|Gene Pavlovsky||15/01/2020 07:59:27|
|26 forum posts|
I have finally got my first lathe, a Hobbymat MD65. I got it from UK (I am myself a Russian living in Luxembourg). It came with a whole lot of bits and pieces, and it looks like a few little things for those are missing. I would also like to understand what is what. Some things are clear, some are not so much.
I will post picture and I hope you will help me to figure it out one by one.
Lathe itself, just to show it.
Pulleys. Seems it already has the slow-speed attachment.
Toolpost (quick-change?). This has two dovetails. There are 3 matching holders with tools (carbide-tipped?). One tool appears to be damaged, unless it was designed like this for some reason. There are two pins that operate plungers which lock the dovetailed holders (I suppose using a cam inside). The pins have holes for a handle or a tommy bar, however I didn't find the handle anywhere. I operated them with a suitable diameter bar, and one of them (the one which would be used for a boring tool) turns easily, while the other one (regular tool) is hard to turn/jams, and also the orientation of the hole seems to be so, that when trying to look the tool holder, the handle fouls the holder and it can't be locked properly. I'd like to know if this toolpost is a standard item, how does the original handle/tommy bar looks like, and how do I disassemble it to check if there's anything wrong with the locking pin that seems to jam? I am also wondering if matching additional tool holders could be purchased today, or would I have to make it myself (that is, if this toolpost is worth keeping)? Note the last picture showing the parting tool (and the holder, I guess) came from Chronos from 1992, I wonder if they still have these things... By the way, the locking screw on the parting tool holder is shorter than on the other three holders, I wonder if it has any significance.
|Gene Pavlovsky||15/01/2020 08:01:02|
|26 forum posts|
Original toolpost is also included, along with two screws and one (!) washer. I guess the other washer got misplaced. I found washers of the same diameter, but thinner, in a small box with screws and washers. I hope it's a regular washer? The screws look weird, is there any purpose to these curved cutouts?
This is the picture of the small parts box. There are taps and dies, and I guess reverse jaws for the 3-jaw chuck.
Four-jaw chuck. This looks like an original item. I found one like this that someone tried to sell on eBay for 300$ - it didn't sell (obviously). It looks like already attached to a backplate, however there are three threaded studs sticking out the back. I wonder why, and what to do with those? I've seen pictures of a 4-threaded chuck for MD65 and nothing was sticking out the back. Unfortunately, there is not a single lathe chuck key anywhere! Both 3-jaw and 4-jaw chucks have a hole that measures around 6.3 mm - so I'm guessing a 1/4" lathe chuck key is needed. Any recommendations?
There is also one backplate, here it is.
|Gene Pavlovsky||15/01/2020 08:02:03|
|26 forum posts|
Jacobs chuck 34-06 6 Taper chuck. There are also two arbors, MT2-JT6 and MT1-JT6, I think this allows to mount the chuck in either headstock or tailstock. Unfortunately there is no matching chuck key. I measured the hole size at 7.9 mm, so I'm guessing it's a 5/16" pin size chuck key, it seems either Jacobs K3C or K3 would fit (or both, I couldn't find the difference between them). I didn't find where to get it in Europe, though.
There are more things and more questions, but I've posted the things that interest me the most, and will ask about the lower priority ones later, to avoid too much clutter in the thread.
Thanks in advance to all the helpful people here
Moderators: please delete my previous post, which had the pictures linked from imgur instead of embedded in the post.
|Roger B||15/01/2020 08:39:39|
84 forum posts
The quick change toolholder was comercial item. I also have one and find it useful for setting the tool to centre height for non indexable tip tools.
I have not had to dismantle mine so I can't help there. I don't have a tommy bar, I just use a convenient sized allen key.
Most of the time I use the original tool post with indexable tip tools so the certre height is automatically correct. I believe that the cutaway parts of the fixing bolts are to limit the forca that can be applied to the rather thin top slide.
I think that this key should fit your lathe chucks:
I guess you already know of RC.
4861 forum posts
The lathe tool is damaged probably when a parting off cut jammed. scrap.
The 'curved cutouts' are to weaken the screws because they are only going into a thin bit of cast iron - be careful even so and even more so with the normal screws on your other toolpost.
