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Re: Bosch Digital Laser

#254677 by WileyCoyote » Sat Dec 08, 2018 11:40 am

As I get older and things don't work as well as they used to, especially my eyesight, I depend on gadgets like this to help me in my hobbies. I haven't used a pair of calipers in a few years that doesn't have a battery and I would never give up my Wixie gadgets. I don't see a problem with using technology to help me out and it is quite often more accurate than I can get with mechanical gadgets.

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Re: Bosch Digital Laser

#254680 by reible » Sat Dec 08, 2018 12:59 pm

I just picked up one of these bosch lasers. I will not be using it for setting up the machine but rather measuring rooms and the likes. The advertised resolution is no where near what one needs to set up a table saw.

Typically +/- 1/16" is just not going to be useful on a table saw even for measuring for parts where I would shoot for being with in 1/32". Remembering that laser could be off by as much as 1/8" from measurement to measurement. That would be one reading off by + 1/16 and the other off by - 1/16.

"Experts" that I've respected for other things and I have no reason to doubt have used from .003" to .005" as how close a table saw should be setup. I have used .005" and I have not found it difficult to get this or better using several methods. Yes there are a few tricks to achieve this but it is not that big a deal that just about anyone can do it.

Now on the other side, how bad can it get and still be safe comes into play. If it is too far off it becomes dangerous. I don't know where that point is and I really don't want to know. Things get bad at some point but why go there when you don't have to? Could you get by with it being off by 1/32" who knows but if it were a 1/16" I'd be really scared. Off by a 1/8" you might as well get out of the shop as using the saw that way would be nuts.

The point being is you should strive for something in the few thousands and you will not get that with a bosch laser.

Ed

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{Knight of the Shopsmith} [Hero's don't wear capes, they wear dog tags]

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Re: Bosch Digital Laser

#258159 by WebTraveler13 » Tue Mar 19, 2019 1:44 am

how long it could be live w/o charging?

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Re: Bosch Digital Laser

#258163 by reible » Tue Mar 19, 2019 2:09 am

WebTraveler13 wrote:how long it could be live w/o charging?


The model I have uses 2 AA batteries and I'm still on the original set so they seem to do pretty well time wise.

Ed

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{Knight of the Shopsmith} [Hero's don't wear capes, they wear dog tags]

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Re: Bosch Digital Laser

#258165 by RFGuy » Tue Mar 19, 2019 6:48 am

I just picked up the Milwaukee laser measure (for installing LED lights in my shop ceiling), but all of these units look very similar to each other. I found a good website that discusses the accuracy and resolution of these kinds of laser measuring devices. I am including a quote below because I found it useful. So, I believe the Bosch GLM42 is very similar to my Milwaukee in that it has a resolution of 1/32", but its accuracy is quoted as 1/16". However, I think this accuracy is actually linear and would be much smaller than 1/16" on the small scale of making a measurement on top of a table saw. If you look into higher end laser measuring equipment, the accuracy is typically quoted as a percentage, so it is that percentage multiplied times the distance range. Since these low end laser measure devices are typically only a single range like 150 feet, the accuracy is quoted as the total accuracy over that 150 feet. For nice easy numbers, say you are making a cut at 1.5 foot on the table saw, then your accuracy should be 100x better (1/16" divided by 100). That is quite small for accuracy on a table saw!

So, I think the accuracy of one of these units could be quite small (much less than 1/16") and I expect it to be fairly static unless the lighting or temperature fluctuates a lot in your shop. I mean the saw blades light reflectance should be fairly constant over time. If it starts to gum up, it can always be cleaned. It should be possible to make several cuts using this laser measure and use a set of calipers to measure the cut and determine what the accuracy is from this. Once this reading is known, you could simply calibrate your cuts accordingly. However, I don't think accuracy is going to be the limiting factor as it should be very small on the sort of distances measured on a table saw. Resolution is really your limiting factor for making cuts, I think. With a resolution of 1/32", this is the same as the adjustments on the Incra TS-LS fence system, but of course the Incra has a micro adjuster that goes even lower, but 1/32" should be quite acceptable resolution for a lot of saw cuts. Just my 4 cents (it was 2 cents, but I had to adjust for inflation).

