling I am using.

As I said before this has made a massive improvement in the performance of my DB7V.

Cheers

Martin
15 April 2010 at 13:32 #50717
Versaboss
Participant
@versaboss
Hi AES,

It seems you have a strange problem here. Would you mind to disclose the type of lathe you have? I cannot understand that a floppy thread can give the results you describe. As soon as the nut is tightened, the stud is under tension, and all floppyness should disappear I think.

But resting the toolpost on a nut is definitely a no-no!

Boring the 19.5 mm hole – yes you should not use a drill; btw drills in this size usually have a Morse 2 shaft. But this ‘cut’ of less than a thou makes me again think that something is fundamentally wrong. Even ten times as much is not a heavy cut.

But it is difficult to make a diagnosis without seeing the setup.

Material suppliers in Switzerland – well ‘it depends’. Pestalozzi in Dietikon sells also really small quantities, but you should fetch it yourself in their warehouse. They deliver only by truck, and that’s expensive. Now if you happen to live in Geneva then this is not a good idea I admit. The only other way I can suggest is to find a nearby mechanical shop and ask politely…

Ah, and the thread form tool? You don’t have the chip inserts in mind, do you? In a lifelong time of hobby tinkering and 10 years of semi-professional machining I never felt the urge to use them. And on a ‘floppy’ lathe–I would know better means to burn money. Most of my threading is done with tools made from these ubiquitous ‘broken center drills’ (used in a GHT retracting holder, worth its weight in gold).

Greetings, Hansrudolf (from central Switzerland)
15 April 2010 at 13:40 #50718
Circlip
Participant
@circlip
Can’t understand an ” ordinary ” bolt being floppy? Was going to suggest you use an 8.8 HTS bolt or a long Cap(Allen)screw as the donor to make a suitable drawbolt/stud.

If you do go down the Silver Steel route, trim the end as stated, turn the dia. down to 9.9 and chamfer the end as a start, cut/die the thread, degrease put in oven at gas mark whatever (Untill dark blue/purple) remove and quench in oil.

Jobsaguden.

Regards Ian.
15 April 2010 at 14:31 #50719
KWIL
Participant
@kwil
All I can say is beware of QC toolholder that are said to be compatible with Myford etc, check before you buy is all I can say here.
15 April 2010 at 20:47 #50726
Francois Meunier
Participant
@francoismeunier96697
Hi AES,

For me, the problem does not arise from the tool post stud but from the square toolholder supplied with these chinese lathes, which bend upon tool tightening. you have to lock the tool holder with the stud nut, and then tighten the tool (not too heavily). If you want to rotate the turret for another tool, as soon as you release the nut, the turret becomes distorted and cannot stay flat anymore on the cross slide, giving that poor tool holding you mentioned. I have seen that on the minilathe but also on larger lathe eg sieg BV20 and its clones.

I would bet that changing of toolpost will solve this problem.
Cheers

FM
15 April 2010 at 21:40 #50730
Ramon Wilson
Participant
@ramonwilson3
Hi AES,

Have to agree with the above posts – cutting the thread is one thing but if as you say you can only take one thou cuts and still get deflection then something is definitely very awry.

You really do need to sort out this problem before you begin to take on a project. I’m sure the guy’s above would agree, if we could see the set up that would be a big help.

Is it possible for you to take several pics of your set up from different angles so that the problem can be seen a little clearer – that would certainly enable more understanding of the situation.

My comiserations on your supply difficutlies, that must be frustrating at the best of times.

Regards – Ramon
16 April 2010 at 00:56 #50738
Martin W
Participant
@martinw
Hi AES

Sent private mail re tool post problems, if you feel this could help drop me an email at address supplied.

Are you using the supplied brazed carbide tipped tools, assuming any were supplied? If so see if you can get hold of some HSS tools and try them, often these will perform better than the carbide tipped varieties that are supplied as standard. Secondly the hss tools can be readily sharpened, if somewhat crudely, on a standard grinding wheel (MGJ I know not the best way but when the devil drives and needs must etc etc. ).

Regards

Martin

Edited By Martin W on 16/04/2010 01:12:44
16 April 2010 at 10:49 #50752
AES
Participant
@aes
Gents,

I am VERY grateful for all the helpful hints, tips, & comments received since my original post (which at the time of writing this was only 36 hours ago!). Fantastic “service”, thank you all for your willingness to help.

Right now I am rather busy with “work work” but will be responding to all the Qs etc above over the weekend. I’ll also try to put som pix up, as per the requests above (I’ll also have to work out how to do that first, but should have time this weekend).

Meantime, for Martin W, you say you have sent me a private mail but so far nothing received. Am I allowed/should I add my E-mail address here?

Again thanks to all, until later ….

