Myford set up.Time to get it right.

[paul coombsParticipant @paulcoombs24988]

[paul coombsParticipant @paulcoombs24988]

Hi Guys.Decided that I need to check accuracy of my ML7(serial 41733)

I knew it had runout.Bolted to floor on Myford stand, with correct mounts.I levelled the bed with engineers level.

despite my best efforts, the runout didnt really alter, it stayed about .9mm

then I noticed that by grabbing the test bar,I could get up to 1mm movement on the test bar.I think the movement is behind chuck.Im presuming, I have worn bearings?Any input grateful thanks.

[JasonBModerator @jasonb]

A better test would be with the test bar in the spindle MT socket as it would seem a lot of 3-jaw chucks have runout that is far greater than mine.

[paul coombsParticipant @paulcoombs24988]

Not sure what MT socket is? However, that wouldnt explain the movement though would it?

[clogsParticipant @clogs]

thats an awful lot of play…

is the chuck secure on the shaft, jaws tight on the bar and the bar is a good way in…..?

can you get the DTI on the back end of the main shaft….or near enough…

with the test bar in the chuck and a good tug will show up any play……

not sure of the lathe design but aren't these brearings adjustable…??.

[Martin KyteParticipant @martinkyte99762]

Posted by paul coombs on 26/09/2020 17:16:11:

Not sure what MT socket is? However, that wouldnt explain the movement though would it?

The spindle taper is 2 Morse same as your test bar.

Take the chuck off, clean the spindle taper well and insert the test bar. Now do your test again. Do ensure you are just pulling the test bar and you do not have your other hand on the cross slide. Ideally put your other hand in your pocket.

regards Martin

[paul coombsParticipant @paulcoombs24988]

Posted by clogs on 26/09/2020 17:19:35:

thats an awful lot of play…

is the chuck secure on the shaft, jaws tight on the bar and the bar is a good way in…..?

can you get the DTI on the back end of the main shaft….or near enough…

with the test bar in the chuck and a good tug will show up any play……

not sure of the lathe design but aren't these brearings adjustable…??.

Yup chuck is tight, and bar well located.I put DTI on back of shaft, couldnt see any play

[paul coombsParticipant @paulcoombs24988]

Posted by Martin Kyte on 26/09/2020 17:29:29:

Posted by paul coombs on 26/09/2020 17:16:11:

Not sure what MT socket is? However, that wouldnt explain the movement though would it?

The spindle taper is 2 Morse same as your test bar.

Take the chuck off, clean the spindle taper well and insert the test bar. Now do your test again. Do ensure you are just pulling the test bar and you do not have your other hand on the cross slide. Ideally put your other hand in your pocket.

regards Martin

thanks Martin.

[Tony Pratt 1Participant @tonypratt1]

Holding a bar in your chuck doesn't tell you anything about the lathe itself only that the 3 jaw chuck is not running true at that particular diameter.

Tony

[not done it yetParticipant @notdoneityet]

’The proof of the pudding is in the eating’ as they say. How does it perform when cutting?

Are you measuring along the bar or while rotating it? Nearly a mm is excessive.

[Howard LewisParticipant @howardlewis46836]

Agree with Tony Pratt.

To check the Mandrel, the test bar has to be seated in the clean 2 MT taper of the Mandrel. Using a chuck introduces another two possible sources of error, so that the result says nothing about the Mandrel.

Holding an absolutely parallel bar in a three jaw chuck could result in any reading of run out, from Zero to 0.036", depending on how good the Mandrel and the chuck happen to be, based on the ones that I have seen

Howard

[paul coombsParticipant @paulcoombs24988]

thanks guy.It doesnt perform that great when cutting,measured whilst rotating.With the excessive movement, when I gripped the test bar,Im thinking it might originate from spindle/bearings

wiil retest with mandrel, without chuck on monday!

[JasonBModerator @jasonb]

It is most likely bearings but a badly bell mouthed chuck could also be allowing some movement of the bar that is why it is best to remove the check from the equation at this stage and put the bar into the spindle's socket

[SteviegtrParticipant @steviegtr]

This guy on youtube does a lot of work to the myford lathes. Worth a watch.

