Machining pipe bevel

Hello I have no experience in machining I'm hoping y'all can get me started. I want to bevel pipe to practice tig welding on. It will be 2 inch sch 40 and sch 80. I have no tools yet. I'm looking to get the 7 in. x 10 in. Precision Benchtop Mini Lathe from harbor freight it runs around 560 but will be less with the 20 percent off coupons. Could y'all please tell me what tools I will need to buy to be able to bevel a 37.5 degree bevel and what the steps would be. There isn't much videos online.


Mini Lathe - 7" x 1" Precision Mini Lathe

Harbor freight also sells lots of different lathe tools but no idea how to use them or if I'll need all of them. Any help would be greatly appreciated


Lathe tools

This is the link to all the tools harbor freight has for lathes mostly on bottom of first page and the rest on the second page

While the TOS prohibits discussion of so-called "hobby machines" I submit we allow this one instance. The OP is working to improve his welding competency and desires a small lathe to weld prep his practice material.

Most any small lathe will do the job you propose and much more in the same size range and smaller. You can get by with a parting tool and a hand-ground turning tool like this

HSS lathe tool sketch - Google Search

The South Bend basic lathe manual "How to Run a Lathe" is a valuable resource for a beginner lathe hand. Here is a PDF:

http://vintagemachinery.org/pubs/1617/3789.pdf

Eventually, depending on the equipment furnished with your new lathe, you will need some additional items. Make a list as you go, think about where and when you shop, set a budget etc, strike up acquaintanceship with old machinists who may have a soft spot for mentoring etc. OIW build a support structure.

Forgive my asking, but isn't it a little extravagant to buy a lathe for the sole purpose of prepping weld specimens? You got other plans? A weld shop with a machining capability or a machine shop with a welding capability will probably do 4 times the business of a one-trick pony shop.

Good luck to you.

I suggest we DO NOT allow this "Just once"....there have been too many "Just Once" allowances
around here.

What I do suggest is the OP find a retired machinist to have their TIG practice pieces made locally,
and maybe even receiving some one-on-one instruction on lathe work.

Well this thread will be locked soon, but before it is, let me suggest to forget about doing this on a lathe. It's an expensive and unnecessary way to do this.

Just buy a benchtop belt sander and spin the pipe in your hand while pressing the other end against the belt, Something like this, although a more powerful one would be much better for metal: http://www.sears.com/craftsman-3-4-...yA&gclsrc=ds&dclid=CJqJhPTU1tUCFa-8swodfG0JMA

A bench grinder would be even better. That sander will probably stall if you press the workinto it hard enough.

Practice welds don't require precision bevels, which is what a lathe is capable of (at least agood one, not the cheapo models you mentioned). Buying a lathe will require tooling and accessories that will cost more than the lathe and a long learning curve. In fact, a bench grinder is one of the accessories you will need anyways.

Just buy a bench grinder and learn to spin the pipe to get an even bevel. You can also use it to sharpen your TIG electrodes (keep a wheel reserved for just this).

The pipe can be beveled with a 14" double cut bastard file in less time than it takes to even think about getting any machine to do it with - at substantially less cost - and zero aluminum oxide contamination for the TIG to not like

johnoder said:

The pipe can be beveled with a 14" double cut bastard file in less time than it takes to even think about getting any machine to do it with - at substantially less cost - and zero aluminum oxide contamination for the TIG to not like

Click to expand...

Goos point john, hadn't thought of contamination.

Buy yourself a good 4 1/2" angle grinder (which you should have for welding anyway) and learn how to grind the bevels.

Wall thickness of 2'' sch 40 is .154", sch 80 is .218", so it will not take long to grind a bevel.

Fabworks said:

Buy yourself a good 4 1/2" angle grinder (which you should have for welding anyway) and learn how to grind the bevels.

Wall thickness of 2'' sch 40 is .154", sch 80 is .218", so it will not take long to grind a bevel.

Click to expand...

Especially when you factor out the 0.0625" root land.

I assume you're practicing for API-1104 or ASME Sec. VII/IX?

If you were closer, I'd do this for a case of beer. A106 cuts pretty nice, IME.

If the sole purpose of the lathe is to make practice coupons... I'd
skip the lathe (at least for now).

Find yourself a small shop, or a retired home shop guy (home shop machinist board?)
And let them go to town on it for a few bucks. Make sure you have the pipe in hand.

Several reasons to go the "sub it out" route.. Cheaper than buying a lathe (for now)
and you get to make some contacts. Might even luck out and be able to trade some
welding work for some machining work..

Also, I'm assuming the goal is to become an employed welder.. In that case any contacts
you make trying to get coupons made could become very helpful in the future..

If you were closer I'd trade you out some work..

johnoder said:

The pipe can be beveled with a 14" double cut bastard file in less time than it takes to even think about getting any machine to do it with - at substantially less cost - and zero aluminum oxide contamination for the TIG to not like

Click to expand...

But will you be able to reliably produce a 37.5-degree bevel? I'm sure you realize that welding 37.5-deg. bevels is entirely different from welding 38.2-degree ones.

MichaelP said:

But will you be able to reliably produce a 37.5-degree bevel? I'm sure you realize that welding 37.5-deg. bevels is entirely different from welding 38.2-degree ones.

Click to expand...

