Setting compound for 30 minute angle?

I'm trying to turn a front sight base that will fit a tapered barrel.
After some hand-to-calculator fighting, I came out with a 1/2 degree per
side angle. Start of the band is @.610, the end is @.630, looking at
tapered end mills in Wholesale tool, Grainger, KBC, Enco, and others
shows a decent range of prices, but the corker seems to be the front
diameter. Stock tapered end mill tips are in common sizes, like 3/8,
1/2, 5/8 and 3/4.
Thing is, moving the band rearward gets the band into the diameter of
.623, but the band will be over an inch and a half from the muzzle.
Looking at the iGaging digital protractor, the accuracy is listed as .2
degrees. Resolution is listed as .05 degrees, but look at the accuracy
and we're well into half the value of the desired angle.
How can I set my compound for boring? Angle plates? Adjustable angle?
Reply to
Louis Ohland
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I think you should be looking for a tapered reamer.
Reply to
Pete C.
Uh, yeah. Tapered end mills seem to be the only game in town, however. The tapered reamers that I've seen are rated in inch/foot tapers. Looking at Machinery's Handbook, the tapers are way too large.
Perchance a vernier protractor, dunno.
Reply to
Louis Ohland
What I've done before is chuck up a piece of drill rod, indicate it true, then mark off an inch or few inches and indicate the compound to taper the desired thousandths per the distance I marked off. For example if I want a taper of 0.008" per inch, I mark 1" on the drill rod and set the compound with an indicator to move the desired amount per inch.
After getting close, you can use high spot blue to see if the taper fits evenly or not, and work for a more perfect fit.
RogerN
Reply to
RogerN
Chuck the barrel up muzzle to the headstock - better yet use centers . Mount an indicator to the compound and adjust until the indicator stays steady when you crank it in and out .
Reply to
Snag
Almost there, but the barrel is in the action. Ooh, here's the thought... cylindrical action, not perfect, but chuck it up, run the muzzle very carefully onto a tailstock live center. Use indicator as described. Snap, that's backwards. Unless I indicate the far side of the barrel...
Reply to
Louis Ohland
The compound isn't intended for cutting accurate shallow tapers, that is why taper attachments for lathes exist. You will likely have to go by trial and error, test cutting some scrap and test fitting until you find the correct setting.
Reply to
Pete C.
My first preference was a tapered mill or reamer, because this only changes about .010 over the inch I need.
Reply to
Louis Ohland
Machine a plug that is a very light press fit in the action ?
Reply to
Snag
Maybe you could you attach a sine bar set to 0.5 degrees to the faceplate and use a square to transfer the angle to a bar clamped into the compound dovetail.
I tried to cut a taper for a grinding wheel spindle adapter with the compound and found that I needed to refit the dovetails so the gibs were evenly tight throughout the full travel.
jsw
Reply to
Jim Wilkins
Make a D-bit reamer, it's easy enough.
Stan
Reply to
stans4
Yeah, just set the compound to 0.5 degree and turn one from drill rod. They'll cut a little while without being hardened.
jsw
Reply to
Jim Wilkins
Oddly, that came to me while drinking coffee. Except the D-bit part.
Is this like a spade bit with a removable blade? Excuse the bad analogy, still looking.
Reply to
Louis Ohland
Jim Wilkins fired this volley in news:193fe058-9df9- snipped-for-privacy@s28g2000prb.googlegroups.com:
Umm... Jim?
this was a joke, right?
LLoyd
Reply to
Lloyd E. Sponenburgh
Or, just attach thge sine bar to thge faceplate and an indicator to the compond. Adjust the compond angle until you can run it in and out along the faceplate without moving the needle.
Reply to
rangerssuck
Surely you mean set the tailstock over?
Reply to
Tim Wescott
Setting the tailstock over the few thous has the advantage of simplicity. Run between centers. I assume moving the tailstock toward me will reduce the tailstock end. Set for zero off the tailstock end, then move the tailstock to me by .005 (roughly).
Get 6" of A-2 (cheap), face and center drill both ends, set up with dead center/dog at headstock, live center at tailstock. Indicate so its roughly parallel (what's a few thou between friends?), turn about 1/2 inch at tailstock to 9/16 (@.5625 dia) so it will pass through the small end of the reamed section, then set the tailstock to me roughly .007 or so, turn the taper over 1.000", then measure.
Still ditzing with the base size, initial impression is an .875 OD x .500 ID by 1.000 inch long chunk of aluminum tubing. Drill out to 15mm (just over .610). Then things get fuzzy. Check chuck concentricity. Set tailstock back to dead on. Chuck up base, ream with D bit.
Tubing wall thickness is important. Lyman 93 center of aperture is .550 above bottom of clamp. I can get mounting blocks in various heights, up to .500 high. Sight has to be @1.1" above bore, so .550 (sight) + .375 (base)+ .310 (to bore center) + .125 (7/8 OD thickness) is 1.081. I think that is close enough.
Snap, no stock downstairs with a diameter that will work in steel that will hold up. 16mm will be .639+. Use D bit like a tap, base in chuck, spring loaded center in tailstock, D bit in tap chuck, ream to depth.
Reply to
Louis Ohland
Yep, dialing in the compound with an actual gage indicator running along a known cylinder is the best way. It's a little slow, though, so if the angle is going to be reproduced later, it pays to cut a reference (cone, in this case) and adjust for zero gage indication on the reference instead of variable indication against the cylinder.
There are other techniques possible; an amusing one is to zero the compound angle, then mount a laser pointer. The laser spot on a distant wall (2 meters) will indicate d*tan(theta), or (assuming perpendicular incidence at theta =3D 0) (2000 mm) sin(1/2 degree) =3D 17.45 mm when the compound is adjusted to the correct angle.
Reply to
whit3rd
Some of the tapers I used to turn on the lathe compound were .0025" taper in ~3" for facing 33rpm record dies IIRC. First I'd cut the face with the slight taper, then grind with the tool post grinder feeding 0.0002" at a time. The compound can work for cutting shallow accurate tapers if set up properly.
RogerN
Reply to
RogerN
Hmm, rechecked my math, looks like the .750 OD is what I want for the base, wall thickness @.0625, sight block of 3/16 (.1875), sight .550, barrel CL to surface .312, add em up and it's 1.112, minus the concave sight base (.005 or so).
Tool post grinder. Erk. Lessee, start looking through the usual suspects...
Reply to
Louis Ohland

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