My new lathe a Warco 918

Here you go Mike a picture of the modified lead screw drive assy. You can see that the nut is steel with a full length brass insert, of course I didn't see the original parts but going by the manual drawing the new nut looks to be longer.

The lead screw runs in a pair of sealed ballraces, to the right of the bearing housing there is a threaded nut with a grub screw the nut adjusts out any end float.

The cross slide gib has been replaced with a heavier brass version 5mm thick and the adjusting screws increased from 3 to 9. I must admit I thought the 9 screws over the top but who am I to argue there is no play at all and it is silky smooth in operation. The top slide has the same mods, scraped in faces, ball races, heavy brass gib and 6 adjusters, he certainly went to town on it when he made the changes.

Made a start just cut the channel through to the rear of the saddle. The last cut revealed a porous area but there doesn't seem to be any weakness or depth to it plus there is an inch of metal below it.

Thanks for the photo Ron. Crikey, with my night owl question and your up with the larks response, you must be a very early riser, or located several beneficial time zones away.

The modification looks to be very well done indeed. Your description of the nut answers the question on backlash adjustment for wear. My original thought was that the brass insert might have been two pieces, one fixed in place the other threaded into the nut body and locked after adjustment. It was difficult to see from your original picture.

Yes, having nine gib adjusting screws does seem to be a bit of overkill and patience tester when setting up, but if it works, that's what counts.

I did come across a post on another forum on the subject of power feed conversion, but it was more a discussion of motor types. However, a video at the very end show how a 10x22 size lathe was modified to add a drive shaft below the lead screw and combined with a redesigned apron to make a geared system. Ingenious, but complicated. Your approach seems much simpler to make and with suitable electrical fail safes, probably more flexible in use. Looking forward to your updates (one of which has already appeared).

For general interest, here is a link to the discussion thread.

https://www.homemodelenginemachinist.com/threads/power-crossfeed-help.22091/

Mike

Hi Mike, I should pay more attention to the parts, the nut does indeed have two brass inserts you can see in the picture below the pair of tiny grubs screws for adjustment at either end.

Ron

Once again, thanks for the follow up Ron.

Turned up and tried for size the first part of the drive leaving enough material on the rear which will become the first half of the clutch. Still working on that, I have a couple of ideas trying to keep it simple but effective.

A couple of pictures of my take on a dog clutch for the cross slide feed, the slotted traveller is spring loaded with an internal compression spring keeping it pushed back and disengaged against the lever boss. To engage the clutch the lever boss is slid forward pushing the traveller to engage both pins for drive. I will have a stepped or angled slot on the motor mount for the lever to engage in maintaining the connection of the two pins.

I used the end of the top slide to keep the sprung traveller engaged, the lever will be held in a slot on the actual fitting to the lathe.

Forgot to add the pic of the parts that make up the clutch.

I now have a driven cross slide which has worked out quite well, tested it this morning with various cuts, various materials. With brass and aluminium it sailed through it with no issues but of course steel would be more of a test. I put up some 25mm EN1A and tried various facing cuts, I went up to 1.00 mm which was fine and it would probably handle more but I didnt push it. The thing I was hoping the drive would handle is parting so using the rear tool post and a 2.0 mm insert I tried the steel. No issues at all, no grabs, no hesitation, cut smoothly all the way through, how nice it was to have both hands free whilst parting off.

I then tried parting some EN8 and the drive wasnt so happy with that, it hesitated a couple of times. I think the answer is to upgrade the motor/box to one with a higher torque rating. I happen to have one, its a bit bigger in diameter, twice as long but with 4X the torque of the one I am using and wont need that much work to change it over.

The way I have gone about fitting the drive means the motor/box/clutch and drive hanging out the back off the saddle. To use an inline motor on the centre line of the lead screw it has to be positioned that way as the cross slide runs out 90mm when fully rearward. It would be possible to have the motor closer and tucked underneath the cross slide but it would mean building a gearbox of some sort.

Anyway pleased with the drive it works well enough, just a couple of improvements to do, change the motor and sort the electrics plus build a small control unit and fit to the front of the lathe.

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.

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

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.

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.

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

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.

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

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

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

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

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