Faircut lathe tidy up

[Jacob LeonidouParticipant @jacobleonidou84012]

Brian you're right but I did eventually grind down a piece of HSS to have a really blunt point. I think I need to experiment more with the way I grind the point. Also might have something to do with the feed and speed. I think im only running around 350rpm at the moment.

[Andy CarlsonParticipant @andycarlson18141]

Posted by Jacob Leonidou on 19/08/2020 11:24:41:

I think what you're saying is that you need to invest in a mill

Err… no. First I would need to invest in a bigger shed. I do have a small Proxxon MF70 mill indoors but that is tiny compared to the Faircut and usually used to make small scale model parts. I did look at other options before buying the MF70 but found nothing else in the same cost and size range and a big step to the next machine upwards.

So the Faircut is my only 'big' machine (and many would say not really big at all) so any milling jobs that are too big for the MF70 will be done on the Faircut… just like the old school model engineers would have done. I'm still on the case with the cross slide backlash but that job is proving far from easy. Then my vertical milling slide also needs some attention to deal with backlash.

[Jacob LeonidouParticipant @jacobleonidou84012]

Bigger shed is always the better option. I'm on the lookout for a mill with no available room. The way I see it you just need to dig deeper as far as creative space arrangement goes.

Also I bought another dead centre as one the ones I used previously to align the tailstock didn't have much of a point and I wasn't confident as to its accuracy. Gave the alignment another go and it was apparent that it was out quite a bit. Explains why my my drill bits were orbiting, they were flexing and then rotating. I corrected it and its pretty spot on as far as im concerned. Excited to start drilling some holes for the wheels I need for the 2×72 finisher im building.

Have you got any ideas for correcting the backlash?

[Brian MorehenParticipant @brianmorehen85290]

Hi Jake

Puzzled by your question backlash , Have you got cross slide movement if you try pushing or pulling the cross slide by hand if so this may be some wear in the lead screw nut or both , or is there movement if you try to twist the cross by hand on the lathe bed which may be some loos ness or wear or can this be tighten with the gib screws on your your cross slide . PS ( Always a problem trying to explain or diagnose a problem when you cant see it )

Good Luck Brian

[Andy CarlsonParticipant @andycarlson18141]

Posted by Jacob Leonidou on 03/09/2020 12:10:20:

Have you got any ideas for correcting the backlash?

Hi Jake,

At the moment I'm looking at the cross slide. The backlash is partly down to wear in the feed screw and partly wear in the nut. I'm progressing with the nut just now. I'm trying to make the new one similar to the old – a non ferrous insert press fitted into the saddle.

There are easier ways, like making an insert with a flange so that two screws can be drilled and tapped into the casting to keep the insert in place. This does lose a lttle bit of slide travel to accommodate the thickness of the flange.

The thread is 3/8 diameter 12 TPI square… which is not the easiest thing to cut, here again there are easier options like replacing the feed screw with ACME threaded rod and acquiring a matching ACME tap.

There is chapter and verse on another thread…

https://www.model-engineer.co.uk/forums/postings.asp?th=166091&p=1

[Jacob LeonidouParticipant @jacobleonidou84012]

Brian I have backlash everywhere. Gibs are all adjusted however, no issues there. It's not ideal but I don't do anything that precise so it doesn't bother me, eventually ill look into correcting the issue. Out of curiosity how tight were the tolerances from factory? Was there any backlash?

[Jacob LeonidouParticipant @jacobleonidou84012]

interesting project Andy, id be interested to see the result. Ill have to pull mine apart again to look a little more closely, mines pretty bad.

Also I need some advice on 4 jaw chucks. What would be the best way to go about purchasing a 4 jaw? I don't necessarily want to share face plates so how would I go about getting another? Im going to buy something cheap from ebay but the are chuck only.

On a separate note, I came across some album photos of another faircut with a cracked headstock repair. I couldn't find anything using the search function, would you happen to know if theres a thread? It looks very interesting.

[Howard LewisParticipant @howardlewis46836]

Being pedantic, a Faceplate is means of holding items for machinging that for some reason do not fit into a chuck.

A Backplate carries a chuck, and once machined for a particular chuck, remains attached to it, for use on that lathe.

Swapping backplates between chucks would not be my way of goinbg about things, in the interests of accuracy and repeatability. Which is why backplates, either casting, part or fully machined are offered for sale by suppliers.

In terms of a 4 jaw chuck, once you have decided what size you want, the next job is to make a backplate for it.

You are unlikely to find new ones on offer anywhere, for your Faircut., unless it conforms to one of the more or less standards used by another manufacturer.

You will need to know the details of the fixing to the Mandrel; presumably threaded, so diameter, pitch and thread form, plus length and diameter of the register if there is one.

