Has anyone tapped a drill rod?

[WarrenW]

I have some 1" drill rod and I was thinking about tapping it to mount down for support and then using some open linear bearings or using roller bearings mounted on some angle like many do.

I want to go about 4 feet with the drill rod so thats why it needs to be supported. I got the drill rod from enco.

Warren

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[HuFlungDung]

Drill rod is typically supplied annealed, so its not bad to work with. Its maybe a little tough, but if you use a nice tapping fluid, or even sneak a little bit of lard out of the kitchen for your thread tap, it should not be any problem, with a sharp tap.

[fyffe555]

Warren,

Unsurprisingly Hu has it right I've tapped the enco drill rod, the trick is to use lube, a good tap (not a Harborfreight black oxide special) and take out the swarf frequently.

Another suggestion is that if you have a drill press use it to control the tapping process. UNPLUG the press, Hold the rod on a vice, chuck the tap and turn the chuck by hand while controlling the pressure on the spindle with the other. It keeps alignment, and if it gets too tight to turn by hand then back off and try again, saves missaligning holes and breaking/sticking taps.

Also, watch your tolerances on the drill rod and the bearings. Enco drill rod is supposedly +/- 0.001 but mine was all -0.000 - 0.003

If you're using , say igus R series their tolerances are +0.0016 to + 0.0036 and you will have at least 1 thou and up to almost 6 thou on the bearing clearance. Mine are loose but it's on a sliding table on my saw so its ok. Also since the bearings are plastic, unless you're getting them in pillowblocks watch the install sizes too as if the hole is under size or not exactly round they will compress the bearing and it won't fit. Don't ask me how I know that...

If you're using ball bearings watch the tolerances again, too tight will tear up the rod..

let us know how it goes..

Andrew

[DareBee]

Just to share some experience.
Having tried ball bearing type linears on unhardened shaft - if there is any sort of load at all or a lot of movement, the bearings will gouge into the rod VERY quickly. I attemted to run a couple hundred pounds on 1" and it gouged instantly.
If you intend to use bushings (bronze, UHMW, Frelon lined, etc) it should last a respectable amount of time.
Having said all that, for the little extra money of hardened rail and the fact that I prefer to do things only once I would not use soft rail for ANY application that bears weight or is repetitive.

[WarrenW]

Thanks for the tips! Maybe I should just use skate bearings like some do on this rod. Will it hold up to that or still too soft? I have seen where people use black pipe with the skate bearings. Is the black pipe stronger than drill rod?

Warren

[DareBee]

You drill rod should work good with skate bearings. The key to using unhardened material is to have enough surface area contact.
Drill rod (which is normally O1) is at least twice as hard as CRS in it's soft state.
You could consider having the rod hardened after you are done machining it to suit your needs. After heat treat you could likely get away with a quick hand polish to clean it up.

[jeffs555]

Warren,
It is all about contact area. The amount of penetration into the rod is proportional to the force applied divided by the contact area. The equations are complex, and I haven't worked them all out, but believe that the depth of penetration varies by more than the square of the diameter of the bearing. If you double the diameter of the bearing, the penetration should be more than 4 times less. I don't know what size the balls are in the typical linear bearing, but a 22mm skate bearing should penetrate at least 50 times less than a single 1/8" ball. The linear bearing will have more than one ball in contact with the rod, but even with ten 1/8" balls carrying the load, the skate bearings would still cause at least 5 times less damage to the bar.

I don't know if black pipe is harder than unhardened drill rod, but from cutting both, I would guess that they were close to the same hardness. If anything the pipe might be softer, because it seems a little easier to cut and drill.

It would be interesting to see some real world wear results from people using the skate bearings on unhardened rod.

Jeff