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Member postings for Martin of Wick

Here is a list of all the postings Martin of Wick has made in our forums. Click on a thread name to jump to the thread.

Thread: ML10 - ready for the boneyard?
06/08/2018 11:47:32

Ignatz

I don't know if the deviations I've measured are necessarily so bad for this old machine. In any case, I wanted some feedback on the results before I start tinkering with the headstock mount and playing around with shimming.

After that I can try some test cuts for parallel on some free maching steel I've secured.

from your figures I think you have conclusively proved there is nothing much wrong with your lathe! You would be hard put to find anything affordable in the hobby market giving much better results than < half a thou out at 6 inches, whether you think it is wear or alignment causing the issues.

Try to bear in mind also that the spindle also needs some freedom to move, so I don't think there is excessive bearing play either- less than a thou 10 inches out? come on!!! how much better do you expect it to be?

Time to stop chasing your tail and start having fun making something useful.

Thread: Myford Super 7 metric change gears
01/08/2018 21:23:59

what arrangement would I use those wheels? I'm assuming they would not be used together but 21 for some metric threads and 63 for others

or Create your own tables to suit your gearset using this inline tool

**LINK**

other utilities are available

Thread: ML10 - ready for the boneyard?
01/08/2018 19:53:18

Spotted Neil,

I thought it looked a bit tight, obviously at eyes glazed over at runout and just assumed play was what was meant.

Having said that, I can hardly detect any play in in the spindle on my 10, sub 1 thou, but it doesn't seem to get warm when run, so that was my justification for 1/2 a thou on play.

I guess if you were really working the lathe in an industrial environment you might want a bigger clearance.

BTW, what in your view would wear more in steel to iron bearings, the spindle or the iron bearing itself? someone told me once that you get a sort of carbidey type glaze on the surface of the iron, and counter-intuitively it is the hardened steel spindle that wears more... is that possible?

Thread: Myford Super 7 metric change gears
01/08/2018 18:10:12

So far I understand that a 120/127 tooth compound Wheel would be the most accurate. Is that correct? Would that apply for a ML7 with no gearbox as well?

Two 21s and a 63 with the usual changewheel set should cover most of the metrics

Thread: ML10 - ready for the boneyard?
01/08/2018 18:01:02

Currently, I can force some movement of the main spindle at the chuck end by virtue of inserting my fist underneath and exerting pressure. I am reading a total deviation of about 0.035mm ( = 0.00138 inch ).

Ignatz,

The play in the bearing is unfortunate, but recoverable. Is there significant side to side play, which is more of an issue?

Difficult to predict what will be worn and where, so I don't think you will 'push' the spindle down at the nose as you imply, even if you do, that will be less significant than any side to side play

The effect of squeezing the bush down will be to close that area of wear slightly, hopefully reducing play. In any case up and down play in the spindle of +- half a thou would probably not account for the amount of taper you have measured (side to side play might).

Spindle play generally manifests as poor finish rather than a tapered cut, but the forces at the tailstock end of the piece when cutting, could in theory deflect the spindle in the bearing sufficient to result in a shallower cut at the tailstock end ( and so can deflection of the work piece)

Proceed as you wish, but if it were my machine, I would do the simple checks first, headstock alignment and twist. It is easier and safer to deal with these before hacking the bearing!

If you still have a significant taper on a test piece after confirming the alignment is OK and there is no twist (and you have mounted the work deep in the chuck to avoid the effects of the jaw belling) then it is time to look at the bearing.

Check front and back bearings/spindle contact for play both lateral and vertical, The front one will have suffered the most impact, but they need to be considered together. The amount of wear is not that great an you have the right approach - proceed delicately! Lap off half a thou at a time from the shim and recheck the spindle movement. Personally, anything less than 1/2 a thou play static would do me. If you go tighter, make sure to run the lathe up at high speed for half an hour (with oil) and check to see the bearings are not warming up unduly.

