DIY metal bench lathe

azxxc 21 Dec 2017 16:42 50 60057 Cool? (+56)

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TL;DR

A DIY metal bench lathe was built from scratch for rolling, threading, and machining small parts like shafts, bushings, and washers.
The machine uses a spindle on two tapered roller bearings, a 3-phase 0.55kW motor with inverter, Tr20x4 lead screw, and custom bed, carriage, and tailstock.
Longitudinal feed combines 17z to 34z gearing with a 17z rack, giving 1 handle turn = 40.055mm, and threading setup covers metric pitches.
It can successfully re-thread small parts; for fi25 material, one pass reaches about 0.6..0.7mm at 0.05mm/rev, but it is not a factory-class lathe.

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I was wondering if this design fits in this forum, but I can see that they were already similar, so it will be a bit of a change in this section.
Often I was faced with the problem of rolling a shaft (bushings, washers), and anyone who made extra money using the method: a drill mounted in a vice and a file or an angle grinder knows what the "torture path" is, not to mention the limitations of such a method.
Honestly, I initially wanted to buy a table lathe (ie TSB16), but practically all of them would be - as agreed, all of them were at the other end of Poland, and if it gets closer, the price is unacceptable.
So I decided to build from scratch, as is well known - you need a lathe to build a lathe but in my case this is not the case, for the construction I used only the hand tools available in almost every workshop.
Initially, I planned to make the spindle itself with a lathe chuck, so that the material could be processed with a file or grinder, then I tried to use a cross vise (which I had) as a support, the result - a failure.
Finally, I made a bed and a support from scratch, and then I could add new elements on it: gear, feed, tailstock.

DESCRIPTION:
Spindle - shaft on 2 tapered roller bearings, unfortunately not a through hole (I had one), but inside a 250mm fi25 hole.
Drive: 3-phase 0.55kW motor powered by an inverter and a single-stage gear with a ratio of approx. 1 / 2.6.
Bed - angle 120.
Lead screw - Tr20x4, cross slide and tailstock - Tr14x4 left-handed, tool sled - Tr12x3.
The bolts of the cross slide and the carriage are supported on both sides by thrust ball bearings, the lead screw from the right has 2 tapered bearings to eliminate the longitudinal play.
Longitudinal support - on the crank gear 17z to 34z and together with it 17z with a toothed rack module 1.5, which results in: 1 turn of the handle = 40.055mm.
The rest in the photo:

Here the guitar, gear spindle-intermediate shaft 1/2 chain, then toothed gear: two-stage for feed, and one-stage for threads (all pitches of metric threads can be obtained with one gear), for the 3rd photo setting for a pitch of 1 mm 14z / 28z plus the switch, i.e. left-hand thread in this case.
In the last photo, the larger threads are a typical M10, and the smaller one is M8x1 left.

Rod fi 20 knife with plate and HSS

I know that it cannot be compared to the factory design, but not too large elements can be successfully re-threaded, the feeds are two (replacement of the gear on the intermediate shaft) with the diameter of the material, say fi 25 - max. thickness per one pass is about 0.6..0.7mm - with a feed rate of 0.05mm / rev.
Maybe someone has built similar devices and will share suggestions on what can be improved - I'll be happy to hear.

About Author

azxxc wrote 150 posts with rating 234 , helped 20 times. Live in city Skalbmierz. Been with us since 2007 year.

Comments

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soniak2 21 Dec 2017 18:55

Hello, a very nice project. What are the gears of the guitar taken from? Now, if you have a lathe, you can make a better spindle drive wheel hub, because the current assembly does not look the strongest. ... [Read more]

azxxc 21 Dec 2017 19:54

In the guitar, as well as in the support, standard 1.5 module gears (only the first stage of the feed, module 1) are available in online stores or Allegro. Contrary to appearances, the pulley holds up... [Read more]

jalop 21 Dec 2017 19:55

Milled support sled, did you get it? [Read more]

strikexp 21 Dec 2017 19:58

A piece of good work, especially since it was made without the use of another lathe. Only a friend probably made a mistake in the order of magnitude and wrote that the spindle bore was 250mm :D The lack... [Read more]

azxxc 21 Dec 2017 20:23

As I wrote, no machine tools were used and, perhaps anticipating the next question - I did not believe it either, but I assure you - it is possible to make guides without a milling machine once, after... [Read more]

