Member postings for Martin of Wick

Couldn't say for sure.

In theory it should, assuming your early model has the 3/4 inch leadscrew (my opinions not to be trusted on early S7s as you have discovered!). I have a late PXF version of the S7 and the saddle looks quite different (although the fitting dimensions to the bed must be the same, albeit with the middle bearing surface cut back for clearance).

Not quite sure what you would gain unless the current saddle is in poor condition, (or you don't have access to a mill or second lathe to trim back inner bearing surface, which is usually the problem for most of us!).

Perhaps somebody can chip in if they have gone down the saddle replacement route?

I would suggest that you acquire a micrometer(s) a piece of paper and a pencil and take some defined and detailed measurements of shear width and depth over the bed ( tablet and spreadsheet will do if you are a young whipper-snapper). This will accurately map the location and amount of wear and give you a good idea if the wide guide fix will work. You could also measure the gap between the back of the rear shear and rear saddle bearing surface with the saddle set up in the usual arrangement towards the back of the lathe. Feeler gauges may help here.

You may then be able to find / fabricate a suitable piece of steel to that thickness plus about 0.020 thou and epoxy it to the saddle back bearing surface. This will pull the middle bearing surface away from the front shear enough to avoid binding. This particular kludge depends on there being enough slop, flop and fitting clearance on the apron fitting and leadscrew clasps. clearly if you go too thick on the stick on plate, you may lose leadscrew/clasp nut clearance. This method avoids having to cut back the middle bearing on the saddle.

Disclaimer - I have only read about those claiming to use this approach second hand, so cant guarantee success.

Sorry you are quite right, if it says S7 then it is. The early S7 apparently had the same poor saddle design as the ML7. Change to the rear shear bearing on the S7 was only implemented in 1972 (I thought it was earlier for some reason, but just checked on lathes.co).

BTW the saddle design suggests your lathe is an ML7 not a Super7

Don't think you have missed anything, the shears are worn at the headstock end, most of the wear will be on the front shear. The narrow guide myford is a poor design which is why the later models  use the outer edges of bed shears as the saddle bearing surfaces.

The front shear is mainly used on the narrow guide design and this is subject to most of the wear, not helped by the short bearing surface of the middle of the saddle which allows the saddle to rock. As most of the work is usually done close to the headstock, the front shear inner and outer edges wear most in that area over time. This is confirmed by your visual -Scraping marks are present on the inner edge of the front way from the tailstock to midway along toward the headstock, and then fade

Unfortunately, your lathe exhibits the most common problem with that class of machine. Not a lot of wear visually observed is more than enough to cause this problem. Effectively your front shear tapers down towards the headstock.

If you cant live with the problem and adjust the saddle fit to suit the job you are doing, then you options are

• You can get the bed and saddle reground if you can find anyone still capable of doing it and you have deep pockets
• You can do the standard documented wide guide modification which uses the outside of the back shear
• Some people have claimed that they have scaped/filed/ground the shear edges, but I wouldn't recommend it

Should also add, that if the bed is significantly worn, the shears can also be thinned on the z axis towards the chuck, so you will need to check the thickness of  front and back of each shear chuck to tail every 30mm along the bed. If this is the case, the wide guide mod may not solve the problem.

Edited By Martin of Wick on 16/12/2021 20:40:47

Edited By Martin of Wick on 16/12/2021 20:48:09

Edited By Martin of Wick on 16/12/2021 20:56:24

Hmm... yes accepted, there are brands and brands and Seig is probably upper quartile. Indeed, the article makes the point that some suppliers play a bit of a game with the numbers.

Most of what I end up with is very much from the other end of the quality spectrum to bottom of barrel stuff, so I have reasons to be cautious!

As stated, heat treating PLA (referred to colloquially as 'annealing' will both:

1. significantly strengthen the PLA part
2. make it temperature stable up to about 120c (ie as good as ABS)

But it needs to be done relatively carefully to avoid warping or distorting the part. I use one of the small consumer bench top ovens that I removed the top element from. I also recalibrated the temp control using a temperature probe on the middle shelf (ie where the item to be heat treated is placed) to have a more accurate indication of actual part temperature.

The best results I found are obtained by bringing the part up to to 60c, 80c, then 100c in one hour for each stage, and then back down in one hour stages. There can be very slight shrinkage on X and Y axis that may affect larger parts.

