pic: Team 3647 West Coast Drive

[JamesCH95]

Originally Posted by JesseK

McMaster # 9056K11 (or similar from a less expensive supplier) might be a good start for Richard's design.

Without a DRO, how would one check the bored diameter? Is the only way to start/stop the lathe constantly?

Even with a DRO one would stop the late occasionally, i.e. after several passes, to check the ID of the part. Without a DRO one does the same procedure. The drive handles on the lathe will have a scale on them, something like 0.100" per revolution, typically with 0.001" accuracy. The operator would then count.

I like to take a 'skin' cut, measure the ID I just machined, subtract from the ID want to reach, and count turns/notches on the drive handles.

Edit: Chris' suggestion is also a good one. Assuming you're going to make many holes that size it is definitely worth investing in a reamer.

[AdamHeard]

Originally Posted by JesseK

McMaster # 9056K11 (or similar from a less expensive supplier) might be a good start for Richard's design.

Without a DRO, how would one check the bored diameter? Is the only way to start/stop the lathe constantly?

No need for a DRO. A DRO won't make the machine more accurate, just a bit easier to use.

Boring part by part is possible, but an FRC team who plans to start making custom parts should purchase the specific undersize reamer for the bearing. We really only use two size bearings on 95% of 973's robots, so it was a great investment (same for broaches, etc...).

[Richard Wallace]

Originally Posted by JesseK

McMaster # 9056K11 (or similar from a less expensive supplier) might be a good start for Richard's design.

Jabba ordered 9056K151. $38.69 for a one foot length of 2" o.d. 1" i.d. 6061 aluminum tube.

Jesse is right, there are cheaper sources. I change my password more frequently now, to make it more difficult for Jabba to place unauthorized McMaster orders. He prefers them because they deliver his material next day.

[Mk.32]

For the press fit bearings, should the hole be something like .001 inch undersized? Or the same as the bearing diameter?
We have an HAAS CNC we can use, I am not sure if we have any reamers so I planed to just bore them out with a 1/2 milling bit.

[Brandon Holley]

Originally Posted by JesseK

Without a DRO, how would one check the bored diameter? Is the only way to start/stop the lathe constantly?

DROs are nice, but definitely not necessary for just about everything you can do on a machine. As others have said, even with the DRO, a proper bore will require several starts and stops.

The fastest way will definitely be to get close and then ream. It will probably give you decently repeatable results as well.

We are fortunate enough to have a set of bore micrometeres at our disposal. They are extremely nice, and extremely expensive. We only allow experienced machinists to handle them and use them. They do make checking bore sizes a breeze though, and in our experience, are extremely eaccurate.

-Brando

[davidrk13]

is there any way of doing it with the wheels being off centered?

[EricH]

Originally Posted by davidrk13

is there any way of doing it with the wheels being off centered?

Depends on what you mean by "off centered". If you mean with the center wheel dropped, that's standard WCD configuration. If you mean the center wheels moved forwards or backwards, then you do pretty much the same thing as what is shown in the picture.

If you mean that your wheels don't have the axles in the center, well, that ought to provide some comedy to anybody watching you bounce around a lot.

[zcoops97]

Originally Posted by Mk.32

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Over on team 340, we had a similar concept... Andymark supershifters that worked great... had our chain runs inside 1.5 by 2 inch tubing (1/8 inch wall), easy to get to with the right pocket placement, and much, much safer... still had the 1/8 inch drop center, wedge top tread. We were pretty happy with our drive base this year