Myford super 7 taper turnin

[Allan BParticipant @allanb]

[Allan BParticipant @allanb]

So I have got my new toy installed, base was bolted down and leveled with an engineers level, lifted the lathe onto the base and raiser blocks, and then set onto leveling and setting up the lathe, and this is where the issues started.

I started by getting a true bar in the 3 jaw chuck, set a DTI onto it, and over the 100mm length had a difference of about 0.5mm so a bit of adjustment needed, I then leveled the lathe front to back with the engineering level, but still had a 0.3 difference along the length, I then tried to tweak the leveling jacks as described in the myford manual, the closest I managed to get was a 0.04 difference, but to do that it had twisted the bed so that the cross slide no longer moved smoothly down the bed.

Now on to my question, is there any adjustment in the headstock itself to true it up? I can’t seem to find anything in the manual or off Google search.

Allan

[LambtonParticipant @lambton]

Allan,

It is more likely that your 3 jaw chuck is a bit inaccurate than the headstock being out of line. 3 jaw cucks, even new ones, are not to be relied upon to hold work accurately. This is why many experienced operators use 4 jaw chucks or collets for accurate working.

You need to turn a piece of bar exactly as shown on pages 13 & 14 "Checking The Levelling" of the handbook.

Do this very carefully taking very light cuts "levelling" the lathe accordingly..

It is best not to disturb the headstock casting. .

[BazyleParticipant @bazyle]

How tight is the saddle on the bed? With other slides locked of course, is the measurement point close to the middle of the saddle?. If you have a DTI hanging off a holder on the front of the toolpost any rotation of the saddle about a vertical axis due to the thou of clearance on the gib will be exaggerated.

You do not need to take cuts at least initially. If the 'test' bar is of consistent diameter you can set one end dead true in the 4 jaw or in the 3 jaw with shims of beer can then set the outer end true regardless of cross slide setting. Then you know it is in line with the spindle and can measure your offset taking into account backlash in the saddle twist. With the DTI set on the outer end and the bar rotated to max or min offset point you can observe the effect of shimming.

[Allan BParticipant @allanb]

Thanks both for your input, makes sense so will have another play tomorrow, didn’t take into account the 3 jaw being so far out.

And for reference the test bar I am using is a pre manufactured test bar, so is should be round, and I have checked it with a micrometer and it reads a true diameter the full length.

Allan

[ASFParticipant @asf]

+1 for the saddle maybe being a little sloppy.

That was a problem with my S7

IIRC the rear bed face had a little wear and also mine did not have all the shims between the saddle and rear saddle strip! They just left the bolts loose… so it could float around as it wanted.

[roy entwistleParticipant @royentwistle24699]

Allan B You cannot check for round with a micrometer the bar could be lobed like a twenty pence piece ( uk )

[Allan BParticipant @allanb]

I wasn’t checking for round with the micrometer, just that it was the same diameter along the same plane meaning it was usable as a test bar, it should have been as that is what it was sold as, but I have had at check just in case

Allan

[KWILParticipant @kwil]

Allan B

Where are you located? Is you test bar just cylindrical or is it on MT2 taper?

[Allan BParticipant @allanb]

I’m in the middle of Cheshire, just outside Northwich.

The test bar I have is just cylindrical with a centre mark in each end for setting the tailstock up, that will be the next trial by fire lol

[HopperParticipant @hopper]

The turning test is the best and easiest way of setting your lathe up. What you see is what you get. That's why the Myfrod manual recommends it as the final test, and as a complete substitute for leveling if no engineer's level is available. Holding a ground test bar in a chuck introduces all kinds of errors. Save the test bar for setting between centres to adjust the tailstock, after the bed has been set up.

You have to remember too that on an old or worn lathe, there will be wear on the bed shears that will throw out the readings on an accurate level. Hence the handiness of the turning test on old machines.

That said, yes there is adjustmemt on the head stock. Two jacking screws at the front of the headstock and four hold down bolts inside the headstock box casting. But you want to have eliminated all other possibilities before messing with them.

What sort of condition are your headstock bearings in? More than the regulation half a thou or so of up and down movement of the spindle measured at teh collar behind the chuck, while you yank up and down on a piece of 12" long bar held in the chuck will affect alignment too. (Another reason the turning test is best: it takes into account any slack in the bearings that allows spindle to move under cutting load conditions.)

Edited By Hopper on 07/02/2017 23:46:51

Edited By Hopper on 07/02/2017 23:48:21

[Allan BParticipant @allanb]

Thanks for that info Hopper, I thought there must be some adjustments in there somewhere, but as you say it’s a last resort, and I now have a lot more checks and info to go with before I get to that point.

Allan

[ASFParticipant @asf]

As far as I am aware, those two `jacking screws` are thrust screws that push the headstock to the rear shear face. Not for adjustment.

I would guess scraping would be required to change that setting?

