# D1-4 Backplate Not Seating Against Spindle



## Morgan RedHawk (Nov 25, 2015)

Greetings everyone,  
I am having a problem with runout on my 4 jaw chuck (Chinese).  When I dial in the work with the dial near the jaws, then take a reading 4 or so inches away from the chuck, the runout is about 0.010.  Before I mounted the chuck to the backplate, I took a facing cut across the front of the backplate and marked the position relative to my spindle.  I dug through the forums and happened upon JimDawson's Asian 4-jaw Chuck Adventures: 
http://www.hobby-machinist.com/threads/asian-4-jaw-chuck-adventures-re-post.33311/
I decided to use the methods he described to track down my problem.  

I measured the runout on the face of the chuck, and got a reading of 0.007".  Next I removed the chuck from the backplate and measured the runout.  Same reading.  I took the backplate off to make extra sure there was no chips or anything causing the error, and when I went to put the backplate on the spindle, I noticed a thin little sliver of light coming from between the spindle face and the backplate.  Without tightening any of the mounting lugs, I am able to wiggle the backplate around on the spindle in the same way that would cause the runout reading on the face (if you catch my drift).

Its like the backplate is sitting on that conical surface (surface 2) but won't go on far enough to seat against the flat surface (surface 1)of the spindle face no matter how hard I push on it.  See my crude drawing below for reference.

My question is, the backplate should sit flat on surface 1, shouldn't it?  If so, then the taper inside the backplate is too small and needs to be widened out slightly it would seem.  The best way to do this would seem to be to duplicate JimDawson's setup where he was machining the rear of the chuck, except set to bore the taper instead (with the mounting pins removed).  That sound about right?

Thank yall for the help..hope everyone has a happy Thanksgiving!


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## RJSakowski (Nov 25, 2015)

I do not have any hands on with the D1-4 mounting system but from what I gather, this is a common problem with Chinese chucks. 

The conical surface provide the radial registration while the face (surface 1) controls angular runout..  If the chuck made contact with both the conical surface 2 and surface 1, it would be over-constrained. What apparently is done in practice is to dimension so the chuck makes contact with surface 1 while simultaneously having an ever so slight clearance with surface 2.  This requires very precise and accurate machining and close attention to tolerances.  

The taper on surface 2 is 1 in 8 meaning that for every .001" the cone diameter is increased the the distance to surface 1 will be reduced by .008".  You will also have to be very careful to dial in the backing plate to prevent radial runout.  The depth of the tapered pocket should also be greater than the height of the tapered boss on the spindle.  If it were me, I would try to identify what the tolerances for the D1-4 spec is. It appears that the nominal diameter of the large end of the cone is 2.5005" for the spindle and 2.5010" for the back plate but I didn't see any mention of tolerances.

There are a number of older posts on this subject.  I believe that the similar threads listed below should get you there.

Good luck with it and keep us posted as to how it turns out.

Happy Thanksgiving to all!

Bob


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## Tozguy (Nov 25, 2015)

I have one that does that but after greasing the D1-4 cams and studs up well, then torquing the three cams evenly and gradually the backplate reached surface 1. I would try a bit more grease and torque on your setup before opening up the taper on the backplate. A tight fit is good in my books.


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## JimDawson (Nov 25, 2015)

Try Tozguy's idea before machining.  But if that doesn't work, then machining like I did is a good option.  Set the compound angle by indicating the spindle nose taper.  Also check the depth of the pocket in the back plate, make sure there is clearance for the spindle nose taper.


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## Morgan RedHawk (Nov 25, 2015)

Thanks yall, for the replies.  I am going to try as Tozguy suggested first, and if that does not do the trick, I am going give RayC's method a go...the one from this thread: http://www.hobby-machinist.com/threads/er-to-d1-4-backplate-fitting.24596/  although I will probably ziptie the sandpaper to a paint stirrer to keep my fingers away from the action.  If that method is unsuccessful, then I will resort to machining.  Hopefully I will have time to work on it this holiday break (no way am I going to venture out on Black Friday!) and can report back on the results.


