Reamer using

[kevin.decelles]

I picked up 5 or 6 imperial sizes from KBC about 6 months ago. 1/4, 5/16, 3/8 etc. Just checked the pricing on them, they've gone up about 25% since then. They are ok for my use.

 

[Brent H]

So reamer usage, couple things to consider:

Bushings (like the Oilite, sintered bronze etc) will come with the OD sized to properly press fit into a precision hole. So you want to fit a 3/4” OD bushing with a 1/2” ID - bore then ream the hole to 0.750” or 3/4”. The bushing comes with the press fit accounted for.

Fitted bolts: hole is drilled and reamed to exactly 1/4” or 0.250”. Bolt is then machined to exact fit.

For slight changes of “fit” you can get adjustable reamers. These come in various configurations- tapered cutters that adjust for a wider range. I also have some that have a set screw adjustment to allow for finer precision adjustments - like making a 0.750 reamer a 0.751 reamer.

Custom fits can be had depending on your project and I have some odd ball size reamers that were made specifically for some injection molding fabrication.

Buy quality if you can and sometimes it is better just to get the ones you need rather than a set. It is not often you would ream a precision hole under 1/4” unless it was specific for fitting an alignment pin or you were using a tapered pin - than you have a whole other bunch of tapered reamers to acquire that will be specific to the pin you are fitting 0,1,2, 3 etc or metric or Morse taper, Brown and Sharpe - UGH!

 

[Blouin55]

So reamer usage, couple things to consider:

Bushings (like the Oilite, sintered bronze etc) will come with the OD sized to properly press fit into a precision hole. So you want to fit a 3/4” OD bushing with a 1/2” ID - bore then ream the hole to 0.750” or 3/4”. The bushing comes with the press fit accounted for.

Fitted bolts: hole is drilled and reamed to exactly 1/4” or 0.250”. Bolt is then machined to exact fit.

For slight changes of “fit” you can get adjustable reamers. These come in various configurations- tapered cutters that adjust for a wider range. I also have some that have a set screw adjustment to allow for finer precision adjustments - like making a 0.750 reamer a 0.751 reamer.

Custom fits can be had depending on your project and I have some odd ball size reamers that were made specifically for some injection molding fabrication.

Buy quality if you can and sometimes it is better just to get the ones you need rather than a set. It is not often you would ream a precision hole under 1/4” unless it was specific for fitting an alignment pin or you were using a tapered pin - than you have a whole other bunch of tapered reamers to acquire that will be specific to the pin you are fitting 0,1,2, 3 etc or metric or Morse taper, Brown and Sharpe - UGH!

What is the rule for press fitting, ex pressing a half inch pin in a hole?

 

[Brent H]

Directly from the bible we have the pin fits


From the chart you can see that a proper 1/2” dowel pin would be ground to 0.5001 to 0.5003” and the hole is going to be 0.5000 to 0.4995. This would give you a light press fit of just 0.0001” or a bit tighter at 0.0008”. This is for assembly and location so you can actually take the thing apart.

 

[Brent H]

If you are going for a solid fit the basic rule would be 1 to 3 thou up to 3/4” shaft - less of a press the weaker or more brittle your material. Above 3/4” you are pretty reasonable at 0.003” depending on application.

If you are pressing the 1/2” shaft into a permanent fixture you would be solid at 1.5 to 2 thou.

 

[Blouin55]

If you are going for a solid fit the basic rule would be 1 to 3 thou up to 3/4” shaft - less of a press the weaker or more brittle your material. Above 3/4” you are pretty reasonable at 0.003” depending on application.

If you are pressing the 1/2” shaft into a permanent fixture you would be solid at 1.5 to 2 thou.

Very usefull information

 

[Susquatch]

For example my next project will be to make a lathe bed stop and i want i want to have an indicator in it.
Do i need a reamer or only a drill bit will make the job?

A Reamer is almost always better than drilling.

HOWEVER, for something like a, screw hole or a clamping hole, I would just drill and go.

I am planning a lathe stop someday too. I've never used one, but I can see the advantages it might offer. I am NOT PLANNING to get a Reamer for that job. In my view, the job simply doesn't require that kind of precision.

The indicator shaft clamping force is minimal and the alignment isn't that critical either. So I won't be bothered about it.

 

[Chicken lights]

So....what about rubber grommets? I have some that call for a 3/4” hole. Last time I used a 3/4” hole saw and they were way too sloppy. So I picked up a 47/64 drill bit in Edmonton with @Everett thinking try going under size first. If it’s too tight ream it to 3/4”. But if I did the math right it’s only 0.015” undersize?

I have a 1” tapered reamer that’s awesome for wallering in holes, when you don’t know what size the hole needs to be, you can just keep making the hole bigger until it fits the part. They are grabby to use though, I’ve had the best luck with lots of oil, high speed and light feed

 

[Brent H]

@Chicken lights - your drill at 47/64 should be fine, unless the 3/4 rubber is a lot bigger than 3/4.

Folks need to keep in mind that a drill bit is a “roughing out” tool and will rarely yield a hole that is to a specification. Drill chucks are not “precise” and a drill in your hand control adds to some lack of precision. The drill bit itself may not bore a hole that is the actual size of the bit. Off centre sharpening will typically add a few thou as well.

The crazy processes of making holes!

 

[YotaBota]

Speaking from a hobby non-machinist point, I have sets of Number, Letter and Fractional drill bits and most times I can get close enough to not need a reamer (using the mill). I may get a set of Metric bit to fill in the gaps but haven't needed them "yet". There are a number of charts online that will show the decimal equivalent for the drill bits.
Like @Brent H says, drills are a rough estimate so start a couple of bit sizes smaller and work up to the hole size needed.
Having said that there will be times when the only way to get the tolerance required is with a reamer.