Hobbymat lathe - couple of questions

Hello all, new here and hoping for some advice on a Hobbymat MD65 lathe I got recently. When I searched generally I got a lot of good advice from the model engineer forum already but have a few more questions I hope the membership can help with. This is my first lathe, although I have used a few bigger under guidence...

First question is on jaws, removed the chuck for a cleanup and on anticipation of receiving a set of external jaws I have ordered which I hope will fit. The lathe came with internal jaws - how important is the numbering for this little lathe? Embossed in the chuck and jaws are the numbers, but when I took the originals out they were not corresponding - hop the pic works.

Second question I have is on change wheels, I still need to work out what is installed, it did not come with any others. Are the change wheels for this machine still available?

Many thanks, Chris

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Edited By JasonB on 28/12/2019 06:50:01

All that really matters is that they go in 1-2-3 order anti-clockwise and that no1 engages first. On a small chuck like that I put the jaws in, hold a light pressure inwards with one hand and turn the key backwards until no1 jaw pops over the end of the scroll then wind them in with the key.

Hi Chris

Some chucks will come with matching numbers on chuck body and jaws, this indicates they were finish ground as a matching set.
It is not always the case though but at least have the same numbers on all jaws showing a set, not just 3 jaws.

Looks like your jaw numbering in black does not agree with the number 1 stamped in the chuck body with your 2 marking, best try them in correct order starting from the marked No.1 location, could be less runout than other positions.

Emgee

Because they are engaging with a scroll the teeth on each jaw are different. They have to go in the right order and are best fit in the corresponding slot. However if the previous owner swapped them they would likely have a different number where they were the best fit so they may have numbered them accordingly.

Changewheels are only available from ebay I think and likely to be at inflated prices. You might want to investigate using a complete set from a mini-lathe which are more readily available and reboring to fit. You probably can't mix types though. There are commercial gear suppliers like Daval but that is an expensive route.
You might like to measure the diameter one of the ones you have and post on here asking a mini-lathe owner to give the dimensions of the corresponding one.

Edited By Bazyle on 28/12/2019 11:44:24

Pete, Emgee, Bazyle, thanks very much - I have learned some things right there! I will go with corresponding numbers.

I have ordered some external jaws from "Bang Good" being shipped from Germany, a few reviews I have read look like they will fit this model chuck ok.

Thanks for the advice on the change wheels, I will start investigating.

Many thanks.

Hi Chris,

The gears are plastic, it might be possible to get some 3D printed, if you can find out the data on the gears needed.

Cheers Chris, that's actually a good idea, I have a friend who has been doing a fair bit so may ask, also aware that prices are coming down for 3D printing but have found this link on lathes.co.uk, not sure how valid it still is but may be worth me checking once I work out what I might need.

**LINK**

Cheers

Chris

The gears appear to be 1.0 MOD, are 10mm thick, and have a 20mm bore which is slotted to accommodate a 4mm key.

(50T gear=52mm OD, 60T=62mm, 70T=72mm, = 1mm of PD per tooth plus the addendum (= to mod) on each side).

I can't establish the pressure angle exactly from my worn examples, but 20 degrees seems the most likely to me - it's a "modern" metric machine made in Europe, for those not familiar with it - additional informed comment or confirmation would be very welcome, here.. (..although if you are going to get a set printed, it's rather immaterial in any case, as long as they are all the same.).

You will need; 20, 30, 35, 40, 50, 55, two 60's, 65, 70, 75, and 100, if you want every option listed on the plate. Even for common metric threads you will still need 30, 35, 40, 50, two 60's, 70, 75 & 100. A 20 is "nice-to-have" for a fine finishing feed.

I'm not familiar with the mini-lathe change-wheel sets, but do be aware that the Hobbymat uses a 1mm pitch leadscrew, which I think is finer than that fitted to ?most mini-lathes and therefore the ratio between headstock-spindle-turns versus amount-the-carriage-advances will be different.. might be worth doing the maths/checking the tables before buying any gears, just to make sure that you will be able to achieve the ratios that you need.

