How long will a 3 Jaw chuck last

[Kim GarnettParticipant @kimgarnett94824]

Hi

Having serviced my 3 jaw chuck I was wondering How long they are supposed to last. Now I have 2 3 jaws chucks one is getting on for thirty years old and the other is 22 years old on two different lathes both can repeat 0.05mm runout at 110mm from the end of the jaws on a test bar however the zero position (where you tighten with the key) on both chucks has moved. I have looked after them over the years and I don’t abuse them but they have done a lot of work over this time. is it time to look for a new chuck as nothing last for ever or will they keep going ?

[bernard towersParticipant @bernardtowers37738]

Personally I would machine a petal plate and regrind them first it can transform them.

[HopperParticipant @hopper]

0.05.mm (2 thou) runout at 110mm from the jaws? You won’t find a new chuck that good. Most are lucky to be that good immediately next to the jaws.

If you want better, use the 4 jaw chuck. Three jaws chucks are not intended for ultra precision but for quick set up that is “close enough” for general work.

[Paul LousickParticipant @paullousick59116]

The Pratt Burner chuck on my lathe is 50+ years old and still works OK. Wear depends on the amount and abuse that it has received.

Chuck jaws can be ground to correct runout if a problem, using a special spreader/spider to clamp the jaws in the normal working position. Lots of videos on Youtube showing this.

[Thor 🇳🇴Participant @thor]

Hi Kim,

My Emco 3-jaw is almost 50 years old and is still working to my satisfaction, if your chucks has a runout of 0.05mm you have good chucks that will last for many more years.

Thor

[David George 1Participant @davidgeorge1]

The wear on chucks can have diferent effects depending on what you turn on your lathe or use a grinder etc and how you use the jaws as if you hold longer pieces of material which loads the full width of the jaw or grip short lengths which in effect tip the jaws giving a cow mouthed effect to the jaws. Also if you use the chuck on a particular diamiter the scroll will wear more on that diamiter than less used diamiters. I recently tried to grind the original chuck on my lathe as it was cow mouthed and found that at the diamiter i ground through the jaws was not bad when i changed to a diferant diamiter there was a significant error both on larger and smaller diamiters. I presume that the chuck scoll and jaw slide areas had worn unevenly.So put the chuck which is from around 1950 back in the cupboard having spent a couple of days on stripping, cleaning and making a clover leaf plate to allow me to grind the jaws. I regulary clean and lubricate my 5 year old Pratt and Burnherd which will repeat to less than a thou depending on material being held. I have a hardened and ground 3/4″ dowel 4″ long which i use to check for runnout regulary as it is possible to get a foreign body either into the chuck spindle location or scroll etc.

David

[Brian WoodParticipant @brianwood45127]

Hello Kim,

How long is a ball of string? Your question is in the same sort of category!

I still use regularly the 3 inch three jaw Bernard chuck that came with the ML4 lathe my father bought in 1945. I lapped the jaws true many years ago to correct bell mouthing and it is still a decent chuck, maybe not in the 2 thou range but then it might never have been.

By contrast, the five inch three jaw chuck that was original Pratt equipment on my 1947 made Churchill was completely shot. The scroll had 50% of the first turn missing and beyond that it was distorted, the jaw guides were sloppy and there was another area of scroll distortion about halfway through. Repeatability was dreadful. This chuck had been given a very hard life indeed.

Just delight in your good fortune and the care you have given it over the years.

Brian

[noel shelleyParticipant @noelshelley55608]

All the chucks I have are over 50 years old, all PBs and will see me out. Noel

[Kim Garnett]

On 11 October 2024 at 21:14 Kim Garnett Said:

 

Having serviced my 3 jaw chuck I was wondering How long they are supposed to last. …

Depends, depends, depends!

Ask the accountant in a busy old-school lathe shop doing piece-work round the clock circa 1914, and he’d probably say 3 to 5 years.   His experience is of chucks worked hard in a rough environment, by many different operators, all of whom are incentivised to work flat-out for hours on end.   Operators don’t mollycoddle the equipment, and there will be accidents – like dropping the chuck onto a concrete floor.   And chuck life will be reduced considerably if the work-holding requirement tends to bell-mouth the jaws, or requires lots of jaw movement that wears the scroll.  Repetition work concentrates wear in one place.  Grinding does a lot of damage, as does whacking the work with a hammer, or nothing but heavy interrupted cuts.   In a large workforce, chance are a few men will be of the ‘tighter the better’ persuasion, who insist on putting a pipe extender on the chuck key and then hammering it!   Maintenance is a major factor – if any!  Chucks that are cleaned and oiled last longer than those choked with swarf.   From a cost perspective, it’s often cheaper to replace chucks than it is to pay men to regularly clean them.

How long a chuck lasts in a professional jobbing work-shop depends on how hard and often it’s used.   On average, compared with the same chuck doing 1914 style piece-work the chuck will have a relatively easy life, or maybe not!  Still vulnerable to abuse during rush jobs, poor maintenance.  My local machine shop used to list their tools on the web.  About 30 CNC machines, plus a manual lathe.   Chances are the manual lathe is hardly ever fired up, in which case it’s chuck will last forever!

