It's time to get a quick change tool post for my Super C3 mini lathe.
I've looked at the made to measure holder at ARC Eurotrade and two possibilities from RDG tools which would need a simple mod to fit.
Arc C3 Quick Change Tool Post Set (£43.96) Two thirds down page here:
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HBM Quick Change Toolpost Ref: 2051 (£56.17) & Dixon Type Quick Change Toolpost Ref: 725MYFORD (£66.07) First two items here:
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I saw the hardened and ground Dixon Type from RDG tools at Alexandra Palace yesterday and it looks very nice, but might be a bit big on the C3. I also saw the ARC tool post on the Super C3 displayed at the SMEE stand and it appeared to do the job. The chap at the RDG stand told me about their HBM tool post, although they didn't have any with them. Although cheaper than their Dixon type, he sais it was a better design, the only down side being it was his own design and so parts were only avail able from him.
Can anyone offer advice on these or other suitable Quick Change Tool Posts for the C3?
My two genuine Multifix Suisse A sized tool posts and the 17 tool holders I have with them cost me _nothing_ Heh Heh Heh :-)
They are old and worn and need replacement cams bought or probably made, but they're still a bloody good system. The only major flaw in the design is the
40 positions. 36 or 48, even 42 would be far more useful.
I've used the ArcEuro on the SMEE lathe. It works fine, though you need to do a little bit of fettling with a file to get all the tool holders to engage and release cleanly and the Allen key release can be a tiny bit fiddly.
The most important thing to bear in mind is that the maximum diameter you can turn on these lathes is limited by how far back you can get the tool tip in its holder. The cross slide is stopped from coming back far enough by contacting the back of the feed handle carrier - It's a design problem on all of these mini lathes. If the tool post you get is any bigger than the ArcEuro one it may put the tool tip even further forward and make turning anything above a couple of inches diameter very tricky.
Back 12 years ago, when I got my mini-lathe (old version of the C3) I found that the cheapest QC Toolpost was one by GROZ, although I had to open out the fixing hole. I've not seen them advertised recently, although one of the stands at the show in Gloucestershire last August had one for sale very cheaply. I see that some people have made their own see :
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They might be easier to make than the other types and they work fine on the mini lathe. If they aren't available and you aren't interested in making your own, then I would go for the Arc Euro offering.
Thanks to everyone for the useful pointers. Norman: Very good point about making sure the tool post isn't any bigger than the ArcEuro one. Thank you. That's exactly the kind of mistake I want to avoid, although I guess I'll be making a mod to the lathe to fix this at some point in the future... Ketan: Thanks - The A2Z CNC is a very nice looking, if pricier alternative to ARC's QCTP, but will it restrict the turning diameter as Norman warns (see above)?
This is a problem, but if the workpiece has too large a diameter to use the tool holder in the normal way, I get round it by using a tool in the rear of the toolholder (the one that came with the lathe) for facing off and a borring bar in the rear for parallel cutting. (I hope that's clear - at least I know what I mean)
I have an AET type one, and have used the HBM types.
I am totally convinced that a solid lump of mild steel is by far the best toolholder for the minilathe.
Each tool has one permanently fitted, the tools are shimmed to height (only need to be shimmed once), and changing tools is really easy - unlike the AET types you do not have to find a tool, just unscrew the levered nut and replace the tool with a new toolholder and tool.
It's at least as quick as changing a tool on the HBM, and quite a bit faster than changing one on the AET type (assuming you can find a suitable hex key).
I get a lump of 25mm by 50 mm mild steel, about 40 mm or 50 mm long depending on the tool. First I drill a 10mm hole for the threaded post, then I fit it on the threaded post with a 3/16 plate under it and mill a
12mm slot. Take it off, remove the plate (which is just used to give the slot the correct height) drill and tap 2 or 3 holes for holding screws, replace, fit the tool and shim to height.
I don't bother to finish the bottom surface, but some people might. I occasionally use an accurate steel pin which fits into a hole in the post bottom for repeatable location, though not always. Use two holes and pins if you want really accurate location repeatability - much more accurate than a HBM/AET type.
This is first of all rigid, far far more so than any of the other types of tool holder I have seen, and most important it means you can get the tool right next to the threaded post, no overhang.
It's repeatability is far more accurate, both in horizontal position and height [1]. Plus it's cheaper.
Hope this description is clear. It doesn't take long to make one, and once you have made three or four for the major tools you will never use a quick change toolpost for them again - I do use my QCTP sometimes for tools which I only use occasionally, as it's easy to adjust the height, but that's all.
And if I need rigidity, eg for hard materials, accurate parts, or when there's lots to remove, I make a lump holder for them and shim the tool. No wobbly overhang.
[1] The horizontal position can be fixed by two highly accurate steel pins, unlike the HBM/AET types where it depends on the fit between the hole and the threaded post, as well as the fit to the stop. Vertical height is fixed by shims, and isn't going anywhere, while I find the screw height adjust types can bend and unscrew in the wind.
Hi Peter, This sounds very interesting (I use indexable carbide tools so the height for each tool remains constant) but I'm struggling to visualise your design. Are their any images of it online, or could you email me some? By the way, no joy with getting any more of those thin tungsten carbide rings I hoped to send you. I'll have to snap a piece off one I have - I'll post it to you tomorrow...
Note how close the tool is to the vertical threaded post, and that the cutting point is vertically over the cross slide, and that apart from the tool overhang itself there is solid metal everywhere under the shank of the tool.
Downward pressure on the cutting edge will tend to tilt the top slide, but that's semi-permanently locked (the big cap screws amongst the jib adjusting screws). But downward pressure will *not* tilt the cross slide, as the operating point is vertically between the bearing surfaces.
(the hex nut with a nail in it is a carriage lock - absolutely essential for a minilathe. The hole in the saddle was already there, I think it's for a steady)
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shows a similar small parting tool in an AET type holder for comparison - note the overhang!! There is a big gap under the shank of the tool with no metal, so downward pressure on the cutting edge must be resisted by metal not bending rather than metal not getting squashed :0) and metal doesn't squash easily..
And apart from being potentially wobbly at the joint between the tool-holder and the holder-holder, downward pressure will also tend to tilt the cross slide - which can be really bad news especially because you can't lock the cross slide when parting or facing.
Thanks Peter, I've re-read your previous post with this illustrated one and you've convinced me! I particularly like the way your holders are machined 'in situ'. Quick change tool posts seem redundant for replaceable cutting tip tools since you only set the tool height once. That frees you up to design a much more solid tool holder. I will definitely be using this approach - thanks again. Do you think there's any practical advantage in making the holders from something more robust than mild steel?
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