Wow, looks good!

I thought I knew the Pultra accessory range, but I'm not familiar with the item shown in the second picture. Some sort of tailstock?

Andrew

That certainly is an unusual tail stock, I can't see anything like it in any of my Pultra parts catalogues etc.

I don't think it looks like a Pultra part that's been modified either, but it looks nicely made and fit for purpose (as far as I can tell from the photo) , so well done, you'll not regret buying a Pultra ! I believe I've got eight, at last count, they may be breeding ?

The compound slide looks a bit modified, but as long as it's functional, who cares. Someone must have done it for a reason.

Hope you enjoy using it, I'm sure you will.

What you need now is a nice Mardrive or similar motor/countershaft arrangement.

Colin

That's a good question, I'll have to go and have a look in the morning. I've only got one with the quick close lever on the headstock. Just to muddy the water, that one is a 1770, but with the large bore headstock, it is listed in the catalogues of the time, it takes the 20mm collets, same as the 1590 models. Think they are 19.7 mm by 1.666mm pitch. Much like Schaublin W20 collets.

The Mardrive doesn't take up much room if you can arrange it into a cabinet and fit it underneath the lathe.

Or in one of the under drive cabinets that Pultra sold, with drive to the left, drawers on the right, and room for your legs and the clutch pedal in the middle, quite neat.

Colin

I've got a couple of 1750 headstocks fitted with collet closers. I'll have a look tomorrow evening and figure out how it works. Current assumption is that something goes slightly over-centre as the collet grips. My collet closers look like they are intended to be used without stopping the spindle, as one would expect.

Andrew

Dell

To power the Pultra I would recommend one of the Industrial sewing machine motor kits being offered on "the Bay" and especially the one made by Jack. The kit has a powerful ( 3/4 HP) brushless DC motor, with mounting components and includes the motor electronic drive unit similar in function to a VFD and all for circa £100. The kit is truly "plug and use" with no wiring up needed. The motor can be mounted in an under drive configuration, as it is usually fitted on a sewing machine, or behind the machine. Interestingly the Mardrive unit was originally designed and used on industrial sewing machines and I believe the stand the Pultra was offered on was also derived from the same.

I have my sewing machine motor mounted on a bracket just behind the headstock and have used a VB 8x375Li belt to couple it to the spindle pulley. There are pictures of my set up posted on the ME site. The motor can provide extremely high torque even at low speeds so a countershaft arrangement isn't really necessary. If an overhead drive arrangement for milling/gear cutting etc is needed then just buying a separate motor is probably easier and since the motor is so small , about 100mm cube, it could be mounted on the overhead drive column.

The only downside I have found so far is that speed control algorithm of the drive unit is designed for sewing machines and from the OFF position goes to a fixed low speed setting ( can be preset to between 100 and 200 rpm) before moving through to a linear speed control region that goes from the low speed setting to the max speed which can also be pre-set up to 4000 rpm. I've changed the motor pulley to a smaller one that matches the Pultra spindle pulley to limit the max spindle speed to 4000 rpm as the original motor pulley would have e driven it at 8000 rpm on max motor speed obtainable. I'm not sure what the max spindle speed is for a plain bearing Pultra but I'm sure the ball bearing head is rated to beyond 8k rpm.

Another feature of the motor drive unit is that it provides servo speed control so the motor can accelerate and decelerate to the set speed demand vey quickly and the speed doesn't vary much with load. Not much of an issue with a direct spindle drive coupling and collets but could be if using a high inertia countershaft system and a big chuck.

I've found that the Brushless DC are exceptional performers and have recently "upgraded" my Bergeon 30535 watchmakers lathe base and motor unit with a BLDC motor to replace the noisy, dusty and smelly brushed AC motor. The BLDC motor runs virtual silently and there is no smell of ozone or carbon dust generated by the arcing brushes as a plus. To do this I used a BLDC motor controller used for electric bikes and COTS 24V DC power supply module. All low voltage and safe to wire up and the EV bike controller is better in that it can control speed from zero to max speed in a single linear range.

I'm also thinking of doing the same to a Bergeon Multifix motor unit which is equally noisy and has very poor variable speed control which it does by moving the position of the brushes with respect to the stator.

There a some tiny 2kW ( 3HP ) BLDC motor available so I might try fitting one to my Colchester Chipmaster !!!

Clive

Having read the manual after posting I realised that I was wrong about setting the collet position. Should have read the manual before posting.

Colin has saved me from needing to scan and post the relevant pages.

Andrew

I've had another look at both of my collet closer headstocks, this time with the manual open at the adjustment page. It's not clear that there is an over-centre effect. The closure just seems to rely on friction from a spring loaded ball in the handle, on the extreme left, on serrations on the spindle.

The way I read the manual is that the handle, extreme left, is rotated to close the collet onto the work and is then locked in place. The vertical handle then simply opens the collet or closes it to the pre-determined place. Probably the best thing to do is look at a real unit while referring to the first and third photos posted by Colin.

Andrew

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It matters not a jot, Dell … but I have to ask:

What makes you think that green was its original colour ?

MichaelG.