I would like to be able to rig up some sort of programmed PID control to do avoid having to do the settings manually but haven't been able to figure it out!

If you go down the same route, try to get a circulating oven if they make them - the internal temperature will be much more even.

Is it true all induction motors are really rated on their output power? If so then I have learned something new.

I say this because I have come across ancient* 1/4 hp motors that subjectively appear to be able to deliver as much turning force as some modern 1/2 hp motors (although I have never been able to precisely measure this to confirm). I did query once with a motor man who reckoned that older motors tended to be quite significantly under-rated on the plate with respect to expected duty, to ensure operational reliability.

What I do know from experience is that Chinese ratings appear to be for the absolute, full blown, maximum power dissipation the item will tolerate at the point of magic smoke release. Numbers are based on marketing rather than considering any actual duty. For reasonable operating, I usually assume 50% of stated values as indicative/safe power.

*ancient defined as circa 60 to 70 years old

I would go for half a horse min. I have a 350W induction motor on an equivalent lathe and it certainly doesn't feel over-powered. However it does feel substantially more powerful than the DC motor it replaced (that bogusly claimed 550W!).

If I didn't also have the 1HP Myford, I would probably up the drive unit to 500W.

Edited By Martin of Wick on 14/11/2021 20:37:41

For those with the cash, the NT solution will be simple, robust, safe and least faff.

If 'twere me, I would find a new 3 phase 350W or 500W motor circa £80 to £100 and a generic 750W VFD circa £50 to £70. A s/h motor would be OK, but you may have to search about to find the right one and they never seem that much cheaper than new.

If you do not feel completely confident/competent to wire up such power devices and make a simple control box to suit your purpose, I advise you to take the NT route.

Depending on motor speed selected, (ie. 2 or 4 pole) you may need to adjust the drive pully arrangements to suit your requirement.

PS -  avoid open frame motors if possible, sure they run cooler but they have a propensity to ingest swarf unless well protected

Edited By Martin of Wick on 14/11/2021 20:06:57

Hmm....

I urge caution using ONLY VFD for setting drilling speeds. Unless you have a fancy VFD with vector control, I find power drops off quite sharply below about 1/3 plated motor speed. So when you need the power for that large hole in some cast steel, 'taint there unless you have selected a decent ratio on the pulleys. And, if you are trying to extract torque in any quantity for a long period at low RPM, your motor will be sucking up a bunch of amps and getting toasty warm - best stop when you sense the acrid fumes!

On a lot of the older 'workshop' brit drilling machines, rated say at 3/4 or 1 inch capacity, it has always struck me that the lowest speed, seems scarily high, typically 400 to 600 RPM (it may be because I am wary of the nasty bite a drill is capable of if not careful). For example, my the lowest belt speed is 450 RPM which is deemed OK for 1" HSS drill speed for industrial Gradgrinds to suck their pound of flesh (quite literally I suspect) from man and machine.

BUT, I wouldn't want to attempt hole opening to 1" at that speed with a manually held vice however, using the VFD to give what for me would be a comfortable speed of 150 RPM, I could stall the motor. So ended up clamping down and doing the job in the safe way at about 300 RPM.

Neither, out of sheer laziness, would I rely on setting the mechanical speed  at 2000 RPM and just use the VFD to turn it down to an appropriate workpiece speed for the same reason. Always best to change belt position if you can.

For the average run of hole drilling from 1/8 to 1/2, I am quite happy to plod along at timorous speeds between 400 and 600 RPM more or less irrespective of material and would go much lower if |I could for larger holes.

I did explore the possibility fitting a 6 pole motor to reduce the available speeds on the Denford by about 1/3, although only 550w, it was a bit of a monster compared the original and considerable work to adapt, so it gathers dust for now.

Edited By Martin of Wick on 01/04/2021 16:15:07

| Kevin it is usually very easy to alter the connections in the motor terminal box,

....Yeah well maybe..... if you are lucky and the motor is configured that way. With older motors, I have found that they tend to have been designed for industrial use and be single voltage star connected without the facility for alternate connections in the junction box. If you want to re configure these type motors as delta you will have to dig around and find the star connection point in the windings - and even if you can get at that easily, you have to consider whether the wire grade used is suitable for higher currents (probably ok for a drill).

Like the OP, I acquired an old Denford, couldn't re-configure the 3P motor as the star point was not accessible without potential damage to an otherwise excellent motor and resorted to a cheap and nasty step up inverter (250 to 380v which works fine). Slightly scary as you have upwards of 380v floating about at the back of your drill, so need to use a bit of care when wiring up.

