Member postings for Martin of Wick

Is this likely to cause any major concerns, or is it tolerable?

Does that not depend on the intended application of your worm? You have just shy of a one thou. in pitch error. Probably OK if you are not expecting to use it in an application where the errors will accumulate (such as a rotary table or instrument rack etc).

For example, if you are planning to use the worm to drive a rotary table with 90:1 ratio, one turn of such a table with your worm would have 90.0 x 0.0009 = .084 thou in. positioning error, you can decide if that is significant or not.

If you are using your worm to drive a hacksaw or the suchlike then the error is not material.

Riiight....

well, may be useful to invest in a 3MT centre in case you want to turn BC in future but also for checking your tailstock centre alignment for general work. When my minilathe came out of the box, the tailstock was way out of horizontal alignment and my first piece of parallel turning was a gentle taper!

Centre drills are not to expensive, best to get a few in a selection of sizes for future use.

Check the size of the fixed steady to be sure it will admit your 1.5 inches diameter - I opted not to purchase the factory device as it seemed too small to be useful, but it might just take your project.

As I suggested, you can avoid using a steady (because in this case it is only used as a convenient way to locate the centres for drilling).

Instead, you can use a centre finder to scribe 3 or 4 lines at as even spacing as you can eyeball across the face of the bar. Then centre punch as close to the centre of the resulting triangle as you can judge. You can either use a bench drill to centre drill the recess, or you can set up in the lathe chuck and manually guide the work bar on to the tailstock chuck and drill the centre recess as best you can.

If you don't have a centre finder, it is a bit more tricky but it is not impossible to scribe the bar face by careful measurement with a rule, plate and scribing block, or even just odd leg calipers (piece of glass will do as a surface plate).

lathe is a Sieg SC2, so as far as i can tell, turning between centres isn't possible as I cannot get a centre in the headstock.

Why exactly? you will need to remove the chuck to get the centre in I think, but not necessary to use centres unless super accuracy needed, in which case check your centres align in all planes before anything else.

In any case, if t'were me I would clock up the bar in the 4 jaw, then if you have a fixed steady clock up the bar at the tailstock end, then with fixed steady in place centre drill as required to fit your dead centre. Oil the centre drilling, wind in tailstock with centre and lathe away.

If you dont have a fixed steady, you can use a centre finder, punch and use bench drill or lathe.

You don't comment on your turned size - if much less than an inch, you may want to take lighter cuts as you approach size.

You had better luck than I did. In my case the bearings rattled around in the block recess with about .8mm clearance - completely useless.

Had I been fortunate enough to obtain one with a decently tight fit, I would have lubricated thoroughly, pressed the shaft to front bearings then to the block, then tapped the back bearing with tube down over some blocks with something large and heavy (or resorted to the trusty 12 tonne press if all else failed). Other methods would probably work just as well, such as place bearing in block then press shaft in.

If you are of a sensitive disposition, pre fitting, you could polish the spindle up a bit with fine silcarb paper on't lathe to a tight sliding fit , but go easy as easy to overdo.

I had a similar saddle rock problem with that type of lathe, seems to be quite a common problem. Check there isn't a burr or warp on the saddle base . In my case there seemed to be a slight bulge. Perform the tests and checks above to be confidant you have properly diagnosed the problem.

Check out this link to see a method I used to ensure a good fit of the saddle to bed - seems complicates but is actually very easy and quick- go carefully as it is easy to over do it! **LINK**

I find it hard to believe the vee in the saddle is really wider than the prism it sits on, but it is possible through bad manufacture. If this is truly the case and the misfit is gross, shimming may be an option.

Alternatively, you will find you can obtain a complete new saddle from one of the partners (in no particular order ARC Amadeal others etc.) on this site will not break the bank (typically <£30.0).

The irony is the CAA are proposing a registration and training scheme when one already exists through the BMFA. needless to say, for model fliers the CAA scheme will be hugely more expensive, a cost risk to taxpayers and deliver fewer benefits than the existing scheme.

