Here is a list of all the postings Alan Charleston has made in our forums. Click on a thread name to jump to the thread.
|Thread: Backlash Allowances for Gears|
Thanks for all the helpful advice. I agree that as far as the change gears are concerned, I don't need to be too fussy. They are DP 18 which is equivalent to Module 1.4111. I have a set of Module 1.5 cutters (20 degree P.A.) and I figured that the difference in the profile between Module 1.5 a 1.4111 would be small so I cut 3 extra change wheels using Module 1.4111 to calculate the OD and depth of cut. I made them from Delrin so I wouldn't damage the existing gears. The gears worked well. They seemed to mesh OK with the existing gears.
I then had a go at cutting a 14 tooth pinion on the handwheel shaft in the apron. The DP of the gears here are DP 20 which is equivalent to Module 1.27. I repeated what I did for the change gears using a Module 1.25 cutter (20 degree P.A.) and cutting a Module 1.27 pinion. I made the new shaft and pinion out of steel. It didn't mesh at all well with the second wheel in the apron train. This situation is quite different to the change gears as the shafts are in fixed positions and the clearance needs to be right which is why I was interested in getting some guidance on how to go about it. I managed to set the pinion up in the dividing head again and cut the pinion a bit deeper but the meshing was still not good, so I put the old one back in.
I concluded that the problem was the pressure angle so I'm looking to get a set of DP20 cutters with a P.A. of 14.5 degrees.
The reason I'm looking at working on this is that there is a lot of backlash in the handwheel on the apron although looking more closely at it I think the main wear could be on the pinion which engages with the rack on the bed. I'll pull it apart and measure the pinions and gears across pins but again, I need to know how to determine the backlash allowance so I can calculate what the correct across pins measurements should be.
In the past I have cut gears by making a blank with an OD of the pitch diameter plus twice the addendum and, using commercial cutters, cutting to a depth of 2.2 times the addendum.
This has worked OK but I watched a youtube video by Keith Rucker - https://www.youtube.com/watch?v=9Dl5J9b8GBw - where he used an excel spreadsheet he had devised to calculate the measurement across pins to ensure the gears were cut to the proper depth. A screenshot of the spreadsheet is shown at 36minutes into the video. There are two inputs which are the backlash which is defined as 0.040/P and the clearance which is defined as 0.157/P where P is the Diametral Pitch. He said he was going to publish the spreadsheet but I don't think he ever did.
I have found a calculater here - http://salemcompany.com/cgi-bin/cabAS.py?a=./gears/pages/Salem1501HS.html&b=./gears/pages/Spur1501S.html&c=./gears/pages/Salem1501FS.html .
There is a box labelled Backlash Allowance. If this is left empty, and the dp, pressure angle and number of teeth are entered and the calculater run, a recommended backlash allowance shows up in the results which I assume you can put into the front end and recalculate. There is no allowance for a clearance input.
The problem I have is that the recommended backlash allowance is quite different (higher) than the 0.040/P suggested by Keith Rucker.
Can anyone tell me if the backlash allowance worked out by the calculater is perhaps a combined backlash/clearance figure?
One of the reasons I am keen to measure gears across pins is that I have an old Boxford lathe and I want to make some more change gears for it. As I understand it, the pressure angle on these should be 14.5degrees but the two reversing gears at the top have 20P.A. stamped on them so I'm unsure as to whether the main train gears have 14.5 or 20 degree pressure angles. I've made a pair of dp18 racks with the two pressure angles but they both seem to mesh with the gears OK. That's when I came up with the bright idea of measuring the gears across pins. The problem is that if I use 0.040/P as the backlash allowance, they look like 20 degree gears and if I use the backlash allowance recommended by the calculater they look like 14.5 degree gears.
Can anyone help me?
|Thread: New old 1950's Myford 7 Lathe still in the crate|
The seller has posted this:
My grandfather was a fitter and turner by trade and bought it with the intention of using it in his home workshop. However he lost interest in doing so and my father inherited it from him. While my father was also a fitter and turner by trade he never wanted or needed to use it so it had just sat in his garage all these years in its original crate. A great shame really. We'd love it to go to someone who is passionate about using it.
|Thread: Is this really a clock?|
The maker posts updates on the HMEM website.
|Thread: BOILER CLEADING|
What about steel shim plate. Relatively cheap, readily available, flexible and should be easy enough to get paint to stick.
|Thread: gear cutters|
Gear cutters used to be a fearsome price but I have had good experiences with cheap cutters from Aliexpress. Here is a link for a full set (8 cutters) of DP24 14.5 degree pressure angle cutters for a bit over US$70. I can remember paying about that for one cutter about 20 years ago. The DP gears are hard to find on Aliexpress as most of them are module cutters but a search for "gear cutters 14.5 degrees" digs them out.
|Thread: Vintage lathe meets 21st Century|
Very interesting. Like everyone else I'd be interested in the motor and controller details.