Choices for the OP...

It is probably quite a good motor so if you can reconfigure the old motor to delta easily, use a low cost 250v single to 3 phase inverter.

Otherwise if comfortable with higher voltages in your workshop, use a more expensive 250 to 380v inverter.

Otherwise, you can obtain imperial B56 frame motors from Newton Tesla (at a price).

Otherwise you are in the realm of searching on line markets, for S/H imperial single phase (usually split phase start windings with centrifugal switch) . Check specs and motor plate carefully!

or go down the route of adapting a cheap metric capacitor run motor (at 550w usually 80 frame size so 19mm shaft, but I did once see a 71 frame with a more convenient 14mm shaft).

Been longing for an excuse to get one of these  motors and have a tinker as a potential for the CML.

£75, 3 days out of Germany no handling or VAT to pay - go figure!

Findings:

Quite a neat unit with assorted fittings that may be adaptable for mounting etc

As usual, modest documentation, but there was a parameter sheet covering basic set up BUT.... with this example some parameters could not be altered as per sheet (up to 5000 RPM), in particular speed which is set up restricted to a max  of 3500 RPM, motor torque adjustment, braking, ramp speed etc. adjustable.

Fairly easy to set up and run out of the box. Low speed limited to 200 RPM, appears to have some very serious grunt at low RMP, but sincerely doubt if duty power is anywhere near 750W - like most RoC products claim probably represents maximum power at the point of failure. I usually factor RoC Watts by 0.6 which in this case gives about 400W as a probable duty rating. Not withstanding the stump pulling torque of the motor, this feels about right, subjectively. Would be nice if anyone with access to a dynamometer could test one across the speed range.

You could lash one up and run a machine with the supplied control equipment - basically gives you forward, reverse, off, slow running, variable min to max (controlled by the hall sensor as explained earlier). There are basic interlocks, so if you leave the control position at high speed and power up, a warning condition is displayed and the motor will not start up until the control position has been zeroed.

It would be best to make up a basic control pendant in a small project box with a trimpot circuit say 2 x 5K Ohm with a decent wirewound 1 turn final pot (say 47K) tuned to control between 2.4v and 4.2v. Hopefully, about 10% of pot movement will output the non running signal, another 20% the slow running output and the remaining control movement will be sufficient for the variable speed range. You could always use a multiturn pot if you needed ultra fine control but I wouldn't have the patience for the amount of dial twirling required!

In addition, reversing can be taken from the S switch on the mini control panel to a momentary press release switch on the pendant (if you want reverse operation).

E stop will be accomplished by (press to break) interrupting the low voltage control signal input back to the motor driver. I haven't tested this exact mechanism, but if you unplug the Hall device from the motor driver, it shuts down the motor and sets a fault condition on the motor driver. The unit has to be powered down to clear the fault condition.

All in all, quite a good little drop in unit for the smaller lathes and mills to replace the usual existing 4000 RPM brushed motors. Problematic with yer trad Britisher lathe due to the high motor speed compared to ye olde worlde 4 pole 50Hz induction motor. May require an intermediate shaft for low speed lathes.

B for attainment

D+ for effort (lack of documentation and flexibility)

Edited By Martin of Wick on 27/03/2021 10:04:21

Edited By Martin of Wick on 27/03/2021 10:16:26

I have had to do this for a 7 and S7, and confirm it is not a trivial job, especially if you intend to fit a new shaft. Hammering them in, using G clamps etc is not recommended, oilites will distort in a heartbeat.

You absolutely do need to make up a pulling mandrel, find lengths of threaded bar and have some appropriately sized tube washers and nuts to use as pullers.

Your mandrel should be stepped to conform to the exact external diameter of the shaft (avoid being smaller) with the wider portion say 10 thou less than the id of the bearing recess. The part upon which the bearing sits needs to be slightly (4-5 mm) longer than the bearing. Tap the mandrel for 8 or 10mm threaded pulling rod.

Pulling the old bearings out is easy, pulling the new ones in needs a bit of care on the initial alignment. Soak bearings in oil and use lots of oil when placing bearing on mandrel (it may be tight)

You may need to wring the mandrel back out of the bearing, or even need to pull it out.

My nasty experience came when I discovered the new shaft was a wringing fit in the new bearings. I tired slow running the shaft as a bearing run in, but it was clear that it was seizing.