Unfortunately the reason for this sorry state is two hidden agendas.

one is the complete failure of our wonderful administrative classes to recognize the risk that multirotor drone technology posed until too late, resulting in the usual ' OMG, the public needs to be protected...' we must redeem ourselves and look like we know what we are doing... - cue knee jerk solution. Because the remedy is designed by bureaucrats it is an overly costly paper and red tape solution that will have no impact on illicit operation.

Secondly, the commercial drone operators have bent the CAAs ear and want a 'clear skies' policy - they don't like the idea of having to share airspace with those flying model aircraft, even though there is very low level of increased risk as unmanned vehicles will only take over activity conducted by piloted aircraft (in the main).

So as a model aircraft flier (proper aircraft that need to be flown by hand and brain as opposed to multi-rotor computer controlled abominations) I am not optimistic. if the CAA get their way, the charges will escalate so that within a few years model flying registration will cost more than owning a PPL, and that will be the end of it for model flying unless you want to specialise in micro models under 250g.

And lo and behold, criminals will still get their drugs delivered to their cell window and terrorists target their drones packed with anything they like to cause maximum mayhem from the other side of the word without batting an eyelid.

Look out for new registration requirements coming soon on owning knitting needles or garden spades, now deemed to be required to prevent potential slaughter in allotments up and down the land.

Pat

The mini lathe comes out of the box pretty much OK for simple work. It is only after while that you start to notice that all is not as it should be, on longer spindles, deep drilling, and precision work etc, by that time it is probably out of guarantee.

As stated above, the tailstocks are quite crudely finished and offer poor adjustment, such that you can spend an entire day chasing your own tail trying to get some degree of repeatability in the setting.

Both my C1 and C3 clones were a right PITA to bring to an acceptable condition (even after sorting the C1 with shimming and the C3 by reaming and lapping due to the badly cut MT socket)

To try to reduce the general level of frustration when you recommence investigation, I suggest you allow plenty of time, take a good note pad for readings and sketches, take readings twice to check consistency by rotating testbar and repositioning the DTI and in general try to trap or minimise all other sources of measurement error to fully identify the issue . You will get there in the end, it just takes monumental patience. And when you do achieve reasonable performance, you will never ever want to disturb the tailstock again! Should you feel the urge to turn tapers, use a tailstock taper turning attachment if only to protect your sanity!

Martin

Pat,

I commiserate with you having suffered similar tailstock issues on this lathe and another smaller sino lathe.

I am no expert but from my understanding, this is not an uncommon problem. I had the same lathe and encountered similar issues with erratic tailstock readings. In my case, the problem was due to an incompletely reamed MT2 taper in the barrel, but even when this was sorted, I spent the best part of half a day setting it to be collinear with the bed and centred on the head.

Before even considering shimming the headstock, I would advise the first action is to check and confirm the headstock spindle is collinear with the bed in xy and zx plane. You will need preferably a 3 MT test bar or 3/2 MT sleeve. If it appears the spindle is aligned accurately, move on to tailstock (if the spindle is not aligned, depending on severity,you will have to decide whether you wish to attempt to rectify yourself of contact Amadeal and request a replacement).

Next ,check the fitting of the MT2 test bar in the tailstock and absolutely confirm that you can see no play in the taper as it enters the barrel (push backwards and forwards with some vigour to confirm this). In my case It took me a while to recognise that the MT2 was only being griped at the narrow end and there was 10 thou of play at the front of the barrel (partly because I didn't want to believe it!)

With headstock spindle alignment checked and the MT2 in the tailstock fully retracted, can you get the two centres to line up point to point perfectly? (the ruler on the points trick will be an adequate test of this). Do the points stay fully aligned when the tailstock barrel is extended? If not, perform whatever adjustments you can on the tailstock and repeat tests. It is more of a concern If the tailstock is significantly too high when the barrel is retracted, and at this point you may wish to contact the vendor.

