Constructing a D1-4 Mount

[Geoffrey Morgan 1Participant @geoffreymorgan1]

I have considering attempting the construction of a D1-4 pattern chuck mount for an obsolete five inch chuck that I hold.  I am rather intimidated by the 7 degree 7 minute something seconds taper that I will have to turn not to mention the high degree of accuracy the hole location for the mounting studs.  I understand via a post on the Practical Machinist site that at one time an article was published in the Model Engineer (or ME Workshop) wherein a simplified method was described about this undertaking.

I have tried the search engine on this site with no luck.  All comments are welcome.  Thanks, GM 

[Geoffrey Morgan 1Participant @geoffreymorgan1]

[mgjParticipant @mgj]

Sorry – is this for a mounting on the lathe spindle, or a backplate/mount for the chuck?

 

If its for a backplate. turning the taper is no trouble – its very short so you set your topslide over having done the trigonometry and using a DTI. Or sine bars. Best to use a longer plane than the actual taper – but then one exists in the form of the whole side of the topslide.

 

So if I may suggest it, stop thinking of it as some amazingly difficult angle to set – it isn’t. Its just a distance and a number of thou to offset.

 

As for the hole location, its just a straight 3 point indexing job. You set up the PCD on a mill drill, bore to size and tap.

 

But one has to say – why bother. You can buy a 1-4 backplate ready to fit from people like Chester for not very much. Put it on the lathe and turn the register. The only tweak when doing that is to put a dab of paint on the spindle and a matching one on the backplate, and then it always goes back on in the same position as it was machined. Sort of helps accuracy a bit..

 

 

[KWILParticipant @kwil]

Beware, some of the backplates that are offered for sale are VERY poorly made, see before you buy!

[KWILParticipant @kwil]

7 Degrees 7 Minutes 30 Seconds,  also bear in mind the tolerance on the diameter of the taper, the Spindle Nose dimension at the base of the cone is  2.5005″ + 0.0005″, this controls the concentricity of the mounting.  It would be worth making a plug test jig if you do not have another spindle nose to check against. You make and check your plug guage, then retain the final topslide angle to cut the internal taper.

[mgjParticipant @mgj]

Yes well I’d have thought that if you do a plug gauge and then use exactly the same setting to do an internal taper – it probably is all going to go pear shaped- because one has reversed the thrust lines.

 

You have to make the plug, and then adapt the angle using blue as a guide.  A lot of people recommend using a tool upside down at the back of the job for that reason. Using the same setting without reversing the tool is not a grand idea.

 

To be honest, these things are best ground to a finish, and while the amateur can do it, its just such a pain to set up a tool all aligned and backlash free.

 

The alternative method is to cut the internal taper at the same setting – measure the error (which you will know because you have done your geometry and then adjust using a DTI) – on a test piece. Then once you have all set right, then you cut the internal taper.

 

Bite the bullet – buy one. A Bison/Toolmex one if you can afford it.  Or, if you are not paranoid about accuracy, you’d probably get a new chuck and backplate complete for a similar cost. At the end of the day, unless you are paying a lot of money for a 3jaw, 2-3 thou of error is pretty standard and as Circlip said, if you need genuine concentricity you have to turn both dias at the same setting if using a 3 jaw.

 

It’s not as if this were for a collet chuck or something like that.. 

[Geoffrey Morgan 1Participant @geoffreymorgan1]

Thanks for the advice.  The idea is related to lathe application.  I was considering making a drive plate for use to drive a dog for between centre work.  The face plate supplied with my machine is a massive unit and it just seemed more convenient to have a more specific service component.

Most of the chuck backing plates commercially available are too thin in section (beyond the registering shoulder) to allow for the drive slots to be milled proud of the spindle.  It also seems that since the decline of the Western lathe manufacturers, the Asian machinery makers do not offer the drive pattern plates that used to be standard.

I like the idea of a plug gauge which I can check with Prussian Blue, etc.  At least with that scheme I would have a matched set of component tapers, although I am sure that very few of the Asian machines would meet exacting BS or American standards. 

[mgjParticipant @mgj]

Sorry, I thought this was to mount an old (but good?) chuck on. Ergo since this backplate would affect more or less everything you hold, it was worth doing really really properly.

 

If all you want to do is drive a dog – for Gods sake – buy the cheapest backplate you can – forget milling much. Just bolt a broad strip of steel to it with slot pre milled. Add a balance weight, and away you go.  (That way you can bolt any driver onto it you want, and most drivers are either a cranked dog (modified) to fit slot, or a locked up bolt MIG/soft wired to dog)

 

Lord above, just to buy the chunk of steel you need to do this as a blank is going to cost as much as the whole shebang could be done for – take several evenings too.  Actually its no more than an hours work- unless you want to make it so – and that includes a coffee stop. 

 

If you REALLY want a plate in this application, buy a backplate, bolt the disc to it,(to bring the front face forward) turn  the inside hole, skim OD  & repair to house for well earned coffee before setting up on rotary table for slots. (and thats if you don’t want to buy a smaller faceplate which are freely available)

 

But again, considering how rarely we do turn between centres (unless you have a particular project in mind) why bother? 3-4 jobs a year, (some of which can be held in a 4 jaw at one end)  just use the faceplate, save the cash and time?

[KWILParticipant @kwil]

Now we find the real requirement the above discussion has become academic.

 

So one question for Meyrick, reversed thrust line? 

 

If you turn the plug with a boring tool set parallel to the lathe axis and the machine running in reverse, check the taper angle [fortunately my DRO wil measure that angle without me doing the trig], then bore the taper with the machine running forward, then tool spring apart, the thrust line are the same??

[mgjParticipant @mgj]

No thats absolutely right, because you have kept the thrust directions the same by running the machine in reverse for one of the operations. But to be fair, you made no mention of running the machine in reverse.

 

Its just that for most, “At the same setting” would probably have meant, (and I assumed that, for which I apologise) set taper, turn plug. Then bore the tapered hole. Then one would have been terribly surprised when it didn’t fit properly.

 

To be strictly correct shouldn’t one do it with the tool upside down and at the back of the crossslide, because that keeps the feeds screws in compression OD and ID? Its the fact that the backlash is taken up in opposite directions that leads to the small error which can be important in critical taper fits – both compression into the bed, feedscrews and saddle across bed (which is 3 points with socks off).

 

Which is why the commercial people grind them. With such very small cuts that sort of error is much less of a problem, particularly on a machine set and adjusted to produce one taper to perfection.

 

(No PM Kwil – if I argued against a point in public, it deserves a public answer )

 

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