repairing J head low speed housing

[jmm03]

Hello all, I am probably not describing it correctly,so please bear with me. The bearing housing on the pulley that drives the quill
has two pins that ride in slots to enable the gear to be moved up when low speed (back gear) needs to be used.The threaded holes are worn out and the pins I bought from H&W don't work.I would like some repair suggestions if possible before I take the housing off.I was wondering if I could rotate the bearing housing 90 degrees and drill new holes,but I suspect it is more involved.I am not sure how worn out the housing is as to whether it is feasible to drill out the existing holes and retap the and make custom pins but I would prefer to try and fix this one if possible rather than just buy a new housing.(I know,I know...)
Thanks for any help. Jim

 

[Tony Wells]

I had that issue with my clone, and tapped larger to fit custom pins, made from dowels. Worked, but there should be a better way. The slot(s) is(are) worn on mine as well, so at some point, a rebuild is in order.

 

[jmm03]

Hi Tony, I haven't even addressed the worn slot possibility yet,the mill is serviceable but its in a welding and fabrication shop that puts it to somewhat hard use,taking it down for very long could be a problem,hence the preplanning.I replaced the bearings and belts in the top end and rebuilt the table feed gearbox,(an early straight mechanical feed).Just alot of small issues that most older tools are likely to have,coupled with some lack of knowledge on my part about jheads.I've worked more on the later vari-speeds and Laguns and Index's. Regards, Jim

 

[CharlieW]

My 1965 Bridgeport had that problem. A previous owner just rotated the bearing housing about 20 degrees and drilled and tapped new holes. I have since repaired the pins an additional time. It was an easy repair.

Charlie

 

[brucer]

at some point bridgeport accepted it was a poor design and added extra drilled and tapped holes... so you may be able to get new pins and rotate the bearing sleeve and put the new pins in... if the clutch cam or housing isnt wore too much... if the housing has too much wear to disengage the low gear housing you have to redrill the hole something like .010 lower on the bearing sleeve... they recommend assembling the tophousing and bearing sleeve and putting a .010 shim between it and the lower teeth, then marking the holes and drilling and tapping them....
also if the top housing is worn under the cam you can have a shim cut from flat stock to make up for the wear on the cam and or the housing..

the tap size for the pins are 1/4-32unef (united extra fine)

i found a modification on some guys personal website, and i wish i could remember where it was so i could give him credit.. anyhow he made a nice top plate which he drilled and tapped 8mmx1.0 and bolted on sleeves, this also took up the slack for the clutch cam.. it was a pretty innovative idea for a long standing problem with the old j-heads..

heres the pics i saved them for reference.

 

[RandyM]

This very thing happened to my machine just as I was buying it. The owner then proceded to fix it with thread inserts. Currently it appears to be working quite nicely. Time will tell if it will last.

 

[brucer]

This very thing happened to my machine just as I was buying it. The owner then proceded to fix it with thread inserts. Currently it appears to be working quite nicely. Time will tell if it will last.

the bearing sleeve wall is pretty thin where the cam pins are, seems like thread inserts would cut you short on a couple more of the threads.. the thread insert might be a little harder than the sleeve itself, so that might help.

i lucked out, after i got mine tore apart i have an extra set of holes... i ordered new bearing retainer nuts, compression springs,cam pins. i'm going to clean up the top housing and i think i'm going to order a new timing belt and drive belt while i'm in there.. plus i'm going to add about .030 on both sides of the brake lever to get me more brake...