clevis holes .001 different

[ken king, King DesignParticipant @kenkingkingdesign]

I have some loco parts to make and on the drawing several of the clevis ends have one side specified as, say, 0.125 dia. whilst the other side is 0.124, the idea being that a press fit on one side retains the pin. Fair enough, but can someone with more experience please explain how this is best achieved ? I gather it's not an unusual feature so presumably there's a tried and tested method. Please help !

[ken king, King DesignParticipant @kenkingkingdesign]

I have some loco parts to make and on the drawing several of the clevis ends have one side specified as, say, 0.125 dia. whilst the other side is 0.124, the idea being that a press fit on one side retains the pin. Fair enough, but can someone with more experience please explain how this is best achieved ? I gather it's not an unusual feature so presumably there's a tried and tested method. Please help !

[ken king, King DesignParticipant @kenkingkingdesign]

I have some loco parts to make and on the drawing several of the clevis ends have one side specified as, say, 0.125 dia. whilst the other side is 0.124, the idea being that a press fit on one side retains the pin. Fair enough, but can someone with more experience please explain how this is best achieved ? I gather it's not an unusual feature so presumably there's a tried and tested method. Please help !

[ken king, King DesignParticipant @kenkingkingdesign]

[JasonBModerator @jasonb]

Depending on how far apart the two holes are it is possible to drill a little undersize as if reaming, then use a hand reamer but don't go in too far. This will open the first hole to 0.125 but as the second will still not have reached the end of the lead in taper so it will be a little undersize.

J

[JasonBModerator @jasonb]

Depending on how far apart the two holes are it is possible to drill a little undersize as if reaming, then use a hand reamer but don't go in too far. This will open the first hole to 0.125 but as the second will still not have reached the end of the lead in taper so it will be a little undersize.

J

[JasonBModerator @jasonb]

Depending on how far apart the two holes are it is possible to drill a little undersize as if reaming, then use a hand reamer but don't go in too far. This will open the first hole to 0.125 but as the second will still not have reached the end of the lead in taper so it will be a little undersize.

J

[Paul LousickParticipant @paullousick59116]

Similar to Jassons answer. Use an adjustable reamer. Ream thru both holes so that they are concentric to the minimum size and then adjust the reamer and open up one side only.

[Paul LousickParticipant @paullousick59116]

Similar to Jassons answer. Use an adjustable reamer. Ream thru both holes so that they are concentric to the minimum size and then adjust the reamer and open up one side only.

[Paul LousickParticipant @paullousick59116]

Similar to Jassons answer. Use an adjustable reamer. Ream thru both holes so that they are concentric to the minimum size and then adjust the reamer and open up one side only.

[ken king, King DesignParticipant @kenkingkingdesign]

Yes, I can see that an adjustable reamer would work on larger holes, but 0.125 ? I should also add that the clevis ends are 0.125 apart, so not much distance with respect to tapers either. Actually, I've never checked a tapered reamer to see what the diameter difference would be over such a short distance. At the smaller side, a lightly tapered hole is no bad thing for the press fit, but to make the other side parallel, well, I can only think of the tip of a machine reamer, which has very little lead-in, but that's two reamers for each clevis size and £'s begin to add up!

[ken king, King DesignParticipant @kenkingkingdesign]

Yes, I can see that an adjustable reamer would work on larger holes, but 0.125 ? I should also add that the clevis ends are 0.125 apart, so not much distance with respect to tapers either. Actually, I've never checked a tapered reamer to see what the diameter difference would be over such a short distance. At the smaller side, a lightly tapered hole is no bad thing for the press fit, but to make the other side parallel, well, I can only think of the tip of a machine reamer, which has very little lead-in, but that's two reamers for each clevis size and £'s begin to add up!

[ken king, King DesignParticipant @kenkingkingdesign]

Yes, I can see that an adjustable reamer would work on larger holes, but 0.125 ? I should also add that the clevis ends are 0.125 apart, so not much distance with respect to tapers either. Actually, I've never checked a tapered reamer to see what the diameter difference would be over such a short distance. At the smaller side, a lightly tapered hole is no bad thing for the press fit, but to make the other side parallel, well, I can only think of the tip of a machine reamer, which has very little lead-in, but that's two reamers for each clevis size and £'s begin to add up!

[Anonymous]

I'd be inclined to change the design to something more practical. There are several options:

1. Thread one hole, and the pin, with or without a shoulder on the pin, and assemble with or without thread lock

2. Put a shoulder on the pin and loctite the smaller end in place

3. Put a shoulder on the pin and lightly rivet it in place

No doubt there are other options.

