Reamer vs. End Mill Hole Quality?

[RaisedByWolves]

Crankshaft bore on flywheel for I.C. Model engine. I can turn the crankshaft to fit the bore. Might just have to break down and buy a US made reamer

Are you doing this on the lathe or mill?

Second best way to go about this is with a reamer in the mill.

Best way to go about it is to bore it on the lathe.

A reamer in a mill will give you a slightly (Depending) inaccurate bore alignment due to the mill head not being trammed true, and it is nearly impossible to tram it as true as you would get boring it in a lathe.

A reamer, in even a good well set up lathe will likely leave you with a slightly tapered bore due to several factors such as tailstock misalignment, radial inaccuracies in the tail stock drill chuck, and to a lesser extent the straightness of the reamer shank.

 

[extropic]

A two flute end mill will probably act as a boring bar (single point) due to even slight runout in the collet/spindle.
Drill the hole 19/64" and then slowly plunge with a sharp 2 flute EM.

Your mill head needs to be accurately trammed or you will end up with the hole slightly askew.

 

[whitmore]

If this is for a bore that gets lubricated, you might not WANT a fine finish; a bit of
tooling texture will hold the oil better. I'd go with a drill, and if finish isn't great,
hone with some metal polish or abrasive against a spinning rod.

Fine fits for locating pins or slip fits for permanent assembly is why to get a reamer.

 

[WobblyHand]

Find some cheap good reamers, preferably from a country that still makes good stuff. Don't trust the markings on the reamer. Measure them and return any that are not correct. Reamers are measured just past the chamfer. Rotate the edges to get the widest measurement. I had one heck of a time getting decent ones. I tried buying an over and under set (import) and 95% of the unders were over! I obviously returned them. The seller questioned me and I simply sent a picture of my Mitutoyo mic and the mic reading.

Ended up getting most of mine from a fellow HM member, primarily used American reamers. I did fill the set in with some eBay buys. From eBay I've received some mislabeled reamers, really junky reamers, and some really nice ones. The reamer that was marked 5/16 - 0.001 got my attention, yeah, it was junk. (The picture didn't show that, it was listed to 4 decimal points.). All my other reamers were marked to four decimal places, at least for inches. 0.xxxx"

Reamers are accurately ground, so your measurements should match the label on the tool, practically to the tenth.

I never thought I needed any reamers, until I used one. Quite handy to have around.

 

[ShagDog]

Are you doing this on the lathe or mill?

Second best way to go about this is with a reamer in the mill.

Best way to go about it is to bore it on the lathe.

A reamer in a mill will give you a slightly (Depending) inaccurate bore alignment due to the mill head not being trammed true, and it is nearly impossible to tram it as true as you would get boring it in a lathe.

A reamer, in even a good well set up lathe will likely leave you with a slightly tapered bore due to several factors such as tailstock misalignment, radial inaccuracies in the tail stock drill chuck, and to a lesser extent the straightness of the reamer shank.

Doing it in the lathe. You just saved me some money on the reamer (Around $25.00 for a good USA one here at a local industrial supply store). I don't think I have a small enough boring bar, but I will grind one if necessary. Since I want the bore concentric to the rest of the flywheel, you hit it right on the head that boring while set up in the lathe is likely the best option. Plus, I will need to bore a .500" diameter x .188 deep hole for the cam drive gear spigot on one side of the flywheel concentric with the 5/16" through hole. I appreciate your help and the help of others on this forum in "brainstorming" this.

 

[RaisedByWolves]

If this is for a bore that gets lubricated, you might not WANT a fine finish; a bit of
tooling texture will hold the oil better. I'd go with a drill, and if finish isn't great,
hone with some metal polish or abrasive against a spinning rod.

Fine fits for locating pins or slip fits for permanent assembly is why to get a reamer.

Every model IC plain bearing engine I have ever seen has had a mirror finish on the bore with ~.0005-.002 clearance depending on the size of the engine.

Any ridges will get pounded down through the action of the engine firing and forcing the crank downward on every stroke. This will lead to the crank quickly developing excessive clearances and cause the engine to suck air if a two stroke or leak oil in a 4 stroke.

Doing it in the lathe. You just saved me some money on the reamer (Around $25.00 for a good USA one here at a local industrial supply store). I don't think I have a small enough boring bar, but I will grind one if necessary. Since I want the bore concentric to the rest of the flywheel, you hit it right on the head that boring while set up in the lathe is likely the best option. Plus, I will need to bore a .500" diameter x .188 deep hole for the cam drive gear spigot on one side of the flywheel concentric with the 5/16" through hole. I appreciate your help and the help of others on this forum in "brainstorming" this.

Best simple option would be to use an endmill for your boring bar. A dull or one with a chipped flute would be ideal as long as you can get the length you need. You can partially or completely grind off the flute you will not be using to make a larger endmill fit your needs. A 3/8" with the flutes completely ground off save for 3/16"-1/4" of the tip of one flute remaining would be ideal.

 

[ShagDog]

...

...
Best simple option would be to use an endmill for your boring bar. A dull or one with a chipped flute would be ideal as long as you can get the length you need. You can partially or completely grind off the flute you will not be using to make a larger endmill fit your needs. A 3/8" with the flutes completely ground off save for 3/16"-1/4" of the tip of one flute remaining would be ideal.

I do have a boring head with a MT2 taper that goes up to .385" max diameter. I did also already grind a hss lathe tool bit to put in my QCTP holder. But, when all is said and done, I did end up ordering a USA made 5/16" reamer on Ebay for just under $20.00 shipped.

What I intend to do is drill the hole and bore it out to the appropriate size for the reamer. The reason I did end up ordering the reamer is that the bronze bushings to be made also need the same diameter as the reamed bore of the flywheel. I figured it would be much easier to get good size match between the bore of the bearings and of the flywheel with the reamer than trying to duplicate each with boring. Plus, I have now added what I expect to be a quality reamer to my reamer arsenal.

 

[tobnpr]

Depth of the hole to full diameter needs to be deeper with a drill than if cut with a reamer or end mill, if the hole goes nearly to the bottom of the part this may be a problem.

 

[ShagDog]

Depth of the hole to full diameter needs to be deeper with a drill than if cut with a reamer or end mill, if the hole goes nearly to the bottom of the part this may be a problem.

These are through holes.