How to become more accurate?

[STIBuilder]

I wanted to share my own struggles and see if other had similar thoughts. Basically im interested in ways other fabricators became more accurate in building stuff. The right tool I know goes a long way but there also has to be some processes and obviously skill to become better. I'll give an example building a stand for my 2x72 grinder, its 1.5 square tube. 45* miter cuts OD is 28x15 rectangle. But after cutting everything out, the best I could get was 15 1/16 x 28 1/8 Right out of the band saw. I seem to have trouble measuring 45 degree cuts. In the past I have setup a jig and used my disk sander to bring things down to size but that was risky keeping the angles and fit nice and tight.

Thoughts?

 

[cvairwerks]

+/- 1/16” with a bandsaw is within reason. For better accuracy, make sure you are using good measuring devices, and marking tools as well as techniques. We regularly used to get within .030” and tighter limits on the factory floor using good tools and techniques.

Look up and watch some videos on old school layout work with Dykem and scribes and scales.

Additionally, use good blades in your saw at proper tension and take your time fitting things up prior to tacking.

 

[Walkers]

Get yourself an aluminum speed square. This allows you to measure end point to end point for the miters, flip it on the side, and mark for the angle. Use it also to set up your bandsaw for accurate cuts.
Usually when cutting for miters on the bandsaw I will put my blade right in the center of the mark rather than cutting to the right or left of it. My blade is.035”, so this gives me approximately 1/64” per side, or 1/32” total play in the joint set up to adjust for accurate corners. Then I will either use a corner clamp, or clamp themto my welding table and use a framing square to get the corners accurate, then measure diagonals to make sure the whole thing is accurate. For me, 1/16”” is a maximum allowable error, but I try to shoot for right on the mark!

 

[RoninB4]

Speed square is a good suggestion to have for lots of projects. So is the idea of accurate lay-out and scribing lines. A black sharpie can often work just fine for lay-out and scribed lines instead of Dykem. Accuracy is a relative word. Accuracy for house framing isn't the same as for finish carpentry. The same holds true for metalworking. Working to .001 is absurd for the stand you made for your grinder. Working to .001 often isn't good enough for precision metalworking. I have a jig borer that will locate to .xxxxx on the DRO but it would be overkill to use that for a welded frame component.

What was the condition of your saw blade? How square to the blade was the saw vise? Small errors in accuracy can add up to larger errors. I have to check this every time I make a critical cut on my band saw too. You can't expect good results from a machine or operation that has built-in inaccuracy. If it's a critical cut, ensure everything is aligned and where it should be. Sometimes inherent errors need to be corrected by a secondary operation or a different machine. That's just the nature of things. If I don't have a machine that's capable of producing the results I want then I either have to send it out or change the design to work with what I don't have.

It's all about how precise/accurate you really need to be for any given project. Excess precision/accuracy is time and money wasted when it's not needed. Also bear in mind that for most operations the time spent in set-up is far greater than the time actually cutting metal. Not uncommon to use an hour setting a piece in a machine only to spend 10 minutes of cutting time. There are also limits to what a machine operation can do. Boring a cylinder on a drill press will not produce satisfactory results and a belt sander is not a substitute for a surface grinder. That doesn't mean you have to buy expensive machinery to produce good results for projects.

Buy a few things to help with accurate set-up, take your time with this, and use good sharp cutting tools. You can even ask for suggestions on this board BEFORE you cut anything. There's plenty of knowledgeable members in the collective here. Do allow yourself to make mistakes and have less than desirable results, it takes time and experience to make nice things.

Sorry this was long winded, accuracy is a deep rabbit hole. Enter at your own expectations. Good luck.

 

[STIBuilder]

Great points so far, I think the biggest take away so far is that in the quest for accuracy you may need a second operation. So like @RoninB4 suggested. Personally I do have a speed square and use it for the 45's Im also just getting used to the bandsaw and the cuts it makes, huge upgrade from my Evolution cold saw.

 

[ItsNemo]

You'll never cut better than a 16th or maybe 32nd on any saw. I fully expect to do some final fit-up with a grinder/file/sander when doing metal work by erring a smidge long on the cut or by bridging it with weld by erring on a smidge short.

