Need boring head recommendations

[Ken from ontario]

It appears to be missing a set screw, but every one I looked at was missing at least one.

IIRC, there should also be a steel bearing ball in there too , I could be wrong but in case you need one, they are easy to find, you can get 100 in a package.

 

[mikey]

IIRC, there should also be a steel bearing ball in there too , I could be wrong but in case you need one, they are easy to find, you can get 100 in a package.

Ken, there are ball bearings under the gib set screws. There are none under the set screws that hold the boring bars, and that is what he is missing.

 

[rwm]

It's not "on center" that would be the concern in my mind, it would be "tilt". So while the shank may run "true" to the quill, the head may not be running true to the shank.

So if you're using it like a fly cutter, it may cut on the forward sweep and not on the rear sweep. For boring, you may be able to compensate for the "less than true" cut, but I believe you'd have to measure the bore because graduations on the tool may (or may not) be accurate.
sonally, I'd much prefer a tool that has a grub screw, lock pin or some other locking mechanism rather than to weld the threaded shank to the head.......YMMV.

Sorry but this is not correct. Tilt of the head will not affect its use. The tool will always revolve around the axis of the spindle. If the mill is in tram it will work fine. I agree it IS likely deformed by welding.

 

[great white]

Sorry but this is not correct. Tilt of the head will not affect its use. The tool will always revolve around the axis of the spindle. If the mill is in tram it will work fine. I agree it IS likely deformed by welding.

Maybe a quite and dirty diagram will help expalin what I'm seeing in my mind:



That's obviously an exaggerated depiction, but it gets the idea across. I fail to see how the first picture would cut the way you would expect the second to. The shaft still spins true to the quill, but the head (being pulled/warped/twisted/etc) won't follow the same arc when cutting....which I can see causing all sorts of problems.

I could very well be wrong, but I'm just not seeing it.....

 

[rwm]

The head on the left will still inscribe a circle that is perpendicular to the axis of rotation and co-planar to the mill table regardless of the angle.
As an example, take an indicator holder clamped in the mill spindle with indicator at the far end. It doesn't matter how many joints or what angles the bars are set at. The indicator still runs in a plane co-planar with the table. Yes? That is how you check tram.

There IS an error that would be introduced by a warped head. The dovetail not being perpendicular to the axis of rotation will cause a very small cosine error in the movement of the tool when you increment the screw. This would be minimal.

 

[ARC-170]

I saw that head. Looks pretty good except its missing one of the bar holding screws. The replacement is a 5/16-24 Z 3/8" long fine thread socket set screw with a knurled cup point. You can get them on Amazon.

I agree with @ttabbal. Borite cobalt bars are one of the best bars but they are no longer in business and finding a full set is going to be difficult and expensive. An alternative I would jump on is this one from KBC. Might seem pricey but they are 8% cobalt and will last your lifetime if cared for. They will also work really well at the speeds you are likely to use.

REPLACEMENT SCREWS
I thought it was the best of the bunch, plus I got a good offer. The other ones had what appears to be rust. They were ALL missing screws.

I was planning on using set screws from the local hardware store. Is there any reason to use the special ones you mention above (thanks for the spec, by the way!). Does the knurled end hold the boring bar better? I have to buy 20, but only need 3 (I'll just replace them all). I may have to post the extra for sale here! Ha!

BORING BARS
Thanks for the link. Would I need to sharpen/grind the cobalt ones at all, and is it easy to do if I need to grind them if I break/chip a bit for some reason? I was going to order a set of 1/2" shank ones from LMS, since they are local to me and I have a set of 3/4" shank ones that work fine.

 

[ARC-170]

Finding a good quality boring head in my non professional hobbyist view is one of the easiest task nowadays, just look around on eBay as I'm sure where you found that one in your post, there are plenty of Criterion BHs for sale, I bought mine from a good seller "bratex"( and he accepts reasonable offers) ,it is a smaller S 1.1/2 with a straight 5/8" shaft, I would not trust a tool like a boring head if it was welded unless I know the story behind it or can verify it is still 100% functional.

I was watching 3 Criterion DBL-202 boring heads this seller had for $250 + $15 for shipping. He offered to sell them for $187.50. I already accepted the other offer, but thought I'd mention this for anyone following along who wanted to know what a "reasonable" offer was for this seller.

 

[mikey]

REPLACEMENT SCREWS
Does the knurled end hold the boring bar better? I have to buy 20, but only need 3 (I'll just replace them all). I may have to post the extra for sale here! Ha!

Yeah, the knurled end holds the boring bar solidly. This is the set screw that Criterion uses.

BORING BARS
Thanks for the link. Would I need to sharpen/grind the cobalt ones at all, and is it easy to do if I need to grind them if I break/chip a bit for some reason? I was going to order a set of 1/2" shank ones from LMS, since they are local to me and I have a set of 3/4" shank ones that work fine.

These cobalt bars cut fast, accurately and finish really well in most materials we hobby guys encounter. My sets are from Borite and are over 25 years old and they look and work like new. To sharpen them, simply hone the top and end on a fine stone when needed. You just need to get those flat faces flat.

If it was me, I would go for the KBC set but you should buy what you think is best. Just stay away from inserted carbide unless you're cutting something really hard. Inserted carbide bars need speed and speed and boring heads do not play well together. Trust me; a cobalt bar will cut more accurately and finish way better than carbide.

 

[ARC-170]

Ken, there are ball bearings under the gib set screws. There are none under the set screws that hold the boring bars, and that is what he is missing.

I received the boring head today. I cleaned it all up and put a few drops of 3 in 1 oil on the screw and dovetail.

There are no ball bearings under the set screws. Looks like they take 1/8" diameter balls?

There were actually two set screws missing. The one that was there was not the knurled cup point. I bought 25 on Amazon. McMaster-Carr had 50 for about the same price, but I was able to use a gift card balance so it was actually cheaper for me on Amazon.

 

[ARC-170]

Yeah, the knurled end holds the boring bar solidly. This is the set screw that Criterion uses.


These cobalt bars cut fast, accurately and finish really well in most materials we hobby guys encounter. My sets are from Borite and are over 25 years old and they look and work like new. To sharpen them, simply hone the top and end on a fine stone when needed. You just need to get those flat faces flat.

If it was me, I would go for the KBC set but you should buy what you think is best. Just stay away from inserted carbide unless you're cutting something really hard. Inserted carbide bars need speed and speed and boring heads do not play well together. Trust me; a cobalt bar will cut more accurately and finish way better than carbide.

I bought the KBC set. I hope they send you a thank you note! I've decided that good cutters are gold. I have too many issues with cheap cutters.