Now here is the thing, you don't want to ream this type of bearing and even if you did, how would it be possible to do it accurately in situ? I solved this problem by making up a polished olive that was a couple of thou bigger than the shaft id. This is pulled through the tight bearing making it conform to the required size (process may have to be repeated). These bearings have a porosity, so within reason can be 'squeezed' to size.

Eventually, the shaft fitted albeit a little tight, but easily enough that after a bit of running in, all was well. The running in consisted of: run the shaft at min primary speed, as soon as the bearing gets cup of coffee hot, say over 50 C. stop and allow to cool. Repeat until happy that the heat build up is reducing.

With the lathe back in service, keep bearings well oiled and monitor temperature, ceasing operations if getting too hot until well bedded in. A year or so after fitting, my countershaft bearings get just slightly warm after a couple of hours run. I make sure the oil cups are full before every use.

Thanks to all responders, problem solved I think.....

A HSS blade tool 'good enough' to chew its way through bits o' steel is just not going to cut a chunky bit of bronze.

Using a 2mm quality cobalt HSS parting blade, straight off the grinder, the workpiece was sliced through it as if it was a piece of soft cheese, tool set slightly high, cut at about 100 rising to 150 rpm with neatcut. So I learn that a really, really, sharp tool is what is needed!

I take the point about blade overhang, but with the GHThomas / AKA Hemingway rear post you dont have an option to change projection easily as the tool height is defined by the tool angle which is designed in at 8 degrees. This results in a slightly scary projection of 1 1/8 inch on the large blade. Am considering making an alternate turret to take a horizontal blade - one day!

M

Thanks to all,

should have said, the lathe is a Myford S7.

It just seems strange the HSS parting blade set up that was performing flawlessly with steel and silver steel moments before, completely balked at the bronze.

I usually set the blades about 5 thou above centre line using the rear tool post (and deal with the annoying little pip later) Perhaps I need to set the HSS a little higher as I couldn't seem to start the cut with that configuration. The blades project quite a way from the mount on the GHT toolpost, so perhaps that is contributing to the problem.

Using the MGEHR carbide tool I was eventually able to establish a consistent ribbon of cut material about as thick as aluminium foil, but is was clearly hard work for the lathe. On inspection the actual cut surface was slightly dished towards the headstock, as if the forces involved had tried to drag the spindle out of the bearings or twist the blade and this was probably contributing to the heat build up. The blade was set as true as was possible to measure using a parallel off the chuck face and the carriage locked, so I dont know what was happening there.

Plan is to resharpen the HSS blades and set 10 thou above centre and have another go, If that doesn't work, put a new blade in the MGEHR, if that fails, buy a bigger carbide parting tool and if that fails, give up and use something softer!

Will feed back any results good or bad!

A torrid afternoon trying to part some rounds of PB - at least that is what it was sold as.

No problems encountered turning and facing dry with tangential tool HSS so wasn't anticipating problems parting.... Oh dear, how wrong....

Using a GHT backpost and eclipse style taper blades (set at correct height) at speeds between 150 to 400 the blades made no impression on the bar and just bounced off, refusing to bite. When I eventually managed to force the tool in it generated so much noise with the blade twisting and bucking that I chickened out lest I break a blade.

Managed to half do one using a tiny MGEHR insert holder not big enough to cut through completely and had to finish with a hacksaw. It was a scary operation all round, needing about 400 rpm for a steady cut and the job became so hot that the cutting oil was burnt on to it!

Can anyone please suggest an approach that works for them when parting PB? what speed, oil/no oil, or different grinds for the blades etc. (currently ground flat, sloped down at 8 degrees giving circa 10 t0 12 degrees front rake).

Thanks M

Edited By Martin of Wick on 05/02/2021 20:27:55

For basic drill sharpening I use both the old style Picador vertical spindle jig and a properly made (apparently) slant spindle clone drilling jig. much has been said about both in the forum.

In their unique way they both deliver reasonable looking drill re-grinds with satisfactory point angle and what appears to be an acceptable heel clearance (as long as some care is taken) . Best results are usually obtained with a clamp bar on the drill so each side is ground at a true 180 degrees where possible.

To improve repeatability, I thought the spreadsheet model below might be helpful (available from this site).