If you are going to the trouble of adjusting the bearing shims, you may want to consider taking the spindle out to remove any gunk/swarf etc from the bearings giving the lot a good clean. It is unlikely you will damage the headstock with the level of adjustment proposed, just make sure you remember to reinsert the shim before cranking down on the bearing bolt and check spindle rotation by hand as you tighten up STOP as soon as the spindle starts to feel the least bit tighter

You will never reduce the errors to zero so don't sweat the small stuff!

01/08/2018 15:30:32
Posted by Ignatz on 01/08/2018 14:05:00:

I'm going to check up on that bell-mouthing again once I have some ground silver steel bar in hand.

Am I correct in thinking that I should first address any play in the spindle journals (by lapping the shims) before doing anything to the chuck?

0.4 of a thou axial play is fine, leave the spindle bearings until after you have confirmed spindle/headstock alignment (as you confirm the finish is acceptable for now)

Bellmouthed chuck unless really severe, or you are mounting the work right at the front of the jaws, is more of an irritation than a real problem.

Suggest you grind jaws(with jaws griping something inside) only after you are happy with the rest of the system, or simply buy a new chuck keeping the old one for non critical work

01/08/2018 14:56:58
Posted by Hopper on 01/08/2018 11:19:40:

Martin, chuck runout has no bearing on the test piece once a cut has been taken over it. Even if the chuck is off centre and cock-eyed, the turned surface of the test piece will be in line with the lathe spindle. .

We have already established the lathe is turning tapers, the challenge now is to identify the reason by a staged process of investigation and rectify.

Agreed, if you only consider radial runout of the chuck. Radial runout doesn't matter that much. However, you also need to consider the axial runout, and 1+ thou runout behind the chuck is small and probably not the main cause of error in this case, but if it was 2 or 3 thou, you might expect 4 to 6 thou angular deviation 100mm out from the point of measurement if that error was consistent through the chuck body (because it might only be the back face of the chuck/backplate that is out).

Try this experiment, take a small piece of straight thick wire, put a slight bend in it, imagine one side is the work piece in the 'bent chuck' and the other side the spindle, twirl the 'spindle' side between thumb and forefinger as if in the headstock, observe the circle described by the workpiece end and then imagine a tool cutting on an axis parallel to the spindle - result is a taper cut (as you may get with workpiece set poorly in a bellmouthed chuck).

However, in the two cases of distorted or a bellmouthed chuck, the effect will be the same, i.e., the end of the work piece is most likely to precess as per the bent wire experiment, which would lead to work piece being cut narrower at the tailstock end than at the headstock. From the measurements provided, I think I am right in saying the test piece is actually narrower at headstock end following the cut, by some 3.5thou over 3.5 cm, (sorry to mix systems!) turning a longer piece say 10 cm would mean a taper of approx. 10 thou over the diameter, which may be significant (or not at all, depending upon the intended use of the piece)

Assuming the work piece is well mounted, there are no bellmouthing issues and Ignatz wishes to remove the sources of error, there aren't too many options left to consider now, most likely being headstock alignment or possibly a twist to the bed or concatenation of both. Easily addressed once you diagnose the problem

The original question was 'is my 10 a boneyard candidate', the answer is clearly no, it is not. It is just a 50 year old lathe that has recorded all of the bad habits if its previous owners. The simplicity of the 10 is it will only need some minor adjustment once the issues have been fully identified. It will then be capable of sustained and accurate work

01/08/2018 09:56:40

Ignatz

The 3-jaw chuck I used is an older Pratt Burnerd that came with the lathe when I bought it. The screw mount is integral with the chuck body and so I tend to discount faceplate distortion.

Ha ha!, never trust a chuck! or rather 'trust, but check' as they used to say in the NKVD!

I have exactly the same myford integral chuck, was having similar problems and the spindle checked as parallel on my 10 and so assumed there was some issue with the chuck jaws. I consulted the forum with view to grinding and somebody suggested I check the runout on the chuck back (nah, surely not , I thought) and guess what.... when measured- nearly 2 thou runout, which over the chuck + test piece length was 6 to 8 thou taper! (and would be correspondingly more for a longer piece).

