Author Topic: Making short precision tapers  (Read 6548 times)

bogstandard

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Making short precision tapers
« on: February 04, 2009, 08:21:04 PM »
I just didn't know where to post this, so I suppose here will have to do.

How many of you need to make a short taper and don't know how to do it, so you start trolling the web to buy what you need.
This post shows how I go about making a short taper.

Your topslide, if it has a degree scale, can be used very easily to do this job and the only limitation is the actual stroke you can get on it. Mine can give me nearly four inches, most of the smaller lathes should allow you to do around 2" in length. Plenty long enough for a chuck taper or a stub MT that I mentioned somewhere the other day. This is purely a manual turning job, no power feeds, as you will only be using the top and crosslide.


Look what fell into my hands the other day, a very kind donation from someone who knew I was looking for a very small key chuck.
This is a 5/32" (4mm) Jacobs chuck that has a 0 JT fitting. Getting hold of one of those will be rather difficult, so I decided it is quicker and easier to make my own.




So I chucked up a piece of 1/2" bar and faced the end off.




By searching the web, I found the correct dimensions for the taper. So a quickie calculation using the triangle feature of my desktop calculator (in the downloads section), it told me that I would need a 1.41++ degree angle to be cut.
So I set the topslide over to 1.5 degrees. Always go slightly high if possible, it makes the correction of the taper much easier.




Turn the taper, continually checking the chuck for fit, if it goes too far and you get a wobbly fit, just take 1/4" off the length and start coming down to size again. Once it seems to be almost there, go to the next pic.




This is the messy bit.
Using engineers marking blue (NOT layout blue), coat the inside of the chuck taper with a very thin coat. I use a cotton bud. DO NOT put too much on, you will get a false reading. Just a very thin film.
This blue will jump out and get you, it will get everywhere if you are not careful, and SWMBO will hit you with a big stick :wack: if it appears in the house.
I have had this tin a few years, it lasts forever, and will most probably be sitting, ready for use, in my great grandson's workshop, years after I am long gone. A very good investment.




So very carefully, put the chuck on your turned taper, then push it home and give it a twist around the taper.




Gently remove the chuck and see what impression is left on the taper. This pic isn't very clear, but you can see the ring of blue left behind. Because it is at the big end of the taper, it means that the angle is too large. If it is at the small end, you will need to cut a bit off the end and increase the angle slightly. This is why I said, make the angle a bit big in the beginning.
So what I do now, is slacken my topslide bolts off just a little bit, and using a plastic handled screwdriver, gently tap a tiny bit off the angle setting. One or two very small taps is usually enough, then tighten up again and take a very fine cut, just to clean up the taper. Try the chuck on again and see what you get. Repeat as necessary.




I got this after two 'tapping' sessions, and took me about ten minutes from start to finish.




End rounded off, cleaned up a bit and parted off. Job done. Now wasn't that easy?

But in my case not finished. I will show you the next bit of my project.




While the lathe had the correct setting on the topslide, I made another, just in case.




I cleaned off all the marking blue with some meths, put a dab of loctite hi-strength on the taper and assembled the two parts.




While the loctite was setting, a bit of metal was chucked up and a 5/32" spigot was turned on the end.




The chuck was tightened onto the spigot and the tapered bit I had just made was very carefully turned down to 1/8" diameter.
This part of the job was now finished.




Popped into the collet holder of a high speed mini die grinder, it ran absolutely spot on. No detectable run out.



This is the drill part of my high speed precision drill press project. This will now be put away until I have time to make all the other bits for it.

If you notice, I left a gap at the back of the chuck and a machined on shoulder on the taper. If I ever need to remove the chuck from the mandrel, I will use a wedge between the chuck and the shoulder.

I have shown this for use with a chuck, but this method can easily be used for any taper, as long as you have an original fitting you can use the blue with, to check for correct fit.


Bogs
« Last Edit: February 05, 2009, 01:12:07 AM by bogstandard »

Offline sbwhart

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Re: Making short precision tapers
« Reply #1 on: February 05, 2009, 03:14:41 AM »
Nice one John

That chuck looks familiar  :lol:  :lol:  :lol:

Stew
A little bit of clearance never got in the road
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Location:- Crewe Cheshire

bogstandard

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Re: Making short precision tapers
« Reply #2 on: February 05, 2009, 03:50:39 AM »
Thanks Stew,

It turned out just as I had hoped. If all goes well, I will be drilling very tiny holes in the near future.

