Member postings for Simon Williams 3

PS being able to sit at the side of your new table is essential!

edited for PS

Edited By Simon Williams 3 on 12/03/2023 20:37:14

Hi there, good evening.

If you weld anything worthy of the name to the underside of your 5 mm sheet you will pull the top plate out of shape. Even stitch welds will do this to some extent. Maybe this won't be a concern, but a nice flat table top will elude you.

I have a slightly smaller table with a 10 mm thick top welded to 50 mm sq box around the periphery, It's not too bad, but flat it ain't. I estimate it's crowned by about 1.5 mm. It was fabricated as a fly press table, so it's OK for what it was meant to be used for, I use it as a welding table but I have to keep away from the edges if I want to clamp anything to the top surface and keep it flat and square.

I would make a nice stiff frame and keep the top of the frame as flat as possible. Then I'd fix the top on with say M6 countersunk screws through right angled brackets on the 4 x 50 ribs.

A flat surface is a great deal more useful than a not quite flat surface...

Sounds as if someone has removed the control shaft to save furtling in the innards to make the Newton Tesla package compatible with the original switched control scheme.

I re-wired the control switch so it became the input controls to the VSD. Maybe this boat has sailed?

I've got a Bantam 2000; on this there are three shafts running along the front of the bed. The top one is the leadscrew, the middle one is a shaft with a keyway all along it, this operates the longitudinal and cross feeds. There is a third shaft of about 16 mm square section which is controlled by the forward/off/reverse lever located right hand side of the saddle.

How is the on/off function controlled on your Bantam? Any chance of a few pictures?

Many thanks to all the replies, we seem to have established that my reamer is a roughing one and it's no surprise that the chip clearance needs a whole lot more care. Good stuff and thank you.

To answer the question about its origins from David, this was a completely off-piste design albeit a loose copy of something I've seen in a picture. I've never seen one "in the flesh" as it were.

Here are the individual components:

The body "casting" is two tubes bronze welded together, so the "bite" out of the side of the bigger one sets the centre distance of the pinion against the rack. Otherwise the bits are fairly simple. I chose the pinion to be 15 teeth and DP20 as this makes a full turn very nearly 60 mm travel.

Just to pass the time between wishing the in-laws bah-humbug, I've been converting the tailstock of my S7 to be rack operated. Thus:

Excuse the paint job (lack thereof) - it is 70 years old.

Almost the last operation was to cut a no 2 morse taper socket in the inboard end of the new tailstock barrel. I drilled a 14 mm hole to clear out most of the material, then bored an undersize taper of very nearly the correct angle to make sure the socket would be true to the OD of the barrel. So far so good.

I then introduced my one and only MT2 reamer into the mix. I've tried to bore MT2 sockets before using the compound slide, but found it is very difficult to get a truly linearly tapered surface.

Here's a picture of the reamer. It's far from new, but I thought I'd give it a try.

As you can hopefully see it's the type with a solid MT2 shank, and with serrated flutes. I'd assumed this is to make it cut more freely.

I was surprised how quickly the gullets filled up with swarf. Am I expecting too much to use this as a metal removal tool rather than a shaping/smoothing/trimming tool? By the way the barrel material is EN32, so mild steel but with no free cutting properties worthy of the name.

It cut a successful socket, scored near the mouth which I took to be me being clumsy with my swarf management regime, but the taper size and fit are pretty good. For the amount I shall use it I'd call it a success. Shame I cut one of the rack teeth out of position (simple typo in my list of dial settings).

So I am planning to remake the barrel, but before I do I would appreciate some advice about how to cut an internal taper. My initial question - is this reamer a metal gross removal device - is one such, also what is the difference between this reamer and a straight flute hand held one with a square butt for use with a tap wrench? Why is one on a Morse taper shank and the other one hand-held? Do I need both?

Should I get much nearer the final socket dimensions before using the reamer?

Can I sharpen my serrated flute reamer by grinding the face of the flutes?

Any thoughts?

Thanks as ever

Simon

P.S. I'd rather not get involved in grinding the finished taper if I can avoid it, it will only be used for light occasional duties and I don't have the technology. By the same token I'm happy to leave it soft. The real imperative in remaking the barrel is that I mis-designed the anti-rotation slot to take the tang of a MT2 drill but my reworked barrel will have a tang slot and an ejector.

