Press Fits

[FLtenwheeler]

What is the correct diameter of a 5/8” axle into a cast iron wheel that has a reamed hole. Is there a formula to calculate it?

Thanks

Tim

[Bill Shields]

I go with .00075" per inch of diameter.

But then I am also a believer in Loctite products

[arborist]

When you are searching, using the term 'interference fit calculator' will broaden the results you see:

e.g. https://www.tribology-abc.com/calculators/e3_8.htm

[Harold_V]

You should be aware that a reamed hole isn't necessarily a good hole. If you assume that a reamer yields a hole the size of the reamer, you may find that you don't get a press fit. That's for many reasons, including the fact that reamers are notorious for creating tapered (bell mouthed) entries, multi-sided holes (usually one more side than the reamer has flutes) and may simply cut oversized because one edge (flute cutting edge) is buggered and causes the reamer to cut oversized. Bottom line---the hole may or may not be straight and round, although generally much improved over a drilled hole.

Rule of thumb for a press fit is one thou of interference per inch of diameter.

H

[FLtenwheeler]

Harold you are correct. A reamer doesn’t produce a perfect hole. I found a treasure trove of information on the internet. A 5/8” reamer can produce a hole 0.0006” oversized and still be acceptable for class H7 hole size. So this has to be taken into account for the shaft sizing.

Cast iron will only take some much before it fails.

Then what equipment is available to assemble the parts. I only have a 5 ton arbor press in the shop so I heated the wheels to ease the pressure.

When I installed the tires on my driver I used 0.001” per inch plus one. The tires were heat soaked to 500 degrees F for an hour. They turned a nice blue color. After they cooked the axle hole closed up 0.0002” of an inch.

Loctite is a great product when used correctly. I see many people using the wrong product for the application as the major fail. I have fixed many loose wheels over the years for people. I have a Loctite product the will hold a drive and set in under 5 minutes. Great for use at meets.

Tim

[FLtenwheeler]

Here is a chart that I came up with using Solidworks.

Tim

[GlennW]

Don't forget that surface finish is a factor as well.

Especially if you are planning to measure to four decimal places.

[liveaboard]

Getting an accurate measurement of the hole is the major difficulty with press fits for amateurs (like me).
External micrometers are affordable, but internal ones are beyond my budget.
So I use telescoping cheapo thingies to transfer the measurement to an external micrometer, a process prone to error.

Patience and many repeat measurements are how I overcome this, and a 20 ton press is useful too.