Doesn't work here either. Ian S C

Old Thread i know ( sorry !) but as i’m doing a similar conversion or more of a modification to the current set up to my mini lathe i thought i would ask a few questions . The origional conversion i did still used the two speed gearing but recently i have started using this lathe more often the steel gears i fitted are whining thier teeth off and it is driving me insane ! I could use the majority of the set up i had but just use a longer belt to feed drive from the layshaft up to the spindle , this way i coud use a stepped pulley on the motor and layshaft to give either 1:1 or possibly 3:1 drive ratios but changing these over might be a fidget . I can also do the same as Neil has and run straight from motor to spindle with no reduction .

Motor is 0.75 kw @ (i think ) 1380 rpm .

Neil, now that this conversion has been in place for a few years how have you found the performance of the drive ratio you have now ? Do you feel it has impacted on low speed turning ? And if you had to do the conversion over again would you change anything ? One thing i really hate is the tumbler gear lever at the back so may change that also .

Ian.

Just a quick update as to the progress of my conversion so others can use the info if they wish .

My lathe has a previously fitted taper bearing conversion so some of the parts can be reused , i have now added grease nipples and grease ports to lubricate the bearings if wish . The alloy bearing covers have double lip seals fitted so the grease can only exit through the bearing and to the inside of the headstock .

The pulley and belt were purchased , they were cheap enough to not bother making the pulleys which are steel and come with a 10mm pilot hole . The 4mm key slot on the spindle for the back gear has been lengthened so it picks up the pulley bore and the collar that the seal rides on was made for the previous conversion and just needed shortening .

The alloy cover that the banjo fixes to will have two slots cut into it to allow the belt to exit to the rear of the headstock and this will run around the same size pulley that is on the spindle , this pulley will have transmission power fed to it via a set of "A" section V pulleys to allow a ratio change .

I still have to finish the layout of those pulleys as i want a clutch which can be activated by pulling a lever to loosen the drive belt , i did briefly consider modifying a manual clutch from one of those cheap minibikes on ebay but i think it may be more work than what it is worth – still undecided .

I will also be doing something with the tumbler gear set up as having the lever at the back is a pia , i might make a linkage system up so i can mount the positioning lever ontop of the headstock .

If Neil doesn't mind i will keep posting in this thread , I didn't want to start a new thread to post the occasional update.

Ian.

If you have a VFD, do you need a clutch?

But I was thinking it doesn't have to be that abrupt. You can program the inverter to take say 3 seconds to ramp up or down, which is as fast as a clutch probably. On belt changing, depending on the belt you use – on my recent Unimat conversion I use a round belt with no provision to loosen it. They pulleys are designed so they always use the same length irrespective of ratio and its easy to shift from one to another by hand.

I habitually power tap using the VFD on my mill. I line up the tap with the hole and hold it with the manual quill feed so the tap is just in the hole and pressing lightly. VFD is set to 6 – 10 Hz, I flick the fwd switch and cut until the thread is well established; then stop, let the mill stop (which it does very fast from such a low speed) then reverse it. If the hole isn't blind and there's a clear run on the other side I tap right through in one go; otherwise discretion is the better part of valour so I finish the thread by hand once the tap is running true. I have never broken even a small tap this way, though once I forgot to turn the speed down after drilling – that was exciting!

I'm sure the same would work on the lathe.

Today i completed the modifications to the alloy housing to allow the belt to feed through to the pulley , i also relieved the inside of the housing a little so the pulley face has some clearance and i then opened up the hole for the spindle about 3mm in dia . The cup shaped item on the end of the spindle is for the tacho proximity sensor

A very tidy installation

… although I would prefer to see screwed fasteners used for motor mounting

MichaelG.

This is a beginners question so dont shoot me down in flames. I guess you guys obviously looked into it before you started but it would make me wonder is a mini-lathe capable of handling all this extra power..?

Ron

p.s. I have just seen on Ian,s earlier post 750 watts, so not that much of an increase I was thinking the motors are 1.5 – 2 HP or something similar.

Edited By Ron Laden on 16/12/2018 11:04:20

Edited By Ron Laden on 16/12/2018 11:06:41

If you crash the machine it won't matter much if its 1/2 hp or 1 hp you are going to break something . You just have to remember to drive it like the lower power unit even though the power and temptation is there to push it harder . I still have the nylon gears in the tumbler as they act as a safety stop for the leadscrew and i do intend to play with the belt tension of the poly v belt to allow some slip if i get to aggressive with the machine . I'm hoping that the weight of the motor will be sufficient for the v belt tension but I won't know that until i use the machine and this would also allow some slip if needed . The motor is actually a 0.55 kw unit so 3/4 hp , i always thought it was a 1 hp unit – why i dunno.

Never going to shoot a newcomer down in flames for asking a question Ron! If you don't ask you never learn !

Edited By XD 351 on 16/12/2018 11:33:51