For instance, the generally accepted standard Myford backplate thread is 1.125" diameter x 12 tpi with a 1.250" register., and can be bought as a separate item.

The raw material for the backplate needs to be thick enough to give full length of thread engagement, plus any register, after machining is completed..

Having produced an embryo backplate which is a good fit on the Mandrel thread, you fit it the other way round to clean up the face, and to bore the register diameter.. .

Once that is done, the backplate is fitted to the Mandrel in the manner in which it will remain. It will be located b the register or thread / flange. It needs to be cleaned up on the face that will contact the chuck body, so that it is square to the axis of the Lathe, and the OD turned to be a close fit in the register of the chuck for which it is intended..

You should now have a backplate which only lacks the holes for the fixings which will retain the backplate to the chuck. Most likely they will be clearance holes, but some chucks have the fixings in through holes in the chuck body, so that long bolts pass right through into tappings in the backplate.

Purely my prejudice, but if the Lathe uses a particular thread form, say Whitworth, Unified , or Metric, then for the sake of consistency of spanners / keys I would use fixings of that type. It would annoy me to have to use a Metric or A/F spanner / key on a machine which was otherwise entirely say Whit form fixings, especially since something that would conform to the majority was to already hand but did not fit properly. on that particular fastener

HTH

Howard

 

Edited By Howard Lewis on 09/09/2020 13:23:34

[Andy CarlsonParticipant @andycarlson18141]

Jake,

My spindle thread is 7/8 ins and 11 TPI… which matches the numbers for 7/8 BSF. As Howard said, you are unlikely to find a backplate with this thread so you'll probably need to make one. That will require some thought to figure out a way to hold the backplate blank.

Thread cutting is another question for you if you dont have a full set of change wheels (55T and 40T would be the most likely combination). You could do it all with taps but at 7/8 ins that will be quite a job.

…or find a friend with another lathe.

If the album you found was from Steve King then that lathe is the source of my spare Faircut bits. He sent the headstock to someone who said they could fix it and never got it back again. I bought most of the remaining bits from him last November.

Regards, Andy

[Brian MorehenParticipant @brianmorehen85290]

Hi Jake

I think Andy and Howard have provided all of the answers that you were looking for any instruction booklet will be a collectors item Can you lock your cross slide with a centre screw in the back gib. I think you will need to find someone who can make you a faceplate for any 4 Jaw chuck you get I have 4 inch 4 jaw chuck that fits my lathe comlplete with backplate I also have a 6 inch that fits my faceplate this i have never used to date

Regards Brian

[Jacob LeonidouParticipant @jacobleonidou84012]

Hi Howard, thanks for the information it was quite informative. You're right, it is a backplate. I was using the two terms interchangeably and I was wrong. Out of curiosity, as I've never removed a chuck from a backplate, is there provision for locating the chuck to centre it? Or is that done manually with an indicator?

Could you explain the register to me? I read up on it but it wasn't easy to understand.

Thanks

[Jacob LeonidouParticipant @jacobleonidou84012]

Yes Brian I can lock the compound slide. Theres still a bit of play as I can move the saddle by hand if the half nut is not engaged. its not a massive deal I will deal with it eventually. Is there any advantage with the 6" chuck apart from being able to turn larger diameters?

Edited By Jacob Leonidou on 10/09/2020 11:08:10

[Jacob LeonidouParticipant @jacobleonidou84012]

Andy that was the album. Its a shame as it looked like it would have been a very interesting thread. Was it not fixed? Looked like it had been gas welded in the photo.

I might not attempt to make a backplate as I've seen a few for sale with a 7/8 diameter hole for relatively cheap on eBay, I would just need to cut the thread which I'd be able to manage.

On a more positive note I managed to clean up my turning finishes. I found that feeding to tool really slowly by hand left a much smoother finish. Only problem with that is that its a pain to wind it so slowly over long lengths.

[Brian MorehenParticipant @brianmorehen85290]

Hi Jake

I bought a 4 inch 3 Jaw Myford chuck which had a myford thread all ready cut into the chuck .I had a friend who then got a ex work colleague to make make a backplate to suit my lathe after providing all measurements to fit my lathe this came with the thread cut to fit my lathe , the faceplate then had to be machined on its face for accuracy and the small piece in the faceplate centre machined to fit into my chuck register up to the thread that was inside the chuck all to get a perfect fit . All has been fine A 6 inch 4 jaw chuck is really a matter of choice and price I have had mine over 40 yrs and never used it or fitted it to the faceplate . Slow work getting a perfectly smooth finish looks like you are learning don't be in such a hurry.