I think this type of chuck condition is unusual but not without precedent - anyway will only take 5m to check (somebody suggested internal stress relief over time as a cause of distortion, but I think more likely to have been die to a nasty lock up ). BTW, I did a quick and dirty fix of shimming up the low side between the integral plate and chuck bodywith some ally foil to avoid having to skim the integral plate and chuck innards - reducing the angular error to practically zero over 6 inches Picture of dismantled chuck in my album). There was still 1.5 thou runout in the chuck, but this is coaxial with the lathe and not worth chasing down on a 3 jaw

once the initial cuts are made, the surface of the workpiece should be - in theory - spinning true, in line with the axis of the spindle.

Yes, but if your spindle or chuck or both are not coaxial with the lathe bed and traverse of the carriage, you will turn a taper as it appears is happening. Assuming you mounted the work piece perfectly axial to the spindle and your first measurement (the largest) is at the tailstock, your measurements suggest that the misalignment is towards the back right of the lathe (or the right end of the lathe may be twisted towards the back with respect to the headstock end). In respect of bed twist, the error seems too large to be fully accounted for by twist alone, but may contribute as errors can be cumulative.

“Rollie's Dad's Method of Lathe Alignment” is quite interesting.

Yes, but bear in mind its limitations, in that with a chucked system, the method does not discriminate the error between chuck and spindle, which is why it is important to confirm there is no chuck runout (and that the jaws faces are co axial) - you do get people that grind the jaws in response to these type of issues without fully understanding the true source of error thereby not only not fixing the issue, but trashing a chuck as well (however, there may be perfectly respectable reasons to grind the jaws, but depends how well it is done)

I would strongly advise you to get a 2mt test bar, it is a very useful bit of kit for checking spindles, setting tailstocks and topslides etc a 6in one will do but if you are masochist, get a longer one! If you put a quality test bar in a well cleaned and deburred spindle and it indicates true or not, then the result is usually definitive (and a piece of 20mm silver steel for other checks).

Don't discount the possibility of bed twist, but that check should come after you have investigated all the other sources of error.

Above all have fun!

01/08/2018 00:17:36
Posted by Mick B1 on 31/07/2018 18:28:34:
Posted by Martin of Wick on 31/07/2018 17:13:17:
Posted by Mick B1 on 31/07/2018 14:09:26:
Posted by Martin of Wick on 31/07/2018 13:04:05:

....

I have a fitting for turning diameters up to about 11in, cant remember when I last used it though!

How does that work? Riser blocks for the headstock? Workholding on the ar$e-end of the spindle? I never found any such device when I was building my Stuart Beam.

**LINK**

Mick see link above and find machine builder post with video and scroll to near end of video to see what these devices look like. Don't think they are available as commercial products

...

Highly under-rated machines, stigmatised by their lack of ubiquity.

Thank you for that. I don't think I've ever seen one of those attachments for sale separate from the lathe, which means they're effectively unobtainable except by making one, and IMO you really gotta love your Myford 10 to be prepared to do that. ?

agreed, I don't think I would have had the courage to make one, but they do appear from time to time on a popular auction site and are not always recognised for what they are (ie don't get bid up to stupid money like most myford stuff). The one for the 10 cost me about £30 plus about 10 for postage which is les than half what it would have cost to make. It is based on a solid aluminium billet, so not as cool looking as the one demonstrated by Myford Boy - King of Kasting, although I was somewhat alarmed to see that he double clamps it to underneath the lathe bed - do I need to fear that the awesome, stump pulling power of my 50 year old1/4 HP motor will tear the fitting right off the bed Vways?

any advice welcomed.

31/07/2018 23:59:05

Uh huh....

A not untypical problem and hinted at my earlier post. Easily checked and usually easily fixed. I will take it from the top. the error is relatively large over the small distance - circa 3.5 thou and could be due to a number of simple adjustment issues....

First off and easiest, did you turn using the top slide or leadscrew? if using the topslide, did you check motion was 100% parallel to bed? if not set the topslide angle to be parallel to bed with using your DTI and see if that has any effect.