Will the servo motor you're planning to drive the leadscrew with be linked to the headstock motor to allow screwcutting? If you can get that to work, then pretty much any knackered old lathe can be brought back to life with a bed grind.
|Thread: can i silver solder cast iron|
If you have a nice crisp break with the two bits fitting snugly together you might like to try gluing it together with an epoxy glue such as araldite. This can give a high strength joint which may be OK for your application.
|Thread: Single to 3 phase vfd|
Sorry for the delay in letting all those who helped know how I got on.
The controller I settled on was a Series 9000 Vector Frequency Controller
After paying the motor supplier to install the cable between the controller and the motor, I installed the motor in the cabinet under the lathe (a real PIA) and was in the process of mounting the controller when the cable came out of the gland. I got in touch with the motor supplier and after we had passed through the “Well I've done hundreds of these and nobody's complained before!” phase it transpired that they had used glands designed for armoured cable rather than screened cable. So, (mutter, mutter) back under the lathe again to get the motor out and back to the supplier. The proper glands gave much more secure connections.
After the motor was reinstalled and the controller mounted, I started using the system and came across a couple of problems which centred on the motor deceleration time. The motor supplier had set this at 6 seconds which he said was standard for lathes as too short a time could result in the controller being burnt out.
The first problem I encountered was during threading. My usual practice is to cut a 3mm wide groove with a depth equal to the root diameter of the thread at the end of the thread. The tool is then run into the groove, the motor stopped, the tool withdrawn and then returned to the start point by running the motor in reverse. The half nuts remain engaged throughout. The delay between switching off the motor and the tool actually stopping, made it difficult to get it to stop in the groove. The lathe has an 8TPI lead screw and a Norton gearbox to cut imperial threads and a range of metric threads can be cut employing change gears. I didn't have a thread dial indicator with the lathe however I managed to make one which meant I could disengage the half nuts at the end of each cut which stopped the tool dead. So that was one problem sorted.
The second problem with the delay between pressing the STOP button and the lathe actually stopping is safety. If I get into trouble and press STOP, there will be a period of continued operation. It will be worse than a lathe continuing to rotate due to momentum as I suspect the ramp down period will be under power and will overcome the force produced as I am wound into the work.
The STOP button on the controller is a fairly small target to hit if you're in a hurry and I would like to install a larger STOP button. I presume this can be achieved by utilising a pair of the analogue input terminals and a switch but I can't make head or tail of the Manual. Can anyone help me with some advice regarding this?
After all this negativity, there are some aspects of the VFD that I like.
The ramp up time gives a very gentle start which is particularly good if the work has some weight.
I can do threading at 100rpm without having to engage the backgear.
When parting off, it is useful to be able to change the speed to get away from a resonant frequency if chattering becomes a problem.
The VFD reduces the number of pulley changes required which, given that they involve kneeling on the ground and fumbling around in the cabinet under the lathe is much appreciated.
On balance, given the hassles I had getting the VFD up and running and the safety concerns, I'm not sure if I would install a VFD and a 3 phase motor rather than a single phase motor and a reversing switch if I had the time over again. I suspect not.
This is the second time I have written this. The first time I made the mistake of trying to create an album of pictures to go with the words. When I returned to the post it had - of course - disappeared. I'm not making the same mistake again.
Thanks for the comments. For some reason I thought the screen was used as the earth lead so I bought a 3 core cable which of course was a total waste of money. Given that I made such a basic error I decided that perhaps it's not such a good idea to fiddle about with mains wiring. I've taken the motor and controller back to the motor supplier who will wire them up for me for not much more than it would have cost me for the (correct) cable and fittings.
At this stage I'm a bit annoyed with myself for being too ambitious by going for a 3 phase motor and vfd rather than a single phase motor with a reversing switch but I suppose if it works I may appreciate it.
My VF drive has arrived from China. I ended up getting a WK 9000 from NFLiXin. I've bought a couple of meters of 3 core, neutral screened cable (really expensive at $25/meter) to connect the vfd to the motor, which is earthed via the screen to minimise rf interference. I've never used this wire before, and I'm not sure how to make the connection to the screen. Is a short section of the screen twisted and put into a connector close to the wire and then a piece of insulated wire to the motor earth terminal, or is a section of the screen long enough to get to the motor earth terminal twisted and insulated with some heat shrink?
