Bridgeport Series1 J2 head drawbar

[TorontoBuilder]

Our bridgeport mill's drawbar seems to be tighter that it should be, and I looked at it in detail and to my eye it does not look original.

I wanted to make another drawbar to fit the metric arbour that our expensive sandvik face mill is attached to, and I didn't want to rely on the dimensions of the existing drawbar

So can anyone confirm how the drawbar is supposed to be made and the dimensions?

Lengths
Overall 23"
Bar 18"
Hex 4 3/4"

Thread Size 7/16"-20 for the Metric M10 x 1.0
Length 1 1/2"

It appears that the hex is drilled to insert the bar and then it appears to be fixed in place with a roll pin. Is this the manufacturer's method of construction? Or would Bridgeport have turned down an entire hex bar?

 

[Darren]

you could make a 7/16 to m10 f-m adapter, then a spacer for the top to take up the difference. The adapter could stay in the arbor, even loctited in.

 

[Former Member]

It is common for the hex head to pinned on.

 

[TorontoBuilder]

you could make a 7/16 to m10 f-m adapter, then a spacer for the top to take up the difference. The adapter could stay in the arbor, even loctited in.

Thank you. That sounds easy and would require so much less material. I can see how that would work in a manner similar to an adjustable drawbar with the upper spacer.

 

[Canadium]

I have a Bridgeport series 1 1J head with what appears to be an original drawbar.(it has a patent # on it). I suppose dimensions somewhat differ on your 2J head

Lengths
Overall 20-5/8"
Bar 16 3/4"
Hex 1.5"

Thread Size 7/16"-20
Length 1 3/4"

There is about 3/4" long round flange half 0.5 dia rest 7/8 dia. between the rod and the hex

 

[TorontoBuilder]

Turns out I didn't need a metric drawbar.

The arbour screw was filled with crud and had rusted a bit which is why the drawbar wont not screw into it.

When I cleaned is up with metric tap the tap was too loose to be right. So I shot the hole full of penetrating oil and ran the 7/16 tap in slowly and carefully. It got stuck once but I freed it. Then I was more careful to advance only about an 1/8th of a turn at a time and then back it our two full turns. Even after it was opened up I could see pitting left on some parts of the thread deeper in the bore.

So I didn't make a drawbar today.