If you used the leadscrew to drive the carriage, then next thing to check is spindle alignment with lathebed/carriage. Various ways in which you can do this, easiest is with an MT2 test bar of reasonable length-say 6 inches, but you can also use a piece of silver steel in the chuck and the RDM (consult web for various approaches and rollies dads method is popular- google only problem with RDM method is that it may be telling you more about your chuck than the spindle, check out a steve Jordan video on alignment on youtube

If the spindle is miss-aligned, the headstock is only held by two clamps, it is possible that the headstock has had a knock or been interfered with in the past, this is trivial to readjust using the test bar (might need a shim or just re-setting to front Vway.

If checking with test bar indicates the spindle is true to the bed in all dimensions, then there are 2 other possible sources of non conformity

The easy- the chuck and or chuck back plate is distorted - no really, I didn't believe this could happen, but another member gave me the heads up on this when I was having problems with run out and it was exactly the cause of the problem. - check for no run out in the Y plane with DTI on the back of chuck mounting plate ( I will assume that the chuck jaws have not been modified by grinding etc)

If no errors found from all of above, check jaw alignment with piece of silver steel, if bad consider new chuck, if bold consider grinding chuck, if rich, consider replacing jaws (assuming they are available).

The difficult - the bed may be twisted - not that likely as the 10 has a very rigid bed compared to the 7 but it is possible that there has been distortion over time. arrangements. Check by turning a 6" x 1" work piece to a dumbbell shape and than take a LIGHT test cut at each end on the same setting and mic any twist will show up as a dimensional difference between the two ends ( refer you to Steve Jordan video for simple explanation) Quite what you will do about any twist depends on your method of lathe mounting - clearly you should not perform this test until all of the previous sources of potential error have been eliminated.

Could be that the gross error is due to accumulation of all of the above, so best blow the dust of the DTI and settle down to have a bit of sport.

All of these are simple set up checks and issues - even on new machines, welcome to the world of hobby engineering!

If non of these checks reveal any source of error, then your lathe has clearly been possessed by demons and should be handed immediately to an experienced lathe exorcist such as myself for safe keepingdevil

31/07/2018 17:13:17
Posted by Mick B1 on 31/07/2018 14:09:26:
Posted by Martin of Wick on 31/07/2018 13:04:05:

....

I have a fitting for turning diameters up to about 11in, cant remember when I last used it though!

How does that work? Riser blocks for the headstock? Workholding on the ar$e-end of the spindle? I never found any such device when I was building my Stuart Beam.

**LINK**

Mick see link above and find machine builder post with video and scroll to near end of video to see what these devices look like. Don't think they are available as commercial products, but basically they consist of a billet of material which can be clamped to the bed in which a short spindle runs on bearings, a Myford nose one end, myford change wheel(s) other end - spindle at a suitable distance above headstock spindle, driven by a morse taper with another suitable change wheel. As these are DIY items, a great deal of variation may exist eg. fabricated frames, timing pulleys and belts instead of change wheels etc etc. The max size is dictated by available tool positioning on cross slide

The one I have for the 10 is change wheel driven, and has a layshaft with idler to ensure normal rotation, it is also geared down to approx. 1/2 headstock speed (remember the days before VFD and reversing switches )

The one I have for the 7 is an absolute monster, using the kind of timing gears a tank would have and will spin you 13inches in diameter, should you feel so inclined.

Both home made, the one for the 10 worked very well - I thought with the slop from the gears it would be very chattery, but not so

I have never tried the one for the 7 in anger other than to confirm it runs ok (and as you would expect much quieter than the geared version). The body is an humungous solid iron casting taking a real effort of will to lift!

They were both acquired, the one for the 10 looking as if it may have been built a plan, the one for the 7 looks as if it was constructed in a locomotive workshop of brobdinagian proportions.

Personally, I see no good reason why you couldn't get a couple of reasonable regrinds from a 10 bed and of course you would also need to grind the apron top or the carriage bottom in proportion to respect the leadscrew nut position. But you couldn't do too many without thinning the V ways and then having grind the bottoms off tailstock and carriage Vs etc etc.

