MEW 268 - THREAD Dial Indicator article

Just downloaded the above MEW No 268 and reading the dial indicator article.

Trevor sorry but so much is wrong in this . I am a novice but have much background. I hope many who read can assess the wrongly described situations. You mentioned Martin Cleeve's work and getting your head around it! Even my dyslexia usually only typing or writing found me re-reading one sentence 4 times on the dial engagment or disengagement??

I myself have to destress re-read often before posting even on our own blog, then I read it again.

Obviuosly editing just didn't happen here.

I've altered the title so people don't confuse it with the article about using a dial indicator to set a rotary table.

Thanks Jason.

I haven't read the article but on quickly scanning it there is an obvious printing error on page 23.

The second column has been printed in the wrong place.

Steve.

My apologies, it's a text flow error as Steve has spotted.

A classic example of seeing what I expected to see... because I have been through the text several times before it gets laid out I'm afraid that I must have been looking at the text and recognising the words as 'correct'. It's very hard to properly read something you have seen so many times before

Neil

Raymond , i wonder if a a discrete message to the editor may have been more plausible ? There is very little that can be done now it has gone to print except a note on the forum and in the next issue.

Other than what Steve has mentioned is ther anything else wrong with the article ? You mention that there is so much wrong with it so can you please point out everything you see wrong with it so anyone coming along who reads this thread or the article can understand what is going on .

Neil I know that during my time writing tech manuals and tour brochures seeing them over and over again.

XD351. I considered that BUT over the last few months we have been through much regarding a lot to do with so much regarding both magazines. Web downloads, access, postal issues this is not good and those who may not see the flaws in this article and are new could be turned off just as I was many many years ago as a very young lad.

Trevor has used the title "Using a Thread Dial Indicator"! yet has left out so much in his descriptive working of and jumped to checking of the Thread dial Indicator. Leaving out the half nut interaction with the hand wheel to move the carriage/saddle. He states about doing it from "a first principles" and wanting I gather to make it easier for those as confused as he was when he started out. I still am a novice but as stated have much background and training.

He mentions installing the TDI and lining it up to mesh with the lead screw?? I can not see how fiber washers would in anyway make lining it up on installation to mesh with the lead screw?? There is no mention of ever moving the dial indicator in or out to engage it or disengage it only about the half nut.

There is No photo showing TDI meshing with the leadscrew just the top of the TDI's.

The sentence & paragraph I had to read 4 times "With the half-nuts engaged the carriage, with the indicator, moves with the threads on the leadscrew and the indicator doesn't rotate"

The statement above gives the indication he has the TDI engaged or meshed!

2nd sentence " But when the half-nuts are disengaged the indicator dial rotates as the carriage moves along the bed"!! That is impossible, if the half-nuts are disengaged the saddle will not move and hence the TDI will not either.

From there on further statements are made regarding the correct use of the TDI but with no explanation only use of the half-nut and its use. Although he does say "leaving them engaged".

In checking the travel distance there is no mention of using the hand wheel to move the carriage/saddle don't forget he's trying to describe to novices those who are looking for guidance.

From there as Neil spotted poor layout/continuity of the article.
I struggled to continue to read through but did from there on. I was hoping to find something about using the TDI itself not mathematical formula nothing to do with the TDI itself.

Neil I know that during my time writing tech manuals and tour brochures seeing them over and over again.

XD351. I considered that BUT over the last few months we have been through much regarding a lot to do with so much regarding both magazines. Web downloads, access, postal issues this is not good and those who may not see the flaws in this article and are new could be turned off just as I was many many years ago as a very young lad.

Trevor has used the title "Using a Thread Dial Indicator"! yet has left out so much in his descriptive working of and jumped to checking of the Thread dial Indicator. Leaving out the half nut interaction with the hand wheel to move the carriage/saddle. He states about doing it from "a first principles" and wanting I gather to make it easier for those as confused as he was when he started out. I still am a novice but as stated have much background and training.

He mentions installing the TDI and lining it up to mesh with the lead screw?? I can not see how fiber washers would in anyway make lining it up on installation to mesh with the lead screw?? There is no mention of ever moving the dial indicator in or out to engage it or disengage it only about the half nut.

There is No photo showing TDI meshing with the leadscrew just the top of the TDI's.

The sentence & paragraph I had to read 4 times "With the half-nuts engaged the carriage, with the indicator, moves with the threads on the leadscrew and the indicator doesn't rotate"

The statement previous to that gives the indication he has the TDI engaged or meshed!

2nd sentence " But when the half-nuts are disengaged the indicator dial rotates as the carriage moves along the bed"!! That is impossible, if the half-nuts are disengaged the saddle will not move and hence the TDI will not either. Un;ess you leave the TDI meshed with the leadscrew and use the hand wheel to move the carriage, yet no explanation in doing so.

From there on further statements are made regarding the correct use of the TDI but with no explanation only use of the half-nut and its use. Although he does say "leaving them engaged".???

In checking the travel distance there is no mention of using the hand wheel to move the carriage/saddle don't forget he's trying to describe to novices those who are looking for guidance.

From there as Neil spotted poor layout/continuity of the article.
I struggled to continue to read through but did from there on. I was hoping to find something about using the TDI itself not mathematical formula nothing to do with the TDI itself.

