Are you suffering from Bar Sag?

[@ADBBuild]

This is the most polite and thorough calling out of haters the world has ever seen.

[@MachiningandMicrowaves]

That brought back memories of Bob Cawley at the Post Office Factories Division back in 1976 saying "Everything's bendy" when he was teaching us about surface grinding and lathe work and how to handle systematic errors from gravity, heat flows, expansion, tool pressure and all of the other spoilers of measurement precision. Always enjoyable seeing your attention to detail and thoughtful analysis

[@MrCrispinEnterprises]

Thanks

[@hashgeek929]

But what would Aimee say?

[@MachiningandMicrowaves]

@@hashgeek929 Something suitably scathing and critical, I have no doubt. She's a great fan of raffish young gents with world-class hat-throwing skills

[@billdoodson4232]

Robin Renzetti says the world is made out of rubber.

[@hashgeek929]

@@billdoodson4232 especially the rubber bits

[@Workshopfriend]

Thank you. Appreciated your responses to queries and the way you determined the relative impact of 'indicator droop' in your setup. You illustrated the fact that a little thought and experiment can make a big difference to the result. From a fellow ex-RR apprentice.

[@MrCrispinEnterprises]

Thanks

[@retromechanicalengineer]

I could teach you a thing or two about bar sagging. It usually happens to me after about eight pints. Any more than that and I get involved with bar slumping. Best wishes, Dean.

[@joejoejoejoejoejoe4391]

Around here you need 8 pints to find any of the women attractive. It's a catch 22 situation.

[@billwessels207]

@@joejoejoejoejoejoe4391 Just remove your glasses and dim the lights. Speeds up the process considerably and reduces out of pocket expenses considerably.

[@timelessengineering]

Mr. Crispin..... a world of practicality and contextualised topics. Always such highly accurate work being produced out of a home workshop. Well done. I look forward to your videos every week.

[@MrCrispinEnterprises]

Thanks

[@BM-jy6cb]

I'm glad the videos are flowing again.. Opening KZbin and being greeted with a new notification from Mr Crispin is always a treat.

[@bostedtap8399]

Excellent presentation on radial error caused by DTI measuring, something I've been regularly involved in when setting up, and training operators. The machines were rotary friction welders, on older machines, measuring "spindle droop", that is caused by excessive end float on taper roller bearings, was done simply by measuring how much the chuck would lift when using a blooming big crow bar. Remember that the operator would indicate the static clamped part allegedly on centre?, but when under axial load, the front bearing would centre, and the now weldment has a centre mismatch. Thanks for sharing Mr Crispin.

[@f.hababorbitz]

I just got a new tool in the mail yesterday, from Tangent engineering. It's a magnetically held sine bar that is sat on the cross slide top (assuming you have a square one like on your lathe) the indicator is magnetic/clamped to the ways of the lathe or the tailstock. Under one of the pins of the sine bar the jo block stack is placed, and the magnetic sine bar produces enough force to hold it in place. Then you just sweep the cross slide to dial in zero. I just found this channel, I like the style of your presentation. And I'm in the middle of trying to make internal spindles for my Czech made tool post grinder. Appears there are no standard tapers in these machines. My lathe also has a D1-8 spindle nose, and an odd spindle hole taper. It's a 90mm metric taper, and was imported by accident to the USA. The manual for the lathe say's it's a #6 Morse taper, but that would fall through the 80mm head stock hole.

[@number2664]

Great demonstration on indicator sag with the parallel. Simple and effective display ! That’s how I show people, they are usually stunned

[@alangordon1677]

Your Joe Pi method of setting the angle was the method taught to me in the 1960s by my instructor at college. At that time we were setting angles on a milling machine and using trig and table movement to set angles.

[@TheKnacklersWorkshop]

Hello Mr. Crispin, I had not considered Indicator droop before... Now that I am enlightened I will do my best to avoid it. Thank you. Take care. Paul,,

[@rallymax2]

I like that you knew where to stop on the nature of project stacking. I must practice that.

[@jim9689]

Your videos are outstanding. You are clearly an expert at your trade, and also one damn good instructor. As for measuring the cross-slide movement to verify the angle is set correctly, I think i would try to indicate off the actual lathe bed way somehow, which is the primary reference standard. You might need to create a special fixture to do this though.

