Wildguzzi.com
General Category => General Discussion => Topic started by: nobleswood on July 30, 2020, 09:38:23 PM
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Bought myself a Prazi SD 300 mini - lathe. Now I need to learn how to use it :laugh:
Looking for recommendations for books, websites or YouTube videos to watch.
TIA :thumb:
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Back in the '70s when I started getting hold of some machine tools I attended adult education classes at a local vocational school. Helps a lot to have someone who knows what he is doing looking over your shoulder to show you the right way to do it. Added bonus, first semester we had assigned projects to do but second semester they would let us do our own projects if they deemed it worthy. I built a lot of custom Norton parts there that are still on the bike today.
Pete
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Try looking for videos/books on the Emco Unimat lathe (very similar) or the Myford ML7 lathe (bit bigger)
Both were/are used a lot as model making machines and have quite a lot of support behind them
Also Ian C Bradley or Tubal Cain both had a good reputation for books back when my Dad and I were messing about with this sort of thing
Yours is a manual machine so lots of the older books will be relevant
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Tubal Cain has dozens of free instructional videos on YouTube. There's nothing that this guy doesn't know about manual machining. Very patient and clear explanations. There are others that have more technical stuff as you move along. I bought a Grizzly a few years ago and I've made a pile of custom bike parts. I give you about 6 months before you are shopping for a companion table top mill to go along with the lathe. Great fun.
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Thanks Guys,
I would love to sign up for some evening adult classes but during the current pandemic that isn't likely. :sad:
Clubman you're right, a benchtop mill is on my wish list.
Tubal Cain is a name I've heard before, I'll check him out
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I have a lathe and am mainly self taught. To give advice is hard without knowing what level you are at. I had a look and this appears to be a small lathe.
If you are an absolute beginner I would like to recommend that you could start with plastic or nylon rod.
It may help if you ask any direct questions you may have. This will help as gauge your experience level, as learning to use can mean so many different things.
Steve
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Steve,
I know how to turn it on & that’s about it :rolleyes:
As a woodworker I know something about steel & cutting edges but not anything about cutting shaving from a rotating piece of metal. I’m at the stage of knowing that I know a very small amount
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Remember even a small machine will maim you if you break the rules.
I remember a dude I worked with who did his time at a large facility, I forget the story in detail but they had large lathes facing each other... The short version is another dude landed on the floor behind him who had been dragged in and ejected.
Similar story here, although not sure if it was a large lathe or more specialized piece of spinning equipment. Long before I knew him, my first wife's grandfather (my grandfather-inlaw?) reached where he shouldn't while working at the textile mill. His arm caught. It threw him 30-40ft across the room and his arm stayed where it was caught... While he and the family was at the hospital, two friends from the mill retrieved his arm, took it to his house and buried it in the backyard for him.
As a fellow new metal lathe & mill owner, I've been watching videos and reading, too.
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Hunt up a copy of "How to Run a Lathe" By South Bend Lathe Works. Last published in the '70s.
https://tinyurl.com/y3t228oc
This will get you a free copy.
See Page 146!
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I would buy a book like Machining Fundamentals by John R Walker. It will give you a good start of the basics.
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I had machine shop classes in high school and one of the classes for the year was to use a lathe to do projects as assignments. These were the big pro honking machines with lubing, etc., and a few key things that I remember are:
Wear goggles, no loose clothing around your sleeves, sharp and properly cut bit, angle of the bit to the surface being spun, and patience. We spent a lot of time and were tested often on the bit sharpening technique as it is key in getting good quality results. You can also use the auto-advance to get a really good finish, but a steady hand and patience was my preferred method and I found it more pleasant and less stressful while working (auto-advance would stress me out).
Good luck, and fun purchase. :thumb:
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And take your rings and bracelets off your fingers and wrists.
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I'm fairly lax on safety around machine tools any more.. but I *always* wear safety glasses when running a lathe or drill press. Both are perfectly capable of sending a shard of broken drill bit toward your eye, especially when you are learning. No long sleeves running any machine with a rotating spindle. No gloves. No rings. No long hair. (I've seen a girl get snatched bald.. not pretty.)