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## Tozguy (Nov 26, 2015)

Please let us know how it goes for you. Just a reminder to stay within the usable range of the cams as indicated when tightening or you could bugger them. An extra precaution of rounding all the edges slightly on the notch in the studs and removing the cams for visual inspection and de-burring would ensure smooth functioning of the D1-4 system.


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## Chipper5783 (Nov 27, 2015)

My suggestion is for the approach presented by RayC, in the link above.  Open the taper a bit with Alox type cloth- I got a very good result on a similar problem.  David


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## Morgan RedHawk (Nov 29, 2015)

I got some time to play in the shop and have solved some of my problem.  I ended up having to go the route that RayC did with the taper.  Interestingly, it took 4 operations to get mine right, same as his.  We both have the same lathe and probably the same 4-jaw and backplate.  I measured the runout on the backplate and marked the high and low spots on it.  Next, I removed and replaced the backplate several times in each position on the spindle, checking to see if the marked spots remained as measured.  They did, so I faced the mounting surface of the backplate.  The runout on the backplate is now below 0.001" and repeatable with removal and re-installation.  So far so good...

When I re-mounted the chuck to the backplate and chucked up a test bar, the runout at 4 inches was better, but still not too good...about 0.005".
I took the chuck apart again and put it on the mill table for inspection as JimDawson did.  The readings I got were all within 0.0012" of each other, so I guess that is about as good as can be expected.  The surfaces are not super smooth, so that probably introduced some error.

Next I moved on to the jaws.  I put one of the jaws in my vice using the method with the pins as seen in JimDawson's Asian 4-jaw Chuck Adventures.  Measuring across the jaw face, I found a variation of 0.006" between all of the teeth.  I wondered if the reading was caused by wiggling in the set up and the interaction between the DTI probe and the teeth, so I put a parallel atop the teeth and repeated the measurement.  Again, I got an error of about 0.006".  I flipped the jaw on its side and put a machinist square on the table and against the jaw teeth.  Sure enough, I can see light between the innermost teeth and the square.  A cursory inspection of the other jaws showed similar results, the jaws are all shaped thusly:



The most sensible solution, it would seem, would be to grind the jaws square while they are mounted in the chuck and attached to the lathe using the method I have seen used to refurbish bell mouthed 3 jaws (ring around the outside, die grinder mounted to the tool post). 

What do yall think?


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## Tozguy (Nov 29, 2015)

Sounds good although you might consider preloading the jaws inwards instead of outwards for the grind.
Thanks for keeping us up on your work.


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## rgray (Nov 29, 2015)

I recently watched a utube from suburban tool where he relieves the back teeth of the chuck .010 and then clamps round stock in that area so he can grind the jaws in their normal clamped position. Looked like a nice way to do it. Dremel..?? Not sure if I'd trust that...may work with some patience.


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## JimDawson (Nov 29, 2015)

Biasing the jaws to grip on the nose first is not a bad thing.  The jaws/chuck will deflect a bit when tightened.  It looks like your jaws might be correct as they are.  I would see how they grip before I started grinding.  The opposite condition, bell mouth, is not good, and then they would need grinding to correct.  That is the case on my 4-jaw, bell mouth.  I'm going to have to correct that one day.


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## Tozguy (Nov 29, 2015)

Any ideas for how to test the grip? teeth marks on copper water pipe? wood dowel? aluminum tube? or ?


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## JimDawson (Nov 29, 2015)

Hmmmm....Good question, I've never actually done it.  Maybe a piece of about 1 inch steel bar stock.  Maybe a piece of paper between the stock and the jaw.  That should allow you to see the marks from the jaws.  Maybe another way would be to use Plastigage (available at most auto parts stores).  That would give you the actual measurement.  

http://www.plastigaugeusa.com/


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## Tozguy (Nov 29, 2015)

Love the plastigauge idea


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## Morgan RedHawk (Nov 29, 2015)

Thanks for the ideas, yall.  I will tinker with it some more and report back.  It might be next weekend before I get a chance.  
I hope yall had a nice Thanksgiving!


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