# School Me On Boring Bars And Holders



## great white (Oct 4, 2015)

My setup is an old atlas TH42. Simple, easy to use and just generally gets the job done well for me. It has an AXA QCTP I put on last year and that helped immeasurably.

I only do simple work on it, mostly motorcycle parts and bits. IE: spacers, axles, bushes, small brackets, etc. I have an atlas milling attachment (thanks again Ulmadoc, it gets lots of use!) that lets me do small brackets and some facing operations.

I find myself at a point where I think a boring bars might be a useful addition to the tool shelf.

I would be doing bores probably no bigger than a few inches at best. Usually under an inch I would think (motorcycle parts: axle spacers, bushes, etc).

I need a bar holder for a QCTP obviously, but there seems to be all manner of boring bars and sizes.

I'm guessing larger diameters are for deeper and larger bores to resist deflection. But they would also limit the smaller ID they could be used on. 

I'm also not looking to "break the bank" on this and ebay stuff usually will work to the tolerance I need. I have a busy bee locally (I'm in Canada), but their prices are just stupid compared to what I can order off ebay. Their tools all seem to come out of China anyways, so I can't bring myself to pay their stupid mark up on a China tool when I can just order it myself and wait a couple weeks.

I don't screw cut, so internal screw cutting is just not even an option right now. I'm just not good enough, yet.

Most of the bars I've seen are carbide inserts, although I have seen a few HSS ones. Most of my cutting tools are HSS as I am trying to force myself to learn how to grind cutters. HSS is fine for 99.9% of the work I do anyways (typically Al or mild steel).

Can someone recommend a good "all around" size for a boring bar that typically does light work?

Once I have an idea on what bar size will cover my use, I can start hunting for a holder....


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## Bill Gruby (Oct 4, 2015)

I use a 3/4 inch holder in my QCTP. I have bored holes to well over 4 inch diameter with it. To use smaller diameter bars I made a set of split bushings for the holder. My bars go from 4 inches to 10 inches in length. That's the short answer my friend, hope it helps?

 "Billy G"


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## great white (Oct 4, 2015)

Bill Gruby said:


> I use a 3/4 inch holder in my QCTP. I have bored holes to well over 4 inch diameter with it. To use smaller diameter bars I made a set of split bushings for the holder. My bars go from 4 inches to 10 inches in length. That's the short answer my friend, hope it helps?
> 
> "Billy G"


Ah, I never thought about bushing a larger tool holder to use smaller bars!

That opens the options up quite a bit.

Thanks!


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## Cobra (Oct 4, 2015)

One of the cheapest and quickest solutions is the brazed carbide sets for use in a boring head. They'd can be had in shank diameters from 3/8 to 3/4 for very reasonable prices. In each set you have a number of diameters and lengths. 
Either buy for your Utica change tooling or build bushings for fit them.


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## Bill Gruby (Oct 4, 2015)

With the boring head comes a problem. That problem is depth of cut without chatter. A good idea yes, but a 3/4 inch bar going 6 inches deep is a better solution. If you are only doing short depth holes the boring head will suffice.

 "Billy G"


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## Cobra (Oct 4, 2015)

I agree Bill.  The suggestion was for an easy way to get started.  Once you actually have a need for a longer bar, then buy it.
Don't want to suggest buying a bunch of tooling just on spec that it might someday be needed.


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## Bill Gruby (Oct 4, 2015)

What I strived for with my answer was not to short change your idea as it really was a good one. I sought to inform the OP of the negative side of the idea, that way he is better informed  on which path to take. I meant no disrespect in my post. My apology if any was taken.

 "Billy G"


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## Cobra (Oct 4, 2015)

None taken at all Bill.  I should have expanded on the post.
I just looked again. Were you thinking of using the entire boring head in the tail stock?
Might be a great idea but I was just using the bars from the head in the QC tooling.


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## coolidge (Oct 4, 2015)

My brother likes carbide boring bars for rigidity, he cruises ebay for these and often picks them up for a fraction of new price.


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## Bill Gruby (Oct 4, 2015)

If you have the tailstock taper on the boring head you can use the head in the tailstock. This allows for short depth holes. Yes that is what I was referring to.

