After a couple of days delay due to soccer games and a local engine show, I managed to get back in the shop today, for a few minutes.
The work piece will eventually become a contoured body for the engine which will house the crank and piston rod. This required, what was for me, a bit of a challenging bore cut. The first cut was your typical straight through bored measuring 1.125 in diameter. The outer cut will soon accept a plate with a "oilite" (sintered) bronze bushing and measures 1.8125. Neither were difficult, although the larger diameter was an interrupted cut.
The challenge came in when the third cut was made. The cut had to be centered within the work piece, it would be 15/16 inch (.9375) wide and 1.975 (1 /78) inches in diameter. OH yeah..... it would be made completely in the blind with only a couple of witness marks and the dials to guide me. NOOOOOO Sweat....right?
The delay getting back in the shop gave me time to do some mental machining and by the time I began I felt like I had a fair grip on the procedure. The photo below shows the completed cut.
The recently acquired boring bars offer me the ability to mount HSS cutters at 45° or at 90° and are significantly more rigid than the cheap carbide set I bought so long ago. The added plus of being able to easily adjust the cutter depth was indespensible for this particular job. The huge honking tool holder seems to help dampen vibration a bit.... even if it looks funny.
Yeah... the cutter does look a little odd too. Duclos suggested the strange looking end grind to reduce chatter and it really did make a noticeable difference. The sides also have a tapered cutting edge which made for encountering the side walls of the cavity with very little chatter. The double edge is there because the cutter would be running to corners in both directions of travel. The "cupid bow" end minimized tool contact and further reduced chatter. This is an idea I'll be experimenting with when doing other types of bore cuts.
For those considering doing a Duclos project, be prepared to follow his instructions to the letter. After having taken on this, my second of his tutorials, it has become obvious that he has boiled procedure down to it's essence. He offers up no wasted steps and you skip one at your own peril. He makes things as easy and common sense as they can be made. Case in point....
Since the cut is being made in the blind, he suggested using tape and a couple of witness marks to keep you in control of things. He also takes you step by step while making sure you properly zero the dials, taking into consideration the adjustments to compensate for the tool size. In short, he's been there, done that and doesn't want to abuse a newbie, but he is never condescending about it.
From here the work piece will be transfered back the mill for a couple of steps before it comes back to the lathe for shaping.
There were some concerns about the face plate setup. It proved to be quite stable, however, I was still quite cautious about my proximity to it and the lathe was run no higher than 180 RPM to make sure it all stayed stable. This was my first time using a face plate and I must admit it won't be my last choice anymore. It certainly offers quite a wide range of possible setups. More tools in the arsenal...eh?
Steve
