Hobbymat MD65

Hi,

Dave here, I need a little bit of help on my late fathers Hobbymat MD 65 Lathe.

I am trying to swap the Tailstock Chuck for the Centre Spindle.

(not sure if the terminology is correct here)

The Chuck appears to be stuck in the bit that goes into the Tailstock.

I was advised to lever it apart but all I've manged to do is remove the Chuck Head from it's own shaft and it's still attached to the piece that goes in the Tailstock.

I am of course assuming that these parts are interchangeable and one simply wedges/levers or applies brute force to change the mover.

Just kidding on the brute force bit.

Any advice would be greatly appreciated.

There should be a threaded hole in the end of the quill (the bit with the graduations on it). The thread on the hand wheel goes into this and pushes the tapered part out as you wind the quill back into the tailstock. If the chuck has been in place for some time some heat may help.

I keep a length of brass rod to wack it down the quill.

While it's in bits spray some WD40 down the hole and let it sit for a while. Re assemble and then just wind the quill all the way back. The chuck taper should be self ejecting.

Machine tools often use tapers to attach chucks and other accessories. They wedge into a socket and grip tight enough not to spin or fall out. (We hope!). As the taper angle effects the grip, they can be made self-holding or self-releasing. (See Machine Tapers on Wikipedia).

Tapers work well, but sometimes they come apart by accident, and sometimes they stick solidly together. David's chuck has come off the arbour unintentionally: no problem, it's allowed. When the time comes just push it back on firmly.

The other end of the arbour is stuck in the tailstock spindle. Five common causes:

• The taper was wedged too firmly in the past by applying excessive force, perhaps a hammer! (Don't.)
• A cold male taper was pushed firmly into a hot female (yikes!), forming a shrink fit when the lathe cooled down. This can happen when a lathe is thoroughly warmed up and a cold tool is pulled out of storage. More likely to happen at the headstock end because the bearings warm up, and cutting heats the chuck.
• The taper was lightly oiled and gummed up over time.
• The taper wasn't lightly oiled and corroded.
• The taper was inserted dirty and is jambed by a bit of swarf.

You might like to soak the stuck parts in penetrating oil for a day or two. It removes gum and loosens corrosion.

Normally, winding the tailstock spindle back beyond zero will cause a tongue to press on the taper and eject it. Not all tapers fit properly, so this may not be working on your lathe. Try inserting a rod through the hole and, gripping the spindle in one hand, rap it sharply on a wooden bench to push the taper out. Nice thing about owning a lathe is the rod can be turned to fit, if necessary.

If that doesn't work, try supporting the shoulders of the spindle in a vice (with the chuck hanging freely below), and tapping the rod with a hammer. Note a sharp tap is essential because prolonged slow pounding will damage the spindle. Don't overdo the violence!

Heat is the most certain way of loosening a stuck joint. Apply a blowlamp or electric paint stripper to the spindle and heat gently : not red heat or anything like it because that will damage the metal, hot enough for spit to dance on the surface. Let it cool down and try rapping again. The metal expanding and contracting causes enough movement at the joint to gradually loosen whatever is jambing the wedge. Several cycles may be necessary. Not tried it myself, but some report success by cycling with boiling water and a deep-freeze. As the temperature swing is smaller than can be done with a blow lamp, I guess more cycles might be necessary, and the process will be slower because the freezing part must take a few hours. No need for a blowlamp, and no risk of damaging the metal by overheating.

After separation, give both genders a good clean. As they are a precision fit, nothing aggressive. Ask again if the problem was corrosion or the tapers are obviously damaged.

Dave

Wow,

Thanks a million your advice is greatly appreciated.

I have no idea if my dad was a bit "heavy" handed with the chuck but I think I'll go with the "it's been stuck for a while" angle.

Yes I have tried WD40 and a light tap or two with it perched in a vice and also winding it all the way back and a touch more whilst in the Tailstock but it wouldn't give.

I did ask the machine shop where I work this afternoon if they could take a look at it for me (I'm in the office) and they said bring it in.

Fingers crossed I can report a "clean separation" tomorrow arvo.

Cheers, DaveT

Forget WD40 get some Plusgas ideally the liquid not the spray

Roy

+1 for Plus Gas Liquid (Now in a black tin not the traditional blue) - WD40 is at best a spray lubricant and water repellent, not a dismantling fluid

Hi All,

Thanks for the tips. Handed the Spindle to the workshop & 5 mins later it was returned separated.

Sometime in the past someone thought it a good idea to cut a bit of the Taper off. No idea how, why, when or where but this explains why I couldn't just wind it out of the Tailstock.

Now I can get back to tinkering with my new (old) toy.

Appreciate all the advice given.

I will be getting me hands on some Plusgas ... just in case

Kind Regards ... DaveT

Good that it is now separated! It looks like it needs a little bit of careful cleaning on the inside of the taper as there seems to be some corrosion as well. Maybe your machine shop has an MT2 taper reamer that they could give it a very light scrape with?

There is a bit of surface rust inside the taper of the quill, so yes all three pieces will need a little tlc.

The chuck shaft is quite a bit shorter than the centre so I will have to keep a piece of rod handy for when I swap the over but that's no biggy. Just happy to be able to start the final cleanup prior to using it.

The Lathe pic attached is just a dummy setup, it will give me an idea where to bolt it down with clearances and accessability to the belts etc ..

Thanks John, I'll ask tomoz if they have reamer.

People shorten the taper because they get annoyed by the item ejcting before the tailstock barrel retracts back to zero graduation. But it can backfire as you found. Use a ball bearing to make up the difference - it just rolls out after use.

Ah, now that makes sense, thank you.

I'll use it for a while to see how i go before deciding to do anything.

All too easy to chop a little too much off the end. You can guess how I know!

I might try cleaning up the bore with a piece of hard wood / 'coarse rag on a stick & vinegar' or similar before resorting to the reamer - the spindles and shafts are of very soft steel on the Hobbymat. If you do need to ream, go very lightly, just the tiniest skim. The size is 1MT.

The arbor looks long enough to be gripped in a chuck.

If the arbor is too short to eject, it may be possible to drill and tap it.

Insert a short length of threaded rod, or sacrifice a bolt, so that the "extension" is just long enough to make contact with the ejector.

This has worked for me on several occasions.

Howard