How to straighten drill press arbor

[guythatbrews]

I have a Digital Mahr MarCator 1087R, .0001 to 1.0 with an arm mounted to the spindle to reach under the shaft. For the V block setup it is a Girod 0.0001 to +/- 0.0055" test indicator, it does not seem as stable.

One thing I notice is the chuck moves by several tenths as I rotate it by hand, pretty sure its in the bearings I am not sure if that is normal, I have an old south bend lathe with bushings and oil lube so there is some clearance in there for oil, between 0.001 and 0.0007".

I am very happy with how it came out, the bottom of the spindle is about 3 tenths when supported by the journals. The test arbor is about 1 mil TIR near the spindle and 3.5 mils at 6 inches away, about where the end of a drill bit would be. This was close to 1/8" when I got the drill. Thanks again for the most excellent suggestions.

Patience and hard work pays off! Great work! Always nice to see old machines brought back into condition.

 

[metalmagpie]

They used acetylene torches and skill to bend the I-beam legs of the Seattle Space Needle.

But to straighten a shaft I suggest sawing a pair of V blocks from aluminum. Set up an indicator and push down on the high part. Take your time and you can work it to sub-thou runout.

 

[Turbowerks]

One thing about pressing things straight, it seems they will bend back easier in use , but wen you peen it , seems like the metal retains it memory better. Learned this on crankshafts hardly ever press the always peen the radius and they stay put


When I find it I don’t need it
When I need it I can’t find it!

 

[Tony Quiring]

Back in the day spent much time straightening both camshafts and grankshafts in a production shop.

Never any presses.

8 ox ball pie hammer and chisel with DI used on cam between centers and cranks in V blocks.

Hardest part was getting brain to remember that shaft goes TOWARDS the impact as stresses are removed or material is expanded causing the side being hit to get longer causing it to move.

For a drill press spindle the spot that is actually bent needs to be located first.

Cranks and cams are easy, bends at corners.

If a straight smooth shaft and is bent in center of smooth spot it can still be done with chisel, the bumps will need to be removed with a file after.

Sent from my SM-G781V using Tapatalk

 

[eKretz]

For press straightening I always had better luck getting things to stay put if I overbent them a little then brought them back to straight again. Don't know why, but I noticed it happened reliably after repeated instances, so I started doing it on purpose. Peening works good too but takes longer. It's a lot easier to fine tune with. Sort of like a laser guided missile vs a cluster bomb.

 

[CarbideBob]

When I worked in a round tool HSS shop it was common practice to peen the shanks to "straighten" tools that had too much runout at inspection.
I always wondered if this was permanent or if over time and/or under use the induced stress would relax.
Has anyone peened to straight and then checked it 4 years later?
Bob

 

[ratbldr427]

Lots of good info. Mapping the part is most important. You may find compound bends and also twisted shafts. I have found some materials work harden at the bend and depending on the anvil spacing you can induce a bend away from the bend you are trying to straighten. Bending to an adjustable stop(Screw or shims) is the best way. Gard I think that was what you meant by pitting a jack under the part. That reduces the influence that the press frame flex has. Some times you get close and the work over bends. I have seen some shaft presses that had a large C section that hinged like a steady rest with the ram on top and pressed against a jack stop.
A milling machine vise and three shims is my quickie for small parts.
For pressing against threads non critical just cut a matching nut in half to press against threads without damaging them.

 

[Gard]

Lots of good info. Mapping the part is most important. You may find compound bends and also twisted shafts. I have found some materials work harden at the bend and depending on the anvil spacing you can induce a bend away from the bend you are trying to straighten. Bending to an adjustable stop(Screw or shims) is the best way. Gard I think that was what you meant by pitting a jack under the part. That reduces the influence that the press frame flex has. Some times you get close and the work over bends. I have seen some shaft presses that had a large C section that hinged like a steady rest with the ram on top and pressed against a jack stop.
A milling machine vise and three shims is my quickie for small parts.
For pressing against threads non critical just cut a matching nut in half to press against threads without damaging them.

One curious thing I saw was the indicator that measured deflection and subsequent TIR of the shaft got higher after loading. For example, I initially set it up to read +/- 1.5 mill as the shaft is rotated on V blocks in the press, after applying several loads it read +0.8 and -0.1 mills. This did not cause me a problem because each time I applied a load I rotated the shaft to check. There must of been something moving someplace but its curious the centerline of the shaft got higher with respect to the indicator.

If I was getting paid to do this or had a bunch of them to do, I would probably investigate further to figure out what is happening. In my previous job I would sometime have over 1/2 dozen very expensive federal electronic gauges reading different points on the same part all going into the spreadsheet automatically along with the load cell force and temperatures in a cleanroom. Some of my co workers would laugh now seeing the HF press in the barn, tooling made from rusty old signposts etc.

 

[TaperPin]

While it’s not needed for this project, I suspect you would enjoy seeing the results of flame straightening. At its most basic level a small dot is heated and expands, but is held by the surrounding metal from expanding so it is forced outward slightly and remains slightly bulged even when cooled, so the original area contracts because it has less volume.

The heated area has to be constrained from expanding, either by surrounding metal, or by outward forces like clamps, or whatnot. If a shaft is supported on both ends and a dime size area is heated in the middle on top, we all know the shaft would want to rise in the middle from expansion - some shrinkage of that area will occur when cooled if it was enough heat to bulge the metal, but if the shaft were constrained with a clamp (or press) even more shrinkage would occur with the exact same amount of heat.

On damaged bridges, or boats, driveshafts, or sheet metal, the heated areas look like grids with dots where heat was applied to multiple spots and often in multiple passes to more uniformly shrink an area.

The amount of heat doesn’t have to make the area glow red - and water doesn’t have to be used on the heated area, but it does allow additional heating to continue faster, and keeps the overall part cooler making measurements more meaningful. Some people use compressed air to cool the heated area.

It’s a nice tool to have if the bend is in a tight spot since the shrinkage can be limited to a short section.

Anyway, it’s a fun skill to learn.