Matching a taper

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AllenH59
Posts: 387
Joined: Wed Mar 16, 2011 1:26 pm
Location: Prince George BC Canada

Matching a taper

Post by AllenH59 » Sat May 06, 2017 1:21 am

Gentlemen, hi, I have been out of the shop for the winter, and just got back in.. A friend brought me a bronze cast hub for a steering wheel for a boat, which was a about 70 years old, and had been his father's. He asked if I could bore the hub a bit, and make it fit a tapered shaft he brought. He is a good friend, and takes me deep sea fishing, so I said I would give it a go. I measured the shaft as best I could, and set my compound as close as I could. I made a few fine cuts, and tried the shaft, and found it wobbled a bit, being tight at the inside of the cut, so I adjusted the compound a bit and took another cut, at it was tight at the outside end. I split the difference twice more, and got it dead on. I have previously been unsuccessful at matching tapers. I did set a dial indicator up so I could see how much I was adjusting it. It turned out that the error was very small in the first place, although it felt like quite a bit. Can you guys set your lathe to cut a taper accurately enough that you do not need to fool with it as I did to get it right?
Thanks
Allen

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10KPete
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Location: Nordland, WA, USA

Re: Matching a taper

Post by 10KPete » Sat May 06, 2017 1:56 am

Well, in the case you describe I would chuck the shaft, dial it in true. Then with an indicator mounted to the tool post, adjust the compound to be true with the taper. Swap the shaft for the hub and bore it.

That's what I do.

Pete
Just tryin'

Harold_V
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Location: Onalaska, WA USA

Re: Matching a taper

Post by Harold_V » Sat May 06, 2017 2:01 am

AllenH59 wrote: Can you guys set your lathe to cut a taper accurately enough that you do not need to fool with it as I did to get it right?
Thanks
Allen
No. And to think you can is a good sign you'll settle for less than acceptable. That's true, assuming you wish to make a simple setup and be correct. There's always the case where a guy gets lucky and hits the right place, but that isn't likely to be reliable.

You made a good choice turning to an indicator to make corrections. That's the procedure used when setting (removing) taper on a cylindrical grinder. While the machine markings are reasonably correct, they are intended for use as a guide, not for precise settings. To give you an example of why that is, one degree of angle provides for .017" taper (per side when discussing round objects), so it's obvious that if the marks are off, even slightly, it's not reasonable to assume they can be used reliably. You see evidence of that whey you dial in the head of a mill, where the fine corrections required to bring it in are not really visible on the machine markings.

In regards to using an indicator to dial an angle true, unless your tool is dead on center, and the indicator is, likewise, dead on center, you'd still find a small amount of error. It will get you close, but nothing duplicates making the setup, making a cut, then checking the angle, either by fitting, or by precision measurements on a surface plate, with the part held between centers. Angles are never easy, assuming you wish to be precise.

Harold
Wise people talk because they have something to say. Fools talk because they have to say something.

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Lew Hartswick
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Location: Albuquerque NM

Re: Matching a taper

Post by Lew Hartswick » Sat May 06, 2017 8:47 am

Yes I can BUT the compound on the lathes I have access to are very suitable to do this on. First off they have nearly 5 inches of travel and a straight side that a dial indicator can follow. So I made a fixture that sits on the ways and measures how far the side of the compound moves while moving the carriage 4.5 inches. That give a pretty darn good angle calculation. If anyone wants a pix I'll have to do one Monday .
...lew...

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Frank Ford
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Re: Matching a taper

Post by Frank Ford » Sat May 06, 2017 1:17 pm

I made myself a special indicator holder to avoid having to even think about setting the indicator on dead center for matching tapers - works every time without any hassle.

Here's an article on the project:

http://www.frets.com/HomeShopTech/Tooli ... older.html

Once the compound is set, I can cut closely matching inside or outside tapers with ease if I set the tool on center with my height gauge:

http://www.frets.com/HomeShopTech/Tooli ... htset.html

I still check, tweak, etc., as necessary, of course. . .
Cheers,

Frank Ford

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warmstrong1955
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Location: Northern Nevada

Re: Matching a taper

Post by warmstrong1955 » Sat May 06, 2017 2:56 pm

Ty as I might, I have never got a taper exactly right with the first set up with a dial indicator.
I run a test piece, measure, and it always requires a tweak or two to get it right.

First few time, it was more than a few tweaks. :roll:

Bill
Today's solutions are tomorrow's problems.

Harold_V
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Location: Onalaska, WA USA

Re: Matching a taper

Post by Harold_V » Sat May 06, 2017 3:42 pm

Frank Ford wrote:I still check, tweak, etc., as necessary, of course. . .
Yep. That's the point.

Harold
Wise people talk because they have something to say. Fools talk because they have to say something.

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warmstrong1955
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Location: Northern Nevada

Re: Matching a taper

Post by warmstrong1955 » Sat May 06, 2017 4:26 pm

Harold_V wrote:
Frank Ford wrote:I still check, tweak, etc., as necessary, of course. . .
Yep. That's the point.

Harold
I feel better..... :)

Bill
Today's solutions are tomorrow's problems.

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larry_g
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Location: Oregon

Re: Matching a taper

Post by larry_g » Sat May 06, 2017 7:42 pm

If possible to have taken a skim cut on the shaft you could have done that and then without changing the angle of the compound turned the taper in the hub ??

lg
no neat sig line
I am unique, just like everyone else.

CaptonZap
Posts: 68
Joined: Fri Mar 06, 2015 8:31 pm

Re: Matching a taper

Post by CaptonZap » Sat May 06, 2017 7:53 pm

Only if you make an upside down boring bar to cut on the back side of the female socket. :wink:

CZ

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wlw-19958
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Location: Lewes, DE

Re: Matching a taper

Post by wlw-19958 » Sat May 06, 2017 8:01 pm

Hi There,
CaptonZap wrote:Only if you make an upside down boring bar to cut on the back side of the female socket. :wink:

CZ
Or, reverse the rotation of the spindle and cut on the back side.

Good Luck!
-Blue Chips-
Webb

Magicniner
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Joined: Thu May 30, 2013 4:40 am

Re: Matching a taper

Post by Magicniner » Sat May 06, 2017 9:20 pm

That's a yes the ;-)
But I'm not a fan of changing things from standard, if at all possible I like to ensure manufacturer's parts will fit after my repair.

- Nick

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