Morse taper grind

[justin0785Participant @justin0785]

Can anyone recommend a place to get a morse taper cut into the existing spindle of my herbert ov milling machine. The current taper is similar to R8 but impossible to find tooling for now

 

[Andrew CrowParticipant @andrewcrow91475]

First question, is the spindle hardened? If not you could possibly machine it yourself and probably would be better to make it R8 or perhaps No. 30 International.

Even if it is hardened by getting it ground to any other taper it would probably remove the hardened surface anyway as it would most likely be case hardened which would only be about 30 to 40 though deep.

Andy

[Andrew CrowParticipant @andrewcrow91475]

As a second thought, with the right grade of carbide insert you could probably remove the case hardened surface anyway. Obviously your finished spindle would be soft, so extra care needed when fitting tooling. The international taper might be better as you have a positive drive from the dogs.

[Clive FosterParticipant @clivefoster55965]

There is an older thread discussing this taper problem. If I recall correctly a favoured solution was to convert to R8 by boring out the end of the spindle to take a short cylindrical slug with the R8 closing taper inside. Presumably held by loctite. I imagine the spindle bore needed to be taken out a bit further up to accommodate the cylindrical, stabilising, section at the end of an R8 too.

Having all the operations on the spindle simple turning jobs seems a bit safer than converting the taper. Producing the insert is a straightforward taper turning job too.

Clive

[Howard LewisParticipant @howardlewis46836]

If you can measure the taper (Major diameter, Minor diameter and length, you may be able to work out what it is.

Yours is not full length, so no point id quoting all the dimensions for INT 30, 40 or 50.

But if it is any help the major diameter for INT30 is 1.25″, INT 40 is 1.75″

If the taper works out at 3.5 inches per foot, it will be an International Taper (Which is what I would expect of a Herbert milling machine.)

Howard

[JasonBModerator @jasonb]

It’s a small mill, the taper was R0

[John MCParticipant @johnmc39344]

I made a new spindle for my Herbert 0V, used tapered rollers rather than the ball bearing arrangement.  I made the new spindle with a 4 morse taper.  I think that is better than the R8 taper, a better (more rigid) connexion between spindle and cutter/chuck and no weak key.  The 4MT allows larger milling cutters and drills to be used, something the 0V is quite capable of using effectively.

Getting back to machining a new taper into the spindle, its hard but not hard enough to trouble carbide tooling.  Problem will be the size of taper.  3MT is too small, the bore of the spindle is too big.   A 4MT would be too big, spindle not big enough in outside diameter.  The attached photo shows this.  (Herbert spindle [bottom half!] on the left, 4MT on the right).  A new spindle is thee way forward.

Whatever taper is chosen, I would finish it on the machine to ensure absolute accuracy.  Assemble the spindle into the head, clamp a boring bore vertically on the work table.  Tip the head over to the half the taper angle.  Lift the worktable to machine the taper.

Anyone interested in buying a Herbert 0V?  PM me.

(Apologies for the blatant advertising).

[ZanParticipant @zan]

If machining the spindle in situ, it will be difficult to get the angle spot on.  I suggest somehow mounting a dummy nose  to test it out and only do the spindle when all is ok

[old martParticipant @oldmart]

It might be possible to recut the taper to R8 dimensions in a lathe with carbide tooling, or if you are ambitious get an R8 spindle and make it fit.

When the museum was gifted a Tom Senior light vertical the problem was that all the mill tooling was already R8 for the other mill we had and the TS was tiny MT2. I got a short replacement R8 spindle for one of the Chinese mills that ARC used to sell and married it up to the top part of the TS spindle which has drive splines on our particular version. Also a threaded adaptor to fit on the bottom of the TS quill to accomodate the larger taper roller bearing needed for R8 which only lost about 25mm of Z height. The top bearing is a new standard replacement for the existing taper roller bearing.

 

 

[Pete RimmerParticipant @peterimmer30576]

It was my Herbert 0V that was converted to R8 by the late (but still great) John Stevenson. He drew up the two collets to compare them and said that he could do it by boring the spindle taper to be parallel then shrinking a slug of EN24 (I think) into it and then cutting the R8 taper into that. This is exactly what he did. He also made a 7/16″ drawbar ever so slightly smaller to fit down the spindle but still draw in the R8 collets.

Here are some pics you might find useful:

 

[Pete RimmerParticipant @peterimmer30576]

Truing the taper was actually very easy. I just tilted the head over to the R8 taper angle, set a lathe toolpost on the table with a HSS tool on the centre line of the spindle and used the knee to turn the taper with the motor running. It worked a treat.

[old martParticipant @oldmart]

I forgot to mention that the top splined original part of the spindle was bored for 3/8″W and I just managed to ream it out to 7/16″ with a hand reamer extended with a silver soldered steel shaft. Reamed from both ends it passes a 7/16 standard drawbar with minimal clearance.

Lathes UK does not have Herbert listed in the milling machines, but does have prints of the manuals available.

