Chuck backplates, buy or make?

[AjohnwParticipant @ajohnw51620]

Steel back plates tend to pick up and bind. Cast iron doesn't. I've toyed with the idea if making a composite one. Might one day but so far no need.

I have heard of several people cleaning up boxford back plate threads. Even when close to size some couldn't do it. One said they did eventually. I'd guess a very hefty bench well fastened to to floor. These were rdg taps – usual tolerance. They leave a thread that is somewhat larger than a manufacture such as Boxford and Myford would use on their back plates. It ideally needs a tap that is on size. The spindle nose will be a couple of thou under size or should be. Personally I think that an internal chaser is a better option. I've cut several using a hand chaser in the tool post. Set carefully and run right through. Fed in at 1/2 the flank angle – slightly off to cut a little on one side.

Before making one a dummy spindle nose is a good idea. It needs a very good finish on the register part and a well cut thread. On the thread it's best to do some sums to account for the use of a pointed tool. It's just about possible to use a couple of teeth on a chaser on a Boxford as the thread od is notionally the same size as the register. Might be possible to do the same on a myford if the run off area can be big enough. The dummy nose can be tried in a known perfect back plate etc. The register part can have a short length say 0.010" under size. That way tiny cuts can be used to finish to size. Say 1/2 thou – fit has to be to 0.001 then but watch out for boring bar spring.No problem using 1/4 thou etc cuts either. Just takes longer. If you set up to do several remember the dial settings but still check.

I had wondered about using one of the morse taper plus spindle noses that can be bought for use on rotary tables etc. Having one for mounting a face plate in the tailstock afraid I wouldn't be happy about it's accuracy. They are too loose in my view. On a myford you may be able to get a used spindle cheaply. That's what I did on my ML7. It needed a new spindle anyway so came for free – after a fashion. I've still got it for my dore westbury and diviiding head for if I need it.

I've seen complaints about pre machined back plates. Both too loose and later too tight.

On the chuck register I don't think a tiny touch of taper is a problem. Tends to give a press fit if the sizes are correct. I have been known to mess that part up on my Raglan – not enough care measuring so took too much off. Ideally it needs to be a press fit.

John

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[mark smith 20Participant @marksmith20]

And what do people think of Tony Griffiths statement on the lathes.co.uk site.

A note on the "register" of the spindle end might also appropriate – the register being that small length of finely-finished plain shaft between the thread and the abutment face. Although by its name one might assume this to be a critical part of the assembly it appears that this might not be the case and could have no bearing on the accuracy of the backplate-to-spindle fitting. So, is the register all-important? Well, I thought so – until a Boxford that was passing through my hands was discovered to be fitted with a chuck where the register had been machined out to the root depth of the thread. Despite this "deficiency" the lathe turned with perfect accuracy – even deep cuts failing to have any detrimental effect. As this caused something of a discussion to develop, as an experiment a brand-new Burnerd chuck with a close-fit register was fitted and tested on the Boxford- and absolutely difference in performance could be detected. Most "vintage" lathes, even very large ones, had no register at all, their chucks just screwing on until the abutment face was reached – and these too were perfectly accurate.
The answer may be that, once on tightly the chuck will always – unless the thread is "drunken" or worn – seat into the same position. Naturally, if you want to go with the "Register-is-all-important" school of thought then no harm will result in following it. Of course, a thread is a poor way of mounting a chuck and the several alternatives, some of which can be seen here, are a great improvement.
If a chuck is stuck–click here for advice.
Tony Griffiths

Edited By mark smith 20 on 21/12/2016 18:18:33

[AjohnwParticipant @ajohnw51620]

Sounds like the had a back plate that was made fairly well. When making them it can be difficult to get the thread exactly right so some signs of the thread peaks may be visible in the register. All it needs is the flank angles to be out a bit. The thread may then need cutting too deep to allow a dummy nose to go in. This can also be caused by the flank angles on the dummy nose being out.

Actually if he had measured the sizes of the spindle he would realise just how precise things need to be. Spindle nose register 1.500 dia, thread 1.498 dia.

My boxford came with everything I need except a collet chuck. Now I have one I will need to make a back plate for it. I think I already have a suitable casting also a dummy spindle nose but when I come to measure that I may decide to make another. I have a chaser for cutting the internal thread.

My view on registers and threads in these things is that both matter one way or the other. A thread that is close enough to allow the chuck register to engage smoothly is ok but that also means that the thread needs to be pretty accurate if the register is to have a decent fit.

John

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[mark smith 20Participant @marksmith20]

John, thanks for your thoughts . Do you actually think it affects accuracy of the chuck if the register is slightly out?

I use a south bend 9a and i had to `catch the thread`, with a 60 degree tool for un threads to get them to fit, as all the back plates that came with it were boxford threaded and they didnt fit on properly at all.

I found that very strange as i bought it from a retired engineer who had developed alzheimers ,so i couldnt really ask him any detailed questions. But i cant believe he had used the lathe since new (early 1960`s) with the chucks like that.

Surely if the register is about right and the backplate locks flat against the spindle boss?? ,then as long as the backplate is machined in situ for the chuck register then it should be dead on(well as good as the spindle runout).The back plate should screw on and lock against the spindle boss in the same place each time.

