How Do You Efficiently Grind A Hss Boring Bar

GarageGuy said:
rex21 is spot on. It doesn't need to be any more complicated than that. Especially for cutting bronze.

GG
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I cut CRS with a bit like that. The longest time will be grinding the clearance on the bottom. Specially by hand and a bench grinder.
 
mzayd3 said:
What about drilling just slightly undersized and boring it out with a 5/16" endmill? I have used this setup for larger bores.
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I use endmills all the time as boring bars for shallow holes. Works great. Just set up so one cutting point is in the right position to make the cut.
 
Tom, I suppose all of this comes down to what you're boring. You mentioned this is a bronze casting so I assume this means you have one shot at it or you'll need a new kit. The bore is only 1-7/32" deep but for a 1/4" steel bar that is relatively deep. You don't mention if this is a precision bore or just a clearance hole, and you didn't tell us if this has a flat bottom. If your tolerances are large then no problem but if your tolerances are in the low thousandths or in the tenths then that does make a difference. You also didn't mention what kind of finish you need.

All of these things have a bearing on what kind of boring bar you use and how you use it. Perhaps if you gave us this information it would allow us to be more helpful.
 
Dear All,

I found the solution in my toolbox! I forgot that I have a boring bar that has a minimum hole size of 3/8" and a max depth of 1.25". Thus, there is no need to make a boring bar from 1/4" sq HHS stock, which would probably not work anyway (given past experience).

This is the project I am doing:
STEAM-ENGINE-7.jpg

It is a twin cylinder version of their #3 engine, which I did previously. The #3 engine build largely failed, as it won't run. This is due to two factors: 1) I am a beginner, having started machining in March 2015, and 2) my lathe had some problems. I am hoping this goes better!

Thank you all for your help. The information provided will be useful to me and others.

Cheers,

Tom

P.S. I am thinking about starting a project blog on the PM #7 engine (above). Would this be of interest to folks on this site? I don't see many model engine builds in the projects forum.

STEAM-ENGINE-7.jpg
 
I am sure folks would enjoy following your engine build. I would not worry about an engine not working right off the bat. I know folks who have had non working engine builds for years and then voila, the light goes on, they find the problem and a happy outcome.

cheers
michael
 
+1 on the share the build with us. It would be nice to see one done. In fact I am doing the picture myself. It will take me a few months as I only get a small amount of time with it at once. Also have to purchase a bunch of the taps and dies. for it as I did not have any that small.
 
For those who are interested, I have started a PMR #7 steam engine model build log here.

Thanks,

Tom
 
atunguyd, That is exactly what I was looking for. Thank you!

Tom
 
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