Fine tuning your BT3K saw

[cgallery]

I've outlined my procedure for aligning my BT3K SMT and rip fence to +/- .001" (one-thousandth of an inch). More details here:

http://www.cgallery.com/jpthien/index.htm

Please let me know if you spot any obvious mistakes or if anything seems unclear.

Thanks!
Phil

[jhart]

Pretty nice write up Phil. Nice pictures also. Thanks for sharing.

[rcp612]

Great instructions!! The easiest I've seen. Thanks Phil

[LCHIEN]

I've outlined my procedure for aligning my BT3K SMT and rip fence to +/- .001" (one-thousandth of an inch). More details here:

http://www.cgallery.com/jpthien/index.htm

Please let me know if you spot any obvious mistakes or if anything seems unclear.

Thanks!
Phil

That's very good, Phil!

[dlminehart]

Looks really great. Thanks, Phil! Only thing that's a bit unclear to me is the attachment of the gauge to the wood. You mention the holes, but I could use a closeup of how the gauge actually attaches. I notice, for instance, that it is not horizontal . . . how does it stay at that particular angle?

[cgallery]

Looks really great. Thanks, Phil! Only thing that's a bit unclear to me is the attachment of the gauge to the wood. You mention the holes, but I could use a closeup of how the gauge actually attaches. I notice, for instance, that it is not horizontal . . . how does it stay at that particular angle?

My indicator has a lug back. This provides a point to screw it to a fixture. In my case, I used a cross-dowel and bolt (knock-down furniture hardware) to hold my indicator to the jig. This allows me to use a single cross-dowel to hold the indicator on either the long edge or short edge of the jig. All I have to do when I want to reconfigure the jig is turn the cross-dowel by 90-degrees with my fingernail and screw the indicator on from the other edge.

The angle you see the indicator set to was simply an attempt by me to have the indicator tip as close to the table as possible. This allows me to take measurements at a wider point on the blade, thus increasing accuracy.

[final_t]

My indicator has a lug back. This provides a point to screw it to a fixture. In my case, I used a cross-dowel and bolt (knock-down furniture hardware) to hold my indicator to the jig. This allows me to use a single cross-dowel to hold the indicator on either the long edge or short edge of the jig. All I have to do when I want to reconfigure the jig is turn the cross-dowel by 90-degrees with my fingernail and screw the indicator on from the other edge.

Totally. Brilliant. Finally a really good use for the dial gauge!

[Turaj]

Thanks Phil for taking the time. The instructions are clear and very helpful! Thanks again!!

[LCHIEN]

...

The angle you see the indicator set to was simply an attempt by me to have the indicator tip as close to the table as possible. This allows me to take measurements at a wider point on the blade, thus increasing accuracy.

Not a criticism really, but the dial gauge at an angle other than a right angle to the blade of course gives you a less than accurate reading. Since the object in this case is to get the same reading or a difference of zero or at least minimize it then it really doesn't matter.

If the dial gauge is not perfectly normal (perpendicular) to the blade then the actual reading will be longer by about the sine of the angle from 90°. You're really measuring the hypotenuse and not the shortest distance.

If its 5 degrees off then your reading will be 9% longer than the actual distance.

I think about things like that, just a measurement science (metrology) thing with me...

[ChrisD]

Very good write-up, Phil! I'm all for inexpensive methods that yield excellent results.

[ChrisD]

I think about things like that, just a measurement science (metrology) thing with me...

And that, Loring, is why you are such an asset to this place!

[cgallery]

Not a criticism really, but the dial gauge at an angle other than a right angle to the blade of course gives you a less than accurate reading. Since the object in this case is to get the same reading or a difference of zero or at least minimize it then it really doesn't matter.

If the dial gauge is not perfectly normal (perpendicular) to the blade then the actual reading will be longer by about the sine of the angle from 90°. You're really measuring the hypotenuse and not the shortest distance.

If its 5 degrees off then your reading will be 9% longer than the actual distance.

I think about things like that, just a measurement science (metrology) thing with me...

Right, I thought about that and I knew you would, too. :-)

Not being a metrologist, I had to think about it a while. I finally decided that, when making relative measurements, the angle is a PLUS. Because it effectively increases the resolution of the indicator. That is provided: (1) You can maintain the angle very strictly (hasn't been a problem), and (2) You don't use such a steep angle that it causes the indicator stem to deflect or work in a non-linear fashion.

So using the angle is a win-win: (1) You use more of the blade, thus greater accuracy and (2) You get an increase in resolution of your test gear, thus greater accuracy.

Am I right? Do I get my junior metrologist badge?

[LCHIEN]

Right, I thought about that and I knew you would, too. :-)

Not being a metrologist, I had to think about it a while. I finally decided that, when making relative measurements, the angle is a PLUS. Because it effectively increases the resolution of the indicator. That is provided: (1) You can maintain the angle very strictly (hasn't been a problem), and (2) You don't use such a steep angle that it causes the indicator stem to deflect or work in a non-linear fashion.

So using the angle is a win-win: (1) You use more of the blade, thus greater accuracy and (2) You get an increase in resolution of your test gear, thus greater accuracy.

Am I right? Do I get my junior metrologist badge?

I'll agree with you as long as you don't tell me any uncorrected numbers you read off the gauge face! (which you did iw two "minor" places - calculation of the runout and distortion of the blade of .006" when you raided it to the top. I figure the last one was probably more like .0055" instead of .006"

My real point is not criticism of the procedure, I think its quite good and will do the job. I just don't like to see dial gauges at an an angle other than perpendicular. Makes me shudder. Other applications it may really matter!

[cgallery]

I'll agree with you as long as you don't tell me any uncorrected numbers you read off the gauge face! (which you did iw two "minor" places - calculation of the runout and distortion of the blade of .006" when you raided it to the top. I figure the last one was probably more like .0055" instead of .006"

My real point is not criticism of the procedure, I think its quite good and will do the job. I just don't like to see dial gauges at an an angle other than perpendicular. Makes me shudder. Other applications it may really matter!

No, your criticism is valid and I didn't even think that I was measuring runout w/ the indicator at an angle! I will update the page w/ a corrected photo and add some discussion of using angles in the notes next time I make changes.

If there is anything else you see please don't hesitate to say something. And that includes any text that isn't clear or could be made MORE clear.

[greencat]

Great write up - I also like you shop vac collector. How much is the angle reader?