[@edpopelas2844]

Bar sag is a good topic to refresh from time to time as it is bug that will bite you when you’ve long forgotten about it. Speaking of, keep an eye out for brother, last we saw him he had a evil gleam in his eye regarding a missing tooth brush.

[@ianmalkin5229]

Thank you for the video, you have reminded me of a discussion I had with a very experienced machinist. Ernie mentioned the change in readings with very large micrometres and other measuring equipment , The readings will change with how the micrometres are being lifted and held whilst measuring, this change just being due to flex/stretch in the backbone of the micrometres. it wasn't much change but it does matter when trying to be extremely accurate.

[@joecolanjr.8149]

Excellent demonstration and explanation my friend. This was very informative. Thank you for taking the time to explain. Cya on the next one. Cheers!!

[@MrCrispinEnterprises]

Thanks

[@CazClocker52]

I watched this video in its entirety last night! Fascinating video. I hope you continue to create more videos in the future.

[@MrCrispinEnterprises]

Thanks

[@bulletproofpepper2]

thanks for sharing! i enjoy your presentation. my job is very random in very remote locations. i sometimes need to adjust and aline output and input shafting. i knew about indicator droop but had no idea it was that much.

[@channelview8854]

Great information. I knew this was an issue but I must confess, I had no clue that the magnitude was so much. Thanks!

[@melvynoconnell1671]

Wonderful set of explainations, and it looks like you have sparked off another set of questions looking at the comments. If you have just made people think about what they are measuring then this will be a useful video(s). Reminds me of a story I heard many years ago about a long bar (about 30 foot long) that needed to be a precision flat, and the shopfloor and the QA dept did not agree about it been flat. The shopfloor were using a precision manometer and the QA dept were using a laser system. For anyone who hasn't cottoned on what the problem is, then think of the Humber Bridge, the two towers are vertical, but the distance between them is 4 inches more at the top then the bottom. Look forward to your next video.

[@swanvalleymachineshop]

I try & dress the unused rear portion of the wheel as well for balance . You should be able to balance a coin on the TPG spindle housing when it's running . That will be a big ask for a TPG to plunge grind that angle rather than use the compound , if that is your plan . Hopefully you will not get a slightly convex profile due to the TPG spindle bearing set up . My one , i would have to tackle that job as 2 separate grinding operations due to wheel dressing requirements . Best of luck !

[@MrCrispinEnterprises]

Thanks

[@grahameblankley3813]

Retired engineer with life time experience Machinist, found this very interesting, Coventry 🇬🇧👍.

[@MrCrispinEnterprises]

Thanks

[@billshiff2060]

This is a great dialog, this is what makes your channel the best! 3:00 Lets say the spindle was not square, you could still grind the face flat just by feeding across rather than full face using the grinding wheel as a form tool. Also, if using the full face form tool approach, any error in alignment(and there will be some error) is ground into the surface whereas feeding across eliminates that. Looking at the face to be ground vs the size of the wheel, it looks like there would be a large engagement percentage of the wheel face, that would concern me because that much engagement might produce chatter(especially seeing the rather spindly mount of the do-more).

[@MrCrispinEnterprises]

More good points you raise Bill. The concern I have with feeding the wheel across is that as the wheel breaks down during the cut (microscopically) the actually cutting point is changing and therefore it may not produce a flat surface. You could well be right on the chatter issue. We will soon find out.

[@billshiff2060]

@@MrCrispinEnterprises Yes the erosion of the wheel is always a problem in grinding but then you can always go back and forth however many times required. It won't have the nice "blanchard" type cross hatch but it will be flat.

[@Rustinox]

That was interesting. I never heard of indicater drop before, but of course, it makes perfect sense.

[@100yojimbo]

Excellent follow up video fully explained and demonsterated nicely done 👍👍👍

[@michaelrandle4128]

You’re one smart cookie Mr Crispin, thanks for the explanation,

[@WillemvanLonden]

"My coat pocket has got stuck on the lathe." Like watching Monty Python. You are improving with every new video, Mr. Crispin.

