Fitting chucks to 7 x 12 type baby lathes

[old martParticipant @oldmart]

I have great difficulty changing chucks on my little lathe. There is not much room to get 6mm nuts between the headstock and the spindle flange with my very arthritic fingers. The original chucks got changed for Sanou 80mm three jaw scroll and a 100mm four jaw independent which are slightly better. The 100mm was made front mount and the rear register was bored to fit exactly the same as the original 80mm four jaw. I was thinking that with a 90mm diameter by 20mm thick steel bar offcut, a split backing plate could be made with tapped holes inline with the spindle flange holes. The backing plate would have SHCS clamping the halves together across the split. I could get a piece of en24t in this size easily, or possibly use aluminium with Helicoils in it. Making the 80mm front mount is a piece of cake, simply drill the body through the rear mounting holes with a 6mm and counter bore for SHCS at the front. The holes are outboard of the scroll and not near the jaw slots.

[DiogenesParticipant @diogenes]

I guess the plate wouldn’t really have to be any thicker than the original nuts.

A thinner ‘ring’ could be made-up with lap joints and ‘re-assembled’ using something like 2.5mm SH countersunk screws (?done up through the flange holes). They only have to hold the halves together when it’s ‘loose’.

Least fiddly option would be to fit a one-piece ring if the spindle ever has to come out.

 

[Howard LewisParticipant @howardlewis46836]

If holding the nuts, either to fit or to remove, you make and use a “Danny M2Z Widget”

He posted this gadget a long time ago in M E W.

It is quite simple, and works beautifully. It prevents the nuts being dropped, and holds them in the small space where they are inaccessible even to flexible fingers.

Just a short piece of strip steel with two sheared cuts, about 25 mm long at one end (6 mm apart) with the central tongue filed to a coarse taper point, and then about 6 mm bent down at right angles.

Having slackened the nut, the widget is slipped behind it, and as the nut is slackened further, the point enters the nut and retains it, against the flat strip. When fully off the stud, you just lift out, remove the nut and repeat with the remaining two nuts.

For fitting the nuts, load to the widget and offer up to the stud and start rotating the nut to engage the thread. When well engaged, disengage the widget and repeat the procedure on the other two studs, and the tighten the nuts fully.

If you can’t find the short article, PM me with an E mail address, and I’take a photo and  send it to you.

Howard

 

[old martParticipant @oldmart]

Too late for any widgets, I made the ring from Aluminium, using up about 3/4″ of the end of a 4″ bar that I had bought, but cannot remember why, old age getting the better of me. The 80mm chuck body got the front mount modification. The ring was cut in half after everything else was complete, including the 6 off 6mm threaded holes. The photos show the plate viewed from the side that sits against the lathe spindle flange, the other side is plain and the threads are 10mm in length. The length of thread in quality aluminium did not require Helicoils for the ammount of chuck changing I will be doing, and the SHCS are 62mm long, both chucks are the same thickness.

[old martParticipant @oldmart]

This is what the 100mm four jaw looks like with the backing plate. One thing which has helped chuck fitting is to drill the holes through the chuck body for the 6mm SHCS to 1/4″.

 

 

[Ian PParticipant @ianp]

I dont have a minilathe but I understand that normally there are studs sticking out of the back of the chuck that pass through holes in the spindle flange. Seeing your front mounted chuck conversion (which make a lot of sense) why not just drill and tap the three (or four) holes in the flange itself so the split aluminium parts is not needed?

If the flange does not have enough meat for decent threads then it would be straightforward to make ‘hank bushes’ and set them in two halves a large ‘washer’ that sits behind the spindle flange. The washers would stay on the spindle during chuck changes if the flange holes were slightly countersunk to accepted suitable reduced head countersunk fixings. I am assuming that the flange and half washers would be drilled and threaded for 3 and 4 jaw chucks. so whichever particular chuck was in use there would always be the unused threads available.

Or am I missing something?

Ian P

[old martParticipant @oldmart]

The spindle flange already has six holes of about 7mm in it and for direct threaded holes to be added could be done in situ with a round drilling jig, and careful positioning. I don’t know how hard the flange is for tapping, that would be a factor. Doing this mod to a spindle that was removed from the headstock would be simpler. The alternative would beto increase the size of the existing holes for captive nuts. There arealways a variety of solutions to these problems.

[Ian P]

On Ian P Said:

I dont have a minilathe but I understand that normally there are studs sticking out of the back of the chuck that pass through holes in the spindle flange.

Ian P

Sadly not on mine when I got it. I had to pass M8 cap head socket screws through the back of the flange into threaded holes in the chuck and use a cut down hex key. I’ve since fitted studs to all my chucks as you mention though. Luckily the counter bore on the back of the flange isn’t an issue for the M8 flange nuts I use.

[old martParticipant @oldmart]

The picture of my front mounted 100mm chuck does not show that the chuck had been turned and bored in a larger lathe to get the correct counterbore to fit the mini lathes flange as well as producing the front mount holes. The 80mm size four jaw independent chucks fit right on with the rear mount, but I don’t know whether they could be made front mount like the 80mm three jaw scroll type.

[Author]

Posts