*Any* machine that is capable of cutting steel will just laugh at flesh and bone.
When Austin started on the cnc mill, I told him my most important job was making sure he didn't get hurt. So far, so good. :smiley:
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As a professional woodworker I am around saws, planers & shapers & have a healthy respect for them.
Lathes. Not so much.
In my apprenticeship we ground our own knives when it was something we didn’t have for the shaper. There was one guy in the workshop who whenever he was about to fire up the shaper I’d find an excuse to leave the room or search for my pencil on the floor behind my bench. He’d get in a rush & not tighten the knives in the head 😳.
I’ll look up the book titles tonight .
Cheers
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As you know how to use a wood lathe I am going to assume you can master putting something in the chuck and understand if it is long to use the tailstock. If not please ask.
The next step/decision is tooling. When I purchased my lathe I bought indexable tool bits as I was not sure on grinding High Speed Steel (HSS). I have since learnt to get full value out of indexable carbide bits you need a powerful lathe and you should work them hard.
The best tool I have purchased is a Diamond tool holder https://www.eccentricengineering.com.au/products/diamond-tool-holder/the-diamond-tool-holder there is a video at the bottom of the page that demonstration how it works. I use this for 80% to 90% of my lathe work. It is almost idiot proof to sharpen and in my opinion a very cost effective way to go.
To keep this one step at a time I think the first decision is what tooling you will use. If you have questions to help make up your mind please ask. I am sure there will be enough opinions to keep you busy. I would say the biggest trap is buying to much tooling to early. Once you get experience you will decide what will work for you.
When it comes to using your lathe and selected tool you will find tables and formulas to tell you what speed to turn the item at. Essentially the smaller diameter the faster the speed. It also works on the hardness of the material and HSS bits require about half the speed of indexable carbide. This is another advantage I found with using the Diamond tool holder. I was not spinning the piece as fast, therefore not throwing the chips as far.
I will leave it here for now and if I notice any questions I will chime in.
Steve
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Regarding tooling, the lathe came with a quick change tool holder.
(https://i.ibb.co/wMFj2kd/IMG-4533.jpg) (https://ibb.co/wMFj2kd)
The tool holders; I'm still learning what each part is called
(https://i.ibb.co/jH2YQBQ/IMG-4532.jpg) (https://ibb.co/jH2YQBQ)
And bits
(https://i.ibb.co/QPTjbR8/IMG-4531.jpg) (https://ibb.co/QPTjbR8)
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Nice. :thumb:
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The collet set that the lathe was advertised with, had been sold separately.
Have to study up on how to use what I have & how to sharpen it
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The collet set that the lathe was advertised with, had been sold separately.
Have to study up on how to use what I have & how to sharpen it
I hope there was a considerable reduction in price..
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$300
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Probably about right.
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Go on YouTube and subscribe to training videos by Joe Pieczynski. He diagrams and speaks in a common way and has a sophisticated, commercial shop.
Patrick Hayes
Fremont CA
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I am slowly getting to watch videos & familiarize myself with this lathe; so here's a question.
Measuring runout, I have 0.001" on the faceplate. But there is 0.014" measured on the body of the 3 jaw chuck & the same measurement on a new drill bit held in the jaws & measured close to the chuck.
The question is, can anything be done with the chuck or should it just be replaced ?
FedEx managed to drop the lathe in the delivery. There is a claim on going.
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Take the chuck off and measure the runout on the inside of the spindle. If the spindle is under .001 then it may just be the jaws are not closing evenly. Not uncommon on cheaper chucks but thats why you use collets for more precise work. A collet should be dead nuts.
Pete
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Regarding tooling, the lathe came with a quick change tool holder.
(https://i.ibb.co/wMFj2kd/IMG-4533.jpg) (https://ibb.co/wMFj2kd)
The tool holders; I'm still learning what each part is called
(https://i.ibb.co/jH2YQBQ/IMG-4532.jpg) (https://ibb.co/jH2YQBQ)
And bits
That's an important bit of tooling. I would have recommended those as a first add to the lathe. Little Machine Shop is a good resource. I have purchased a number of thigs from them and the customer service is very good.
https://littlemachineshop.com/
(https://i.ibb.co/QPTjbR8/IMG-4531.jpg) (https://ibb.co/QPTjbR8)
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(https://i.ibb.co/cJt0czy/A81-A0554-6192-45-F6-8-CB3-89-FD98-CD12-BA.jpg) (https://ibb.co/cJt0czy)
This is how I am measuring the runout on the chuck body & on the faceplate it is bolted to.
