Member postings for Chris Crew

Well, I tried one of my brainwaves this morning and met with limited success, so limited in fact that I am going to declare it a failure but I did manage to cut a half acceptable keyway in a cam blank but this is only about the width of a Myford change gear and even then I had to take out a taper in the slot, where the tool had deflected, with the edge of a small file again.

I have another idea that will require a bit of silver soldering but that's for another day. I also had the same idea as Bernard Towers about inserting a slotted inner sleeve into the bored out bush so I may try that too. If I try all the suggestions I am sure I will eventually hit on something that works for me and then stick with it because I would eventually like to make a few replicas of Myford change gears which obviously require an internal keyway in the blank.

BTW, some excellent work shown in the photographs, well done! (I can only dream of achieving such standards).

"PS how long is the slot?"

The sleeve is as long as two Myford change gears mounted side-by-side, so about 1". The component to be made is identical to a change-gear bush but needs to be internally keyed to drive a 0.375" shaft. The device I am making is the Parkes' gear hob backing-off device, published in MEW No.57, and I have thus far followed the drawings. I have considered altering and simplifying the design because the UJ's connected with the drive shaft do not appear to be very robust and look smaller than those showing in the photographs in the magazine but it's difficult to tell. I know the device works because the late Dr. Parkes was demonstrating it at an exhibition several years ago and, following the interest I was showing in the device, he very kindly sent me a copy of the drawings and the accompanying script from which I have been working. I only very recently tracked down a copy of the magazine that it appeared in.

I have had an overnight brainwave as to a possible solution to the problem but I will not reveal my idea until I have been in the workshop today to prove it one way or another. If it works I will describe it in this post and if it doesn't I will just keep trying.

PS. Many thanks for the suggestions thus far. I will try them all if my 'brainwave' fails.

Edited By Chris Crew on 03/10/2023 08:11:54

I am building a device that requires a 0.625" diameter sleeve, bored 0.375", to have both an internal and external keyway 0.0625" x 0.125". The external keyway is not an issue but having spent an evening in the workshop making a slotting tool for the Radford slotting attachment (it works the same as any number of slotting attachment designs that have been published for the Myford), I have had very limited success in forming the keyway which is not to the standard I would have hoped for (probably another addition to the scrap box). The problem is that the tool shank is very slender 0.375", which fills the whole of the bore the idea being that this would prevent deflection and the cutting bit was of 0.125" HSS set across the diameter to be nudged out a few thou. at a time until the full depth of the key way was reached. The problem arose when the 0.125" HSS cutter kept breaking under the force applied by the slotting tool. After a couple of attempts I tried again with a tool similar to a boring tool which worked up to a point but was mostly deflected out of the slot towards the end of the cut resulting in a keyway of tapering depth. I removed this taper with the edge of a small file but I am not very happy with the result.

So, can anyone suggest a method for obtaining a better result that they may have used themselves? I know the Radford slotter works well enough on larger sizes when the tool can be made big enough to resist deflection because I have squared holes, cut internal splines and keyways with it but not at such a small size. I am thinking that the professionals may use some form of broaching to form keyways inside small diameter bores, e.g. the Myford lead-screw spacer, but I don't have this facility.

Edited By Chris Crew on 03/10/2023 00:22:45

"I have recently purchased a metal lathe and I’m teaching myself watching videos on YouTube etc. "

Welcome to the rich man's hobby, from now on you will never have your hand out of your pocket, LOL! It will soon become apparent that you will need a decent grinder, then a bench/pillar drill with a decent machine vice, then a milling machine plus all the associated tooling. Then comes the rotary table followed by a dividing head. Not to mention all the files, drill bits, taps and dies and reamers etc. you will need and that's before you start buying a stock of material to start on a project, a percentage of which will end up in the scrap box. Then when you to assess the way to tackle the next job you will find that for all the tools and equipment you have bought that you just don't happen to have the right size cutter or bit so will then be shelling out yet again and waiting on its delivery. Happens to me all the time and that's even after almost a lifetime of collecting and amassing a very well equipped workshop but you still enjoy it all.

Edited By Chris Crew on 01/10/2023 19:54:41

Workshop front built into up-and-over door aperture.

It looks like you have, or had, a roller shutter door. My workshop is a pre-cast concrete garage and I replaced the door aperture with a 'site office' type front with 4ft double doors and the largest window that could be fitted. The outer skin of the front is boarded in ship-lap which is protected with Sadolin. Your garage may benefit from a similar arrangement rather than retaining a roller or up-and-over door. Although I have the large front window and four smaller windows down the side of the building they are mostly obscured by shelving to the point where it is always necessary to switch the internal lights on, whatever the time of day, so you may not need a Velux window in the side wall which will diminish the overall security of your workshop overall. I think we must all live in fear of a break-in and losing irreplaceable tools and models. I have a workshop burglar alarm fitted, security lights all around the house and lately four CCTV cameras recording 24/7 but it didn't stop the b*******ds relieving me of my then new big-screen television and restored antique time recorder in broad daylight whilst I was out at work.

I think you would have to be a very strong man to strip the back gear when removing a chuck. Probably could sheer the locking pin too!