[@MrCrispinEnterprises]

Thanks

[@johnkneeshaw9732]

Should be a standard phrase in all foreign language phrase books

[@MrCrispinEnterprises]

LoL

[@joejoejoejoejoejoe4391]

One of the handles of a Colchester student is loose (for the cross slide handwheel), I was once using the lathe when I suddenly felt something rapidly go down my leg inside my boilersuit (this can take you by surprise...), the handle had come off, gone in a hole in the boilersuit; the hole is so you can get you hand in a pocket of the trousers underneath.

[@ronwilken5219]

@@joejoejoejoejoejoe4391 Yeh! That's your story. We'll believe you. LoL

[@somebodyelse6673]

It seems I learn something every time we go to the clipboard. Thanks, mate!

[@djhscorp]

Spot on video. Infirmative,educational and humour to boot😂

[@MrCrispinEnterprises]

Thanks

[@freddupont3597]

Such a fascinating and interesting video - Great explanations of problems I did not know existed, thank you @MrCrispin

[@crozwayne]

Yep, spot on Mr Crispin. the number of people I come across who have perceived errors on lathe alignments due to this phenomenon earns me some coin!

[@gvet47]

I cannot think of a good comment to get you started into your next video. Probably because you are smarter than me and you do prove that in every video.🤪

[@billshiff2060]

16:00 You just gave me a great idea. I will make a sin bar with a built in dead square on top to do exactly this kind of thing. That would be useful for many kinds of setups and measurements. It will give sin angle +/- 90° automatically. It will be a sin COS bar.

[@MrCrispinEnterprises]

Sounds ideal

[@Engineerd3d]

Interesting topics. Awesome explanation, also thanks for the book recommendation.

[@ronwilken5219]

I'm very much suffering from eyelid droop at 01:15 in the morning. To test your spindle setup would a say quarter inch thick, machined aluminium disk with a suitable boss, fitted to the spindle and offered up to the machined "cylinder" you have in the lathe chuck, give you a reasonable indication of alignment (disk is same diameter as outer of the cylinder) and parallelism (the machined face of the disk should show no gap between the faces). Any gap could be measured with a feeler gauge. The disk would weigh less than the vice, bar and indicator and is directly referenced to the spindle. Or am I being simple minded? I set my toolpost parallel to the work using either the face of the chuck, drive plate or faceplate or the mandrel of the tailstock. Seems to work for most applications. Just my offering. 🤔🇬🇧💩😃🤞🇺🇦🕊️🇨🇦🍌🥋👍

[@bkoholliston]

Good video! I appreciate your taking a serious look at indicator droop/bar sag--it is a real effect in my experience. My measurements and experience are that the measurement error depends not just on the mount, but greatly on the indicator itself and my Interapid (low measuring force) is the worst (several thou) and my cheap 1/2 thou indicator from China is the "best" at 1-1.5 thou. You could clamp a good (and square) height gage to the top slide and move the indicator up and down (always right side up) on the it. You could prove that the height gage was square on the surface plate if needed. That's almost certainly overkill. I am sure your mount for the grinder had some error, I just questioned how much you measured. I thought your angular Joe Pie method was fine but when I want it really close I put the sine bar and gages blocks on the side of the compound with a magnet (Mighty Mag) and indicate the sine bar on the compound relative to the lathe ways. That is the most accurate way I know to set the angle.

[@MrCrispinEnterprises]

Thanks, interesting points

[@billshiff2060]

I agree. I see in my most sensitive DTIs that the indicator alone has an internal sag error. I found that out by trying to use an "indi-cal" with a Tesa on it to measure a bore on the lathe. It works if the bore is horizontal but not sideways in the lathe.

[@proskub5039]

If your indicator droops, be sure to check if it has been inadvertently fitted with a droop snoot

[@624Dudley]

Good analysis and illustrations. Thanks Crispin! 👍

[@stevebosun7410]

Hi Mr C. How blindingly obvious. Thanks for the reminder.

[@MoondyneJoe]

Mr Crispin, I just came across your video "planting a Forest 26 June 2021". Could we please have an update on there growing progress, it would be interesting to see how they are fairing Tony from Western Australia 🇦🇺

[@MrCrispinEnterprises]

Yes I will do at some point. Being hard wood trees the land scape does not look hugely different at the moment but the good news is we have only lost about 20 trees out of 2,000.

