Member postings for Robin teslar

Well said John

Certainly even the cheapo digital calipers have their place for say - spot measurements, having zeroed first and moved SLOWLY to the measure point, but from my experience I wouldnt trust the incremental type on say DRO applications where you could scrap your work or damage the machine.

BTW, we are addressing the linear encoder, there are rotary encoders available quite cheaply and by their nature they can be easily made as absolute position indicators (see Gray code in google). To my mind these are much more robust and foolproof - no exposed sensor elements and fundamental absolute accuracy.

Have to see what the DIY market can offer

Allow me to say, guys, that the anomalies that i observe are more like step changes say 0.15mm instead of zero. not consistent. My caliper is gerally clean, but will try some spirit. I think it has more to do with the speed at which i close to re-zero the device, maybe it cant keep up, not that i am rash of course.

A salutory observation I think. One step forward two steps back

Cheers

Robin

Thats a very sound suggestion, will look into it tx

Hi is this 50 shed of Myford?

Yes any insulation is better than none (provided is doesnt suffer wetness), but with all sheds, garages, outbuilding, they will have many sources of wind leakage, and these really must be thoroughly sealed up if you are to benefit form conserved heat, otherwise a windy day will just whistle your heat away in a heartbeat - its not as easy as it sounds.

One method to consider would be to get a PU foam installer to coate the inside surfaces with 50mm spray. It certainly works and is quick. You can buy the DIY semi pro kit yourself for ca £250. I dont advise those nasty spray cans - very poor results generally - nozzle blocks quickly thru atmospheric moisture, you have to use it all in <10mins. Wear goggles and gloves as its a deveil to remove from skin

Cheers

Robin

Ive had similar problems. A lot of publishers rely on inertial selling (on line newspapers are a glaring example where they off 3 montths subscription at say £1 per issue say vs £2.50. But unless the practically give notice of termination straight away, they fudge the issue and continue billing your credit card. I would NEVER sign up to a deal like that. Just plain dirty tricks

Hi Myfordians

Im sure we are all aware of the plethora of cheap digital measuring devices available on Ebay all from PRC of course. The probelm I find with my digital caliper is that the zero can inexplicably change, sometimes quite drastically in the course of measuring. Of course I make it a habit to close and zero the reading each time (essential imho) but it certainly detracts from the usefulness of the device and that you could end up with scrap if you forget to check zero each time. Course, never got that with a vernier caliper.

I understand the basic the simple micro slice scale that it uses (is it optical?) and that it is inherently relative, but there are better systems that use an absolute scale. Can anyone suggest a caliper like this (Mitutuyo? serious cost)

Certainly I couldnt possibly trust this system for any machine mounted DRO

Am I missing something, should i go back to my vernier caliper and get much stronger spectacles

Robin

Hi, hope this isnt a dumb question but cant fint it in the Myford manual (lots of basic info missing from that book).

I have followed various thread on how to measure wear on your lathe eg mic the far end outside of the bed, then mic the bit ca 2" from the chuck (presumed to get the most wear

It seems to me that the inside faces of the bed dont get any sliding wear, so should be a suitable datum to measure other factors, such as using a parallel test bar

Any ideas?

Cheers

Robin

Hi Myfordians

I noticed on my venerable ML7 that I have rather more end play than desirable and would like to tighten it up. Having looked at the gear with a slotted grub screw tapped endwise on the mandrel, and also the steel thrust collar with grub screw, so its not quite so simple. Before messing about in ignorance, would any kind users please suggest my best move. If its covered elsewhere, apologies please advise link

Cheers

Robin

A valid point MG

I have never worked with an un-numbered scale but its worth having a feel of this - would I lose my way?

Dont know till I try

The OP has certainly produced some interesting observations and I am totally blown away by the geared scales but as said maybe too much play would detract from the benefit. I'll just knock up a test sample

BTW messing around with an ML7 is what floats the boat. I could have bought a modern machine with full DRO for less that the total cost of my old Myford but it wouldnt be the same as when I started out in a machine shop

So I recycled a jam jar lid from the kitchen pedal bin and here we have an un-numbered 254 grad scale. The print needs adjustment but it can work and cost me nothing

Robin

Yes thats true <1 rev BUT when you are turning down a diameter towards the last few cuts then you re-zero the dial each time so its not really that limiting. I also realised that Ive got the scale upside down and I also need to divide by 2 to give a diametric read out rather than straight radial. More work needed

I think I might as well make a dual scale for IMP/Met diametric readout

Yes the dial gauge is essential also but doesnt divide by 2 (although I think Ive seen a DRO that does? cant remember where)

