How Accurate Are Your T-Slots?
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- čas přidán 28. 08. 2024
- This is a response video to a viewer question from my very first video. User Ro K asked how accurate it was to use T-slot pins to locate parts on the milling machine table. The answer, in my case anyway, is not bad, but not spot on either. For most work, it will get you plenty close, but if you need it to be perfect, indicate it in. Your mileage may vary, especially if you have a machine that was not abused earlier in its life.
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One thought: the position of the pins is completely determined by the position of the slot and the irregularities at that exact point. So if there is some damage at that point, the pin and therefore the parallel will pick it up and appear to be off even though the slot is correct on the whole. The way to test this is to change the position of the pins slightly, repeat the measurement, and see how it affects the parallel. That will give you an idea of the range of accuracy you can expect when using the pin alignment technique.
Interesting video. This is one of the things I have thought of in the past, but my limited knowledge had me assuming they would be more true than that over a 6" span. It would be really interesting to see what this would look like when done on a brand new mill.
Some now obsolete mill construction kits used to require the builder to mill the T slots after installing the blank table. Guaranteed initial alignment! BobUK.
Good answer to a good question.
Obviously, when high accuracy is required, tramming of the holding system is performed, but the accuracy given by the T-slot pins is good enough for most milling operations. If you really need more accuracy, you're probably moving into grinding territory, anyway.
Good stuff, just subbed to your channel.
Thanks for sharing,
Cheers
Very interesting video.Thank you
Good enough for the girls I got out with!
Could there have been some play in the gibs? I was wondering if the run out would be the same if you went back towards your vise or if it would have been the .001 that you initially saw.
That's a possibility too. I'll test it and let you know.
I love your videos. Very informative.
I have a question for you about coolant and oil. I see a lot of people brushing cutting oil on the part when drilling holes, threading, turning, etc. I use spray cutting fluid for general purpose, water soluble cutting fluid for my saw. I recently purchased a horizontal mill and a big drill press both with coolant pumps and dark oil in the sumps. Do you have any thoughts on what type of oil I should use. The only cutting oil I am familiar with is the ridgid thread cutting oil.
Thank you again for sharing your knowledge.
Bob
Hi Robert. I use Tap Magic pretty often and also the dark cutting oil. I like them because you can use them in moderation and get good results. They do tend to smoke and stink up the place though. Machines that use dark cutting oil aren't pumping very fast, so it won’t sling all over the place. Coolant does lubricate a bit, but is mainly to cool the part/tool and evacuate the chips, so they generally pump at higher volumes. That can get messy without some kind of containment. There are a lot of saw specific coolants that are formulated to get as much life out of the blade as possible. There are also specific formulas for mist coolant, grinding, and even for certain materials. Coolant can be a breeding ground for certain bacteria that turn it skunky, so it's a lot higher maintenance.
The burr and build up at the bottom of the t slot is on almost all mills. Comes of easy by running a file up and down the lengths.
Yeah. You can see where I had to do that on some parts. When I initially bought the machine I actually couldn't run T-nuts all the way through the slots. The middle slot is still a little iffy.
How tight do the pins fit. What diameter do they mic to.
The pins are quite tight as mentioned in the video. I'd say a light press fit, although that is hard to judge since they are only contacting on two spots. The pins are made from 5/8" turned ground and polished rod and measure in at .6247"