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Quote:
Originally Posted by Mart
Hi fellas.
I've been testing my boring bar and have a few questions. I would appreciate any advice you can offer. I've set it up on an otherwise scrap block and have been taking some test cuts.
1,I'm boring to suit some used pistons. They are +60s and measure 3.246. What would my target bore be after honing? Is it 1 thou per inch so lets say 3.249?
2, How many thou do you allow for when honing? 1? Or hardly anything?
3, When fitting sleeves, how much do you leave at the bottom of the bore for the sleeve to sit on?
4, When the cutting tool reaches the bottom of the bore, do you then somehow withdraw or remove the tool before bringing the bar back up to the top of the bore? (To save putting a scratch up the bore.)
5, what diameter and thread is used in general for the clamping mechanism? I have made two clamps using 12mm threaded rod. I think it looks pretty strong but wondered what the pukka setups use. Is one clamp normal, or are two used sometimes?
I'm getting closer to actually trying to do this for real so would appreciate any help that can be offered.
Thanks in advance.
Mart.
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Hi Mart, with any deck-mounted bar I would recommend boring the smallest amount of material as possible in one pass. On a +.030" o'bore I would take about .024"/.025" (nominally). For a +.060" o'bore I would consider making 2 passes, etc.!
In order to get an excellent base for the rings to seal you should leave about .005"/.006" to finish hone. We generally leave .006" to hone but we have a power-stroked machine so it's relatively easy for us.
If you're planning on hand-honing (.005".006") to the required size, that much material will be a task!
At the bottom of the bore you want the sleeve to be resting on a "full-round" register, the bar should have some type auto-stop?? Don't worry too much about leaving a "line" from the cutter on the way up, it won't hurt anything!
If I recall, the older deck mounted bar we once used had an "auto-retract" built in?
Thanks, Gary in N.Y.
P.S. We bore all our units on a CNC w/o a block-plate, but we do finish EVERY hole with the block-plate bolted in place. Makes for a "round" hole after the head bolts are installed.