Member postings for Ajohnw

I found a bit of information - posted here

**LINK**

Kerosene ignites when vaporised so I doubt if any one uses that on a tool grinder. Suds I would have thought but I believe there are specialised liquids about for surface grinding etc.

John

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There is some stunning work done on all mini lathes of all makes. In some cases it would pay people to fit a polishing mop to one end of their off hand grinder to improve on file and emery cloth work. Not that I;m being cynical of course. Actually a supplier told me how surprised he was by some of the results people get but then he wouldn't be aware of what people do. Neil posted a thread showing some extreme work done on one but he has also remachined some of the bits.

I'd strongly advise people not to get sucked into the .de aspect. On the other hand they do point out that the bed castings for one of their larger hobby lathes are aged for 6 months before grinding etc but I understand traditional lathe manufacturers leave them lying around for a lot longer than that. I wonder if 6 months is sufficient to really achieve anything useful.

The steel cutting problems are probably down to general rigidity - Brian wanting a very light weight lathe. Too light in my view.

John

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There is a big and not that unusual comment on the SPG's page - reserve the right to change without notice. I sometimes wonder if they phone china and say what have you got cheap at the moment. Joke but why don't sites like that keep their web pages up to date.

I'd 2nd Bazyle's comment about inverter drive. Also note that min speed on the SPG is 80 rpm. It probably has a brushed dc motor and driver built into it. Others will be brushless which shouldn't do anything with torque unless the motor hp is increased but probably does give better speed control at low speeds. The larger spindle bore on the SPG is an improvement and they have even knocked the top speed down bit to account for increased bearing size. The spg has a 3morse tail stock allowing bigger drills and reamers to be fitted. If you read the thread I posted a link to you should note that sometimes rather wild claims are made about motor power.

The details on the warco suggest it has a low speed pulley setting which I feel is a good idea.

In respect to the size of the spg lathe I suspect I would be seriously considering this one

**LINK**

That one is out of the hobby lathe range. In fact I decided some time ago that if I ever changed from my boxford it would be to one of these or a similar model. Being a gear head it should have adequate power for a lathe of this size - rather a lot more than the variable speed ones. I'd also expect it to be up to industrial standards but don't know if it is. This one would have the torque to handle things like 3 morse drills. I have my doubts about the SPG one. Being able to hold a big drill is one thing, having the power there to use it is another. Even the gear head would probably have to get up there in steps.

John

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Edited By John W1 on 30/10/2015 11:42:18

The main problem is machining them in place on the lathe. If your lathe is turning a taper or some other strange shape due to spindle alignment etc you will finish up with bell mouthed jaws. Apart from that aspect they can hold work rather accurately.

I wouldn't entirely agree with Jason's comment. In use the jaws are under compression and even if they aren't tapered down at the end to hold low diameter works there will always be a degree of point contact when holding round work. The only sliding wear they may get is when your putting work in them. The scrolls on the back will wear more quickly than hardened jaws and that is the main reason for hardening them. This is why hardened soft jaw carriers are available for some chucks.

I've seen mention of machining or grinding ordinary jaws in various mags over the years. The jaws are just dangling in space = nvg. They need to be clamped on something for the best results. One way of doing that is to machine a shallow recess at the back of the jaws, say 1/16" x 1/16". Then grip a washer or what ever in that while pulling the washer back against the shoulder. Then machine the inside of the jaws going as close as you can to the washer. Remove the washers and take off the slight shoulder that is left.

If your jaws are worn you'll probably find that the ways in the chuck are too. When ever I have bought soft jaws I've found that they need fitting to the chuck and suspect they are deliberately made a bit over size to account for wear in the chuck. The slot in the jaws is usually a touch to narrow and the front width of the jaw past that a little too wide. I've just used a set of warding files to correct that being very careful to identify which part is fouling on the chuck body. I find it easier to keep the file still and move the jaw as that way I can feel when the surface being worked is square to the file.

