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Myford S7 Cutting Barrel Shaped Cylinders

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Hopper24/05/2020 09:41:04
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Posted by Michael Gilligan on 24/05/2020 09:34:20:
Posted by Hopper on 24/05/2020 09:27:13:
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Or just take a continuous cut over the 4" length of the 1" diameter bar. It does not take that long. And gives a full reading of what is going on.

Yes, using a level on a worn bed is fraught with danger […]

.

I agree completely, Hopper ... but isn’t that ‘where we came in’ ?

MichaelG.

________

Mike wrote :

I have adjusted the feet to ensure the ends of the cut are the same diameter, but having run the cutter from right to left each time using the slowest power feed, I found that the middle of the cylinder is consistently around 0.0015" (1.5thou) oversize. I ensured that the cutter was removing metal from the length of the bar on each pass.

I was refering to Jason's suggestion of a three-collar test bar in the previous post.

Pete Rimmer24/05/2020 09:42:44
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The saddle and tailstock run on different parts of the flat way, the tailstock will never wear the chuck end and the saddle won't appreciably wear the tailstock end, so you can actually put a level on either end quite confidently as it will sit on the un-worn parts both ends unless the wear is particularly heavy or the top surface damaged with dings and burrs.

This doesn't stop the saddle rotating on the worn bits but it does give you a baseline to start your measurements. from.

Hopper24/05/2020 09:46:57
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Posted by Pete Rimmer on 24/05/2020 09:42:44:

The saddle and tailstock run on different parts of the flat way, the tailstock will never wear the chuck end and the saddle won't appreciably wear the tailstock end, so you can actually put a level on either end quite confidently as it will sit on the un-worn parts both ends unless the wear is particularly heavy or the top surface damaged with dings and burrs.

This doesn't stop the saddle rotating on the worn bits but it does give you a baseline to start your measurements. from.

But the saddle runs on the full width of the top horizontal surface of both ways. So saddle wear is full width. Problem is the front way way takes most of the load and wears more than the rear way. Unless the Super 7 carriage is different from the ML7? (It doesn't appear to be but I dont have one to hand to check.)

I suppose you could measure the actual wear on the bed and shim the level accordingly??? Or build a "sled" that referenced off the relatively unworn underside of the shears where the lift plates run and sit your level on that??? Tricky though.

 

Edited By Hopper on 24/05/2020 09:57:47

Michael Gilligan24/05/2020 10:11:24
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Given the bed wear that Mike has already measured ... I would say the measured barrel is entirely reasonable.

It’s a worn lathe, giving ‘worn lathe’ performance.

MichaelG.

Michael Gilligan24/05/2020 10:13:32
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Posted by Hopper on 24/05/2020 09:41:04:

I was refering to Jason's suggestion of a three-collar test bar in the previous post.

.

So perhaps my comment should have been addressed to Jason

JasonB24/05/2020 10:19:24
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"It’s a worn lathe, giving ‘worn lathe’ performance."

Agree with that Michael

Advantage of the bobbin type test is your tool stays nice and sharp doing two ( or 3) 1/4" wide cuts so giving a more consistent reading than turning a whole long length. You can also make it with "rings" loctited to a shaft and keep that for testing setup and simply heat the rings off when too small and fit new, saves wasting lots of bar.

Even using a between ctrs test piece could be a problem if the tailstock had droop or wear to match that of the bed, one of the downsides of buying old machines I suppose.

Edited By JasonB on 24/05/2020 10:20:22

blowlamp24/05/2020 10:32:55
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In practice, it's not that big a job to give the vertical shears a 'lick' with the scraper to remove the worst of the wear.

You wouldn't get an award for "Engineering Excellence", but you could do it without dismantling the carriage and even use said carriage to check for tight spots as you progress.

What's to lose? smiley

Martin.

Hopper24/05/2020 10:40:16
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Posted by blowlamp on 24/05/2020 10:32:55:

In practice, it's not that big a job to give the vertical shears a 'lick' with the scraper to remove the worst of the wear.

You wouldn't get an award for "Engineering Excellence", but you could do it without dismantling the carriage and even use said carriage to check for tight spots as you progress.

What's to lose? smiley

Martin.

If you have the requisite skills and scrapers and scraped straight edge and square for reference. And not if the carriage is equally as worn as the bed. (Usually the carriage is more worn than bed). For the average home shop worker I think it would better to try the very simple wide guide conversion and if the vertical wear is still a problem, pay for a regrind. It's a Super 7 so worth spending money to refurbish, given the outrageous resale price.

blowlamp24/05/2020 10:55:26
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Posted by Hopper on 24/05/2020 10:40:16:
Posted by blowlamp on 24/05/2020 10:32:55:

In practice, it's not that big a job to give the vertical shears a 'lick' with the scraper to remove the worst of the wear.