Interestingly the south bend thread is more usually dead on 1 1/2" but the register is often 100 -150thousand greater in diameter.

[Neil WyattModerator @neilwyatt]

Posted by MalcB on 21/12/2016 09:26:15:

Remember – Model Engineering/Home Workshop ( when not undertaking for financial gain) is about Enjoyment and learning. Ignore minimal financial differences and go for pleasure gain every time albeit making them thru' or buying ready made and moving on to next project.

Excellent point!

Neil

[RobboParticipant @robbo]

Mark,

I assume that "no" should be inserted between "absolutely" and "difference" in line 9 of your quote from Tony Griffiths?

Edited By Robbo on 21/12/2016 21:44:59

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Robbo on 21/12/2016 21:44:32:

Mark,

I assume that "no" should be inserted between "absolutely" and "difference" in line 9 of your quote from Tony Griffiths?

.

That does seem a reasonable assumption, Robbo … but the two words are quoted verbatim, from: **LINK**

http://www.lathes.co.uk/latheparts/page7.html

MichaelG.

[John Stevenson 1Participant @johnstevenson1]

The most important thing on a threaded spindle and it rarely gets mentioned is that the shoulder has to be true because if you think about it no matter how good or bad the register or thread it's the shoulder that controls everything.

I once had a ML7 that I bought for spares and I have never seen a lathe so badly worn.. The spindle threads and register were visibly worn. The threads were really rounded and the register was barrel shaped but the chuck fitted, admittedly very loose but it ran true.

So very easy to prove.. Just unscrew the chuck, put a tad of 1 thou shim on the shoulder at one point and tighten up, then watch when you run it.

[MWParticipant @mw27036]

And ofcourse, when you first cut the female register of the plate, the whole backplate must run true, it doesn't matter how close to size you get the measurement at one point of the corresponding shape cut. If your backplate is running at 0.08 out of centre, then the register you cut will also run that much out. Therefore you will find it would be a fruitless exercise without the aid of a four jaw chuck.

Michael W

[WorkshopPeteParticipant @workshoppete]

Just a note I had to make several chuck backplates for my Maximat Super 11 and found the training weights sold in Tesco provided a cheap ready source of cast iron. They were available in several sizes mind this was several years ago i do not know if it is still relevant. The only thing to watch is the that the hole through the centre is not to large.

Peter

[mark smith 20Participant @marksmith20]

Posted by John Stevenson on 21/12/2016 21:55:57:

The most important thing on a threaded spindle and it rarely gets mentioned is that the shoulder has to be true because if you think about it no matter how good or bad the register or thread it's the shoulder that controls everything.

I once had a ML7 that I bought for spares and I have never seen a lathe so badly worn.. The spindle threads and register were visibly worn. The threads were really rounded and the register was barrel shaped but the chuck fitted, admittedly very loose but it ran true.

So very easy to prove.. Just unscrew the chuck, put a tad of 1 thou shim on the shoulder at one point and tighten up, then watch when you run it.

The shoulder – Thats what i was refering to incorrectly as spindle Boss??

[AjohnwParticipant @ajohnw51620]

I think it's best to get both right. Some reckon the register does it all. Some the thread. If the thread is too small and the register is nice and tight the back plate will hit the register rather than slide nicely onto it. Ok a chamfer helps but how big does that have to be.

The other aspect is that I have two 3 jaws. If for some reason I want to do something else while work is in one of the chucks I can take it off and use the other one. The person I bought the lathe of set that up. It has been handy a few times. The chuck I usually use has an extremely light interference fit on the register. I'll hope to achieve the same when I do one for the collet chuck.

John

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[Roderick JenkinsParticipant @roderickjenkins93242]

I recently took the easy way out and bought a ready made backplate from ARC. Slightly cheaper than buying a blank casting from RDG and is a nice fit on the Myford nose. I've come to the conclusion that, as a frequent changer of chucks and user of non-aqueous cutting fluids, seizure is unlikely to be a problem for me. Anyway, my er25 collet chuck and the Myford collet nose piece are both steel and they have never given me any problem.

HTH,

Rod

[AjohnwParticipant @ajohnw51620]

I think the problem with using steel comes when people go for a tight/very close fit and the finish probably matters as well Rod. The finish is likely to be very good on bought back plate. Correct flank angles too. The register fit on a collet holder I bought was in my view too loose but the main problem was that it wasn't concentric with the business end.

Personally I believe that the register fit determines the repeatability. It will but as some also say the thread will tend to centre what ever it is. I think that's true – to some extent.

John

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[Martin ConnellyParticipant @martinconnelly55370]

If we make the reasonable assumptions that a work piece in a self centering 3 jaw is always slightly off the center line and if removed cannot be put back in the exact same position and that a 4 jaw independent chuck requires the work piece to be centered when put in the chuck then repeatability of the register becomes a moot point. The only time it would be important is if you found yourself having to remove the 3 jaw chuck complete with the work piece and then replace it to carry on working on the part (I have done this when making a back plate!). Planning the order of the work or the choice of mounting in the lathe becomes the best guiding principle.

