Things you’d forgotten you had – Volstro Head

[Peter Neill 1Participant @peterneill1]

Trying once again (and again failing to a small degree…) to create some order in a very overcrowded garage workshop, and as I pulled out numerous dusty things, I spotted this box hiding in the furthest, darkiest, dustiest corner of a shelf under the bench.
I bought this for my Bridgeport back in 2010, but then a year later I bought a Tormach CNC mill, so never actually got around to fixing it (it had 2 small broken bevel gears – I bought replacements, but never got around to fitting them) and of course never got to use it.
Bit of a rarity these days, and on this side of the Pond, but I expect that a few of you that have been around as long as I have will recognise it.

[PeteParticipant @pete41194]

I have the exact same head and accessories Peter.

[Pete]

On Pete Said:

I have the exact same head and accessories Peter.

Do you still use it? I obviously haven’t needed it since the Tormach, but I remember being a little desperate to get hold of one back then.

[Clive FosterParticipant @clivefoster55965]

Aaand for all the forumites muttering “Looks cool but what does it actually do?” the Volstro is a rotary milling head.

Basically a small cutter held in a collet on an adjustable slide with what is effectively a built in, worm drive, rotary table attaching it to the spindle. Moving the slide offsets the cutter away from centre line so turning the handle on the rotary device allows a groove to be cut on a radius set by the amount of offset put on the slide.

Clever device and, in certain quarters, more useful than you might think in pre-CNC days. I guess the basic party trick would be to cut a narrow rectangular groove with rounded corners of radius significantly greater than the cutter radius.

Proper exploitation and correct production of a part to a drawing needs concentration and careful pre-planning of the job so the cutter is always moving forwards. The device has absolutely no tolerance for backlash so, except in rather special cases, you can’t move backwards without wrecking the job.

Realistically these days it lives on the same shelf as a Cherrying head inspiring folk who notice them to heartfully say “Thank God for CNC.”

Clive

[howardbParticipant @howardb]

A video of a Volstro head in use.#

[Dave WoottonParticipant @davewootton]

A very clever and useful device, but as Clive says needs concentration and pre planning, used one in a large Huron mill to machine O ring grooves in a very complex casting for blanking off ports for air blast circuit breakers. It was one of the last jobs on the casting and vividly remember the sweat running off me as I desperately tried not to mess it up!

Even though I have no idea how to programme or use it I do have to agree thank god for CNC. Strangely only last summer I saw one for sale, with no tooling or collets, at an autojumble. Ashamed to say I just hurried past!

[PeteParticipant @pete41194]

Since I don’t have cnc, yes I do. I spent over 10 years trying to find one in excellent condition with all the collets and accessories. Luckily a good friend had gotten one that had been used just once and had been sitting on a shelf ever since when the original owner decided cnc would be the better and method, which it obviously would be. And he passed it along to me for a very reasonable price. Mine was in basically brand new condition. But it seems very few even know about them today.

I suspect the previous owner of yours probably tried forcing it to take larger depths of cut or feed rate than it was designed to do and broke teeth on those bevel gears you mentioned. If you already have a replacement set, and they seem to be in your picture, your extremely lucky to have bought them when you did. If you repair yours, I’d also double check the rest of the internals for any damage as well. For whatever reason I’ve yet to figure out, Volstro never added anything like a shear pin or slip clutch to the internal assembly to protect the fairly delicate parts. Other than added cost, that was at least bearable when Volstro were still in operation for spare parts. Today I know of nowhere that might have any parts at all for these heads. Since you also have the powered head rotation that uses the standard Bridgeport spindle feeds. It shouldn’t be used for larger radii towards the maximum these heads will do since that’s still a bit too fast for the feed rate. Again that creates more loads than the internal assembly was really designed for. In that case, I’d always use the hand crank for the head rotation for those larger radii. Btw, the drive belt is meant to be coiled up and then fits around the outside of the small drive pulley, there’s a depression in the styrofoam just for that. 🙂

I’m unsure if Shaublin still produce the E 25 collets these heads use, and even in North America there fairly hard and expensive to find as used collets today. I’ve heard that just before Volstro closed there doors for good, they changed to using ER 25 collets for these heads. In case you don’t know, the Schaublin E series collets were I believe the starting point for Rego Fix to invent today’s ER collets since they use the exact same body and nose taper angles these E series collets have. But for some definite reasons, there not interchangeable. Rego Fix apparently lengthened the design of the E 25 series by just over .100″, added the extraction groove on the collet, and came up with there clever eccentric nut design the ER collets snap into and get extracted with. I’ve compared my own set of Schaublin ESX 25 collets (exactly the same as ER collets) against these E 25 collets. And that added length and extraction groove are the only real changes I can see or measure. But there’s also differences in the collet chuck diameter and thread sizes on both the chuck body and nut used as well. So an ER collet nut still can’t be used on these E series collet chucks.

I believe it was probably more for getting the heads to fit those storage boxes Volsto sold as a quite expensive accessory than anything else. But these heads have what I’d call a stub length R8 shank as the drive. So you also need a different draw bar length of about 2″ longer to use these heads on a standard Bridgeport or clone that has the same 3.375″ spindle diameter. I think these heads are extremely well built for what they were designed to do, but in reality I think they were only meant more as a light weight finishing tool and mostly designed for use in tool & die and injection mold production. Cnc is what finally closed Volsto’s doors I guess.

Fwiw, I’ve no idea what your head and the accessories would have originally sold for, and as you mentioned, they would probably be also quite rare in the UK. But I just checked an old 2003 MSC catalog I still have. At that time these heads were using ER 25 collets, so that much is confirmed. But just the bare head without any collets, power feed components or that storage box was priced at $3161.81 U.S. dollars. With what we have, then certainly well over $4,000 U.S. back then. There’s some information on the Practical Machinist forums about these heads if you do a search. Some of it mine that would repeat most of what I’ve said here.

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