My new lathe a Warco 918

[Niels AbildgaardParticipant @nielsabildgaard33719]

A great step forward for the church of 9*18 size lathes.

The first motor You showed had a torque rating of 0.15Nm

First guess

What will You now recomend and what max rpm?

My lathe is a WM250 550 or very close to Yours sizewise.

[Ron LadenParticipant @ronladen17547]

Hi Niels,

You are quite correct with First guess re the motor I went with, actually it is not the Mclennan motor but a cheapie version, it didnt come with any torque figures but with a similar spec I assumed similar output figures. Working out the drive/clutch parts was fairly straight forward but to be honest I had no idea when it came to the size of a geared motor.

I really went down to basics for the output speed, I simply did a series of facing cuts in steel and aluminium and timed the number of turns on the hand wheel to get an average speed working at the rate I would normally, that led me to 100 – 120 rpm (approx)

Power/torque required was really a finger in the air job and more by luck than judgement I wasnt too far away. I can face 1.0 mm deep in EN1A and parting with a 2mm insert was no problem on the same material. As I mentioned though I think I was running out of steam when parting some EN8, so although I am happy with the rpm range I think more torque is required. I would have thought a 120rpm motor/gearbox with something around 1Nm in the way of torque would be fine, well from what I am seeing with my lathe at least.

I do have another motor/gearbox in the drawer which is a MFA 975D1041 6 – 12 volt 5.5 amp 67rpm (though mine is faster than that) its listed at 2Nm which is 12X (not the 4X I mentioned earlier) than the motor fitted currently.

So I am going to give it a try, will let you know how it turns out.

Ron

[Ron LadenParticipant @ronladen17547]

Mk11 version, a much higher torque motor/box and a modified dog clutch. The previous clutch with the internal spring and hand lever worked but it was awkward to use. So I have removed the spring and lever and drilled a pair of holes for a spring loaded 4mm ball bearing which locates the traveller in the engaged/disengaged positions. Just waiting for some 4mm balls to arrive, I had 2 but lost both to the workshop gremlins in no time at all.

If all works out OK I will see if I can get some video of it making some cuts especially parting.

[Ron LadenParticipant @ronladen17547]

Well some success I think, the cross slide drive with the heavier duty motor/gearbox seems to have more than enough torque to cope with heavyish facing and parting. A couple of videos below showing a GT insert facing with a 1.5 mm cut across some 6082, also parting off some inch and three quarter EN8 with an insert parting tool.

No hesitation or stalling, really pleased with the parting that was the operation I was hoping would turn out ok. Since doing the video I have faced the 6082 with a couple of heavier test cuts 2.00 and 2.5 mm, again no problem with the drive but I dont want to start getting silly.

Apologies for the video, "bad camera position" but I think it shows the drive works well.

So quite chuffed I now have a driven cross slide.

[Niels AbildgaardParticipant @nielsabildgaard33719]

That is an acceptable box of chineese lathe kit You have got there says a man who drove an Imperial Boxford of latest model on scrapheap in anger.

Awesome 918 Lathe ,but why not a bigger spindle?

Put  same kind of motor on the leadscrew and tell us all what size motor.Please?

If You do not need the ultrafine longitudinal feed from gears anymore it will be easy to put in a much stiffer spindle.

It is the gearwheel on spindle that is a little tricky by monster-spindles and very fine feeds.

Edited By Niels Abildgaard on 28/06/2020 18:09:10

[Ron LadenParticipant @ronladen17547]

I need some help guys, I need to fit a limit switch at each end of the cross slide to stop the drive and prevent a mechanical over run, I was hoping to use a pair of micro switches. The motor speed controller has two controls a rotary pot for speed with an off switch built in and then a SPDT switch with a central neutral and forward one side and reverse the other.

I obviously need to be able to reverse the drive off the limit switch at either end but havnt much idea of how to go about it. I would like to keep it simple if that is possible but electrickery is not one of my strong points so any help would be much appreciated.

