70's bridgeport with an M head, opinions?

frezaRO · May 26, 2020

Hello everyone, always wanted to join this board and now I have a legitimate reason. I just purchased a 1973 Bridgeport with an M head. I am a metal fabricator and welder and I have been hoping to learn how to use a mill and lathe to expand my metalworking capabilities. The chance came to purchase a bridgeport so I jumped on it immediately. I had no chance to do my research beforehand, unfortunately, so as I am reading about my machine now I am learning this might not have been the best purchase! I have very little knowledge about these machines and I have used a knee mill only a handful of times (a Cheng Ki 1-1/2hp). What do you guys think about this machine? Is it possible to buy a J head and mount it on this machine if I want something heavier duty with auto-feed?

$2,000 for the machine in good condition.
Serial on the Knee "12 BR 157759"
Serial on the Head "M26493"
Motor 1/2 HP

Thank you for your time.
(not sure if this is the best way to attach pics)

Rob F. · May 26, 2020

Pics look good, you did better than most and got them to show up

You realize the power feed in the head is NOT for drilling right? It is for boring holes to a specific size that are already drilled. It is not for powerfeeding drill bits like a drill press can.
Where are you in Calif?

chip's · May 26, 2020

Looks like a dovetail ram to me. You should be able to find a J head to fit the knuckle.

frezaRO · May 26, 2020

Rob F. said:
Pics look good, you did better than most and got them to show up
You realize the power feed in the head is NOT for drilling right? It is for boring holes to a specific size that are already drilled. It is not for powerfeeding drill bits like a drill press can.
Where are you in Calif?

See this is the info I knew this forum would have. "What is the M-head ideally made for" should have been my main question.

No I did not realize it is for boring holes, How is it for tapping threads in already drilled holes?

I have an upcoming project where I need to bore .120 holes to .145 and afterwards tap a thread all in .120 thick mild steel. Is this M head good for that?

I am in the Sacramento area.

jhruska · May 27, 2020

If you are good with a hand drill that would be a lot faster.

Form tap or cut tap? Two different tap-drill sizes.

Use the mill;
Bore out to 0.145. No, just get on location and drill it, then tap before moving to the next hole.

The adapter that fits the M-head now might not match up to the j-head.

Just me but I think you paid too much. For a $2000 M-head there should have been digital read-outs
or at least a Servo-feed for the x-axis.
John

Milland · May 27, 2020

Rob F. said:
Pics look good, you did better than most and got them to show up
You realize the power feed in the head is NOT for drilling right? It is for boring holes to a specific size that are already drilled. It is not for powerfeeding drill bits like a drill press can.
Where are you in Calif?

He knows the M head doesn't have power feed, he's referring to the J head that he'd like to swap having power feed.

Milland · May 27, 2020

Freza, the M head has a lot of limitations, so if you can swing the extra cost going to a J head would be a good idea. But this time it would help to run some options by a knowable friend (or even here) so you don't wind up with a further let down.

Now, the M head is great for being a very nice drill press head, so you might find a sturdy drill press and try to adapt the M to it. Use your new J head mill to make the adapters you'll need...

BTW, check out the spindle bearing on the M, they're pretty darn old now and it might be wise to think of replacing them if they've not been oiled as needed. This guy did a pretty nice job of videoing a series on refurbishment: M Head Matters 1 - YouTube

frezaRO · May 27, 2020

Wow, well thank you all for the information. I at all do not feel bad about this purchase, it might be at the higher end but it comes at a time in my life when I am setting up my own work studio/shop so to kick things off I have a new mill and welding table. Can't wait to move in and set up.

I plan to eventually buy a J-head and swap it on there. If the M head can at-least be used as a drill press for now I am very satisfied. And this machine is in real good condition. The ways are clean and from what I understand from the seller, it saw very little use.

How much does a J-head go for? I can't seem to find a lone head on ebay.

PDW · May 27, 2020

frezaRO said:
Wow, well thank you all for the information. I at all do not feel bad about this purchase, it might be at the higher end but it comes at a time in my life when I am setting up my own work studio/shop so to kick things off I have a new mill and welding table. Can't wait to move in and set up.

I plan to eventually buy a J-head and swap it on there. If the M head can at-least be used as a drill press for now I am very satisfied. And this machine is in real good condition. The ways are clean and from what I understand from the seller, it saw very little use.

How much does a J-head go for? I can't seem to find a lone head on ebay.