Yes, indeed: Some welding has to meet stringent requirements and the weld prep is only part of the picture.

Not all welding process is served by farm country technique. I've cut weld preps in omega seals, pipe, plate etc where the contour was not only gaged but held to 0.005 tolerance and 1/4 degree.

I was skeptical of these elaborate requirements until I quizzed the welding instructors and the worker bees. They told me that consistent weld prep was the key to consistent results where full X-ray quality was an everyday requirement, particularly in awkward locations where a mirror (even two!) was needed to see around obstacles to weld. Pressure looks for the weakest point. The weld on the far side of the pipe has to be every bit as good as the weld you can easily see.

I've never done welding to that degree of fussiness but I've known plenty of guys that have. There's welding over dirt and paint and there's super quality aerospace and nuclear welding and everything in between. Good enough for patching a boat trailer may not be good enough for welding burner cans in a jet engine. You work to requirements keeping in mind that your habitual technique does not constitute the apotheosis of welding quality.

The weld school sent its student weld sample to the machine shop for sectioning and prep for pull and bend tests. When I worked inspection on the "other shops QA" bench, I got a first hand look at the results. The back bead appearance looked like the finest TIG welding which, of course, it was. That controlled burn through with back purge ensured the inside of the pipe was 100% fused, free of defects, and presented a minimum smooth convexity conducive to flow, etc. Ever heard of consumable inserts, back-up bars, run out tabs, piggy back starts? Welding is a sophisticated trade the equal in technical knowledge and diversity of any other trade. I got a lot of respect for a fully qualified welder.

Keep an open mind, next time you fly. The landing gear your butt depends on probably has welds whose requirements you may think a waste of time.

If someone says he needs fully machined weld preps for practice, give him the benefit of the doubt. He's the guy with the cert qual papers in front of him. He may know what he needs better than you.

Thank you all for the reply may take to a machine shop for now. Til I save a little more money

Forrest Addy said:

Forgive my asking, but isn't it a little extravagant to buy a lathe for the sole purpose of prepping weld specimens?

Click to expand...

Forrest Addy said:

Not all welding process is served by farm country technique. I've cut weld preps in omega seals, pipe, plate etc where the contour was not only gaged but held to 0.005 tolerance and 1/4 degree....

If someone says he needs fully machined weld preps for practice, give him the benefit of the doubt.

Click to expand...

Forrest,

I fully agree with you. All the advises to use files, angle grinders, sanders and grinders are not applicable if the OP is an experienced welder and needs to refine his skills to be employed by a nuclear facility, Boeing or a NASA plant. I don't know if a Harbor Freight lathe rhymes well with those, but it definitely much more predictable than files, grinders, etc. in terms of a correct beveling.

Yet if we imagine the volume and total cost of outsourcing test coupon machining for such an extensive and serious training (unless it's a prep for a particular project), purchasing an inexpensive dedicated lathe doesn't sound too extravagant at all. Especially, if it's an HF toy which begs to be a dedicated tool for such basic operations as anchoring a boat, keeping doors open or, well, beveling test coupons.

P.S. I hope that the flat coupons welding training is over, so there will be no need to buy a milling machine.

MichaelP said:

But will you be able to reliably produce a 37.5-degree bevel?

Click to expand...

If you've learnt how to file you will.

Limy Sami said:

If you've learnt how to file you will.

Click to expand...

I'm afraid I'll need to have a degree in Finance and Economy to calculate how much time it will take to produce such a coupon: 2" steel pipe, 37.5-deg. bevel while keeping the cut perpendicular (or at a particular degree) to the pipe axis and maintaining a consistent root land size.

But I suspect that a person who can do it within a reasonable amount of time doesn't need to change his occupation and become a welder. With all probability, he can make a decent living "as is". Especially, considering how many coupons are needed for those who want to advance their welding skills without buying dedicated Harbor Freight lathes and mills.

True, ...... but we weren't talking the financial aspect of filing

Of course you can buy all kinds of weld coupons. Just do a search for weld coupons.

That lathe that the OP wants will struggle with any steel over 1" diam, and will need a lot of tuning and tweaking just to do that. Don't ask how I know. Save up your money for something much better.

If you want to do it yourself, buy a rotary welding positioner and an angle grinder. The welding positioner will be useful later, and the angle grinder, with quality wheels, will be faster than the lathe.

Get some 1/4 plate, find a bit of bar or tube that fits loosely inside the pipe to be prepped, mitre it to the complimentary angle you require and weld to the plate sticking up, when you prep the stub or nipple when you hold the angle grinder horizontal the pipe should stick up at the right angle of the bevel.
Cut your practice peices, drop one on the spigot sticking up, the spigot should be slightly lower than the bit of tube your bevelling.
Bring the grinder to it holding the grinder horizontal or close.
With the grinder running gently touch the tube, it will start biting and spinning the stub of tube itself.
Repeat til bored.
Don't use the same disk for stainless, you'll drive iron onto the pipe.
It what I was taught to do and I must have done hundreds of 2" bits of tube
Don't forget to degrease.
Watch welding tips and tricks, walking the cup etc.
( furic Pyrex are really good, and you can see through them, I like gas lenses)
I'm currently relearning stainless, is suprising how quick you forget stuff!
I do the odd hour when I can fit it in, mainly because I bought a new AC/DC set and it's got more settings than I can list
Mark