I guess Model Engineering workshops are typically lightly loaded and, apart from during the learner driver phase, our tools are  egged on rather than thrashed.  (Anyone thrashing a Chinese hobby lathe, please STOP!)  Bad news, ME chucks are more likely to be called on grip work in a way that causes bell-mouthing, or stresses the jaws and scroll.    Good news, there also more likely to be kept clean.   A mass of different factors, making it impossible to generalise beyond “should last decades”.

In an amateur workshop, I suggest chucks are only a concern when they can’t do the job without annoying the operator.  Even then not necessarily the end because worn jaws can be re-ground or replaced.  The killer, I think, poor results due to worn jaw slots or a damaged scroll.

As a skilled operator will be able to get good results out of a not too wonky chuck, it’s down to the individual to decide when replacement is necessary.   My advice to Kim is only he can decide when it’s time to change.   Whilst the forum can offer suggestions, we have no idea how well or badly Kim’s chuck is performing.   0.05mm run-out is good, but maybe repeatability is poor?

Another comment:  Model Engineers tend to measure tool life in elapsed years.   This is misleading.  Better to measure run time.  A 1948 Myford that does an hour cutting every alternate Sunday should be close to being in ‘as new’ condition.   A 1948 Myford that cut for 4 hours a day year on year will have had new bearings, bed regrinds, replaced chuck etc and was probably scrapped in the last century.   Condition depends on the amount of work done, not chronological age.

Dave

[Kim GarnettParticipant @kimgarnett94824]

Hi thanks for the replies both chucks are good if tightened from the new zero position but not so good from the original zero position between 0.1 to 0.15mm on one and up to 0.2mm on the other  which would indicates wear which is not unexcepted for the age of the chucks and the amount of use they have had. When I was young I was always told to tighten on the zero position as this was set by the manufacturer when the chucks were made and where the chuck would be most accurate, which I have done so unable to state how accurate there were for tighten from other positions as I have never done it until now.

Kim

[HopperParticipant @hopper]

<p style=”text-align: left;”>Well if tightening from the new zero keyhole works for you, no need for a new chuck.</p>
 You may have worn out the original zero position bevel gear and it is skewing the scroll plate or something like that when tightened.

Have you taken the chuck apart and cleaned and inspected it? They do need the swarf cleaning out and the grease repacking in the bevel gear cavity every decade or so. Best to reassemble the parts in same positions as they came from.

[VicParticipant @vic]

An old machinist told me “three jaw chucks are for rough work, if you want accuracy use a collet chuck”. I suppose it depends on what you’re doing? I use a collet chuck quite a lot as it doesn’t mark small round stock like a three jaw will, plus the accuracy of course.

[Kim GarnettParticipant @kimgarnett94824]

Hi Dave has made some good points as when I was in industry I have bought and replaced quite a few chucks in my time on different machine tools over the years CNC and Manual and the life depended on the amount of work going through the machine the quality of chuck used and the operator, on manual machine machines manly the operator as

even good chucks if used badly will not last. I can remember one lathe where I bought 2 Pratt chucks for a lathe in 4 years replacing every 2 years the amount of work going through that machine was far less than my lathes do. My lathes do quite a lot of work but not abused. I have been very happy with both chucks on my lathes and if I replaced them I will not be upset as I have had my monies worth out them both.

Kim

 

[Hopper]

On Hopper Said:

0.05.mm (2 thou) runout at 110mm from the jaws? You won’t find a new chuck that good. Most are lucky to be that good immediately next to the jaws.

If you want better, use the 4 jaw chuck. <b>Three jaws chucks are not intended for ultra precision but for quick set up that is “close enough” for general work.</b>

Disagree with the emboldened, above.  They are perfectly appropriate for turning work pieces as long as all the turning operations are completed without removal/replacement from/to the chuck.

Any centres I use in my lathe are made in the 3 jaw – as good as, or even better than, a centre fitted to the spindle taper.

[HopperParticipant @hopper]

Yes indeed. Close enough for precision work if all done in one setting.

[JasonBModerator @jasonb]

Also depends what you want to do with it, if it is making models both steam and IC then they are precise enough

[HopperParticipant @hopper]

What you do have to watch out for on old chucks is bellmouthing, which may give only a small amount of runout but it moves around as the job is not firmly held. So even turning in one setting results in some varied results.

[peak4Participant @peak4]

For some reason my original reply has vanished.
Essentially, so long as the jaws aren’t bellmouthed, as mentioned above, if you need greater accuracy/repeatability, you could always make an adjustable backplate, so that your setup replicates a Griptru.
I’m still using Taylor chucks which are likely as old as me.

Bill

[Graham MeekParticipant @grahammeek88282]

Hi Kim,

Most standard Chucks have a tolerance of 0,025 mm at 25 mm from the chuck jaws when new. Your chucks are well within this range. As regards the the preferential jaw screw moving, this is common.

