Dividing head question

I am in the market for a dividing head for my J-head. I want to set it up with a gear train for helical milling. I have been surfing ebay but none of the dividing heads have any gears. What do I need to look for so I dont end up with something that wont do what I want.
Thanks
Alex

Those import clones of Walter dividing heads (sold down in GA) come with gears, studs, & banjos.
They also come in sizes from about 6" swing on up.
I've asked on here in the past if they were any good, but there does not seem to be any PM experience yet.

smt

You want to look for a "universal" dividing head, not a semi-universal dividing head. It will have a shaft parallel to the spindle to which a drive shaft from a gear box may be attached. The gear box mounts on the end of the mill table and is driven from the table feed screw. They were normal attachments on universal horizontal milling machines. Setting one up on a Bridgeport is unusual, but I did see it done once on a TV show. I think the mill owner was making spiral fluted stairway posts for a This Old House restoration job. Since you have to make the gear box or substitute (Bridgeport never made them), you can design whatever you please. Roller chain is one option, for instance.

Watch out for the sellers who call their heads universal when they have no input drive shaft.

Larry

Setting one up on a Bridgeport is unusual, but I did see it done once on a TV show. I think the mill owner was making spiral fluted stairway posts for a This Old House restoration job.

Click to expand...

Must have worked, but sounds slow & inefficient compared to a wood shaper or pin router.

smt

Various info in MHB for LEADS will have to be revised. 4 TPI table screw makes master lead 10" with the usual 40:1 head.

Your BP (with 5 TPI) will reduce the master lead to 8"

johnoder said:

Various info in MHB for LEADS will have to be revised. 4 TPI table screw makes master lead 10" with the usual 40:1 head.

Your BP (with 5 TPI) will reduce the master lead to 8"

Click to expand...

Nice catch! I have a note written in my MHB to multiply the required lead by 5/4 to get the corresponding lead to look for in the tables (and hence the change gears) for my Misal universal horizontal mill, also with 5 tpi screws.

One other point to note: setting up these gear trains is a royal PITA. Probably one will need to construct a special endplate to replace the anchor plate on one end of the table. This plate is something you might have to modify as to you go, mainly to add stud holes for extra gears required to make the gears in the train reach one another, and also perhaps for an extra gear in case you need to reverse the direction (quite likely). Fun, fun. Lots of head scratching involved that I never realized just from reading about the general procedure.

There was some other trick...it's been quite a while, but I think the gist of it was to set the cutter up on the horizontal arbor, get it centered with respect to the blank before swiveling the universal table, because it's damn hard to center the cutter and blank afterwards. Now when doing this on the vertical head of a Bridgeport, I'm not sure how you'd go about this, because the swivel axis is not in line with the work axis.

Edit 5 choices for Helical milling on a non universal mill.

Use a ball (or custom ground to needed profile) end mill...

Tilt head, mill from side of work.

Mount a table on top of table, to get table angle needed.

Use a spindle/quill mounted angle attachment, rotated to needed angle.

Turn turret of mill to get angle..

Then you can start to worry about geartrain to DH..

http://www.practicalmachinist.com/v...ng-head-set-up-bridgeport-179653/#post1956756

I see quite a few posts about setting up universal milling machines to make helical gears etc. Even if guys have the mill and dividing head, they usually are missing the change gears. I feel kind of bad because I have the whole setup for my cincinnati mill that I dont even use. I really dont want to sell it though just in case I might need it. I will say though that once you have a gear hobber, you will never want to cut a helical gear on a milling machine again. here is a little video of my old barber colman #12 cutting a helical gear.

https://www.youtube.com/watch?v=d3fFn2LsS0s

I have done this before and actually will do it again if I can find any eff'ing time. The parts went with a mill I sold and quite accidentally. I forgot to remove them before letting it leave. I was stubborn ( and am not saying that has changed ) and did not want to remove one of the handles, so made a new end support that allowed for the drive gear to remain installed. The support had a slot in the top for the gear to protrude through, and a removable cover to keep it from grabbing rags when not in use. Was a royal PITA to make and get right and kicked myself for a very long time for letting it leave. By the time I realized my error, the phone number was no longer a working one. I cannot say that I would recommend most people do this. It is largely a waste of time and effort, but I like things to be "just so" and "because I can" so I expended the effort.