Edited By Chris Crew on 27/09/2023 18:29:41

I know how you must be feeling, I have recently spent the best part of two nights machining a universally jointed drive shaft for a device that I am making. I know the device works because it was demonstrated to me by the designer who personally sent me the drawings before he left us a few years ago, but I had my doubts about the proportions given by the dimensions as I proceeded. It didn't seem to me to be robust enough for the amount of power it was going to transmit etc. but I worked on the principle that those who have had designs published must have forgotten more about engineering than I could possibly ever know so I plodded on regardless. And guess what? I was right and the drawing was wrong, the errors must have crept in when the design was published because when I eventually tracked down a copy of the magazine where it appeared the accompanying photographs confirmed the shaft on the prototype device was much more substantial. So I will have to do it my way guided by the photographs I now have, with another doubt and IMO pointless complexity being removed along the way. I don't mind the time and the lessons learnt so much as the waste of material and the expense of acquiring some more. Good job the MMEX is coming up soon to replenish my stock.

If I were to be starting over again it would be a no-brainer to buy this, or a similar model of lathe, so I am a little envious of your shiny new purchase. I have never subscribed to the notion that if a product is of 'far-eastern' origin it must be rubbish because clearly they are not as this nice new machine easily demonstrates. I think the prejudice against Chinese products has almost dissipated but it still rears its ugly head occasionally.

"Thanks for that. According to the chap I'm going with, the bus takes an circuitous route and so is slow, all eating into the limited time we gave at the exhibition, especially as some of it will be taken up by a boring talk by some old fogey (me)"

I can only go by my own experience last year but the No.63 bus to Rugby was direct to Radford Semele along the A425 out of Leamington. According to Stagecoach the journey takes between 11 & 13 minutes. There may be other buses that take a more circuitous route, the No.664 is showing on the Stagecoach website for example which may take a different route, but not being a local I don't know Warwickshire bus routes, I can only go by my experience last year and the Stagecoach timetable and app. To me it was convenient, quick and above all free with my bus pass so I really don't think it will eat into your time at the exhibition because I would suggest a taxi may take almost as long as the bus.

I have just checked on the Stagecoach website and there is a return bus at 16.00, 17.13 & 18.27 from Radford Semele, but the exhibition centre is a few minutes outside the village by bus and there is the walk to the bus stop to be taken into account, so I would be at the stop at least 15 minutes earlier than the above times to avoid missing the bus and missing your train home. I will be on one of those services so our paths may just cross.

BTW, It's worth downloading the Stagecoach app to your phone.

Edited By Chris Crew on 25/09/2023 08:40:28

There is a Stagecoach bus that departs just around the corner from the railway station, It is the No. 63 towards Rugby and departs hourly at 42 minutes past the hour. It will take you to the roundabout where the A425 crosses the B4455. From there it is a five minute walk to the exhibition centre through the car park.

If you have a bus pass it is free, or rather someone else pays! If you walk through the snicket under the railway line towards the town's main street the bus stop is outside All Saints' Church. Alternatively, walk under the girder bridge and turn left into Bath Street at the traffic lights and just keep walking until you see the church on the right. From memory, there is no signed bus stop for the return journey to Leamington but the bus stops exactly opposite the signed bus stop on the other side of the road where you alighted. I used this service last year to avoid paying for the shuttle-bus and will do so again this year as I have a B&B booked in Leamington for a couple nights.

It's so much cheaper than a taxi even if you don't have a bus pass.

Edited By Chris Crew on 25/09/2023 08:18:09

I have had this fault before and it's easily fixed if you have the same problem. If you have a dewhirst switch take the front off and examine the contacts. You will probably find that they are burnt due arcing but salvageable. Simply clean them up with an emery stick and retension them with some rat nose pliers. I had been stopping and starting my single phase motor for thirty years before I fitted a clutch so all the scare stories about doing this are almost nonsense to me. Of course, I only go by personal experience not what it says in the books or what Inspector Meticulous has to say about it.

You learn something new every day, I had never heard of 'verbed' either!

I had an email from a courier company advising me of a delivery. Their contact address commenced as 'National Sortation Centre'......... That's a new word to me, never heard of 'sortation' before. It's a long time since I went to school but I thought the verb was 'sort' or 'to sort' and the present participle was 'sorting', or maybe it's the gerund? I can't quite recall after all these years. Is this yet another 'americanisation' of our wonderful language? I sincerely hope not!

Can I also commend Coventry Grinders on their service and prices for silver steel. Even though the p&p looks a little steep for a single item at first glance it remains the same for multiple items. I combed eBay for a better deal for the larger sizes that I required and found that going direct C.G. was by far the cheapest and they deliver the next working day by courier too.

"Beats me how LBSC and all ever managed to produce their creations without all the NASA and RR standards we expect of todays tooling to enjoy our hobby."

I am so pleased I am not alone in thinking along those lines. I simply don't 'get' all this fretting about the 'nth' degree of accuracy in my back-shed workshop. I take my hat off to those who can achieve it, and no doubt some models like a gas turbine require it, but my philosophy is if it looks right, fits right and works right then it is right!

