I would like to make a 3/4" boring bar with about a 14:1 bore ratio. The purpose of the bar is to bore a 12" deep hole on the lathe into wood. The wood can vary in hardness and species. The hole will also be taperd. The boring will follow a 3/4" drilled hole. The taper will be approximately .014" tpi . With the small dia at 3/4". I can not afford a solid carbide or any kind of devibe bar so it needs to be shop made. My thoughts so far is to start with 7/8" sqaure bar about 17" long. I would taper 13" of it the same taper as my bore. Then drill or slot the end for a piece of high speed steel. My question is what type of steel would give me best results, what type of tool geometry would give best results for long boring and would resist chatter. I usualy grind my tools for wood with lots of pos top rake. Is lots of pos rake more coducive to chatter than say neg or neutral top rake? Any suggestions welcome. Thank you
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looking for advice on shop made deep hole boring bar
- Thread starter legoboy
- Start date
- Replies 73
- Views 10,018
js412000
Cast Iron
- Joined
- Oct 24, 2006
- Location
- pennsylvania
The type of steel does not matter.
All steel alloys have approximately the same stiffness.
All steel alloys have approximately the same stiffness.
IronReb
Stainless
- Joined
- May 26, 2011
- Location
- Shreveport/Louisiana USA
Is there a reason your bore can not be drilled followed with a form tool?
Maybe you could add a length of rod to a 3/4 jobber drill bit then machine a piece of
3/8 flat bar down the edge to get your taper, grind a few degrees relief so you create
a two flute reamer and hone the cutting edges. I would try to use an alloy harder than
mild steel just so it stays sharp longer.
Add a 3/4 pilot on the end to guide it.
I would cobble up a means to drive the reamer with a large T handle to finish up the last bit by
hand so I could turn it nice and slow if it chattered.
Maybe you could add a length of rod to a 3/4 jobber drill bit then machine a piece of
3/8 flat bar down the edge to get your taper, grind a few degrees relief so you create
a two flute reamer and hone the cutting edges. I would try to use an alloy harder than
mild steel just so it stays sharp longer.
Add a 3/4 pilot on the end to guide it.
I would cobble up a means to drive the reamer with a large T handle to finish up the last bit by
hand so I could turn it nice and slow if it chattered.
johnoder
Diamond
- Joined
- Jul 16, 2004
- Location
- Houston, TX USA
A left hand drill ground with that taper and made to cut right hand at small end will fix you right up, having both room for chips and no tendency to pull itself in - assuming you rotate work to make right hand cut
Too short, but maybe the right size to start with assuming taper spec is on diameter
http://www.ebay.com/itm/Morse-Taper...-1-pc-15-16-/291513049487?hash=item43df88218f
Too short, but maybe the right size to start with assuming taper spec is on diameter
http://www.ebay.com/itm/Morse-Taper...-1-pc-15-16-/291513049487?hash=item43df88218f
Krovvax
Hot Rolled
- Joined
- Mar 5, 2012
- Location
- Quebec, Canada
Ive made some custom boring bar at school with 8620 that we heat treat. We drill a 1/2 hole 3/4 of the length from the back of the bore. Took the box of old used scrap carbide insert that we break in little piece and fill the hole with them. We also fill the hole with oil and plug the end with a npt plug. This mix allow to get rid of alot od chatter and harmonic that can be create. It work wondefull on steel so it should work like a charm in wood.
Thank you for the responses, I had thought of a purpose made tapered reamer but the cost of having a custom made reamer is a little out of my price range. I have the setup for cuting long tapers so was leaning towards boring the hole. This is a process I will do possibly hundreds of times so being able to sharpen the cutting edge or change an insert would be ideal. Posts on the same line as krovvax is what I was looking for. Specificaly what type of tool geometry should the cutting edge have. I know that minimizing tool nose radius is important but not sure of what type of rake angles are prefered when you are trying to minimize chatter. For example I have had experience where a dull insert seams to work better then a new one for chatter. I will replace a. Insert on a boring bar and all of a sudden I am getting chatter when previously there wasnt any.
Krovvax
Hot Rolled
- Joined
- Mar 5, 2012
- Location
- Quebec, Canada
The bar i talk about was holder brazed tool and hss toolbit. For wood i would go with hss toolbit they are going to give you the best cutting action over a insert. Insert thay are not ground/polish and not sharp and have a flat on them making them less free cutting and giving you a harder time fightint chatter. A toolbit perfectly ground will last a long long time and will be free cutting.
thermite
Diamond
- Joined
- Sep 21, 2011
If I had to do 'many' or these, and in a variety of woods..
I would want to Speed-Bore a straight hole - NOT on the lathe - then do the taper with a common-enough-to-be-cheap carbide wood router bit at the end of a long-shaft internal TP grinder. Or salvaged TP grinder spindle driven BY a wood router head.
As I do NOT 'have' to do them, I'd simply make inserts to be placed into a larger straight-sided bore.
Life is too DAMNED short to spend it single-point precision boring knotty-pine or such.
WTH - I don't personally even regard aluminium as having sufficient thermal 'sit STILL, Dammit!' goodness to mess with a bore that deep to any degree of precision.
Wood adds moisture-content dynamics as well a variations in other characteristics to that challenge. Even if you ''get it right', over time, that tapered bore could be as unpredictable as Hillary's email situation, so....
Where's the gain over a 'tree nail' tapered reamer? And why chase it?
Bill
Onepass
Hot Rolled
- Joined
- Jun 2, 2014
- Location
- Kansas City
Does it have to be flat bottomed on the bore? If not, you might consider putting a negative lead on the tool bit if chatter becomes an issue. I'd think chip evacuating would be a major concern. So anything you could do to eliminate that would be for the good!