I see you have a 3D printer. Later I will post on another thread a picture of a printed MD65 3 tooth changewheel.
|Clive Foster||15/01/2020 10:51:57|
|1950 forum posts|
Swarf ingress is a common problem with locking plungers on QD type toolposts. Given the generally close fit of the moving parts its amazing how much gets in over the years and, eventually, seriously interferes with the operation. Dismantling is usually simple once you have a clear mental picture of how things work.
The operating cam is made by cutting away part of a round spindle so the cut out allows the plunger to move under the influence of an internal spring unlocking the toolholder. In the locked position the plunger is forced against the toolholder by the part of the operating spindle opposite the cut away portion.
Theoretically you just move the plunger back against the spring and wiggle the operating stud around until you find the magic combination of positions that aligns the bores in the toolpost and plunger with the full spindle diameter. Then it simply pulls out. Unsurprisingly swarf or other gunge inside renders things somewhat unco-operative so it can be difficult to feel exactly when proper alignment is achieved. Yours, I think, pushes the plunger forwards to lock the toolholder making them intrinsically more tricky to dismantle than the type that pull the locking device back eg Dickson. Much cheaper to make though. The eternal conundrum is a not so good design you cna actually afford preferable to a better one that needs serious saving up for.
As ever once you have the knack its usually pretty easy. I advocate stripping, cleaning and lubrication on a yearly basis. Mostly to ensure that the thing will come apart to service when needed without undue verbal encouragement.
Before applying too much force its worth verifying that there are no pins, setscrews or similar helping locate the cam spindle. I've never seen such but thats no proof that it isn't sometimes done.
|Andrew Johnston||15/01/2020 10:52:09|
5083 forum posts
Any industrial tool stockist should have, or be able to get, keys for Jacobs chucks. Here's a link to the manufacturers technical page:
The stockists they list are in the US, but plenty of UK stockists for chucks and keys. I'd be suprised if the same wasn't true for Europe.
|5022 forum posts|
Well, that one is broken - throw it away.
Those brightly painted tools have brazed carbide tips. I don't care for them much, feeling they don't have the advantages of either HSS or exchangeable carbide inserts. Disadvantages:
Carbide works best on fast powerful machines pushed hard. It doesn't fail on a small slow lathe, but HSS generally produces a better finish than carbide at slow speeds. I've found the sharp carbide inserts intended for use on Aluminium work well on steel at 'normal' lathe speeds.
Beginners (and more experienced types) often favour the convenience of carbide inserts because you don't need a grinding wheel or have to learn to drive it. Very helpful when first starting because, whatever else you might be doing wrong, it's not because the cutting tool is blunt or badly shaped. On the other hand, grinding HSS isn't that difficult, or so other people tell me, and, provided it's sharp, HSS performs well in most circumstances. It can also be ground to whatever shape is needed, which can be helpful for some jobs.
Don't be afraid to try both.
|Nicholas Farr||15/01/2020 12:17:16|
2049 forum posts
Hi Gene, I don't know about any Hobbymat machine that Bazyle is talking about, but a 4 Jaw chuck cannot be fitted directly onto the flange of the machine that I have, as you can see in the photo below, it has two sets of three holes on two different PCD's. In the supplement notes of my user manual, it states that a backplate will be needed.
Below is a scan of the page with the instructions on, starting from paragraph 4. The studs sticking out the back of your 4 jaw backplate should be in line with three of the holes in your flange and as Bazyle has said, it is good fun fiddling with the nuts in the small gap.
Incidentally, do not remove the flange from the spindle, read here Check for true running
It looks a nice machine and in good order too.
Edited By Nicholas Farr on 15/01/2020 12:18:54
|Gene Pavlovsky||15/01/2020 12:28:59|
|26 forum posts|
Thanks for all the comments!
Roger, do you have exactly this toolpost, and does it work fine? What makes the indexable tip tools special, which allows to use them in the original toolpost and automatically have the correct center height? I am planning to visit RC Machines shop here in Luxembourg pretty soon. Won't a 6 mm chuck key be a bit of a sloppy fit inside the 6.3 mm hole?