 

[LXCam]

Well you didn’t say what kind of bandsaw but I’m thinking hand held? If so layout your cut path with dikem and a scribe and don’t try to cut more then two sides simultaneously. If it’s a drop down bandsaw do some practice cuts and see which direction it’s out and try to shim or adjust for it. The other key to a drop down is blade tension and slow down the feed, allow it to cut without forcing the cut. If the feed is to fast it’ll twist the blade just enough it’ll start to wander on you.

Past that, a two part prep isn’t the end of the world, just time consuming.

And since we're talking metal and dependent on gauge you can always undercut your joint and leave a small gap so placement is dead on and weld away. However when doing it in that fashion you need to figure out a method or change your welding tactics to compensate for shrinkage and the piece moving on you too.

 

[LeonardY]

Accuracy is really dependent on what you're building.
What you need to understand is tolerances that are needed.

Framing carpentry requires less accuracy than finish carpentry.
Finish less than furniture.

I would buy a good framing square, speed square and a combination square.
Get to know your equipment. Test cuts on them until you understand the limitations of the machine.

 

[Bigblue&Goldie]

When I was in school for manual machining one of our graded elements was how accurately we could cut a piece of stock to length on the horizontal bandsaw. I forget the spec, but I want to say it was about .030". Not difficult, but definitely not quick. We also had a drill press project where we had to layout, center punch, and drill numerous types of holes. That project was also graded on how precise your hole locations were. The key to all of it was the quality of your layout.

As others have said, Dykem and a carbide scribe are the way to go for precision. If you don't have Dykem, get a Sharpie and draw a fat line and then scribe into it with your scribe. The other factor is how square your equipment is. I have a portaband in a SWAG base and there's nothing square about it, so I have to factor that in. Good squares, protractors, and scales are money well spent when trying to hit accurate marks. For me, it comes down to patience. There are days when everything goes to **** because I'm in a rush and let things slide. Those are the days you've got to hang it up and go get a beer.

 

[zeke/]

spent forty years as a pattermaker where dead on was the accepted dimensions whether it was 4'x8'x 40' or 11' diameter x 11' high.
Takes good tools, time and patience. Close enough will never get you good work.

 

[isb cornbinder]

spent forty years as a pattermaker where dead on was the accepted dimensions whether it was 4'x8'x 40' or 11' diameter x 11' high.
Takes good tools, time and patience. Close enough will never get you good work.

I graduated from trade school in the mid 1960s. While there was lots to learn in trade school, the real learning came as hands-on in the shop or job-site. A SPEED SQUARE may have been my most used tool. Accuracy is an attitude and learned. If a person does not have a passion for what they are doing, step aside and move on.

 

[e015475]

The Dykem and scribe suggestion did the most for my accuracy when fabing with metal, but here's a few other ideas

- Buy some HF digital calipers and use them to scribe the Dykem when you're doing a layout, I keep a good Mitutoyo caliper around, but abuse the HF ones
- An optical center punch is a great way to improve the accuracy of your drilled holes.
- Buy a few metal yardsticks
- A speed square is my go-to, but some smaller machinists squares along with some large carpenter squares come in handy
- A divider wing compass with scribe points is great for laying out larger circles and radii
- A $25 digital level box is amazingly useful
- I keep a 1' and a 6" belt sander near the band saw - do the rough cut on the band saw and sneak up on the scribe line with the belt sander

 

[cvairwerks]

I cringe when I see people using measuring calipers as scribing tools. Same thing when they use the end of a scale as the reference point when trying for precision in the under .030” range...

 

[ItsNemo]

I cringe when I see people using measuring calipers as scribing tools. Same thing when they use the end of a scale as the reference point when trying for precision in the under .030” range...

Many calipers have carbide tips specifically for scribing. Example:

Mitutoyo

www.mitutoyo.com

 

[cvairwerks]

Many calipers have carbide tips specifically for scribing. Example:

And few outside the layout world know of them or are willing to drop the $300+ on them, as they have no clue or care about how it damages the ones not designed for the task.

I’ve seen how measurement tools are often handled in our plant and just shake my head at how badly they get abused at times. Then the shop people wonder why things are off or tools don’t ever come back from calibration.

 

[Jlarson]

To be honest when I'm doing general fab cutting I only measure and rough mark pieces just to organize my cuts if I have a lot of them, I pull a tape right off the blade.