Joerg Hugel's Drill Performance Tables - Processes (model-engineer.co.uk)

The idea was to be able to generate a table of drill lip projections for differing diameters at differing point angles for the jigs (118, 136, and possibly 98 degrees). Hopefully, I could then make a small gauge to consistently set the point projection and lip angle and then produce grinds where relief is within the optimum range on a consistent basis (without the usual trial and error each drill grinding session). Optimum would be a projected clearance that increases from between 12 to 15 degrees at the outer edge rising to between 20 and 30 degrees at the centre.

I was wondering if anyone had investigated this spreadsheet model and attempted to ground truth it?

The first issue I had (after measuring up the jigs and calculating their geometry parameters) is that the two variable parameters that actually define the grinding cone are not direct entry - you have calculate them by an intermediate step then check to see whether you have got close to your desired axis offsets- Doh!

I was also wondering how reliable the results are? modelling the Picador (easier because the cylinder axis is vertical) the results sort of confirmed what I was getting - ie the picador suggested settings generating rather too much clearance (specially in smaller sizes).

For the clone jig, the model results suggested that an extra 5mm of forward projection was needed on top the projection required for the diameter (forward projection of 1 Dd in the clone instructions, the sideways projection is fixed on these jigs). I find with the clone jig that I usually need less rather than more projection, but that may be because I can only eyeball the finished product, which may look OK but is actually sub optimal.

Predicted chisel angles could quite interesting too...

It is quite a useful paper and spreadsheet model, well worth a look and I would welcome input from anybody that has reviewed it or attempted to use the results to finesse their drill grinding activities!

M.

I have a similar issue, but not quite such a fugly casting as that one - I assume it is quite small, so my choice would be:

set up as best you can in a vice with the shaft as parallel and normal to the cutting plane as you can judge by eye (by any means possible with whatever packing you need).

mill base as reference plane, mill long edge of base likewise

prepare piece of scrap to parallel on all surfaces large enough to overhang base of casting by 20mm or so, bolt said casting to your prepared plate with at least two fixings of appropriate size - If you are really keen you could mill out a slot in the mounting plate to fit the milled base to ensure stability for subsequent operations.

set up plate with mounted casting in vice square and parallel, mill port face and shaft bearing boss face flat, turn over mill rear of port block flat (and rear of shaft boss).

Without removing, find centre of crank boss, punch, spot drill, then drill drill through crank shaft bearing boss with correct size of drill prepared for brass/bronze etc in one go.

With luck this should result in the main surfaces parallel and normal to each other.

nb The author accepts no responsibility in any way for broken drills, mis- aligned or oversize holes or any other unsatisfactory outcomes, how so ever caused

Edited By Martin of Wick on 19/01/2021 14:48:45

You need to check the geartrain/change gear set up behind the left cover.

1 with lathe unplugged, first release quadrant to free change gear mounted to leadscrew from any other gears in the train.

2 turn the change gear on leadscrew manually to check leadscrew rotates, if so, engage carriage feed lever to check for expected movement forward and reverse - if carriage is not moving then investigate for correct movement of half nuts (by peering at right end of carriage with a torch to confirm that the half nuts move together and apart to clasp the leadscrew).

3) if that checks out alright, check that the change gears you expect to have in the train can be made to mesh correctly and check by rotating chuck by hand to confirm motion all through the gear train to the leadscrew - if not look for change gear mounting issues or potential damage (grub screws or nuts to tighten etc)

4) check operation of tumbler reverse jockey wheels - correct engagement etc

5) if all the above is Greek to you, download this manual....

g0765_m.pdf (grizzly.com)

Edited By Martin of Wick on 13/01/2021 14:36:51

Personally, I wouldn't touch a lathe with no provenance, unless you particularly want an expensive, irritating and time consuming project

From your description so far you have already added up a couple of hundred to the base price, added to which is probability of needing to replace all bearings and motorising shafts etc, the cost to achieve a even a mediocre machine is getting up towards a grand - Go to Myfords site and E bay and start adding up the costs of all running part replacements - if you can find them and you may want to think again.

It is more likely than not that the bed will need a regrind and if you regrind the bed you will need to do the saddle etc.

It will likely cost at over £300 excluding time and travelling IF you can find someone to do it.

I had a 7 done by Slideway services 5 or 6 years ago and it was £250 then- since that time the owner has sold up I am not sure if the new owner is amenable to small jobs.

Sent you a PM for basic static Myford checks

Edited By Martin of Wick on 12/01/2021 15:05:31