# Myford nose thread ER32 chuck



## Blogwitch (Feb 8, 2015)

This won't be a warts and all post like usual, just a quick skim thru showing some items that haven't been seen before.

First  off, I got a lump of the tough hydraulic ram material. If I knew the  problems that this was going to cause later, I would have used another  material.
I measured up the hole at the bottom of the ER32 holder, and that size was bored thru this piece.







I took the internal diameter measurement of a commercially made Myford part.






And the depth as well






These were the sizes bored into the back of the piece part.






I  also bored a runout on the far side of where the threads are to go, to  allow the threading cutter to have a safe run into area.






The  toolpost was offset half the thread angle (55 degs), in this case 27.5  degrees, the opposite way to a normal external offset thread cut.
By  doing it this way, when you put your cut on with the topslide (coming  towards you) the tool is cutting on it's forwards face, just like you  would do using this method for external cutting.
Everyone uses the  method they feel the most happy with, some cut from the inside coming  out with the tool upside down, others use just straight plunge cutting,  this is the way I do it, and it works for me.






Then the tool was set to perfect height, and squared up to the job.






The saddle stop was set up, but it would slide if needed, at the max cut length.






The  tool was marked up with the width of the runout, from the end of the  thread to the back of the runout. If I stopped the cut as soon as the  mark started entering the hole, the tool would never reach the back,  even though the tool is actually moving forwards as you set each cut.






This was where I hit major problems with the material.
I  thought I would finish off the last couple of thou depth of cut with  the cheapo taps I had bought. These taps would be great for free cutting  mild steel, but not the stuff I was using here.
I managed to finish off the threads with them, but it was very hard work.






This  is a piccy of the threads. They look absolutely awful, but in real life  they are perfect. I think it is a combination of oil and flash  photgraphy that made them look so bad.






The part fitted perfectly onto my Myford nose adaptor, and it was turned up ready to have the external metric threads cut.






The  threads are 1.5mm pitch, and this is the first metric thread I have cut  on this machine since I purchased it over a year ago. Everything went  very smoothly.






I had purchased a ball raced nose nut specifically for this job, and it screwed on and fitted perfectly






Now we get to the tricky bit, cutting the taper for the collets to fit into.
The  standard taper for an ER collet is 16 degrees inclusive, so that means  the topslide (compound) needs to be set over by 8 degrees.
This was  duly done, but you have to remember that the taper is critical for  correct operation, and this is only a very rough setting. A little  later, things are tweaked to get the taper exact.






This shot shows what the setup looks like.
The  topslide is set over, a boring bar is in the toolpost, set as though it  would be boring a normal hole, and the saddle locked up.
All cutting  is done using the topslide feed handle, so you need to get your  technique sorted, whereby you use both hands in a swapover motion so  that you get a steady and constant feed with no 'jerkiness' between  changeover. This ensures you have a nice smooth surface for the collets  to slide on.






I  cut about 2/3rds of the required meat removal and then blued up the  internal surface with Engineers blue, NOT layout blue. Engineers blue  doesn't set and go dry, and so can transfer itself onto anything it  comes into contact with. I usually have to give the whole area a good  clean down afterwards, as the stuff seems to jump from here to there all  by itself.






Taking  the smallest and largest collets from the set (to allow for the  different springiness) the collets were gently pushed into the blued up  hole and even more gently, rotated. You want to make sure that your  actions don't compress the collet at all, otherwise you may get a false  reading. That was the reason for using the two collets, just to make  sure I wasn't pressing in too hard and I was getting a consistent  result.
The two lines at the tops of the collets are the top one is  how far it goes into a normal collet chuck, and the bottom, how far they  penetrated into the taper I had cut.
As you can see, the blue has  only transferred onto the bottom part of the collet tapered face. This  shows me that the angle that I am cutting is too large.
I slackened  off the topslide bolts very gently, and tapped the topslide with the  plastic end of a small screwdriver to reduce the angle by a minute  amount.
Things were tightened up again, and a skimming cut done so  that the old taper was only just cleaned up. You don't have a lot to  play with, so while you are fine tuning, you take off the minimum  material to do the job. I found the sweet spot first time, you might  take a couple of 'taps' to get it spot on.
The new taper was blued up and rechecked again with cleaned down collets.






This  is the result of my 'adjustment'. I have blue showing from top to  bottom of the taper. The uneveness is caused by the rough finish on the  taper, but as long as it is as shown, then the finish will be tidied up  at the final stage. I have my taper now spot on.






The  next stage is to get the taper to the correct diameter. So after the  collets were cleaned up with spirits, they were place in my normal chuck  and the depth marking was put on. This shows how much deeper it still  needs to go. It looks a lot, but when dealing with tapers like this,  even a tiny skim is a lot.
When I got to the final skim, I really slowed down the hand feed, and speeded up the chuck.






I  was considering breaking out the toolpost grinder for a final lick  over, but the results I got by hand feeding will be just fine.






The collet now sat at the correct depth.






So now the moment of truth.
I  grabbed a 16mm collet and a new tungsten cutter, and by mounting the  cutter in the wrong way around, I had a reasonably accurate test bar.

A quick check with a high precision DTI showed I had a TIR of 0.0001".

A fly farting as it went past could have caused that, so that'll do me.






So  onto the mill, and using the newly made RT adapter and a woodruff  cutter, I made some slots for the C spanner to fit into, just so I can  get the thing off wherever it is mounted onto. I actually had to chisel  it off the lathe fitting, but the first cut with the woodruff took the  gouge mark out.






I  can now interchange either 3 and 4 jaw self centring chucks, an ER32  collet chuck or a small faceplate between my lathe and the RT on my  mill.






The next bit soon


John


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