I have a battered Mitutuyo which readsout to 5places absurd accuracy but it was only a fiver on Ebay

well here's my attempt at the metric scale .01mm scale, i cant seem to attach a dwg so a jpg has to suffice. Its intended to fit on a 50mm wheel

somethings slipped in the jpg and I could fix it but it shows the method

At either end there will be a blank area not intended for use, but you can get +/- 1.2mm

Robin

B

do you means this dial from RGD

http://www.ebay.co.uk/itm/RDGTOOLS-ORIGINAL-SHERLINE-LATHE-CROSS-SLIDE-DIAL-just-one-cross-slide-dial-/291083097218?pt=UK_Home_Garden_PowerTools_SM&hash=item43c5e79482

Robin

Yes quite right B

In fact its just dawned on me that you will never get a full 360 out of the scale. You will be limited to say 250 divs

but it will be accurate as .25mm/div but in fact I want the scale to read diametrically rather than radially, so I dont have to keep dividing by 2 so maybe I can make a scale for 0.1mm on diameter. I'll do a dwg for the scale on 50mm diameter dial tomorrow and post it.

Robin

Well thanks for the tip, yes ML7 I didnt expect the mechanism to be so crude and that dial is pretty naff

In my machine shop years, I always worked on much bigger machines and never gave this trivia any thought

With an ML7 you have to be creative in unexpected ways

Cheers

Robin

Seems a daft question, but I cant see how the handle is secured to the cross slide lead screw. There are no obvious pins or grub screws, just solid metal. If it were just screwed onto the shaft then , even with a lock nut , it would tend to come unscrewed with use

Anyone any ideas?

Robin

I am afraid you are taking me too literally at the moment, I want to check my own ML7 tomorrow and come up with a proper design with say 254 increments/rev, so that gives about .025 mm/div on diameter. Its all about scaling

and that would give .1mm for a major div (multiplied by 4). A 50mm dia collar would give div spacing of 2.48 mm. But I'll have another think about it , too cold out there now

Robin

Hi FB

I think this approach has already been well covered on here. These cheap digital calipers can make a cheap DRO but they are not very reliable, fragile and dont always hold their original zero reference correctly especially after powering down automatically as they do. From expereince, I dont trust them for continuous work. The old fashioned mechanical clock gauge is far better (provided it runs smoothly and hasnt been abused - like allowing it to spring back too quickly

Agreed JB, the slide movement will be the same, but its how it is represented on the circumference of the wheel.

Divide by PI gives a diameter ratio of 1.105, So we want 3.175 to fit on a diameter which gives say 100 convenient divisions, the factor is 1/3.175 = 0.3149. So a 94.49 mm circumference wheel gives a diameter of 30.07mm

So print a strip 94.49mm long and divide into 100 should give increments of 0.3mm per division, actually more convenient to divide by 2 and express as a reduction in diameter when turning as we normally do with a cross slide

This is just off the back of an envelope and I need to play around with the factors and diameters a bit more to get say .025mm and 400 divs/rev

equiv to ca 1 thou per division

I can print this out on CAD and stick is to the wheel, then punch grads through the paper onto the wheel, its not rocket science, Ive got the AL billet ends sorted and can make one for each slide and maybe one for the leadscrew handwheel

Hope you get the idea and the collar can fit right over the existing wheel

Robin

Hi My Fordians (ML7s)

If I won the lottery, then I'd have two sets of machines in a warm workshop Imp/Metric. Thats not going to happen

A lot of my work comes in metric designs and of course my trusty old ML7 is in glorious imperial fettle. We all know what rubbish the stand cross slide micro wheel is. I always use a dial gauge, but I was used to a proper micrometer wheel on my work Harrison. So I looked at what the usual vendors offer and its £25 for a replacement metric wheel, in fact you can pay nearly £100 for a replacement lead screw/nut assembly.

It seemed to me that it should be within the purview of the average hobbyist to make his own conversion wheel. Its a matter of matching the wheel diameter vs leadscrew tral to correspond to an exact number of wheel graduations and make up a collar to fit over the existing handwheel.

How to make the graduations, well I have got a full ML7 dividing head but the seems overkill and probably take me all week to get it set up.

So I thought I would make the collar out of a suitable blank, attach a paper printed scale around the circumference then put protective perspex cover over that, then I thought I would go for gold and make two scales (on different diameters IMP and MET)

Has anyone else tried this?

Any tips to speed up the design process, much appreciated and I am happy to share my design results if successful.

Cheers

Robin