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Alfred Herbert high speed bench drill

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Andrew Tinsley06/03/2021 15:00:41
1343 forum posts

I have just started renovating this drill. It isn't the common high speed bench drill that one normally finds, if you google the above title. I believe that this one is an earlier model, probably pre war or wartime manufacture. The main spindle is supported on a vertical sliding surface and fastened there while the quill can be used in the normal manner via an adjustable lever. The setup is very similar to the much more common Pollard drills

Now the problem is this. It has a notice listing its speeds. It has 6 speeds ranging from 2350 rpm to 12,000 rpm. Lifting the belt cover reveals a block of 3 flat pulleys on the motor with equivalent pulleys on the main spindle, there is a very thin, wide belt transmitting the power. It still has its original massive motor which is a 1/3 hp, 2880 rpm three phase. The motor is specific to this drill and a massive mounting arm is integral with one of the motors end covers.

So my query is how does one get 6 speeds with this set up? There appears to be no reduction gear box on the drill, if there is, then it is mighty small and no lever to change gear! I was expecting a 2 speed, three phase motor, such as a Dahlander. The rating plate shows the current to be 0.6 amp at 400 / 440 volts. There are only 3 wires going into the motor, which rings alarm bells. I would surmise that it is wired in delta as there is no sign of a neutral, but then the motor is stated to be 400 / 440 volts NOT 240 volt 3 phase as I would expect with delta connection.

There isn't a terminal cover plate on the motor, the three wires just go through a grommet on the motor casing. Next move will be to dismantle the motor and see what is there. Not easy, as I can barely pick it up!

Does anyone know how you get 6 speeds out of this oddball?





Edited By Andrew Tinsley on 06/03/2021 15:04:40

John Baron06/03/2021 15:12:02
445 forum posts
180 photos

Hi Andrew,

The motor is 440 three phase ! But I recall a similar high speed drill that had an extra pulley, so you could swap the motor one. The motor was adjustable for distance to account for the change in pulley size. Might have been an Alfred Herbert one. If it is the one I'm remembering, the chuck only went up to 3/8", tiny little thing.

Mike Poole06/03/2021 15:12:31
2940 forum posts
70 photos

The Meddings high speed drill has additional pulleys to implement more speeds, the pulleys are quickly released with a thumbscrew and the pulleys are a light push fit on the shafts. Could the Herbert have a similar arrangement?


Andrew Tinsley06/03/2021 16:58:57
1343 forum posts

Please ignore my comments about the motor being wired in Delta! A case of brain fade! It is connected in star, goodness knows what I was thinking of when I said it must be connected in delta!

I don't fancy digging to find the star point on this one! If I mess up the motor then I have a fair bit of work required to get a new motor in there. it is either a rewind to get it connected in Delta, with modern insulation or a cheapie 440 volt inverter. I swore I would never buy a Chinese inverter, but maybe this is a worthwhile occasion!



Pete.06/03/2021 17:24:43
457 forum posts
60 photos

Invertek inverters start at £95, I don't know why anyone would even consider buying spending £60 on something of dubious quality when for little more you get a lot more.

john fletcher 106/03/2021 18:20:32
676 forum posts

Has any one actually had a Chinese inverter of dubious quality. I often read on HERE, a lot of derogative comment regarding Chinese made inverters, but, when I ask friends who have got Chinese made inverters, all say they work as expected and are very happy with their purchases. 20/25 or more years ago I fortunate as I able to buy some pre own inverters at knock down price, so no axe to grind. As so many car components are made in PRC or India are they also of dubious quality, I wonder. John

Steve Pavey06/03/2021 19:16:48
340 forum posts
39 photos

Firstly, to the op, it usually isn’t difficult to find the star point in a three phase motor - the first one I did was a bit daunting, but once you’ve taken the motor apart the worst bit is over.

I’ve got two Huan Yang vfd’s, both from China via eBay. The one on the lathe has been fitted for around five years now, and has always performed perfectly. I have another one on my cnc router running a 2.2kW spindle also works well, though I found out that it is a little susceptible to electrical noise from the controller and had to fit a small capacitor to the analogue speed inputs - total cost about £0.01. I have also found that Huan Yang use an unconventional Modbus standard, which doesn’t affect me at all as I don’t use Modbus.

So yes, I agree with John Fletcher - no reason not to buy a Huan Yang, especially if you just want to run a 3 phase induction motor. And I did actually look at buying something from a U.K. supplier - a 2.2kW model was £230, and apparently comes from Italy, and you can bet it is full of electrical components that come from China.

Pete.06/03/2021 19:46:14
457 forum posts
60 photos

It's the safety aspect that's most important, I'm sure a Chinese inverter is fine, as long you buy it from somewhere like inverter drive supermarket that would only sell products that meet safety requirements.

Andrew Tinsley06/03/2021 20:06:39
1343 forum posts

Hello again,

I have converted a good number of motors from fixed star to delta by digging out the star point. This motor is very specific to the drill. Not just any motor, but one with a massive integral mounting arm. I want to keep the motor as it is original to the drill. If I mess up digging out the star point then to keep originality, it is a rewind job (to delta) and that isn't cheap!

Show me an Invertek inverter that has single phase in at 240 v and 3 phase out at 440V for £95 and I will buy it. You must know such inverters cost an arm and a leg!!!!!!!!! The only cost effective inverter at this spec, will be a Chinese one! I don't buy Chinese inverters but stick to European ones, but in this case I will give it a try, cheaper than a rewind.


paul rushmer06/03/2021 20:42:24
84 forum posts
11 photos

I dont know if your drill is like my old J & S on this machine you swop the quill pulley for the motor pulley.


Andrew Tinsley06/03/2021 21:04:45
1343 forum posts

Hello Paul,

That did occur to me! I have just measured up the pulley diameters and was going to work out the speeds if one did just that. I will report back.



Andrew Tinsley06/03/2021 21:04:46
1343 forum posts

Hello Paul,

Unfortunately it doesn't work out for  the Herbert drill. It looks as though I need to make a new triple motor pulley at twice the existing diameters. There is plenty of room to get this in the existing set up. Which makes me think this was the original intention, as otherwise the pulley guard could have been made much slimmer for the existing motor pulley



Edited By Andrew Tinsley on 06/03/2021 21:26:43

Dennis R06/03/2021 22:58:08
62 forum posts
16 photos


On my Flott high speed bench top drill, the pulleys are easily swapped over, a pin spanner releases the pulley from a slotted taper.



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