View Full Version : My Shop Made Boaring Bars

02-03-2010, 02:37 PM
Since the other thread has gotten so long I thought I would start these here. Actually made these several years ago when I found a real nice Bridgeport boaring head that didn't have any bars with it.
So I made a couple out of 3/8" round. Both have a neutral rake but each one has a different insert angle. I wanted a simple bar that took an inexpensive easy to find carbide insert, and this is what I came up with. They worked out so well that I made one for my lathe as well.
Since none of these bars are hardened I made a small brass half round plug shown inside the boaring head hole, This keeps the set screw from chewing up the bar.



02-03-2010, 06:33 PM
Very nice work indeed.

02-03-2010, 06:37 PM
Very nice! What material did you use? It looks like the largest one was cold-rolled but you got a fantastic finish. Was that a result of polishing?

I'm not sure what I'm looking at in the bottom picture, though...

02-03-2010, 06:52 PM
Nice work. I need to make some tool holders as well. What would be a suitable material? I have some 4140 I could use. Would it work? I don't want to get involved with heat treating.

02-03-2010, 07:42 PM
Nice work. I need to make some tool holders as well. What would be a suitable material? I have some 4140 I could use. Would it work? I don't want to get involved with heat treating.

Ordinary mild steel will work just fine. Boring bars are hardened so that chips and accidental contact (light contact!) between the work and the bar won't destroy it.

02-03-2010, 08:01 PM
Hi guys, Thanks again for the comments. I don't know what the alloy is, some cold rolled stuff I've had in the shop for years, it machines really nice, no polishing done at all, that is the way they machine. It may be a 12L or some leadloy type steel. I have several lengths of it from 1/4" to 1/2" all is slightly oversize by about .007. I doubt the stuff can be hardened but being as short as they are, about 4" long I have never had a problem with chatter.


02-03-2010, 08:05 PM
Very nice job, how did you taper the back 'seats' for the inserts?
Flatheads? weird, can you really tighten those enough without messing them up? the hex/torx screws in most holders can REALLY be tightened easily without the screwdriver sliping like flathead.

I can't really see what that brass antimarr part is like, could you discribe/photograph it a little better?

02-03-2010, 09:06 PM
When I milled out the pocket for the insert I tapered the sides to match the angle of the insert. I set it up in my rotory table which I mounted vertically on the mill. Haveing a nice pocket for the insert to sit in you really don't have to tighten up the screws super tight. I hate button head screws of that size because you always strip out the hex hole. I think the other reason was at the time the slotted screws were all I could find in 5-40 taper head I think??
All the "anti marr" brass plug is and I like that antimarr, good way to explain it. It's a piece of brass I turned down to fit in the set screw hole in the boaring head and and contoured it to fit the radius of the bar 3/8" It snugs up real tight against the bar and never leaves a mark. Being soft steel without the plug the set screw would gouge up the bar makeing it difficult to remove and adjust. I've also seen some people just drop a small dia. piece of lead shot in the hole to serve the same purpose but it would fall out when I remove the bar.


02-03-2010, 09:53 PM
Ah, yea you kinda have to buy the special 'insert' screws for like $1 each :( for the proper screws.. Or you can use your lathe to put a bevel on normal screws :) little easyer with a collet chuck or block in your 4 jaw chuck.
*thinks, 5C chuck of some kind + workstop + one operation to bevel a head = a dozen beveled head screws per min, Starting from a normal screw that is, not starting from raw metal stock)

how does your brass plug not fall out?

Never had my hex key strip it.. but you do need to use decent screws thats for sure, some chinese screws are off center or oversized and will strip with the proper sized hex key.. Torx on the other hand I would think near impossable to screw up, but im sure some of them could be.

02-04-2010, 03:21 PM
Here are a couple pics of the antimarr plug which I made out of brass.



02-04-2010, 03:30 PM
Beautiful work!

gary hart
02-04-2010, 07:44 PM
Very nice indeed. On my rounduit list. Adding word boring bar cause some people spell it that way and can find it when searching for this good idea.

02-04-2010, 10:44 PM
Heh, heh. A few years back there was an ad in American Machinist IIRC by an offshore machine builder. They were promoting their "boaring mill". Yeah, I lived in a rural area and helped the farmer landlord from time to time. I know what they do to the little pigs that were going to grow up to be boars. Somehow the idea of this large NC machine to de-nut the little things was uproariously funny. :D