You don't say whether you are testing with barrel in or out and whether you have clamped stock and barrel for test and tightened carriage gibs, so will assume you have. After the tests suggested, if there is still a significant rise on the test bar, then the issue could be with the barrel bore or tailstock mating surfaces.

In that case you may be able to shim one end of the tailstock body to sole plate so the barrel is not pointing at the sky while still getting the centres to align. This worked for me on a similar class of lathe, but took hours of to-ing and fro-ing to get to the point where drills could be used from the tailstock without obvious flexing and binding.

It may be that the solution would turn out to be skimming the tailstock - an awkward job so I would see what the vendor has to say if this is the case. You should not have to shim up the headstock for a misaligned tailstock, but it would be a solution in the last resort.

Martin

Depends on blade, teeth count, how robust and solid everything else is etc. My CY90 (budget class small horizontal band saw not that solidly build but performs well within its class) speeds are 20/30/50 m/min.

using 14tpi carbon steel blade at 20m/s it is quite comfortable with steels, but certainly not at 30m/s

Aluminium and brass fine at 30m/s, or lower, any higher it starts skipping and grabbing, so I have never use the high speed but expect it would be fine for plastics

Martin

Neil, Thanks for that.

In fairness the gear had not actually failed, but as you see, about a third of the tooth flank has been chewed away on the left side of the worm gear.

In the gearbox the worm and gear appeared to be well meshed and central (as far as I was able to tell cos you cant actually sight along the axis of the worm spindle). Looking again at the photo, I was wondering if the gear was not properly aligned on the axis of the worm? Is it just my eyes, or would you say that the low point of the impression the worm has cut in the gear is also to the left (I assume if perfectly aligned the low point the worm has 'cut' should have been dead on the centre).

So ,would you advocate replacing the same gear moved a couple of millimetres to the left in relation to the centre of the worm axis? at worst it would just grind down the right hand side of the gear to match the left before concentrating on the middle and eventually wearing that away to failure! Which as you say may take years.

Trevorh,

because the bearings are contained only in a die cast gearbox housing, the options for positioning the worm and gear in relation to each other are pretty limited. However, as intimated above, the worm gear can be moved up and down its shaft and locked into position with a grub. Just difficult to see the relation between worm and gear when fitting into the box. Some careful measurements will probably be needed to locate the gear exactly.

Of course, one assumes that when in use the worm gear shaft will not move in relation to its bearings for this to work!

ega,

I would say this saw has not had a very hard life. It has not been used that frequently, but when it has been used it has often done pretty heavy duty work for long periods without complaint.

The saw is one of Warco's offerings, but I expect however branded they are all much the same. Bought on impulse at a show for an almost infeasibly low price. Have not been disappointed until now. But as Neil says, best thing may be to just bang it back together and run it until it finally grinds the worm wheel to dust, which might be years hence!

I noticed that my 10 year old CY90 bandsaw has been leaking oil slightly via the driveshaft. On closer inspection this time, the oil was loaded with fine brassy material, so decided to open the gearbox and take a look and found it to have become mysteriously filled with 'antique gold' paint.

The pictures say it all realy... dissapointing as the machine has not been used hard in its life, the original 14t carbon steel sawband was still going strong before I dismantled it. BTW, for anyone contemplating dismantling, it was a right sod to get apart - everything seems to have been assembled using oversized shafts and tectonic forces. A bloody good 3 leg puller and a suitable hydraulic press is required.

As far as I could tell the driveshaft bearings seemed OK with no play or float and the worm appeared to be set correctly 90 degrees to the worm gear. The helix angle of worm and worm gear appear the same (approx 4.5 degrees)

I was wondering if anybody had a view as to the reason for the premature failure? How might this be prevented / mitigated in future?

I have purchased a new worm gear but as they are quite expensive, I would like to try to avoid having to replace them every few years (anticipate using the saw rather more in future).

New oil seals will be required, but as the unit is stripped down, would it be worth replacing the various shaft bearings as well?

