Denford Starmill - replacing spindle

**Doddy** · 17-12-2015

As always, solid advice. I had thought of slaving a second spindle on the side of the column - the bed is over-long for the available travel, so that might be feasible (I thought it originally too silly, but to have another suggest it gives me more confidence). Only problem is the available height of material (cast iron?, I think) to mount the motor bracket is around 20mm, and I'd have to be careful not to drill/tap into the bearing that it holds... I could probably fit an additional stabilising bracket higher up the enclosure... I'll think about that.

A new head housing?, Hmm, I need to get into the shed tomorrow (maybe saturday, drinks with the lads tomorrow) to have a look at that. I won't be able to machine that myself, but I've had satisfaction with help given by others on here before now.

I'm thinking, I've got stock in the shed to make a couple of custom mounts so I might tinker with a second/slave spindle in the first instance.

Thanks Jazz.

**andy_con** · 17-12-2015

trouble with starmill and novamill is the way the spindle motor is integrated into the head.

unless you get a replacement motor of exactly the same size you will lose z travel.

although a small machine and small motor, it will blow these cheap Chinese ally framed mills out the water, so don't put it down. can you provide some photos of exactly which model of starmill you have and any photos of motor and head if you have taken things to bits?

are you aware on certain models you can raise the head on a starmill and novamill?

**Doddy** · 18-12-2015

@andy_con:

Either solution - slaved second spindle or replacing the head housing - I'd look to leave the original spindle motor in as a dead-weight counterbalance, the new chinese water cooled spindle being directly mounted in place of the spindle (or offset). I don't see any impact on Z travel.

Re. frame, yes, it's a stiff little bugger. I'll try to get a photo over the weekend - but it's a bit of a hybrid - the previous owner removed the ATC at some point, reworked/refurbed the spindle and bearings).

Raise the head? I'm not sure I understand what you mean... maybe a photo is in order

@JAZZCNC:

With the limited y-travel I'm pretty sure that I couldn't mill the complete back bracket as a one-er, so it'd be a challenge to get the two sides to the dovetail perfectly parallel, and factoring in the gib strip. Also, if cutting steel, it's a big lump for a small machine. Maybe I'm making excuses and avoiding the hard work. I did have a quick look out for any machines being broken, and will probably keep an eye out, but these things are getting a little rare.

@andy_con (2)

I've not got to the motor - it's inside the casting, I could make an effort and break it down, but the laser/IR RPM thing I have claimed just shy of 3k.

@uli12us:

Replacing the existing spindle with a new one?, it's do-able, and probably a whole lot easier. I might ponder this option. I would prefer a much bigger collet system - ER20 or ER25 would work (and I have ER25 collets); but, it's easier to source a spindle motor than a spindle. Okay, I have a lathe, so it could be a winter project to turn a spindle myself (and somehow mount the collet holder, whilst maintaining a level of precision). Interesting option, though I fear more complex than the alternatives. I'd like to retain the strength to cut metal, so nothing too small... I'll have to go into uncharted waters and look at bearing options.

Okay, I'll try to remember to post pictures fri/sat, see if that helps ideas to converge.

**uli12us** · 18-12-2015

No not replacing, the existing spindle remains still in place, but you have a special toolholder with ballbearings in it and a small beltdriven spindle in the middle of the holder, like in some older manual engraving machines.
If I read it correct, you have a BT35 spindle. that holder should have some 38mm diametre. with a 1" bore you can have a spindle with 1/2" diametre.

**Doddy** · 18-12-2015

Originally Posted by uli12us

No not replacing, ...

Cooer, that's interesting. The Z-travel on the star mill is pretty good for such a small machine... I have a couple of BT45 toolholder that could be adapted for this. I already have a crude spindle-lock that would hold the existing spindle in place... hmmm, that's an idea that I hadn't considered, and could be appropriate for simple flat plate milling/drilling. Let me have a ponder and play...

**uli12us** · 18-12-2015

Here is a ebay auction, where you can see, what I think of it.

But the peek of the spindle, should turn 180°

http://www.ebay.de/itm/Graviermaschi...gAAOSwv-NWbloo

A part similiar to this, with an added pulley rotates inside your
toolholder

http://www.ebay.de/itm/ER11-12-x-100...EAAOSwl8NVV~vL

**andy_con** · 19-12-2015

thinking about it, the novamill has a slightly different motor, its 5000rpm.

the starmill and novamill have the same column design and size, so a novamill motor would probably fit.

problem with adding a high speed spindle is the angular contact bearings in the head. angular contact bears are open, so when they get warm/hot the lubrication runs out, so they don't last long. to work properly and last long at high speed they need constant lubrication.

ive just replaced the spindle bearings in my denford triac, with lubrication they are rated at 26k rpm. but they aren't lubricated, the stock motor in there only runs at 4000rpm so they will be fine.

**JAZZCNC** · 17-12-2015

Originally Posted by Doddy

A new head housing?, Hmm, I need to get into the shed tomorrow (maybe saturday, drinks with the lads tomorrow) to have a look at that. I won't be able to machine that myself, but I've had satisfaction with help given by others on here before now.

Why not it's only back plate with a simple pocket then a Dovetail cutter up the sides and you have a working Mill to make it with.?

Then just space the Spindle off the back plate. Go the whole hog and space it off with Rotary table and you'll have capabilty to machine on 3 sides.!!!

**andy_con** · 17-12-2015

also what does it say on the side of the motor as I'm pretty sure my starmill is 4000 rpm

**uli12us** · 18-12-2015

What, if you built a special toolholder with small ball bearings they are capable of some 30.000 turns.
In this you have a small spindle with ER11 or so collets.
On the outside you have a small pulley. then you only need a standard motor with a big pulley 10 times the diametre of the small pulley and a belt as link between them.