Old Rockwell 10 tablesaw- trunion bolt sheered off in table

[Caleb Crosby]

yes indeed Bill, I actually googled cast iron tear out with grade 8 bolt earlier today and your right at what I found- 5/8. just for the sake of discussion my 'lazy route' shortening a new stud would give me about 1/2" engagement which for a table saw I suspect would be plenty close enough. This Rockwell contractor saw is not very heavy but 2x4's are a good idea. Did I mention the bolt that sheered off was a grade 5. I'm impressed Rockwell used good fasteners - but not good enough!

[Tom Trees]

I had that happen recently, so I drilled a hole, and smushed in a cheapo flathead, i.e one from the very cheapest screwdrivers sets you could buy from the poundshop,
likely ground it a bit, and it worked with no hassle atall.
I was expecting it to be much more difficult, didn't even have to remove the table.
That might be required if you cant get the clearance for the drill.

Saying that, I had been tightening and loosening the bolt prior quite a bit.
SAM_8221.jpg

Now, if I could only find a nice imperial bolt to replace it with, fat chance of getting anything local.
This lousy bed or couch fixing will have to do for now, and is why I keep onto everything.
I'd probably find it upsetting, if I could see it.
SAM_8228.jpg

Tom

[Jerry Bruette]

yes indeed Bill, I actually googled cast iron tear out with grade 8 bolt earlier today and your right at what I found- 5/8. just for the sake of discussion my 'lazy route' shortening a new stud would give me about 1/2" engagement which for a table saw I suspect would be plenty close enough. This Rockwell contractor saw is not very heavy but 2x4's are a good idea. Did I mention the bolt that sheered off was a grade 5. I'm impressed Rockwell used good fasteners - but not good enough!

Why do you feel that you need grade 8 bolts? It's not like there'll be a lot of pressure on the table top. Can you even reach the torque spec for a grade 8 in the cast iron top without pulling the threads out of the hole? It's not that Rockwell didn't use "good enough" fasteners but that they used adequate fasteners without spending for unneeded expenses. I bet you could hold that table down with ungraded bolts. And if you're worried about vibration squirt some blue locktite on the threads

[John Kananis]

Not much to add a the solutions provided should work. Just wanted to say, hey, that was my very first table saw. And yeah, the fence was frustrating.

The only other thing I'll add, is look into a pals kit to keep your blade aligned to everything properly. GL.

[Caleb Crosby]

Thanks John I'll google that Pals kit. I've used cabinet saws a bit and I know how nice the fences run, but I guess ignorance is bliss I have not used this yet just setting it up - but I really like the lock down and the smoothness - it is 1/32 out of true- the far end kicks in hair But if it stays consistent I can fix it or shim it

[Bill Dufour]

Where is OP located that he can not find an imperial bolt? You might just drill it out and tap to m8 or m10. If you can find a 5/16 set screw...heat it red hot and let it air cool. That should draw the temper so it can be drilled and used as a guide bushing.
If you use a screw extractor use the square non tapered kind. the tapered kind will expand it tighter and make it harder to get out.
Bill D

[Bill Dufour]

For the drill guide bushing a piece of hardwood dowel will work well enough to get a centered hole started. Do you have a lathe or drill press. No lathe? drill the hole first and use a screw and nut as a mandrel to grip in the chuck as you spin it and sand the outer diameter to fit.
Bill D

[Richard Coers]

One full thread is not easy to pull out in fact bolts are specially designed so the first thread does not carry 100% of the load. From Fastenal:

"This is designed to yield the nut threads to ensure the load is notcarried solely by the first thread. As the thread yields, the load isfurther distributed to the next five threads. Even with the loaddistribution, the first engaged thread still takes the majority ofthe load. In a typical 7/8-9 Grade 8 nut, the first engagedthread carries 34% of the load."

Other calculations for different applications can place the first thread up around 90%. But heck I wasn't trying to argue, more like confess my lazy thoughts. I am no engineer, I work with machining and enjoy reading and researching all kinds of crazy stuff. It's surprising info about threads - it surprised me . Three threads is used by some old engineers as a rule of thumb for max holding power - but depth (more threads) are still needed for accumulated stresses like vibration over time.