Good luck!

Thank you D. I have made a note of this. I won't be screw cutting for a bit which is just as well as it' seems a bit of a convoluted process on this but I have determined the gears I have.

Best Chris

Hi Chris, the Hobbymat is a very capable and accurate lathe.

The photo shows my change wheels for my Hobbymat, which is the same model as yours, if you do get the urge to screw cut this is the set you will need. I haven't shown the change wheels which are on the machine because it is under cover in the shed, but they should be the same as yours.

That three jaw chuck by the way is probably one of the best quality chucks around, hope you find the outside jaws for it.

And that yellow angle plate converts into a very usable mill. Just take off the top slide and bolt to the cross slide. Also a tee slotted aluminium plate was supplied with the machine for extra versatility, so the little vice could be bolted to it. Interesting that you also have the steady too.

Ian

Observant readers will notice the top left wheel has a smaller bore. The normal bore is 20mm so they can fit on the rear of the mandrel then also are put on a bush for other uses. But the 20 tooth mentioned in Diogenes's list is of course smaller than 20mm! It has a special bush of its own to account for the small size. It may be that you have that little one but if not it would be the first one to make when you summon the courage as its primary value is it give a high reduction for fine feeds.
I suggest one of your first projects even before a mandrel handle is an extension rod drilled and threaded to replace the nut on the belt tensioner to make it super easy to loosen so you aren't tempted to make do with the wrong speed.

Did you get a 4 jaw chuck with it? Chronos used to do a 4 in one that fitted the flange and screw holes exactly but that was about 35 years ago when they were selling the lathe.

I bought a 4-jaw chuck for mine from Chronos but had to make an adapter. Do you have the instruction manual? If so, it shows the various configurations for milling etc., and, very important, the correct way of adjusting the saddle and tailstock to the 'D' shaped bed. Be careful not to strain these by not adjusting the fit correctly.

The Hobbymat is a very useful lathe and, with a bit of ingenuity, is capable of doing work beyond its designed capability. Once you have a full set of change gears, it is quite easy to make an extended change-gear bracket to extend the range of threads that can be cut to include the finer threads like 40tpi.

Alan

Edited By AlanW on 30/12/2019 14:59:21

Hi Ian, thanks for this feedback, the chap I bought it from who is an excellent engineer had very good things to say about it, He had had it for over 25 years from new. Thanks also for the picture of the change wheels, looks like I will be needing close to a few hundred quid to acquire them all close to what I got the lathe for...

I have not fitted up the mill plate yet, cleaned up a lot and lubricated per the manual (yes I found a download!) I also gave it a partial paint with Hammerite smooth as it was a bit of a state aesthetically when I first got it but mechanically all seems very good. The yellow Hammerite is an excellent close match.

If you have a picture of the T slotted plate I would appreciate it, I would hope I could make that. It came with the steady, the wee vice, the mill adapter and a face plate! all of which took a fair bit of going over.

I have ordered a fixed and dead centre and the external 3 jaw set should be with me soon so will post if they work out ok.

Hi Bazyle, it did not come with the smaller bush, if anyone has dims for that it would be appreciated and on the list to make. Also noted on the tensioner tool, very good idea and will get onto that.

I didn't get a 4 jaw with it, would that be 100mm s/c upgrade?

Hi Alan, I do have a downloaded manual for it, probably being a bit thick but don't find it very well written / laid out, but its fine.. Yes I noted the warnings in the manual and also on the Lathes UK site regarding care of adjustment to tightening up sequence and relative pressure. Thanks for the advice on the extended change gear bracket, another project!

Sorry for the long winded reply. Cheers Chris

Faceplate after blasting..

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Although not on their website anymore this company used to supply parts for hobbymat and also made and supplied a slow speed adaption that gave it 50 and 70 rpm. They may be able to help.

essel engineering

A few hundred quid!!! I've not had a look at Hobbymat change wheel prices, that seems a like a lot of dosh to spend on plastic gear wheels! In the photo is a 50 tooth change wheel from my Mini Lathe, next to it is the Hobbymat 50 tooth wheel. both of them are 1 module gear tooth profile.

