Member postings for Ajohnw

The prismatic beds generally have huge width to length ratios. The faces of the vertical V can also provide large areas to resist wear.

The myford way with the front guide attempts to put the lead screw and rack central and beneath the guide as they all do which should lead to a lack of twisting forces as the saddle is moved. My ML7 which had hardened rails showed around 0.0005" wear on the rear edge of the front rail. In practice it could have been more because the only way I could measure it was with a straight edge - to remove any wear from the front which appeared to be ok.

I'd be very surprised if Myford didn't do all of the rail grinding in one setting but they may have ground the underside of the rails as a separate setting. i'd expect them to have a machine that would do all of it at one setting though. Perhaps they couldn't afford a slide way grinder.

Chis Heapy's, hope I have spelled that correctly, idea of improving the narrow guide on a myford was to add a gib strip to the rear of the front rail. I can't see that this would help other than making it easily replaceable and allowing the lead screw to be correctly aligned. I assume he got this idea from some one maybe Tubal Cane. He never gave any details, just mentioned it.

I can remember talking to David P and am pretty sure he was the one with a form grinder but it could have been some one else that worked there. I had a Raglan at the time. It's odd that the similar bed arrangement on those does wear better than a Myford - it causes less trouble just as prismatic V do.

There was a slideway grinder in Worcester as well. Brand new around 12 - 15 years ago. They offered to see if they could convert my ML7 to a prismatic bed or even fit it with wear strips. I wasn't happy about the amount of material they wanted to remove. I can understand their problem - set up time. They can grind the grinders table to make sure that is aligned - not keen to do that - then stand the bed on parallels upside down and grind the feet true and then turn it over, set up and do the grinding - all in one go. Actually in this case the saddle was carried on a sub table behind the bed with the V matched by off setting it so that was done too by the same diamond wheels.

John

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Collins gives the info a bit quicker than oxford Neil but both infer the same thing -

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After all Collins is concise.

You'll get me going on the phrase "this begs the question" if and when comments crops up.

John

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I don't know if (may have the name a little incorrect) David Piddlington that used to work at Reeves when they were in marston green is still around but I seem to remember that he would do this for people. He also used to design things for them. Age wise he probably is still about.

These people are in B'ham and it seems it is possible to park outside of their premisses.

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One thing I would mention is that you want to turn very very slightly concave, thou's. All of these people can be a bit extreme.

I'd wonder how bad your bed wear is and if you have tried locking it at various angles - they will rock when worn as most of it is usually in the saddle and some on the bed as well even when they are hardened.

John

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I seem to remember a very simple design appearing in one of the model engineering mags some time ago based on using a bar for the bed. Might have been MEW. Probably square bar rotated by 45 degrees.

There are some interesting ideas from older lathes. For instance one plain lathe uses a totally different saddle for screw cutting. That is then moved along the bed to where it's needed just like the usual slide arrangement.

Some old cheap lathes used nothing more than a pair of round bars for the upper slides rather than dovetails. Some also used Myford type bed rails on the upper slides.

My father reckoned the best way to get a super precision small lathe was to make one myself. I'd been thinking in terms of using flat ground stock sections. His attitude was why - ordinary steel sections only vary by thou's. Makes sense really as things are going to have to be fitted and dowelled / double roll pinned.

He mentioned that an interesting lathe with an unusual design of bed was produced by one manufacturer just after WWII. A slant bed. They can have larger swings and be very rigid compared with ordinary beds. The saddle hangs down from the back so the bearing surfaces can be very large. Trouble is that the cross slide needs to run horizontal. I'd guess he was thinking in terms of a very thick fairly wide steel section. I feel it would be too difficult to make but he might have been suggesting a rather unusual spindle to bed arrangement - bed flat and spindle moved back rather than on centre. Not sure. He'd usually only gave me clues especially as he got older.

One thing that is a fact is that plain bearings are best. It struck me that oilite's could be used to save keeping on having to make them. Maybe even running on needle roller bearing inners pressed onto the spindle. it wouldn't be too much of a problem to make an attachment that could be fitted to the bed to finally size both the bearings in the head stock and the tail stock by hand. It should be just a case of removing a few thou of material. From what I can gather this was done by people a long time ago to save the pain of having to accurately scrape them. The manufacturers have used similar ideas even jigs to position and size them often rotating so that both bearing can be at the same height and alignment.

