Replacement Chuck for Hobbymat MD65

[Keith FitchParticipant @keithfitch71047]

Good evening folks, I'm new here and this is a hobby so needless to say I'm not an experienced machinist, so please be a little gentle !

I have just completed fully restoring a Hobbymat MD65 which I inherited when a local company ceased trading.

The chuck is an 80mm 3 jaw self-centreing and showing heavy signs of abuse. I would like to replace it with something a little bigger, about 100mm or 125mm and scouring fleabay etc is full of chucks of various sizes being sold probably by people who don't know the difference between their backside and their belly button let alone dimensions and specifications of what they are selling.

My question is, has anyone done this kind of task before with a MD65 or is there anything I need to watch out for with this.

Many thanks in advance for your help and advice.

[Keith FitchParticipant @keithfitch71047]

[David George 1Participant @davidgeorge1]

Hi Keith is the original chuck mounted by studs screwed into the body of the chuck or has it a back plate which is screwed onto the back of the chuck with the studs in that plate. If the Chuck has a back plate you should be able to buy one from most places but check the sizes off location diamiter etc. If the chuck has studs screwed into the body of the chuck you will have to make a back adaptor plate to allow it to mount a new chuck unless you can buy a second hand original chuck.

David

[BazyleParticipant @bazyle]

I have a 100mm low profile independant 4 jaw for mine but it is a little large. I would not fit a larger 3-jaw than the original, especially if you need to make a match plate becuae you can't find one withthe oringnal stud spacing. If you need to hold something bigger than the existing chuck will take it is a good indication that you need a bigger lathe.

[John HinkleyParticipant @johnhinkley26699]

Keith,

I downloaded the user's manual for your machine and looking at the parts diagrams, it would appear that the lathe spindle has a flanged nose to which the standard chuck is attached. But then you'll know that, having taken it all apart to refurbish it. Unless you are going to replace like-for-like, I guess that you will have accept that you will need to undertake a certain amount of machining to ensure any replacement – especially larger – chuck is to fit well and correctly. I wouldn't personally go any larger than 100mm diameter on a lathe of Hobbymat size. (My lathe had a 550W motor fitted originally and really struggled with reasonable depths of cut and feed rates and was fitted with 125mm diameter chucks.)

If you decide to go bigger, you could do worse than investigate the possibility of modifying one of these from ArcEuroTrade. Have a look at these chucks, too, from the same source. Note the comments on the latter page:

" Note: Standard Mini Lathes have an 80mm chuck fitted on a spindle flange with a register of 55mm (dimension H). Some Mini Lathes have a 100mm chuck fitted on a spindle flange with a register of 72mm."

Good luck and welcome to the forum,

John

[John HaineParticipant @johnhaine32865]

When I bought my Hobbymat I also got a machineable backplate. IIRC the 3-jaw is held to the backplate by bolts which were a pig to insert since it had to be fitted when the backplate was on the lathe, that being bolted on too! So you needed to make sure that the new backplate wasn't too thick, hence one from the makers. I didn't think (maybe should have) of replacing the bolts with studs. If you're lucky there will be enough meat in the existing backplate to allow you to machine it to fit a new chuck.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Keith, the maximum diameter you can fit to the spindle flange is 100mm, as anything bigger will hit the motor guard, so if you want to fit a 125mm chuck, you will have to have a backplate that will extend the chuck mounting position beyond the guard, which is not really ideal. A 100mm chuck with a backplate that John Hinkley has said, would be OK.

Regards Nick.

[Roger BParticipant @rogerb61624]

Going bigger than 80mm may not bring you much. Unless you have a low speed attachment the minimum speed is 250 rpm. Clearance over the bed is 65mm so you will need to check the clearance of the jaws. This is an 80mm blank held in the standard 80mm chuck.

[Keith FitchParticipant @keithfitch71047]

Hello again and very many thanks for the welcome, help and advice. I'm so pleased I wrote in with my query as I would normally have dove straight in and bought a 125mm Chuck and been left with a useless paperweight.

what I have done today is spent best part of my Sunday on that ARC website, I have ordered a 100mm 3 Jaw and a a C3 backplate. All looks straightforward, with the only niggle is the backplane is bored through at 26.5mm but the spigot on my Spindle is 30mm. There is no image of the backplate and a dimensioned drawing would be fantastic, I'm hoping that this has a machined recess in it otherwise I'm going to have a hell of a job mounting a 100mm diameter backplane into an 80mm chuck.

I have another lathe, an Eliott Unimate SL I have had this since 1982, and recently I had to rebuild the Motor as the internal suppressor developed an earth leak and kept tripping the House ELCB. I took lots of pictures of the job with a write up as a chap up in Scotland wanted to rebuild his. If anyone wants to do the same I will give you the information and any help needed. Beware though, this job is not for the feint hearted, bit like mending a ladies watch in a teacup!

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Keith, your Hobbymat spindle flange should have a 56mm register as on 3 in the scan below.

This flange should never be removed as it is factory fitted for accuracy and your new backplate should be bolted to this. Unfortunately, The backplates that Arc sell have a register of 55mm, so you would be better to get the plain one and just skim it out to 56mm then mount it onto the flange and turn a register for your new chuck, but of course you will have to drill the fixing holes also. You may be able to skim the register on the fully prepared one, but I don't know how accurate it would be using the Hobbymat to do that.

Regards Nick.

[Keith FitchParticipant @keithfitch71047]

Thank you for your help and advice Nick, the 30mm spigot I refer to is shewn in the drawing is part of item 2. I stand to be corrected but item 3 is the backplane which is to be replaced.

as I said above, I hope this is machined in the rear of the backplane, but if not then I’m going to have machine it myself. I’m keeping my fingers crossed I can get 100mm diameter piece of metal into an 80mm Chuck, the original one on the Hobbymat.

once again, thank you.

Keith

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