 

Edited By Raymond Sanderson 2 on 12/05/2018 14:35:49

Edited By Raymond Sanderson 2 on 12/05/2018 14:38:23

It is standard procedure when fitting a TDI to use fibre washers between the TDI body and the apron to space the TDI laterally so that when the halfnuts are engaged, one of the lines on the TDI is lined up with the reference mark. Often when the halfnuts are closed, the newly installed TDI dial is indicating in between two marks. So you add fibre washers to in effect move the TDI along the (stationary) leadscrew, which rotates the dial, which brings one of the marks on the rotating dial into line with the reference mark.

I had to do this on my old Drummond after installing a new half-nut threaded insert, becuase the new threads were in a slightly different position from the originals. Also had to do it on our ML7 when it was rebuilt.

I haven't received issue 268 yet so can't comment on the rest of the article. It does seem that journalism and numbers are like oil and water, though. So I don't envy anyone who has to edit an engineering magazine full of dimensioned drawings and tables of numbers!

Edited By Hopper on 13/05/2018 07:11:57

Hopper couldn't this be achieved by simply turning the leadscrew until it lined up with the half nuts disengaged?

By the way thanks for your background on it I'd seriously not read this anywhere before.

I can understand if the TDI was being set up at a particular point say closest to the head stock or visa versa.

I'll say thanks I've had to write up Ambulance User Manuals and Service Data Manuals. Almost as bad as a Club Bulletin with the same.

No. Absolutely not. That is the point.

If you turn the leadscrew with the halfnuts disengaged until the TDI marks line up, if the TDI is not correctly spaced with fibre washers, when you try to close the halfnuts they will be out of mesh with the leadscrew. Then when you move the carriage, or rotate the leadscrew, that half or quarter of a thread left or right so the halfnuts can engage, the TDI dial rotates and the lines get out of line. Hard to explain in words without diagrams etc. Best go out in your shed and have a look at your lathe.

In essence, the stationary leadscrew acts like a rack as the carriage is moved back and forth by the carriage handwheel and the halfnuts disengaged.

But once the halfnuts are closed and the leadscrew is then rotated to move the carriage along, the teeth of the "rack" stay in the same position relative to the carriage, because the carriage moves along with the thread. Try it and observe on your lathe next time in the shed.

I once had a job writing the service manuals for Collins Class submarines when they were built here in Oz. I would hate to be stranded 20,000 leagues beneath the sea and have to rely on that lot to extract myself from the fertilizer!

Edited By Hopper on 13/05/2018 09:26:18

Think of a stationary nut with a bolt disappearing into it as it is screwed in. Does the thread disappear at exactly the same place irrespective of where the bolt may be turned. You bet it does! Simple mechanics. Same applies here.

Isn't it easier to loosen the dial on it's spindle and just turn it so one of the marks lines up with the notch? mine is just fixed by a simple screw.

Also why fibre washers which may flex, metal shim washers would surely be more rigid.

I'm thinking of Myfords here, what I'm currently familiar with. So the dial is not adjustable like that. Why fibre indeed. Just because that's what Myford seems to have used and when you nip up the nut, the TDI stays in place as the friction of the fibre washer between TDI and apron is greater than the friction of the steel nut being tightened. Maybe. Can't see any flex likely in such a low-stress application. But I'm sure steel washers would work too.

The other problem with using shim washers would be if you had a lathe that had more than one gear for the indicator which would be a right faff having to shim it each time you needed to use the correct gear for the thread being cut. maybe the fibre washers are just standard practice on Myfords.

Certainly standard practice on my Myford which it retains its original fibre washers from new. (It's a late model ML7). I admit to not doing any thread cutting which probably explains why they have not worn!

I agree with Hopper's reasoning behind the mode of adjustment adopted by Myford (and others? ).

Pero

I don't have my copy of MEW268 yet, so can't comment specifically on the article. But I don't recall having any problems using the DTI on my lathe when screwcutting. There are definitely no shims anywhere. I suppose that if it was important to move the dial without moving anything else I'd just loosen the screw that holds the dial in place.

It all sounds so complicated; I'm just glad I binned the DTI and fitted an Ainjest unit instead. I didn't actually bin the DTI; it's sitting on a shelf above the lathe along with the Dickson toolpost I never bothered to fit.

Andrew

Ah Hopper so why is it stated in a way that fibre washers are only used IF required seems to mean No washer at all might work??

Mine doesn't have a fibre washer but a shim and a spring washer on the nut side. I can not see what good a fibre washer would be on the nut side. Of late the retainer tension nut is not holding it tight enough to maintain connection with the leadscrew, that is going to cause trouble.

In practice as Jason said fibre washers crush and over time will wear to point of disintegration by constant movement.
The slightest wear on the half nut or backlash will make alignment an issue between the leadscrew and the spur gear of the TDI.

Even the paragraph title misleads.
"What is a Dial Indicator" A dial indicator is a device which ??

below borrowed from http://www.americanmachinetools.com/how_to_use_a_lathe-2.htm

Has anyone ever engaged the TDI first then the half nut??

So you don't have a fibre washer between the TDI body and apron, but now you are having trouble with the unit not being held tight enough? Try replacing the metal shim with a fibre washer. They slip less than a steel shim.