Thanks

Ron

p.s. forgot to say the motor and controller are 24 volt DC.

[Ron LadenParticipant @ronladen17547]

Morning guys, I have been struggling to find a solution to the lead screw drive wiring and not understanding much about electrics doesn't help. I did find a circuit yesterday which I have sketched below. It shows the two limit switches and a DPDT switch for reversing the drive. Could any of you knowledgeable guys tell me if it looks OK or otherwise.

Thanks

Ron

[Martin ConnellyParticipant @martinconnelly55370]

The circuit you want is to have 1a and 2b connected to one motor terminal, 1b to one limit switch and 2a to the other limit switch. The remaining two limit switch terminals connected together go to the other motor connection.

Martin C

Sketch added

Edited By Martin Connelly on 02/07/2020 10:28:53

[Ron LadenParticipant @ronladen17547]

Thanks Martin, very much appreciated.

Excuse my ignorance but are the diodes not needed..?

Also the DPDT switch I have coming has three terminals down one side numbered 1,2 and 3 and three numbered 4,5 and 6 down the other side, can you tell me how the 1a,1b etc in the circuit drawing cross reference to my switch.

Many thanks

Ron

 

Edited By Ron Laden on 02/07/2020 12:23:29

[Martin ConnellyParticipant @martinconnelly55370]

The diodes will be for spark suppression, I was too lazy to draw them in the quick pencil sketch. The chances are your switch terminals will be the two in the middle of each side are the equivalent of 1 and 2 in the sketch. One end of the switch will be the a terminals and the other end the b terminals. A multi-meter or continuity checker (battery and lamp/led) would soon verify this. I would expect three on one side will be 1a,1, 1b and the three on the other will be 2a, 2, 2b if the switch was marked like the diagram.

Martin C

By the way the diodes shown in the original diagram are the wrong way round and would bypass the switch if you had positive and negative supplied as shown.

Edited By Martin Connelly on 02/07/2020 12:57:48

[Ron LadenParticipant @ronladen17547]

Hi Martin,

I have a multi meter so I can check, as well as the switch I have the diodes and micro switches on the way plus I have an old small dc motor so I can wire all up on the bench to test it out before wiring the cross slide motor just to be safe.

Thanks again for your help.

Ron

[Martin ConnellyParticipant @martinconnelly55370]

I edited the previous post as you replied so I will repeat what I put in in case you missed it. The diodes on the first diagram are the wrong way round.

Martin C

[Martin ConnellyParticipant @martinconnelly55370]

Thinking about the diodes for the circuit I drew, put positive on terminal 1, negative on terminal 2 then the diodes should be as follows:

The top switch should have the triangle pointing to the left, bar on the left.

The bottom switch should have the triangle pointing to the right, bar on the right.

If the motor runs in reverse to what you expect reverse the motor connections as it is easier than having to swap the diodes around if you change the input to the switch.

The bar on the diode symbol matches the band found on most diodes.

Martin C

[Ron LadenParticipant @ronladen17547]

Thanks yet again Martin, will let you know how I get on once the parts arrive

Ron

[SillyOldDufferModerator @sillyoldduffer]

Posted by Martin Connelly on 02/07/2020 12:44:07:

The diodes will be for spark suppression,

…

I thought that at first, but looking again they have a smart purpose.

If the limit switches are hit they open and stop the motor. Now the clever bit! When the current is reversed with the DPDT, the diode bypasses the open switch and allows the motor to back away from the limit. The motor can't drive past the limit but it can always reverse away after being stopped.

Ron's first circuit is wunderbar because it recovers automatically from a crash. The diodes are needed and they're shown the right way round. Martin's circuit is OK but it requires manual resets after bumps.

Dave

[Martin ConnellyParticipant @martinconnelly55370]

Dave, you are correct, the original circuit works as drawn. It does require start up current to flow through the diodes though so heavy duty diodes would be required. I wonder what would be specified. Don't think my version needs manual resets. I've drawn the switches open in the operated position when they should be closed (nc contact) which may be why you think it needs resetting. 

