3 Jaw D1-4 Chuck

[extropic]

If "any tool and die maker of any experience and training and they will tell you the same thing", shouldn't there be plenty of credible published documentation? Where are the text books? Where is the credible published documentation? Were they all trained by word-of-mouth?

The Pythagorean theorem is important in machining and tutorials with solution calculators for right triangles are all over the place.

Where is the credible published documentation stating there must be zero gap between the faces?

The Precision Matthews document linked (reply #18) by @xr650rRider says any gap should be filled with a shim. OK, that's one document for the zero gap side. Each reader/owner will decide for themselves how to respond to that document.
I think making a steel shim (the size and with the holes required for my D1-4) precisely flat, parallel and a few thousandths thick is a difficult task. I suppose a shim could be CA glued to the chuck to prevent contamination under the shim and prevent the shim from being a loose part subject to damage.

I hope Kitagawa responds to @Dabbler.

I also sent the following to Pratt Burnerd America (info@prattburnerd.com)

Pratt Burnerd America

Hello,                                                                  2024-09-26

Please refer the following to an expert in manual chuck mounting.

When I mount my D1-4, 3 jaw chuck, there are a few thousandths of an inch of clearance between the planar faces of the spindle nose and the back of the chuck. My question is, is that a proper mounted condition or must there be zero clearance between the planar faces?

All related surfaces are free from damage and contamination and the cam lock pins are properly torqued.

If zero clearance between the planar faces is a requirement, I would like to read a document defining the requirement. Can you provide me with the documentation of the requirement or inform me precisely where to locate it?
Because achieving such a requirement would require lapping the chuck taper to match the lathe spindle taper, I wonder if you can provide a recommended procedure for the lapping.

Regards,

If I get a reply, I will post it in this thread.

 

[extropic]

I should say that I'm not ignoring, or discounting, the statements by @mksj and @Dabbler that they have numerous chucks that fit with zero gap without any modification.

I have not had the same experience that they describe. I don't think that any of my chucks/faceplates fit with zero gap, regardless of all the elastic deformation that the cam lock pins can generate. I haven't perceived any problems with the gap. No sign of fretting (wear) on the spindle or accessories. I'm just a hobby machinist with a 12" x 36", Taiwan built, probably 90's vintage lathe and I haven't needed to attempt any extreme workpieces or extreme cuts. Most work is close to the chuck or supported by the tailstock/steady rest/follow rest, so moment forces are intentionally kept to a minimum because it seems like good practice.

Also, I haven't had access to calibrated/certified gages to inspect the conformance of my spindle or chucks with ASME B5.9 1967. I suppose that buying a set should be my first step when I win that Lotto.

I do own a copy of the ASME B5.9 1967 specification document and I explained (reply #8) what I see there.

Again, where is the credible published documentation of the zero gap requirement? If the requirement is real, the documentation should be abundant.

 

[Dabbler]

Again, where is the credible published documentation of the zero gap requirement? If the requirement is real, the documentation should be abundant.

If there should be a gap, where is the credible published documentation that a gap should exist? If that is a real thing, then the documentation should be abundant.

Frankly this is so basic that all the D1x lathes I have worked on (more than 30) across 6 tool and die shops, have all worked the way I described. You have one non-conforming lathe and that doesn't mean it is right for everyone else.

Use your lathe the way you see fit. You have that right. Don't tell beginners that it is the way all lathes should work.

 

[extropic]

If there should be a gap, where is the credible published documentation that a gap should exist? If that is a real thing, then the documentation should be abundant.

Frankly this is so basic that all the D1x lathes I have worked on (more than 30) across 6 tool and die shops, have all worked the way I described. You have one non-conforming lathe and that doesn't mean it is right for everyone else.

Use your lathe the way you see fit. You have that right. Don't tell beginners that it is the way all lathes should work.

You have misquoted me again. Please stop doing that. It is inappropriate and does not add credibility to your argument.

I refer you again to reply #14.

I have not said that a gap is required.

I have tried to explain that the dimensions and tolerances specified in ASME B5.9 1967 (Spindle Noses) for D1-4 only allow the faces to meet at one extreme of the tolerances (largest female taper, smallest male taper). As the actual parts deviate from that "perfect fit", there is a gap between the faces. Engaging the 3 camlock pins will reduce any gap due to elastic deformation, but I think the pull isn't enough to to close even a .002" gap.

I've been thinking about how I might be able to (rationally easily) test/measure to quantify the reduction in gap after the camlock pins are fully torqued. Time will tell.

 

[Dabbler]

In order to keep, the peace, here is Hardinge's mounting instructions, Page 2 near the end of the first paragraph should be clear.

https://shop.hardinge.com/medias/sys_master/images/h9b/h80/8802520432670/Chuck%20Mounting%20Instructions/Chuck-Mounting-Instructions.pdf?attachment=true

 

[Dabbler]

You have misquoted me again. Please stop doing that. It is inappropriate and does not add credibility to your argument.

That is exactly what you are saying when you say that it isn't necessary.

-From your post#8 (emphasis mine):

I agree that it's not necessary for both the faces and the tapers to be in contact.

It is necessary. I am sorry that your experience leads you to this assumption that it isn't. As pointed out in the Hardinge instructions, it is. It is so easy to get on the wrong track with what feels like corroborative evidence. I'm not condemning you, it what you have seen. I have worked on some of the nicest lathes over the years and this is how they work.