[@MoondyneJoe]

@@MrCrispinEnterprises that isn't bad going at all, did your dad plant them as a wood lot, or timber or reforestation/animal corridor for his land or privacy? Tony from Western Australia 🇦🇺

[@ydonl]

My analysis of your analyses: (1) Interesting! Nice. Thanks for the effort and time you put into these videos; they make my day brighter. I enjoyed this one very much. (2) I think your bar sag analysis is quite good, yielding the right answer. (3) I *hope* you had fun thinking through some of these; I suspect you did, because of how your brain seems to be wired! :-) I'm learning to make precision measurements of (electrical) resistance. One of the standard techniques is to reverse the input to the test setup, i.e. rotate the bar through 180 degrees, and then subtract the readings, or take the average, or make whatever simple computation is required to eliminate the error. This works when the error is the same magnitude but opposite directions, or at least very close to that. I don't know if machinists ever do that sort of thing. The techniques that were thought up by clever people , a hundred years ago, in all kinds of technology (machining, electricity, others) never cease to amaze me. Brain-power, with no fancy electronics or computers or interweb, and yet in many cases the results are as accurate as we would normally expect today with all of our goodies. Carry on, sir! :-)

[@MrCrispinEnterprises]

Yes I think re arranging the checking method to confirm results is always a good thing if the situation requires and allows it. Cheers.

[@randyshoquist7726]

Perhaps one could compensate for an indicator's weight with a very light tension spring or elastic band. One could measure the spring's extension with the indicator suspended freely, then duplicate that extension when the indicator is mounted. Or one could load everything into a large airplane, direct the pilot to fly a series of parabolas, and work during those 20 or 30 second intervals of weightlessness. However, I suspect that would create other problems as well.

[@MrCrispinEnterprises]

Or as someone suggested, rotate the lathe and put it on its back while doing these measurements!

[@peterconnan5631]

Excellent and thought-provoking, thanks. Regarding point no.3, there may be a fairly easy way to remove concern about inaccuracies caused by a possible error in the straightness of the tail stock. Once you have advanced the compound slide the required distance, simply move the saddle the same distance in the opposite direction. This means that the indicator is then measuring in the same place longitudinally. There may of course still be some error vertically though. But as you mentiined, I am sure what you did was accurate enough for the job in hand.

[@MrCrispinEnterprises]

Good idea

[@billshiff2060]

I see a problem with that. This method relies on a precise travel distance on the compound at the angle. To hit the same spot you'd have to move the carriage precisely the cos x distance of the compound travel(if I got that right) to hit the same spot.

[@peterconnan5631]

@@billshiff2060 he has a DRO set up on the machine. Thus it will be very easy to do that precisely.

[@billshiff2060]

@@peterconnan5631 He has one but many don't and the carriage is the least accurate dial. But as mentioned, because the taper is so short you could get away with almost anything, even just the compound protractor because the compound ways will have some play that could swamp all the accuracy you might try to put in.

[@TinkeringJohn]

Hi Mr Crispin. You had me thinking about the grinding stone not being square to the spindle of the lathe when facing the work. When you use a mill, the cutting tool is stationary and the work is fed into it either in the x or y axis. When grinding on the lathe, you can have both the part moving into the grinding stone as it rotates in the spindle, and the grinding stone moving across the face of the work by moving the cross slide in and out. You should end up with different results. I would like to know what your thoughts are on this.

[@MrCrispinEnterprises]

Ok I'll see what I can mention in the next video

[@TinkeringJohn]

@@MrCrispinEnterprises Thanks. Another thought I have is that if the grinding stone is skewed to the work, the edge of the stone would wear down faster and become flush with the work. Wouldn’t dressing the face of the stone with the relief for clearance also create the same situation? Of course you are not trying to remove a lot of material if you are grinding the part down the last few thou’s to dimension. I worked at Buick in the 3800 engine plant as a machine repairman and I have changed grinding stones on Cincinnati grinders for grinding crankshafts and camshafts.

[@markuk7935]

I have to say, I've picked up a few sags in bars in my time. 😂🤣 👏👏

[@ronwilken5219]

Sags or gags?

[@peterblake548]

To get the two axes of the grinding spindle true to the axis of the lathe spindle may I make this suggestion? Fashion a simple bar of appropriate length with a proper hole in it and offer that up to the grinding spindle. Attach an indicator to the lathe chuck and ,by rotating the lathe spindle, tram the bar in the grinding wheel spindle that is coincident with the four coordinate positions of the grinding spindle.

