Prazi SD300 lubrication question

[Henry RancourtParticipant @henryrancourt22682]

Hi all,

I have a Prazi SD300 lathe (same as Hobbymat MD65) and the manual has lube instructions. One of the components to be oiled before every use is the stepped drive pulley. That pulley has no lube fitting or oil hole but it can be taken off its stationary shaft by reducing belt tension, taking V belt off the pulley and removing a snap ring. For something that is to be lubed before each use it seems there should be a simpler way to do it. Is there an easier way to lube it?

thanks

[Henry RancourtParticipant @henryrancourt22682]

[DiogenesIIParticipant @diogenesii]

The one in my Hobbymat is a standard 'sealed-for-life' ball bearing with double metal shields – it doesn't need to be lubed.

..it seems a bit odd that your manual says it must be lubed before every use.. ..have you seen what type of bearing is in there? ..if it's a sealed bearing there's no need..

[Henry RancourtParticipant @henryrancourt22682]

Very interesting that your MD65 has a sealed bearing. The Hobbymat MD65 manual shows, on pages 19 and 20, their lube instructions. Maybe I'm reading it incorrectly but is looks like an arrow points to the step pulley. I would have included the manual but can't find a way to add it to this reply.

[DiogenesIIParticipant @diogenesii]

Oh, that lube instruction! ..the little line is pointing to the fork arrangement at the bottom of the bracket that supports the pulley.. ..it slides up and down to control the belt tension – a drop or two of machine oil before use is all it needs..

[Henry RancourtParticipant @henryrancourt22682]

Thanks for the info. It would have been difficult to learn it has a sealed bearing without taking the pulley off its stationary shaft because the two copies of the manuals I have don't show that in the parts lists. They also don't show the snap ring.

[Henry RancourtParticipant @henryrancourt22682]

Hi Diogenes,

In my posts on lubing the step pulley I was basing my remarks on hobbymat md65 manuals I found online. Those manuals have differences in the parts list section and also don't have a detailed breakdown of the step pulley shown as part #5.

So I found my original manual that came with the Prazi SD300 I bought about 15 years ago. The parts list and schematic section has some differences from the manuals found online. Some components have a more detailed breakdown and the biggest difference is the motor and drive section. It has a detailed breakdown of the #5 step pulley and all related parts. It lists and shows two radial grooved ball bearings that go on the pulley holder shaft that the pulley rides on.

[DiogenesIIParticipant @diogenesii]

Thanks, yes, that sounds about right, there are two in there, back to back. Since our exchange the other day, I went out to remind myself what it's internal workings looked like.. Mine also contains a shim (like a blank washer), not sure whether an original fitment or fitted by the previous owner to adjust the clearance / belt alignment at some point.

In any case, the assembly hasn't given any trouble in the last twenty-plus years of ownership..

They're a very nice machine – and pretty much everything that needs to serviced or maintained is easy to get at – one thing not to be neglected is cleanliness & oiling of the cross- & top – slide feedcsrew – the threads that receive these are cut directly into the metal of the respective parts and so a little attention paid to keeping these in good order will pay dividends in the later life of the machine.

Edited By DiogenesII on 20/02/2021 17:40:04

[Henry RancourtParticipant @henryrancourt22682]

I’ve owned my SD300 for about 13 years and it has always worked great. Recently I started using it more and was bugged by having to bend over the bed to get the 6M allen wrench into the right locking screw. So I decided to make handles that would stay attached to the locking screws and be very easy to reach. They are now part of the lathe and make locking/unlocking a piece of cake. So now I was bugged having to use the allen wrench for locking/unlocking the tailstock spindle so I made a handle for that task. The 6M allen wrench is now in the tool box.

But now I realized something odd. To lock the carriage its locking screw is rotated clockwise and to lock the tailstock its locking screw is rotated counter clockwise. The carriage and tailstock have always been a very good fit, with the locking screws only needing about 15 degrees of rotation to go from locked to unlocked. Does anyone, with an SD300, have the same clockwise/counter clockwise locking action

[Roger BParticipant @rogerb61624]

This locking action is a result of the slightly strange (but actually quite clever) way the slides are adjusted.

The carriage is normally expected to move so the outer two screws are tightened so it just won’t move and the middle screw is then used to open up the gap until the carriage moves smoothly and without excessive play. This means that the clearances are smallest at the ends, reducing the tendency of the carriage to rock, and requiring the middle screw to be undone (anticlockwise) to lock.

The tailstock is fixed during normal operation so it is opened with the rear screw until it will just move and is clamped in place with the front screw, hence tightening (clockwise) to lock.

[Henry RancourtParticipant @henryrancourt22682]

Thanks for the answer and it makes perfect sense. My confusion was because I took the screw names to literally. I assumed that all locking screws went through the gap such that when tightened the gap was reduced and that all the forcing screws pushed against the surface on the opposite side of the gap thus widening it. Had I checked out the screw length it would have become obvious.

[charles hollandParticipant @charlesholland51724]

Hi Henry, is it possible for you to post the parts breakdown of the step pulley assembly you mentioned in the manual. Thx. Chuck

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