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parker
10-19-2001, 07:22 PM
want to cut a inside taper on a turning collar. shaft tapers,.658---.653X1". do not know how to convert this to the compound. math not my good point. any simple methods known of? thank you---parker

Thrud
10-19-2001, 10:31 PM
parker,

Tan A = a/b, A is the taper angle, b=1, a=(.658 - .653)/2 = .oo25"
Tan A=(.oo25"/1.ooo)
ATan (.oo25)= 0.14324* or 8.5 Arc minutes

This will be a really tough angle to set on the compound. It would be best to set the male part up in the lathe and clock the compound in against the taper to zero deflection as you advance and retract your compound. Then chuck the part you want to bore the taper in and make a fine cut along the taper with the compound set to the angle required. Your initial hole size should be less than the .653 dimension. Check fit with the male part after each cut. After shutting off the lathe, of course!

Take your time, be patient.

Good Luck

Dave

toff
10-19-2001, 11:37 PM
Hi,
Math not my good point either. I normally will use a plunger type dial indicater in a holder from the bed with the plunger tip against the side of the side of the angled compound to measure the fall/difference when I move the saddle a given distance along the bed equal to the length of the taper. The fall equal to one half of the total difference in diameter over the depth of cut. I milled a flat parallel to the solid dovetail side of the compound on my Atlas/Craftsman for set-up purposes. Many lathes have a flat/boxy shaped compound so you don't need to do this to them. This is a wAy to do things that I was taught. There are many others!
If you were to put a dial indicator in the tool holder and a bar in the chuck, swivel the compound to a RCH under 1* and put the indicator against the bar in the chuck. advance the compound to the depth of cut and read the indicator, Adjust the compound angle until the indicator reads 1/2 the difference in dia. at the depth of cut. This will work up to about 4 degrees but over this you have to do the math for the base of the triangle.
Always start all cuts from the same compound dial reading! Then use the cross slide for feed.
By the way, on a good day I would have chips by the time you read this.
There are other methods using sine bars and so forth, but this worked for me again yesterday with three tapered parts that were +.001 minus.000 and .0005 difference from one another. This on a Enco 14x30 that is 6 years old. The material was powdermetal tool steel at 45Rc.
Draw diagrams on paper and move your hands to help understand, words don't do the method justice.
Luck
toff

A book no less!? if you knew how many times I've tried to explain this.. I'll leave it to Lautard!!
New thought, instead of indicator holder from bed, Indicator holder from work or chuck!

[This message has been edited by toff (edited 10-20-2001).]

JIM DEWOLF
10-20-2001, 02:40 PM
Right on Toff! That's the way I do it but could not figure out how the hell to explain it. You should write a book.
Jim

Gizmo
10-20-2001, 11:11 PM
Yeah, what they said! If possible, I would make the part about twice as long as the finished. A very gentle taper like that is hard to hit exactly, so going a thousandth over might advance you a half inch down the stock. Then if you want to polish it up, you find it advances another 1/4"! I'd leave it long, fart with it 'til the taper was what I wanted, polish it up, and face it down to the good inch.