[@MrCrispinEnterprises]

Yes sounds good although the length of the spindle is obviously quite short

[@peterblake548]

@@MrCrispinEnterprises Perhaps I didn't make my concept very clear. The bar containing the hole would be mounted in the grinding spindle in the place of the grinding wheel. Then rotating the grinding spindle with said bar and indicating the bar from the axis of the lathe spindle should provide very ample resolution for axis alignment. The spindle bearings in the grinding spindle are perhaps six inches apart while those in the lathe spindle might be measured in feet. Much simpler that setting up an autocollimator with unnecessarily high resolution.

[@MrCrispinEnterprises]

Ok understood

[@peterblake548]

@@MrCrispinEnterprises I must say that your axial alignment method from another video (that I was too stupid to watch before commenting) appears to me to be quite adequate...my bad.

[@larryriehle166]

Excellent presentation. I enjoy all of your videos. When are you going to get back to the locomotive build.?

[@MrCrispinEnterprises]

This spindle and chuck work is the last job on my list before I start on the Loco again. Hoping it will be at least a 12 month stint of working on it before I get distracted with machine tool overhauls again!

[@y2ksw1]

In this moment I had a discussion with a friend about the problem having 2 clocks, one which runs late and the other which runs early. Your problem about the sag sounds familiar, from this point of view 😅

[@matthewsmetalworkshop]

I didn't ask this on the previous video because I thought other questions had covered it, but maybe not as I don't see an answer here or in the comments to the previous video. Why are you using effectively a form tool rather than a single point tool? I have no idea at all about precision grinding, but if I was turning this feature I'd use a single point tool. I'd assume the same for setting up a grinder. I'd set the grinding spindle such that only the front corner touched, then dress the wheel such that none of the front face touched. That would result in effectively a single point tool and eliminate the precision requirement in almost all of the setup you did. I have never done any kind of precision grinding at all, so I'm just applying my turning experience, so I'm probably wrong, but why?

[@MrCrispinEnterprises]

Quite a complicated answer required! I'll cover it in the video of grinding the spindle nose. Cheers.

[@bcbloc02]

I mostly agree. With my experience with toolpost grinders they are best suited to be used with a point of contact not a face. If used like that any tramming errors would be minimal given the small diameter of the wheel and the smaller the diameter the less the error could be. My toolpost grinder has barely enough power for small point grinding even with dremel sized stones. If I wanted an angled face I would just use the compound to produce it.

[@MrCrispinEnterprises]

My concern with doing the work with a single point design of wheel is wheel wear. As you feed across the face any wheel wear will mean that the face isn't flat.

[@MrLukealbanese]

​@@MrCrispinEnterprises I've always wondered how wheel wear is accounted for in surface grinding actually. I'd love to see a video about this sometime

[@MrCrispinEnterprises]

I'll try and include something about this in the next video

[@StuartsShed]

Excellent follow up video - well presented, sound reasoning. 👍

[@thisnicklldo]

So the point is: Mr Crispin can explain bar droop at the drop of a hat (but not before) - it's the causal relationship between hat and explanatory power that fascinates me most. Or have I missed the point of the video? Maybe I have got the wrong end of the stick (though the stick looked pretty symmetrical to me, when used for throwing the hat). Thank the Lord I am not confused, though you may be.

[@Lanesplitter]

I've had this issue on my Dean Smith & Grace trying to produce a fir-tree root on an Inconel turbine blade! 😉Love your style fella!

[@MrCrispinEnterprises]

I've done allot of fir tree roots but never on a DSG!

[@Lanesplitter]

@@MrCrispinEnterprises My Magerle was broken at the time! Keep up the good work.

[@jimnolan830]

I've decided watching these videos after only one cup of coffee, when I've just woken up is a mistake.

[@MrCrispinEnterprises]

LoL

[@mrechbreger]

I'm pretty sick of my tailstock (I have a mini lathe), I ordered a hydraulic cylinder now and look into using that one and making another slide to put the actual tailstock on... Did you ever thought about something like that?

[@MrCrispinEnterprises]

No that hasn't crossed my mind

[@BensWorkshop]

Back in half an hour, missed that video...

