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Alexander Master Toolmaker

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Andy Pomfret 112/05/2021 21:41:28
18 forum posts

I'm the lucky new owner of an Alexander Master Toolmaker milling machine. It came with the horizontal overarm and arbour, the standard vertical head, the self-powered high-speed head, and a rotary table which might not be an Alexander (doesn't look exactly like the ones in the manual) but which is similar in form. It's my first milling machine, and I'm really looking forward to getting acquainted with it!

However as it stands it has the massive two-speed 415V main motor. The motor is in good condition, but generating 415V three-phase for this one machine looks a bit silly cost-wise compared with a new dual-voltage motor and VFD, which would also get me a soft start and (if I ever needed it) finer speed control. I know that other folk have done this kind of conversion - so, is there anything I should be aware of? I imagine I'll need to machine a new pulley and find a way to mount the new motor. Ideally I wouldn't make any irreversible modifications. Any tips? Bear in mind that I probably won't have a mill, though in a pinch I could drive the old motor off 240V at 29Hz to take part in its own replacement.

The other thing is that the high-speed head appears to be the older pattern that takes U2 collets but with the 14.5x1.2mm Löwenherz thread. (I haven't confirmed that for sure just yet.) It came with no collets. My immediate thought is to grab a bit of EN16T and make an ER20 collet chuck with an outer profile and drawbar thread to match the U2 profile, which should be within my capabilities. Is this a bad idea for some reason I haven't considered?

I'm a relative newcomer to this wonderful hobby, so any advice from those with more experience than me would be gratefully received.

Many thanks!

Steviegtr12/05/2021 22:49:02
2224 forum posts
311 photos

Cannot answer question 2. But the motor. Have a good look around at motor suppliers. I recently changed the motor on a Tom senior mill. The motor frame size was obsolete. So i made an adaptor plate to fit between. If you are lucky you will find the correct frame size you need. It is all about the shaft size & then the motor mount . Most motors will have a shaft length you can work with. Hope this helps.


Andy Pomfret 113/05/2021 16:45:53
18 forum posts

Thanks Steve. I don't think I'll find anything that's a drop-in replacement, it truly is massive - it's a 1.5hp motor but it has an enormous 1 1/8" shaft and a huge mounting foot. I might be able to sleeve the pulley and cut a new keyway, perhaps.


Oldiron13/05/2021 17:20:48
829 forum posts
23 photos

Have you checked the motor plate to see if it is dual voltage 230/415 if so just put a VFD on it. If not a conversion to 230v should not be too difficult. You could use a slotted bush to reduce the pulley bore size if you do not have the means to cut a keyway.


Dave Halford13/05/2021 17:27:20
1657 forum posts
19 photos

I bet tramming that will be fun.

Nigel McBurney 113/05/2021 17:51:15
910 forum posts
3 photos

If you replace the main motor ,I would suggest fitting a new 2hp motor,Horizontal milling can take a lot of power.

Andy Pomfret 113/05/2021 18:19:55
18 forum posts

The motor is 415V only, and is dual speed so rewiring would be almost impossible sadly. I'm fairly new to machine work but I'm an electronic engineer so I'm fairly confident with the electrical side of things.

Tramming... yep. The manual confidently predicts that it should "take only a few minutes" to tram the table. The procedure is easier than tramming the head but it can be out in three axes!

Yes I've been looking at 2hp motors. The price difference is so marginal that I thought I might as well.

Charles P19/05/2021 16:19:11
12 forum posts

When it developed a fault I replaced the two speed motor three phase motor in my Maho MH600 with a 2HP three phase 1500rpm one and an inverter drive. Wish I'd done it years ago. Bloody marvellous.


Charles P19/05/2021 16:21:20
12 forum posts

And tramming is a two stage process. One to get the table level in both directions and one to set the head. I use a brand new solid brake disc clamped to the newly level table to help with the second stage.


Andy Pomfret 119/05/2021 16:42:09
18 forum posts

Thanks, I'd figured out the tramming process but the brake disc is an excellent tip.

When it developed a fault I replaced the two speed motor three phase motor in my Maho MH600 with a 2HP three phase 1500rpm one and an inverter drive. Wish I'd done it years ago. Bloody marvellous.

