Internal taper question

Aukai

Aukai

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I was asked to do a project to cut a 5" diameter aluminum bar into 2" sections, and bore a hole in the center. I said sure bring it over. Well I have the bar and the fitting that they want it bored out for, what they did not tell me is that it is tapered, and slotted. I would like to get some guidance for this project please.
Major diameter is 1.940,
the minor diameter is 1.874
The taper calculator I looked up says I have a 1.909 taper angle, and a .06667 taper per inch. The fitting is 1.5" to the shoulder, I'm wondering about what kind of fit do I bore this out to. Also is the math correct, I'm debating about using the compound/cross slide vs the taper attachment. I have it bored out to the minor diameter right now.
 
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Assuming a taper length of 2", the major - minor diameter is 1.940" - 1.874" = .066". Half that is .033. That divided by 2" is .0165 which is the taper in in/in. This is also the sine of the half angle and the arcsin .0165 = .945º. If the taper length is 1.5", then the taper would be .022 "/" and the half angle would be 1.261º.
EDIT: Actually, it would be the tangent, not the sine. but the angle would still be .9453º for the 2" length and 1.2603º for the 15" length.

In SolidWorks, here is the solution.
Taper Angle.JPG
 
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I'd be inclined to use the compound, assuming enough travel. Easier to set up for a taper this short. I would be looking up the specs for that taper lock rather than relying on the measurements. Oh, and then there's the keyway. Always fun on a taper.

The machinist's curse, it's never a simple as the customer thinks. "All you gotta do is...."
 
mmcmdl said:
LOL , just give it to one of my guys . They couldn't broach a straight keyway if their life depended on it . :grin:
Click to expand...
You just gave me a flashback.
One of the guys walks into the office with a part in hand. Keyway is proper depth on top, nearly twice that on the bottom.
Him: "I don't know what happened"
Me: "Well I do. How long have you been doing this?"

For those who have just tuned in, always orient the part in the press so you can see the profile of the teeth. You will be able to see WHEN the broach starts to dig in.
 
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MrWhoopee said:
For those who have just tuned in, always orient the part in the press so you can see the profile of the teeth. You will be able to see WHEN the broach starts to dig in.
Click to expand...

I have broached a grand total of one keyway. I had no idea, and probably got lucky it's pretty straight. Now I know why and how to prevent it, thanks! :)

In my defense, I would never claim to be a professional machinist that deserves to be paid to turn good parts into scrap. I do that for free! :)
 
Thank you.
Would the math change if the major, and minor were calculated on a 1.5" vs the 2"? My dad designed torpedoes, and mines when he was in the Navy, and had a math degree, I was standing behind the door when they were passing out the smarts gene. :oops:
 
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