https://www.acuitylaser.com/sensor-performance
"The accuracy of a sensor is a measurement of the difference that can be expected between a sensor's reading and the actual distance measured. The resolution is the smallest change in distance that a sensor can detect, and is typically a smaller value than the accuracy error. Accuracy may be affected by temperature, target reflectance or ambient light, which generally will not affect the resolution. "

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Re: Bosch Digital Laser

#258173 by sehast » Tue Mar 19, 2019 9:35 am

This seems like an easy thing to prove or disprove by just using a dial indicator to check the laser device accuracy over a short distance. I would do it but I don't have one so I encourage those who do to do so and report their findings.

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Re: Bosch Digital Laser

#258178 by RFGuy » Tue Mar 19, 2019 10:40 am

sehast wrote:This seems like an easy thing to prove or disprove by just using a dial indicator to check the laser device accuracy over a short distance. I would do it but I don't have one so I encourage those who do to do so and report their findings.

Yes, I agree. You are right, a dial indicator may be a better choice for checking the accuracy of the laser measure. I was thinking of making practice cuts at different widths so that we could look at the finished cut accuracy (using a caliper to measure cut width). This would give you the final accuracy (including sawblade runout, table movement, laser measure accuracy, etc.). I was mainly thinking about this for checking the accuracy at multiple measurement distances from the blade to see how the accuracy varies. A dial indicator is probably a better way to go. The laser measure accuracy should be linear, so once you know it at a given distance, you can compute it as a % and then apply it for any measurement length from the saw blade.

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Re: Bosch Digital Laser

#258198 by RFGuy » Tue Mar 19, 2019 10:13 pm

Sorry, just re-acquainted myself with this entire thread. Just saw that BuckeyeDennis already made the same point, so he was first and deserves the credit. I didn't mean to rehash the same point he already made on accuracy. Since I just bought a laser measure myself, this thread became interesting to me this morning so I just wanted to share what I had learned. Dusty was originally asking the question about whether one of these could be used to check saw blade runout or other uses in the shop. I guess I was more thinking about it for some kind of improvised DRO for rip cuts. This thread and the original post from Dusty is getting me thinking about how I might be able to use this thing around my shop (in other ways)...I mean once I am done with mounting all my LED lights in the ceiling. Anyway, thanks for all of the discussion here.

One last point to reiterate, as I said in my previous post, the accuracy is likely quite good on these units over the distances we are talking about, but the resolution is 1/32". So, if you wanted to use it to check alignment, etc. you could be off no more than 1/32" (resolution is not +/- like accuracy is; also assuming accuracy << resolution). If you want to consider it a +/- then the resolution of the sensor could be thought of as +/- 1/64". One of us that has one of these would have to confirm how useful or not useful one of these could be by comparing side by side with a dial indicator, but I just wanted to point out that these laser measure devices are not as bad as has been assumed in a few of the posts here.

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Re: Bosch Digital Laser

#258201 by reible » Wed Mar 20, 2019 12:36 am

The model I have might do well for some cutting applications on a shopsmith but a few things would have to be worked out.

The manual states that the center of the beam of the laser is where the measurement is taken from, for me that is really hard to see and in fact it looks more like a line then a dot but that is more then likely due to my vision. The point being one would have to find a blade tooth that is pretty small center the laser on it and it has to be the tooth that is facing the right way. For me that would be hard to do.

My laser measures from the base, and they state the minimum useful distance at 6". So a rip cut would have to be at least 6" wide to even use it. With mine there is an "error" displaced when you get less then 5-15/16". I do a lot of cuts with smaller widths then that so not sure how one would get around that.