I've converted all of my machinery (except a bandsaw) from single phase to three phase with VFD, once you've appreciated how adaptable and controllable they are after the conversion it's total no brainer.

Drilling machine - instant adjustment of speed over at least 5:1 range (20 Hz to 100 Hz no problem). Can set the speed for a 3 mm pilot hole and then lower it to open the hole to 13 mm drill at the twist of a knob, no need for changing belts. Controlled soft start, DC braked stop (legal requirement in commercial usage in UK), and reversible with programmable ramp down/ramp up acceleration for tapping, left hand drills etc. No consideration of number of starts or capacitor life, no centrifugal switches to fail. Single phase motor can be reversed but you have to wait for it to come to a stop before applying power again. No such delay with VFD, the speed profile just follows the pre-programmed parameters.

Milling machine - all of the above plus wider speed range to take advantage of carbide tooling. Extend speed range downwards for face mill or side and face cutters, also as another tool in the box for controlling vibration. Switchable low speed range for set up (e.g. wiggler usage)

Geared Head Lathe - all of the above, particularly the soft start and braked stop (no the chuck doesn't screw on!) Being able to extend the speed range downwards is particularly good when working on large diameter faceplate work with the gap bed out.

Myford S7 lathe - can't have braked stop 'cos the chuck might come off, but otherwise the same as above. Also advantageous when metric threading (imperial leadscrew) to be able to program reverse speed (back to start) at twice or three times forward speed.

Try it, you're missing out!

PS (edited).  Motor start doesn't knock a ruddy great hole in the domestic mains, so SWMBO can keep watching Eastenders (spit!)

Bump DOL reverse start with a screwed on chuck is asking for trouble, whereas programmable soft start with VFD solves this problem.

Edited By Simon Williams 3 on 20/01/2023 22:49:03

If a light load on the quill helps, how about changing the quill bearings to be the -2RS style with double rubber seals, lubricated for life. These usually have a bit of passive resistance as a consequence of the seal.

Unless it uses angular contacts of course. Fairly sure mine is standard single row ball bearings, though it is some time since I had it apart.

Mine is the earlier version with a single keyway rather than a spline. It does rattle rather with a face mill but it hasn't failed yet.

Splat of heavy grease down the splines?

Forgive me if I'm being thick, but the cardboard template with three holes is mimicing the stationery part, you need a piece of card with two holes the same as the two in the selector lever hub. The the one with two holes slides over the (stationery) one with three holes.

There's got to be three unique positions of the detents else it would never have worked from new. The stuff about a detent covering half a hole doesn't make sense.

Have you dismantled the selector cross rods and forks to check that there isn't a flat or a hole that's smeared and is sticking but moving erratically?

Keep us posted, do

Rgds Simon

Whoa up chaps

Original description stated that the lathe has been operating successfully for 20 years. Then suddenly we have a wandering gear selector. This isn't a manufacturing fault it's wear and tear.

Don't go modifying anything just yet, there's something as yet unexplained.

Rgds Simon

In a previous galaxy, far far away, I found myself drilling second hand Morris Minor rear springs for a centre bolt. I was cutting them down in length to make trailer springs for a range of two axle trailers I made for a while. I wanted an 8 mm hole but found I couldn't drill this in one take, I needed a pilot hole because I couldn't put enough pressure on an 8 mm drill to keep it cutting. I don't know the exact metallurgical provenance of Mr Morris' spring steel, but it was tough stuff. Ford Transit springs were even tougher - I couldn't drill those.

I found that a 3 mm pilot was too fragile and the drill snapped, a 5 mm drill was a little on the large size and I couldn't reliably keep it cutting but a 4.5 mm drill was a good compromise whilst leaving enough meat for the following 8 mm drill to cut through without grabbing. If you let the drill skate then you might as well throw that leaf away - this was before the days of carbide drills as we now know them. I did experiment a bit (no pun intended!) with re-shaped masonry drills, but it was more trouble than it was worth.

Drills needed to be sharp, with not too much front clearance - hand ground was perfectly adequate. I doubt if the drills were anything other than bog standard Dormer jobber drills. They had a hard life! They needed to be run really slowly and with water or soluble oil coolant with as much down pressure as you dared.

But the moral of the story is that drilling hardened or hardenable steels is about enough pressure on the drill to keep it cutting.