 "Billy G"


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## Cobra (Oct 4, 2015)

I would have to change the adapter from the R8 that is used in the mill.
I just use either the 3/8 or 3/4 carbide tipped bars in the boring bar attachment that came with the quick change set.
3/4 is easy, the 3/8 I had to make up a split sleeve to adapt to the 3/4 hole.


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## mzayd3 (Oct 4, 2015)

I have made some split bushings as well.  For the most part though, I use my other QCTP toolholders that have a vee grove along the bottom of the holder.  The set screws lock the boring bar into the grove.


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## REdington (Oct 4, 2015)

great white said:


> I would be doing bores probably no bigger than a few inches at best. Usually under an inch I would think (motorcycle parts: axle spacers, bushes, etc).
> 
> .



  For anything 500" and under, I use Micro boring bars.  They a carbide and a little expensive, but work well.  The ID on them is easy to identify.
For example, a "BB 1601000" 
 The "BB" a boring bar  
 160 id the minimum diameter 
 1000 is the depth of bore.

 I have also ground some out of HHS for diameter as small as .060.  

 For larger holes I have a 1/2"  and 3/4" boring bars that uses HHS bits.

Rodney


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## mikey (Oct 4, 2015)

In my opinion, the simplest, cheapest way to a good holder is to buy or make an Aloris AXA 4D boring bar holder and use reducing sleeves with split bushings in it to accommodate any bar up to 3/4" dia. The 4D is 3" long, which is exactly the length required to hold a 3/4" bar securely. This type of holder, and any sleeve you put in it, will completely surround your bar and hold it solidly, thereby reducing the potential for chatter. Any other boring bar holder that locks down directly on the bar itself with screws will have more potential for chatter and may mar your bar. 

When making sleeves for smaller bars it is wise to ream the central hole with a sharp reamer and cut it in a single pass to get the finest finish you can get; this also reduces potential for chatter in the bore.


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## T Bredehoft (Oct 4, 2015)

This as been mentioned before, but the cheap( read inexpensive) eBay boring bar sets, (available without the adjustable head) need to be touched up before use.  The ones I've used were not relieved enough behind the cutting edge, nor were they relieved away from the cutting edge (they were square when viewed from above)  A diamond wheel is ideal, but I've found a diamond coated disc from Dremel mounted in a drill press will do an excellent, if slow job. Clamp the tool in a small vice and slide it around under the spinning disc.


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## David VanNorman (Oct 4, 2015)

If you are starting and you grind your high speed cutters you can get a set of bars that use high speed. .If you have a AXA Qctp one  of the holders has a grove that will hold a round bar. Play with that till you get the hang of it.


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## Bill C. (Oct 4, 2015)

Deeper you bore the hole the larger diameter bar is needed. Chatter due to deflection because the length needed to bore the hole is always a challenge. A smaller diameter with a sharp bit could be used but the feed and depth of cut would have to be very light.  If after a cut there is a scratch on the inside wall of the bore then there is still a lot of tool pressure. 

You could take a practice piece of stock and test the amount of tool pressure by re-cutting the bore without making any adjustment to the settings. Sorry but I can't remember what the ratio is, if it one or two more passes before the signs of deflection is removed.  I was using a heavy boring bar on a turret lathe and asked a senior toolmaker why I was getting a scratch on my finish bore.  One would think a two inch diameter boring bar there would be much deflection.


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## Paul in OKC (Oct 5, 2015)

Those bars (the carbide tipped ones) can do a good job, within limits. Keep in mind "normal" length ratio for a steel bar is 4 to 1.  That being said, the larger the bar the better for stability sake. Sounds like the 3/4 bar would do most of what you have.  You will have deflection on just about any bar you use. When taking final pass, either touch off the bore and dial from there, or take a shallow 'spring' pass at the last setting and measure for the last cut.


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## T Bredehoft (Oct 5, 2015)

A good trick on finishing a bore without a scratch, feed out after you feed in.  You've gotta be comfortable with doing this, though, maybe do it on the last two passes, so you take into account the metal you remove on the feed-out pass.


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## churchjw (Oct 5, 2015)

I use the boring head bars often, but as was mentioned they do need some work to cut well.  I also picked up a carbide bar with inserts at a flea market a while back for very cheep and it works great. It is my little workhorse because it will go through about anything with very little chatter.  In general I prefer HSS over carbide so I have a few home made bars that use HSS blanks.  The only trick to making them the way I did is I broached the holes for the HSS cutters.  If you want I can post some pictures of the ones I have.  They are nothing special but they cut good and are cheap to make if you have access to the right size broach or you make a broach. 

