Member postings for Andrew Johnston

I've always cut my gears using conventional milling. Bit ironic really as my horizontal mill is the only one with a backlash compensator; and it's the only one I haven't used for climb milling. Something to do with if all goes pear-shaped the mill isn't going to stall, it'll just plough on and cause damage.

Gear shaping, as used commercially, is by definition a sort of conventional process.

Looking at videos of commercial hobbing some climb mill, but most don't. So it probably depends upon the manufacturer and/or user.

Andrew

Very possibly, but not in this case. Commercial suppliers quote the same physical properties for cold drawn and hot rolled EN24T. Presumably this is because the hardening and tempering is done after drawing/rolling. So any properties imparted by the drawing process are reset during heat treatment.

Andrew

The basic problem probably is the mill. But using poor cutters (not the one from Arc) certainly won't help matters. Small machine tools need all the help they can get, including quality cutters properly ground.

If the gibs are proper tapered ones, they don't have locking screws, just adjustment screws at each end. Presumably the gibs are parallelograms rather than proper tapered gibs?

Andrew

Given both are EN24T it doesn't matter if they're cold drawn or hot rolled. In theory the cold drawn will have internal stresses. But on the assumption that the material is hardened and tempered after drawing that won't be the case.

The question of mill scale isn't really an issue. One, when cutting a spur gear the cutter normally approaches the OD from within the material. So it never has to cut the scale. Two, hot rolled is unlikely to be to size, or even round, so the OD will need to be machined first anyway.

Andrew

Nevertheless, the boys at Britan clearly didn't know what they were doing. My repetition lathe has a two speed motor and it doesn't do star/delta switching, so it's only 750W/375W. Even worse than that it's about the same footprint as a Myford but weighs 750kg. Of course that includes the stand and auxiliary motor along with coolant and hydraulic pumps, and an air compressor. But there must still be a lot of surplus cast iron.

Andrew

Otherwise known as a drum. Just because something uses less metal doesn't mean it's automatically better; cheaper yes, but not always better. Sheet steel cabinets are notorious for vibrating. They often need stiffening to avoid the problem, which can feed back into a poorer surface finish.

Andrew

The energy stored in a flywheel is proportional to the mass of the rim and to the square of the velocity at the mean radius of the rim. So, for a given angular velocity, reducing the diameter of the flywheel has a disproportionate effect on the stored energy and is the worst thing you can do. Follow the drawings and buy the correct diameter stock.

Andrew

Edited By Andrew Johnston on 07/10/2019 19:11:58

Yep, being using them for years, mainly to fit multi-pin automotive connectors. The main advantage is that the holes doesn't need to be pre-threaded but can be as moulded. Optimum number of lobes is five, but three will do.

Andrew

Speed seems ok, if a little slow. But the feed is way down, especially for inserts. The obvious question is where did the inserts come from? I don't have any Glanze mills, but i have a couple of their boring bars. The bars are ok, but the supplied inserts went straight in the bin.

Personally I'd bin the insert cutter and just use a plain carbide endmill.

Andrew

I don't recall milling EN16, but I've just made the drive pins for my traction engines from EN16T bar and it turned with no problem, albeit using insert tooling. But I drilled and tapped 5/16" BSF holes using HSS tooling with no issues. I certainly wouldn't worry about milling EN16. If the OP has a problem then I'd suggest it's either with the cutters (which manufacturer) or speeds and feeds.

Andrew

Of course I'm biased, as I'm building from the LSM imperial drawings. My castings are from elsewhere and follow the original Filby design in some areas, so the LSM drawings are not appropriate. There are a number of show stopping errors, and a lot of missing detail, in the LSM imperial drawings. I'd be surprised if they had been corrected in the metric versions.

As I mentioned to Karl yesterday at the Forncett exhibition day one area that has gone metric is sheet and plate. So 1/4" plate for the hornplates is simply not available. I used 6mm plate which necessitated changing the dimensions of some other parts. However in other areas the situation is more complicated. I've just looked at the rear axle material, specified as EN8 and 1-5/8" diameter. Looking at my local steel stockholder 1-5/8" is no longer available for order. Both 1-1/2" and 1-3/4" are available and in stock. The metric equivalent is 41.275mm. The nearest listed is 42mm, but this is not available for order. The only size that can be ordered is 45mm, which is on 14 days.

An interesting question is what have LSM done with the gears. The DP values do not correspond exactly with standard module sizes. So changing to module would require some significant changes to centre to centre distances, which has a number of knock on effects. Similarly have they made new patterns for castings, or are the castings still based on the imperial design?

