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Myford to ER32 collet

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bogstandard: 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

DICKEYBIRD: 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.

bogstandard: 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

DICKEYBIRD: Thanks for the link John, I put those on my procurement list!

andyf: 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.

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