I've fitted the original toolpost at the moment. In the bag with it were two screws and one washer, like I said before, well I found out that the washer is too big to fit in the screw holes, it was probably misplaced. I've checked the parts diagram in the lathe manual and there are no washers there. The screw (page 44, part 15) is named "break screw" in the manual, which suggests it's indeed a safety measure to prevent damage to the top slide by ham-fisted operators. Looking at the parts diagram, I've also noticed that in the other hole in the top slide, there is a "threaded stud" (page 44, part 20, looks like a set screw / plug). This one is missing on my lathe, would be a good idea to add it to prevent dirt getting on the top slide's screw. I am wondering, though, what is that hole for? Does something useful sometimes attach to it?
I will throw out the broken parting-off tool, then.
Bazyle, thanks for the explanation regarding the chuck. I've taken a closer look at how the 3-jaw chuck is attached, and indeed it seems if I undo the 3 nuts, I should be able to just put the 4-jaw chuck in with it's 3 studs. It looks like fitting the nuts back will be fun I am guessing that the 4-jaw chuck was not the original one? Because the 3-jaw chuck is a 1-piece item, with studs at the back, while the 4-jaw chuck is a chuck attached with 4 screws to an "adapter" (which I previously called back plate), which has the 3 studs sticking out. I'm guessing an original chuck would be 1-piece, to reduce it's width (or should I call it length?). Both chucks have the same size hole, so one key should be sufficient. I'll bring one of the chucks with me to RC Machines shop and try out the key(s) they have. I don't have a 3D printer, I wonder if something in the background in my pictures looks like one? One of my coworkers probably has one, though, I will ask around (software developers, there are many geeks among us). I did stumble into an archive with SolidWorks files for a set of change gears for MD65, there was no 63-tooth in there, though. Which extra thread pitches does it allow?
Clive, I understand your description of the toolpost, however I think the one I have is a different design. It seems that the pins have cams that stick out (like an engine camshafts). They were inserted into the body from the bottom - the holes are bigger at the bottom, then the holes were closed by pressing in bushings with serrations on outside to keep them. The bottom ends of the pins are guided by those bushings, the pins can be lifted slightly so I can see the larger diameter cams through the <1 mm gap that opens. It doesn't feel like there are any springs involved. I can't think of a way I could remove those bushings without destroying them or damaging something else. I think if I took a round bar and made two L-bends in it, I would be able to operate the pin with that (it would clear the second pin so allow more rotation) - perhaps the original tool that came with it were of this shape? On the other hand, like you said, on this toolpost, the cams indeed push, not pull, the plunger against the toolholder, I've read somewhere recently that toolposts of that design don't really offer repeatable accuracy when the tool holder is removed and replaced. Maybe I should just scrap this and use the original toolpost?
Andrew, thanks for the advice, I will check the companies who sell the Jacobs chucks in UK or Germany, and then ask them for a spare key.
Dave, thanks for explaining the difference between the three types of tools. My lathe came with some number of tools in the box(es), looks like most of them are of the brazed-tip variety which you don't recommend. I did read about the advantages of HSS tools in Harold Hall's book, and do intend to learn to grind them. I forgot to mention that I did buy a 200 mm bench grinder (20 years old but never used, I had to replace the start capacitor), it came with Aluminum Oxide wheels. As a woodworker, I've already learned that new tools have to be sharpened (and possibly fettled with). So far I didn't begin to learn grinding with a bench grinder, I've been using diamond sharpening stones (the extra-coarse ones are quite effective at removing material). I will consider buying a small set of HSS tools as well as HSS blanks, and then will try to grind the blanks to imitate the factory tools (Harold Hall's book has some drawings as well, but some are still a little bit hard to understand for me, so it will be useful to see an actual tool). I do intend to work on my grinding and sharpening skills, I think it's an essential part of the job (for hand tool woodworking it's a must, and for hobby metalworking I think it should also be useful).
Would it be useful to buy a set of indexed-tip carbide tools, or better to learn on HSS? Are the "budget" ones acceptable quality, or shou
|Gene Pavlovsky||15/01/2020 12:48:08|
|26 forum posts|
Nick, I see what you're talking about, and I did read those instructions. It seems that my 4-jaw chuck already had this backplate (mentioned in those instructions) fitted. The chuck itself has a bit of chips/swarf inside, so I think it had already been used on the lathe, suggesting it should just fit with no further modifications. I will try to confirm this some time this week. And thanks for your advice of not unscrewing the chuck flange. I plan to read the manual completely before I attempt "playing around" with my new toy.