Regards Brian

[Andy CarlsonParticipant @andycarlson18141]

Hi Jake,

The usual reference on this subject is http://www.lathes.co.uk/latheparts/page7.html

A 6 inch chuck will let you hold bigger jobs but will be a lot heavier (double or more) so harder to fit and remove plus will put more stress on your bearings. It's probably within acceptable limits for what the lathe can handle but personally I wouldn't go there.

A final thing that you may not have thought of – a 4 inch chuck will clear the cross slide if you accidentally feed too far. A 6 inch one won't. I have one that is 4 5/16 ins… which seems like a very odd size but makes more sense when you find out that it will JUST clear the cross slide.

I never saw Steve's headstock so I'm not sure of the full story but from the photo I saw I think the previous owner had added a nasty strap on top to try to keep things together.

Glad to hear your finish is improving. TBH I rarely use the fine feed myself because I don't find it fine enough. Some folks have 127T gears to get a finer feed… if you can find such a beast and if it will actually fit on the banjo.

Regards, Andy

[Howard LewisParticipant @howardlewis46836]

Coming back, late, as usual.

REGISTER

This is a diameter, or face, used as a location. So a register on the Mandrel will be a plain diameter behind the thread for the chuck, usually larger than the thread Not knowing your lathe don't know if it has one.

The Myford ML1,2,3 and 4 did not have a register as such, but their successor the ML7 had a 1.125 x 12 tpi thread with a 1.250 register.

A Backplate would have a short plain bore to locate on the male register on the Mandrel. This will not be more than 0.001 or 0.002" larger than the Mandrel.

Having made a Backplate which locates accurately on the mandrel, it then needs an external register so that it is a close fit in the chuck that is fitted.

The sizes need to be as close as possible to maximise accuracy. If you make a Backplate with a 0.001" clearance on the mandrel, and turn the OD to give a 0.001" clearance in the register in the back of the chuck, even if the chuck were able to hold work absolutely concentric, you could well have work actually running out by 0.002", despite the tight clearances.

Hence it is unlikely that a 3 jaw chuck could hold work absolutely concentric, consistently. Given those clearances, removing and refitting the chuck could well introduce a difference.

If you need two or more diameters to be concentric on a workpiece, in a 3 jaw chuck, you need to turn them without disturbing the work in any way..

With a 4 jaw independant chuck, the concentricity depends up on how accurately you centre the work.

If concentricity is not vital, you can accept run out; but if it is you need to minimise eccentricity.

So, if you were making a simple spacer with a male thread on each end, to hold a plate above another, because of the clearance between the threads and the clearance holes, the two threads do not need to be particularly concentric. With a clearance hole 0.015" larger than the thread, at each end, it probably would not matter if the thread at one end was 0.015" eccentric to the one at the other end.

But if you are fixing two parts so that a shaft can pass between the two, and run easily, the concentricity needs to be better. Assuming a shaft / bearing clearance of 0.004", you would need to hold the two ends of the spacer to no more than 0.002" eccentricity.

That may seem odd, but 0.002 here and another 0.002 there uses up your 0.004 clearance!

In mass production, where several parts have to fit together freely, sizes have be maintained closely (Tight tolerances ) if all parts are to be interchangeable and the device to work as intended.

Tolerances build up. If you were drilling a series of holes and allowed +/- 0.005 on each set of hole centres., after a few holes the tolerance build up might be such that two parts chosen at random may not be able to be fitted together. ( Studs on minimum centre distances trying to fit into holes on maximum centre distances. ten studs could differ by 0.050, and the holes in the opposite direction, giving a total difference of 0.100 )

If, however, you set the holes to distances from one fixed point with a +/- 0.005 tolerance on each distance, every part would fit each other.

Sorry to ramble on, but HTH

Howard

[Andy CarlsonParticipant @andycarlson18141]

As Howard says, concentricity is not a big requirement for a 4 jaw independent chuck backplate – it's more a matter or pride in the job.

What *IS* important is to avoid 'swash' or 'wobbly wheel' effect because a 4 jaw can't compensate for this. To do this you need your backplate to seat repeatably on the spindle every time. This means that the mating faces need to be true to each other, free of raised edges around any 'dings', no binding when being screwed on and no dirt. Then you need to turn the face of the backplate on which the chuck will sit with the backplate mounted on the spindle of your lathe. If you have a repeatable fit then the backplate (and therefore the chuck) should then be repeatably parallel/perpendicular to the spindle axis… even if not perfectly concentric.

One more thing – most backplates are cast iron so read up on machining CI and cover everything up including your nose and mouth. Think of it as machining coal.in terms of the cr*p produced and its ability to go everywhere.

Regards, Andy

[Brian MorehenParticipant @brianmorehen85290]

Hi Jake.