Thrust - a race of some sort will be best for that but for insanely high speeds I suspect Pultra used hardened steel running against phos bronze as I feel that the thrust bearing they used on some would have a hard life at 10,000rpm.

I think about the slant bed and wonder how every now and again. I wonder if what he was thinking about would be better described as a slant head. In my minds eye it makes sense.

John

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LOL It's funny how often people comment on word use like this but don't check.

John

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Any chance of a scan of the missing section Peter or the whole thing ? I use filebin.net if I want to put something on the net for others to download. No registration or any other messing about with them.

John

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The nice thing about the older ones with this type of flanges is that I can machine any size I want as the spindles are long enough to take decent ones. The flanges serve as bushes as well and take the spindle up to 20mm. The actual spindle is probably 15mm dia or something like that. This gives a decent length to ensure the flanges are square to the shaft. They are a very good fit on the shaft. The fact that I could actually see the flanges is why I bought it. I had noticed that these and some of the other black and decker ones usually sell and had thought about getting one before but if the flanges were just pressed no point. Even my larger newtool one in the garage has decent flanges - that's about 18 years old and wasn't that expensive but penny pinching marches on. Probably be 1/4" dia spindles next or metrication such as 10mm instead of 1/2".

One good thing about them is there isn't much to wear out - just the bearings which should be easy to change. Only problem having used some what worn ones at work the quiet rhythmic thrumming noise has a certain amount of nostalgia so I will probably just regrease them.

I do wonder about the wheels that are being sold on the cheap ones. I took one off and noticed something that has a rather dark colour in the centre. I wonder if that's something cheap which is then coated with the actual abrasive. For a 20mm bore I will probably have to go to a proper shop.

John

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I've give up trying to find a 6in grinder that supports the wheel well enough to run them reasonably true so bought this one

It actually has sensible flanges to locate the wheel. Came with the scratch brush on and out of balance so bounced all over the place. It hardly moves around at all with it off. Must be modern as it uses metric bore wheels and is by Black and Decker and made in England.

While we can't expect extraction points on cheap grinders why do all of the cheap 6in ones use stupid pressed flanges.

£16 off ebay and is usable as it comes really. As the bearings are a bit worn it makes a nice cyclic thrumming noise so I suppose I might fix that.

John

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In my view most lathes have cut depth and feed rate combination for some material that will give the best even finish. This might result in an obviously turned finish because the feed rate has to be so high. If the power feed is too slow for the cut to take out the play it can tend to oscillate and bounce about. I get that to a certain extent on my Boxford at times - fix increase the feed rate and it goes away. It's most likely to happen at 1 1/2 thou per rev and usually disappears even with just a small increase. I do mean small as well, the steps at the fine end are insanely tiny.

I'm a bit bemused by the centre too but as it's a none rotating one I'd guess if Brian used enough to push the whole lot home it would overheat. The centre wont stop the other end from moving about at the sort of pressures he could use.

The bearings might explain his depth of cut problem to some extent as well. Best explained with a Pulta I bought with a 3 jaw chuck that is bell mouthed. If a cut is taken too far away from the chuck the bar moves and grabs and makes the belts slip. A bit different to loose bearings but the same sort of thing might happen. Brian not getting the work gripped fully by the chuck can have the same effects. I did explain how he should put things in the chuck earlier so hope he is doing that. The actual run out of his chuck is likely to be pretty low but not if the bar is cock eyed in it and if it's like that the work is very likely to move. That might be another reason for the problem but why sudden?

John

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Use hopper's tool with the radius and set it on centre with the tailstock - usual thing - a very slight touch low to actually on centre. Be sure it's not above centre.

Have about 50mm sticking out of the chuck but make sure you are gripping it correctly. Face the end. If I'm right you will probably get a pip left in the middle that you may be able to keep going at to remove it or the tool might just always seem to jump under it. Often they just break off.

Then take a cut along it to clean the outside diameter up. I think if you stop at the end of the cut and measure the diameter up by the chuck it will be less than the end because the bar is lifting. It can do something similar if the bar is bending but I'd be surprised given the size of cut you can take if that will have much effect on 16mm bar.