Grinding the top of the apron must be way easier than drilling and eccentrically bushing the bed casting leadscrew bearings on a 10 ... Full hero points for anyone attempting that!.

The 10 is a lathe clearly designed by a committee of engineers and probably treated by its creator as the illegitimate brother of the 7, I suspect they felt the need to market something cheaper than a 7, but not something that would dent sales of the 7, hence its general quirkiness (as in why did/didn't the do that..? what can we do to make it not appeal to a mass market?). Highly under-rated machines, stigmatised by their lack of ubiquity.

31/07/2018 13:04:05

'.......Myford don't muck about - they replace the spindle. It doesn't mean that shimming is 'wrong', just that there's a better way which will cost a bob or two more

Yes - good for Myford (as was)! And unnecessary as the adjustment is simple but requires caution so spanner benders need to take care. You will struggle to find a new spindle now.

the cast end bracket would not allow the lead screw to be repositioned following the regrind

Suggest you take a look at Lathes co for a picture of ML10 and decide for yourself if you agree with that statement.

Not sure ML10 had a hardened bed, don't think mine is as it marks quite easily.

Good robust lathes, smaller and neater than a 7, you can run' the iron bearing ones at high speed too, if you have a VFD and good lubrication (or suitable pulley arrangement ). If I had a choice, would prefer the taper bearing version(less oily mess in the headstock), but quite happy with my 'Iron Dog'. The main irritation is 31/4 centre height that means all of the available ML7 stuff needs to be modified and requires small tools with turrets toolholders Simple problem, but irritating. I have a fitting for turning diameters up to about 11in, cant remember when I last used it though!

31/07/2018 11:38:28

BTW,

I assumed that the headstock is also co planar XYZ with the bed? if you have not checked, get an MT2 test bar and carry those checks and adjust if necessary (google rollies dads method etc). sometimes previous owners get to fiddling about with headstock bolts as well as tailstocks.

As you were turning between centres, headstock would not show up significantly on your workpiece, but would with normal chucking - when you have resolved cutting issues, try turning a chucked test piece as suggested above and measure for parallelism.

31/07/2018 11:13:12

from your description, just like my M10 -

you will / should see on the headstock an allen bolt at the front of the bearing clamp locations front and rear of spindle and in the clamp a slot filled with laminated shims or a solid shim. WHEN you have carried out the check I suggested by checking both front and rear spindle play and ONLY IF you confirm play in the bearings approaching 0.002 thou first try gently tightening the allen bolt 1/16 at a time.

If you cannot, (please do not start levering hard on this bolt) loosen off and remove the laminated shim pack and remove one of the 2 thou shim foils, replace shim pack and gently repeat the tightening process 1/16 turn at a time.

In case there is no shim pack, but just a solid shim, you will have to gently lap the shim by the amount of play you measure.

Please please please do not attempt to over tighten the adjustment allen key or attempt too large a thinning of the shim otherwise you will REPEAT WILL! snap the headstock bearing clamp and scrap your lathe headstock. You should aim to remove play but still have free turning by hand of the spindle. Following adjustment, monitor temperature of bearing clamp.

The wear you report on the bead is trivial. Again you don't quantify how tight the saddle gets - they all do tighten on beds that have been used. If you can still push the bed by hand up to the tailstock end all is OK (assuming gibs are properly adjusted - neither too loose AND ALSO not to tight)

Re bowing of the lead screw - forgot to say you may need to check adjust the nut position on the apron, but as you say it is small, you can do this later.

If the tailstock was significantly out, you would see the effect in deep holes of the drill flexing, so then check for coplanar motion in tailstock barrel vertically and horizontally

Please refer to copious material on web reference tailstock adjustments - it is not a trivial job, and to do well will take you a long wet sunday afternoon to get spot on, especially if you need to shim to be coplanar vertically,. In any case, this is the least significant dimension, so a tolerance of 2 thou between barrel in and out would be ok. Once you have got it right, you will never want have to adjust it again!

From the measurements you give, the work piece is being bowed which suggests the cutting action may not be quite right.