 

[STIBuilder]

Well you didn’t say what kind of bandsaw but I’m thinking hand held? If so layout your cut path with dikem and a scribe and don’t try to cut more then two sides simultaneously. If it’s a drop down bandsaw do some practice cuts and see which direction it’s out and try to shim or adjust for it. The other key to a drop down is blade tension and slow down the feed, allow it to cut without forcing the cut. If the feed is to fast it’ll twist the blade just enough it’ll start to wander on you.

Past that, a two part prep isn’t the end of the world, just time consuming.

And since we're talking metal and dependent on gauge you can always undercut your joint and leave a small gap so placement is dead on and weld away. However when doing it in that fashion you need to figure out a method or change your welding tactics to compensate for shrinkage and the piece moving on you too.

Jet 7x12 horizontal, great idea about under cutting parts! These are all great suggestions for others to follow.

 

[LXCam]

Jet 7x12 horizontal, great idea about under cutting parts! These are all great suggestions for others to follow.

I can tell you from experience that both my original 7X12 and the 9X16 that replaced it that cranking down hard on the clamp for an angle other then a 90 will move the fixed clamp. Oh its not much, but it doesn't take much to tweak the angle enough to make life difficult. I bought the 9X16 new and its never been abused but when I'm cutting angles with it and clamping the piece, its just snug enough not to move and I slow down my feed rate.

 

[BukitCase]

On both my 4x6 and 8x12 saws I not only scribed a line on the base for zero (making sure that the pivot bolt was slightly loose, then holding the fixed jaw against the bolt (pushing from the material area), then I added another stop on the movable end and hard clamped it to the saw bed. This helps 90* cuts stay good, if I don't get TOO carried away with clamp pressure -

I do quite a bit of stuff with square tube, and I HATE bugs of all kinds getting into available holes, so (depending on how strong things need to be) I either cap any open ends (1/8 x 1-3/4 FB works well for insert caps) - or I cut 45's -

As mentioned, it gets tricky/slow to get 45's to end up EXACTLY as planned, so several years ago I posted the adapter shown below - I made two, one for the small saw and one for the larger one. I made one change on the larger one that works REALLY well - I left the 45* side long enough so that once it was situated and locked down in the saw, I could let the SAW cut that end IN PLACE -

That pretty much gives me an EXACT point to set my SECOND cutoff scribe line (so the POINTS of 2 45's are EXACTLY the length I need.

For anything I build that needs maximum strength I use 45's - this not only provides a built-in CAP, it also lengthens the weld by 1.414 TIMES, Obviously that part can't work for a T joint.

Another thing that really helps strengh of a weldment (if you need all you can get) is to cut things a little bit SHORT, then insert small spacers before clamping together - done right, this will give you a FULL PENETRATION weld (any pipe fitters know what I mean) - for tubing between 1-3 inches, I tend to use small pieces of "mechanics wire" for spacers - for MIG you'd want to SLIGHTLY push a little faster to avoid burn thru (DAMHIKT )

The pic that shows the large tube frame is one of three 8'x12' roof frame modules for half of the 24' square container roof I did (NEVER enough covered space in rainy Oregon) - that was done on NON-level gravel using jack stands, shims, 2 Wixey angle cubes (MUCH prefer their tip-up version), a LOT of walk-around checks, copious quantities of clamps - and the diagonal brace was actually one of the "purlins", kept TIGHTLY CLAMPED at ALL crossings until all welding was done (with MUCH "hopscotching" til every joint had 3-4 tacks -

I clamped pieces of scrap to the undersides of tubes at all joints, main purpose to maintain exact alignment at each joint. One verification that things were straight was to close one eye, squat down til I could just barely see the far side of the assembly, then move ONLY MY EYE from side to side to tell if there was any TWIST -

All pieces were gang cut on the larger saw so all were less than about 1/64" different. This also let me set up my mag drill table to place bolt holes from the SHORT ends of tubes, instead of individually measuring 11 feet along the tubes - I have the mag drill table done so I can insert a 2" tube into a piece of receiver tube, insert a smaller one in the other end of the receiver and CLAMP it for a repeatable stop.

Doing that allowed me to bolt the 3 8'x12' roof modules together WITHOUT having to hog out any holes (I used a21/32" annular cutter, so a TINY bit of cheating :=)

The end result of all this OCD stuff - all 3 roof modules came out with diagonals less than 1/64" different, ZERO twist, and using a few other "cheaters" I assembled the 24' square roof entirely ALONE.

