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Steve Steven
08-12-2009, 09:43 PM
I am trying to ream a taper pin hole, for a #1 taper pin (.147 to .197 dia, 2 inches long). I am reaming what I think is cast iron, it drilled like cast iron.

I drilled with three drills, sized to reduce the load on the reamer. I started with the reamer, it went down ok, just a little slow. As soon as the reamer started cutting all the way, it just stopped cutting.

All I am getting on the flutes for chips is a black powder, no real chips at all.

The reamer is from MSC, an import. It seems sharp, the edge does not seem dulled, but will not cut. I have not turned it backwards. I am bearing down fairly heavily trying to get it to cut.

I need to get the pin to go down 1.3 inches, right now I am at 1 inch.

Any suggestions on what I need to be doing?

Thanks for any help.

Steve

flutedchamber
08-12-2009, 09:47 PM
If it is indeed cast iron that you are working with you could have hit a sand inclusion which is too hard for the reamer to cut.

Perhaps you can detect the inclusion by sliding a sharp edged pin punch down the side of the hole and "feel" for a slick spot which would be the inclusion. Don't forget that you will have to "feel" the full 360 degrees and from top to bottom.

loose nut
08-12-2009, 10:09 PM
Some types of iron produce what looks like graphite powder not chips, it could be a hard spot in the iron too, that would be a problem for a HSS reamer, about all you can do is go slow and cross your fingers.

gwilson
08-12-2009, 10:45 PM
How slow are you turning(lathe RPM?). Turn very slow. Cast iron can really dull tools fast if it is cut at too high an rpm. Your reamer may feel sharp,but you may have worn the cutting edge just enough that it now has zero clearence. Look at the edges with a 10X loupe. Look for a bright line just at the cutting edge. You may have to carefully and evenly stone the reamer at its original clearance angles. If you are careful this can be done. Some old timers sort of refreshed a reamer by dragging a HSS tool down the top edge of each reamer flute,NOT down the outside edge of the reamer flutes,but ON TOP of the flutes. This can raise a very small burr that will ream several more nice holes. You have to bear down,and not cut metal off the reamer when you do this. Sort of like burnishing a wood scraper,but on a smaller scale.

I advise you to first try stoning the edges,but be sure you are following the original clearance angles of the cutting edges. If you want to go the burnishing route,try using the round end of a smallish endmill as a burnisher. Grind off the radius if it is too big to let the cylindrical edge engage the top of the reamer's cutting edges.

Black_Moons
08-13-2009, 01:49 AM
If its a hand reamer, it might just be how it works. When I hand ream large holes with my tapered reamer for enlargeing holes, the deeper the hole the finer the chips because of less force on the cutting flutes, eventualy all I end up taking off is powder if the hole is deep enough. (can't provide enough force by hand)

Steve Steven
08-13-2009, 07:57 AM
Thanks for the replys, guys.

gwilson, I am doing this by hand. As a matter of fact, it is on the lathe (a Colchester (English) lathe), to pin the compound at a particular angle that we often need to repeat. I would think that a lathe like that, would have had very good metal used in its construction. I had no problem drilling it, the first hole was a bit slow going through, but I was going 1.3 inches deep.

I will get a magnifing glass and take a look, I suspect you are right and the reamer is the problem.

Loose Nut, Black Moons, yes, I am getting a fine black powder. The reamer is small, and I am pushing it down VERY hard, cutting 4 to 6 turns, then removing. Get mabye .005 depth increase, if any. Sometimes I don't get any depth increase.

I would have thought it would have cut better than that.

I'll keep working on it.

Steve

Glenn Wegman
08-13-2009, 08:44 AM
The reamer is from MSC, an import.


Hmmm.........

I don't like reamers, but for tapers they are pretty much a necessity, so I always buy the name brand more expensive ones as there is a difference!

Watch you don't break it off in the bore:mad:

J Tiers
08-13-2009, 09:01 AM
+1 for black moons' idea.

if you need to go deeper, you may need to step-drill a bit deeper if you want to get done any time soon.

The initial reaming is just taking off the edges of the 'steps"...... after a while you are cutting all along the length of every flute, and the cutting gets slow.

A regular reamer never has that problem, because it cuts at the front end, either on the bevel, or on the lead-in taper, depending on type. No matter how deep, the area cutting is always the same.

Black_Moons
08-13-2009, 09:35 AM
Maybe its faster to make a shorter pin :) or make a pin with a fancy knob on it for easy removal :)
PS: How do you plan to remove swaff that WILL get into the hole? (Or do you plan to have a cap for the hole?)

DR
08-13-2009, 11:12 AM
If the reamer is a cheapo (not much to lose) a trick that is sometimes worth trying is to grind serrations on alternate flutes. Like, if it's a four fluter, grind two of the opposing flutes. This allows easier bite into the material. The un-serrated flutes maintain a smooth finish.

Same modification works well with end mills. A finishing end mill can be turned into a semi-rougher.

Steve Steven
08-13-2009, 03:01 PM
Black Moon,
I will have a plug. The pin will be threaded for a nut to aid in removing it.

Good idea, DR, I may try that.

Steve

Steve Steven
08-13-2009, 08:38 PM
Well,
Tonight I stoned the edge of the reamer flutes. I put the stone against the radial side of the cutting edge, and stroked it several times each flute.

When I tried it, it cut well, got .050" depth increase after only 5 or 6 turns of the reamer.

Alls well that ends well!!

Steve

gwilson
08-13-2009, 10:57 PM
Well,you can mail me 50 cents!!!