20th Jun 2008, 02:00 PM #1
Best way to Bevel Pipes with Grinder
I have a quick question. At TAFE i use the Oxy pipe cutter to make the 30 degree bevels on my pipes. I am practicing on the ones needed for the TIG ticket (i think 6m). I just want to know what is the best way to cut and make the bevels at home with just a grinder. I have seen it done and I just cant get the angle right, i keep stuffing it up.
I know its just my lack of experience with power tools, but is there a proven technique i can follow or is there a jig or tool i can make, to make it a lot easier.
Any advise would be great cos i want to get the practice in with proper beveled pipes not my dodgy ones.
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24th Jun 2008, 05:06 PM #3
Practice practice practice the more u learn about welding the more you 'get' the significance of preparation...........
Keep hacking away soon enough you'll become a surgeon with ur grinders n be able to prep most welds with ease
If ur prepping really thin pipe try slack belt grinding on a linisher/multitool will give quick consistant results (If u can have a play and see what works 4 U)
Regards LouJust Do The Best You Can With What You HAve At The Time
25th Jun 2008, 01:13 AM #4
I think its the same pipe im on at tafe and its a piece of 80mm nb x 5 mm x 100 and we use the same oxy cutting head setup on a lathe to cut it at the right angle to weld in either the 5g or 2g position.
25th Jun 2008, 02:35 PM #5
thanks Lou, its true its all practice, and i have realised the more you get into welding and start really worrying about detail, and trying getting it right for your test, preparation takes the majority of your time.
Caveman, yes these are the thicknesses im preparing for the final test of my ticket. (7). I saw some guy do some pipes and pulls out the grinder and did it with ease i guess i got some work to do.
27th Jun 2008, 11:00 PM #6
The prep takes as long as the weld.It is crucial that you get the landing& gap set up as near to perfect as is possible.
I taught and assessed As 1796 for 8 years and saw up to 60% failure rates ,solely due to many applicants not taking the prep seriously enough.
Also if you are fair dinkum you will purchase a copy of As 1796 and study the causes of failure.There is no 2nd chance.
No 1 failure is stray arc strikes.
No2. is lack of penetration
No3. is misalignment
No 4. tacks failing because the d---head ground the guts out of them and left them like foil paper. The rootweld then pulled the pipe edges together with a resultant lack of root fusion.
Learn them all- from the code and apply every one to every coupon that you practice on.
You should be doing 2 joints per night,so over about 12 weeks that should be 24 joints.
Also keep a notebook and record everything,what works ,what, does not
The test was usually on a Saturday,so beware that the current values may be different in daytime as the current draw is likely to be less on a weekend with no industry operating.
'If my old brain recalls something else I'll post it.
1st Jul 2008, 10:36 PM #7
Hey SWATIG. Are you using 80nb sch40? If so its going to be pretty hard to prepare with just a grinder, especially to be good enough for the No.7. Give it a go if you have to; a 125mm or 235mm grinder will be much better than a 100mm. Hold the pipe firmly somehow, in a vice, tacked to a heavy bench, whatever it takes. Have it so the pipe is vertical (as in 2g position). The height should be so you will have the grinder at just above waist height, then just move around the pipe grinding in the angle you want. Oh and you will have to make sure you have a nice square cut to start with.
Just ask the storeman really nicely if you can take some pipes to practice at home. If you look like you really want to learn and you promise to bring them back so they can reclaim them they shouldn't have any problems. Grinding in acurate bevels is a real pain and thats time you should be spending actually welding.
2nd Jul 2008, 01:23 PM #8
It took me a little bit of research but 3" SCH 40 80 NB 88.9 x 5.49
I know what you mean now, at TAFE they only call it 3" or 4" wasnt too sure, but now i know. I have a variety at home 4mm to 6mm thick at 3" to 4".
It definatly takes alot of time to prepare, now that im on holidays I need to do it at home, when schools on i can prepare them at tafe on the old oxy pipe cutter (when its clean) and take them home.
Making a straight cut is hard too, i have a 125mm grinder and getting it right is difficult.
I will try your method, i do clamp them to my table but it is little higher than waist high. I will keep trying and will get better.
Thanks for the advice.
2nd Jul 2008, 07:18 PM #9
Here's something thats come back to me .Double end your pipes-that is, preps each end , to get the maximum use of the pipe.
If you are going to prep them with the oxy acetylene beveling torch why not finish then with a flap wheel mounted on the grinder.
This will have double benefit of both smooth finish and not taking too much off in a set time .
3rd Jul 2008, 06:44 PM #10
Why are your pipes not being bevelled on a lathe, this gives consistency with exact root faces and bevel angles and leaves you to worry about the welding side of things, you must have consistency for your weld test and I doubt you are acheiving this with a grinder, pipe prep is not part of the test!
I would definetly not use a flap disc for your preps as they will leave a convex prep and round off the top edge when you grind the mill scale back away from your prep, you are using a die grinder on the inside to remove this scale also?
How are you setting your root gap?
Are you bridge tacking the pipes together?
When is the test?
3rd Jul 2008, 10:22 PM #11
I have been shown (not by the school) to set my gap by cutting a piece of filler rod (usually 2.6) and bending it into a boomarang shape. placing the first pipe in a vertical positions, the boomarang cut filler rod on top then the 2nd pipe on top of that. Then i align the pipes using my eyes and a little torch. Once im happy, i do a long tack and take out the rod. On the opposite side of the rod, i use the same piece of rod and make sure the gap is the same then a long tack. Then I choose a side and make sure the gap is ok and do another tack. Then i grind the tacks. I then start welding from the side without the tack. Now this is the theory but practical is hard. Finding a compfortable style is something im working on.
Im tossing up holding the torch like a pen or holding it with the whole hand . The old bloke im learning from says that holding it like a pen is not a good way but I find it soo much easier like that more control for me. Anyhow, my test is not for another couple of months, im not ready yet.
As for the grinding the pipes, i will keep trying but I will just prep them at school with the Oxy, theres no lathe at school. I agree that doing it by grinder is a huge waste of time.
4th Jul 2008, 01:21 PM #12
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