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New Chuck won’t screw on

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brian jones 1127/07/2021 02:36:26
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309 forum posts
56 photos

I had similar problem with an adapter faceplate 4" od. the thread would start to bind half way along. i didnt want to push it as my chuck - burnerd - slips on easily

wotodo?

a) layout £20 on a plug tap

b) try some fettling with a dremel

c) use a thread boring bar as a scraper (the Myford is 1-1/8"UNF x 12tpi btw so 60deg ok

d) a 3/4" bsf plug tap has the same tpi for a bit of scraping

i spent half hour dremelling and got a working job

but its frustrating and what you can expect with ykw stuff

 

btw Ive got an original 6" faceplate works fine

in the end i didnt use the adapter plate to save money fitting a generic new chuck and blew the kids inheritance on a 125mm 3 jaw ( I desperately need a set of outside jaws) c/w ready made Myford adapter plate from a well known supplier from here

 

Sometimes all the aggravations gets in the ways of doing some real work

frown

 
 

 

 

Edited By brian jones 11 on 27/07/2021 02:59:49

brian jones 1127/07/2021 03:05:30
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309 forum posts
56 photos

the subject of nose threads generated a lot of hot air

https://www.model-engineer.co.uk/forums/postings.asp?th=122670

The standard BSF/W 1=1/8" thread is 9 and 7 tpi UNF is 12 tpi

e) one trick is to use a 1/2"W ht bolt which as 12 tpi and to cut a slot along it so as to make a set of cutting teeth like a tap, this can be used with some grinding paste to gouge out the thread (old fitters trick to restore damaged threads)

 

1.125

28.75

12

2.117

1.0228

25.979

0.511

1.298

 

https://www.gewinde-normen.de/en/unified-fine-thread.html

Can you believe that Myford would have gone to the considerable expense of commissioning a special thread for the nose, UNF would have been available from america

the chuck is located on the 1.25 shank and on the back face, slight looseness of the thread is expected, what you dont want is a tight fit.

OH well let the Vesuvial fire storm rain down upon my kalbocrying

Edited By brian jones 11 on 27/07/2021

Edited By brian jones 11 on 27/07/2021 04:08:20

Howard Lewis27/07/2021 18:11:45
5237 forum posts
13 photos

Brian,

The "standard" Myford Mandrel thread is 12 tpi BUT 55 degree WHIT form not 60 degree Unified .

The 12 tpi Whit form dates back to late ML lathes manufactured in the late 1940s (The early MLs used 7/8 x 9 , 7/8 BSW, before moving to 12 tpi, The Series 7 launched in 1947 used 1 1/8 x 121 tpi. )

Even the Taiwanese lathes available until, at least 2004 used Whit form threads for their chucks, (Mine is 2 1/4 x 8 tpi WHIT form! )

Howard

Martin Kyte27/07/2021 18:22:11
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2536 forum posts
45 photos

I would think any thread with flat top crests (like unified) would be unsuitable for chuck fitting as the crests would be more prone to damage. The whitworth form with it's rounded crests and valleys would be less prone to damage and picking up and trapping particles of swarf.

regards Martin

Richard Jarvis27/07/2021 22:05:49
25 forum posts
6 photos

I tried a dti on the backplate and found about 1 thou runout but the needle was constantly moving due to a bad surface finish. I will try to skim it tomorrow. Hopefully this picture will show the surface.eb6b87cc-2a19-4044-a230-45ed90234507.jpeg

brian jones 1127/07/2021 22:19:58
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309 forum posts
56 photos

WOW the machining there shows a ripped finish (perhaps a Covid tool?). Hss should give a nice matt finish, no lube needed assuming grey CI 50 sfm

brian jones 1128/07/2021 12:09:48
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309 forum posts
56 photos

So Im not so clever either, I just bought an HBM 3 jaw from RDG ready to screw on it said

Well I got most of the way there then it tightened up and wouldnt budge any further about 1.5 turns to go

Still it spins ok and i have got the energy to mess around with a dremel or complain and send it back

I shall live with it and get on with some work angry

I wonder if I complain they will send me one of their plug taps on loan for a bit of reaming

just makes you wonder do RDG check their stock on a standard nose before they send it out. This is not the first time this has happened - ive seen it reported on this board. Its not beyond reason to expect RDG to carry their own go-no gauge for this rather critical component

Disappointing RDG, but Ill live with it, maybe make a half washer to take up the slack, when ive got nothing on (in this hot weather

The positive bit is my old Burnurd chuck is now sitting happily up on Doreens nose

So there maybe milling ahead

Anyone remember where this other member had trouble and had to return his chuck (not certain it was RDG?)