So I was thinking is it possible to buy the much MUCH cheaper Mini lathe change wheels (Arc Euro sell them) and bore them out to suit the Hobbymat?

Couple of problems though! the wall thickness will be a lot thinner after boring out, so maybe some sort of bushing might be needed? And the keyway will need to be made too. Another problem is that you won't get all the correct number of tooth wheels so you may need to search for an alternative.

Apart from that, the plan is perfect!

Oh! nearly forgot here is a photo of the tee slotted plate, hope you can make out the dimensions

Ian

What gears are you missing Chris? If you can get some delrin and cut the blanks I'll put the teeth on them for you no problem. They'll work just fine with the ones you have and be a good bit stronger I expect.

Well reminded, Bazyle -

The 20T gear carrier comprises a simple stepped cylinder 21.7mm long. The central bore is 8mm (ream if possible).

The larger part of the component has a diameter of c.19.98mm (light push fit for a 20mm bore) and is 10.2mm long. It has 4mm wide key slot, 2.6mm deep (which could be formed by hacksaw and file if necessary - aim for perfection, but settle for adequate - it doesn't run at high speed or take a great load, and mates with a moulded component).

The reduced part that carries the 20T gear is c.13.6 to 13.7mm in diameter (mine is firmly fixed and I'm not going to prise it off!), the dimension isn't critical as the gear is permanently affixed by pressing onto the carrier, so make matched components - aim for a fit that requires say, light vise- rather than finger- pressure, but without "stretching" the gear too much - again, a tiny inaccuracy here isn't the end of the world as running clearance is established whilst setting up the gear train in any case. If one could arrange a parallel knurl, this would be exactly the job for which that process is intended, but failing that any knurl would probably do.. An adhesive might do, but I'm not sure that all are effective on plastics - advice welcome!

The gear should be 11mm thick, leaving 0.5mm of the carrier projecting beyond the face to provide axial clearance for the gear once the carrier is secured to the stud with it's screw & washer.

Both outer edges and the ends of the internal bore should be generously chamfered, for ease of fitting, to reduce friction, and to allow the ingress of oil.

In order to cut the blanks for any of these 1Mod gears, simply take the number of teeth required and add 2 to arrive at the finished diameter in mm - thus 30T = 32mm, 60T=62mm, 100T=102mm etc. With the exception of the 20, which is 11mm, all the others are 10mm thick.

I'd get a piece of Leaded ("free-machining" Bright Mild Steel Round Bar (EN1APb) for this job (I note the standard item is "soft", probably to save wear on the studs), and it's an exceptionally pleasing material to work with.

Edited By DiogenesII on 31/12/2019 13:38:05

As these are just hobby lathe change gears IMO t'aint worth the cost and effort of making them in metal.

option 1 the hard way - as you suggest, purchase a set of nylon minilathe gears - bore and bushed to suit but the bushing will need to be keyed to the bore in the gear. You wont get the whole range, but most of them. you could start just with the few common threads you think you are likely to use.

option2 my lazy way - acquire a cheap 3d printer, download a set of minilathe gears STLs from thingiverse, ,modify them to suit in Tinkercad and print whatever you want. You will suddenly find a myriad other things to print such as soft over jaws, chuck spiders, nudgers, dial clamps, angle gauges, micrometer holders etc etc too many to list as they say.

Hi Ian, thanks a lot for this, the dims are perfect but could you advise on depth before I order the plate please? I am guessing 20mm? - many thanks in advance!

Hi Pete, that would be great and really good of you. I have added up from lathes uk that a full set of gears would be well over £200 and actually they don't have them all. For the the bigger wheels its all 8mm.

A slab of delrin 1000m x 125 is a 1/4 of that cost but I need to work out (get the boy) to cut the blanks, if I can get him t commit I will order the delrin

Many thanks Chris