Proxxon DB250 3 Jaw Chuck

[mrcc]

Hi all...

 

I purchased a used Proxxon mini lathe, all in excellent working order with the exception of the 3 Jaw Chuck being very stiff, almost to the point of being seized up, when trying to open or close down the jaws. I tried to lubricate the exterior elements but no success at all.

 

I went online to see if it was easy to lubricate and service the chuck but absolutely no information there.

 

Any suggestions would be very welcome by any and all reading this post.

 

Thanks!

[mtaylor]

If this is like most mini-mill chucks, usually you can open them to the point the jaws can be removed so that everything can be lubricated.   Note that it does take a bit of fiddling to get them back in place exactly.

[GGibson]

Hi Julian - Not sure if this helps any, but... I have the 3-jaw chuck that I bought when I either bought the Proxxon drill or the Proxxon mill, and the chuck does open very "stiffly".  Did your purchase come with one of the turn handles shown in my first picture?  Using that really helps opening and closing, especially after tightening against whatever you are securing (and the subsequent release of said object). 

 

Also, if by chance you removed the jaws from the base, make sure you put the jaws back in the right spot.  In the second picture, you see that the jaws and the base have 1-2-3 numbers.  Apologize if you are already aware of this numbering, but wanted to point it out.  But, did want to confirm that, yes, the chuck does open hard.

 

Let us know how you like the lathe!  

 

      

[mrcc]

Thanks Mark, Gregg for your replies… much appreciated!

 

My chuck did come with the turn handles as indicated in your pictures and yes, aware of the numbers referencing the corresponding jaw to the numbered base.

 

Besides my real perception that the chuck is very stiff on opening or closing, is that on viewing YouTube videos on the operation of the DB250, it sure appears that people easily manage the opening and closing with minimal effort with the aforementioned keys/handles. 
 

I just thought there was an easy way to open and service the chuck with lubricant… and on looking at the chuck, there does not appear an obvious or easy approach to the service (if truly needed). 
 

Thanks again!

[mrcc]

PS Turned a small mast and boom and yes, love the machine. 

[CPDDET]

I have a Sherline chuck and Sherline does have instructions on tear down, cleaning and maintenance of it. This may be of assistance to you.

Simply Google "Sherline 3 jaw chuck maintenance" and you will find a youtube video on the process.

[mrcc]

Bingo... it looks like the Proxxon chuck is similarly designed and engineered as the Sherline (mini chuck anyways).

 

Thanks CPDDET!

 

Looks like I need to buy a snap ring plier though...

 

Also looks like the jaws perhaps were not installed (by the previous owner) correctly as per the numbering pattern.

Perhaps that why it is so stiff to open and close the jaws.

[mrcc]

Update: Reached out to Proxxon USA and they advised me not to take apart the chuck and that with removing the jaws from the base (which I did not know it could be done), there is more than enough room to apply a penetrating oil to remove the thick grime between the base and rotating plate, which should allow easier movement of the jaws.

 

Cleaned up the jaws already and tonight will get the base cleaned up... 

 

Jaw 2 is marked 2 on each side and will fit in the original 2 slot of the base but the other two jaws are not as clear in my mind where to place as they have markings of 1 or 3 on each side presuming that 1 will face the 1 on the base and the 3 on the jaw facing the base 3 along the circumference skipping the 2 slot. Not sure as I want to flip the jaw from the original position I received the used chuck in.

[CPDDET]

Things shouldn't be this difficult. Might take some trial and error.

Keep us posted.

[wefalck]

These are called 'scroll-chucks' because the bottom part of the body has a spiral milled into it in which the 'teeth' of the jaws run.

 

Of course, swarf tends to get into the spiral and can block the jaws. It's worse with wood dust, as this soakes up the oil and forms a tough mass.

 

Once you have taken out the jaws, you can take a toothpick and while turning the chuck you run it through the spiral inside-out, which pushes the swarf out of the spiral. Do this with each edge of the spiral, i.e. two passes.

 

[bruce d]

For reassembly of scroll chucks I have found that copper grease is ideal.  Use only a tiny amount.

 

Bruce 

[CPDDET]

Sherline recommends Super Lube for its lathe and mill.

[wefalck]

Personally, I think oil is better on scroll-chucks, as grease together with swarf may clog up the rather tight-fitting spirals. I have never used grease on my half dozen or so of different scroll-chucks.

[mrcc]

Thanks for all the information… great for the next person struggling to find a solution as there was absolutely no information on the internet specific to this proxxon chuck anyways.

 

PS Proxxon USA (in an email yesterday) recommends using a penetrating oil on the “spiral milled on the base”. 