As I have modified the saw to allow vertical use, Some fairly good sealing may be needed on the worm shaft as all the oil in the gearbox will be vertically above the drive shaft in that configuration. The present shaft bearing area will only accept one bearing oil seal as the centre portion between the fore and aft bearings has been machined undersize.

There is a thin walled tube spacer between the driveshaft bearings that I was considering replacing with something thicker, machined to accept internal and external O rings to seal both the shaft and bearing housing/spacer annulus. Just concerned that this is a fair bit of work and the o ring on the rotating shaft would wear very fast and become inefective.

Has anyone else come across these issues with this or similar bandsaws? I would certainly weclome the benefit of your eperience, ideas or solutions to these problems.

Truth is, it has been a good little saw, saves vast ammounts of effort, cuts straight and accurately and is very versatile with the usual mods and accessories.

Thanks,
Martin.

Thanks to all that replied, very helpful and useful to know that this is material OK for general use, also useful to know that high speeds and low feeds are the way to go. I now feel emboldened to give the project a try. And if it all goes pear shaped, at least it wont break the bank!

As the project is only for home mini lathe use, the ultimate in high finish and durability is not really necessary. I hadn't thought about scraping issues but I wouldn't have thought it necessary for this application.

AdrianR - you ask an interesting question, I always thought in my ignorance that anything described as 'black steel' by stockholders was technically the same as hot rolled steel. Somebody please shout and tell me quickly if this is not the case!

I don't know of any helpful steel stockholders near to Weston that are willing to supply small quantities so was going to use M Machine Metals, but only because I have used them before (other stockholders are available).

Thanks to all,

Martin

I was wondering if there was any views on the suitability of using black hot rolled steel (HRS) as the basis for machining a slotted cross slide about 8 inches by 3 by1.

Cast iron would be preferable but always seems very expensive (>£50) rolled steel would be about £10. I am unable to heat treat so can't use BMS and I don't fancy fabricating a table, leaving HRS.

I would treat the rolled steel similar to cast iron, taking a deep cut with a carbide face mill all round to get rid of scale, then take approx. to size, then mill the slots and v-ways then mill the tees, then finish mill the surfaces (or grind on my Stent if I have to.

Is this sort of work feasible with this material? will it do as the 'poor mans' steel / iron and are there any common issues, risks or other things to be aware of when generally working with HRS?

Ta

Martin.

Yes well, as you say Neil, a bit unkind but having had such a struggle to get the spindles out and bearings off I wasn't feeling kindly disposed to the little tinker. The front bearing removal took 2 attempts with the hydraulic press and came off eventually with a hell of a bang!

After much spindle and counter shaft polishing I can now put the new bearings on with only a gentle press fit, then replaced the nylon spindle gear with metal, left the countershaft with the nylon gear.

skimmed the bearing covers to accommodate the new bearing and put a slight chamfer on the front cover to allow it to mate with O ring used to seal the gap between spindle and cover. Will leave the back open for the time being pending trials.

I hope TRBs will be a worthwhile mod, and as you say, there is only a modest amount of work involved for a basic set up, but it is not trivial work and it does take quite a time. It looks like the O ring trick to fill the space between spindle and bearing cover is viable. There is a little bit of friction, but I expect that will ease with use.

XD 351,

I have been studying your picture, but can't quite grasp it.

I get the new end caps, I see the black ring in the end cap which I guess is a rotary oil seal of some sort.

My question is regarding the black cylindrical object on or following the 40mm spacer with the circumferential grooves that apparently passes through the oil seal. Is it also some sort of rubberised sealing material, or just a piece of metal turned to fill the void space and allow a semi labyrinth effect? Does it sit on the spacer, or follow the spacer so it is compressed by the spindle nuts (if soft)?

Thanks

Martin

Michael, thanks.

That is interesting, can I ask if you modified the end caps to accommodate the O ring, or just 'squished' them down on the O ring and let them wear their own groove in the cap if needed?

As a supplementary, when you inspect the bearings, does it look as if they have retained their grease reasonably well, or does it look as if the lubricant has been thrown out of the back of the bearing? - I assume if the latter is the case, you take the opportunity to try to squeeze some extra grease in somehow before replacing the caps?