JA28/07/2021 12:56:21
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1217 forum posts
73 photos

Do RDG/Myford read these postings? Perhaps they should.

JA

Richard Jarvis28/07/2021 12:58:23
25 forum posts
6 photos

Have you checked the machining on the face plate?, I managed to get a better surface finish using a 12mm shank tool with what I think is a brazed tip. I tried a HSS but that left as bad a surface as original, that might be the operator at fault as I had attempted to grind it myself.

Richard Jarvis28/07/2021 13:04:13
25 forum posts
6 photos
Posted by JA on 28/07/2021 12:56:21:

Do RDG/Myford read these postings? Perhaps they should.

JA

Well they did not answer my last correspondence seven days ago so I decided to have a go myself with help from the group.

brian jones 1128/07/2021 17:05:09
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309 forum posts
56 photos

Well Richard, it seems ive caught your nose problem myself with a new 5" RDG 3jaw "screw on chuck" that does complete the travel.

This is so annoying as the thread doesnt have to be an interference fit. The chuck is located on the shank shoulder (1.25dia) and the back face. the thread merely clamps the surfaces together

I have lashed out on a plug tap from chronos and hope I will solve the problem @ £14. If it works I will put the tap back up for sale here, Maybe the tap can be passed around and help others in distress

I cant live with a half fitted chuck, never knowing when it might move

angryangryangry

When I have solved the problem and regained my normally mild mannered composure, RDG will feel the hot breath of my displeasure at their carelessness and a demand for compensation. All will be duly reported here

duncan webster28/07/2021 18:34:47
3456 forum posts
63 photos

If one buys something and it's not fit for purpose, send it back. Any attempt at rectifying it, buying a tap for instance, will void any warranty, and anyway why should you be put to the expense of a tap.

one advantage of ebay/paypal is the no quibble return

Edited By duncan webster on 28/07/2021 18:36:04

not done it yet28/07/2021 18:54:23
6279 forum posts
20 photos
Posted by duncan webster on 28/07/2021 18:34:47:

If one buys something and it's not fit for purpose, send it back. Any attempt at rectifying it, buying a tap for instance, will void any warranty, and anyway why should you be put to the expense of a tap.

one advantage of ebay/paypal is the no quibble return

Edited By duncan webster on 28/07/2021 18:36:04

As well as ebay, I would recommend everyone to ask for (or even demand) a receipt for expensive goods at exhibitions, etc. I’ve heard more than enough stories of poor items not being accepted as sourced from stalls - RDG not excluded in that - although I cannot remember the particular item(s) involved.

Flywheel28/07/2021 19:06:41
31 forum posts
1 photos

I had a similar problem with backplates some years ago, at the time I purchased a set of taps 1-1/8 x 12 tpi BSF made by Draper, these have served me well over the years in sorting out faulty backplates. The spindle nose thread is 55 degrees and most certainly NOT 60 degrees.

I am based in South Yorkshire and if anyone who lives in my neck of the woods has any problems with backplates or chucks etc please message me and you will be welcome to come and use the taps to sort out your problems

clivel28/07/2021 21:24:39
324 forum posts
13 photos

I don't think that the problem is unique to RDG chucks.

My secondhand ML7 came with a Burnerd 3 jaw chuck which was mounted on the spindle, as well as a Myford catch-plate and faceplate.

A few weeks later I purchased a secondhand 4 jaw Pratt Burnerd chuck in good condition. I was horrified when I first tried it to find that it would only go on about a quarter of the way before getting stuck.

Trying the catch-plate and faceplate for the first time neither would go on all the way. I was convinced that there must be a problem with the mandrel nose. But I then spent some time with a small brass brush and some strips of brass making absolutely sure that all threads were as clean as possible. Yet, although this improved the fit, none except the 3 jaw chuck which was originally fitted would seat all the way.