[Pirate adam]

I use something called 3 in 1 oil on my Sherline chucks. One thing to keep in mind is that no matter what type of oil you use some will inevitably fly out when you turn on the lathe for the first time.  It is worth making sure nothing is in the area that you don’t want to get oil machine oil on. 
 

Adam

[mrcc]

Good advice... I will throw a towel over the chuck on its first operation.

 

Cheers!

[Cmm4000]

Hi Julian,

Looking at your first picture it looks like jaws are in backwards the taller part of the jaw should be towards the center of the chuck see the picture that GGibson posted above. The jaws are taller towards the center of the chuck.

Curt

 

[mrcc]

Thanks Curt... yes I will rectify that once I put it all together again.

 

Cheers!

[wefalck]

6 minutes ago, Cmm4000 said:

Hi Julian,

Looking at your first picture it looks like jaws are in backwards the taller part of the jaw should be towards the center of the chuck see the picture that GGibson posted above. The jaws are taller towards the center of the chuck.

Curt

 

Actually no. I the jaws are reversible as in almost any chuck like that. When the steps are facing inside, you can work on larger and flat items. 

 

Other chucks may be delivered with two sets of jaws instead.

 

And: keep towels away from revolving chucks, this could result in a serious desaster otherwise.

 

Also: never work with gloves and loose clothing on a lathe (or mill).

[mrcc]

Agreed...

 

But with my primary purpose being to work on dowels; masts and yards, better to have the jaws with the tall end facing in

Edited December 5 by mrcc

[Cmm4000]

Yes,

I was going under the assumption he was working on round stock.

[wefalck]

Talking about machine tool safety: as far as I am aware the DB250 comes with a set of collets of up 10 mm. This is a much safer and more precise option for working on round stock up to that diameter. There is no risk that your fingers or your tool collides with the chuck jaws ... I use collets almost exclusively on my lathes.

[mrcc]

Thanks Wefalck... interesting comment about the collets and yes I have them for the machine and many very well take your advice.

[Dziadeczek]

Those numbers refer not only to the correct placements of the jaws in the chuck, but also the proper sequence of reassembling them. Start with jaw 1 by placing it in the chuck in the place marked as 1 and slowly turn the chuck until the jaw engages. Immediately after, place jaw 2 in its place marked as 2 and proceede with turning the chuck until jaw 2 engages (jaw 1 will in the meantime engage further on). Finish with jaw 3 in the same manner. Otherwise, all jaws will sit in the chuck incorrectly and too tight!

At least, that's the situation with a chuck from the Sherline lathe.

(I would spray WD 40 for the jaws and the chuck to loosen and remove grime in crevasses before reassembling them and then lubricating everything slightly).

[mrcc]

Thanks! Lots of very good information there…

[Dziadeczek]

This is the original Sherline instruction on how to disassemble and reassemble the reversible jaws from a 4 jaw chuck (which I would encourage you to obtain from Proxxon in addition to your 3 jaw chuck, because in certain situations you'll need the 4 jaw chuck to be able to machine, for instance a square or octagonal stock, or similar...).

I have both of them for my Sherline lathe.

Perhaps the situation with the Proxxon chuck is similar with the one from Sherline?

 

 

Edited December 6 by Dziadeczek

[mrcc]

Thanks… absolutely no instructions in this regard from Proxxon whether online or in print.

[Dziadeczek]

I found this video on the YouTube.

Activate English subtitles, if you don't speak Russian.

[wefalck]

Keep in mind that the DB250 is a small wood-lathe with only 40 mm centre-height. The Sherline-chucks are designed for much heavier metal-lathes ...

 

The spindle-thread on the DB250 should be 16x1, not sure that Sherline would offer chucks with such a thread.

 

There may be several aftermarket options of Chinese or Indian origin for centric or independent 4-jaw chucks at moderate prices, but they typically have either 12x1 or 14x1 threads, I think.

 

PROXXON offers a plastic independent 4-jaw-chuck, which would be quite adequate for wood-work.

 

As long as you work from stock, the run-out of a chuck is not really important. The part in itself will be true in all its diameters. Run-out only becomes relevant, when you want to perform so-called 2nd operations, i.e. when you inverse a piece and want to work on its unmachined side.

 

Setting up an independent 4-jaw-chuck can be a real pain and is time-consuming. You normally would need a dial-indicator to check for concentricity (there are other approximative methods). However, this can be the most precise option for 2nd operations. Not really needed for most wood-working applications.

 

[davyboy]

19 hours ago, mrcc said:

Good advice... I will throw a towel over the chuck on its first operation.

 

Cheers!

Not a good idea,think about it. Throwing a towel over a rotating chuck or for that matter any rotating object 

 

Dave