That's good to know! Did you have to fabricate a new motor mount, and if so do you have any tips? I was thinking of getting some bits of 15mm steel laser cut and welding them up. Also did you retain the two speed arrangement, and if so how? I'm looking at perhaps using a 6-pole motor and running it at 37 or 75 hz to get the two speeds.

noel shelley19/05/2021 19:43:20
707 forum posts
19 photos

For an adaptor plate use countersunk socket head bolts, hopefully none of the holes will clash. But why not use the original motor that was intended for the job and a 415 converter ? There is very little to go wrong ! The modern thinking on VFDs is fine if you need variable speed and all the other tricks that come with it, but as you have a good motor that fits why change it ? Noel.

Andy Pomfret 119/05/2021 19:54:47
18 forum posts

I'll need a bit more than an adapter plate - it's hard to overstate just how huge the existing motor is, for a 1.5hp motor it is absolutely massive. A modern 2hp (1.5kW) motor is so much smaller that I'd need to raise the mounting foot by about 50mm to avoid having to fit longer belts and modify the belt guard! That's why I'm thinking of fabricating a new mount as being the path of least resistance.

Size is one of the reasons I'm considering a motor swap, the motor sticks out quite a bit at the back of the machine and I'll save a few inches in a cramped garage if I swap to a smaller unit. The other reason, frankly, is cost; I can get a new motor and VFD for less than the cost of a decent (i.e. digital or rotary, not static) 415V phase converter. Crazy but true. If I do the swap I'll keep the old motor and make sure I do nothing irreversible though, I like the idea of being able to restore the machine to "as built" condition.

Oily Rag20/05/2021 12:29:21
460 forum posts
147 photos


The Deckel U2 collets are also used in the Deckel FP1 universal miller and in the Deckel / GHA SO series of cutter grinders. I believe they are also available and used by Vertex in one of their offerings. Advertised on Fleabay for around 20 bananas a go.

Alternative to using a brake disc (which may not be truly parallel and flat) look out for a large bearing outer ring - I use a 10" odd diameter scrap bearing outer ring for tramming my swivel and tilt table on an AcieraF3. But then again the Aciera also has taper pins to quickly locate the 'zero' in all axes.

Enjoy your Master Toolmaker - a fine machine. Have you got the 2 axis 'quartering' table to go with it? Very useful for doing Bevel gears!


Andy Pomfret 120/05/2021 13:02:16
18 forum posts

Hi Martin,

As far as I have been able to ascertain, the "normal" 16mm U2 collets have a full M16 thread whereas the collets that the Master Toolmaker uses have a weird 14.5mm 1.2mm pitch Löwenherz thread. I'm going to have a go at cutting such a thread on the end of a bit of scrap aluminium (on my imperial lathe, should be fun) to check that that's what the captive drawbar accepts - I can think of no other way of finding out short of disassembling the spindle! I could keep my eyes open for the correct U2 collets but I already have a full set of ER20 so an adapter seems like an attractive idea if I can make a decent one.

By the 'quartering' table do you mean the table that's angle-adjustable? If so yes, it's the only table I have (and it's actually adjustable in 3 axes, it swings and it tilts both ways). I can think of several applications for it, though as others have pointed out, it might take me a while to become proficient at tramming it quickly if I do make use of its adjustability! The previous owner of this machine also did a couple of larger jobs without the table, bolting work directly to the T-slotted vertical 'table' (apron?) to which the horizontal table attaches. Lots of possibilities.

I'd assumed that a new brake disc would be ground flat and parallel, to avoid noise and vibration on braking, is that not the case?


Oily Rag20/05/2021 14:48:04
460 forum posts
147 photos

Hi Andy,

A brake disc is not always guaranteed to be perfectly flat and true - remember pads 'float' in their calipers so that they can adapt to out of trueness. From memory discs have a tolerance of 50 micron (0.002" ) with regard to trueness. A bearing ring will have a couple of micron tolerance so are far more accurate.

The vertical back table I refer to as a 'platen table' - the swivel and tilt table bolts to this 'sub table' - the 'quartering table' bolts to the platen after removing the main table and allows swivel on the X axis but will also allow an up to 90 degree tilting action. The Aciera accessory then takes items such as the simple or complex dividing head onto this tilting table to allow die sinking work but also useful for bevel gear generation.

The U2 collets for the GHA SO clone grinder are, from memory at least, 'sagezahn' (sawtooth profile ) similar to the Schaublin W20 collets with a 5/45 flank angles (the Schaublin being that international metric standard of 19.6mm dia x 1.66mm pitch! ). I will check my GHA clone when I get the chance. It is quite possible to make a ER collet adaptor - but it needs to be done in a single setting to get the ER nut thread / collet bore / shank concentric. And best to make a 'plug' gauge for the collet bore prior to commencing the job, ask me how I know that!!!