FWIW I think 01 tool steel is lovely stuff to work with!

Seasons greetings

Simon

Dunno if it helps, but I happen to have a 48DP no 2 cutter, but for 14-1/2 PA. If it is any use to you and you would like to borrow it send me a PM.

Question for the group - is it asking for trouble to run a gear cut for 20PA against one for 14-1/2 in this application? I note the OP doesn't say which PA the pair gear is, but it becomes 20 deg as the discussion progresses.

You're welcome to try it and see if it looks right.

You might like to take a look at Tom Lipton with much the same question - though not quite as severe.

Try Youtube link here

He makes the point that the gripping efficiency of an Albrecht chuck is a compromise between a bit of lubrication to get the tightening to work, but too much lubrication stops the friction necessary to hold the drill securely. He also details how to get the thing to bits and what to expect to find inside.

Good luck

Simon

Taking the 13A FLC @ 230 volts mains at face value for the time being, then motor start inrush current for a single phase induction motor is about 8 - 9 times the FLC. Hopefully it starts readily, gets up to speed in a few hundred milliseconds, whereafter the mains wiring can start cooling down again. But it takes a socking great clump out of the mains as it starts, so upstream (source) resistance is the limiting factor controlling the inrush current more than the electrical characteristics of the motor. If the upstream resistance is sufficient to droop the supply voltage significantly (spec' is 10% droop - dream on!) then the motor will struggle to spin up, may just churn taking oodles of current or even refuse to turn at all. This is why single phase motors on a petrol generator are so problematic.

Also assumes the compressor is low inertia (no gert flywheel) and is unloaded throughout the start run-up - i.e. not making air, or discharging into an empty pipe. If neither is true then double the estimate (but it shouldn't be on a 13A plug). Also assumes it's a reciprocating compressor.

I couldn't find a definitive answer to the question whether 13A FLC for 2.2 KW is reasonable - my gut feeling is it's a bit low. 2.2 KW into a resistive load would draw 2200/230 = 9.6 amps, but you need to allow for the power factor of the motor (horrible - likely below 0.7 for a single phase motor) and also its mechanical efficiency (estimate 80%) so best guess of FLC is 9.6/0.7/0.8 = 17 amps.. But if you've got a rating plate that says otherwise I'll bow to this superior knowledge.

HTH Simon

PS To answer the actual question, motor equivalent resistance at start up on perfect 230 volts supply is 230/13/8 = 2.2 ohms. Add on estimated supply resistance (this should come from supply company) of say 0.4 ohms, now load resistance is 2.6 ohms. Current is thus 230/2.6 = 90 amps but only for motor inrush.of say 0.2 seconds.

(We likely needed to bring the answer under 100 amps else the supply company will have a fit).

ATB Simon

...and I get to learn something I didn't know I didn't know. Win - win.

I'd guess you're looking for minor corrosion or sticky grease in the horizontal slots on the side of each jaw, and the gooey bit may be out of sight. Try sousing it with a mixture of paraffin and thin oil and rubbing the jaw in and out with the scroll removed. Acetone and ATF oil makes a good penetrant. Don't be tempted to get the emery cloth out, though oily scotchbrite might help.

You probably only need a few tenths of a thou' irregularity to cause each jaw to catch.

HTH Simon

E Stop function requires a second (confirming) action to achieve reset, so the machine can't restart as soon as the latching estop button is released. So you need a dedicated estop relay which drops out when the estop is pressed.

Now imagine you can only re-energise that relay if the spindle control lever is in the central "off" position. Hopefully the micro switches it operates include normally closed contacts which can be wired in series into the reset path of the estop relay. I think you'll find this function is built into the original control circuitry as manufactured.

BTW I don't believe the estop relay needs to be a safety relay, a simple control relay will suffice.

HTH Simon

Does anyone do an occasional hydraulic test for the sake of safety, peace of mind etc?

I'm thinking of the style where you fill the tank brim full of water then pressurise to (say) 1.5 x max working pressure. Ought to test the operation of the pressure relief valve at the same time.

Properly such activities are pre-planned and set out in the Written Scheme of Examination.

Any takers?

If possible stay away from motor oils, which have detergent additives to keep the innards of the engine clean. Compressors are prone to condensation particularly if they only run for short periods, so mixing condensation with detergent and oil gives a lovely brown frothy custard.

FWIW

Simon