In desperation, I ordered a Myford spindle tap from Chronos - shipping to Canada was more expensive than the tap.
I first tried it on the catch-plate, and although I didn't see any filings when I ran the tap through, afterwards it was a perfect fit. Same with the 4 jaw and the faceplate after receiving the same treatment.

Clive

brian jones 1129/07/2021 01:46:35
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309 forum posts
56 photos

It seems that this Myford nose design is fundamentally flawed and will always be of potential for trouble on new parts

You see 1/2 thou oversize and all is sweet, but 1/2 thou undersize, whole pile of grief

you would expect RDG to run a plug tap through its adapter plates (made in india?)before selling them

is that too much to expect?

 

As for sending stuff back, not that easy for some living away from the now disappearing post offices, and there is the likelihood of getting another back with the same (unchecked problem - as I remembred reading from another post - lost in time, only on the third try did he get one that worked

thats a lot of grief

I will just engineer my way out of the problem = its what Myfordians do

btw just to show we are not alone

https://www.model-engineer.co.uk/forums/postings.asp?th=52289

Edited By brian jones 11 on 29/07/2021 12:00:15

Michael Gilligan29/07/2021 07:02:48
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18734 forum posts
916 photos
Posted by brian jones 11 on 29/07/2021 01:46:35:

It seems that this Myford nose design is fundamentally flawed and will always be of potential for trouble on new parts

You see 1/2 thou oversize and all is sweet, but 1/2 thou undersize, whole pile of grief

[…]

.

I think that’s a little harsh, Brian

The same basic design has served well on many machines.

What seems to have been lost is the necesssary attention to detail in manufacturing.

.

As John Ruskin is alleged to have put it:

There is scarcely anything in the world that some man cannot make a little worse, and sell a little more cheaply.

MichaelG.

Flywheel29/07/2021 10:07:07
31 forum posts
1 photos

897199.jpg

These are the taps that I purchased for sorting out the myford backplate threads,

when I dug them out of the shed they where not Draper has I thought but made by Garvin and are Whitworth not BSF (apologies for the error in my earlier post)

I have checked on the Garvin website but sadly they are no longer listed

Peter

Andrew Tinsley29/07/2021 10:31:08
1461 forum posts

A friend of mine purchased 3 Myford back plates from RDG at a reduced price (via Ebay), which were described as faulty. They all fitted the Myford spindle , with no problems.

As you seem to have problems with anything you have bought, my money is that your spindle is at fault. If that is not the case then why not buy a "Myford" tap from Tracy Tools and be done with it. For less than £20 you have a solution and everyone can relax.

Andrew.

SillyOldDuffer29/07/2021 11:08:20
Moderator
7482 forum posts
1657 photos
Posted by brian jones 11 on 29/07/2021 01:46:35:

It seems that this Myford nose design is fundamentally flawed and will always be of potential for trouble on new parts

...

Compromise rather than flaw. Threading the spindle and backplate is cheap to do and allows chucks to be changed quickly, most of the time, ahem. Disadvantages, the threads are vulnerable to damage and dirt; they are likely to jamb if not regularly loosened, and the chuck is likely to come off if the lathe is run in reverse. Can't give top marks to a design that won't unscrew when its supposed to, and comes off when its wanted to hold.

A slightly more expensive alternative is the flange/bolt system used by most Far Eastern hobby lathes. This arrangement has no critical threads to damage or keep clean and is positively fixed in forward and reverse. On the downside: slightly more overhang; takes longer to change (3 nuts), and because there's not much room to manoeuvrer it pays to have slim fingers.

Of the two I prefer the flange system (I have small hands), but when quick change is necessary the professionals reject both and cough up for one of the cam-lock or other better systems.

Don't expect professional features at hobby prices - it leads to disappointment! To my mind unnecessary too: all I need is a machine that does what I want, and although Myford and Far Eastern lathes have multiple disadvantages, they're a good fit to most amateur and small workshop needs. On the subject of expectations why assume the new backplate is faulty when the lathe's spindle thread might have had a hard life? In engineering it's best not to assume anything - measure twice, cut once.

Dave

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