I hope you find the Hardinge document convincing, and we can be friends again!

 

[extropic]

In order to keep, the peace, here is Hardinge's mounting instructions, Page 2 near the end of the first paragraph should be clear.

https://shop.hardinge.com/medias/sys_master/images/h9b/h80/8802520432670/Chuck%20Mounting%20Instructions/Chuck-Mounting-Instructions.pdf?attachment=true

Thank you. Excellent reference.

"Mounting should seat on spindle shoulder."

In order to keep the peace I won't engage in a discussion of the difference between "should" and "must".

 

[extropic]

That is exactly what you are saying when you say that it isn't necessary.

-From your post#8 (emphasis mine):



It is necessary. I am sorry that your experience leads you to this assumption that it isn't. As pointed out in the Hardinge instructions, it is. It is so easy to get on the wrong track with what feels like corroborative evidence. I'm not condemning you, it what you have seen. I have worked on some of the nicest lathes over the years and this is how they work.

I hope you find the Hardinge document convincing, and we can be friends again!

I have not stated that a gap is necessary. I have not stated that there should be a gap.
All my explanations allow that there may be a zero gap, which is the opposite of requiring a gap.
From reply #8 (in bold).

I agree that it's not necessary for both the faces and the tapers to be in contact. According to some basic design principals, the requirement would be over constraining the chuck. The taper locates the chuck both radially and axially. Mine is a very unpopular opinion.

If the taper fit is loose enough (clearance) to allow the faces to be easily in full contact, then the chuck is not radially stiff. Does that require any more explanation?

Having the faces in intimate contact, in addition to the taper, would be wonderful, actually perfect. However perfection is very hard to achieve. Also think about how many individual spindle mounted accessories a fully tooled lathe can have. 3, 4 and 6 jaw chucks, a faceplate, a dog drive plate, a 5C collet chuck, an ER collet chuck. That's seven different accessories that would require the "perfect" fit to the spindle nose. Knock yourself out achieving that, if you like.

I was, long ago, interested enough in the issue to order the actual standards that define D1 spindle design. IIRC, the specified dimensions and tolerances allow line to line (perfect) fit at one extreme of the tolerances. As the tolerances deviate from that perfect fit, the faces separate. Clearance is never allowed in the taper fit.

To take this a step further, if I win the Lotto, I would love to do some testing to determine the axial force required to bring the faces into solid contact on a spindle/accessory combination where the pins, properly tightened, leave a few thousandths gap between the faces.

Until I win that Lotto, I'll live with a few thousands gap on clean undamaged combinations.

 

[Larry$]

I've been following this discussion. Extropic has stated the relationships perfectly. Taking into account there will always be tolerances you have two choices, a perfect fit to the tapered nose and some face gap or no face gap and some slop in the fit to the taper. You can't have both unless there are zero tolerances. Which isn't going to happen.
If you have a "Set-Tru" type chuck then going for some slack on the taper and a tight fit to the back is ideal. You get both axial and radial perfection.
If the tolerances make a good fit to the taper but a clearance on the back you get an excellent radial alignment but the chuck may be pulled into an axial misalignment as the tightening to the studs may not all be ideal, equal! Once one stud has been tightened enough to cock the chuck no amount of tightening others the others will fix the problem with out deforming something.
If your chuck mounts with some back clearance just be careful about how you tighten the cams. I.E. a bit at a time. Grinding the chuck taper in a home shop seems risky. I've tried it on a junk collet chuck. Just getting setup for the weird angle is bad enough.

 

[Dabbler]

You can't have both unless there are zero tolerances. Which isn't going to happen.

Of course you can! I have 7 chucks for my LeBlond, all that fit with tight fit on the taper AND secure contact with the axial face. No reworking of the back plates was required. I have 4 chucks in D1-4 for my 1440 lathe, and again the same story. In fact I just bought another chuck for the 1440, and once at home I expect the same story.

I have reworked 4 backing plates for other people, 3 with lathes sourced in China, and one sourced from Taiwan.The backing plates were all from China. All required light turning and lapping to get the proper fit.

If it doesn't seem real to you, it is because you aren't considering elastic deformation of the spindle and the backing plate (or back of the chuck if it is a 1-piece. Everything deflects under pressure. This is how all tapers work.

How I fix chucks (to answer Extropic's question above)

I adjust the chuck so that pushing the chuck onto the taper - by hand, with a palm thump - so that there is a .001 to .002 gap between the axial surfaces. When drawing the chuck with the cams, the chuck moves into intimate contact with the axial part of the spindle, while tightening on the short taper. During the .002 movement axially, there is minimal elastic deformation of the tapers. A little less than a half a ten thousanth of an inch. This is more than sufficient to hold the chuck and work, even on heavy cuts. The chuck requires a light but sharp rap with a soft hammer to free the chuck from the taper after loosening the cams. If you don't need this hammer tap, you need to lap .001 off the chuck axial mating surface, and try again. If you require a heavy thump by a bigger hammer, or you don't get indimate contact on the axial surfaces, your backing plate needs to be adjusted by lapping. Do NOT turn the taper on the backing plate! The Only Time you need to do this is if bluing the taper shows a serious problem with the shape of the taper resulting in an inconsistent fit. Then you are in for a LOT of work! (been there).