Member postings for Michael Cross 4

Thanks, that's what I needed to know. M

Thanks Keith - I hope you won't think this question is impolite but have you done this yourself on this or a similar model? I hope you won't take offence at the question, you can understand why I would ask.

Thanks - but it's not damaging the roll pins I'm worried about, it's banging on the end of that shaft with a hammer! I don't think the bearings are designed for that.

I get that - but can hammering on the end of that shaft (which presumably runs in bearings not designed to take much thrust) be a good idea?

Thanks Howard. In the M300 manual that I have the pins aren't shown on the motor/pulley page (301/2) but one is shown on the head-stock page (302/2).

I'm not sure which set-screw you're referring to - the motor pulley has one but I can't see one anywhere on the shaft pulley (which doesn't have a hub).

Keith, thanks - I was thinking of that as my next step. The main thing that concerns me about that is getting the roll pins back in when I put it all back together - assuming the pins come out with the cap do I knock them out once it's apart and put new ones in? If so how do I drive them into the shaft? I don't imagine hammering them could be right. I guess I could use that screw thread to push them in but I can imagine that going wrong too...

I do hear you - but I'd like to hear from someone who's encountered this before too.- it's quite a common lathe and I'm sure someone will have has the same issue.

It's a pretty critical bolt and awkward to get to and re-tighten. I'd rather leave it alone if possible.

Certainly no grub screw and I can't see anything else retaining the pulley so I guess that's what the roll pins are for?

As near as I can tell the pins go into the spindle (or shaft or whatever it's called).

Those coiled pins give the pulley a 'don't take this off' sort of vibe - but then how do you replace the belts?

That screw seems to go into the shaft but came out easily and isn't obviously holding anything, I wonder if it's just used to install the pulley as it would push it into place nicely.

Just to be clear - I'm not contemplating taking that bolt out, just how to get the pulley off.

Thanks, here's a picture, arrows point to the bolt that the belt won't pass and the two coiled pins (out of focus).

... I guess it's not the 'spindle' pulley - I just mean the big pulley on the gear box not on the motor.

Hello,

I have a Harrison M300 which needs new belts. I can't get the old ones off the spindle pulley because they're blocked on by the bolt that holds the head-stock onto the bed - and I'm certainly not removing that. They almost squeeze out but not quite, I could probably force them but it doesn't feel right and I fear getting the new ones on the same way could damage them.

So it looks like I need to get the pulley off the spindle - which is the bit I'm not sure about. The pulley has a cap on the end of it which is held on by two coiled pins and on top of that is an m8 machine screw that goes into the end of the spindle. I don't see a ready way of getting the cap off - I can't get a bearing splitter behind it to pull it off and I'm sure drilling out the coiled pins can't be the intended approach. I could maybe get a big bearing puller and pull the pulley of with the cap in place - but even that doesn't look Ideal as I can't really access the spindle to push against, I'd have to put a screw into it and push against that. I don't know how tightly the pulley is on but it certainly won't come off with hand pressure. The motor pulley came off quite easily with a puller but went back on with hand pressure after a tiny bit of cleaning, I suspect this would be similar.

The M300 manual shows the cap part without coiled pins, but mine has pins and they look original, the similar M250 has the same type of setup and the manual shows the pins. I'm not clear what the cap and m8 screw is actually for - except that it might be belt and braces to stop the key from working its way out.

Obviously I could do without damaging any parts so I'd be really grateful to hear from anyone who has come across this before and can either provide advice on removing the pulley or some other way of getting the belts off and back on.

Thanks

Sorry Jacques.

doh - you can't hit half a tooth. Has to be 4 divisions.

I don't think that's right.

1/8 of 20 teeth is 2.5 teeth, on a 6mm ledscrew that's 15mm of travel so any thread where you'll find threads exactly 15mm apart will be fine. That covers 0.2, 0.25, 0.5, 0.75, 1, 2.5, 3, 5 and 7.5

2 divisions on the dial is 30 mm so that adds 2 and 6 to the list and so on.

Thanks to all who have helped on this - my final decision was to use 20 teeth and 8 markings on the dial. Although this doesn't quite cover all scenarios I think it will suit me best most of the time as it means that for a lot of threads (anything that goes into 15) I can hit any number, whereas with 6 divisions you've got to wait for the dial to come round to 1 or 4 and that'll irritate me. Anything that goes into 30 I can hit quarter revolutions of the dial, 60 is half revolutions and 120 you just pick a number and don't change your mind.

That really only leaves the 7s - multiples of 0.35. I very rarely need those so if they come up I'll either just leave the nut engaged and reverse or switch the gear for 21 teeth and pick a number.

I find I very rarely need to use a 3d printer but there are times when it really comes up trumps.

I was just thinking that - no reason not to when you're going that route.

That's a terrific idea - you're making me feel stupid. Thanks!