Motor pulley

[sean logieParticipant @seanlogie69385]

I’m trying to find a 2 step pulley withe a 28mm bore and 8mm keyway …. hens teeth come to mind ,either that or I’m not looking in the right places . My other option is to bore out the pulley on my old motor ,not sure my skill level is enough to do this .

Sean

[sean logieParticipant @seanlogie69385]

[Chris Evans 6Participant @chrisevans6]

It would be a good exercise to bore existing pulley. At best it works and you gain a few more skills, at worst you buy a pulley so you are no worse off. Where are you ? Help from someone may not be far away. Chris.

[sean logieParticipant @seanlogie69385]

I’m kinda leaning towards boring out the old one but I’d have to do it at work on the Colchester,the keyway is the bit I’m not sure about doing,I’ve seen it being done but doing it my self is a different matter lol . I live in Nairn east of Inverness.

Sean

Edited By sean logie on 22/11/2016 09:19:15

Edited By sean logie on 22/11/2016 09:21:35

[Brian OldfordParticipant @brianoldford70365]

Posted by sean logie on 22/11/2016 09:17:37:
I'm kinda leaning towards boring out the old one but I'd have to do it at work on the Colchester,the keyway is the bit I'm not sure about doing,I've seen it being done but doing it my self is a different matter lol . I live in Nairn east of Inverness.

Sean

Sean. The keyway shouldn't be too difficult to cut using a boring tool and following this video https://www.youtube.com/watch?v=XcU0LTavzDM There are several others.

[mark smith 20Participant @marksmith20]

Whats the size of the pulley? Is it a b section?

[sean logieParticipant @seanlogie69385]

Mark I couldn’t tell you,the pulleys on the headstock are z .

The size of the pulley on the old motor is around 150 mm stepping down to half that .

[sean logieParticipant @seanlogie69385]

Measured the motor pulley last night the largest od is 120mm and the smaller is 70mm . There doesn’t look to be enough material to bore it out and to 28mm cut a 8mm keyway. Looks like I’m going to struggle to keep the same gearing,this is going to be an issue isn’t it ? .

Edited By sean logie on 23/11/2016 13:15:19

[not done it yetParticipant @notdoneityet]

I tried to post previously, but it seems to have disappeared, or maybe I thought to just let you get on with it. Should be no problem sorting out alignment as long as the pulley is not rough cast. Otherwise true up an outside face and edge using a stub mandrel before setting up for boring.

My more important comment was that a larger sized motor shaft usually denotes higher power transmission. You really need to consider if your machine can cope with the extra torque/power of this new motor, if it is rated higher than the original.

Might even require a larger section belt.

[sean logieParticipant @seanlogie69385]

Hi,not done yet(liking the name ) I have considered the increase in power vs the old Fortis ,it'll be fine i thing this thing is built like a tank . I'm in the process of renewing all the bearings with better quality items . The only concern i have is that the new motor shaft is 28 mm so i wont be able to have the same gearing from the motor to the counter shaft . The size of the smaller pulley on the old motor wont allow (i think) it to fit the 28 mm shaft on the new motor . How critical will this be? . The OD of the stepped pulley on the old motor … the larger one is 120 mm the smaller is only 70 mm on a 5/8th bore .

Sean

[Steve PaveyParticipant @stevepavey65865]

If the shaft of the motor is long enough, you may be able to turn up a disc with a boss on it, bored to 28 mm and keyed to suit. Then bore your pulley to the od of the boss, and bolt the pulley to the disc (a bit like a chuck is attached to a backplate). Without seeing a photo of the pulley I don't know whether there is enough meat on the pulley to do this – you'd need to drill and tap several holes in the body of the pulley to take the bolts.

[Bill DawesParticipant @billdawes]

Hi Sean, if you are stuck try one of the engineers stockist such as Eriks. Modern industrial pulleys are usually 'taperlock' type which has a separate bush with a variety of bore sizes for each pulley size, easy to fit as well.

Bill D.

[Bill DawesParticipant @billdawes]

Sorry Sean just realised your real problem, it is a two step pulley rather than a two groove pulley, still might be worth a try though.

Bill D.

[sean logieParticipant @seanlogie69385]

Posted by Bill Dawes on 25/11/2016 10:29:49:

Hi Sean, if you are stuck try one of the engineers stockist such as Eriks. Modern industrial pulleys are usually 'taperlock' type which has a separate bush with a variety of bore sizes for each pulley size, easy to fit as well.

Bill D.

Thanks Bill ,i've just gone and ordered from Simply Bearing the exact type of pulley you've described .

And then I'm going to try what Steve Pavey has suggested .

Sean

[sean logieParticipant @seanlogie69385]

I now have the lathe running again , I went with a 95mm taperlock pulley,which i can slide back and forth when i change pulley speeds on the counter shaft drive pulley . I've setup the motor as a counter style mount with a spring for now attached to stop the motor bouncing and it works a treat .There isn't enough meat on the old pulley to bore it out and fit a keyway . My only concern now is … will the gearing difference work now if I make a thread ?

Sean

[Howard LewisParticipant @howardlewis46836]

Surely, thread cutting relies on the ratio between the Mandrel and the Leadscrew, which is determined by the change gears.

The problem that you may have is not having such low speeds available, as previously; IF the ratio between the motor pulley and the Input Pulley is different..

To overcome this, you could add further complication, (and pulleys and belt) by driving via a countershaft so that the speeds seen by the lathe are the same as the original motor set up.

As usual one job creates at least three more than you first expected! (You would not believe how many typos came as I tried to correct the first ones!)

Good luck.

Howard

Edited By Howard Lewis on 27/11/2016 20:15:33

[Les Jones 1Participant @lesjones1]

I agree with Howard. The spindle speed makes no difference to the pitch of the thread. Many people rotate the lathe by hand for cutting short threads.

Les.

[sean logieParticipant @seanlogie69385]

Thanks Howard , I have the old Fortis up and running now so i may try a few things . I may try cutting off the small pulley off the the original and bore out the larger one to 28 mm so i would have the correct gearing on the slow speed at least . (i think that's right ….isn't it lol) .

Sean

[sean logieParticipant @seanlogie69385]

Posted by Les Jones 1 on 27/11/2016 20:23:36:

I agree with Howard. The spindle speed makes no difference to the pitch of the thread. Many people rotate the lathe by hand for cutting short threads.

Les

Thanks Les

Sean

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