Jeff


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## T Bredehoft (Oct 5, 2015)

churchjw said:


> or you could make a broach.



Whew. there's a thought.  Could I do it without any kind of controlled grinder?  Hmmm.  If my mill had a controllable Z, in tenths, maybe, but it doesn't.  I've made several boring bars, to hold HS and carbide round tools, they work pretty well.


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## churchjw (Oct 5, 2015)

You could make a passable broach from a lathe tool using just a free hand grinder.  You may need a cut off wheel to get some of the angles.  I guess it depends on how big a press you have and how hard it will push.  There is nothing wrong doing it with a round HSS cutter.  Could be a good use for broken center drills. end mill, or taps.   Would that work?  Never tried to use an old center drill or tap as a lathe tool.  How does the steel compare?


Jeff


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## Wreck™Wreck (Oct 5, 2015)

Use the largest bar that will fit in the bore (and your holders) and leave sufficient chip clearance, packing a bore up with chips rarely works well and will often damage the tool, the part or both.

Inexpensive round bars with a square hole broached through them for holding square HSS blanks with a set screw work well for hobbyist/one off work. The tool may be ground for internal grooving, internal threading and back boring Etc. Buy one that has a 45° hole in one end and a 90° hole in the other, the 45° will allow you to bore the the bottom of a blind hole.


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## Wreck™Wreck (Oct 5, 2015)

churchjw said:


> You could make a passable broach from a lathe tool using just a free hand grinder.  You may need a cut off wheel to get some of the angles.  I guess it depends on how big a press you have and how hard it will push.  There is nothing wrong doing it with a round HSS cutter.  Could be a good use for broken center drills. end mill, or taps.   Would that work?  Never tried to use an old center drill or tap as a lathe tool.  How does the steel compare?
> 
> 
> Jeff


High speed steel taps work fine in a lathe as turning tools. Have used them in square hole boring bars in the past when the (Job Must Be Finished Today) and I had nothing else.


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## markknx (Oct 5, 2015)

Great White as you see it can be quite an open subject when it comes to tooling. And I do not feel any of the above are wrong answers. You gave dia. What about how deep/long the bore is. If they are short then the sets for a boring head are OK. I think the range is like 1"-3" deep maybe 4". if you think you will be doing deeper bores then I would suggest longer bars. I would only go with Carbide if you need carbide.

If I nay be a bit forward, Learn to grind your own bits. you will see it is not hard to get good results, and it is much cheaper. A well ground bit kept honed will last a long time. You get many option of size and shape. You can even make boring tools.  I a novice have even used a piece of drill rod  to make a boring bit in a pinch. (took a few more spring cuts but it got me by.) It also opens up the repurposing of old broken drill bits, endmills, and the like. Could be if you are not boring deep you already have a few boring bars that are hiding in old broken tools.

Check you tube, Abomb, Mrpete, tom lipton and many others have good videos onhand grinding bits. On this forum there is a thread on it right now and it has a link to two vids on grinding. here

http://www.hobby-machinist.com/threads/turning-tool-and-facing-tool-questions.36687/page-10

I know you wanted to know about boring bars, but you did say you wanted to keep it low cost.

Mark.


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## dave2176 (Oct 5, 2015)

I use carbide insert holders almost exclusively. But I do have this set from Enco.
	

		
			
		

		
	



	

		
			
		

		
	
 (3/8, 1/2, 5/8, 3/4, 1.0) #378-4000 was in hot deals plus 20% and free shipping it cost $20.76. One end is angled, the other 90*. Add a few 1/8 and 3/16" HSS tool bits and it serves well.
Dave


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## atlas ten (Oct 5, 2015)

You can try making them. I got couple home made ones with my lathe purchase.  Previous owner welded hss chunk to mild steel square stock. Then ground to boring profile.  I have made couple smaller also from broken off pieces hss.  Do keep them small ones. Not sure how well they work but worth a try.
I did upgrade to qctp shortly after. Will use 3/4" bar with 1/4" hss 
Jack


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