mt3 to r8

just bought another mill in mt3. does anyone know if and where i can get a converter from mt3 to r8 as all my other stuff is r8? thanks

Never seen an adaptor and the sizes look to close to make one that is not overlong. A friend once stripped his mill down and turned his spindle fro MT3 or might have been MT4 to R8 dimensions. Don't think it was very good as he sold the mill on soon after.

Never seen an adapter the way you want it, fizzy. Local supplier here lists them the other way around (R8 into spindle adapting to MT3 tooling) but not your way.

I take it that this mill is not one of the newer flock of machines which offer different spindle formats?

Its a second hand mill, brilliant condition and paid very little for it. Daft thing is you can get a mt2 to mt4 adapter, bit of a step up in size there.

I've got MT4 in my Super 7, R8 on my mill. I took some quick photos to compare the taper of an R8 collet with the MT4/MT3 adapter (which is of course larger than MT3.

I think you can see that there's no way to make an MT3 to R8 adapter that will fit inside the spindle and you would end up with an overhang probably the full length of the R8 collet.

I think it would be possible to remachine the spindle to R8 which to my mind would be the best solution, it would be critical to get it right first time though.

Mike

If the machine is also sold with an R8 fitting then there is almost certainly room to re-machine the spindle to take an R8 as Mike suggests. Seems very unlikely that the main spindle dimensions would differ between MT3 and R8 versions. If an R8 option was offered maybe look into getting an R8 spindle as a spare part so you can do a straight swop. Machining is going to be tricky unless you have a decent size, very accurate, lathe with appropriate tooling and its not going to be a fast job. Objectively you could probably earn more than the cost of a spindle, if such is available, in the time it would take you to do the job.

Was asked to look into similar issue some years back on a spindle that really was a bit too small OD to put an R8 in. Concluded that the only way to do the job was to make up a permanent insert with most of the R8 contained in a cylindrical section fitted into the bored out spindle with a projecting end made larger than spindle diameter to carry the taper. Probably added about 1/2" or so to the effective spindle length with part of the taper running into the main cylindrical body. Sanity prevailed and the idea never got past the drawing board, well CAD programme actually, so things like fitting and fixing never got looked into. Shrink fit the mane body and weld round the end I guess. Finish machine in situ.

Clive.

There is no such fitting,not that I know of anyway. Be happy with your mill as it is.

I have an unused Chester 626 (still in its packaging). It has a MT3 spindle rather than R8. Do I need to worry?

Phil H

Fizzy, you didn't say what mill model it is. Is it possible that you can get an upgrade kit to convert the mill itself to R8?

When I got my WM16 lookalike here in Canada it came only with an MT2 spindle. Later the seller decided that there would be more demand for MT3 and subsequent machines had that. To satisfy existing users they sold some upgrade kits to convert the machine from MT2 to MT3.

What they didn't publicise, but what I discovered by talking to my friendly salesman, is that they also bought in a few kits to convert the machine to R8. I snapped up one of those.

The kits consisted of a complete new spindle assembly and was simple to fit.

It might be worth asking the question.

I feel that using the morse tapers on a milling machine is bad practice, morse are self holding tapers designed for drilling and reaming. To use them for milling they need the use of a drawbar which requires delicate use to hold tight enough to resist milling forces and not be so tight you have to beat it to release. Milling machine tapers are self releasing and so do not need anything more than a light tap to eject. I feel R8 is very good on small mills both for direct collets and other tooling like chucks and boring heads. Many people opt for MT as they already have MT tooling but I did not have much that I would want to use on the mill and the lathe so went R8 which is a choice I do not regret.

Mike

Edited By Mike Poole on 14/07/2017 09:29:51

Thanks everyone. Ive bitten the bullet and splashed out on a set of imperial and metric r32 collets with a mt3 draw bar chuck instead.

If you mean ER 32, I think you have basically wasted your money on one set or the other! Each collet will contract a usable 1mm or 0.040".

The imperial collets will compress by 1mm and the metric ones by 0.040" if required!

I don't agree (that he has wasted his money). While what you say is true about the 1mm range, using the bottom end of the range is a nuisance at best. And some imperial sizes fitted to metric collets are right at the bottom end of the range forcing you to do a three-handed act tightening (and tightening and tightening) the collet while trying to keep the cutter (or whatever) in position. Likewise when you release the cutter it will drop from the collet the moment you slacken the nut.

I started with an ER32 metric set years ago but rapidly built up a range of imperial collets to improve the range.

You could argue that it's not necessary to buy a full set of the second-system collets - just those needed in the worst cases but but I don't think the full set is wasted. (Especially if you have more than one machine using the same collets e.g. lathe and mill).

Edited By Bandersnatch on 14/07/2017 15:09:00

I agree, I started with a metric ER16 set for my Novamill but soon added imperial for that exact reason.

I'm surprised that no supplier offers a limited set of ER collets comprising only standard milling cutter shank sizes for pure milling machine use. Cost savings should be appreciated by typically impecunious Model Engineering / Home Workshop types. It would be no great problem to offer expansion sets to cover the full range of native imperial or metric sizes should the purchaser eventually decide to use them on the lathe as well.

I prefer the Clarkson style treaded shank cutters for un the appropriate chuck milling in my Bridgeport. I do have an ER32 set on an R8 taper, purchased following magazine advice when I got an R8 square column mill. Almost unused since I rapidly bought the Clarkson set-up following practical advice from an experienced person. Along the way I picked up native R8 collets making the ER system redundant. No use to me on the lathe as mine has a native 5C spindle. A full set of x 1/64 th imperial and half set of x 1 mm 5C covers all my needs.

Never been that impressed from an engineering viewpoint by the ER system due to the monster tightening torque needed to ensure accurate results. The can hold accurately at lower torques, especially when used with minimal compression on material whose nominal size matches that specified on the collet, but if you want specified accuracy everywhere in the range book torque figures must be followed. You won't do that with the tiddly sheet steel spanner in the set.

Clive.

No, not at all. Especially if you make a self ejecting draw bar for it. Do a google for VMC or 626 "self ejecting drawbar" and you should find a post by a German guy who made one.

I've found it very handy to be able to put MT drill bits straight in my VMC.

Does a morse taper milling spindle have a slot to eject tanged tooling? I have an R8 spindle and if I use a morse adaptor for tang tooling I need to remove the adaptor and the use the normal taper drift to eject the drill or reamer from the adaptor, OK for the odd job but it would drive me nuts if I needed to do many tool changes.

Mike

Hi Mike,

My milling machine (similar to WEISS VM-25L) has a MT 3 spindle and a slot to eject tanged tooling.

Thor