[John MCParticipant @johnmc39344]

Looking at the drawing showing the conversion to R8 collets.  I think that it is not only unnecessary, but undesirable to fit a sleeve inside the spindle nose.  Putting a rule across the business end of the Herbert spindle, it looks very much like there is enough metal to do the job without sleeving.  It would mean that the collet would sit deeper into the spindle so the spindle nose can be usefully shortened.  With the 4MT spindle I made I gained around 1/2″ extra height on the Z axis simply by making the overhang from the bearing as small as possible, a point missed by a previous poster.  That 1/2″ might not seem much, but its been a “lifesaver” on several occasions.

(Later,I modded the Z axis feed screw nut to give another 2″ of space under the quill, and still seemed able to use up all the available travel!).

I would urge the OP to steer clear of R8 collets, as I said before, too restrictive on cutter size.  The 0V is a very rigid machine capable of shifting metal quickly and accurately, R8’s would restrict the machines performance.

[Clive FosterParticipant @clivefoster55965]

John MC

Presumably the slug fitted by John Stevenson was a way of getting a harder wearing surface for the collet closing taper than the native spindle material. Opening up directly removes any hardening.

Readily available MT4 collets go up to 25 mm / 1″. Whether that is useful improvement over the maximum 22 mm / 7/8″ bore possible with a good quality R8 systems is a question for the user. That said 3/4″ is generally considered a more prudent maximum for R8. According to Mrs Google MT4 collet systems use a 16 mm drawbar so the Herbert spindle would need to be bored out.

Realistically both MT4 and R8 can be engineered to work well. As ever with this sort of thing what you do is ultimately constrained by available resources when deciding on best way for me. I imagine John considered the R8 taper slug and fractionally trimmed down drawbar more practical than boring out the spindle for a larger drawbar.

If I were doing an MT4 conversion I’d finish off the new bore with a reamer. The extra expense if one isn’t to hand (I have one actually!) would probably push me to  Johns R8 slug method.

Clive

 

[Nick HughesParticipant @nickhughes97026]

Back to the original question. I can recommend these guys :-

https://www.technovaprecision.com/#home

Although I’ve only had INT40 and 50 size spindles refurbished, they do work on the smaller spindles and so worth having a chat with them.

Beware though, using a specialist may make the conversion prohibitively expensive.

[Clive Foster]

On Clive Foster Said:

John MC

Presumably the slug fitted by John Stevenson was a way of getting a harder wearing surface for the collet closing taper than the native spindle material.

IIRC The spindle had a slug inserted because the Herbert collet was wider at the front than the R8 collet so there would be no bearing where it is required the most – right at the big end of the taper.

[John MCParticipant @johnmc39344]

I checked that.  The existing spindle will clean up to R8 dimensions some 5mm form the end of the spindle.  This will bring the point of load usefully closer to the bearing that takes the cutting forces.

As for wear, that’s unlikely to be a problem for home workshop use.  Especially as the spindle is already made of some decent steel anyway, case hardened or not.

In structures that need to be rigid, interfaces need to be avoided as much as possible.  Will it make much difference here? I don’t know, but why bother when its unnecessary?

[John MCParticipant @johnmc39344]

An R8 collet can hold up to around 7/8″ diameter but it will only be clamped over (approx) 1″ of collet.  The parallel bit will not be doing much to support the tooling.

Compare with a 4MT collet.  My set typically,  give 3 times longer clamping length than an R8.  Various collet chucks and inserted tooth cutters I have utilise the full length of the 4MT.  Therefore a much better location for tooling.

As for the drawbar thread, 4MT seem to use, generally, 5/8″ or 16mm threads, I make adaptors to suit a 12mm threaded drawbar.  I drilled the splined end of the Herbert spindle 1/2″ to accommodate this.

[JasonBModerator @jasonb]

I suppose the other thing to consider is the availability of R8 vs MT4 shank tooling. If you want to be useing ER colets, shell mill holders, saw holders, boring heads, etc then R8 is likely to be more plentiful. Though if you are the type that likes making tools doing your own with 1″ parallel shanks to fit a MT4 collet will be easier than replicating R8.

[Pete RimmerParticipant @peterimmer30576]

MT4 tooling is a lot harder to find than R8 (especially the ones with driving flats), and personally I would not consider it for the little 0V spindle as it will leave very little wall thickness on the spindle near to the step-changes in diameter which are already stress risers. By comparison, the Herbert collet and R8 collet are very similar.

 

[John MCParticipant @johnmc39344]

That is why I made a new lower half of the spindle.  Larger tapered roller bearings for better support.  The lower bearing positioned much closer to the end of the spindle (for better cutter support) along with an oil seal to keep the oil in (rather than grease).  Along with a much better adjustment to preload the bearings.

Because the tooling is held in with a drawbar, no need for a tang (driving flats?).  Occasionally I use larger drills, biggest being 1 3/8″ diameter,  no slippage.  The problem I have with larger drills is the lack of power, often quicker to use a boring head.

As for availability, 3 and 4 MT tooling is as readily available as R8, 5C and International tapered stuff.  Similar prices at the cheaper end of the market.  Put another way, I have bever had any trouble sourcing 4MT tooling.

Getting back to the OP’s original ask.  I’m familiar with “Technova’s” (Nick H’s suggestion) work, very high quality with a price to match.  Never the less, worth asking.  “Spindle solutions” might be worth asking.

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