[DMRParticipant @dmr]

As ASF says, the headstock screws mentioned are not adjusting screws! I get the impression that you are short of a a S7 manual? I am only about 15-20 miles from you and have sent you a PM.

[Allan BParticipant @allanb]

I have got the manual for the screw cutting gearbox but not the lathe itself at the moment unfortunately

[Tony Pratt 1Participant @tonypratt1]

Posted by Allan B on 07/02/2017 18:51:31:
Thanks both for your input, makes sense so will have another play tomorrow, didn't take into account the 3 jaw being so far out.

And for reference the test bar I am using is a pre manufactured test bar, so is should be round, and I have checked it with a micrometer and it reads a true diameter the full length.

Allan

Allan,

Many of us have been here before on this forum, firstly the run out or otherwise of your chuck will have absolutely no effect on how the lathe does or does not turn parallel.

Please get a copy of the S7 manual before doing anything else & to be honest jacking the headstock should not be necessary at all

Tony

[HopperParticipant @hopper]

Posted by Tony Pratt 1 on 08/02/2017 22:05:53:firstly the run out or otherwise of your chuck will have absolutely no effect on how the lathe does or does not turn parallel.

 

Absolutely, but it will hold his ground test bar cockeyed and give a false reading as he runs his dial indicator up and down the length of it, as he has been doing. Hence, another reason the turning test is the ultimate test; chuck runout does not affect it.

Edited By Hopper on 08/02/2017 23:50:25

[HopperParticipant @hopper]

Posted by ASF on 08/02/2017 18:36:50:

As far as I am aware, those two `jacking screws` are thrust screws that push the headstock to the rear shear face. Not for adjustment.

I would guess scraping would be required to change that setting?

Yes, their operation depends on scraping the headstock mating surface, or in a pinch adding thin shims to one end of the contact area. Then the screws jack, or thrust, the two surfaces togehter firmly to set alignment. As has been said, it is unlikely this will need adjusting and all other possibilities need to be elimiinated and double eliminated first.

It would pay, too, to measure the bed wear on the front shear, both in the vertical and horizontal planes. More than .005" is cause for serious concern and will affect parallel turning etc. It is easily measured with a 0-1" mike for the vertical and a 1-2" mike for the width measurement. The bottom outer surface of the shear is relatively unworn as it takes little or no cutting forces so can be used as a reference surface. Ditto the front surface of the front shear. It is the top of the shear and the inner vertical surface of the front shear that take most of the operational load.

[Tony Pratt 1Participant @tonypratt1]

Posted by Hopper on 08/02/2017 23:49:54:

Posted by Tony Pratt 1 on 08/02/2017 22:05:53:firstly the run out or otherwise of your chuck will have absolutely no effect on how the lathe does or does not turn parallel.

Absolutely, but it will hold his ground test bar cockeyed and give a false reading as he runs his dial indicator up and down the length of it, as he has been doing. Hence, another reason the turning test is the ultimate test; chuck runout does not affect it.

Yes sorry missed that bit! Get a manual & as you say the turning test is the way to go.

Tony

[Allan BParticipant @allanb]

Thanks all for your input, I now have a copy of the manual thanks to DMR, so I’m going to print it out this morning, then I have got the day today to have a good play with it and will report back later.

Allan

[Martin KyteParticipant @martinkyte99762]

I really suggest you don't start messing with the headstock until you have absolutely determined you have a problem.

Level the lathe with a turning test as specified in the manual, making the necessary adjustments using the jacking screws at the tailstock end. Unless you have a precision machine level you will not be able to set the lathe to turn parallel by that method. Building levels are just not sensitive enough to do the job. Even using a precision level a turning test and a mic is advisable as a final check.

I recently took delivery of a refurbished Super 7 and did set it up with a precision level (0.0002"/10&quot and did a turning test as a final check. I could detect no difference in diameter over the 4" test piece using my best digital mic.

Building levels are good to get in the right ball park, precision levels are a very good short cut and the turning test is the final arbitor.

[Allan BParticipant @allanb]

OK so a bit of an update, so after leveling up again with the engineering level, then putting a piece of 25mm bar into the chuck, the first test cut gave me a difference of 0.03mm over a 100mm length, so a small adjustment later I now have a difference of 0.00mm over the 100mm length.

Next went back to my test bar, between two centres, from the headstock to the tailstock, using the DTI, I started with a difference of 0.04 over the 125mm length, so again a bit if adjustment later got that down to 0.00 over the length, unfortunately I haven’t got a faceplate yet, so had to mount a test piece in the 3 jaw chuck and the tailstock, did a fine cut and again got a 0.00mm difference along a 100mm length.

So after all that I do believe I have finally got the lathe set up 😀

So next jobs are to sort out the drainage for the coolant system, and then fit the DRO, then I can carry on with building a model horizontal mill engine 😀

Thanks all for all your help.

Allan

[HopperParticipant @hopper]

Well done mate. Job's good at those measurements. Enjoy your lathing!

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