Harrison M300 or M250 pulley/belts problem

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.

If you are banging on any bearings it is standard practice to use a soft headed mallet or a soft metal drift, not a steel hammer directly on the shaft. All to do with impulse force.

Edited By not done it yet on 09/08/2019 13:39:38

Michael.

No. I haven't done this on your model, but I have come across this method of fitting gears and pulleys many times on various machines in the past.

NDIY.

I don't think anybody has suggested Michael hammers directly on the shaft with a steel hammer !

Keith.

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

Rollpins, of the size that you seem to have don't require a huge force to refit them. I could imagine that a 4 oz hammer would suffice. You are looking to overcome friction and compress the split rollpin. For the same interference, you would not be able to drive a solid dowel into place!

If possible refit the rollpins to the pulley and hub, before refitting to the lathe.

before tearing everything apart, turn up a counterebored dolly, so that you can use the central setscrew to press the pulley onto the shaft. In this way you will not be putting any impact load onto the bearings.

A large thick washer, and the setscrew might be the impact free method of refitting the rollpins, (doing both at once with care )?

Howard

That's what I'm thinking as a first option - I don't want to hit that thing at all if it can be helped. I know that roll pins are meant to go in easily but I've also known it not to work out that way from time to time.

I would look into replacing the belt with a linked belt.

Ebay UK 254121291285. This type comes in several sizes.

Edited By old mart on 09/08/2019 14:20:34

old mart. There are 2 belts in parallel which must be a reasonable match.

MC My M300 (late model with sloping front edge to tray) has much more clearance from the pulley (120mm dia) to the headstock than your photo appears to show, belt changing is easy and the pulley is fixed with two set screws and does not have a centre bolt. Not much help for you but it does show there are variants.

MC Have now dragged my M300 handbook out from its resting place. Headstock parts breakdown clearly shows M6 x 20 bolt Part 33 screwed into end of shaft through "safety washer" part 31 and "washer retaining" part 32, pulley is keyed to shaft by a single woodruft key. So appears to be, M6 bolt out and pull pulley from shaft axially. No sign of any spirol pins

Thanks KWIL, yes clearly a different variant. Mine's actually a T300 (which comes in loads of variants). It has an M300 head-stock and an M250 gearbox and lead-screw. I'm not sure which the carriage is.

Thanks also old mart but I'm not a fan of linked belts.

Looking at the washer/disc held on with the rollpins, it might be only a chisel or sharp screwdriver that is needed to remove it. Bearings can take a certain amount of hammering, I belt the drawbar of the mill every time to break the R8 taper.

MC Mine is the later headstock wih the completely flat face where the gear selector controls are. I would hazard a guess that you may not need to worry about the roll pins but merely remove the M6  and draw off the double pulley using a simple puller.

Edited By KWIL on 09/08/2019 20:44:05

Sorry I am a bit late late to this party. I don’t know if you have already sorted this. I have just finished stripping and rebuilding my M300. The roll pins only stop the washer/cap from rotating on the shaft, meaning that as you tightened the screw you are only pushing the pulley on rather than twisting/binding it on the key. On mine I just removed the screw, then the whole assembly came off. The roll pins remained in the cap / washer. You may need a puller to get the pulley off if the shaft is dinged from previous abuse, or if there is corrosion. Mine pulled off easily by hand.

Having said all of that, your pulley looks a bit on the large side, which may be why you are struggling getting the belts on. My belts easily passed the cap screw. Is the top speed of a T300 lower than an M300? Here is a picture showing the pulley clearance on my machine. Sorry for the poor picture, this is a crop from a picture of something else.