Because I built the roof "modular", when I no longer need it THERE I can unbolt sections and move the entire thing wherever I need it (once the $$$ is available for a 3 bay tall garage)

Some pics (go back and re-read for better understanding if necessary) ... Steve

 

[BukitCase]

Wasn't sure how many pics would be allowed, here's a few more - note the "crabwalk" hand truck mod, those modules weigh around 300# each -

 

[BukitCase]

Guess the answer is "10" -
first one here shows the modules temporarily offset to allow grinding the inner welds so modules fit (while STILL allowing modules to later be unbolted/separated -
Next - "terrain adaptable" outer roof legs (for if/when the whole thing gets moved) - adjust holes on 1" centers, 1" acme "fine adjust" on bottom. Acme's trapped to C channel, nut welded inside tube.

It's good to have a few choices of wheels without having to change 'em all the time - there's also a power strip on the cart, so ONE extension cord does it :=)

Each one of those "adjustalegs" took about 20 minutes to drill ALL the holes :=)

Anything that wasn't clear, please feel free to ask... Steve

 

[ArkTinkerer]

One item I didn't see mentioned is absolute vs relative accuracy. Often I don't need an absolute accuracy but I do need parts the same length. Stacking and cutting in pairs or setting up stop blocks on the saw will make sure that the pieces match. Thinking in these terms can often make a project faster.

 

[BukitCase]

Yup, I did mention gang cutting above, as well as depth stops for drilling holes in the same place on multiple pieces - I've done as many as 8 pieces at once on the 8x12 saw - for fairly long groups, a couple weld clamps a foot or two from one end of a bundle (assuming you ate your wheaties first) and you can cut both ends without having to do anything but swap ends.

All these little tricks/observances can add up to better work in less time for sure... Steve

 

[zmotorsports]

I would echo what others have stated about accuracy being a state of mind and knowing not only your own capabilities but also knowing your tools/equipment.

My equipment itself is quite accurate but I have seen people produce just as accurate work with far less accurate machines. Even back when I had my round column mill which was not known for holding tight tolerances, I could routinely hold tight tolerances because I knew the potential problem areas of that machine and I knew how to hold the work for better than average results.

On my current equipment I know how close I need to cut to a line to ensure enough material for proper clean-up without wasting material. I also try to cut as close as possible whether it is for a very accurate project or a "general" project where accuracy is not as critical.

I was working on one such project last night so I thought I'd snap some pictures to demonstrate my take on it.

Layout was done with nothing more than a pocket rule and a small combination square, blue Sharpie marker to coat the part and a scribe.


I know my vertical bandsaw well enough that I know cutting to the outside of a scribed line will net me approx. .025"-.030" for clean-up.


This cut landed me at .027" for clean-up.


Depending on the project, I may walk over to the disc sander if it is something non-critical and get within a few thousandths of target size. However, I wanted to be more exact with this so over to the mill it went for clean-up. Generally my saw will cut straight enough that it only needs .010" or so per cut side for complete clean-up.


After milling each side I landed exactly at my target of 2"


Just wanted to give my perspective on accuracy and how it can be achieved with little waste and not much effort.

Aim small, miss small.

 

[theoldwizard1]

Cut long, grind to finish dimensions, doing multiple dry fits.

The Fireball Tools squares are worth the money. Accurate, well made, and you can really clamp your pieces well while welding. Because of this, gas can be filled.

 

[BukitCase]

"Because of this, gas can be filled."

HuH??!? ... Steve

 

[Bodj Built]

"Because of this, gas can be filled."

