Worth mentioning if you happen to have lathe DRO you can dispense with the dial gage measuring along the bed which is probably <2" displacement anyways & subject to alignment errors in 2 planes. Then you can utilize the full length of compound which will increase accuracy because its probably 4X longer, providing the traverse gage is accurately aligned. Lots of ways to skin the cat. All this compound fiddle farting is why I lust for a taper cutting attachment. NEXT lathe lol.
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Tool Tools to set angle on compound fairly accurately?
- Thread starter StevSmar
- Start date
Tool
Tom Kitta
Ultra Member
It is very easy and quick to check the angle this way - on the DRO you see one leg of the triangle, on the indicator you see the other leg. Now using basic math you can get the angle precisely.
But to set the angle you may need to do it few times. Each time getting more precise.
This comes in handy a lot - a lot of tapers need to be quite precise.
I guess you could try to do the same check with taper attachment.
Why wait? Make your own TTA. I did.
I've never worried about that other than an initial check when I first got the lathe. Either Gibb method depends on locating the compound via the opposite slide and neither one distorts the compound in any meaningful way. Maybe I am being overly optimistic or missing something though.....
If you have a set of angle blocks, just attach the appropriate angle block to the side of your compound, then move the cross-slide forward and back while nudging the compound until the indicator reads zero. In this particular case I had to make a 14.5° angle plate to do an internal acme thread, and it's held in place with a magnet.
Therefore, no math!
Therefore, no math!
Attachments
I was going to mention how lucky those are who have a DRO, but I provided my method in order to help @StevSmar who was interested in seeing how its done using indicators and Trig.
Now, if only there was a convenient way to mount a DRO Scale on the compound! If I recall correctly, my Ditron has a setting that will calculate the angle directly. I do plan a scale inside my cross-slide, and I'm thinking that a digital edge finder could be used to measure the length of the opposite side of the triangle. (touch off, move the carriage, touch off again - the difference is the length)
I think I'm about to learn something....... Other than the additional resolution provided by the extra length, why is measuring the angle of a taper attachment any less fiddle farty than measuring on a compound?
PS - I don't have a taper attachment either. They are still available for my lathe ($$$) and time is slowly closing on my ability to get one. So your answer might be pivotal for me.
I got it, and a bunch of other dibs and drabs from my dad years ago. And he had it for years before that.
I see. Nice!
How well do the blocks stack using that magnet?
I see your compound has degree marks all the way around! VERY NICE! Another project I have to finish this summer.
Why the sad face? He's still alive and kicking. Well, maybe not kicking, but alive! He turns 89 in August.
When I spoke in another thread of how much I like the taper turning attachment I have, I don’t think I highlighted the contribution the DRO makes for me to make the job easier.
Before DRO I was doing the indicator shuffle but now there’s no comparison for speed of setup or resolution (and hopefully accuracy!) obtained from the DRO for the reasons @PeterT talks about.
@Susquatch Since you asked, for me the DRO/TTA combination lets me measure both the carriage and cross distances to the accuracy of the DRO (purported to be 1u) and get the angle. The only fiddly part is zeroing in on just the right adjustment of the angled slide but you have to do that anyhow.
I set the carriage travel to as long a distance as practical then tweak the cross measurement (via the angled slide) to obtain the correct sine travel for my angle - always using the same carriage distance. I don’t but you could set two hard stops on the carriage to define the cosine travel while you’re doing the setup.
Make sense?
D
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For those without indicators or gauge blocks, here is another way to set a compound angle for cutting tapers.
If your hand wheels have reliable graduations, you can use them to measure the sides of the triangle. The carriage movement can be read directly to get the length of the adjacent leg. A digital edge finder works perfect for consistent measuring of the cross-slide movement to get the length of the opposite leg, but almost any method of displacement detection will get you within a degree or so.
As always, when using the hand wheel dials, don't forget to take up the backlash.
If your hand wheels have reliable graduations, you can use them to measure the sides of the triangle. The carriage movement can be read directly to get the length of the adjacent leg. A digital edge finder works perfect for consistent measuring of the cross-slide movement to get the length of the opposite leg, but almost any method of displacement detection will get you within a degree or so.
As always, when using the hand wheel dials, don't forget to take up the backlash.
I have a plan. The swiveling rear bar isn't a big issue (I've stored some of your good ideas). Its how to implement the temporary detachment of the cross feed nut from cross slide & then returning it back to normal mode when taper cutting is done. It will involve mods to the cross slide & nut, so being precautious to the point of inactivity haha. I'm going to pull it apart again anyways to replace the nut & possibly leadscrew once the wear gets to irritation level as both are getting worn. So I'll have a closer look at the table underside to confirm if my idea will work. Mostly its a matter of sucking up the kahunas.
The design for the one for my lathe is permanently attached in use. No need to disconnect. If you want I could send you what I have on it.
Tom Kitta
Ultra Member
Yeah but the problem is the super strange angles that seem to be used.
Sure send away. I've looked at a few designs but that doesn't mean I've seen them all. Ideas always welcome. Some are telescoping leadscrew assemblies where the threads are always in the nut, but there is another mode of disengagement. Some are what amounts to undoing the fastener that engages the nut to cross slide underside (more or less what I'm thinking of). Ultimately the table has to slide independent of the screw, only guided by taper bar & arm.
If I understand how mine works, the screw is referenced to the taper attachment so the attachment has to be set at zero to get regular use of the cross slide. In use, the taper attachment moves the cross slide according to its position along its length and the cross-slide screw moves it back and forth from that. In effect, total cross-slide displacement is the sum of the taper displacement plus the screw displacement.
ChazzC
Ultra Member
I'm going to call KBC on Monday to see if they will add one of these to a back order that I've waiting for. On second thought, maybe I'll get several so I can sell them on eBay at a substantial profit (only US$11.95 from KBC, although their shipping can be high):
Since mine will be new, I should get even more!
I think this is the most important part of the discussion. Measuring lengths is so much easier and more reliable than measuring anything else, that it should always be the way to go.
And the accuracy improves to an almost unlimited degree by measuring larger and larger triangles.