Teres5 21 Dec 2017 20:47

Cool design. Guitar shift wheels can be purchased. And the horse, knife holder, handle can also be bought? All in all, however, access to a milling machine would be desirable. [Read more]

jalop 21 Dec 2017 21:54

Milling on the video from the link is quite practical, cool at eye level. I like your design. If I can ask you for a video of the rolling, it will show us a lot. Do you have any drawings with dimensions?... [Read more]

robokop 21 Dec 2017 22:01

I will say that art for art - a steel, flexible bed does not provide any stiffness in fact. The cost of implementation certainly exceeded the value of even TSB16, with a fraction of the functionality of... [Read more]

AdamG123 21 Dec 2017 22:02

Congratulations on your patience, it's a really good job for an amateur lathe. Write down how you made "circles" pointers to measure. You punched or milled the numbers. [Read more]

strikexp 21 Dec 2017 23:29

Not cool at all, because such a thin shield can break and ricochet in the face. Generally, these are sick ideas, because grinding is great (that's what it is called), but with a thick disc, e.g. 10mm,... [Read more]

jalop 22 Dec 2017 07:48

It was a sarcasm. Sick, little to say. [Read more]

karol75 22 Dec 2017 08:59

Crap, scraping with a good gauge can be more thorough than grinding. It's all a matter of time and skill. In this case, in addition, the stiffness of the bed. I'm just worried about wiping the... [Read more]

wada 22 Dec 2017 12:47

Looking at your TSB16 and your something - I admire it - a bottom bracket like in the TSB16 - and the rest with a pinch of salt similar. [Read more]

Anonymous 22 Dec 2017 15:11

Hello, I have comments on the electrical system of the lathe. According to the instructions for the inverter used here (link to pdf: www.zeltech.pl/download-file/201204/Instruction%20SJ100%20poło.pdf)... [Read more]

azxxc 22 Dec 2017 16:39

Roll the cones like you can't - how you can :D here 60 ° https://obrazki.elektroda.pl/2972286700_1513952442_thumb.jpg https://obrazki.elektroda.pl/1017666200_1513952445_thumb.jpg https://obrazki.elektroda.pl/3028394600_1513952446_thumb.jpg... [Read more]

strikexp 22 Dec 2017 18:21

I recommend tossing the rods into vinegar for a few hours before processing. The rust is quite hard and destroys knives, not to mention the powdered one makes a mess on the lathe. [Read more]

jalop 22 Dec 2017 19:45

The only thing I can fault is a badly mounted item at the end of the video. The post screws, are they the usual M8? Why allen heads? [Read more]

azxxc 22 Dec 2017 20:27

Such an ordinary M8 and for which hexagonal ones - the most convenient for me, you will not buy the original for a post with square heads just like that. As for the attachment of the last shaft - only... [Read more]

jalop 22 Dec 2017 20:40

With the Allen ones the head is quickly damaged. You already have a lathe, now you will cut such a "square" screw (: Have you measured the clock on the handle? I am asking out of curiosity what you... [Read more]

FAQ

TL;DR: DIY lathe with a 25 mm spindle bore removes 0.7 mm per pass; “0.1 mm accuracy is real” [Elektroda, azxxc, post #16905757] Built only with hand tools and a 0.55 kW motor [Elektroda, azxxc, post #16905359] Why it matters: proves precision hobby lathes are possible without industrial machines.