The most important thing in mounting a screw on chuck is that it does not move from its initial position once turning has started on the work piece. If you want to remove and replace parts then there is turning between centers, use of collets in the spindle or adjusting the part in an independent 4 jaw. Soft jaws should always be skimmed before use if the chuck has been off and refitted to the lathe.

So the question becomes does the tight fit of the register and of the thread in the back plate ensure the chuck does not move after it is mounted or is it less important than many think as even a sloppy fit will not move once mounted?

Martin

[AjohnwParticipant @ajohnw51620]

The fact that I messed up the chuck register on one for my Raglan didn't cause me much grief Martin. The chuck itself just ran out more than it need do. I've only every changed chucks with work in it because I needed to make something else. Hardly ever happens – every now and again I do spend a lot of time on the lathe.

John

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[MWParticipant @mw27036]

It is important you machine the register as close as you can to centre line of the lathe, you don't want to spend all that time cutting and be disappointed in a chuck you can't use properly…

Michael W

[Harry WilkesParticipant @harrywilkes58467]

College Engineering do cast blanks link sizes but no prices and overall naff website

H

[MWParticipant @mw27036]

Posted by Harry Wilkes on 22/12/2016 14:00:47:

College Engineering do cast blanks link sizes but no prices and overall naff website

H

Straight up, I've never bought anything from these guys, but I don't necessarily let a naff website put me off, sometimes designers like to avoid fancy borders, banners and pop-ups in order to create a website that allows everyone to access it without problems, crucial if you live out in the sticks and your internet connection is dustbin quality.

I've actually been ripped off before by a bloke who built a very convincing website, lots and lots of information on it and professional looking but couldn't be bothered to ship anything, so people would wait 8 months or maybe never get what they ordered. (A lot of unhappy people too, wanted to report him to the consumer authorities, get him black listed on paypal..etc)

They are frequently mentioned on here (and I haven't heard any bad stories? feel free to contest that) and on the back of that, I would say they are probably quite honest, they sell a lot of different useful castings and probably rely on people phoning up to get what you need..

All this iron costs money and time, so they wont keep a "ready to go" stock of every available size, I imagine.

Michael W

Edited By Michael Walters on 22/12/2016 15:45:41

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Michael Walters on 22/12/2016 15:42:47:

They are frequently mentioned on here (and I haven't heard any bad stories? feel free to contest that) and on the back of that, I would say they are probably quite honest, they sell a lot of different useful castings and probably rely on people phoning up to get what you need..

.

It's probably worth reading the 'About Us' page: **LINK**

About Us

… It explains a lot, I think.

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Harry Wilkes on 22/12/2016 14:00:47:

College Engineering do cast blanks link sizes but no prices and overall naff website

.

I think this a comparatively recent overhaul of the site. … Let's be generous and call it a 'work in progress'.

Clicking the 'sitemap' link was "interesting" **LINK**

http://www.collegeengineering.co.uk/sitemap.html

MichaelG.

[AjohnwParticipant @ajohnw51620]

I've bought castings off them while under the original owner. Very good quality. Not so much finish which was fine but the quality of the cast iron. His cast iron bar prices were not too bad either.

I called in more recently. Phoned and told them what I wanted to collect. Served by a lady who did understand what I wanted. I'm 99% sure they had changed premisses since my first call in on them. I've only been twice.

Last time I phoned them a lady answered. One comment was something like do you know that this is now several companies. The other was that she had no idea what I was asking for – I could have told them the old catalogue page number. Followed by chatter in the background and the person who handles this is in the warehouse and will phone you back. They didn't.

I suspect that there may still be a black country service for iron casting and some about that can make the bits he sold. I do wonder if he has been selling off stock for a long time or even maybe getting small numbers of bits when needed. Given the right contacts that isn't difficult to do.

John

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[JasonBModerator @jasonb]

I think the new owners are still sorting out some of the castings and until they have a new batch cast won't have an exact price, you can always give them a call to see what they have in stock at the old price. I have used a couple of their backplates in the past, usually cheaper than a slice of a similar OD cast iron bar.

[Enough!Participant @enough]

Posted by Harry Wilkes on 22/12/2016 14:00:47:

College Engineering ……. overall naff website

 

I guess one man's "naff" is another man's dream. Not one roll-over, not one pop-up could I find. No "sales-data-intensiveness" clutter.

My idea of heaven. A site I'd be inclined to visit regularly – rather than only out of necessity – if it weren't for the shipping costs of castings outside the UK.

Edited By Bandersnatch on 22/12/2016 17:04:48

[AjohnwParticipant @ajohnw51620]

I have got one set up where it's probably a good idea to have decent repeatability. Came with the lathe. There was a Myford fitting chuck and a home made morse adapter to allow it to be used with the boxford. The seller kept his dividing attachment but my dividing head and dore westbury miller both have Myford spindle noses. The chuck fits all rather well.

It also came with internal and external chasers to match the spindle nose.

I haven't had much use for the arrangement but if I do a steam engiine Jason style which is likely at some point the one I like the look of uses gears. The arrangement could be of use for other things as well.

John

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