Myford QC box on Ebay

Does the disposal of the QC gearbox mean that you're driving the leadscrew with a servo ? I would like to investigate this but don't know if it's feasible.

-adrian

Not a servo, but a stepper motor. It is definitely feasible; the plan is to use two steppers, one for the main leadscrew and one for the cross-slide. Isn't too hard to do; the main screw will probably need some gearing down so that I don't have to use too large a motor, but as the motor and leadscrew shafts need coupling together anyway, timing belt pulleys are a reasonable and cheap solution for that. The hardest bit will be replacing the plain bearings on the leadscrews with decent thrust bearings, but there are existing solutions to that (Hemmingway do a kit of bearings and a drawing for the leadscrew; Arc Eurotrade can supply a similar kit of bearings & drawing for the cross-slide screw).

I am not replacing the leadscrews with ball screws, at least in the first instance, as I am also attempting to retain some of the manual features of the lathe (not the gearbox/changewheels though, obviously!) so for quick-and-dirty jobs I should be able to drop the half nuts out of engagement and use it as a manual lathe. I'm also just interested to see just how far you can take a conversion like this using the stock ACME screws.

Regards, Tony

Rather than bidding on those leadscrew bushes, you could ask to do a trade of the left hand one with the buyer of your gearbox :-)

PS. I've noticed a lot of the auctions I'm looking at the moment have this bidder3, bidder4 disguise nonsense. Is this because messrs. Ebay have made hiding the bidders identity the default now?

Mark Rand RTFM

Nah - I want spares as I plan to mangle one set & want to be able to change it back if things go pear-shaped

Looks that way - I can see the bidders' identities as the person doing the selling, but not on items I bid on.

Regards, Tony

It kicks in once the bidding goes over £100.

Peter

-- Peter & Rita Forbes Email: snipped-for-privacy@easynet.co.uk Web:

It's been done to stop the second chance bids for unauthorised users. What has been happening is that once an article has been sold the second and third bidder has got an email thru Ebay to say the sale has fallen thru and do they want to buy this at their last bid price but to save fees and deal off Ebay.

Needless to say these are fake and they don't have the goods.

If they had just stopped second chance bids and made them have to relist they would actually have got more money and better credibility. Now it's open to shilling without anyone knowing.

-- Regards,

John Stevenson Nottingham, England.

Visit the new Model Engineering adverts page at:-

It also puts me off from even looking at items because I don't have any feel for what sorts of other prats are involved. If people want to deal off Ebay for listed items then they deserve to lose their money :-|

It was also obvious on some items before, that shill bidding was going on. Now that it's much harder to spot, more people will get ripped off.

Mark Rand RTFM

Just shows that Ebay don't give a monkeys about shill bidding - they make their money either way. It's the customer that suffers and in the Ebay hierarchy that's well down the list of important stakeholders.

Charles

Is it your intention to drive the leadscrew purely for position control, or do you intend to replace the gearbox with electronics : i.e. drive the leadscrew in sync with the spindle for threadcutting ? This is what I thought would be difficult and would perhaps require the greater speed range of a servo over a stepper.

-adrian

I'm planning to do both (position control and gearbox replacement). Granted, the potentially higher speeds of a servo would be helpful, but I believe a stepper-based system won't have too many limitations - at least, not too many for the uses to which I will put the lathe. Anyhow, the proof of the pudding etc...

Regards, Tony