Krgds

AES
16 April 2010 at 15:57 #50763
Martin W
Participant
@martinw
Hi AES

Re the private mail I sent to you. To read this ‘log on’ to this site in the normal way and then in the ‘My Account’ box on the top left of the page click on the ‘My Messages’ line and this will open your Mail Inbox. You should then be able to read the PM I sent re the above topics.

Hope this helps, this type of PM messaging allows members to contact each other without having to put their personal email address onto to a site for all the world to see, most open forums have this type of messaging service.

I would advise that you NEVER put your personal email address on any open sites like forums because then it is open to abuse from malicious ‘nere do wells’ whose IQ is inversely proportional to the amount of time they have on their hands. Once you have read my PM then you can, should you wish, email me at the address supplied or PM me back on this site by clicking on the ‘message member’ located in the grey bar, directly under one of my posts.

Cheers

Martin
16 April 2010 at 18:42 #50771
mgj
Participant
@mgj
Martin – tool sharpening. I agree – when the devil rides etc. The only problem is that if one is a bit of a beginner it might not be so easy to grind one up, and a good preformed carbide one might help isolate the problem. Mind you if AES has a tool that can routinely take .001 cuts he should be quite a dab hand on the grindstone – better than me.(but not as good as the Quorn) (actually Quorn is out, tangential is in)

This has sort of spread into a wider issue,

first question is how do you know it is not rigid? (Apart from the fact that its sitting on a hexagon nut which needs replacing with a fat flat machined “washer” the width of the toolpost block ASP.)

Is it chattering or what?. Is it turning taper, moving in the chuck, flexing in the bearings or is it simply badly adjusted gib strips. It could just be a blunt tool pushing the work away.

If it is actually that floppy I think one may well be outside the scope of a forum like this. Not that there isn’t the expertise, but its in danger of getting a little long winded.

I would suggest you make a list of all the joints” in the system – saddle gibs, x slide gibs, tool post, tool boat to post, tool to holder etc. Adjust and square each and every one and check with a DTI to see if there is improvement. When you find an improvement its worth taking a trial cut.

I’ve just been through this pain, because my 2 year old Chinaman suddenly started to misbehave. It was turning perfectly straight using tailstock support, but taper with inconsistent sized cuts (occasionally) without support.

Basically a microscopic chip of paint was on the gib strip and prevented it from adjusting properly. So with a bigger cut the clearance allowed the slide to rock, but not on a smaller cut. That sorted the inconsistency, but it didn’t sort the taper.

Working on the basis that if its cutting straight with the tailstock support. but not without, its got to be the way the work is held. Chuck or bearings. Change chucks and try. Still the same. Got to be bearings.

£156 saw me the proud possessor of a pair of P5 grade precision bearings and the machine is fine again. Actually it is stunningly good and is turning straight to 5 hundredths of a thou in 8″.(for the time being – not bad for a cheap old Chinaman. My mike doesn’t go below hundredths)

So its just a matter of working logically though the machine, altering one thing at a time until you get it right.

Above all don’t get tempted to dodge about following this and that advice, which is what will happen if you keep this on forum. Martin I am sure has it taped – stay with him and just plod though it logically and you’ll find the problem quite quickly.

A lathe after all is not a very complicated thing.
17 April 2010 at 00:08 #50788
Ian S C
Participant
@iansc
mgj, you’v got a fancy mic if it reads 1/100th of a thou, sure it’s not 0.0001 1/10, even thats better than most modellers who’s mic reads 0.001 or one thou,you probberbly slipped a digit some were. Ian S C
17 April 2010 at 00:35 #50789
Frank Dolman
Participant
@frankdolman72357
     At the risk of going even further off-post, I would be interested to hear from

   Meyrick whether he has had a chance to do a ‘forensic’ on his old bearings. It

   seems to me that they must have been well made of bad material since they

   performed very well but had a short life. Perhaps some Icelandic dust got at

   them
17 April 2010 at 09:03 #50800
mgj
Participant
@mgj
Its a Mitutoyo that reads to 5 places of decimals.

3 places is thou. 4 is tenths and the 5th is hundredths. It reads to 1/2 hundredths. So does my M&W 1-2″. I ve been a bit casual about figures lately (!) but 5 places is hundredths.

Metric they read to .001mm

I admit setting the lathe up like that was a bit of luck. I’d have settled for 1/2thou over 8″, but I popped a bit of shim in and torqued it down and that’s how it came out.

The forensics. The bearings were as the Chinese adjusted them, and they are oil lubricated. There’s the usual little collector slot and the oil level has been OK. Looks to me as if there had been a misalignment of the wedge angle in the tapers, because you could see a narrow ring where the top surface had worn, and on the outer side of the race track the bearings appeared unworn. That would square with the symptom, which was taper under load – if you had near line contact – but no detectable runout.

The new bearings are excellent – mind you so they should be at that price.

Edited By mgj on 17/04/2010 09:05:30
17 April 2010 at 11:21 #50806
KWIL
Participant
@kwil
Looks like an expensive toy for such “accuracy”!
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