# Aaaggghhh!!!!!!!!!!!!!!!!!



## ranch23 (Oct 15, 2012)

I was tramming in my mill and snapped off a bolt in the face of the head housing. I had to walk away  but think I have to pull the entire head to replace it. Must be Monday.


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## Hawkeye (Oct 15, 2012)

What mill do you have? Someone on here may know how they're put together.

It could be a stud - drilling and using a good easy-out might solve it. I'm assuming there was a nut on the outer end, rather than a bolt head.


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## ranch23 (Oct 15, 2012)

Its a square headed bolt in backwards, nut on the face of the mill, Im sure the head is in a recess trapped by the housing and I believe I will have to pull the entire head loose, or completely off. Its an Acra mill.


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## Pacer (Oct 15, 2012)

Sounds like its one of the 4 that are loosed to allow the head to rotate?? If so, yes you will have to pull the head. As you said it should be a square head bolt, not a stud, that rides in a circle T slot.... bummer!!


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## ranch23 (Oct 16, 2012)

Yes, and yes im kicking myself, altho' I wasn't hanging off of it.


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## bvd1940 (Oct 16, 2012)

When you replace that bolt get a GOOD quality or make and replace all of them ifin they be chicom bolts:thinking:
Just my 2cents worth )


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## ranch23 (Oct 16, 2012)

Good thinking, will do that very thing.


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## Pacer (Oct 16, 2012)

A little story here around those T bolts ---

Couple years ago I bought a Bridgeport type mill (Induma) for $500 without being able to do any thing except determine it was pretty sad. Hauled it home without needing to tilt the head, but on arriving home I needed to then tilt the head to get it into the shop -- well, guess what, it wouldnt tilt! After much scratching of the head??? what the??? took the head off and whoa! someone had pulled 3 of the 4 T bolts thru the Tslot and then had the brilliant idea to replace them with studs (would make for a difficult tramming of the head, no?) 

For some 2-3 months I was figuring it was only good for parting out, but between my buddy and I we figured out a repair and it turned out OK. Have since found out its not too uncommon for this to happen when a heavy hand is used...

I guess the moral of the story is to keep this in mind when tightening these down..hew:

I have a few pics of this, Ill start another post and show it...


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## ranch23 (Oct 16, 2012)

Please do, and I have been at this since 1986, you would think that that could never happen to  me (us).


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## dickr (Oct 16, 2012)

I would bet that Acra is a Taiwan machine and a pretty nice one. Same as many others from there. I think that is a fairly common problem as I recall seeing that in shops I worked in. (more than a few) They just tightened it down and kept goin. Like it was earlier mention grade 5 or 8 would be a good idea for the bolts. Mistakes are done to learn from so now you're even smarter !!!
Be careful removing the head     that can be an owee
dickr


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## ranch23 (Oct 16, 2012)

You bet, removing the head can be fraught with peril. And yes the Acra is a nice machine, have Acra, Bridgeport and Wells. I would take a new Acra over almost any used machine.


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## ranch23 (Oct 16, 2012)

http://youtu.be/HFE_nXQCH6E, hey, if this link  works, check this out, the job just got way easier!


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## OldMachinist (Oct 17, 2012)

Like was stated above stay away from the cheap asian made bolts. The original Bridgeport bolts were alloy steel with cold formed heads and rolled threads, the cheap ones are turned from square stock and will break if torqued just a little over the 50 ft lbs specified. The manual says"Tighten the four unit head mounting bolts first to 25 lb-ft in a diagonal sequence then to 50lb-ft.".

In the picture the bolt on the right is a OEM Bridgeport and other is asian.


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## ranch23 (Oct 17, 2012)

Thanks for the info. I'm assuming torque specs and the like are available in the Bridgeport rebuild manual?


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## OldMachinist (Oct 17, 2012)

The specs are in the full Bridgeport manual that you can download from Hardinge here http://hardingeus.com/usr/pdf/Knee Mills/SeriesIPartList4302Plus.pdf


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## ranch23 (Oct 17, 2012)

Got it, Thank You!


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## ranch23 (Oct 20, 2012)

Replaced the bolts in my head today. Will take longer to tell about it than it took to do it. Built that head holding fixture, and raised the table, puting the fixture in the collett, used the table  to pull the head loose, replaced the bolts and we are back to tramming.


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