Tos FN22 milling machine (Deckel clone)

[RichardM]

A great solution to the problem, Pete. The only thing that I might have added would have been some magnets to collect some of the grinding debris., and a vacuum cleaner.

I find that soaking the cloth in water (with a plastic sheet taped to the machine underneath it) helps too.

 

[paradipiro]

I had a visit from @Dcal yesterday and he helped me tackle a job which I've been wrangling over for a while now. This machine uses a MT4 taper in the main horizontal spindle and vertical head spindle. Like many industrial spec machined of it's day it has a pocket in the front of the spindle with driving flats which provide positive drive for whatever tool is held in the taper. The benefit of this is that there is no danger of ever spinning a taper and trashing the spindle but the down-side is that the tooling is very uncommon. Modern MT4 taper tooling is fairly accessible but none of it has the extended nose and driving flats. Not having the flats is no concern to me but what IS an issue is that every bit of non-extended
MT4 tooling I have tried hits the end of the spindle nose before it engages in the taper, so it simply can't be used. I have a very nice Kaiser boring and facing head which I cannot use on this machine because it will not seat in the spindle taper - it's close, but just not quite enough.

The solution, which might seem unpalatable to some but not so much to me (this is going to be a working machine after all not a showpiece) is to shorten the spindle nose somewhat so that is what we did.

We blued up a new MT4 taper and seated it in the spindle then scribed around the outside and measured it with calipers to get the seating diameter right at the end of the spindle taper socket. Then we measured the diameter of the standard taper end (on several pieces to get an average, which actually turned out all within 0.15mm). We marked a line on the taper gauge at this diameter and then measured the distance between the two lines, This showed that the standard modern taper stuff I have would seat with approximately 10mm of taper poking out the you could add in the distance from the taper to the back of the tool (usually 2-3mm) and that would give you the maximum depth of driving pocket so this stuff will fit (the pictures later will show the problem more clearly if this is difficult to follow). The pocket itself was 15mm deep so to achieve this we'd need to cut 5-6mm off the end of the spindle. I went with 6mm for comfort as these measurements are not easy to take.

I also had previously checked how deep the driving flats of the arbors I have here went into the original pocket and it was more than 10mm on most, so if we cut it just right we should not only create clearance for the non-extended tooling you can buy today but also maintain some drive engagement for the horizontal cutter arbors which do use a lot of torque when working and would be the most likely to spin the taper.

So, how to cut this off? The spindle is fully hardened and interrupted cut so turning it off whilst possible cermet would probably be slow and expensive. Parting with carbide not an option so I went with what we had at hand and used a mini grinder. I have a nice heavy duty Metabo on here which we bolted to a block of steel then clamped the steel block onto the mill table with a large cast iron spacer underneath using the clamping kit. We squared the grinder up with the travel and used an extra clamp to spring the unit downwards to hold the cutting disc plumb with the spindle face too.

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We'd already taped over the top of the machine, so we covered as much as we could with sheeting, put a piece of metal on the sheet so the sparks didn't set fire to it, fired up the grinder and with the spindle turning slowly very carefully fed the cutting disc into the spindle using the x-axis feed.

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The cutting didn't take long and a quick check showed that the results came out just about perfect. You can just about se the end of the MT4 taper in the gap so the measurements were perfect. The boring head now fits in the spindle taper and so does the MT4/ER32 collet holder I have bought. I also have other tooling such as drill chuck arbors which I can now use in the spindle.

View attachment 443008

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I tried a piece of original tooling in it and yes it does still engage with the driving flats by a few mm so that was a success too

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Most of the grit and iron dust was caught in the cloth cover, but the machine is getting a thorough clean anyway.


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Finally I wanted to improve the finish on the end of the spindle. The disc did cut through right on line but it doesn't look great and the thin disc inevitably has some flex especially at the start of the cut so we set my Union grinder up on the table, dressed the cup wheel and used that to grind a lovely flat face on the end of the spindle, then applied a tiny chamfer using the same.

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Here's the finished job. I'm very happy with how it has come out. Just got to do it all over again with the vertical head spindle.

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Impressive! On the down side, the vertical spindle is only extends around 4-5mm from the quill bar, so there is not much to cut off.

 

[Pete.]

Impressive! On the down side, the vertical spindle is only extends around 4-5mm from the quill bar, so there is not much to cut off.

I have done a quick survey and I think it's just about enough. Find out in a couple of weeks when I get the grinder out.