An overview of Thread Cutting with the Hobbymat MD65 along with some examples.
The spindle of the Hobbymat MD65 is driven with a belt and pulley system with an intermediate reduction pulley that can be seen on the right hand side of the image.
A gear is located on the spindle (behind the pulley in this image) and this has a key to locate it on the main shaft.
The set of gears here have a large reduction as the system is set up for a fine traverse.
The pillar at the bottom of the image has a lever that operates the dog-clutch to engage and disengage the leadscrew. At the very bottom right of this image you can see the dog-clutch that is disconnected at this point in time.
The saddle is permanently engaged with the leadscrew, this means that once you have made a cut you need to stop the lathe, reverse the motor direction and wind the leadscrew back to the start of the cut – leaving the dog-clutch engaged all of the time.
In this image on the right you can clearly see the drivetrain.
With change gears there is quite a lot of setting up of the gears and care needed to get it right.
The middle intermediate pair of gears have a metal carrier that is also the bearing. This is adjusted on the aluminium plate that in turn can be moved get the correct engagement of the gears on the main spindle.
As these are plastic gears I have left them dry, but they do pick up quite a lot of dust from the workshop, to date this has not done any serious damage and these gears have been used for around 30 years, ok fairly light use.
Change Gears for Hobbymat MD65A box of spare gears used to create the other spindle to leadscrew relationships – ie to allow you to create the other thread pitches.
You can see a metal spigot in the centre of one of the gears with a key to locate it.
Machining a thread up to a shoulder on the lathe takes some time and experience to master. The image on the right shows a mounting for the table on my small Pillar Drill, the thread is 14x1mm so that I can fit Unimat chucks and backplates.
For this I modified the Hobbymat with a handle on the back of the headstock spindle so that I could turn it by hand with the motor disconnected.
This allowed me to machine the thread right up to the stop, wind it backwards and then take the next cut.
I must admit that I finished the thread with a die.
Thread Cutting Calculator
Enter number of teeth on change gears and leadscrew pitch to calculate the pitch of the thread that will be cut.
Calculator works in mm or TPI.
Model Engineers Workshop No 40 has a comprehensive article on upgrading an MD65 for full threadcutting.
I guess this will be my first part to make on my lathe, a bushing adapter….!
Many thanks, Alex T
Yes, the original part is steel running on steel, but you could also make it from brass.
Interesting stuff, I was wondering how to put other gears on the change gear ‘banjo’ section. The pin that holds z1 + z2 doesnt take 2 gears with the same diameter bore, I am trying to attach 2 of the 60t gears…..
AJ
Hi Alex, the ‘banjo’ or ‘bobbin’ that takes the two intermediate gears on my MD65 is parallel and so takes gears of the same size. All of the gears are the same size. My lathe was from around 1982-84 I think, struggling to remember exactly. Best regards, Nigel
when I say all of the gears are the same size I mean internal hole ID
I am thinking of buying a Md 65 hOBBYMAT lathe. but it does not have thread cutting gears.I own a nice Emco 7 lathe. it has about 10 gears fitted, do I still need to get other gears to cut. I cant get info anywhere. I am very new to this and getting on in years. Please can you help. Regards Colin.
Hello Colin, I suppose the real question is whether you want to cut threads on the lathe? I must admit that I rarely cut threads and even then often use a tailstock dieholder as it’s easier. The only thing you might want gears for is the auto-feed. There is a modern version of the Hobbymat: SU 300 Masterturn and Pro Machine Tools sell this in the UK, not sure if they will sell you a set of gears, but worth asking. I use my HobbyMat for all sorts of turning in metal and occasionally wood and it’s lasted so well. Best regards, Nigel
Colin, Hobbymat MD65 change gears can be 3D printed, this would be the most economical approach. If you join the Prazi-Machining @ groups.io, there are 3D models for the gears in the files section.
If you’re in UK, you can contact EMCO Machine Tools (who sell the “Masterturn” SU 300). I put Masterturn in quote because I believe this is just a trade name it’s sold under in UK specifically. On the manufacturer’s website it’s just SU300. You can contact the manufacturer directly for change gears or other spare parts, the lathe is made by Teco Znojmo (a Czech company).