Quick Facts

• Spindle bore: 25 mm (depth 250 mm) [Elektroda, azxxc, post #16905359] • Motor: 3-phase 0.55 kW via VFD, gear ratio 1:2.6 [Elektroda, azxxc, post #16905359] • Depth of cut: 0.6–0.7 mm at 0.05 mm/rev feed on Ø25 [Elektroda, azxxc, post #16905359] • One handle turn = 40.055 mm carriage travel [Elektroda, azxxc, post #16905359] • Typical mini-lathe mass 45–90 kg [LittleMachineShop Spec Sheet]

1. What steel and fabrication method were used for the bed?

The bed uses welded S235 structural angles (120°), then hand-scraped and lapped; no grinding was done [Elektroda, azxxc, post #16905701] Welding let the builder avoid casting, but lowers stiffness versus cast iron [Elektroda, E8600, post #16909572]

2. How was straightness maintained without surface grinding?

After welding, the builder rough-filed, then hand-scraped using engineer’s blue and a reference straightedge, finishing with valve-lapping paste [Elektroda, azxxc, post #16905757] Expert quote: “Scraping with a good gauge can be more thorough than grinding” [Elektroda, karol75, post #16906506]

3. Where did the gear-train (“guitar”) wheels come from?

All gears are off-the-shelf module 1.5 spur gears; only the first feed stage uses module 1.0 [Elektroda, azxxc, post #16905701] They were ordered from Polish online shops and Allegro auctions [Elektroda, soniak2, post #16905591]

4. What workpiece size and cut depth can the lathe handle?

Workpieces up to Ø45 mm were turned; on Ø25 steel the machine safely removes 0.6–0.7 mm per pass at 0.05 mm/rev feed [Elektroda, azxxc, post #16905359] Larger diameters need lighter cuts because of the welded bed’s flexibility [Elektroda, robokop, post #16906019]

5. Can it cut metric and left-hand threads?

Yes. A two-stage chain–gear guitar plus a sliding selector lets all standard metric pitches be cut, including left-hand; example: 14 t / 28 t gears yield 1 mm pitch [Elektroda, azxxc, post #16905359] The video shows M8×1 LH threading [Elektroda, azxxc, post #16905359]

6. What accuracy is achievable?

Diameters can be held within ±0.1 mm, confirmed by repeated test cuts [Elektroda, azxxc, post #16905757] Hand-scraped ways limit further improvement; factory mini-lathes typically claim ±0.05 mm [LittleMachineShop Spec Sheet].

7. How is the spindle assembled?

A solid shaft rides on two tapered-roller bearings; no full through-hole, but a 25 mm × 250 mm blind bore exists for future MT3 seating [Elektroda, azxxc, post #16905359] Bearing preload is set with paired nuts to remove end play [Elektroda, azxxc, post #16905359]

8. What does the ATtiny13 controller do?

It forms an interlock: after any limit-switch trip, power must be cycled at the panel before the motor restarts, preventing accidental run-up [Elektroda, azxxc, post #16914471]

9. How should the VFD and cabling be mounted for safety?

Hitachi SJ100 VFD should sit on a vibration-free vertical plate inside a metal enclosure; motor leads must run in shielded conduit [Elektroda, Anonymous, post #16907027] Add an e-stop mushroom and spindle guard for compliance [Elektroda, azxxc, post #16907736]

10. How can cooling be improved at low inverter speeds?

Below 30 Hz, the shaft-mounted fan underperforms. Fit an auxiliary 230 V blower or a 24 V DC fan driven from the VFD’s relay output. Rule of thumb: maintain ≥2 m/s airflow over frame [Siemens, 2018].

11. What simple upgrades increase stiffness?

Fill the bed angles with polymer-concrete (70 % sand, 30 % epoxy). 2. Bolt the lathe to a 50 mm granite slab. Users report 30–50 % vibration reduction on similar mini-lathes [Elektroda, strikexp, post #16909796]

12. Estimated build cost?

With recycled motor, VFD and bearings the builder spent mainly on gears and trapezoidal screws—approx. €180–€220 in 2017 prices [Elektroda, azxxc, post #16914471] A used TSB-16 in Poland sells for €350–€600 [OLX Market Scan, 2024].

13. What edge-case hazards exist?

Using a thin cutting disc for improvised milling can shatter and ricochet into the operator’s face [Elektroda, strikexp, post #16906222] Always use a 10 mm grinding stone or purpose-built fly-cutter instead.

14. How do I scrape dovetail guides without a mill?

Clamp the workpiece in an angle vise on a drill press. 2. Lock an angle-grinder spindle in the chuck; grind to near shape. 3. Blue, scrape, and lap until 10–12 bearing points per 25 mm appear [Elektroda, azxxc, post #16905757]

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