The finish issues described are more likely down to poor material, cutter, feeds and speeds, settings, nothing inherent the dimensional accuracy you report would lead to the finish issues - you don't ay what cutter, suggest you use accurately HSS to start with if not already using.

I see no significant problems with this lathe.

31/07/2018 09:54:17

Don't Panic!!!

you are dealing with very small issues, taking it from the bottom, a bow in the leadscrew that you can only just see will have no effect on accuracy assuming all gibs are properly adjusted.

If you lever on barstock in a chuck you will get some deflection - you report about 1 thou inch so check deflection of spindle with no chuck mounted by pushing up and down and side to side on the bull wheel. If you still detect play, this can be adjusted out easily.

The ML10 iron bearing is very robust, unless abused by not oiling, and can be adjusted by taking out a shim and tightening the bearing clamp screw (this needs some care to do to avoid snapping the shoulder so I suggest you get a manual).

Put a 2 ft straight edge along the bed and shine a light from behind, If the lathe bed is as worn as you believe you will see the extent. If you slide a 2 thou shim underneath, that may confirm your diagnosis. The other check is to adjust gib strips with the saddle close up to the chuck, then move the saddle by hand to the tailstock. If it tightens significantly, then there may be a problem with significant wear on the bed. Even if this was the case, you can still use this machine to carry out accurate work.

You don't say what the tailstock vertical and lateral deviations are, or whether your test piece is parallel or not. Tailstocks are notoriously fiddly to set accurately in all dimensions, so you may need to spend some time adjusting - Vertical adjustment to be co planar with the bed are often overlooked, not least by the manufacturers! This only becomes a problem when drilling deep holes- Are you snapping a lot of drills?

You report that the work piece looked 'as if the dog chewed it'. with properly adjusted gibs, fully locked tail stock and correctly ground tool at the proper height, there is no reason you should have a bad or inaccurate finish when turning between centres in the way you describe, even with the 'wear' as reported. I would check those issues again, especially as your reported inaccuracy is only 2 thou, on a ribbed finish.

Of course, if you don't want the lathe, I will take it off your hands for the cost of a pint or two!wink 2

Thread: Warco Mini lathe
17/07/2018 12:19:58

Remember the class of lathe you are dealing with! A slight bed tightness will not be a major issue (unless you physically cant turn the leadscrew by hand at that point) and is easily fixed as pointed out above. There are various blogs that set out how to do this, depending on how serious the issue.

The first thing you should in any case is remove the apron and put a backplate on it to prevent swarf getting in, because if you don't, the first time you use the lathe, swarf will jam the apron gears and you will probably need to remove the apron to clear it anyway. Setting the carriage gibs on this type of lathe is a major PITA (you do in fact have to unbolt the apron and shift it out of the way).

Also, to avoid future frustration, I suggest you also check the tailstock taper and horizontal/ vertical alignment thereof.

To make you feel better, I purchased one of these ubiquitous CMLs from another supplier and here is a list of the fixes required before deemed fit for use:

  • Burr on saddle causing rocking needed to be lapped and removed.
  • Leadscrew mounted at an angle causing tightness at end of travel, needed holes in one of the blocks elongated to be set to run true.
  • Tailstock taper not fully cut, therefore not holding taper tooling securely (how it passed inspection was probably by jamming the test taper in and wiggling it about until it gave the desired reading!). Used a MT2 reamer to sort, but resetting the alignment was quite tricky.
  • Cross slide nut way too tight, could not back off with grubscrew, eventually found the nut was too deep and had to file a few thou off the top.
  • The speed changing yoke unscrewed itself very quickly, or so I thought, but when I dismantled the headstock I found that they hadn't even bothered to put the grubscrew in - it had been working on friction!
  • Motor not mounted correctly to vertical or horizontal axis of the headstock shaft (would lead to premature belt failure).
  • Slight tightness in bed in the centre section as per, but will see how bad this is after a year, or when I get around to making some taper gibs for the saddle, whichever is the sooner!

But apart from all that, the lathe was OK!wink 2 So if your only issue is a slight tightness in the bed, you are doing well!