Harold's idea of using them as carriers for other jaws is interesting. I'd wonder about annealing a set of soft jaws, doing what work is needed and then case hardening them. The mess on them after case hardening could be cleaned off with emery cloth with virtually zero change in size.

John

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The main problem with sharpening HSS on a green grit wheel assuming that it is one intended for use on carbide is that it will glaze fairly quickly and then cut more slowly and generate more heat unless its' regularly dressed. As it's intended for carbide which is a harder material than HSS it's less friable. A more friable wheel tends to cut more cleanly so like most things it's a balancing act what ever the material being ground is or the type of grit in the wheel. The more friable a wheel is the quicker it wears away. The less friable it is the more often it needs dressing to expose fresh sharp grit. The ideal degree varies according to the material that is being ground.

Oh how I wish I could remember the grade and hardness of the silicone carbide wheels I used during training. All I know is that it was more friable than what would normally be used for grinding hss tools in a tool room. Done to save having to regularly dress the wheel as rather a lot of tools were sharpened on it, White aluminium oxide only seemed to be used on tool grinders - sharpening milling cutters and re sizing reamers etc with very light cuts.

This highlights an interesting aspect of friable diamond wheel - correct for carbide or for HSS. I'd guess correct of carbide.

John

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There is one other useful feature on that warco lathe - the ability to change the feed rate without messing about with change wheels. I've no idea what the range is but if done sensibly it can be very useful. Sometimes the finest feed available doesn't give the best finish and a faster feed can often be used for roughing things out anyway.

Personally I would also stress the screw cutting indicator especially if it will cope with a range of metric pitches. While these can be done by reversing the lathe at the end of a cut to get back to the start again the indicators do allow the work to be done a lot more quickly and are a lot more convenient anyway when working up to shoulders etc. It's even possible to use them for that on pitches where the lathe has to be reversed.

John

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I'd expect them to machinists files as per this that comes up when the term is googled

Warding files are machinist's files and are frequently used by locksmiths. They are named after the shaped openings in keyholes that act as a barrier to lock picking, as they are used to both deburr and repair them. They can also be used to file the notches in a key that allow it to fit into the warding.

I've bought them from tool shops often enough and would expect any particular shape of file, rather a set with circa 100mm blades plus handle that includes at least a flat blade with 1 or 2 safe edges, 1/2 round, round, 3 square, square. The actual file length including handle is likely to be around 150mm or more.

The last set I bought are described as miniature files Including a warding file - just to add to the confusion - with one safe edge or maybe that's the tapered flat one with no safe edge. Bought because my previous set are a bit long in the tooth now.

**LINK**

John

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Edited By John W1 on 29/10/2015 16:35:53

Ok Tom has chosen a lathe. What I would like to add is the next question is where to buy it or similar from. Versions vary

This one for instance and others in similar ranges have a screw cutting indicator - even on the metric version or so the page suggests. I'd check.

**LINK**

It also has a conventional AC motor and inverter fitted as supplied. I" bore too.

For some reason screw cutting indicators are often lacking on this general range of machines especially on metric ones. Odd as it can be done and saves reversing the lathe at the end of each screw cutting cut. Some come with 2 gears to fit to the indicator to allow more pitches to be cut like this.

Is the axminster one better or this one better than that. Pass. The only way to find out is to use one.

No more comments from me. I'm away for a while.

John

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Edited By John W1 on 26/10/2015 10:35:41

Noise out of Transwave 240 to 440 3 phase passive converter ?????????????? Set incorrectly and the motor stalls and there will be some noise.

Noise out a motor driven by an inverter - yes. They tend to be noisier than driven via 3 phase due to the switching frequency used to drive them.

