Sounds like we used essentially the same process: Spoon shaped roughing reamer, then final reamer, with me feeding the pieces onto the reamer by hand.
I am guessing the design of the reamers largely accounts for our differing experiences. I mean to be fair, by the time I got there they’d had 40+ years to perfect their tools and techniques. Plus they had a former GE engineer in the family, who was also a machinist, designing and producing most of the custom tooling. And, well, they are Germans after all, so rather particular about precision, function, quality, etc.
I didn’t answer Loren’s specific question about cutting vs scraping with spiral reamers because I have not done
that experiment myself.
Get busy man, someone needs to do it!
I would guess that the cutting edge on a spiral reamer would work more like a planing
action and produce a smoother surface, but I haven’t done a side-by-side test of this.
I was surprised to learn from the aforementioned Phil Lowe that a properly prepared and used scraper can produce a finish equal to or even smoother than a well planed surface, hence my curiosity.
The VH final reamers definitely appeared to be scraping, not cutting, and on most woods these reamers left a very smooth finish indeed. Considering that they designed and made these rather complicated reamers in house (who else has reamers that also cut sockets and face the end all in one go?), I figure they settled on the straight fluted reamer design for a reason, since they could have made them any way they wanted to.
Shame we can’t get everyone and their reamers together and try them side by side! That would be fun. Guess I’m a bit of a tool geek for even thinking that.
The reamers I make myself have a scooped out, spoon shaped cross section. I settled on this design because it seems to clear chips the best. I suspect this is why your machinists used this design for the roughing reamers you used.
The difference, though, is that I use this shape reamer for my finish reamer. I originally intended to only use a single reamer, but I became concerned about wearing it out. At about that time I found out that I could buy a 5-blade,
Chinese, HSS, oboe reamer fairly inexpensively on eBay, which had just the right dimensions to work as a roughing reamer for several of the flute designs I was making. So I just bought a couple of those rather than spend a lot of time
making additional reamers myself. The idea being to simply save wear and tear on my carefully constructed finish reamers.
For this reason, I ended up using a 5-blade, 5 fluted, straight reamer for roughing, and a spoon shaped, single bladed (well, two really, but only one cuts for any given direction of rotation) for finishing.
This is not ideal, and is the reverse of the way you described using your reamers. So, I think you are right, this difference in use of reamers probably accounts for the different experiences with clogging.
The multi-bladed roughing reamer clogs much faster than the spoon-shaped one because it is removing more material and has less space in the flutes for the chips to accumulate before they fill up.
Fortunately, I do not have to achieve the efficiencies of a large-scale production operation, so I can get away with this non-ideal way of doing things. For my small-scale, diverse, prototyping operation it works out
quite well, aside from having to extract the roughing reamer periodically to prevent clogging. But that is relatively easy to do when feeding by hand. In an ideal world, I would have people who could
make me inexpensive, high speed steel, spoon-shaped, roughing reamers.
For years, I’ve been buying reamers from Gammons in Manchester, CT*. The cost has been well-worth the experience it gave me. My preferred design has a right-hand cut and left-hand spiral (RHC, LHS). Cobalt-steel costs a little more (and takes a little longer to deliver) but it lasts much longer; for all the trouble and expense, I want it to last longer than HSS. I request TiN coating to reduce friction. Step-drilling relieves some of the wear on the expensive reamers. I know that the simple, homemade reamers can work, but I got tired of fighting with them. When I’m considering a new bore, I prototype it by making a smooth core and molding resin around it.
I use a LeBlond machine lathe because it can develop the torque and it has a large spindle bore so I can put the workpiece deep inside the headstock. For reaming, I have a rotary union at the far left end; a plug in the spindle has a conical seat at the workpiece for a rudimentary seal. Thru the hole in the plug, compressed air drives the chips out of the reamer flutes. In this arrangement, reamer flutes of perhaps 1/8" deep are desirable to maintain pressure differential. Also, with shallow flutes, the core has a larger diameter to resist torsional flexing. Such twisting can ruin the smoothness of a deep hole. I don’t design the reamer around the idea of deep flutes to hold chips; quite the opposite. The spiral can reduce chatter but has no value in removing chips,
Many of my reamers have six flutes, but my latest have 5. With five flutes, the “tooth load” increases, which means that more of the force results in cutting, rather than just overcoming friction. More flutes (more cutting edges) means the tool will stay sharp longer, but the driving force increases. As mentioned, the machinist’s principle is this: if you have more tool engaged in the work, you’re going to need more torque, more horsepower, and you’ll have less control. A metal workpiece doesn’t flex much, but wood does, so the extra force compounds the problem. In the past, I specified reamers ground with “chipbreakers” as on some milling cutters. The point is to increase tooth load, but designing is tricky and the resulting surface is not as smooth. For small and simple reamers, I specify “blank back” which means a six-flute pattern where 4 are cutting edges and 2 flutes are not there (the tool has a smooth arc instead). More affordable and quicker delivery.
Of course, Paul S. is in no position to advise you on acoustic considerations. The standard machine tapers (morse tapers) are of limited use. Paul knows metalworking and can suggest these ideas plus whatever has been successful for others who make woodwinds (bagpipes and clarinets).
Loads of good info here. I primarily try to make whistles but a lot of the same concepts get used. I only use Delrin and not wood (and aluminum but I dont need to drill that). But I have big issues with the drilling part. After drilling only like 2 inches in any chip evacuation goes down the toilet, and it starts getting really hot. Then I haev to drill liek 1/4 in, stop, pull out chips, try to cool it, repeat. Takes literally forever.
And another issue, is I have to use spade bits. Normal spiral bits after drilling in an inch or 2 get so much friction from the sides rubbing that it gets super hot and can stop spinning. Spade bits fix this issue because the area that can rub is much smaller because its a skinny long shaft. Also much cheaper. I find they also give a decent finish. But the fail miserably at chip ejection. I’ve seen videos with special gun drills that use air or somethign to blow chips out. I’m wondering if theres any budget solutions for this. At my level buying custom tools definitely isnt an option.
Gun drills are the solution to your problem, but they might create other problems (set-up and cost). If you make any quantity of flutes or whistles, they are worth the investment and will give you much better results.
Thanks for the reply. You are right, I should just do some research and see if theres a reasonable way for me to get a gun drill setup. My current issues with my tool setup is I have a mix of tools that can do some jobs but not all. I kidna cheaped out. I have a midi wood lathe (which I got first and realized was the wrong tool for most of my work) and a taig micro metal lathe. So I have to base my designs around what my tools can make. No cool internal tuning slides for me haha. So now I just work with metal tubes because I dont need to drill them. And I can at least bore them if its a small piece. But unless I ever pull off making something worth selling its feels kidna bad buying more tools. But it is really tempting, there’s always more tools I could get haha. If I get a gun drill setup I can at least make use of my wood lathe again.
The guy from the reamer company said the spiral flutes also help with chattering. With the work piece held in the chuck, I put a vacuum nozzle in the thru hole, which cleared chips and helped cool the piece and the reamer.
The free-floating work piece makes so much sense to the mechanical engineer in me now. You never clamp a lead screw at both ends to give it a little transverse wiggle room.
Thanks for those ideas, Walt. I might think about getting a new reamer for only that section with fewer flutes. I have felt like the six flutes create a lot of friction without much cutting.
I’ve had a few conversations with Paul and have found him very helpful.