Personally I would leave well enough alone.

Regards

Gray,

[Chris CrewParticipant @chriscrew66644]

Why are people obsessed with Rolls-Royce or NPL standards in a back shed amateur workshop? It beats me! If I can get within 001″ on anything I am delighted, but that’s just me as a back shed dabbler, others may think it’s nonsense and they are welcome to their opinion. I have a cheap Chinese 4-jaw 8″ self-centring chuck that indicates .0015″ a foot out from the the jaws on a piece of 0.625″ PGMS and will repeat this. What more do you want in a back shed?

[Hopper]

On Hopper Said:

 

If you want better, use the 4 jaw chuck. Three jaws chucks are not intended for ultra precision but for quick set up that is “close enough” for general work.

3 jaw chuck with bored soft jaws will be as accurate as anything, if not better.

 

I hardly ever bother a 4 jaw chuck.

 

Jimb

[bernard towersParticipant @bernardtowers37738]

surely a 4 jaw is used for a completely different scenario?

[Vic]

On Vic Said:

An old machinist told me “three jaw chucks are for rough work, if you want accuracy use a collet chuck”. I suppose it depends on what you’re doing? I use a collet chuck quite a lot as it doesn’t mark small round stock like a three jaw will, plus the accuracy of course.

Is that all he said?  Surely an over simplification, I’d qualify it thus:

• If a job can be completed without removing it from the chuck, then a 3-jaw will do much better than ‘rough work’, even if it’s distinctly wonky.   The reason is the lathe cuts relative to the spindle axis, so provided the job isn’t moved, the result will still  be true.  Not as good as turning between centres, but still very acceptable.
• The problem is what happens when the work is removed from the chuck for some other operation and has to put back later for more cutting.   Then, because the 3-jaw has poor reset characteristics, the job is likely to be positioned relative to the spindle axis in a different way, so any subsequent cutting is misplaced relative to the first.  Bad!
• Rule: if a job has to be taken out of a 3-jaw and replaced in it later for more cutting, don’t use a 3-jaw!   But they’re fine for one-off turning, and might be ‘good enough’ if the later cuts don’t have to align highly accurately with the first.
• I wonder why ‘old machinist’ didn’t mention 4-jaw chucks?  They can be reset highly accurately with a DTI. Problem is that resetting is quite slow, but I say it’s essential to own one.
• If the operator needs fast no-skill resetting, then collets are the answer.   Work just plugs into them, very little fiddling required for almost instant accuracy.  The disadvantage is the need to own a lot of pricey collets:  each size only grips over a small range of diameters.

Which is best depends on the workflow.  It’s mostly about speed.

Most of what I do is best done with a 3-jaw because quick and general purpose suits my common requirement for simple basic turning.  If I have to reset, work can be encouraged into better alignment in a 3-jaw by tapping it with a hammer and checking run-out with a DTI, though I’m not sure hammering is good for the chuck or bearings.

The 4-jaw comes out when I need to reset the same work repeatedly, or when I want to turn ovals or cams – 4-jaws are very versatile.  The 4-jaw is used roughly 10-20% of the time in my workshop because it takes me a while to set them up accurately.  Practised operators set 4-jaws up remarkably quickly to the extent that some prefer to use only them, not bothering with a 3-jaw at all.

Collets suit a particular type of workflow – one in which a job develops by being transferred repeatedly between a few different machines.  Above a certain number of swaps, chucks become tedious and error prone.  Watch and clock makers use collets all the time.   I rarely do that type of work so buying a set of work-holding collets for my workshop is a waste of money.  I did cough up for an ER collet holder, because it allows me to use collets needed for my mill.

How about a 6-jaw chuck?  I believe these are good for gripping thin walled pipe.  Some workshops do little else.  On the rare occasions I work on thin pipe, I make a stub mandrel out of wood to connect the chuck to the pipe, and support the other end with a large diameter cone live centre.   A 6-jaw would be faster and easier, but a serious waste of money in a workshop that only turns pipe once in a blue moon.  Unless I’ve missed something else 6-jaw chucks are good for?

Dave

 

[JasonBModerator @jasonb]

Hoppers post suggest it is needed for precision holding of round stock. But then again my 3-jaw is good for 4/10th” runout

Mine 4-jaw only tends to get used for round stock if it is too big for the 3-jaw, as that is 125mm compared to the 160mm 4-jaw. or round items that need to be held eccentric. Otherwise the holding of non round scenario comes into play.

[not done it yetParticipant @notdoneityet]

I suspect that ‘between centres’ turning was used by far more hobbyists until the later years of the last century.  As long as the lathe was set up to cut parallel, parts would be started by initially cutting the centres then mounting between them for accurate, concentric turning operations.

No problem if the centre in the 3 jaw chuck was needed to be removed before the workpiece was completed – just remount the centre in the 3 jaw and give it a quick skim, to centre it perfectly once again, then continue with the workpiece between centres.  Likely no need for a more expensive (at the time) 4 jaw chuck, as most ‘offset’ work could be accomplished with use of a face plate.

[Author]

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