Thread: removing a j head with a table mounted fixture?

Greetings everyone,
I have a few questions about removing a j head by means of a table mounted fixture.
The 'fixture' in question would be a piece of bar stock of some kind welded vertically on end to a piece of plate and gusseted up vertically. Plate would be bolted to table via toe clamps and or t nuts, drill chuck or collet could be tightened down on the vertical bar stock, once everything was locked down the 4 head removal nuts could be loosened and then using table feeds head can be slid off with ease...or at least in theory, and repositioned for re install seemingly just as easy.
so, how bad for the spindle bearings would this be? any other issues im not considering?
and finally if this is an ok method, i understand it may not ideal but if its ok, what method would be best for attaching the bar stock to the head, drill chuck? collet?

thanks in advance

That's how I've removed Bridgeports head for 30+ years. I have a plate with a 1 1/4" stub shaft welded in it that I mount in a end mill adapter, then I crank the knee up until it flush on the table and toe clamp it down. If the machine has a DRO I set zero on the X, Y, remove the four nuts and back the Y out. When it time to install just crank the X back to zero and move the Y in a little at a time until you get the studs started in the holes then crank it back.

Why are you removing the head? If this is only for the occasional work I dont see this as worth the effort. If you have a need to do so regularly, I would find a more solid method of mounting your fixture to the head. Maybe a sling and chain hoist?

When I need to remove the head (rarely) I simply flip it upside down and bring the table up (with a piece of plywood on it), hold it with one hand and remove the four head bolts, slide it off of the counterbored shoulder, and lower the knee with the other. Once I get it below my belt I then either slide it onto a cart or just muscle it wherever it needs to go.

You mean like this
Mill Head Removal Post
JR

haha! yup exactly like that one!

as to why remove, its a likely bad worm drive in the head so rotating down isnt currently a one man show.
Head either needs removed or rotated to fit in the doors anyway and it can be taken apart where it sits now (buddys shop) so figured i would go ahead and completely remove both head and table to help with moving.
so how bad is this for the spindle bearings, quill, etc.
thanks

I done it several times by first removing the motor and then clamping the quill in the vice...

Originally Posted by vanguard cycle

haha! yup exactly like that one!

as to why remove, its a likely bad worm drive in the head so rotating down isnt currently a one man show.
Head either needs removed or rotated to fit in the doors anyway and it can be taken apart where it sits now (buddys shop) so figured i would go ahead and completely remove both head and table to help with moving.
so how bad is this for the spindle bearings, quill, etc.
thanks

Rarely does the worm drive fail most likely the ram adapter is chipped out where the square head of the mounting studs bear against the slot from over torqueing the nuts.

Table mounted adapter is the way I personally do it, only safe way if working solo. Adding extra support via wood blocks or whatever to keep the head straight is prudent. Its not balanced relative to the spindle line and extra support reduces loads in unexpected places. Having assisted guys doing it by other methods e.g. hoists et al it still seems to me to be the best way not least because you can use the feeds to line everything up exactly to remove and refit. Hoists and other methods with flex in the line always seem to need shoving into alignment to overcome small errors. The closer I get to 60 the more I favour cunning over heaving!

Concerning the incidence of tilt worm drive deficiencies all the half dozen I've been involved with showed significant to considerable wear on the worm wheel but rather less on the worm. One set was clearly approaching unsafe so worm and wheel were renewed and the key ways re-worked to remove slack by fitting oversize keys. All the others had the worm wheels reversed to bring the unused teeth into play an a couple had the key ways reworked for oversize keys too. From choice I wouldn't take a head much past 20° from vertical without assistance or a safety strap and certainly wouldn't remove the stop pin without arranging a strap "just in case". Not even on my machine which I know to be good. With one of unknown history I'd be very unhappy about tilting until I'd had a chance to verify that all components were in good order.

Yup I'm chicken here.

Partly due to a bad experience with a similar type of set up in a different context which almost got away from me. Being an idiot I hung on and just managed to hold it. Sensible guy would let it go figuring that the firms machine was a lot less valuable than my hands!

Clive

Originally Posted by Clive603

Sensible guy would let it go figuring that the firms machine was a lot less valuable than my hands!

i completely understand Clive, no matter how many times i hurt my foot i still attempt to stop falling things from hitting the floor with them!
it's like i tell my girl when i come limping home, my foot will heal, that expensive part wont

and thanks for all the great responses guys, this bridgie is new to me so i will most likely have more questions in the coming days.
thanks again everyone