I suppose if the headstock fills up with grease over time no harm done as it can be scraped out and recycled to lube the gate hinges or garage door etc!

Thanks,

Martin

Neils,

Thanks, as you point out, the Boxford was properly designed from the start for TRBs - so no issues. Fitting TRBs to a Chinese mini lathe is a kludge that raises a whole bunch of issues, unfortunately not a simple 'drop in' solution as is often presented .

In practice, need to be looking at a solution similar to XD351 if wanting to use and protect MTRBs long term.

Thanks for that Neil, Adrian

as you say did notice as a minimum, the bearing covers will need to be relieved slightly to make space for the TRB roller cage. Still leaves quite a big gap, but apparently this does not appear to be as big problem as I imagined (visions of loose tools, dogs and small children, etc being sucked into the exposed bearing). Just still feel queasy about exposed bearings.

It is possible that oil seals of 48x60 would probably do with some further modification of plastic covers, but the covers are 8mm thick and the thinnest seal I can find is 7mm. Similar solution, differing sizes on the internal faces. Perhaps this is overkill and quite expensive at about £5-6 per seal.

There is a possibility that a 48 x3mm O ring could be used if the external cover was adapted a bit more - not a seal as such, but would minimise the gap on the external faces and help keep out coarser muck. Partially shielded TRBs are also available but I have not located any at the required size (at a price).

Think I'm leaning to cheap ACBs as a trial/quick fix while I ponder the requirement for TRBs long term.

Martin.

Having had a knock down - drag out fight with my Chinese mini lathe to get the spindle and bearings out of the headstock, it occurred rather belatedly that the TRBs I was about to fit would be completely open with no protection (very much a Doh! moment). The carefully applied grease would puke out of the bearing fore and aft and every species and class of swarf, abrasive dust, moisture etc would pile in, cue dead bearing in short order.

Scouted about on the web and could find very little discussion of this particular, rather embarrassing elephant in the room from those that wax lyrical of the subject of bearing replacement.

Question is to those who have opted for this mod - what, if anything, can be done to resolve this problem ?

I can think of various solutions but all seem to involve significant extra work and expense in making new or modifying the bearing covers to accept rotary seals on the external bearing faces. Cant think of any solution to seal the back of the TRB so lubricant will be ejected into the headstock cavity no matter what- the existing headstock has most definitely not been designed for TRBs.

I am hoping there might be a simple, cheap, reliable, fix but I suspect that the choice will be restricted to two of the above. My possible quick fix may be to chuck the TRBs into the roundtuit box and go to sealed angular contact bearings (cheap and simple). Would prefer to use TRBs if there was a reasonable solution though.

Would certainly welcome others experience and solutions with this irritating problem.

Martin.

I have a Warco/Soba 6" rotary table, Purchased 6 or 7 years ago for around £100 because I only ever buy the cheapest anything on principle, WTF, it is just a hobby.

Perhaps I have been lucky as I can confirm it is perfectly OK for what I do. out of the box it was in a pretty sloppy condition. There are two main adjustments to be made, worm engagement by twiddling the eccentric to give maximum gear engagement while checking for no unacceptable tightening at other points on the rotation and backlash by crimping down the shaft collar to the point where there is an acceptable balance between handle stiffness and minimal lash.

Once adjusted, the backlash is consistent at about 2 minutes of arc at any point on a full rotation, there is a very slight variation in tightness around a rotation, but this doesn't seem to affect angular motion. I manage the backlash by the usual means and can confirm that 90 cranks of the handle returns the table to the starting position give or take a couple of thou. I haven't bothered dismantling it to examine the gearing on the principle of ' if it aint broke, it don't need fixing'.

I have used the table occasionally for milling curves, facets and making a division plate. At the current rate of usage, I have every confidence that the table will outlive me by several centuarys. My only complaint is that it is so heavy, I can hardly lift it, glad I didn't get the 8 inch version.