As you may have problems with the first cut try the same thing again. The let us know what the difference in sizes are.

I suspect the bearings are loose but it really would be best to REALLY ensure that this is causing the problem before doing anything about it. It explains the rings your getting because the cut lifts the bar but each time the feed rate drops off the bar drops and creates a ring. This can be improved by increasing the feed rate especially if power feed is being used - the cutting pressures stop high and constant enough all of the time to hold the work steady. The cut has to lift the chuck, spindle and work. I'm hoping 0.3mm is enough but the rad on the tools will help. If the feed is too slow all sorts can happen. If the work lifts as it's being cut the tool will cut again when it's run back to the start. That can also be down to the work bending - centres help with that. This is why hand feeding isn't easy because there is always some degree of flex some where or the other and even micron deep grooves will show. The better the finish produced the more apparent they will be.

As this has happened rather suddenly it shouldn't be bearing wear which will cause the same problem eventually. What can happen when lathes are assembled is that the bearings aren't pushed fully home so they move when the lathe is used. My Boxford had this problem even though it had seen years and years of use before I bought it The bearings loosened each time I drilled a 1in hole. Looking at the results you have had it wouldn't surprise me that if you held 300mm of bar tightly in the chuck you would be able to waggle it about and feel the play. People are usually concerned about amounts that need a dti to detect - some also bend the bar trying. It's always best to check this sort of thing by turning unless the problem is rather gross.

John

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What diameter aluminium bar do you have ? I'm pretty sure I know what is causing the problem.

John

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I'm glad the belts and they torque they can give cropped up. It seems that there is a retailer around that might say buy a 2,800 rpm motor to get a 2,800 rpm spindle speed, throw other pulleys and any gearing away and set what ever speed is needed via the inverter. If only.

I haven't done my mill but have changed my lathe. I did what a lot of people do upped the motor power. This means that I can reduce speed and still have the same torque at the cutter as I did have. It can give a reasonable speed range. This subject often crops up elsewhere and some one said it's wonderful and posted a video where the inverter was used to bring the speed right down. It's an excellent example of when extremes may work out. He drilled a sizeable hole with the inverter at 50Hz, this took some time. He then changed the cutter to a sort of fly cutter to face the area around the hole and then brought the speed right down with the inverter and used it which took seconds so there was no chance of burning out the motor due to the cooling being reduced. I've always wondered what happens if a separate fan is fitted as the inverter will control the motor current. Mitsubishi inverters will model the thermal behaviour of the motor which should help but for their own motors. They also have a random switching setting which does a lot to remove the noise problems this type of drive has.

It is possible to get motors that are intended to be driven over a wide speed range. They usually have a fixed speed fan and are balanced for higher speed running and are costly. I asked Brooks about running at high speed and got the answer that he doubted if they made an 1400 rpm armature that would have problems running at 2,800. Wont burst in other words. TEC show how they think their motors should be run on their inverters in one of their catalogues if it can be found. This should give people an idea what ordinary motors can do. One of the catalogues doesn't provide any data at all.

I went from 1/2 to 1hp on my lathe. In part because I had let some of the smoke out of the 1/2 hp a few but there was still enough smoke left in it to allow it carry on working after it had cooled down. As I was making the change I also fitted the inverter. I generally run it at 40 to 80Hz but mostly up to 60Hz. I'm in no rush when I work so didn't change belts that often anyway.

John

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I did mention above centre turning in another thread. It's something people who can turn normally might like to play with.

If aluminium is sticking to the tool try reducing the speed you are using by 10 - 20% . Use Hopper's tool and as he mentions a rad will help improve the finish but it will also do something else that may help. If there is any aluminium sticking to the tool it can be flicked off with say a small screw driver or what ever.

Hoppers suggestion of using a centre will help correct another problem. If you don't have a revolving centre there will be need for some lubrication on it - lard out of the kitchen will help, grease would be better but if the centre is too tight it will still get hot and the ally will expand making it even tighter. It can expend when it's being turned as well.