John

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I used a Transwave box for a couple of years without any problems providing i set it as they instructed. If I played with the settings more out of curiosity all seemed ok but from time to time things didn't work out so eventually I just set it up as instructed and didn't have any problems at all. One thing I will add to that. When these were popular many would buy a 3hp unit or even bigger as they can be turned down via the knobs. I just went for one that was more than adequate for the motor it needed to run. Transwave will advise you about the suds pump.

Some people set up a motor converter that uses a generator and get 440v 3 phase that way. I know nothing about these.

I think I have read about a method that use capacitors and more than one motor. Might be details on the web.

Sometimes 3 phase 440v is available and close to the house and just not wired so can be installed but I have no idea of the costs. Houses are just wired off one of the phases so a lot depends on how the meter etc was initially installed. In older properties in B'ham I have been told that getting at it is often relatively easy. Good job too if in the future we have to heat our houses entirely via electricity.

John

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Edited By John W1 on 25/10/2015 20:38:09

You've reported that you can rock it / move the saddle around in the past Brian so what has changed ?

John

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That link is a fantastic example of not understanding the process of using emery cloth on a lathe.

A little trick that can be tried to see why. A very high class finish is required with say the same accuracy as boring. Fix some emery cloth to a boring bar so it's firmly in contact and well aligned with the bore and use it just as you would a boring bar but with extremely light cuts. 2 things become apparent. The cloth wears out very rapidly due to more or less point contact along a line and it will also clog up. The same thing can be done to external diameters.

Curiously extremely coarse emery cloth tends to be more effective as it forms a multi point cutting tool in the same fashion as a grinding wheel does. One supplier of the stuff looked into producing a sort of cassette so that "new cutting points" could be obtained at the press of a button.

John

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Edited By John W1 on 25/10/2015 16:19:14

Edited By John W1 on 25/10/2015 16:19:40

It may well be worth telling us which way the saddle rocks when the plate isn't attached Brian. Push down firmly over the V in the centre and see if it rocks in any direction.

As Jason pointed out and I expanded on a little there shouldn't be any need for the plate to be firmly up against the bed - other than if for some reason the basic design is screwed up.

It might be that the saddle will move across the bed when the side on the flat is pressed down. Have a fiddle about with that sort of thing and tell us what happens. Pressing down an various places and checking for any sort of rock/movement across the bed elsewhere. The V and the flat need to mate at the same time when it's on the bed so if the flat is too high, the V too wide etc it will move about in directions other than along the bed.

John

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Edited By John W1 on 25/10/2015 15:35:41

Edited By John W1 on 25/10/2015 15:36:57

Edited By John W1 on 25/10/2015 15:47:22

From what I can find out the drive circuitry is effectively replacing a commutator which means the coils driven by this need to be stationary. The switching frequency controls speed and phase will set direction. A simple view.

I did try playing around with a relatively low rpm per volt model aircraft motor and driver but didn't stick a scope on it to see what was going on. I found that the speed regulation didn't seem to be too good but suspect that was the controller. I had wondered about using one to drive a tool post spindle powered by a redundant power supply intended for use on a server. There is info on getting some of these to run out if a server - some pins have to be shorted etc. One problem is the size of leads needed as the power goes up.

There is plenty of info on the web such as

**LINK**

I'd guess there will be info on using an arduino to do the basic drive about as well.

John

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I missed the slight wear marks at the edges.

Gibs of any sort that use screw arrangements like that are always a pain to set but once set the cap screws should lock it all up so they should stay set.

Some people reckon that the underside gibs are added so that things can be milled on the lathe. They just prevent the saddle from lifting. I'm not so sure. A lot depends on how the cutting forces are transferred to the V and flat. There is often one on the back to stop that end from lifting but as you point out these generally don't need to be tight. The whole idea of a prismatic bed is that cutting forces push the saddle hard down on the V so it should remain in place. The fact that it's a V can also mean that there is a decent contact area to resist wear.

If the V in the saddle isn't straight/flat and has a slight bow it will rock. Past that problem pass but bed width to centre height of the lathe also has some bearing on it. I'm not convinced this is down to science more down what has been found to work. The lead screw might not be straight either which could also cause the saddle to rock in use..

