Drill size before reaming?

[butchlambert]

How much do I need to leave before reaming? Maybe 015" under reamer size. Holes will be .200 to .500.

 

[WSnyder]

Here's what I'd shoot for Butch. .010" for under .250" and .015" for .250"-.500"

 

[gunsandgunsmithing]

3% under reamer...rule of thumb.

 

[butchlambert]

Here's what I'd shoot for Butch. .010" for under .250" and .015" for .250"-.500"

About what I thought. Thanks

 

[hogpatrol]

I'd just do .010 on the side. Maybe smaller with the .200.

 

[Dimner]

There is a chart somewhere for this I think? At least I remember something like that back in shop class.

 

[ridgeway]

10-15 thou. Half the speed, twice the feed will get er done

 

[butchlambert]

There is a chart somewhere for this I think? At least I remember something like that back in shop class.

I looked in my 1959 issue of the Machinist Handbook, but didn't find it.

 

[Dimner]

I looked in my 1959 issue of the Machinist Handbook, but didn't find it.

In my shop class, might of been something from the reamer manufactuer. However, it did keep most of us dummies from messing our projects up.

Shop teacher: "check the chart" was a fav quote. There were quite a few charts in the room that answered all kinds of questions. So now, when ever I have a question like this I think to my self "I bet there is a chart for that"

 

[butchlambert]

In my shop class, might of been something from the reamer manufactuer. However, it did keep most of us dummies from messing our projects up.

Shop teacher: "check the chart" was a fav quote. There were quite a few charts in the room that answered all kinds of questions. So now, when ever I have a question like this I think to my self "I bet there is a chart for that"

Must be, but I never found it. .010-.020 won't hurt me.
Thanks for the suggestions.

 

[xr650rRider]

The amount of material left in the hole prior to reaming “pre-ream hole size” plays an integral role in the quality of the reamed hole. The pre-ream hole size affects characteristics in the reamed hole including hole finish, hole straightness, tool life, and cycle time. There are several ways in which the pre-ream hole size may be obtained some examples include investment casting, boring, line boring, rough reaming, and stamping. The most common way to obtain the pre-ream hole size is through drilling and the focus of this blog entry. The appropriate amount of stock removal for carbide tipped and solid carbide reamers is generally 2 – 3 percent of the finished hole size. Carbide tipped and Solid Carbide Reamers need to have adequate stock to remove or they will rub in the hole and generate excessive heat. This leads to premature tool wear and poor hole finishes.

 

[gunsandgunsmithing]

Must be, but I never found it. .010-.020 won't hurt me.
Thanks for the suggestions.

Two factors really...don't overload the flutes with chips but also, leave enough material that the reamer has to actually cut rather than rub tight. The 3% rule I posted earlier came from when I did tool and die work full time. That stuck with me for all these years and has never let me down. But yeah, there's almost certainly a chart somewhere, too. You can get by with more and less with different reamers and materials, Really, as much as we scrutinize everything in the gun business, a chamber reamer is probably the hardest reamer to get just right of any but yet, some pre-drill/bore and some use a finish reamer from start to finish with good results both ways. Hole depth is another factor and it seems like there was a rule regarding that too but I don't remember that one. Lol! 3% rule covers a lot of ground though.

 

[butchlambert]

I'm doing an upgrade on my case forming die bushings. 12 sizes of bushings from .200-.500. Bushings are .625" in height and OD. Mild steel with Melonite case hardening. I can size a piece of 458 Lott brass to a 17 cal.