You wouldn't get an award for "Engineering Excellence", but you could do it without dismantling the carriage and even use said carriage to check for tight spots as you progress.

What's to lose? smiley

Martin.

If you have the requisite skills and scrapers and scraped straight edge and square for reference. And not if the carriage is equally as worn as the bed. (Usually the carriage is more worn than bed). For the average home shop worker I think it would better to try the very simple wide guide conversion and if the vertical wear is still a problem, pay for a regrind. It's a Super 7 so worth spending money to refurbish, given the outrageous resale price.

Yes, I did mention that in my first post. In my previous post I was thinking more of a 'get a bit more accuracy' type of fix without doing a complete refurb.

I've done similar myself using scraper, files, some ground stock and a little blue and it's surprising how well a simple bodge job can work.

Martin.

Hopper24/05/2020 11:01:38
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Blowlamp, yes such a "simple bodge job" could be better than nothing if wide guide is not an option. Good idea using gauge plate as a reference surface. Ive done similar with large section key steel before too. It's surprisingly flat (by bodge standards laugh ) And you could mike off the relatively unworn front shear.

But if I had an S7 I would spring for the regrind given the resale value and the quite nice lathe you would have as a result. Depend's on one's budget of course. And nobody's retirement fund is going gangbusters at the moment. (Unless you are Jeff Bezos or one of those guys.)

Edited By Hopper on 24/05/2020 11:02:48

Mike Donnerstag24/05/2020 19:27:10
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Firstly, I'd like to thank everyone who replied. I expect all of you have a greater engineering knowledge than I. I did a little toolmaking on my violin making course during 2012-2016 and have only been doing more at home since then, firstly in a severely limited way with a Myford cross-slide fitted to my woodworking lathe (!), then with the Myford S7 I bought at the start of last year, and more recently with the purchase of the Sieg SX3 mill.

I knew the Myford was an old lathe with an unknown amount of wear, but I thought it was a great price (£1500) for one with a gearbox and power cross feed. It’s from 1982-ish, so the saddle is already ‘wide-guide’. I’ll try to reply to everyone separately below, so please excuse me repeating myself, and apologies for anyone I've missed!

Pete Rimmer: The idea of compensating for an out of line headstock makes complete sense to me. If the axis is pointing towards the back right corner of the lathe and the front right foot is raised to compensate, in my mind at least this would explain the barrel shape. Just an idea: would an iron casting such as a lathe bed spring back to its original flatness, or thereabouts, confirming this? If so, I could see what happens when I slacken the two nuts at the right end of the bed.

Unfortunately, I don’t have access to a machinist’s level, but if there is anyone on here who could help, in the Lincolnshire area, I would be eternally grateful. Having said that, it seems that not everyone is in agreement that it would help identify the problem.

Graham Meek: I’ve been using a freshly sharpened piece of 3/16” HSS held very solidly in a tangential toolholder made by a very capable young chap who is head of the engineering workshops at Newark college. He has given me a great deal of help, that is, until he fell off his push-bike and broke his hip at the start of the year! Anyway, I made sure the depth of cut was the minimum necessary to remove metal from all the way along the shaft, between 1 and 2 thou. The tool cut very sweetly with no chatter on the mild steel bar (not sure whether it was leaded for free-cutting, but it cut well). The cutter was sharpened with no radius, but has retained its edge during the eight or so test cuts, giving consistent results.

I’ll try the ‘test bar test’ tomorrow (I’ve been solving lockdown relationship problems today – my own relationship that is - very tiring!!) using the (probably Chinese) 11” (including taper) MT2 test bar from eBay recently. It’ll be interesting to see what this shows. I’ll keep you updated on my findings.

My overhaul so far has really only covered the carriage. The bed wiper felt was completely missing when I purchased the lathe, so this was the first job I did last year, as well as removing, thoroughly cleaning and oiling the saddle. The underside of the saddle is quite scored. More recently I replaced one of the apron bearings, which was so bad it leaked oil from the apron sump. Apart from adjusting the bearings and giving the whole machine a good clean and oil, I haven’t touched the headstock.

I have completely ignored the tailstock so far in my setting up since replacing the apron, as I considered its alignment to be just another variable to contend with and confuse issues further.. though more on this below.

