Boring Olds

[Bob Parker]

I am in the process of building a Paul Breisch Olds. Trying to bore the cylinder. The bore is 1.875 about 5.25 long which requires a long boring bar. How do I eliminate chatter??

 

[chuck foster]

hi bob
you need to make as big of boring bar as you can (diameter wise) and keep the tool over hang as short as possible and as always keep the tool on center.
you will also find that the slower you run the lathe (with in reason) the less chance you will have for tool chatter.

hope this helps and i am sure others will have more ideas to help you.

some pictures of this build would be nice th_wwp

chuck

 

[Jasonb]

As Chuck says a big thick bar will be best, at that bore a bar of 1.5" would be ideal. You may have to get adventurous about how to hold the bar, maybe like this which is a 3/4" bar being used on a 1" liner for a IHC vertical.

If you have the height you could also mount it on the lathe cross slide and use a between centres boring bar which eliminates flex.

 

[MachineTom]

If you can hold it I have a 1" x 12 TPG insert bar to loan. It is a Kennametal bar it is round with flats, so it can be bed mounted. Let me know.

 

[Bob Parker]

Thanks for the replys. I quess I will just take very small cuts and hope once I get past the chatter marks it smoths out. Am using a 5/8 bar not very ridigit.

 

[steamer]

I don't know...once it starts chattering , it's hard to take it back out without a set up change. You really should get a bigger boring bar I think.

Dave

 

[rake60]

I've chattered up many critical fits in my career.
Sometimes it was my fault, sometimes it was just the material.
Once the surface finish is chattered, that chatter will repeat.

In my early days, I asked an old salt machinist for help and was horrified
when he took a triangle file and scraped shallow grooves in my almost finished fit.
Those grooves were just enough to break the chatter cycle and my fussy fit was saved.

A light cut with a very sharp tool with a quick feed will also break that chatter cycle.
It will sound awful and look like a thread gone wrong, but it works!

After the finish is roughed up, a light cut with that same very sharp tool will bring the
fit to an acceptable finish that can be honed or polished to the finish size.

Rick

 

[chuck foster]

thanks rick...........one more useful tid bit to remember :bow:

i use to just scrap the part and start over :-\

chuck

 

[rake60]

thanks rick...........one more useful tid bit to remember :bow:

i use to just scrap the part and start over :-\

chuck

No part is EVER scraped!

If that were true there would be no need for machinists.
We'd just throw it away and order a new one from........ where ever they come from.

Rick

 

[Maryak]

No part is EVER scraped!

Many are scraped......................few are scrapped. :-*

Best Regards
Bob

 

[Herbiev]

Old crowbars or jackhammer tools can be transformed into sturdy tool holders

 

[rklopp]

You need a steel boring bar at least 1-1/4" diameter or a carbide/heavy metal bar at least 3/4" diameter. That is, unless you bore it boring mill style using a bar supported at both ends. A steel bar has about a 4:1 limit of overhang to its diameter, and a carbide/heavy metal bar has about a 6:1 limit. You can tweak beyond that a little, but not much. Keep the cuts deep, the feed high, and the nose radius small. Be sure your tool tip is above center, even after it is bent downward by the cutting forces.

I bored my Breisch Hired Man cylinder boring mill style using a homemade 3/4" bar between centers. I had the bore honed at a commercial shop. I recommend honing or lapping for practically any IC engine bore.

 

[titex]

Bob,
If you decide to use a boring bar then the recommended overhang for a steel bar is 3x the Ø so you might get away with a 40mm Ø steel bar [if you have a lathe large enough to use it] With solid carbide the ratio is anywhere between 5 to 7 x the Ø [it depends if the bar has through coolant or not]
If you are going to use a B/B then use one with positive rake inserts for your last few 0.01,s mm [very low cutting forces with positive rake]
Titex

 

[Bob Parker]

Brought my chattered casting over to a friends shop. He has larger equipment. We were able to bore it on his bridgeport with a right angle head, slow speed, small cuts, sharp tool. It looks good. I also got to use one of his lathes to turn the flywheels. Size does matter.
Bob