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Member postings for nick Clark

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

Thread: Myford Super7 Leadscrew Accuracy problem
31/12/2009 17:27:27
Hi,
Thanks for all your replies on this problem, I could not see what was wrong so I read some of your replies out to my mate over the phone and he offered to let me try a new (spare) set of nuts for it which he had. we tried them in the lathe today and found the following.
We looked at the new and the old and the only difference was a slight bend in them only visable against a new set which is why it could not have been getting full engagement in the root of the leadscrew without having the adjustment slightly less engaged.
I can now confirm that the leadscrew is ok as I have checked it and the pitch error has gone. Also with the new nuts the handle is in a lower position than before confirming a lower engagement in the leadscrew.
Thanks for all your help in this problem I can now cut perfect threads with a bit of luck!
I hope you all have a Happy New Year
Regards
Nick
 
29/12/2009 11:36:56
Hi,
I have done a new test this morning and have checked the clock and for a known movement (on my Mill) it is giving the required reading so I am at the moment not suspecting the clock?. The Myford carriage moves freely and adjusted gibs so no play (bed just reground by Myfords)
The test I have done involves placing the clock on the bed and whilst turning the leadscrew in one direction I expect a movement of 125 thou(1 turn of handwheel).
I got readings like this as progressing along the travel
0.126"
0.125"
0.128"
0.128"
0.127"
0.123"
I am wondering if its the leadscrew worn in places ie the helix angle is changing due to wear causing the plus minus error?
I have been told that myford leadscrews have an accuracy of 2thou / foot so I am getting some pretty bad readings if thats the case.
How I first came to find the problem was my friend cut a 20tpi screw on a myford (super7 box type) and my Super7 changewheel type is finding errors as I run along due to my feed/rev being wrong. If i set for a feed of say 0.500" I get 0.490"?
This is how I came to suspecting the leadscrew? or nut? as the leadscrew seems to be out.
Any Ideas or further checks would be gratefully received
Best Regards to all.
Nick
28/12/2009 20:42:07
Hi to all,
I am having trouble with the rated accuracy of my Super 7 leadscrew (8TPI) as im getting weird figures on the clock.
I have the changwheel type of lathe but I have disconnected all of the gears so its just the leadscrew under manual control (using the leadscrew handwheel).
I am getting figures of 5 thou out over a 1" dial guage travel.
If this figure were to translate into cutting a long screw ie a foot long then the pitch would be seriously affected.
Can anyone confirm their measurements of the 8TPI leadscrew accuracy using just a clock and turning the leadscrew by handwheel grads.
Any info as to what other people find would be very helpfull.
I have inspected the clasp nuts and they seem to be ok by eye.?
Regards to all
Nick
Thread: BA Threads or Metric Threads?
15/07/2009 21:04:35
Hi,
Thanks for all the info its a great site,
When you say BA threads are metric based what does that mean?
And the last question or point is regarding Jims Post he says
"You will find that it is all BA nuts and bolts that have been scaled to suit the model engineer"
Does this mean there are all different sizes of nuts for say a nut of 6BA.
What Im trying to say is if I bought a 6BA brass nut from one supplier and then later got another supplier will they all be the same or scaled differently from each supplier?
Perhaps im getting confused?
Thanks for all the replies so far .
Regards
Nick..
11/07/2009 21:18:54
Hi,
Im new to model engineering and so far I have only dealt with Metric taps and Dies for thread cutting.
Can anyone tell me why model engineers seem to use BA threads as opposed to Metric equivilents.
Are BA threads popular in model engineering as someone told me that BA is obselete now as it was phased out in 1966?
I dont want to purchase taps and dies if its not really something that people use anymore in Model engineering?.
If anyone can enlighten me I would be gratefull.
Regards
Nick
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