Steve.

myford mods

[HopperParticipant @hopper]

You need to put the plunger of the dial indicator on the lathe spindle directly behind the chuck then yank your test bar up and down and side to side. If you still have more than one thou of movement there, you have loose headstock bearings.

[John OlsenParticipant @johnolsen79199]

The ML7 has bearings that can be adjusted by pealing off shims from the stack. I'm no expert on how to do this but you should be able to find the information somewhere.

John

[paul coombsParticipant @paulcoombs24988]

thanks for all the replies guys.Its now blatantly obvious, that accuracy and true running begins at the spindle (bearings) and that has to be origin of accuracy checks.

I will remove chuck, re check the spindle with gauge.Im kinda hoping ill find thats where the issue is.

I watched the youtube guy many times.Really great info.He actually admits to using a second hand spindle and bearings,which he replaced almost immediately.I dont care about spending money on my lathe.I love using it, and any investment only protects it value anyway.

I bet that a lot of the used ones, on offer (Ebay etc) are well used and worn.

[JasonBModerator @jasonb]

Probably best to check the whole lathe over for ware as if the bearings have gone that far things like bed and tailstock may also need work which could end up costing a lot more than lathe would be worth financially.

[Maurice TaylorParticipant @mauricetaylor82093]

Posted by paul coombs on 27/09/2020 07:57:18:

thanks for all the replies guys.Its now blatantly obvious, that accuracy and true running begins at the spindle (bearings) and that has to be origin of accuracy checks.

I will remove chuck, re check the spindle with gauge.Im kinda hoping ill find thats where the issue is.

I watched the youtube guy many times.Really great info.He actually admits to using a second hand spindle and bearings,which he replaced almost immediately.I dont care about spending money on my lathe.I love using it, and any investment only protects it value anyway.

I bet that a lot of the used ones, on offer (Ebay etc) are well used and worn.

I would be hoping the spindle and bearings were alright with no play and the chuck was no good..Takes a few minutes to fit new chuck.If the chuck is bell mouthed it would cause the play with that bar in it.

[paul coombsParticipant @paulcoombs24988]

Ok guys finally managed to find some time.Today I removed chuck and checked run out on spindle as suggested.No matter what I did I couldnt get more than 1 thou runout.Happy with that.I did notice that the spindle bearing caps were not pulled down tightly.I pulled them down and as I thought the spindle locked.Then backed off quarter turn and the spindle runs freely.

Im presuming that my issue with run out is the chuck.Pic of it attached along with 2 jaws.It doesnt state a make,but is stamped "Specially made for Myford ML7" If I have to replace it, I presume I will need to reuse the back plate.Any advice on removal of back plate.I removed the Allen Keys.Not sure of what is required next?

Edited By paul coombs on 03/10/2020 15:53:31

[paul coombsParticipant @paulcoombs24988]

Edited By paul coombs on 03/10/2020 15:52:02

[Martin of WickParticipant @martinofwick]

Paul,

The 'made for myford special chucks' do not have a backplate in the conventional sense, what you are assuming is the backplate is in fact an integral but threaded part of the chuck, as shown in the picture below.

You take it apart by undoing the socket screws and splitting the two parts with a hide mallet.

if inconsistent or large TIR is an issue for you the easiest route is to purchase a new chuck (of the non integral variety) and new unmachined backplate, machine said backplate on your lathe to mount your new chuck. dont expect less than 3-6 thou TIR as a repeatable error (you might get better – just don't expect it!).

Your other more time consuming choices are:

determine the cause of the error –

is it badly worn jaws – if so you could attempt a jaw re-grind to minimise the runout, you should be able to reduce it slightly but not remove it entirely (google / utube is your friend here)

worn or damaged scroll – you are stuffed – you can tell by inconsistent runouts at differing diameters if runout is a problem you will need a new chuck

deformed , (ie bent off axis) chuck mount (hard to believe but entirely possible- that was the problem with the one in the picture) – you can tell by putting a dti on the back of the chuck and check for axial wobble – you may be able to effect some sort of correction by shimming the downside on the rear chuck part.

[paul coombsParticipant @paulcoombs24988]

Thanks for that Martin.Im off to buy a new chuck right now!

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