HuH??!? ... Steve

Gaps can be filled*

 

[BukitCase]

Thanks, semi-senior moment there - I only tried letter REPLACEMENT, not ADDITION ... Steve

 

[Monza Harry]

Thanks, semi-senior moment there - I only tried letter REPLACEMENT, not ADDITION ... Steve

Steve, You could have gotten away with "DAMN AUTOCORRECT" and I would have believed it as it gets me all the time! Harry

 

[BukitCase]

Thanks Harry; but I try to "own" my mistakes, seems to help me NOT do it that way again (SOME times ) ... Steve

NOT saying I have't been bitten by autocorrect tho, it's why I tend to proof read before posting, more so if it's a fairly technical subject - I still remember the old example of bad grammer from high school (only 60 years ago) - "throw the horse over the fence - some hay" - hell, I wasn't strong enough BACK THEN to throw a horse over a fence

 

[ArkTinkerer]

Yup, I did mention gang cutting above, as well as depth stops for drilling holes in the same place on multiple pieces - I've done as many as 8 pieces at once on the 8x12 saw - for fairly long groups, a couple weld clamps a foot or two from one end of a bundle (assuming you ate your wheaties first) and you can cut both ends without having to do anything but swap ends.

All these little tricks/observances can add up to better work in less time for sure... Steve

Apologies! Missed the "gang cut" reference!

 

[BukitCase]

No prob, there's been quite a bit of info posted already on this relatively new thread, easy to miss a comment here and there ... Steve

 

[Milton Shaw]

One thing is making sure the workpiece doesn't move in the vises. Put some self stick abrasive paper on the faces of the vises to make sure workpiece does not slip. As others have said use a scribe instead of a soap stone will make a lot of difference

 

[isb cornbinder]

One thing is making sure the workpiece doesn't move in the vises. Put some self stick abrasive paper on the faces of the vises to make sure workpiece does not slip. As others have said use a scribe instead of a soap stone will make a lot of difference

I agree 100% with the scribe. I am not impressed with the You Tube "experts" who use a Sharpie for their cut lines. How can a person suggest they might have some level of accuracy if that person does not have a transfer punch or some method of accurately locating the center of a hole?
I like to use a sharp scribe or a thin marking knife for accuracy. I like sharpies and I have them in every colour and width. Something I like to do is to very lightly take the sharp point off of a freshly sharpened scribe. The tiny flat end will leave a clear mark.

 

[gte718p]

I agree 100% with the scribe. I am not impressed with the You Tube "experts" who use a Sharpie for their cut lines. How can a person suggest they might have some level of accuracy if that person does not have a transfer punch or some method of accurately locating the center of a hole?
I like to use a sharp scribe or a thin marking knife for accuracy. I like sharpies and I have them in every colour and width. Something I like to do is to very lightly take the sharp point off of a freshly sharpened scribe. The tiny flat end will leave a clear mark.

This goes back to knowing what you are building and the appropriate tolerances. My speed square was almost a 16th out of square. I built 40 houses with it and never noticed. Trying to setup my bandsaw it was driving me nuts.

I used to do a lot of tube work on race cars and off-road vehicles. Almost all of the tube work was laid out with sharpie. However when it was time to build jigs for locating suspension or building suspension components the dykem scribes.

Some people have a precision fetish. That is fine and can be a mark of a master craftsman. However, a professional will match the tools and techniques to the requirements. A sharpie and a tape measure can be the right tools for the job.

 

[sanddan]

I typically work on my precision skills just because. I do this stuff because I like to so trying to hit the number dead nuts on is part of the fun. This started when I got my lathe and mill and began to learn machining. It has also made me much better at welding and fabrication. Accuracy is a benefit in just about everything you do.

 

[Milton Shaw]

The one use of a sharpie would be to use it like bluing (Dykem) to get the surface where you can see a scribe mark easier. A sharpie is a lot faster than finding the Dykem bottle and not as much mess as spilling the liquid blueing.

 

[joe49]

My speed square was almost a 16th out of square.

I'm thinking you had a knock off and not a real Speed Square. The real ones I have are accurate.

 

[matt_i]

Even if you don't have machine tools you can do pretty well with a collection of good files to work on "fitting".

 

[bugnut]

As others have posted depends on what you are doing. To get measurements correct all the time use the same tape measure for that level of accuracy.

In wood the tool to sneak up on accuracy is a shooting board, trim till you get the fit.

For more accuracy in other materials with less movement, a good 24" steel ruler, from a name manufacturer, ie Starrett. A sharpie chisel point marker, makes wide black lines for layout.
For hole location and highly accurate locations, of starting and end points, an optical bomb sight is what to use and for layout prior to the bomb sight a snapoff razor knife is much more accurate than a scribe. A good quality combination squarehead with a 24" steel ruler is hard to beat.

for those not familiar with a bombsite, https://www.ucc-udb.com/C41-C44udb.PDF