News from a small machine shop
Don’t remember where I have found this one, but I liked the idea:
The blade needs to be «bent» in place mainly on two points (on the top right, and the opposite left). The concept of displacing the bearings in accordant way could preserve them a little bit. And given that this is a short task on the lathe…
The idea of easing up the setup of the blade alignment is really delightful. I saw this or similar mods on different places – the one I took a in depth look onto was on the ToolsandMods website.
Mine consist of two setscrews on each side of the blade guides – this way it’s possible not only to tilt the blade, but also to displace sideways the whole block. This way it’s really easy and accurate to set the blade in two angles: in the cutting direction and also in the cutting angle of the piece beeing cut.
The parts were milled about 5.5 mm down on the sides – making space for some M5-threads and offering contact points for the setscrews. Setting this part back, some clearance for the height limiting wheel is needed. I took about 3 mm – you can see this recess in the middle of the part.
I used some vee blocks to clamp the angled parts down. Don’t worry: those angles are far away from 45°, but this doesn’t matter to the later purpose. The other parts were clamped on the precision tool vice using a ball and some brass shim stock (similar setup as you probably would use to square up stock).
Beneath the usual mess with cast iron, it turned out well. This mod is really a great simplification of the setup process. It speeds it up and makes it really more precise. I really recommend this one!
Inside the gearbox, everything looked nice: no worn gears, just a tiny amount of play. I did open this already as I received the machine. Yep, with the whole mess of oil pouring out – so if you didn’t open it yet, be prepared and have some rags on hand.
Probably this was the cause of screwing this lid that much down, that I completely thinned the gasket. Well then: a new gasket with some scrap 1 mm rubber plate is done fast – and don’t forget not to overthighten the lid. I need to confess not beeing aware of the different oils and lubrication possibilities – I believe what’s indicated on the label. So far, it worked for me…
As I got some scrap rubber of cutting the gasket, I laid some underneath the junctions of the sheet metal box containing the belt and the pulley gears and the top of the cast iron arm. This really reduced the noise of this resonance box!
I really liked the idea of Jim Schmitt (on a post here) about the «inverted» retractable threading tool. Based on the concept of Charles Dolan (his post is here) it reverses the pull-handle to a push-handle – what in my opinion eases different things.
On the one hand, it’s easy to add a spring, helping to fully retract the tool completely in the right moment. On the other hand, it’s possible to let the tool clip into place by the right angle of the mechanism (and supported by the spring). This way it should be possible to cut repeatable and precise threads on the lathe.
The first sectional view shows the lever mechanism in neutral position.
The through hole on the left is tapped on the end and holds the spring. The two blue circles next to each other are the pins on the slider – the last one from on the lever.
In neutral position, the spring-rod pushes the carriage and the lever back. The lever is in the upper position.
In the activated position, the angle of the link in relation of the lever circle is slight above the center. In combination with the spring tension, this latches the setup in an safe engaged position.
Desengaging the tool needs minimal action and force – as soon as the angle drops below the center of the lever, it’s retracted by the force of the pushing spring rod.
The tool is made of 1.0570 (S355J2+C, or in the USA: 1024). This is low-carbon steel and not really made for hardening (possible tough) – don’t know yet, if this tool needs to be hardened…
Most parts were milled on the Tormach PCNC440. There were tricky ones, like the dovetails, which need to be smaller than the ones of the back of the toolholder (btw.: yes, also the little version of the dovetail cutter showed on insta works like a charm), or the small cross-section for the lever, which needed a precise angle on the top as back stop. Some screenshots from the «lever side»:
Another difficult part was the axe which connects the slider to the lever: even though it’s possible to simulate almost everything in CAD/CAM, I had to make another version – 0.3 mm longer. It worked perfectly, but in the neutral position, the slider poked out a little bit 😉
After assembly, it turned out, that two pins on the slider was overkill. One is enough – with the benefit, that a stronger ball-point-pen-spring could be used.
For those who are interested in: here are some PDF-Files of the different parts which were made:
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And some photos of the working in progress:
First: the tool works! It’s quite sturdy and won’t move while turning the thread. Though, you really have to set up «soulful» the force of the dovetail clamp. A too high clamping may block the carriage – a too low results in sloppy toolholding!
These images were taken from my next project. An M20-something with a fine thread. That was an easy task to do with this tool.
I have a Tripan toolholder system on the Schaublin-102VM lathe. It’s an «old school» quick change system with adjustable height and quite a good clamping capability. I really like the quality and the versatility this system offers – and it matches perfectly on this lathe.
Just because I live nearby where it was produced and probably mainly used, this doesn’t mean, that we could get them cheap – they are still quite expensive (we get them unused for about 85€ p.p.). Therefore and because I’d like to have a better feeling for machining mild steel, I wanted to make a run of 10-12 of them. Right: about a dozen – a mechanical artist on Instagram about that fact (Thanks Robin):
robinrenzetti Looking good, no such thing as too many tool holders. 💪👍👌
I own some original toolholders – and there are some plans with measurings on the net. So, making a CAD-file out of that material was an easy task. At the moment, my favourite CAD/CAM/Rendering program is Fusion360. Take a look – you can manipulate the image yourself:
I always like to test some setups, materials, speeds’n’feeds, etc. – even too in the production run! The prototype means the previous step for me: a first physical output, which you can move in your hands and study directly on it. Even though CAM and CAD are quite sophisticated these days, they won’t beat the physical output.
The first prototype turned out well. The dovetail cutter won’t take a whole production run, and there were some «design issues» – but technically the «proof of concept» was done…
For machining this little piece, three different setups were needed. If you make a production run and have the stock-pieces in the same dimensions, you can ease your life by indexing them in on the lower back inset – this way, you don’t need to bother about heights (you set them in the CAD-program). The mentioned setups are:
As mentioned above, on the first try I noticed, that tool wear would sooner or later be a issue on the production run. The dyi-dovetail-cutter solved the problem (and lasts till today – after a dozen of dovetails milled).
By the way: the width of the dovetail isn’t that critical in my opinion. On the drawings I mentioned before, really tough tolerances are given. But finally it defines the way the base lever (on the Tripan 111) has to travel – nothing significant for working with it.
The back surface (image above: on the top)
… not finished yet. To be continued…
For my Tripan-toolholder-project i needed a 60° dovetail cutter. I got one which worked really great with the prototype:
After inspecting the work and the tool, I saw a beginning wear in the tool. Those tools are to expensive to get them stub after 2 or 3 parts. So, I thought about an indexable tool – but they are even more expensive than the solid ones! Consequence: make an own one. Continue reading “Dovetail cutter”