Coax indicator design

[BillTodd]

Post picture of the conversion 

[BillTodd]

Kwackers had a good idea in another forum. Adding a spring and ball to push the body towards the rocker so it can be used horizontally. It will also pre-load the shaft so reducing any wobble caused by the force from the rocker.

[winklmj]

What are you making your probes out of? I scored a used Blake off of Fee-Bay sans the probes. I made a straight one out of some bronze. Would hardened drill rod be any better?

The Blake eats up a lot of Z-axis so one of yours is on my project list.

[BillTodd]

I think it was a piece of silver steel, but anything reasonably stiff would do.  Drill rod would be perfect

[winklmj]

Made a curved one out of bronze again and tried it. Just one use against a piece of aluminum had put a tiny flat spot in it. So I made some out of drill rod and hardened the tips:



Freehanded everything so there are some goofs but the ball-ends are pretty smooth.

[Bezalel]

a little late to jump into this thread maybe, but I've only just  seen it. and  must say I realy like it 

Bill,

I know this depends on the length of the bar, but in the configuration shown what sort of displacement of the meter do you get for say 1 thou of error?

(Nice job btw!)


ATM 10thou" of displacement caused and indicated 3 thou on the DTI (which would be doubled as run-out). I suppose a quick improvement would be to swap the cheap DTI for a tenths indicator.

I'm thinking when I build my own I will be looking at reducing or eliminating the  resolution reduction of 3:1

by this I mean it seams to take 3 thou movement on the job to register 1 thou on the dial.

The length of the pickup has significant bearing on this



If the probe length is adjustable to approx half diameter of the job and rotated to be horizontal, such that it is pushed end on, the acuracy of the dial increases accordingly.

for unity resolution of the dial or better. can anyone think of any reason this couldn't be done here?

[BillTodd]

If the probe length is adjustable to approx half diameter of the job and rotated to be horizontal, such that it is pushed end on, the acuracy of the dial increases accordingly.

Yes, sort of. To work out the exact ratios you'll need to work out the effective lengths of the levers rather than the actual the lengths of the levers, but in principle the shorter the  measuring arm the more the dial will move for a given displacement.

Another way to increase sensitivity, would be to change the angle of the taper on which the ball runs; If this were greater than 45° it would push the DTI slide further (you will need to stick with my original stepped design to ensure the ball is supported on the other side of the taper). It may even be possible to use a curved taper to compensate for the change in lever angle.


Alternatively, it would not be impossible to make a compound lever mechanism to increase sensitivity , as Richard Shute suggested earlier.

[bp]

I've been a'wondering about this for a while.
"Wondering 1".... was to use a DTI rather than a Dial Gauge and run the probe on the lower face of a groove in the main shaft.  The ultimate version of this used a washer from a thrust bearing, as they are ground flat etc etc
"Wondering 2".... was to use a cranked lever to activate the Dial Gauge, as has been previously mentioned.  Fiddle about with the ratios to get a more favourable stylus movement/indicator movement ratio
"Wondering 3".... Bill, in your last version, the one with a ball riding in the groove, the side loads on the indicator must be considerable, or is the indicator probe well located so that it can only move in and out, if you see what I mean?
cheers
Bill Pudney

[BillTodd]

I've been a'wondering about this for a while.
"Wondering 1".... was to use a DTI rather than a Dial Gauge and run the probe on the lower face of a groove in the main shaft.  The ultimate version of this used a washer from a thrust bearing, as they are ground flat etc etc

Yes, that should work well

"Wondering 2".... was to use a cranked lever to activate the Dial Gauge, as has been previously mentioned.  Fiddle about with the ratios to get a more favourable stylus movement/indicator movement ratio

A lever is certainly possible (the DTI above has this same lever built into the device)

"Wondering 3".... Bill, in your last version, the one with a ball riding in the groove, the side loads on the indicator must be considerable, or is the indicator probe well located so that it can only move in and out, if you see what I mean?
cheers
Bill Pudney

The only side load on the indicator, that I can see, is from the friction with the ball as it spins (if it spins?) which is lubricated with a hardened point contact. I don't think it's a cause for great concern .