When I started I planned to change all threads to metric. Internally I used a number of metric, mainly M6, SHCS and will continue to do so. But externally they just don't look right, so I've reverted to BSF and BA. Since I'm making most of my own bolts, studs and nuts, availability of off the shelf items isn't important. Nor is the availablility of the correct hex AF stock, as I use sizes that correspond with the hex collets I have available rather than what is nominally correct.

My lathe is imperial and both manual mills are metric. Generally this is not a problem either way. However, as NDIY says the main issue is metric screwcutting on an imperial lathe. I tend to screwcut a lot of my threads, a number of which are specials. The imperial drawings call out a number of BSP and 32 & 40tpi ME threads for which there are no direct metric equivalents. Before anyone points it out I know that there are ISO pipe thread standards, but they're based on the BSP system. So for 3/8" BSP you'll still need to be able to cut a 19 tpi thread.

Andrew

I wouldn't buy one. One, the vendor is not a supplier I use anymore. Two, I don't see how the collet grips anything. Sure, at end nearest the taper, the collet will grip. But as you move away from the taper there's nothing compressing the collet fingers and making them grip. I'd imagine that a 25mm endmill would work loose in a very short time with any sort of cut.

Andrew

Oh my word; eighths and sixteenths in decimal should be instant recall!

I still use 64ths, albeit not explicitly. If I'm machining a spigot that is, say, 3/8th long I'll hold a rule on the toolpost on the first pass and knock off the feed just before 3/8". The I'll turn the spigot to the correct diameter and finally take thin cuts off the shoulder. After each thin cut I put the rule on the work, resting against the shoulder, and if the end of the spigot is within a lines width of 3/8" on the rule that's good enough. If better accuracy is needed I'll dig out the depth micrometer.

Andrew

Simply converting imperial dimensions to metric isn't really going metric. To do so properly one needs to convert part sizes to use readily available metric sections. Are you really going to machine an axle to 9.525mm over its length rather than use 10mm stock?

Andrew

Hand reamers have a long taper on the flutes, so full diameter is only reached once a third or more down the length. The taper is intended to allow easy starting by hand. Hence the square on the end for a tap wrench. Machine reamers cut on the very short chamfer at the end and as the name suggests are intended to be used in a machine, ideally a lathe or mill.

I never use hand reamers, only machine reamers in the lathe or mill. I wouldn't bother using them in a pillar drill. If a hole is important enough to be reamed it's most likely important enough to be properly located and drilled before reaming using a vertical mill. A hand reamer will not ream a blind hole. A general rule for machine reamers is half the speed and twice the feed of the preceding drill.

Andrew

Can't say I've ever heard that?

The term lithium battery covers a multitude of sins. Primary lithium batteries have a fully charged voltage of 3.7V. On the other hand lithium-ion and lithium-polymer secondary cells have a fully charged voltage of 4.2V. If you charge them to a voltage of 3.7V they aren't fully charged. To complicate it even further LiFePO4 batteries have a fully charged voltage of around 3.8V.

Andrew

I expect the third terminal is for temperature measurement, usually a thermistor embedded in the battery pack.

I'd be very surprised if there was any charge balancing in the simple series packs used in power tools. I've designed a number of battery management systems that include both passive and active charge balancing. But it's expensive to provide and the algorithms required are non-trivial. The systems I designed were for electric vehicles where rapid charge and discharge cycles of several hundred amps are common. For a hybrid vehicle you don't actually want the battery full charged. If it is, then it cannot accept any energy from regen braking without over-volting the battery.

Andrew

The datasheet I found for the TPA4056 was less than informative, but not charging batteries below 2.9V is not how I read it. A Linear Tech device that I have used, the LTC4002, has a trickle charge threshold of nominally 2.9V. So below a battery voltage of 2.9V it will be constant current at the trickle rate and above 2.9V it will be constant current at full current. The LT datasheet doesn't give a minimum battery voltage, but it will certainly recover batteries that are below 2.9V.

Andrew

I wouldn't buy a main lathe that wasn't gap bed. But neither would I buy one that simply had a gap; it has to be a removable gap piece for me. On a well designed lathe a gap shouldn't materially affect the rigidity. One of the problems on lathes with a permanent gap is that in order to allow the saddle to be near the chuck for ordinary turning the width in the gap for the workpiece once a faceplate is fitted can be minimal.

Another point to note is that some of the import lathes with gap pieces do not gaurantee the turning accuracy of the lathe once the gap has been removed and refitted.

I am building a traction engine, so the gap bed does come in useful:

But it also comes in handy for smaller parts that need involved setups, meaning that the diddy faceplate cannot be used:

Andrew

An interersting question is how many contacts are there on the charger connector? Is the charger dumb, just voltage and possibly a thermistor for over-temperature. Or are there processors involved with serial comms. If the latter one might have hoped that the software would have refused to allow the charger to do anything damaging.

Andrew