It maybe that I have to learn to be more subtle in adjusting the chuck on the faceplate
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The faceplate & the chuck body both have a ‘0’ engraved into the metal & that was what I was using to align the parts.
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(https://i.ibb.co/cJt0czy/A81-A0554-6192-45-F6-8-CB3-89-FD98-CD12-BA.jpg) (https://ibb.co/cJt0czy)
This is how I am measuring the runout on the chuck body & on the faceplate it is bolted to.
It maybe that I have to learn to be more subtle in adjusting the chuck on the faceplate
I wouldn't worry so much about the runout on either of those surfaces. They don't do any work and aren't necessarily true to the working surfaces. What is the runout in the bore of the spindle shaft? Is there a "register" disk on the faceplate which engages a recess on the back of the chuck? What is the lateral runout on that register? Have you removed and reinstalled the chuck jaws? The jaws and their sockets are numbered and you should install them back in the same sockets that the manufacturer intended. If you still have too much runout, remove the chuck screws and rotate the chuck to use different hole pairings and see which setup gives you the least. If you still have too much runout, consider setting up a Dremel as a toolpost grinder to gently grind the working face of the jaws. Lots to do for fine tuning. You can get waaayyyy too anal about this. What are you planning to fabricate? If you're not doing really precision work, you can easily spend more time than necessary to tune the machine. Should be lots more YouTube videos about trueing up the machine.
Patrick Hayes
Fremont CA
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Removed the chuck, which does not have a registering plate on the back.
The tip on the dial gauge may not be the best for measuring the inside of the spindle, but hey it’s what I have. Contacting the outer edge which felt as if it had some irregularities in the surface.
(https://i.ibb.co/TKYGXWD/CD2-A0-E12-7-E32-4077-9-D3-B-EF2-CA57-D4-CD4.jpg) (https://ibb.co/TKYGXWD)
The variation;
(https://i.ibb.co/7YgmNgd/CFD1813-B-5495-4740-8-DDE-6441-CAB30-D9-B.jpg) (https://ibb.co/7YgmNgd)
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I removed the chuck & rotated it 120*, pinched up the nuts & measured. Then repeated again 120*.
The variation is the same each time.
I have tried gently adjusting with a rawhide mallet but I haven’t got the results I want yet. But I will again.
Realizing that this isn’t a high end machine I wasn’t expecting +/ - 0.001” but I was hoping for > 0.01”
Still haven’t given up on find glaringly obvious answer that I am just not seeing yet.
Thanks all
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After thinking this over I'm going to work on the idea that the mounting holes in the faceplate are the problem and make some adjustments there.
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Easy to think the machine has to be perfect to make perfect parts but that is not true for a minute. You just have to know how to make your parts with the machine you have. Every machine in every shop I ever worked on had some issue that you had to work around because nobody was going to fix it. Learning the proper sequences and running a machine within it's limits will let you make very good parts. It takes time to learn and skill sets will be learned as you go. Be patient and make parts, it will get easier as you go.
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Once you get it set it should hold until it gets crashed. The tooling will cost at least as much as the lathe. It’s a great pass time, the hours fly by so getting the time to use it gets difficult. There are two things a lathe can do, one is replicate itself and the other is hurt the operator badly. Watch out for “machine hypnosis “ and make some cool stuff. I have a pile of stuff that I wasn’t happy with, sometimes I can make something the first try, some times it takes a couple or more and I’m glad I don’t have to earn a living that way!
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After thinking this over I'm going to work on the idea that the mounting holes in the faceplate are the problem and make some adjustments there.
So, you have no register dome on the spindle to force or maintain concentricity. Here's an idea.
Find a plate of 1/2" metal.
Drill the three mounting holes but make them small enough to thread internally.