Andy Pomfret 120/05/2021 15:21:18
18 forum posts

Thanks! No idea where I'd find a bearing ring. I'll keep my eyes open though.

I'd thought of machining the ER taper first with the part choked up in the chuck (the blank will fit down the spindle bore) and making up a plug gauge with an accurate centre hole, so that when it's finished being a gauge I can fit the plug into the ER taper and then turn the remaining features between centres. I like turning between centres because, as an "ambitious beginner", it allows me to take the part out of the lathe and test fit threads and tapers without losing my setup or needing to invest in more measurement equipment! Let me know if that's a bad idea for some reason I haven't thought of. And yes, I'm a big fan of plug gauges and "go/no-go" gauges and things like that. As a hobbyist I have more time than skill, might as well make that work for me. Any ideas for getting a good finish on the collet taper would be welcome - can't really lap a cone, and I don't have a toolpost grinder.

My information on the thread profile came from an old Practical Machinist thread on the GHA high-speed head. The collet is referred to as a Lorch B, and the weird thread is discussed at length. It might not be correct though!


Oily Rag21/05/2021 10:49:56
460 forum posts
147 photos


Bearing rings can be blagged from M/c Tool rebuilders where they have replaced a worn bearing - that's how I got mine.

Your production method seems very reasonable - I did mine by gripping in a set of bored soft jaws on a sacrificial 'tail', then using a bed mounted steady on a part which was not crucial. The collet taper was bored off the top slide after setting to the correct taper using a 'slave' ER chuck and clocking. The finish was good enough not to need grinding. The main point, as has been mentioned in other threads concerning ER chucks, is to get the concentricity 'spot on' between the collet taper, the closure nut thread, and in the case of a W20 to ER adaptor the outer locating taper. Yours will need the outer locating taper of the U2 to be substituted for the later.

I'm not so sure the GHA high speed head didn't use a different taper to the 'normal' Deckel taper, or potentially a reduced thread diameter on a 'normal' Deckel long body collet - I have a nagging suspicion that the high speed head only accepted smaller cutters than the standard head, which makes sense as you only need high speed for small cutters! Or because the captive drawbar in the high speed head had a small thread diameter so as to keep spindle size diameter down. The high speed head on the Aciera has a very complex captive drawbar arrangement which can be a PITA as the upper end of the drawbar is only 10mm diameter, but the lower end accommodates the female 19.6mm x 1.66p thread. I'll dig out my SO grinder collets today and check them.



Simon Williams 321/05/2021 12:10:09
605 forum posts
81 photos

My Deckel S0 grinder uses U2 collets, which are 20 mm OD and have a 20 mm x 2 mm pitch thread on the tail. And yes it is a sawtooth thread.

I've bought these collets from Rotagrip. If you look on their website you'll find them, look under "Milling Accessories", then "cutter grinder". They don't always have all bore sizes.

Not sure this helps you of your collets are a different diameter?

Best rgds Simon

Oily Rag21/05/2021 12:13:57
460 forum posts
147 photos


Thanks for the verification of the SO grinder collets. Now if anyone needs any Thiel collets I have found a box full lurking in my shed!


Andy Pomfret 121/05/2021 12:21:31
18 forum posts

Thanks Martin!

I'd also thought of relieving the rear portion of the U2 taper on the adapter so that it only seats near its outer edge. My thinking was that it's not actually closing a collet, it's just ensuring concentricity and providing lateral stability, and so I'd rather ensure that the tapers definitely meet near the end than risk a poor fit in the other direction which would lead to the contact between the spindle and adapter effectively being further from the tool. If that makes sense.

The high-speed head accepts very significantly smaller cutters than the regular head yes, the regular head being MT4!

Thanks for the info Simon - I've measured the bore on the high-speed spindle and it's a shade over 16mm so they're definitely not the same. The best lead I have so far suggests that the drawbar thread is likely to be 14.5mm x 1.2mm pitch Löwenherz (53° 8′ pitch angle), but other 16mm U2 collets do seem mostly to have a full 16mm thread or else a sawtooth thread, so I guess I'll just have to experiment until I find a thread form that fits - I can't think of a way to measure the captive drawbar thread. Doesn't help that there's a key in there too so I can't just thread the end of a bit of bar and see if it fits, I've got to cut a keyway too (although I suppose for a quick test I could just hack away enough material to avoid the key, rather than cutting an accurate keyway).

I'm still holding out hope that another owner of a GHA high-speed head will pop up and tell me definitively what the necessary thread form is! :-D


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