# what to do with a free scrap dumpster find ?

10 Nov 2021 08:51 #225939 by andypugh
I made several bits of tooling at the wrong angle.

Because (atan(7/24)) / 2 != atan((7/24)/2)

atan(7/24) / 2 = 8.1301 = 8° 7' 48.36"
atan((7/24)/2) = 8.2971 = 8° 17' 49.56"

The second angle is the correct one.

10 Nov 2021 09:21 #225942 by rodw
One mathless way to cut a taper if you have a conventional tailstock is to set up a sine bar parallel to the tailstock quill and adjust the compound  so the sine bar is touching the compound. I machined a little jig to rest the sine bar on that hooked over the edge of the compound for alignment and put the sine bar at the right height.. The result was a perfect taper!..... if your quill is concentric with the spindle which it should be by definition.

So all you have to do is select the correct sine block!

10 Nov 2021 09:28 #225944
yeah something in the math for the theory is a common mistake many make including myself . i looked at it from a simple right triangle but that was wrong. that was 8.1301 degrees and the right one would be 8.2972 degrees. i was right in the middle of both of them

i matched mine to to holders i have which is not ideal but i figured it was the best way to make it work with next to nothing

most angular dimensions are +/- 30 minutes so being off 5 minutes is pretty darn close.

10 Nov 2021 09:43 #225945
Rod when i turned the outside i took the tapper out of the turns on the shaft with my tailstock. i never tried doing a tapper that way my little lath is converted to CNC so no need. when i worked at the industrial pump plant we would program the straight turns at a slight tapper to remove any tapper in the shaft. pretty common with a 14 foot long shaft so it was an easy fix.

i was always under the impression the tailstock method was used for slight tappers but i never did much that way on a manual and just kicked the compound for all the stuff i did. depends on the type of work your doing i guess

10 Nov 2021 10:12 #225950
best way to tell is to mark a holder up with some high spot blue or something like it and see how it makes contact. it's cheap and effective. if it hits in the front the angle is too steep and if it hits in the back your to shallow on the angle. after 31 years doing machining in general perfect to a micron or two is not done with general machining. center height of the tool and deflection of a boring bar can throw you off. heck i had to finish by cutting dust to keep the shaft from moving while cutting. depends on the type of steady rest you have? the roller bearing type would work better but i am not lucky and was stuck with light support and grease on the shaft. to much pressure and the shaft gets warm and that's not good when you are trying to work to 1 or 2 tenths

perfection is tough in the real world so doing your best with what you are working with is all you can do in the end.

i was able to stuff a tool holder in the shaft and indicate the tool holder and it appears to be running true to .0001 or .0002 imperial so for just machining i would say that's about as good as you can do. i'm happy with it so far

11 Nov 2021 14:13 #226111
got one more thing crossed off my to do list got some threads cased on my overly simple spindle shaft and since i was taking pictures i took one of the tapper while i was at it. still have a ton of work to do on this but progress is always exciting for me no matter how much or little
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15 Nov 2021 09:04 #226558
just some more pictures. almost done with the shaft but decided to order a long drill to finish the id clearance for the draw bar. i'm tired of fighting with boring bars sticking out a mile

took some length off the casting for the spindle just a starting point until i decide where the final length is going to fall. should make for a stiffer spindle so that's an added bonus.

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21 Nov 2021 11:30 #227186
managed to finish up the shaft except adding the drive dogs, i will probably do that today but things work as they should now. i had to rework the bore behind the taper since it cut small the first time but it is fixed now, i'm not sure why but my guess is i had the boring bar out to far and it was pushing away from the cut, that part of the internal work is about impossible to check with bore gauges so it needed fixed regardless.

taper lock pulley fits so everything looks good so far. i started working on a labyrinth seal for the front end but it is slow going. only thing i could find to make it form was 316 S.S. which is a pain to drill with HSS drills and boring it out on the lathe is a pain just because i can't get a good chip when cutting and have nothing but stringers always something with this little tink toy of a lathe i have
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27 Nov 2021 20:13 #227774
managed to get the drive dogs done and have my labyrinth seal finished and the mounting sorted out on the casting for the labyrinth seal. i will have to do a spring tension cap on the other end after thinking about it since i'm getting closer to that part. still have a bunch to do but  at least now i can see how it will look when i'm done,

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The following user(s) said Thank You: tommylight