Question on BP M type rotary head mill

[DanLins]

Do these enjoy a good reputation? Can parts be found if needed? (Like the end nuts on x & y axis feeds)

Thanks in advance.....

Dan

[Bguns]

No answer yet, so I will jump in... www.lathes.co.uk has a lot of information on Bridgeports.

M Head Bridgeports excell at light work...

The spindle is designed to run ~ 1/2 in endmills, maybe a 2 in fly cutter/Boring head...

The spindles that were available were the B3, B&S #7, and Morse Taper #2 all 1/2 inch collet capacity

They are not built for heavier work... for modelmaking and small work, they are fine.

The basic mill parts (leadscrew nuts, wipers, and such) are identical to the larger J head models (Some M heads were even built on the full size J head column) The shorter tables would require the longer table feed screws to be shortened.

The head bearings are available, the clockspring can be bought, or made from a real clock mainspring. The splined spindle drive pulley nut, is the only tricky to make wear part in the head.

The differences on older M Heads are the round ram (not as ridgid as a J head V ram, but still stiff enough for ~1/2 in tooling)

The length of the table on older M Heads is 32 in, giving a max of 20 inches of x travel.

The saddle on older machines only has 9 inches of y travel, vs 12 inches on later M/J head machines.

The M heads require a bit less space in the shop, and are a little easier to move around.

A VFD installed on the M Head, will give a lot more of a usable rpm range than just the stock belt drive alone. And provide the needed single phase conversion to 3 phase. (some M heads were single phase from factory)

3 phase allows instant reverse, which is very handy for tapping. Motors are simpler with no switch contacts to fail, or motor capacitors to explode/melt/leak...

[Rich Carlstedt]

Yes, they are excellent machines
Nuts are the same as all later models
Parts can be had from High Quality Tools at

http://hqtinc.com/

click on replacement parts and look for series 1 BP's

They have a catalog of just BP parts, and a second one for clones
I have no association with them, but friends have bought parts and were happy with service/price.

I am not sure about parts for the M head, but the basic machine is no problem
Rich

[Bguns]

Hmmm I do read previous posts... Grouchy tonight...
Quoting myself.... :

"The basic mill parts (leadscrew nuts, wipers, and such) are identical to the larger J head models (Some M heads were even built on the full size J head column) The shorter tables would require the longer table feed screws to be shortened."

Any Bridgeport Mill parts supplier will have the common parts.. (including Hardinge) Hardinge has clocksprings, lockwashers, and bearings listed for M head repair parts...

The quill feed handle will interchange with a J head.

Any other M head specific parts must be acquired from used parts suppliers...

[DanLins]

Roundhead BP

My brother tells me that this is likely an older, late 1930's model, and that getting the head back to zero after rotating it is nigh onto impossible.

http://s1013.photobucket.com/albums/af253/Danlins/Machinery/

Thanks for all the input, folks.

[TGTool]

My brother tells me that this is likely an older, late 1930's model, and that getting the head back to zero after rotating it is nigh onto impossible.

I don't know why that would be so. I've got a real old M head on an older Cincinnati horizontal overarm. You just put an indicator in the spindle where you can sweep the table, zero it on one side, swing to the other, tap the head back to half the indicator reading and re-check. Just like any other aligning and indicating task.

[Toolguy]

The main problem with the round ram mills is that you have to re tram the head every time you move the ram. A dovetail ram stays squared up when you run it back and forth.

[TGTool]

The main problem with the round ram mills is that you have to re tram the head every time you move the ram. A dovetail ram stays squared up when you run it back and forth.

True, but in practice it's not that big a problem. For most jobs the saddle travel is sufficient to cover any operation that needs to be done and the head isn't moved. I recall in the shop I worked in guys would go to some length to arrange a setup that didn't require moving the head so they didn't have to re-tram it when they were through. It's a feature (both rotation and in/out) that's there when you really, really need it and for the vast majority of jobs you don't.

[Rich Carlstedt]

My age is showing

Moving the round ram and not loosing tram was not a problem!
You stick a 1/2" dowel/shaft in the collet and tighten.
Then bring it down to the vise with aluminum in the jaws
Clamp on the dowel with the vise while moving the Y axis.
Loosen up the round ram clamps, and use the Y axis to pull the ram out.
Lock the ram and release the dowel. done !

In reality, the head is seldom moved. When it is imperative to hold a position like say 85 degrees, it is neat to do the above (With a known angle !) and keep the same angle for subsequent machining.

I changed out my M head years ago for a J because I wanted Power Boring, which I consider the single most important function of a J besides larger endmills

I doubt the mill is from the 30's . Few were made
I believe number one was 1938
My mill is number 3923 and was made in the middle of 1943.
When the War started, BP's were in very high demand
Look for the number at the front top of the knee
Rich