Thread: Swivel Base Revisited

I had a good long look and think about any other ways, but I think you have come up with a good and possibly the only solution for those parts to be able to go into that T slot. Good thinking Bob.

Dave

Hi BT,
A couple of ideas,
Could you turn the tee slot in the lathe?
Would it be easier to turn a register onto the bottom of the piece that the dividing head mounts to that fits into the tee slot?
Couldn't you drill two holes from the bottom, one just big enough to pass the barrel bodies. Another much larger just into the slot to pass an over sized head tee bolt?(over sized enough that the centre of the bolt is pass one side of the barrel bodies hole before the head of the tee bolt clears the opposite side of the hole)
Stuart

A 2 piece T bolt, with the bottom part screwed to the top, would allow assembly from the bottom. It could also provide adjustment for the cam action. It would be bulkier, and some way of preventing the circular T bolt from turning once adjusted would be needed - maybe a nylon friction insert?

Jordan

Going off the pictures Bob posted, it doesn't look like there is much room in the base for a larger T slot, and there is not much meat between the reduced shank part for the T bolt and the cam hole. Seems like it's a tight squeeze to fit it.

Someone posted pictures of a Taiwanese lathe a while back where they come with just holes in the T slot for the compound bolts to get in. They where having trouble with the T bolt chewing the edges of the cast out around the holes when set at that angle. At least with Bob's fix it would have the patch piece to give even pressure either side of the T bolt.

Dave

The only alternate that I can think of at the moment is to make the interior of the T slot bit a disc and bolt it in with some SHCS after putting in the inserts. That notch and cover arrangement looks fiddly and if the T-cam were right under it, it probably would not secure much.
Another option is to have a hole in the top that the T can be fed into in the least popular place - say at 80 degrees to the main axis - how likely are you to ever want to position something there (and with symmetry you can mirror things so it does not matter if you did.)

Michael

I like Michael's idea of a bolt on mushroom. You'd get 4 or even 6 nice big screws in and it would be very secure and uniform.
Edit: Actually he said disc and that's probably all you've got room for.

Dave, Michael, Jordan, Stu and Bryan, thank you for thinking about this.

The bolt down disc is a pretty simple solution. It needs to be able to slide aside to allow the tee bolts to be installed. The centre bolt would provide alignment of the two major components.

I had considered a two piece tee bolt but the present 5 x 20 base ( proposed nut) of the bolt would need to be thickened somewhat to provide reasonable thread engagement with the resultant thinning of the material below the tee slot. Then a locking device would need to be devised.

Stu, holiday over? A integral register is something I have to think about. It would prevent the upper section from being mounted directly onto the mill table should the need eventuate.

BT

Originally Posted by nadroj

A 2 piece T bolt, with the bottom part screwed to the top, would allow assembly from the bottom. It could also provide adjustment for the cam action. It would be bulkier, and some way of preventing the circular T bolt from turning once adjusted would be needed - maybe a nylon friction insert?

Jordan

Hi Jordan,
Not sure if this is along the lines of what you where talking about.

Bob what about something like this. The bottom could be screwed on and a few drops of Locktite would hold it there forever. The small shoulder would locate it for length.

Dave

Originally Posted by Dave J

The bottom could be screwed on and a few drops of Locktite would hold it there forever. The small shoulder would locate it for length.

That's one way, or the other end could be threaded.
Another idea: One piece, but using a modified oval shape to engage the T slot. Its width narrow enough to fit through from the top, and its length and shape sufficient to provide adequate clamping area when rotated to its working position. The hole for the cam would be offset by an angle, such that when it's in the correct position so is the clamp.

Jordan

I'm working through the suggestions.

JP,

I made a skewable nut for my table adjuster and while it works well in that application, the amount of engagement available is a bit limited on this current project. I will explore the idea further though with a drawing. Here's the two part tee bolt. The thread would be M8. Loctite is easy but makes dismantling a problem. Maybe a M3 or 4 socket set screw with a brass pad might be a better option.

BT

Hi BT,

I don't have any better suggestions that those you've already got,
But I like Jordan's two part T bolt idea, instead of a locking screw, you could use loctite thread lock ( a little less permanent than loctite 401 )and mill a screwdriver slot on the bolt head.

Regards
Ray

A little locally applied heat destroys the Loctite bond.
It doesn't need to be so hot as to affect the metal parts.
I guess it's not as nice as a purely mechanical solution.

Or, what about a very wide slot, so the bolt doesn't need to have 3 diameters, only 2 with the top part large enough to engage the cam.

Jordan

Originally Posted by nadroj

Or, what about a very wide slot, so the bolt doesn't need to have 3 diameters, only 2 with the top part large enough to engage the cam.

Jordan

I will sketch up a version incorporating that idea tomorrow Jordan.The tee slot is located within the 80mm width of the upper mount to exclude swarf. Room may be at a premium.

BT

The non waisted tee bolt as per Jordan's suggestion. I now have to work on a way of holding the two major parts together whilst providing accurate rotation.

BT