Author Topic: Top slide angle  (Read 4145 times)

Arbalest

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Top slide angle
« on: May 05, 2015, 07:00:30 PM »
Parts of the scale on my top slide have the numbers/divisions rubbed off anyway but how do folks accurately angle their top slides?

Online Jo

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Re: Top slide angle
« Reply #1 on: May 05, 2015, 07:02:11 PM »
I ignore the numbers which are normally wrong and use a Vernier protractor.

Jo
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Offline KB

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Re: Top slide angle
« Reply #2 on: May 05, 2015, 07:07:36 PM »
Set a dial indicator on the bed, perpendicular to the ways with the tip touching the top slide.
Move the carriage three inches and a little trig will tell you how much the dial indicator should move.

Offline mklotz

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Re: Top slide angle
« Reply #3 on: May 05, 2015, 07:08:39 PM »
There's an ongoing thread on this topic over on HSM...

http://bbs.homeshopmachinist.net/threads/66821-Worn-degree-marks-on-compound

but I agree with Jo and many of the contributors to that thread that use of a good protractor is a much better solution.
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Offline Dave Otto

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Re: Top slide angle
« Reply #4 on: May 05, 2015, 07:13:42 PM »
If I'm being picky I do just as Kevin B has described.  Most of the time I trust that the Germans who made my machine put the marks in the correct spot.  :lolb:

Dave

Offline arnoldb

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Re: Top slide angle
« Reply #5 on: May 05, 2015, 08:23:15 PM »
As usual, "It Depends" on what you have available, how much accuracy you need, on the angle itself, and on your lathe  ;)

I prefer my vernier protractor as well, but for shallow tapers like Morse, it becomes impractical to use, as things get in the way.  Then the simplest solution is to just use a known-good Morse taper and a dial indicator to set the angle.  For this, the indicator must be mounted as close to horizontal center line as possible - a good idea here is to use a flat foot on the DI; makes it much more accurate.  Marv has an article on that somewhere; I can't lay my hands on it right now.

Kevin's method works well too - once again, the DI needs to be on center line, and you need to be fairly accurate on the length you travel with the slide to set it.  On smaller lathes this can become a problem - there's not much travel on the top slide - especially for shallow tapers (close to parallel to the workpiece).

If you have precision triangles, those can also be very useful in setting the angle, especially if you can confirm if the side of your top slide is parallel to the top slide's dovetail.  And even if there's an error there, it's easily compensated for.  If you don't have precision triangles, it's very easy to make up your own that's usually plenty good enough for hobby use - it just involves a blank piece of material with three fairly accurately drilled holes and a milling machine - and some math.

 :stir: For the "new age" machinists, some food for thought:  A laser pointer can be used to set an angle pretty accurately; and I have my own ideas around that.  There's some "off the wall" thinking required though  :mischief: - oh, and some more maths...

There's many more ways to get the job done - and no definitive "right" or "wrong".  At the risk of putting both my feet in my mouth and falling flat on my @rse:  One thing I've learned about hobby engineering is that often times "close enough" is "plenty good enough".  It's nice to work down to the absolute precision one can obtain, but there's no use in chasing absolute precision to the point where one gets to the point of "I can't do xxx because my machines/measuring equipment/skills aren't accurate enough" - then you'll never get anything done.  Just go ahead and try the best with what you have - you might be pleasantly surprised at the results  :)

Kind regards, Arnold
Building an engine takes Patience, Planning, Preparation and Machining.
Procrastination is nearly the same, but it precludes machining.
Thus, an engine will only be built once the procrastination stops and the machining begins!

Offline mklotz

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Re: Top slide angle
« Reply #6 on: May 05, 2015, 08:56:42 PM »
  There's some "off the wall" thinking required though  :mischief:

Chuckle.
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Arbalest

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Re: Top slide angle
« Reply #7 on: May 05, 2015, 09:19:32 PM »
A few ideas there, thanks.

Offline tangler

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Re: Top slide angle
« Reply #8 on: May 05, 2015, 09:50:55 PM »
These are quite good http://www.axminster.co.uk/gemred-digital-angle-rule.  Supposed to be accurate to 0.1 degrees



If more accuracy is required then its the dial gauge and trigonometry.

Cheers,

Rod

Offline Stuart

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Re: Top slide angle
« Reply #9 on: May 06, 2015, 07:29:15 AM »
Or use a sine bar with Jo blocks

Stuart
My aim is for a accurate part with a good finish

Offline Jasonb

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Re: Top slide angle
« Reply #10 on: May 06, 2015, 09:40:57 AM »
I would say 90% of the time I just use the scale on the topslide for what I do. Most tapers seem to have a matching male & female part so as long as you don't move the slide they will match perfectly and 0.5deg either way won't matter. Or the actual taper is not really that critical like a carb venturi or a decorative taper on a shaft.

For when it does matter I would reach for one of the veneer protractor or dti and trig

Arbalest

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Re: Top slide angle
« Reply #11 on: May 06, 2015, 10:07:43 AM »
Well done Rod, I've actually got one of these somewhere. Keep forgetting about it...

http://www.machine-dro.co.uk/digital-protractor-angle-finder-graduations-200mm-moore-wright-506-series.html

I've only a 8 x 14 but there should be enough room to use it easily.

Offline Ian S C

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Re: Top slide angle
« Reply #12 on: May 06, 2015, 01:34:16 PM »
I have a couple of jobs that come up that require a taper(not too critical), I'v made a couple of templets of the required angle so that I can quickly set up for the cut. They are just cut from sheet stainless.
Ian S C