(By the way, I have your handwheel dial fitted that I purchased from Steve Tracey – great design and a fantastic bit of kit!)

Martin Kyte: I haven’t noticed any rigidity problems with the ER40 collet chuck, going by the lack of chatter. The cut has been very light; no more than 2thou.

Blowlamp: I’m coming to the conclusion that it may well be just bed wear that I’ll have to live with, until I dismantle everything and have the bed reground, which seems to be worth considering. The lathe is from 1982 and therefore already has the ‘wide guide’ saddle, hence my taking the measurements from the full width of the bed.

I have absolutely no experience with metal scrapers, even though I do own several blunt ones. Without someone who knows what they were doing, I’d be afraid of doing more damage than good.

To be continued...

Mike Donnerstag24/05/2020 19:27:30
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Continued from above...

Hopper: Yes, pretty borderline wear it seems. The lathe is a post-1972 wide-guide version. Regrinding may well be the answer if I need greater accuracy.

Not done it yet: Wouldn’t bringing the tailstock into play just add to the number of variables contributing to the problem? Or, would it definitively isolate the issue to the bed, thereby proving that the headstock alignment is not to blame?

JasonB: I could try taking a heavier cut, though I’m expecting chatter at the outboard end to confuse the measurements.

Michael Gilligan: You may well be right about the lathe bed just being worn, with a regrind the only way to increase accuracy.

To summarise…

I will try the MT2 test bar suggested by Graham Meek and turning between centres suggested by Not done it yet. If that doesn’t help identify the issue, I’ll have to decide whether to live with the inaccuracy, or to stump up for a regrind. Actually, the dismantling, transport and subsequent reassembly and alignment scare me more than the cost, which is within my budget.

Just an idea: If the problem is due to bed wear, would it be worth checking and adjusting the flatness of the saddle gib strip to ensure it is bearing on as much of the front shear of the bed as possible? That way, perhaps it might skate over the bumps instead of diving into the hollows?

Pete Rimmer24/05/2020 21:42:11
715 forum posts
49 photos
Posted by Hopper on 24/05/2020 09:46:57:
Posted by Pete Rimmer on 24/05/2020 09:42:44:

The saddle and tailstock run on different parts of the flat way, the tailstock will never wear the chuck end and the saddle won't appreciably wear the tailstock end, so you can actually put a level on either end quite confidently as it will sit on the un-worn parts both ends unless the wear is particularly heavy or the top surface damaged with dings and burrs.

This doesn't stop the saddle rotating on the worn bits but it does give you a baseline to start your measurements. from.

But the saddle runs on the full width of the top horizontal surface of both ways. So saddle wear is full width. Problem is the front way way takes most of the load and wears more than the rear way. Unless the Super 7 carriage is different from the ML7? (It doesn't appear to be but I dont have one to hand to check.)

I suppose you could measure the actual wear on the bed and shim the level accordingly??? Or build a "sled" that referenced off the relatively unworn underside of the shears where the lift plates run and sit your level on that??? Tricky though.

Edited By Hopper on 24/05/2020 09:57:47

Ah right, I didn't realise that. I have scraped a 7 bed from end to end (hand-scraped 7 thou of wear out of it) but never used one.

Your next best option would be to pop the headstock off and put the level on there.

Graham Meek25/05/2020 10:14:01
215 forum posts
151 photos
Posted by Mike Donnerstag on 24/05/2020 19:27:10:

 

Graham Meek:

(By the way, I have your handwheel dial fitted that I purchased from Steve Tracey-great design and a fantastic bit of kit)

Hi Mike,

Thank you for the kind comments about the Handwheel Dial. Steve makes a better job of them than I did, he has the kit to do it with.

Generally

As regards using an Engineers Level with a worn Flat Bedway. It is known that the wear on this particular Bedway is 0.0025". A feeler blade, which is a standard in my Moore & Wright set of gauges, can be interposed between the Bedway and the Level which will restore the Status Quo. No need for any further dismantling, or ruling out the use of a Level to check a worn bedway.

Regards

Gray,

 

Edited By Graham Meek on 25/05/2020 10:19:06

Mike Donnerstag29/05/2020 12:46:14
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Unfortunately I don't have any engineering friends from whom I could borrow a level. Do you have any recommendations for one that I could purchase? I noticed that RDG have unnamed (Chinese) levels from about £52, or Moore and Wright for £144. Nice tools, thought I'd probably only use them once!

Or...

Is there anyone anywhere near Lincoln who could perhaps lend me a level?