It doesn't like reflective surfaces which could mean errors when looking at a saw blade???

Then this is this gem from the manual:

"Accuracy Check of the Distance Measurement The accuracy of the distance measurement can be checked as follows: – Select a permanent measuring section with a length of approx. 3 ft to 33 ft (1 m to 10 m); its length must be precisely known (e.g. the width of a room or a door opening). The measuring distance must be indoors; the target surface for the measurement must be smooth and reflect well. – Measure the distance 10 times after another. The deviation of the individual measurements from the mean value must not exceed ±1/8” (±3.0mm). Log the measurements, so that you can compare their accuracy at a later point of time."

I'll let you sort that out.


As far as how accurate they are I'm sure they work pretty well for the intended purposes. I mean you do use them to measure then transfer that measurement to cut the workpiece. If indeed the cut is within a 32nd of in inch that for most things that is good enough. Setting up tools is not it purpose so I have to no hope that things would work out well for that application.

If I get some time I'd like to make a set up to do some testing. A few set up blocks and a feeler gauge should tell the story pretty fast.

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{Knight of the Shopsmith} [Hero's don't wear capes, they wear dog tags]

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Re: Bosch Digital Laser

#258204 by RFGuy » Wed Mar 20, 2019 7:37 am

Ed, you make all valid points. Out of curiosity which Bosch model did you get? My eyesight used to be 20/10 which was a gift and made it easy for me to work on very small surface mount components in electronics at work. Today, presbyopia has set in and I have trouble focusing close-in. I need to get reading glasses, but have not done it yet. In addition, the past few years, I find that I have trouble reading unless I have good bright lights. My shop has poor lighting, so poor in fact that I had to use a flashlight on the other side of a square to do alignment on my Shopsmith so that I could tell when the blade was parallel with no gaps to the square. That's why I am putting in new shop lights and had to purchase the laser measure to install them. Well, I could have used the tape measure up on the ladder for like the 1000th time, but finally broke down and bought a laser measure.

You are right about the <6" measurement, so perhaps it is less useful for rip cut measurements. I have a Porter Cable miter saw, but have not built a miter station yet. Perhaps mounting it on a miter station could serve useful for making repetitive cuts there, but then a stop block could do the same thing. I did make 10 separate measurements at 8" from rip fence to saw blade to check the repeatability. I don't own a caliper yet, but I do own a Woodpecker 1281 square and I think Woodpecker's Al machining is down to 1/1000th so I assumed the height of this square to be 8" +/- 1/1000th. Using it as a guide, I clamped my rip fence and did 10 measurements. Every single one was 8" exactly on my Milwaukee laser measure. So, at least my model seems to do fine with the saw blade and repeatability, but maybe when I finish installing my new, bright lights it may struggle. Of course, I am going to the flat of the blade for the measurement. I know to be useful you would need to measure to the carbide tooth on the near side of the blade. However, if you know this width it would be easier to subtract it from the measurement, but this isn't so easy to do inside the laser measure. Another option is to try to get one of those laser targets that they have for survey work. Placing one of these on the flat of the blade could help with reflectance, but again you would have to correct for distance from this to tip of carbide tooth. Ultimately, I guess I am trying to fit a square peg into a round hole here. These devices are "cool" and just wish it could find other uses in the shop. I did follow-up on another thread (link below) a while back regarding putting a DRO on the tablesaw fence. Noone responded, so I am guessing other than Owad noone found it useful or attempted it. I don't trust my eyes like I used to, so I am just looking for any advantage that I can get in the shop to make life easier. I would have seriously considered the Incra TS LS for my Shopsmith, but they don't sell it anymore. I will probably try to improvise a DRO somehow on my 520 fence in the not too distant future. Likely my laser measure will collect dust once I am done installing the LED lights... :(

https://www.shopsmith.com/ss_forum/viewtopic.php?f=9&t=15588&p=256008&hilit=DRO#p256008

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