Turning a taper spindle plug collet own its own lathe
|John McNamara||13/11/2011 05:07:25|
1311 forum posts
Turning a taper spindle collet on its own lathe.
This may have been posted before although I have not seen a post recently.
I needed to make a MT3 and NT40 plug collet to fit directly in the spindle of the lathe.
So a piece of stock was selected that was long enough to make the two with a 15mm extra allowance in case the taper did not fit first time and to allow for cutting them apart and facing The plug is about 65mm diameter at the widest point.
The following cutting sequence was used.
After measuring the taper with a protractor I set the top slide to match the taper. Then I mounted the three jaw chuck and I skimmed the diameter to remove the scale then bored a Half inch hole half way through from the tailstock then reversed the work piece and bored from the other end and creating a through hole, as it happens it was fairly true leaving a clearance hole for a 12mm all thread rod that would be used later to clamp the collet. next both ends of the piece were faced. Then after rechecking the material holding tight I made the first taper cut.
Leaving the piece in the chuck I removed the chuck and tried the taper cut using a little marking blue. It was a little out so I nudged the top slide and reinstalled the chuck made another cut and tried again. This time it was (about) right. "That L Do" ! (something I do not often say)..... I removed the piece from the chuck and removed the chuck.
Continued next post.....
Edited By John McNamara on 13/11/2011 05:12:02
|John McNamara||13/11/2011 05:26:40|
1311 forum posts
Continued from previous post........
From that point on I would hold the piece in position with the threaded rod only.
I installed the piece in the spindle clamped it with the all thread drawbar and turned the other straight end. It was then a simple matter of adjusting the taper with the top slide angle until a perfect fit was obtained I used marking blue to check the fit. No more trying to juggle a heavy 8 inch chuck, Using the taper alone guarantees perfect concentricity. It also saves a lot of time to make two at once. To assist removing the collet I put a nut behind it to enable it to be driven out using the all thread rod as a driver
once completed the piece was cut in half using the bandsaw and the pieces refaced and bored MT3 and INT40 as required. The fit was more than enough to hold the piece in position for facing and boring. I just tapped it in position with a plastic mallet to seat it. For extra precision I marked the collet to index a known point (a small screw) on the spindle.
Chuck no longer required
Ready to cut in two
Cut on the bandsaw (A fiddly set up it was hard to grip)
Ready to face and bore as required
Edited By John McNamara on 13/11/2011 05:41:03
|Richard Parsons||13/11/2011 08:57:50|
645 forum posts
John next time set your compound slide using a DTI. If you are going to a male taper use the rear of the taper in the Headstock. This will give you a good taper.
If you have a taper which is a bit ‘wobbly’ then machine away the centre of the taper. You will get a good fit.
|John McNamara||13/11/2011 10:14:45|
1311 forum posts
A good fit but not a perfect fit. There is the chance of a slight error due to the cut line being slightly different from the line measured on the taper by the indicator. Unless the match is perfect two different tapers will result, Marking blue and trial cuts will yield a very close to perfect result.
It was easy to turn the work end for end and make tiny adjustments to the top slide. without having to manage a heavy chuck hanging on the end of the work. this is an industrial lathe, the chuck is 200mm diameter and weighs about 25 kg on its DIN back plate. It is almost impossible to "feel" that wobble with a heavy weight (Chuck) hanging on the end of it.
Making a pair makes the job easy, in this case I wanted two anyway.
The process would work for many different types of collets even very small ones. The advantage being that you are "fitting" them to their holder, then boring them in position. You do not have to stop at 2 you could cycle a dozen work pieces or more if needed. all perfectly fitted and bored in situ.
Edited By John McNamara on 13/11/2011 10:20:20
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