Martin C

Edited By Martin Connelly on 02/07/2020 15:22:03

[Ron LadenParticipant @ronladen17547]

Morning Martin,

I have sketched the circuit adding the diodes etc can you check I have it correct. Also, I have shown the switch to how you suspect it will be and I have assumed it will be cross wired 1a to 2b and 2a to 1b..?

Thanks

Ron

[SillyOldDufferModerator @sillyoldduffer]

Posted by Martin Connelly on 02/07/2020 15:16:20:

… It does require start up current to flow through the diodes though so heavy duty diodes would be required. I wonder what would be specified. Don't think my version needs manual resets. I've drawn the switches open in the operated position when they should be closed (nc contact) which may be why you think it needs resetting.

Martin C

Big current diodes aren't my thing but many automotive types look good, this MBR10 from Farnell does 10A (surge 150A) up to 100V for under a quid. I doubt Ron needs a heatsink for this application because the diodes only have to work until the switch takes over again – milliseconds, unless there's a jamb.

I thought your circuit needed resetting because I didn't think it through! Slapdash, sorry…

Dave

[Ron LadenParticipant @ronladen17547]

The lathe came with a number of accessories, one of which is a vertical milling slide (picture below) I have never used it as I have the mill but this morning was the first time I have taken a good look at it. It looks to be quite decent quality, certainly robust and with a very smooth action on the lead screw with no play or backlash. The vice is good to for its type and I think the swivel arrangement on the mounting plate is well thought out.

I wondered if anyone can recognise it as shop bought or homemade, just interested.

[Ron LadenParticipant @ronladen17547]

Sorry double post why I keep getting this I have no idea.

Edited By Ron Laden on 04/07/2020 12:38:41

[Martin ConnellyParticipant @martinconnelly55370]

The improved sketch looks right to me. If you have been following the discussion Dave and I have had the original circuit would also work. Since a diode that failed short circuit in either circuit would bypass the switch it is across rendering it ineffective you may chose to use my offering but omit the diodes, your choice. You can add them if there is a problem in the future but with the current and voltage you are using I think it is unlikely.

Martin C

[Ron LadenParticipant @ronladen17547]

Hi Martin,

I havnt received the DPDT switch or diodes yet but I have the micro switches and a small test motor, I also found a matching pair of SPDT switches so sandwiched them together to make a DPDT for a bench test.

Works a treat as I,m sure you knew it would, I think I will leave the diodes out to start with.

Thanks for all your help, very much appreciated.

Ron

[Martin ConnellyParticipant @martinconnelly55370]

Regarding the vertical slide, there are some features that look like they would need a mill to produce. Specifically the insertion slot in the base for fitting the tee bolts into the slot. If you have a mill for this would you make a vertical slide for a mill? Examination of this feature may show if it was milled or hand made.

Martin C

[Martin ConnellyParticipant @martinconnelly55370]

Dave, I think I was equally slapdash in assuming the first circuit's diodes were for spark suppression and not thinking through beyond that.

Martin C

[BizibilderParticipant @bizibilder]

The vertical slide is an early Warco one. This was designed with two hold-down bolts to fit the Myford cross-slide, either facing the spindle or at 90deg to it. The steel plate was an adapter plate, sold with the vertical slide, to allow it to fit the Warco 920 lathe and "allow rotation through 360deg". The three part vice was a standard fitting that came with the slide.  It cost £90 new and was advertised in ME around 1992.

Added:  I just noticed that someone has modified it by putting two spacers in to hold the end plate away from the slide – a darn good idea because one fault with the slide is you can only load the t-bolts from the "bottom" of the slide which is a right pain!  Note to self – make two spacers for my own slide!!

Edited By Bizibilder on 05/07/2020 20:13:49

Edited By Bizibilder on 05/07/2020 20:18:20

Edited By Bizibilder on 05/07/2020 20:22:14

[Author]

Posts