Some more advice I'd like to ask. Is it advisable to re-grease the spindle bearings? I was told that the lathe was not used much, so it would have way less than 1500 hours mentioned. However, car or motorbike manuals usually say oil should be replaced every X thousand kilometers, or 1 year, whatever happens first. Grease also tends to get old, I suppose? And the lathe was made in 1987 - some 33 years ago In the instructions re-greasing sounds somewhat simple, but I know such things can be misleading. From experience when working on a car or a motorbike, sometimes one sentence in a service manual can take one hour of struggling and swearing to accomplish. So if someone did it / does it regularly, how easy or tricky is it, and what grease do you use?
The manual says "oil the bed", "oil the screw and the dovetail guides" etc. The spindle re-grease procedure mentions "acid-free precision instrument oil". I have a bottle of Mobil Velocite #10 ISO VG 22 Spindle Oil. Is that suitable for everything? Or should I get some other kind/viscosity of oil, e.g. "Ways oil"?
|Nicholas Farr||15/01/2020 13:17:59|
2049 forum posts
Hi Gene, it shouldn't be a too difficult task if you have basic spanner skills. Whenever I got a second hand car privately I would always change the oil etc. regardless of whether I was told it had been changed recently or not and although the Hobbymat had an issue or two when I bought it, I did a complete strip down and clean, paint and re-grease, it was not a real task for myself and if you follow the instructions, you should be OK with it.
See my Stripdown
|Roger B||15/01/2020 13:21:37|
84 forum posts
As far as I can see my toolpost is identical. I works without any problems and allows easy adjustment of centre height. I tend to use it when boring or screw cutting with HSS tools. The tool holders are rigid when clamped but do not always go back in exactly the same place when removed (the larger more expensive versions are more reproducable).
The benefit of indexable tools is that by design the tool tip is the stated dimension above the bottom of the tool. If I put a 10mm tool holder in the standard toolpost it will be on centre. The tips are not cheap and when they get blunt or chipped you just throw them away. I have a selection of 6mm, 8mm and 10mm tools. The smaller ones are set to height with 2mm thick packing pieces. I started out with a Proxxon set
I have additional holders from Glanze (Chronos) and CTC.
The additional hole in the top slide is to allow the yellow vice to be fitted in milling mode.
|Gene Pavlovsky||15/01/2020 13:27:03|
|26 forum posts|
Nick, indeed same thoughts as you mentioned about second-hand cars. I'm reasonably ok with spanners. And I do love greasing and lubing and oiling things (my wife likes to make fun of this habit of mine). I guess I will plan a spindle re-grease for some near future. Don't know about a complete stripdown, as there doesn't seem to be a particular reason for it (another guideline with cars is not messing with what's working properly). Your Sunshine Yellow paint job seems pretty close to the original color, isn't it? I do like this color a lot, I had painted an espresso machine a very similar shade. So, which grease and oil(s) do you use for the lathe itself?
|Gene Pavlovsky||15/01/2020 13:37:24|
|26 forum posts|
Roger, I'll try to figure out how to dismantle the toolpost to figure out what's wrong with it. I am thinking about trying to drill out the plugs in the bottom holes. If I manage to do it without damaging the body, it shouldn't be a problem to make replacement plugs. I also thought that instead of the two separate plugs, if a groove is milled to span the two of them, a plate with two holes drilled in it could replace the two plugs, and it could have a countersunk hole for screwing it to the body. This would allow easy disassembly for cleaning. I hope my explanation makes sense, if not, I will sketch my idea.
Someone is selling a toolpost that looks very similar (for quite a lot of money!): eBay link
It looks very similar, but the pins have allen key heads, this seems more sensible. If I manage to get my apart without damaging it, I will think about adding allen heads to the pins.
|Nicholas Farr||15/01/2020 13:47:14|
2049 forum posts
Hi Gene, I don't really use this one very much now, but use a slideway oil for the bed and leadscrew etc. I can't remember what actual grease I used in the spindle bearings but I think it was a high melting point one that was used where I worked at the time, I think it was similar to what one would used on car wheel hub axles, whatever it was it's been working OK. I do agree that you don't need to do a full strip down, but in my first picture in the link, you can see I had no need to remove the bearing at the chuck end of the spindle, nor did I remove the bearing cups in the headstock.
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