Or maybe you could find a really big-assed bridge reamer.
Just a wild thought, could you use a carbide burr on a small diameter ID grinder spindle?
You might also consider turning several tapered pins of the same contour and taping these to small trees. After the tree grows around the special pin , just cut that section out and turn O D easy-peasy!!
Or maybe you could find a really big-assed bridge reamer.
Just a wild thought, could you use a carbide burr on a small diameter ID grinder spindle?
You might also consider turning several tapered pins of the same contour and taping these to small trees. After the tree grows around the special pin , just cut that section out and turn O D easy-peasy!!
Forrest Addy
Diamond
- Joined
- Dec 20, 2000
- Location
- Bremerton WA USA
Boring the lumen of a woodwind instrument? The bores may not have a linear taper. Usually they are drilled and finished with a contoured D reamer.
The practitioners of these arts can be very secretive.
The practitioners of these arts can be very secretive.
The wood which will be used is all mostly exotic hard woods and is all dry to 6% moisture content. The wood to be bored is already in dowel form and is about 1 1/8" in dia. After the hole is finished another dowel with matching taper is glued inside of it. So the original piece ends up being more of a thick one piece veneer. So movement is not a big issue. I do not object to using a reamer but my issue is keeping it sharp and with that much surface area cutting heat could reap havoc and possibly crack the dowel. As well I have not seen anyone who makes that long of a reamer so it would have to be custom made. As far as live tooling I have thought of that but going that deep in such a small dia hole would make that prospect very challenging to rig up. Currently I am using a straight bore and using a gun drill. The tapered bore is where I want to go for various reasons. And the finished piece is tapered as well so the internal taper would match the external.
Orange Vise
Titanium
- Joined
- Feb 10, 2012
- Location
- California
I would just grind a modified D-bit from a 12" length of 3/4" M2 round bar. I don't think chatter is going to be an issue in wood, and you can always use a gap filling adhesive like epoxy.
thermite
Diamond
- Joined
- Sep 21, 2011
I submit that cutting-tool methodology quite aside, you are overly optimistic about the social mores of woods.
Another 50 years of observation, assisted with the odd museum visit, tempered by the knowledge that an ancient and carefully preserved item is perhaps the only one of multiple thousands of originals that has NOT yet cracked... wagon wheels come to mind as much as table legs or music boxes - and you'll know what I mean.
BTW - 'the ancients' were not too proud to cheat, either. Had all sorts of hidden kerfs, sealers, glues and resilient fillers for wherever they made good sense.
"Married' a few things 'green', too, now and again - then controlled the drying after assembly.
6% moisture content (you trust) means no more in the grand scheme of things than '25% less Sodium' does on a bag of 'tater chips.
Bill
stephen thomas
Diamond
- Joined
- Jun 3, 2001
I second the idea of modifying a bridge or car reamer. I have done so for shorter lengths, (up to 7" or so IIRC). They can often be found as scrap, and then just modified on a T & C grinder to whatever taper is desired.
Less ambitious but perfectly adequate is the D reamer, more or less used for centuries. Long discussion about them somewhere on PM recently.
If you want to hew to boring
, I might make the bar with a carbide or tantung wood cutting insert. They are quite sharp, enough clearance angle to set at any sensible rake, and have 4 edges to index. I use a lot of them to make shaper cutter heads, but they should be good on a bar, too. For maximum rigidity, I agree with your idea to taper the bar. Sounds like you at least have a long enough taper attachment to bore 12", so the bar should be easy as well or could be done with TS offset.
smt
Less ambitious but perfectly adequate is the D reamer, more or less used for centuries. Long discussion about them somewhere on PM recently.
If you want to hew to boring
, I might make the bar with a carbide or tantung wood cutting insert. They are quite sharp, enough clearance angle to set at any sensible rake, and have 4 edges to index. I use a lot of them to make shaper cutter heads, but they should be good on a bar, too. For maximum rigidity, I agree with your idea to taper the bar. Sounds like you at least have a long enough taper attachment to bore 12", so the bar should be easy as well or could be done with TS offset.smt
Can you explain the term D-bit?
thermite
Diamond
- Joined
- Sep 21, 2011
Paint it with the mouse, RMB depress, select 'Search Google for..."
Second hit has images, third hit is a collection of threads about them right here on PM.
Dead-easy to make, just never the fastest game in-play vs a multi-flute reamer.
Advantage to sawdusty things is that a modest air-blast can clear the chips AND keep the tool (relatively) cooler.
Common Tungsten Carbide laminate trimmer, guide-bearing pulled, used as 'live' tooling in the form of a TP grinder or router head will do the do a lot faster for repeat work, though.
The cutting edge(s) take SO very, very, many tiny 'nibbles' per second there is near-zero deflection stress on it.
Bill
I am not familiar with a bridge or car reamer as well as d reamer. I am open to the idea of a reamer but I dont think it will be very affordable. I will.have to locate a suitable reamer candidate then have it custom ground and then get it sharpened often enough. A reamer was initialy my first thought but decided that a boring bar I could quite easily build, it just needs to resist vibrating. I did build a quick 5/8 bar with a HS tool in the end and it works great to about 7" out but beyond that it starts to.osilate up.and down somthing fierce. So was hoping with a little advice I could engineer a better bar.I second the idea of modifying a bridge or car reamer. I have done so for shor
o 7" or so IIRC). They can often be found as scrap, and then just modified on a T & C grinder to whatever taper is desired.
Less ambitious but perfectly adequate is the D reamer, more or less used for centuries. Long discussion about them somewhere on PM recently.
If you want to hew to boring
smt
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