I just think its good to know this stuff bc it's counter intuitive and it helps you make decisions. Thanks again for the green light on lifting the table off. I didn't know.

https://www.fastenal.com/content/fed...s%20Design.pdf

The part you are forgetting in the equation is the tensile strength of the material. Grey iron tensile strength is quite low. In metric, the ultimate tensile strength of cast iron is 1.3-1.6 tonnes per sq meter, mild steel is 5.5-11.0.

[John Kananis]

The pals kit will fix the misalignment.

https://www.ptreeusa.com/tablesaw_PALS.html

Thanks John I'll google that Pals kit. I've used cabinet saws a bit and I know how nice the fences run, but I guess ignorance is bliss I have not used this yet just setting it up - but I really like the lock down and the smoothness - it is 1/32 out of true- the far end kicks in hair But if it stays consistent I can fix it or shim it

[Caleb Crosby]

Bill, I'm OP but it was someone else looking for that - Mcmaster Carr I'd recco or amazon if no hardware stores around

[Caleb Crosby]

Bill all good approaches - I agree square are the kind of extractor to use - I used to have to extract glued Sony camera screws as a sideline biz and ground my own from HSS 1/4" blanks, get em good and sharp and tap em in before turning sometimes

[Caleb Crosby]

Jerry yes 2 x the diameter in CI with a grade 8 and the bolt will fail first- depending on the grade of the casting. I dont know how age effects CI but I think it gets harder - weird thing is when you drill it out after you get thru the shell (woodpecker hard) its all powder in there!

I want grade 8 bc it will clamp into the threads with more hold before deflecting which I think is more of a problem than failure. and bc I may have to only go in half way with the stuck shaft. Ive decided my first approach is put a 5/8 length bolt in the sheered whole. I'm not trying to make a project here. Just want a tight table. I do have a lathe but cant for the life of me figure out why anyone would use on on this

[Caleb Crosby]

Bill do I have a LATHE!? I have my grandfathers 120 yr old Seneca Falls 9" with a quick change post and all the tooling. He was an MIT engineer and only used it for delicate stuff at home so it's like brand new, can cut to a thou easily. I made a lot of camera parts with it, love the thing. Still driven by the leather belt it "came with" - my father had it on a shelf at his shop for 50 years untouched- too small for any production work

[Caleb Crosby]

I sorta got it - it was a fistfight in a phone booth - got the blade running within 1/100 of miter slot. I picked up one shortie 3/4" long 5/16 bolt for my bum socket and three 1 inch. The shortie hit the jackpot - it fit- so no need to lift the top. Generally with these saws three of the trunnion/table bolts are straight forward easy access but one (Murphy) is right corner, near you facing saw and it's just a smoking crater to get to- up against the wall directly above the tilt control rod- and why in heck are they left hand threaded anyway? Thats some deep baseball there.

Thanks - that PALS look like the thing. I didn't know this was a sort of pervasive/design issue. or maybe they help you keep it in trim bc they are prone to wander? Hope not. if it does I know now where it needs some persuasion to sit straight and I'll add a doo dinger special - bolt a socket to the left rear leg and one to the motor mount rod and connect with some nuts and threaded rod.

Or something like that - thanks for the help and good ideas lads. All this messing around makes the beer go down like a babbling brook!

[Caleb Crosby]

Why do you feel that you need grade 8 bolts? It's not like there'll be a lot of pressure on the table top. Can you even reach the torque spec for a grade 8 in the cast iron top without pulling the threads out of the hole? It's not that Rockwell didn't use "good enough" fasteners but that they used adequate fasteners without spending for unneeded expenses. I bet you could hold that table down with ungraded bolts. And if you're worried about vibration squirt some blue locktite on the threads

I would think Rockwell engineers made good decisions, but all companies have to build to a price as well. I removed 3 grade 5 bolts - prob original - if so- there you go. Seems like the right bolt. But it was a grade 5 that sheered off. the 4th bolt was (probably replaced by a prev owner) - it had no grade marks, the threads were severely deformed (on all 4) but it held up.