Problem- Whats missing? Drive lugs

[Jet A]

Hello,


I recently acquired a bridgeport series 1 j-head with an NMTB-30 spindle. I know nothing about bridgeports, and i am begining to get my feet wet. The spindle has an electric impact draw bar. I reciveved a ton of nmtb-30 and erikson Quick Change 30. All of them seem to fit fine in the machine. Here is the problem, The tool holders have female lugs, and the spindle has female lugs. Knowing what i know about Tapers, there has to be some sort of drive lugs. Can anyone tell me what i am missing?

[vidio1]

The spindle would normally have "male" lugs attached where the slots are. They were most likely removed when the powered drawbar was added. Just a quess, but for the lugs to work with an ATC there needs to be some way to index the tool holder to the spindle. A more simple solution is to just remove the lugs.

[mactec54]

Hi Jet A

Yes you should have the drive key in there I have a set you can PM me

[machintek]

Depending upon the drawbar set up, there has been difficulty lining up the keys to the tool when pressing the button to hold the tool. Some power draw bar kits used extended keys to get around this. Try holding the tool inside the spindle and see the gap between the tool and where the keys will sit. It might answer the question why the keys were removed.

George

[Jet A]

Originally Posted by machintek Depending upon the drawbar set up, there has been difficulty lining up the keys to the tool when pressing the button to hold the tool. Some power draw bar kits used extended keys to get around this. Try holding the tool inside the spindle and see the gap between the tool and where the keys will sit. It might answer the question why the keys were removed. George

AH HA.....I see what you are saying. I went and measured. there is 1/2" gap between the top of the tool holder flange and the bottom of the spindle flange. this is before it is taken up by the draw bar.

So knowing this, does the taper take all of the load then? are there any custom tapered keys for this? it seems like there is a pretty big load on the taper. Are they designed for this?

I will not be running a ATC, but will be running the power drawbar.

mactec54, let me see what my options are first, if i need the lugs i will PM you for sure.

[HimyKabibble]

The taper alone is MORE than capable of handling the torque on a Series 1. The keys are only required when you get up to at least the 5-10 HP range.

Regards,
Ray L.

[Jet A]

Good to know


Thank you

[mactec54]

HimyKabibble here we go again giving out bad imformation

Jet A you need the keys, as George said, some draw bar kits had/needed longer keys, the standard key in your case will not work

The size of the key you need .402/.406 wide .625 long & .750 high you can taper the top .250 as the standard key is ony .500 high, These are easy to make if you can't get any

One of the reasons you need the key or keys, is these are prone to the threads getting tight, (chips dirt etc in the threads ) & you won't be able to hold the tool with your hand when it has a tight thread, this is were the keys will hold the tool untill it is undone.

[HimyKabibble]

Originally Posted by mactec54 HimyKabibble here we go again giving out bad imformation Jet A you need the keys, as George said, some draw bar kits had/needed longer keys, the standard key in your case will not work The size of the key you need .402/.406 wide .625 long & .750 high you can taper the top .250 as the standard key is ony .500 high, These are easy to make if you can't get any One of the reasons you need the key or keys, is these are prone to the threads getting tight, (chips dirt etc in the threads ) & you won't be able to hold the tool with your hand when it has a tight thread, this is were the keys will hold the tool untill it is undone.

Yeah, sure.... That's why ISO30, which is the *exact* same taper, does not even *have* notches, or drive dogs. And how many Bridgeports have worked just fine for years, or even decades, after the stupid little alignment screw was sheared off?

Like I said, the taper itself is MORE than capable of holding the tool until youi get well above the horsepower of an old BP. If sticky threads on the drawbar are a problem, then you really ought to clean them more often so they're not sticky.

Regards,
Ray L.

[seniormachinist]

If it were me, holding a cutting tool in my hand and energizing a power drawbar, I'd want the keys engaged to prevent the tool spinning out of my hand. That's just me though.

[gridley51]

Originally Posted by mactec54 HimyKabibble here we go again giving out bad imformation Jet A you need the keys,

Matchmaker have thousands of 40 taper machines running with no drive dogs,so I don`t see that it is bad information.
As for holders getting tight on threads,it`s more than likely a problem with your drawbar.

[mactec54]

That is one of the main problems with air wrenches spinning at 200 to 1000rpm if the draw bar grabs the thread & you don't have the keys you have the tool spinning in your hand, this then becomes a SAFTEY problem ( Ocha saftey violation )

HimyKabibble it is obviously you have no clue as to what we are talking about on this subject, there is a big difference between the 2 types of draw bars systems

One is spinning & the other is not with the drawbar you are talking about not needing keys it does not spin, you have a air cylinder on top of the draw bar just pushing it down to release the tool , springs for pulling the drawbar back up to lock the tool in place, Keys are not needed if you are not doing any heavy cuts with this system

But with a impact wrench on top of your draw bar it can be spinning the draw bar any were from 200 to 1000 rpm, You can guess what happens without the keys when the thread grabs the tool & it spins in your hand