Mike

Graham Meek29/05/2020 15:23:55
215 forum posts
151 photos

Hi Mike,

While a level is the quickest and easiest way to check for twist, it is not the only way.

In my first post I outlined the use of a length of Silver Steel or Precision Ground Mild Steel. I used this method to set up my Maximat lathe the last time I moved the shop around.

I bought an 8" Engineers level second hand form an advertiser on here. It is a Rabone and Chesterman circa 1970's. I don't know what accuracy it is, but it is fussy. When I checked my lathe with this level I found it was not that far out, given I had used the Ground bar test.

Unfortunately I am the other side of the country in the Forest of Dean, or you could gladly borrow my level.

Regards

Gray,

Mike Donnerstag29/05/2020 15:51:56
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171 forum posts
35 photos

Hi Gray,

I printed a Myford alignment test sheet, and my tests have shown the spindle to be quite outside of tolerances, as follows:

my myford alignment tests.jpg

As such, I don't think I can trust the accuracy of my spindle taper.

Do you have think the bearings may be worn, or need adjusting?

Mike

blowlamp29/05/2020 17:12:37
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I don't think there's is much point in using a precision level to check your lathe if it's generating a barrel shaped part.

A level would be a good tool to use to correct a taper though.

Martin.

Graham Meek29/05/2020 17:30:31
215 forum posts
151 photos

Hi Mike,

I am a little confused by the XXX "mm" readings which in some instances are larger by a factor of 10, from what I would want to see, taking the 0.068 mm on the Headstock Alignment-Vertical as an example.

Did you check the Test Mandrel for concentricity before you used it? It might be new but it would not be the first time I have experienced one that was wrong.

Placed on dead centres in the lathe and spun by hand under a clock will prove this to be a good one, or otherwise. Clock at the small end of the taper, the large end, the plain diameter next to the lager end of the taper and at the tailstock end.

There should be Zero error at any location, Plus the test diameter should be exactly parallel. If it is then I think you need to inspect the mandrel taper socket for cleanness and for any damage. As the spindle is hard there should be no damage, but you never know.

I know of one individual who decided to try and drill out his spindle to take a larger bar. I had to internally grind the damage out so that the Morse taper would seat properly.

During these tests above, have you tried clocking the mandrel with the belts under tension. Or have your checks been done in the free state? Too much tension will accelerate wear and if the spindle front bearing is out of adjustment then the belt tension will influence any readings.

A clock on the mandrel chuck register will show if the belts are lifting the spindle as the belt tension is applied.

Adjusting the bearings is not a hard thing to do, but I would like to see what the answers are to the Test Mandrel concentricity test as well as the mandrel taper socket, belt tension etc, before I say any more.

Regards

Gray,

Martin Kyte29/05/2020 17:48:02
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1842 forum posts
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Posted by blowlamp on 29/05/2020 17:12:37:

I don't think there's is much point in using a precision level to check your lathe if it's generating a barrel shaped part.

A level would be a good tool to use to correct a taper though.

Martin.

Well if it's a combination of spindle bearings and bedway twist the level will eliminate one of these.

I don't think you have done a cut between centres on a test piece. Irrespective of bed twist or tailstock misalignment you should end up with either a tapered test peice or (unlikely) a parallel piece. Either way the testpiece should be 'straight sided) unless you have significant bed wear.

I should like to see you set the bearings up properly first.

Do it like this

1. Power Down

2. Remove all belt tension.

3. Remove Chuck

4. Rotate RH collar one complete turn. (top towards you).

5. Rotate LH collar one complete turn. (top towards you).

Spindle should be completely free of front bush.

6.Loosen allen screw on collar at end of spindle.

7. Using the Allen key tighten collar as tight at it will go by hand.

Inner tapered roller races are now locked together with correct pre-load.

8. Back off LH collar one complete turn + a bit (top away from you)

9. Rocking the spindle by holding the spindle nose tighten the RH collar by hand (top away from you).

10. When you feel resistance to movement stop.

11. Collar should be just tight enough that spindle can just be moved by hand holding the nose.

12. Do up the LH collar by hand (top towards you).

You should still feel resistance when turning the spindle by the nose.

13. With the crescent wrench on the LH collar tap the end smartly with a 12oz hammer.

The spindle should move forwards by a couple of tenths and be completely free running.

14. With the lathe running slowly (lowest direct speed) put the oil gun in the front oil cup and pump until oil issues from the front bearing.

This is how Myfords used to set the lathe up.

regards Martin

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