I'm struggling to figure out what exactly the query is ...........

I apologise if I didn't explain my confusion very clearly but in any event it has been resolved by a forum member who contacted me via the messaging centre so I will respect his privacy. My confusion arose because I had got it into my head that the 32T worm wheel and two-start worm formed part of the gear ratios that determined the number of teeth being cut which they do but only to the extent of producing a 2:1 reduction. Although the 8TPI Myford leadscrew plays no part in the hobbing process, except to transmit rotation to the banjo at the tailstock, it is obviously taken into account when calculating the speed reduction when cutting a thread or the number of teeth on a worm wheel. The 2.5 times speed reduction required to cut a 20TPI thread, i.e. 1/20" axial travel of the screw-cutting tool per revolution of the lathe mandrel, would be converted by the Radford device to a 1/20 rotation of the gear blank if it were a 1:1 ratio. Because the worm gearing reduces this by 2:1 it produces 1/40 of revolution of the gear blank. The increase in speed of 40:30 that Radford used increases this to 1/30 of a revolution, therefore 30 teeth. The penny finally dropped for this bear of little brain!

Edited By Chris Crew on 12/09/2023 20:58:43

Here are some photo's of the temporary set-up of the Radford Worm Wheel Hobber. I set the attachment up temporarily on the lathe and used the gears given Radford's example to cut a 30T worm-wheel. You have to imagine that the hob is mounted on the arbor between the centres and the gear blank is mounted on the vertical spindle. The catch plate shown is my interpretation of Radford's indexing catchplate, which he mentioned but never described, which in theory enables anything up to six-start threads and worms to be cut but in in reality three is probably the maximum achievable. I used it to cut the two-start worm and it worked a treat. The gear set-up appeared to work but I could not immediately explain why. The leadscrew was set to cut 20TPI, but it plays no part in the hobbing process except transmitting rotation to the banjo at the tailstock end of the lathe. There is a 40T gear on the end of the leadscrew and a 30T gear on end of the drive shaft. All the other gears are idlers. Subsequently, a forum member kindly PM'd me with some very helpful information. At this point in time I haven't completely got my head around it but I hope the penny will drop soon!

Edited By Chris Crew on 12/09/2023 15:14:47

Edited By Chris Crew on 12/09/2023 15:26:58

I have built the Radford worm-wheel hobbing attachment as described in the book 'Improvements and Accessories for your Lathe' but not yet used or tested it. For those not familiar with the device it utilises the Myford leadscrew to transmit power to a train of change-wheels mounted on a banjo-arm at the tailstock end of the lathe with rotation from this gear-train taken to a vertical spindle set in a casting on the cross-slide on which the gear blank is mounted. This spindle is driven by a two-start worm meshed with a 32T worm-wheel inside the casting.

In tandem with this device I am making the Radford Thread Milling Attachment as described in the same book and I am now at the stage where I need to hob the 20DP 15T worm-wheel which is integral to the milling spindle of the device. Radford shows that this is done with his worm-wheel hobbing attachment, obviously.

In his hobbing attachment design and construction notes Radford states, "In designing this fixture, I decided to use the screw-cutting change wheels to determine the number of teeth and the tumbler gears to determine whether right or left-hand, and I decided that the number of teeth would be twice that set for screw-cutting. Any gaps in the range could be corrected by using a second set of change wheels driven by the tail-stock end of the lead-screw and driving a splined and universal jointed shaft back to the worm drive in the fixture...........

This second set of change wheels is used in the following manner. Say 30 teeth are required. In the Myford gear-box there is no provision for 15, 30 or 60 teeth, so we set for 20 teeth in the gearbox which with one to one gearing would give us 40 teeth on the worm gear blank. We have to speed up the blank to cut 30 teeth in the ration 40:30 so we can fit a 40T wheel on the end of the leadscrew and a 30T on the spline shaft drive (or 60-45) so that a gear wheel of the same number of teeth as the change-gears are set for (x2) on the leadscrew end, and change gear of the required number of teeth on the blank will give us the correct gear ratio."

I thought I sort of understood that, in principle at least, and I am assuming the (x2) Radford states accounts for the two-start worm drive in the fixture because he gives the option of using a single-start worm in the drawings but I thought I would try to be clever and prove to myself that I could cut a two-start worm. (I had the worm wheel cut by a local gear company because I was then in a 'chicken and egg' situation).

My lathe does not have a gearbox, but that shouldn't matter, although now I have come to actually do the job it seems a little more complicated than I first thought because I am not very good at working out gear ratios. I am thinking that with the hob cutter set between centres in the lathe, which I am imagining to be a worm, then for every fifteen revolutions of this 'worm' the worm wheel (i.e. the gear blank) must rotate once. Am I correct in this assumption? Please tell me if I am wrong.

What is really taxing my mental resources is the taking into account of the two-start worm to 32T wheel reduction in the fixture which seems a little at odds with the 15T worm wheel I need to cut. So, I suppose the real question is this: Can any of those people who seem to have this sort of thing calculated on spread sheets suggest a suitable train of gears that would resolve my dilemma, please?

Edited By Chris Crew on 11/09/2023 21:42:07