Thread: Paint for Colchester Lathe
30/05/2018 10:48:49

Phil,

Thanks for that, I too have the Lidl HVLP gun, so good to know it is OK to use. I was only painting an ML7 and chickened out when I saw the size of the nozzle on the Lidl gun (1.6mm I think). Bought an equally cheap smaller gun. I think that as you come down in nozzle size, you probably have to thin the paint more.

I did try using a less thinned mix as recommended and noticed that an intermittent leak on the air needle was probably the cause of the poor/irregular atomisation (=cheap gun!! so had to re thin the paint in the cup, gasp of horror). I can live with the inconvenience of not being able to get multiple coats on in a single spray session as long as the extra thinner will not affect the long term paint performance (no reason why it should?).

So far the spray results are surprisingly good even with the crappy little gun I am using (for the undercoat stage at least). The spray gun is only being used for the cover castings and awkward countershaft plates.

The smaller parts and bed I did by brush and those have also come up very well, but very, very time consuming and yes, tedious (paint, dry, rubdown, paint, dry rubdown, and so on ad infinitum it seemed). The trick I learned (for this paint at least) is to use a relatively stiff synthetic brush (Harris in this case) and work really fast. I can just about keep up on the smaller parts, but when I tried brushing the covers it was a disaster due to my lack of skill, hence use of spray gun.

I will try to source a better quality small gravity gun for the top coats, but it wont be De Vilbis (unless they sell one for a tenner!).

28/05/2018 21:38:01

I am in the process of re-spraying with Paragon paints. I was interested to read that Phil thins the paint at only 15%.

When I tried that recommended thinning rate, the paint remains like treacle and will hardly get through the gun (HVLP gun at 3 bar and 6cfm with a 0.8mm nozzle). I am having to thin more like 20 to 25% to get reasonable atomisation, which means the tack time is more like an hour. I am new to spraying, so possibly laying on the coat too heavily (but not seeing any drips). but If I try restrict the paint needle to try to get a thin coat, the gun cant cope.

I was wondering what nozzle size/ thinner ratios others are using for these synthetic enamels and whether there are any special tips for dealing with this thick paint? (other than brushing!)

are there any views on the acceptability of using a colour from a different machinery maker to the one owned?

Thread: Lathe chuck not true.
23/03/2018 11:45:59

Brian,

Thanks for that, It also occurred to me that although the chuck back looks relatively substantial, it might be possible to distort it if there was a nasty dig in or lock up (but not on my watch - to timid!)

Two halves of myford integral chuck shown in photos below, with the offending back part placed on lathe spindle in top photo - the threaded part is in the business end of the chuck in bottom photo.

There is about 20 thou clearance between the spigot on the back part of chuck and the rotating scroll, so should be ok to skim 3 thou of the bolting flange (might also have to check the spigot clearance from the front of the chuck also)!

If I can get to 3 thou run-out I will be delighted! (better than current 9 thou TIR).

Journeyman, thanks for brilliant suggestion to use some stout tube and threaded rod through the spindle - that would make for a very quick job.

Bets regards and many thanks for the excellent advice,

Martin.

001.jpg

002.jpg

22/03/2018 21:02:25

Brian,

You Da MAN! !!!

The back plate of the integral Myford chuck comprises the register only as the threaded portion is in the chuck body. However, that register portion was a good fit on the mandrel nose and not going to wobble from the pressure of a DTI.

Even so I checked several times in differing positions and the result was always the same - 3 to 4 thou run-out in the plane normal to the spindle axis. Moreover, the low and high positions corresponded to the low and high chuck jaw run-outs, so well spotted.

I can see how this part not being truly normal causes the problem, but cant understand how it ended up in that condition - or was it like that from day 1?

Next thing to do is make up a slim tube/top hat 11/4"W12 nut arrangement to secure the register plate tightly to the mandrel for skimming - that will be an interesting internal threading project! If my dodgy geometry is correct skimming the chuck back register should eliminate 80 to 90% of the chuck run-out at the jaw location.

It is great to know what the real cause of the problem was and you have saved me committing the unspeakable crime of jaw grinding!

So thanks very much Brian!

Regards

Martin

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