If anyone has a picture of this, I would be keen to see it.
Thanks for the replies. The HuanYang vfds are a bit more expensive than the one I was looking at but still cheaper than the local quote. I'm a bit worried about the "Chinglish" manuals as raised by Mick so I may look at getting the HuanYang vfd so I can take advantage of John's offer to help with the programming.
John, what was the model number of the inverter your friends installed. The problem with sites like Aliexpress is that the choices are confusingly large. Buying from China is always a gamble but if your mates are happy this reduces the uncertainty a bit.
Thanks for the tip a bout local suppliers Ian. I'll give Fishers a ring tomorrow as well.
I'm in the process of restoring an old Boxford AUD lathe. It came without a motor so I've been running it with an old 1/4 HP washing machine motor until I had the lathe running to a point where I was confident I didn't have a piece of scrap metal. I'm there now and I'm ready to splash out a bit of money on a proper motor. I'm planning on using a 750W (1 HP) 3 phase motor with a single phase to 3 phase variable frequency drive. I've got a quote for the bits locally (New Zealand). The motor is OK at $277 but the going price here for the VFD seems to be $550 - $600.
I can get something such as this
from aliexpress for about $130.
Has anyone had any experience with this item or a recommendation for a suitable device from Aliexpress?
|Thread: John Wilding 8 day Weight Driven Wall Clock|
I wish you good luck with getting the clock to run. After banging my head against a brick wall for months, I finally conceded defeat and packed the bits away in a box. I probably took too long to flag it away. If you can get it to go, I'm sure you'll get a real kick out of it - but don't keep at it for too long as you'll end up feeling bloody useless.
I bought an old seized up Boxford lathe which I'm in the process of refurbishing. The problems are just the right difficulty for me to make them interesting but are solvable which has helped to restore my faith in myself.
Frankly, I wouldn't recommend anyone start the Wilding clock. He's woefully inadequate at explaining how the clock works and how to go about building it.
|Thread: Centering square stock in the 4-jaw|
If you find the centre of the square using a height gauge (or scribing diagonals if you don't have a height gauge) and centrepunch it you can centre it in the chuck using a wobbler.
|Thread: Convensional vs climb milling|
One situation where it is definitely better to climb mill is when cutting gears in plastic such as acetal. If you cut the teeth using conventional milling you end up with a hairy finish on both the top of the teeth where the cutter exits, and the side of the gear the cutter exits on. If you climb mill, the hairiness is confined only to the side the cutter exits as the cutter enters the top of the teeth. It's easy to remove the hairiness on the side of the gear using a razor blade but very difficult to trim the top of each gear individually.
|Thread: Cutting brass tube|
On small diameter/thin walled brass and copper I use a jewelers piercing saw which have very fine blades and give a nice smooth cut with no burrs.
|Thread: Boxford Cross Slide & Top Slide Disassembley|
Thanks for all the comments. I looked at the "workshop manual" suggested by Hopper. The problem is the Boxford headstock is completely different although it might be worth while getting a copy for the rest of the lathe. I've found Tubal Cains series of videos on disassembling a 9" South Bend lathe on You Tube helpful as well.
I hope ega's comments about swapping the clamp pins don't apply - I didn't note which pin went in which hole when I pulled it apart.
I've managed to sort out the problems.
I got a couple of screwdrivers under the top slide and a bit of gentle levering forced the pins back far enough to free it from the cross slide.
As far as disassembling the top slide itself, I finally figured out that the brass nut was the same diameter along its whole length and that it could be levered out through what I thought was the shaft hole. Once that was done, the top slide came apart without any trouble.
Easy if you know how.
I've bought a sad old Boxford AUD lathe which I'm in the process of resurrecting. I've got the headstock and gearbox working OK and now I'm working on the carriage. I've struck a couple of problems.
The first is that I can't get the top slide off the cross slide. I've taken the bolts which clamp the rotating mechanism out and can see the ends of the clamping pins at the bottom of the holes but I can't get them out far enough for the cone on the bottom of the top slide to come out of cross slide. I seem to remember Tubal Cain on Youtube had a similar problem with a South Bend but I can't for the life of me find the video.
The second problem is in disassembling the top slide. I've taken the screw and the gib out, but the brass nut stops the top part from sliding off the bottom part and the bottom dovetail is to wide to allow it to come off sideways. It seems to be an impossible puzzle.
Any suggestions to get round these problems?
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