Author Topic: Myford to ER32 collet  (Read 14425 times)

bogstandard

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Myford to ER32 collet
« on: November 21, 2009, 05:18:54 PM »
This is the last part of my interchangeable tooling that needs to be done. After this, I will have the complete versatility to swap over between my lathe and RT on the mill.

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.

This has been shown on here before by Arnold, but he tended not to show how a few things were done.

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.




I will see if I can finish this off tomorrow, but don't hold your breath.


Bogs
« Last Edit: November 21, 2009, 05:20:36 PM by bogstandard »

Offline DICKEYBIRD

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Re: Myford to ER32 collet
« Reply #1 on: November 21, 2009, 06:40:42 PM »
Great stuff John!  I hope to make an ER collet adaptor for my Taiwanese EMCO 8 clone one of these days.  It has a 3 stud flanged spindle which will require either making a ton of swarf or a 2 part weldment.

Is that a brazed carbide threading tool you're using?  Nice piece, that.
Milton in Tennesee

"Accuracy is the sum total of your compensating mistakes."

bogstandard

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Re: Myford to ER32 collet
« Reply #2 on: November 22, 2009, 01:05:34 AM »
Yep, an el cheapo middle European job made by Soba. I bought it in especially for this job because I knew I would have trouble with the material, as it was the cutter was great, just the taps struggled a bit. I should have used the threading tool all the way to finished, but I wanted to see how close and tidy the thread form was with the taps.

http://www.chronos.ltd.uk/acatalog/TWINW_PACKS_OF_BRAZED_TCT_THREADING_TOOLS.html

About 10 bucks for a pair in your money.

You have to be very careful with them as if you use one a little too large for the job, they can easily foul the threads. I had to grind relieve the support bar on this one before it was put to use. Normally I would make my own out of HSS or silver steel.
I actually dropped this one (a very common occurance with my fumbly right hand fingers) as I was putting it away and the tip came off. But for the cost of them, they are not worth repairing.


John

Offline DICKEYBIRD

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Re: Myford to ER32 collet
« Reply #3 on: November 22, 2009, 09:07:42 AM »
Thanks for the link John, I put those on my procurement list!
Milton in Tennesee

"Accuracy is the sum total of your compensating mistakes."

Offline andyf

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Re: Myford to ER32 collet
« Reply #4 on: November 22, 2009, 10:00:55 AM »
I have a confession to make  :bow:

I bought an ER25 Myford nose adaptor from Chronos - about 1/3 way down this page http://www.chronos.ltd.uk/acatalog/Myford_Lathe_Compatible_Acessories.html , to use my ER25 collets on my Dore Westbury mill/drill. To make one, I would probably have had to make a dummy spindle nose first, and laziness set in  :coffee:

Chronos only seem to do them for ER25s, though, and not for ER32s, probably because a major advantage (particularly on a lathe) of the device is that stock or tools can pass through into the spindle bore, which on most Myfords is only about 15mm. 
Sale, Cheshire
I've cut the end off it twice, but it's still too short

bogstandard

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Re: Myford to ER32 collet
« Reply #5 on: November 22, 2009, 11:19:23 AM »
Andy,

I was going to do exactly the same thing as yourself, as they can be bought almost the same as I am making.

Half way down the page on here

http://rdgtools.co.uk/acatalog/MYFORD_LATHE_USERS_NEW1.html

Unfortunately, some don't come up to expectations and are a little on the suspect side for accuracy.

In fact it was only a couple of days ago I helped someone over on HMEM with the same sort of problem.

http://www.homemodelenginemachinist.com/index.php?topic=6796

I didn't want to go down the 'fixit' route.


Bogs

Offline andyf

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Re: Myford to ER32 collet
« Reply #6 on: November 22, 2009, 01:04:59 PM »
Mine seems accurate enough - just luck, by the sound of it. Like your threading tool, it's made by Shobha/Soba - I think they are the same outfit, and a bit further away than middle Europe, unless Delhi has got closer since we did geography at school :lol:

http://www.shobha-india.com/about-us.html

But localities just won't sit still nowadays. I'm fiddling around with a new (to me) DC motor for the Dore Westbury. The rating plate says it comes from Leeson Electric Corp, in Wisconsin. At the bottom, in tiny print, it says "Made in China."

Andy
Sale, Cheshire
I've cut the end off it twice, but it's still too short

bogstandard

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Re: Myford to ER32 collet
« Reply #7 on: November 22, 2009, 05:34:22 PM »
I stand corrected Andy.  :bow: :bow:

I was just repeating what a retailer told me at a trade fair when I asked where a Soba vice I had bought came from.  :bang: :doh:


John

Offline andyf

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Re: Myford to ER32 collet
« Reply #8 on: November 22, 2009, 06:37:36 PM »
Now veering definitely :offtopic:

It wasn't said in a pedantic spirit, John - I was merely musing on how you can't rely on what labels say (or what suppliers tell you) any more. I see from The Times that one supermarket chain is selling ready meals "produced in Britain" though the chicken they contain is brought in from the Far East. The sophistry offends me; the economics of the production chain simply baffle me.

Andy
Sale, Cheshire
I've cut the end off it twice, but it's still too short

bogstandard

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Re: Myford to ER32 collet
« Reply #9 on: November 22, 2009, 07:22:59 PM »
Andy, little would you believe it, I prefer someone to correct me when I am wrong. I don't profess to know everything, but what I do know should be correct, as I do pass over a lot of information. If that incorrect info can be corrected, then I am very grateful.
So please, don't be afraid to tell me I am wrong (just don't go out alone in the dark, the Boggy man will getcha).  :lol: :lol:


Anyway, we are now at the last part of this project.
Again, it is a highly abridged version, because most things have been shown before, but if there is anything you don't really understand, then shout up and I will try to explain the process

I left the last post awaiting threads to be cut.
They have now been completed using the offset single point technique.
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.




That completes the set of parts to make my dream of interchangeable tooling come true.

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.




A super happy Bogs.

Offline dsquire

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Re: Myford to ER32 collet
« Reply #10 on: November 22, 2009, 10:13:02 PM »
John

Thanks for having us all along for the watch. I know that I learned a bunch and I am sure others did as well. This should give you a new level of satisfaction when you are machining and moving between operations and machines. Very well done John.  :ddb: :ddb: :ddb:

Cheers  :beer:

Don
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Offline Bernd

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Re: Myford to ER32 collet
« Reply #11 on: November 23, 2009, 08:53:17 AM »
Nice job as always Bog's  :thumbup:

Bernd
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Offline DICKEYBIRD

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Re: Myford to ER32 collet
« Reply #12 on: November 23, 2009, 10:51:56 AM »
Thanks again John for your excellent tutorial.  I am gathering the necessary "stuff" (mostly gumption needed) to make one of those.

As mentioned above, I was thinking about welding 2 pieces together to fit my flanged spindle but EUREKA!  Look what I found in my junk box today.  I'd forgotten all about it.  It's a connector shaft off of one of those steerable Vermeer (or Burkeen) horizontal drilling machines.  I saw it lying beside the hiway a few years ago and stopped to pick it up.  I have cut several chunks off it to make various bits of tooling and it machines well.  The flange OD on my lathe is a bit less than the inner edge of the bolt holes so it should do great!

Dear Santa, will you bottle up some Bogs Gumption™ and leave it under the tree for me?;)
Milton in Tennesee

"Accuracy is the sum total of your compensating mistakes."