Perhaps Brian's rock is side to side due to a warped saddle or front to back because when the V in the saddle is in firm contact the flat isn't.

Some one wouldn't see me trying to fix that with a scraper despite all of the hype, I'd use a file.

John

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I've mentioned slideway oil before Brian. It will help. I can't search ebay oz for some reason but there may be 1l available on there. 5l is available from several sources in oz. A bit too large a quantity for you. There maybe some one who supplies smaller amounts.

John

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It's not that simple a thing for them to do Brian. You have milled ways. To improve that they would have to grind them. They could also improve the milling by doing it more slowly. Both would increase cost and in these days things being sold on the basis of there being a market for items at a certain price doing so would upset the apple cart.

I suspect you would find more or less the same on all hobby lathes.

It looks to me like the plate doesn't actually run on the underside of the rails - just the grub screw tips. Am I correct? In that case the finish on underside of the rails is what matters. The bed is ground so it shouldn't be too much of a problem for them to grind those as the facility to do that would be on any slide way grinder.

John

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Edited By John W1 on 25/10/2015 12:23:50

Maybe the Brian's lathe problems in another thread are down to China working to German quality standards then Alan.

My own collet chuck problems are similar - didn't realise that the aspect that is wrong matters or maybe just couldn't be bothered.

Japan was a touch different. All exports were checked to meet certain standards and they managed to produce goods with all round acceptable performance at much lower cost than the west. Many bits had a "quality" sticker on them - reassuring if nothing else. Factually they were generally inferior products to what the west produced but at 1/2 or under the price and able do what ever it was meant to do, well that sort of thing always wins in the end. They also most definitely dumped to gain market share. They also propped up the USD for a long time. China's foreign reserves seem to be falling rapidly but it's hard to find out how many USD they actually have. At one point getting rid of them would have cause the USA a lot of problems.

Taiwan deserves some comparisons with China too. The same thing will probably happen to China eventually but given rather a lot of them and communism - rule by technocrats - it could be a very very long time coming. Possibly never.

John

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Mounting it on a lathe isn't a sensible way of testing it Dusty. That's why I set a myford spindle up in a V block. This removes any lathe spindle errors. There is too much test bar run out tested like that. And way way to much 50mm from the collet face.

I could check the taper run out in the V block but would have to be very careful not to allow any side to side movement so see that as a none starter.

There is no run out on the test bar or the myford spindle. Both can be checked in the V block and have been.

I then reversed things and mounted the test bar on the V block and checked the collet holder register for run out. Very little which could be down to either or both the collet or holder. Doesn't matter which. It's acceptable anyway.

The only explanation for this and the other measurements and tests is that the screw thread in the holder is off centre. This forces the collet holder to be off centre - any clearance between the registers is pushed over one way.

I've effectively ruled out significant problems with the test bar or collet.

I'm sleeping on sending it back for a replacement. The problem suggests that it's down to the way it's been made. Some effort has been clearly taken to align the register and collet taper but not sufficient on getting the thread central. This also explains why register sizes that should go in don't. The thread pushes the nose over as it's screwed in. The options are a refund or machine away the offending bits which would have to include the register even though it's ok and fit an insert that would be made in one setting - that hasn't been done on the thread in it otherwise it wouldn't have this problem. The problem - in some ways it would be easier to make one from scratch as the collet taper would be machined while it was on the spindle.

John

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The saddle drawing in the manual doesn't make much sense.

I assume 202 going in from the top is for locking the saddle. The other 202 and 220 look like a very crude sort of push pull arrangement. It only makes sense if 220 is used to alter the angle of the plate and both 202's are used to set the fit. The plate doesn't seem to be supported at the other end which is rather odd but there is signs of a hole.

Maybe a photo from underneath might help.

I suspect it will show that some bits have been dropped from the design.

John

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