Next question is that after you have taken a cut does the tool cut again when the tool is just wound back to the start without the centre in? Much - tiny shaving etc? Also if you measure your work is it showing much taper along it's length ? Do things improve a bit if you keep taking the same cut?

John

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Edited By Neil Wyatt on 15/09/2015 14:47:19

There is a need to be fair Chris - cost.; It's possible to buy a very small Schaublin even now. Where I feel things are wrong is too much penny pinching though the pennies are probably some 10's of pounds as far as a buyer is concerned. If Schaublin quality is needed costs would escalate who ever or where ever it was made. Part of the price increase would be down to how many would be sold - not many at their prices. Many things are made to suite a particular market price wise. Actually in some areas that sets the price not the actual cost of producing what ever it is.

By the time Brian put a motor on a small Schaublin 70 and had it on a suitable stand he wouldn't be at all happy with the weight. Probably not with the weight of the lathe alone either.

I can see plenty of things in my workshop that aren't from china, some things I made myself, some others made, some used some new. I've recently added a mini lathe as well. Used as there is no way I would pay the new price for one of these particular ones. I've found a stupid design feature already. The way it's mounted and if I followed the suggestions in the manual it would probably distort the bed. A real silly. No feet projecting from the bed. Instead the casting has been drilled and tapped making it a bit difficult to mount it evenly without any distortion. The curious thing is that normal feet with a simple plain hole would be cheaper to produce and easier to mount. I sometimes think that the people who design them and also buy them don't look at lathes in general and then wonder why things have been done that way. Simple solution in this case - just make to 2 plates and fasten them to the bed and use holes in these to mount it. The person I bought it off made some screw jacks but they aren't suitable for the way I need to mount it. Most people would probably do just what the manual suggests. It came with a test report. One entry is interesting - if the head stock bearings are loose apply pressure to remove the play and then take the measurement. Actually as there is a little noise when the lathe starts from cold that rapidly goes away they are probably about right but as usual no sensible way of adjusting them is mentioned. It could be some other bearing anyway. There are several possible candidates.

John

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I don't advocate buying mail order on a whim and sending back. The only reason I mentioned it is that if he wants them Brian is in a bit of a fix but must admit I don't see the need for a rushing and in real terms the Oz supplier should be able to supply them.

Personally Ketan I feel that the baby lathe suffers from a type of size problem. I'm a design engineer that has always worked in manufacture so am well aware of it. There is an assumption that because something is smaller it must be correspondingly cheaper but unfortunately when it comes to things that need machining it really isn't as simple as that. Or anything else really. For the same features the only thing that really changes is the cost of the raw materials which will be relative low and a 2ndry knock on effect of reduced machining times which wont be that significant over a range of sizes. The plant will still cost the same and etc. So the next step to reduce cost and it does do that is to omit features and or parts that would normally be there. That's why I said not that one to the friend, the general make up the machine. He by the way is fairly competent. I had warned him about the tidying that would probably be needed. I've done that myself on a small miller - bought used off some one that couldn't make any use of it. I did, it mostly needed adjusting. The novice that bought it off me was also happy with it. Casting kit is a term I have seen used round here so just repeated it.

I might add that I bought 2 baby lathe compound slides of you Ketan and didn't send them back. No use to me as worse than expected. I could sort them out but wanted something quickly and the clearance used on the lead screw "bush or lack of it" suggest I might find that they can't be sorted out. I feel this sort of thing is another aspect of Chinese lathes at times. In this case the parts have been machined and in real terms shouldn't even need to be as they are even less a bush.

The baby lathe isn't unique I also knock Myfords with good reason but again compared with what could be called real machines they were cheap as shocking as that sounds. I often mention ML10's and Speed 10's to people looking for a small lathe. Another example of a machine on a budget at the manufacturing end. Personally I feel s7's could have been better for little additional cost other than maybe plant but going on the later offering they bought that anyway.

In general people will tend to get what they pay for. The trouble is as I see it is expectations and that can be difficult when some one asks what machine and in my experience people are likely to take no notice as they feel that if there were any problems it wouldn't be sold. The one I mentioned isn't my only instance. Maybe they live on planet zod but in some big boys toys area some retailers take advantage of peoples naivety. Actually I feel lathes and machine tools are no where near as bad as some other areas.

