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Charlie Lear let me know that Mason wrote up this toolpost design in
Model Engineer, vol 136 No 3384, 2-15 January 1970 and he has made the relevant pages available on
his web page
31 Jul 2002 |
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Alternately, one can have several such holders, each dedicated to a specific tool and preset to suitable heights. Simply loosening the crimp bolt (1/4 turn on mine) will allow the removal of the holder and the quick placement of the next one. Variations can be made to hold boring bars or even drill/grinding attachments as illustated below. I already have partial drawings for a boring version, and a cutoff version, which might get mounted on a backtoolpost.
The following is my final working drawing for the post I have built.
This may undergo changes or updates as I gain experience with the prototype.
A pack of printable drawing files is available as well.
This PkZip2.5 archive contains Postscript, HPGL, PNG and TurboCAD2D format versions
of the working drawing.
I had a piece of stainless shafting handy and hacksawed off a suitable piece,
then faced it both ends. In the drawing it is shown with a recess in
the bottom end. This is to clear the 'hump' in the middle of my topslide where
wear has not occured from 40 years of using the stock ML7 tool holder. Thus
my post sits on the worn area at it's largest radius, and will sit flat and rigid.
I made a brass washer to sit on top of the stainless, with it's inner edge chamfered to match the rounded end of the toolpost nut. In the photo you can see the brass is polished to a high gloss using a buff. Not necessary, but pretty.
Stainless is not necessary, Mild steel would work just as well.
Basic operations are as follows (in order):
| Mod: 23 Apr 2003 12:40 When I made the boring holder, I offset the tool slot lower in the block to accomodate my homemade 9mm thick boring bars. Having recently purchased some 8mm HSS tool blanks I decided to mill a little more off the bottom of the slot of the turning holder. Thus the '9mm' dimension in the drawing becomes 5mm or so so that 8mm tools can be set to center height with a bit of leeway remaining. |
The almost completed block laid over the drawing. I've put the post in upside
down so you can see the recess that clears the unworn 'hump' in the center of
my topslide. This ensures that the post rests on the largest possible diameter
and is therefore as stiff as possible and does not rely on the hold down bolt being stiff.
The bar of 60x60mm BMS I cut the toolpost block off of with a hacksaw.
Won't do it again in a hurry, rather take the time to go to a friend with a bandsaw!
The endmill/slotmill just after filing and before hardening. This was made from
a piece of a 1/2" 'silver steel'. It was turned to 10mm (the size of my required slot)
then I made rough marks as guides, then cut the
basic shape with a 1mm cutting disk in the anglegrinder. Then filed to shape.
Heated to bright cherry with a LPG torch and quenched in oil. I then tempered
it a bit soft and had to do it again before a final sharpening on the grinder.
Ended up cutting slightly less than 10mm but it will do fine.
The first couple of cuts! The block is mounted with the toolpost stud through the
big hole. The topslide had to be mounted on the far end of the cross-slide for this
operation, and you can see the rather makeshift method of holding the near edge down.
The far edge has a T-slot handy. Fortunatly I made 2 T-nuts last year when I bought
the lathe, they were one of my first projects but I've never used them till now.
It was jolly handy to have them though, without having to make them for this job.
Nearly there, another millimeter to go. This was a slow process since I could only take
5 thou cuts on one direction and 10 thou in the other. It was happier in the one direction only.
Any deeper a cut and it would snag and unwrap the backlash in the crosslide leadscrew.
The carriage was locked and infeed done with the topslide.
The first cut! 30 thou in mild steel with power feed of 1.8 thou per rev and
NO chatter, not even a hint. Could have gone to 40 thou I believe. As you
can see I was too excited even to clean the blueing off before the foto!
You can also see how the brass washer is off center. This is because the stud
is bent from many years of tightening against the stock ML7 holddown. I had to
bore the post slightly oversize to allow the post to sit flat with the stud
running at an angle up the center.
From the other side. The clamp stud end is still rough. This one is temporary allthread
as I don't yet have a long enough bolt for it.
The parts. The clamping stud is temporary, as is the height adjust stud. Currently
peices of M6 allthread, I will change them for suitable bolts shortly. I have already
swapped out the 4 tool holddown bolts for hardened caphead bolts. I had to wait for
them to come from the 'big city' as they are not sold here. Maybe I'll make a brass
knurled head for the height adjust, soon as I get a knurler....
I have since replaced the height adjuster and the clamp stud with M6x50 bolts which I polished on the buff. This makes the threads much smoother than they come from the factory and the action is nice and smooth.
The smaller bar seen above is made from the bar that links door handles
through the lock. The cutter there is a piece of ball bearing casing
sliced from the outer race using a 4.5" angle grinder and 1mm thick cutoff disk,
then ground to size and shape on the bench grinder. Keep it cool!
The cutter is retained by an M3 countersunk screw in the end of the bar.
(because I recently purchased a set of M3 taps and had to use them for something!).
This bar will enter a 10mm hole whereas the longer one will only enter 13mm.
The squarish hole is for a cutter as described above that I ground too
short after many resharpenings and replaced with the HSS center drill.
I will be cutting the tail end off as soon as I need to. For the job I needed
this for (the final few cuts on the boring holder) it fitted into the hole as is.
The end of the bar was ground off so it didn't hit the jaws in the 4jaw when
I was boring the tool holders.
The recess could be left out, and the clinch bolt operated from the operator side (also tap the opposite end of the hole!), but that would interfere with facing operations so this is only feasible if another holder is available for facing/boring.
Toolpost grinders, drilling rigs etc could be made with this mounting. Even a rear toolpost with this same post on it could be made, facilitating easy tool swapping and adjustment.
10 Jan 2003
Had the idea to make a toolpost power feed attachment using this mount
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