I was lucky my back pkate came back complements of a local engineering works and only required some small adjustments . One Favor for another

Regards Brian

[Howard LewisParticipant @howardlewis46836]

Andy is right in every respect. This why, having once machined the register for the Backplate and fitted it the right way round onto the Mandrel, you skim the face to clean it up, and machine the register that locates the chuck.

In that way the chuck seats against a face that is square to the axis of and concentric with, the Mandrel.

My earlier post suggests the sequence in which to machine a Backplate to obtain accuracy.

With a 4 jaw iundependant chuck you will need one or more DTis, (Finger or Plunger type. Preferably both ) and a base on which to mount them. probably a magnetic one will be most useful, but my advice is to avoid the adjustable ones, because they tend to be less rigid. You can't measure accurately if the datum point can move, even slightly.

Without such kit it will be less easy to centre work accurately. There are ways to centre irregular work in the way that you require, but first things first!

Cast iron is easy to machine, but DIRTY. I put a newspaper under the area being cut, with a strong magnet under it, but some STILL escapes. Wipe / brush it off the bed and any slideways as soon after, or even during machining (But not with the machine running ) Resist the urge to blow it away, you cannot be certain of where it goes, until you find something that grinds where it once ran smoothly!

Cast iron dust, despite the graphite content still manages to be abrasive!, And none of us wish to damage the accuracy of our precious machines by lapping away vital parts of them.

So, you will need to machine up a Backplate for every chuck that you used on the lathe (except, possibly drill chucks. These will locate in the mandrel or tailstock by their Morse taper shanks. )

If you want some useful reading material:

"The Amateur's Lathe", by L H Sparey

"The Amateur's Workshop" by Ian Bradley

and you will find "the Model Engineer's Handbook" by Tubal Cain an invaluable reference book.

To these you can add as time goes on, ones from the Workshop Practice Series, covering other subjects such as Drilling and Tapping, Screwcutting., or some of Harold Hall's books..

Practice will make perfect. The more that you do, the more that you will learn and gain confidence, even when you make mistakes. You learn from them so that "You recognise the mistake the next time that you make it"

We all do!.

Go for it!

Howard

[OldironParticipant @oldiron]

Posted by Jacob Leonidou on 10/09/2020 11:18:03:

I might not attempt to make a backplate as I've seen a few for sale with a 7/8 diameter hole for relatively cheap on eBay, I would just need to cut the thread which I'd be able to manage.

7/8 bore is no good if you want a backplate with a 7/8 x 11 thread in it. You need 25/32 hole for tapping.

regards

[Howard LewisParticipant @howardlewis46836]

Sitting in pedant's corner again, 25/32 at 0.781 is 0.034 oversize, and a rather slack thread would result..

Since an 11 tpi Whit form thread is 0.064 deep, the theoretical bore is (0.875 – 0.128 ) = 0.747

The chances are that a 3/4 drill would produce a slightly oversize hole, to deliver a thread with enough clearance.to prevent root / crest interference, and still be a close fit.

Even if the Mandrel does not have a register diameter, if there is a shoulder, running the Backplate against that shoulder will tend to use the thread as a taper to align the chuck more consistently.

I have made Backplates with a chamfer to butt against the shoulder, as a means of improving alignment.

HTH

Howard.

Edited By Howard Lewis on 13/09/2020 18:20:13

[Jacob LeonidouParticipant @jacobleonidou84012]

Well that was a lot of information to digest. Andy I didn't think of the clearance aspect, probably explains why the machines always have 4 jaw chucks installed (as far as I've seen).

I didn't know that they are generally made out of CI. Is that for accuracy? It would be much easier if there was compatibility between the faircut and more well known brands as for as backplates go, I'd be able to buy off the shelf. It's a pity as I'd like to be able to machine square shapes. I might focus on finding a suitable backplate soon as I've been building a benchtop belt grinder and im absolutely sick of the drill press. It's time for a change of machinery.

I appreciate the time and effort that went into such detailed responses!

[Andy CarlsonParticipant @andycarlson18141]

I'm sure there are lots of reasons for using CI. Ability to dampen shocks is one. The fact that the manufacturers are (were) set up for making lots of CI parts is probably another.

Another advantage of CI is that it is less difficult to machine to a precise fit. Because it forms fine grained swarf it is possible to take very light finishing cuts and expect those light cuts to remove the amount of metal that you had in mind. Steel forms curly swarf and this process tends to pull the tool into the work. This becomes an issue when trying to take accurate cuts of less than a thou.

Regards, Andy

[Brian MorehenParticipant @brianmorehen85290]

Hi Jake.

I was probably lucky with my backplate for my lathe .Having rewired a machine as stated this was a favor in return. Do you not know any one near you who can help. Any machine workshops near you often found local ones only to willing to help if you were in trouble when working away from home with a breakdown.

Regards Brian

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