Bill

[BillTodd]

I have decided to put my prototype indicator up for auction on ebay to raise money for the Royal British Legion's 90th anniversary appeal.

http://www.britishlegion.org.uk/support-us/how-to-give

It should be listed by Thursday (I'm just waiting for the Ronseal to dry on the wooden box - posh or what  ) all the profits will go to the charity (I'll pick-up the auction and paypal fees, the winner will pay the postage).

[slowcoach]

A very worthy cause 

[BillTodd]

A couple of pictures of it in the box:

[BillTodd]

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=200657351320

ebay auction is now active you have ten days to bid

I've started it at 99p (I'd like to see an early bid of at least a tenner ) .

Bill

[Divided he ad]

Looks like it's going well Bill.... 7 days left and £51 already!! got to be worth well over the £100? 


I haven't the funds for even the £50 but it's a great job in the building and then the selling on   



Hope it goes for stupid amounts of hard cash 





Ralph.

[BillTodd]

Well, it sold for £72,  which I think is excellent 

I don't know if Ralph, the buyer, is a Madmodder or not but many thanks Ralph. It'll be on its way tomorrow or, if the post office is closed, Monday .

I hope you'll find it very useful :cheers:


Thanks to all those who bid and gave support

Bill

[woodguy]

Well done Bill.

What does the current incarnation of the design look like?

[Xldevil]

Well, it sold for £72,  which I think is excellent 

I don't know if Ralph, the buyer, is a Madmodder or not but many thanks Ralph. It'll be on its way tomorrow or, if the post office is closed, Monday .

I hope you'll find it very useful :cheers:


Thanks to all those who bid and gave support

Bill

Of course I am,Bill.
Hope You'll offer me some help if needed.
Cheers,Ralph

[HS93]

Well, it sold for £72,  which I think is excellent 

I don't know if Ralph, the buyer, is a Madmodder or not but many thanks Ralph. It'll be on its way tomorrow or, if the post office is closed, Monday .

I hope you'll find it very useful :cheers:


Thanks to all those who bid and gave support

Bill


Have you thought of making a few more ? I was the out bid at £70 ish via some one was biding for me, but if there where some otheres being made i would be able to save up if they where a bit more expensive.

peter

[BillTodd]

Of course I am,Bill.
Hope You'll over me some help if needed.
Cheers,Ralph

Always happy to help, Ralph. Just ask

[BillTodd]

Have you thought of making a few more ? I was the out bid at £70 ish via some one was biding for me, but if there where some otheres being made i would be able to save up if they where a bit more expensive.

peter

I'll have to get my second Haighton Miller up 'n' running first and then find a source of cheap bronze & SS etc. etc.

[BillTodd]

Just a qucik update:

Missionfish, the company that runs the ebay charity donation system have finally taken the money from my paypal account.

However, it appears that The Royal British Legion will not actually receive the donation until December 30th (a 45day delay to allow refunds, apparently). I can only hope Missionfish give a proportion of the interest accrued on their holdings  to the charities (else I'm not sure I'd use the ebay method again!)

Bill

[Davo J]

Bill, this may interest you
http://madmodder.net/index.php?topic=6246.new#new

Dave

[BillTodd]

Coax V2 coming soon....

[zimma]

Hi chaps,

Just a quick hint for those of us with limited Z clearance, or with a round column mill that loses accuracy when changing the height of the head (because of that limited clearance).

I have an MT3 spindle in my mill. If I use a 10mm MT3 collet to hold the coaxial indicator directly in the spindle, and not in a chuck mounted in the spindle, then the touchdown point of the indicator probes is pretty similar to the touchdown point of an endmill in a collet chuck.

I had always struggled with Z axis travel as I used to just swap the coaxial indicator directly for an endmill in my ER32 chuck until i realised I could gain the whole length of the ER32 chuck by mounting the indicator directly in the spindle with a collet.

Hope this helps

Graham

[BillTodd]

Hi Graham,

Good advice

The coax indicator above was designed to work with my Haighton mill which has even less Z clearance than my RF30*.

Even if made a collet for the Int30 spindle taper a normal Blake's type coax is too tall to be of any use. The one above sticks out about 3" from the chuck with the shortest probe.


Bill

*incidentally, I have fixed my round post problem with a wish-bone stabiliser