If some one relates the above to much heavier lathes please go lie on a motorway and play with the traffic. Thw weight aspetc at some point will come into it. Perhaps I have managed to explain why things like a baby lathe will have limitations.

John

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I've no idea what HSM is Bazyle

Over centre turning was explained to me during training. The actual effect is that the tool can take more of a shaving cut and in the extreme probably dates back to hand metal turning. In my experience it needs things to be pretty rigid and well located. As was suggested I have tried it with a parting off tool angled around 15 - 20 degrees so into the cut. That can only be used for rather shallow cuts. The actual tools that were used for this sort of thing are more like scrapers.

Boxford outline a less extreme form of the same thing. To be honest I have never tried it on my Boxford for lack of a suitable tool holder but it worked remarkably well on a Taig - very easy to get a tool bit over height. Not used during training either as we were expected to produce work which was smack on, tool ever so slightly below centre. It was just explained. One of the instructors saw a sign stating "Fine Turning" while on holiday and managed to persuade the person concerned to show him the tools and the machine he used. He also showed us what happens when a ball end spinning tool is ran along mild steel - that one is often explained in old books, LOL the surface of the ball broke down part way through the demo. It needs to have a mirror finish and be rathe very hard.

The negative aspect is that more front clearance is required and that cuts wont be what is set on the dial. The excess front clearance and the usual tool holder which will slope a tool at circa 10-15 degrees produces a very fine edge which will wear more quickly than a blunter one but if tools are stoned from time to time that doesn't really matter. The interesting aspect is that it's aimed at a better finish rather than tool life as per cutter angle tables.

Can't agree on Boxford's all over the place. A lot were used in schools and also in workshop type environments rather than tool rooms. Harrison's and Colchester are a lot more common in more advanced training establishments. Even some schools. The Boxford's I used at school were great machines in really good order. I've still got a wax crayon firing cannon I made on one of them some where. Very easy to get an excellent finish. I was talking to a college metal work lecturer yesterday. He reckoned I would be disgusted by what is taught today. The machines he uses are Colchesters that it turns out were made in Taiwan and assembled in the UK,

John

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Long time ago but vaguely remember that spilt mercury can be gathered up with a piece of aluminium.

A spill in a lab from a type of porosity measuring machine. I'm pretty sure it was aluminium that was used.

John

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Brian if you can't handle putting a Taig together I'm inclined to say, laughingly of course that you shouldn't go near any machine tool. As many people have pointed out your and other lathes are a bit of a casting kit. If so they can need a lot more work than a Taig does. My only reservation is the variable speed drive Taig's now have so it's a pity no one has commented because I suspect it will be the Sherline one or very similar. The other catch is the centre distance which a long bed Shereline would avoid.

On your steadies I doubt if the lathe is any different bed wise to any of the other common baby lathes. You could try a local order and send back if it doesn't fit. In the UK this would be taking an unfair advantage of the remote selling laws but sometime it can be the only thing to do. Just pick one that looks the same with the same centre height etc.

As to what to do Hopper is your best bet and I suspect a number of people would appreciate his views on the lathe before and after it's sorted out. This assumes it's not and electrical problem - it's hard to see why that would cause a finish problem. On cut depth I have heard similar comments from some one else. His opinion after some use was it's best used on plastics. This was one from Chester Machine Tools. I went up with him and said no not that one but later he did - weight the same as you. I suggested the usual mini lathe. This might surprise you but the salesman agreed with that too - pointing out that lots of people did do serious work with those. Not much choice really as I was looking as well and mentioned some things that I wouldn't accept on a lathe. That ruled out a lot of the ones they had for sale. Some of those problems may have disappeared since then. I honestly don't know but the baby lathe looks just the same.

John

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I've not used this but have heard reports that it's pretty good for machine painting. They do a number of colours, matt or gloss. Also spray cans. The reports were based on using a brush but I have no idea if it was diluted or used as it comes.

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Techaloid is still available and as far as I know remains unchanged. It's a synthetic coach paint. That does benefit from thinning when brushed on - as I mentioned. The correct thinners might dry more quickly.

David's post interested me as International Yacht Varnish is available and seem to brush well.

John

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Maybe some one fancies trying another way

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John

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