I quite like the M heads, I have one. But they do have limitations.

If you want to run cutters from say 2mm up to 12mm (or 1/2" for you primitives) then IMO the M head is better - it has a much higher speed range.

If you want power feed on the quill and ability to run a decent face cutter, the J head is better.

I have both. I did exactly what you want to do and am seriously thinking of reverting. HOWEVER I have other 40 taper mills and I regard the B/port as a bit of a flimsy general purpose mill anyway, not something for serious metal removal.

The last J head I bought cost me $300, the one before that was $600. Local to you, who knows.

PDW

HWElecRepair · May 27, 2020

frezaRO said:
The ways are clean and from what I understand from the seller, it saw very little use.

Not arguing it, but I can count on one hand the amount of times a seller didnt say it saw little use and had great ways

If you can get a J head for a good price and the ways are in the condition the seller said, all around you won out I think. I am with JHruska that there probably should have been some extras for the cost, but I dont think you got raked over the coals. Without seeing the ways, knowing how much rock or slop is in the axes, it is difficult to say.

Jon

HWElecRepair · May 27, 2020

PDW said:
I
The last J head I bought cost me $300, the one before that was $600. Local to you, who knows.

I need to make friends with your friends.

Those are steals.

Jon

Tony Quiring · May 27, 2020

Check in with emerick in Fresno.

Good source for esed stuff, once had a 2 hp mill for arts for 700.00...

Sent from my SAMSUNG-SM-G930A using Tapatalk

jim rozen · May 27, 2020

Suggest a step pulley J head as the replacement, not a varispeed. Then fit a VFD.

Use the M head until a good one shows up.

frezaRO · May 27, 2020

HWElecRepair said:
Not arguing it, but I can count on one hand the amount of times a seller didnt say it saw little use and had great ways

If you can get a J head for a good price and the ways are in the condition the seller said, all around you won out I think. I am with JHruska that there probably should have been some extras for the cost, but I dont think you got raked over the coals. Without seeing the ways, knowing how much rock or slop is in the axes, it is difficult to say.

Jon

I know what you mean, it's like when someone sells a car and they say "runs like new" "freeway miles only"

Attached are pictures of the ways and table (excuse my lack of correct terminology)

I have a feeling this machine originally came with a J head and someone adapted an M head onto it. Is it possible to put the M head on the rear and a J head over the table? Make a drill press/mill combo?

Also, I realize now there is a forum specifically for bridgeports on this site. Hope this doesn't give the mods any issues.

jhruska · May 27, 2020

Details about the M-head
There is an adapter to mount the M-head on the back of the ram. It is similar to the mount for the shaper.
If the proper adapters can be found a J or 2J head can be mounted at the front of the ram and the M-head at the rear.

John

jhruska · May 27, 2020

Details about the J and 2J dimensions.

John

PDW · May 27, 2020

HWElecRepair said:
I need to make friends with your friends. Those are steals.

Jon

One was a dealer I knew well - he bought it one day & sold it to me the next at a decent profit without having to do anything to it. His attitude was, a decent profit for zero work and a fast money turnover beat holding out for top dollar and waiting maybe 2 years to sell something.

The other, cheaper one was an auction. I did get lucky there.

And yes you can have the M head on one end and the J head on the other end. I used to do this myself until I wanted to tuck the mill into a tighter corner and the extra head got in the way. I fabricated my J head mount from a steel weldment.

PDW

Milland · May 27, 2020

Looking at pic 5 from the OP - that looks like a somewhat worn chromed way. Does anyone have an opinion on how worn? I'd guess it's fine, but my machines are not chromed so I don't have a good reference.

frezaRO · May 27, 2020

Well thank you all so much for your input and knowledge. The machine was bought and paid for upon starting the thread and I am happy to have my own mill as I am expanding to my own shop.

Within the next few weeks I hope to be fully moved in and have this machine set up and milling whatever project needs it at the moment. I wont invest any more money at this moment, for now I just need to learn how to properly use this thing and go from there.

I will be getting the tooling and collets from the owner later on in the week, I will update with more pics.

Rob F. · May 28, 2020

Milland said:
He knows the M head doesn't have power feed, he's referring to the J head that he'd like to swap having power feed.

Yes, I was talking about the power feed that he wanted the J head for was not meant for drilling. Since he is a fab guy, kind of like me, I wanted to point out that a J head was not a power feed drill press substitute.

70's bridgeport with an M head, opinions?

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