Regards,

Andrew

[Anonymous]

I'd be inclined to change the design to something more practical. There are several options:

1. Thread one hole, and the pin, with or without a shoulder on the pin, and assemble with or without thread lock

2. Put a shoulder on the pin and loctite the smaller end in place

3. Put a shoulder on the pin and lightly rivet it in place

No doubt there are other options.

Regards,

Andrew

[Anonymous]

I'd be inclined to change the design to something more practical. There are several options:

1. Thread one hole, and the pin, with or without a shoulder on the pin, and assemble with or without thread lock

2. Put a shoulder on the pin and loctite the smaller end in place

3. Put a shoulder on the pin and lightly rivet it in place

No doubt there are other options.

Regards,

Andrew

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

IHi Ken ,

It's all a bit silly really – the tolerance on any readily available pin material and the uncertainty of such small reamers cutting dead size means that some samples of pin material won't enter either hole and some will fall right through .

Unless you can get some precision pin material only way forward is to use Jason's method and basically hand fit each pin to each hole pair .

Be alert to the fact that if any press fit turns out to be too severe then there is a real danger of bending fork ends when trying to press pin in .

The apparently similar arrangement seen on full size locomotives was actually quite different – pivot pins were precision fit/transition fit in both holes but actually held in place with taper pins in the fork sides .

If you want your arrangement to look right then the pins are easy enough to do . 1/32 inch diameter would be more than adequate .

Regards ,

Michael Williams .

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

IHi Ken ,

It's all a bit silly really – the tolerance on any readily available pin material and the uncertainty of such small reamers cutting dead size means that some samples of pin material won't enter either hole and some will fall right through .

Unless you can get some precision pin material only way forward is to use Jason's method and basically hand fit each pin to each hole pair .

Be alert to the fact that if any press fit turns out to be too severe then there is a real danger of bending fork ends when trying to press pin in .

The apparently similar arrangement seen on full size locomotives was actually quite different – pivot pins were precision fit/transition fit in both holes but actually held in place with taper pins in the fork sides .

If you want your arrangement to look right then the pins are easy enough to do . 1/32 inch diameter would be more than adequate .

Regards ,

Michael Williams .

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

IHi Ken ,

It's all a bit silly really – the tolerance on any readily available pin material and the uncertainty of such small reamers cutting dead size means that some samples of pin material won't enter either hole and some will fall right through .

Unless you can get some precision pin material only way forward is to use Jason's method and basically hand fit each pin to each hole pair .

Be alert to the fact that if any press fit turns out to be too severe then there is a real danger of bending fork ends when trying to press pin in .

The apparently similar arrangement seen on full size locomotives was actually quite different – pivot pins were precision fit/transition fit in both holes but actually held in place with taper pins in the fork sides .

If you want your arrangement to look right then the pins are easy enough to do . 1/32 inch diameter would be more than adequate .

Regards ,

Michael Williams .

[Joseph RamonParticipant @josephramon28170]

Michael is right.

This is a good example of where the "best practice of fully dimensioned and toleranced drawings" as used in industry is clearly folly.

Even the old style 1/8" full and 1/8" bare would be more useful, though a simple 1/8" dimension with the note to make one end a press fit would be best.

In practice I'd make both holes undersize on the pin material, then open one up with a broach, reamer or even a drill in a pin chuck.

Joey

[Joseph RamonParticipant @josephramon28170]

Michael is right.

This is a good example of where the "best practice of fully dimensioned and toleranced drawings" as used in industry is clearly folly.

Even the old style 1/8" full and 1/8" bare would be more useful, though a simple 1/8" dimension with the note to make one end a press fit would be best.

In practice I'd make both holes undersize on the pin material, then open one up with a broach, reamer or even a drill in a pin chuck.

Joey

[Joseph RamonParticipant @josephramon28170]

Michael is right.

This is a good example of where the "best practice of fully dimensioned and toleranced drawings" as used in industry is clearly folly.

Even the old style 1/8" full and 1/8" bare would be more useful, though a simple 1/8" dimension with the note to make one end a press fit would be best.

In practice I'd make both holes undersize on the pin material, then open one up with a broach, reamer or even a drill in a pin chuck.

Joey

[Chris HeapyParticipant @chrisheapy71135]

Just drill 7/64" then poke a 1/8" reamer through until you see its cutting edges appear on the far side. Put a faint chamfer on the pin and press it in. Job done. Sometimes we over-think these things…

[Chris HeapyParticipant @chrisheapy71135]

Just drill 7/64" then poke a 1/8" reamer through until you see its cutting edges appear on the far side. Put a faint chamfer on the pin and press it in. Job done. Sometimes we over-think these things…

[Chris HeapyParticipant @chrisheapy71135]

Just drill 7/64" then poke a 1/8" reamer through until you see its cutting edges appear on the far side. Put a faint chamfer on the pin and press it in. Job done. Sometimes we over-think these things…

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