I don't normally disclose benefactors names when it comes to hard to get items, just in case you get innundated with requests.

Now about my other die grinder and the spare taper I have made.  :lol:


John
« Last Edit: February 06, 2009, 12:02:31 AM by bogstandard »

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Re: Making short precision tapers
« Reply #3 on: February 05, 2009, 03:54:13 AM »
Ah.... The birth of the precision drill.... Looking good so far John.

I like the mounting idea for eliminating the runout.... I'd have probably not thought of that.

Probably a good reason my peck drill attachment dosen't spin!!  :lol:


I'm certainly going to watch for the rest of this build  :dremel:



You getting rid of some old tooling Stew?  :scratch:    :lol:





Ralph.
I know what I know and need to know more!!!

Offline sbwhart

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Re: Making short precision tapers
« Reply #4 on: February 05, 2009, 03:58:40 AM »
Left myselve open again

 :bang: :bang: :bang: :bang:
A little bit of clearance never got in the road
 :wave:

Location:- Crewe Cheshire

bogstandard

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Re: Making short precision tapers
« Reply #5 on: February 05, 2009, 04:29:11 AM »
Ralph,

The decision to use the mini grinder as it is, is still open at this moment, that 1/8" spindle does look rather susceptible to being bent out of position, and I think it would be a pig to get straightened up again.
Also I would have liked to go a bit faster, so I just might still go for a high speed spindle and and double up the speed with a couple of pulleys. That will get me just over the 100K RPM which is ideal for the size of drills I am using.

Stew,

Now you see why.

John

Offline SPiN Racing

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Re: Making short precision tapers
« Reply #6 on: February 05, 2009, 10:02:51 PM »
WOW very very cool....

Turning it to 1/8 while the  chuck is mounted.. very wise. AKA no runout..

<adds that to notes>
SPiN Racing

Kludge

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Re: Making short precision tapers
« Reply #7 on: February 05, 2009, 11:11:55 PM »
This is ubercool, John, especially since I have two JT0 chucks plus the Clisby has a small MT0 taper for which adapters seem scarce.  (I don't know about the headstock yet.)  At the moment, the only thing I have that accepts a JT0 taper fits my 8mm lathe which means I have a lot of work to do. 

Thank you!

Best regards,

Kludge

bogstandard

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Re: Making short precision tapers
« Reply #8 on: February 05, 2009, 11:40:57 PM »
Kludge,

No, THANK YOU.

Your reply has made the effort worthwhile.

If it has given thought to, or helped just one person, the time spent has not been wasted.

                                         :proj:

It is amazing how small recollections from the past, can be turned into useful little articles that can maybe help others.


John

BTW on the original article, you may have noticed that for turning the final 1/8" spindle, I had changed over to a tipped tool.

The reason being, I had to get the lathe up to its top speed to try to prevent the unsupported fine spindle from deflecting while I took superfine cuts. I was worried that the uncooled HSS cutter might overheat. If I had used coolant, I wouldn't have been able to see how the cut was progressing, plus, at that speed I would have got rather wet.
« Last Edit: February 05, 2009, 11:49:24 PM by bogstandard »

Kludge

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Re: Making short precision tapers
« Reply #9 on: February 05, 2009, 11:54:34 PM »
John, I have completely failed to not learn from you. 

Just thought I'd mention it.

Best regards,

Kludge

Offline Darren

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Re: Making short precision tapers
« Reply #10 on: February 06, 2009, 05:17:54 AM »
Hi John I have a couple of small chucks that I salvaged from old drills. I turned threaded shanks for them but they ended up off center.

Now I know what I need to do, thanks to your post, turn the shanks whilst in the chuck actually holding a small rod which is held in the lathe.

I also have a JT0 chuck that needs using....

So, some projects for later then..... :D
You will find it a distinct help… if you know and look as if you know what you are doing. (IRS training manual)

bogstandard

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Re: Making short precision tapers
« Reply #11 on: February 06, 2009, 06:38:30 AM »
Darren,

The only true way to get it perfectly concentric is to do what I did, mount a bar in the chuck first, turn perfectly concentric, then without removing it from the chuck, put on drill chuck and turn the back spindle. By doing that any error in both chucks is cancelled out.

John

Offline SPiN Racing

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Re: Making short precision tapers
« Reply #12 on: February 06, 2009, 05:45:23 PM »
ooooh and run the lathe fast as heck when turning small diameter....

same with drilling small diameter then I guess.
SPiN Racing