Mount this dummy plate up against the spindle and use short bolts from the back side which will hold the plate in position and mark that as your standard, or re-mount position for every usage.
I saw on the video that the chuck DOES have a recessed back to allow for attachment to a register dome.
Now, turn 1/8" or so from the front of this dummy plate so that you create a register dome for a snug fit with this chuck recess.
Drill 3 new holes in the dummy plate and recess the back side of those holes to the dimension of allen head bolt heads.
Unmount the plate from the spindle and mount it to the back of the chuck using these recessed allen bolts.
Now remount the plate to the spindle and with luck you will have something very close to concentric.
You might then consider a gentle grind to the jaws to approach precision.
This is delicate work for a beginner, but a good learning project. You might need help from someone with a mill or another lathe to ensure that your bolt holes are in a precise "bolt circle" layout.
Starting with 1/2" or 3/4" aluminum plate would be easier to work with and might serve you a long time. Once your skillset develops you might do it again in steel for better durability.
I have made backing plates like this numerous times in order to adapt other, odd chucks and fixtures to several different sized lathes. You're trying to make something like this:
(https://i.postimg.cc/T1yzyb7X/MVC-122X.jpg)
The accuracy is still dependent upon using the bolt holes of the spindle face and that may vary slightly every time you remove and reinstall the chuck. With practice, you will learn to remont and restress the bolts always in the same direction so you can at least be accurately repetitive if not accurately concentric.
Patrick Hayes
Fremont CA
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What is the size of the pass-through hole in this chuck?
Could you mount a collet in the spindle, then a precision rod in that collet, then install the chuck by first clamping it to this mounted rod before bolting?
In this way, you would get the jaws very close to concentric before bolting down the chuck.
Of course, there has to be enough room for you to now remove the precision centering rod and the collet that was holding it.
Might be something you'd have to make. Perhaps sacrificing some other purpose built tool with the proper taper. Start by measuring the ID of your pass through hole in the chuck.
Patrick Hayes
Fremont CA
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Thanks! I like the backing plate idea, rather than throwing money at a new chuck & hoping. :thumb:
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This guy did a lot of work. Should be helpful guidance for you.
http://www.bazmonaut.com/machines/hobbymat-prazi-md65-lathe/fitting-new-chucks/ (http://www.bazmonaut.com/machines/hobbymat-prazi-md65-lathe/fitting-new-chucks/)
Patrick Hayes
Fremont CA
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Bazmonaut. I've been reading his posts they have helped especially as he's working with the same lathe.
Anyway, success !
Pulled the chuck, checked the mounting studs for nicks & kissed them with a fine Nicholson file. Remounted & managed to get TIR to 0.005". Good enough for me.
Thanks for the advice, pointers & ' no need to be paranoid' guidance.
'Hello my name is Tim & I'm a Perfectionist' :grin:
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Good enough for me.
You can do better, grasshopper.. :smiley:
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I had a machine shop instructor in college who said ".001?, why you could drive a truck through it!".
You want to aim for perfection.
Pete
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I know nothing about that little lathe except it has a good reputation. I'd bet money (Not Guzzi content) :grin: that the spindle is on the money. If not, you will have to make it so. (New spindle bearings, etc.) *Assuming* that it is, there is no reason that you can't get it to run true.
In general, 3 jaw chucks aren't terribly accurate, but there are some tricks you can learn. Just the same, (it has a good reputation, again) unless FedX really did a number on it.. you should be able to get it running better than .005.
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Obi - Chuck,
I am interested in the ways to set up the chuck to be more precise. :bow:
From what I could measure the faceplate & the spindle had just under 0.002" TIR. Which is the specification in the sales brochure.
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Go on YouTube and subscribe to training videos by Joe Pieczynski. He diagrams and speaks in a common way and has a sophisticated, commercial shop.
Patrick Hayes
Fremont CA
yes, piescynski is a machinist's machinist. there are a number of really good online machinists and you will find them easily once you start poking and prodding for machinists on the utoob. i would highly recommend Blondihacks for small machining/lathe tips. quinn dunke is excellent and knows her way around machining and especially the small home lathe that she uses. do not miss blondihacks.