Dummy D1-4 Nose Spindle ER25 Collet Chuck Pt. 1

[plunger]

Hi My name is Eugene and I need to make a backplate. I dont understand the term zero to cut this taper to get it right. I was hoping someone could please explain it.
Thanks Eugene

[Highpower]

Hi Eugene,

First of all, welcome to the forum.  

What Dave referred to as "zeroing" the taper means adjusting the angle of your lathe's compound slide until it matches the angle of your spindle nose EXACTLY.  You can do this by holding a DTI or dial indicator in your tool post. Place the tip of the indicator on the nose taper and move the lathe compound slide (not the carriage) back and forth to run the indicator across the taper. Adjust the angle of the compound slide until the needle of the indicator no longer moves when you run across the taper. In other words 'zero' movement of the gage means you have adjusted your lathe compound to the exact angle needed to cut that same angle on another part. I hope that makes sense?

[plunger]

Thanks for the reply Willie. Without making a dummy I wonder how feasible it is to machine a backplate to fit perfectly. I would think it would be real hard.
If one cut the taper od slightly larger and then face the flat section untill the taper and the flat section blues up.In other words to creep up on the measurement.
Also I would hate to damage the register on the spindle of my emco v13.
I was going to try this from en19 (4140I think) but maybe cast iron would be a better choice simply because its softer.
Does anyone know of any other write ups on how to do this.? I would need as much help as possible.I am a bit mathamatically challenged and the trig to machine a 7 degree and 7 sec and whatever arcs is beyond me.
Thanks Eugene

[Hopefuldave]

You don't want both the taper and the flat to blue up, the D1 spec requires that the cams take up the final fraction of a thou" clearance to get an interference fit on the taper (a good fit should pretty much lock and stay that way when the cams are released, to the extent that you'd need a deadblow hammer or similar to unseat the chuck).

I've always worked to get the taper right, then measured the face clearance by the Silver Rizla method (extra-fine cigarette papers, a few tenths of a thou" thick, between flat faces of the spindle and chuck) - with the taper seated the paper should release unless the cams are tightened, when they should be gripped equally between each pair of camlock pins.

Dave H. (the other one)

[Vinny]

Welcome to the forum Eugene!!!

[plunger]

Thanks Vinny

[Dr Stan]

I don't have a clue as to the availability of back plates, etc in your neck of the woods, but the taper matching up perfectly is just one aspect you need to accomplish.  The other is the studs/pins which fit into the cam locks.  While not nearly as demanding as the taper never the less they too require decent accuracy.  The pins should also be hardened properly and the commercially manufactured ones have a line machined on them to indicate just how far out of the back plate they should extend.

If there is a supplier I recommend buying back plates that you can mount on your spindle nose and finish machining to fit your chucks and other workholding attachments.  I'd contact Shars to see if he has a contact in SA that supplies what you need.

When you machine the back plates use a center punch on the outside to mark its Zero location on the spindle nose to make sure you mount it the same way each & every time.  I always use a 4 punch mark symbol on mine.

[plunger]

Dr Stan I dont know of a place that provides backplates.I once bought a second hand one in a pawnshop to make an er 50 collet chuck.
I am having doubts of making this as it could potentially damage the spindle if the taper fit is not right. The pins could also damage the cams.
I doubt I can ever get spares for an emco v13 spindle so I need to be real careful. I may just make a spacer between my existing backplate and the chuck.

[Dr Stan]

Again I suggest contacting Shars.com.  If he cannot supply your needs hopefully he knows someone who can. Or see what you can find on EBay.