[@MicrobyteAlan]

Very interesting, informative and well presented, thanks as always. 👍👍

[@MrCrispinEnterprises]

Thanks

[@mchiodox69]

Well done...great video. I learned a few things too.

[@davebambrook7745]

Hello Mr Crispin, another fine video

[@stewartross1233]

As well as interesting and entertainment every video is an education, thank you.

[@MrCrispinEnterprises]

Thanks

[@typhoon2827]

Subtitle: ain't gravity a bitch.

[@typhoon2827]

"oh. I'm exactly right" As a fellow Yorkshireman, I'd expect nothing less.

[@4pawsforge273]

Justifications = JUSTIFIED (from someone that knows absolutely nothing about your MAD SKILLS Mr. Crispin!

[@1crazypj]

If you watch the 'This Old Tony' video's from s a few years ago, originally he sounded a lot different to the 'Allan Alda' voice now used. Anyway, the point is, you look quite a bit like Chris Barrie in Red Dwarf (which I'm sure has been pointed out before) how about emulating his speech patterns for 'humorous interludes'?

[@CraigLYoung]

A very interesting video. Thanks for sharing 👍

[@BensWorkshop]

Yes, I did find it interesting, many thanks.

[@surindersingh4786]

Hats off to your intelligence sir👋👋👌✌

[@MrCrispinEnterprises]

Thanks

[@jerseyjoe2684]

Good day, Mr. Crispin 👍 🇺🇸

[@yambo59]

It just wouldnt be a complete Mr. Crispin video without his signature hat toss-lol

[@ElTelBaby]

I dunn'a suffer from Bar Sag;... eyes wide open... I can sup as many pints as the next;... but I do suffer from Testicle Sag... ROFL & no amount of dressing them up seems to work...

[@petemclinc]

In stead of making a project of grinding a 7 degree slope in the top plate, why not just shim it?

[@MrCrispinEnterprises]

Quite possibly could but it would be less stable. Also I think the disk may flex if it's being shimmed up and one end but clamped in the middle.

[@Sydney268]

Well, you're a clever (insert swear word here). and well done, that's why we watch you, keep up the great work Mr Crispin :)

[@MrCrispinEnterprises]

Thanks

[@copasetic216]

Nice to see you!

[@carlwilson1772]

Superb sir. Thank you.

[@jediatricwalker938]

Rigidity would be the blue pill factor in that no-grow indicator.

[@NRDavis-wl8vn]

Use to be bothered with Bar Sag but I got a Lovely Lady to walk with me from Pub to Pub, she keeps me standing tall. 😉

[@bamboozler8459]

I just wish my drawing skills were a quarter of the illustrations😂

[@Andrew_Fernie]

Good video that. 👍

[@deserado11]

... interesting ...

[@flatsurfaces1913]

Older gentleman do 😁

[@OldKing2]

nice title ;)

[@Blue.4t2]

⭐🙂👍

[@glennmoreland6457]

Good 🇬🇧😐

[@mykedindeal]

Nothing about indicator cosine error...😉🤣🤣

[@MrCrispinEnterprises]

Stylus within 10 degrees of the measurement plane should negate that!

[@Te4mUp]

A thou? M8 ain't you bri-ish? You off knockin around with them barmy yanks I reckon?

[@ShainAndrews]

A unit if measure that is not exclusive to "yanks".

[@MrCrispinEnterprises]

I think you'll find most British equipment and drawings from before the 1970's use imperial! As a collector of equipment from that period I have to use it. Cheers.

[@ronwilken5219]

@@MrCrispinEnterprises makes more sense to me than metricated aproximations.

[@billwessels207]

Are you aware of the fact that a neat clean and organized shop is the sign of a very sick mind. I have noted some of your quirks, eg hat flipping, feather duster in a machine shop etc. etc. Perhaps someone can recommend a proper pub and brand of suds for therapy!

[@MrCrispinEnterprises]

Don't worry, the duster is well and truly in the category of stage prop!

[@billwessels207]

@@MrCrispinEnterprises As we sometimes say in the states, "just pulling your leg a bit!. Or, " just yanking your string!"

[@ruffruff7063]

Put a pin up girl on wall . Every workshop I've been in had one and now I know why . Bar sag . Problems solved.