Machining an Inside Taper

[RayG]

Hi All,

I'm looking at making some socket chisels, where part of the job is to machine the inside of the taper, it's too small for a boring bar.

I'm thinking of making a sort of custom step drill, maybe with a bit of a spiral for chip removal, and then finishing with a reamer.

Is there a better way? How do manufacturers bore inside small morse tapers?

Regards
Ray

[Bryan]

Ray, there was talk recently on another forum about morse taper drill bits, but few had heard of them so they clearly didn't catch on. I'm going to guess wildly say step drill with several bits and ream - rough and finish. I guess a custom step drill would be worth it for production. What size do you need? I've bored MT2 but it's a pain.

Edit: If you make a special drill can we watch? :wink:

[RayG]

Hi Bryan,

I could make it whatever taper I like I guess, but if I want to make it interchangeable with Lie Neilsen socket chisels, it would have to be a custom taper, probably closer to MT1 than anything else.

One other idea is to set up the rotary table on the mill and tilt the rotary table over at the taper angle with a small diameter cutter and use the rotary table to control the cut.

Regards
Ray

[Michael G]

Can you post a sketch with a couple of dimensions? I have a small Kennametal boring bar that will start in a 10mm hole from memory, so a small taper is possible, especially if short.
I have a taper turning set up on the lathe too that makes these things easier than cranking a compound slide handle.

Michael

[harty69]

Ray if you had a cnc mill you could mill a tapered pocket with a ballnose endmill take about 5min any
taper you like:2tsup:

cheers
Harty

[RayG]

Hi Michael

I will do a proper drawing later tonight, but rough dimensions are tapering from 12mm diameter to 5mm or so diameter over about 30mm.

Here is some idea of what I'm on about.. I've put in a #1 Morse taper for comparison.

http://www.backsaw.net/pics/Misc/SocketChiselTaper.jpg

The quick test with the standard step drill worked fine, and the taper is close to what I need, the lack of a spiral meant that there is no way for the chips to get out.

The part on the right hand side is the start of a new chisel from 3/4" O1 drill rod stock.

Regards
Ray

[RayG]

Ray if you had a cnc mill you could mill a tapered pocket with a ballnose endmill take about 5min any
taper you like:2tsup:

cheers
Harty

Thanks.... :rolleyes: I needed to know that... just a few more little pushes will be all it takes for me to get back to finishing the CNC conversion. :)

Regards
Ray

[Jekyll and Hyde]

One of my usual harebrained ideas here, but could you make up some sort of jig to grind a tapered drill bit or similar on your surface grinder?

[Michael G]

I think for a taper that small, the best plan is to drill out with the step drill and then clean up with a custom made cutter. If you knew someone who could heat treat and has something like some some O1 steel you'd be set.
I'd start by turning up a cone (on a shank) and then off set it in a 4 jaw to put some relief on the side; turn 180 degrees and do the same thing. End result should be something football shaped in cross section (provided we are not talking soccer here...)
Put it in the mill and cut two flutes, heat treat, grind and hone. Should work...

Michael

[Steamwhisperer]

HI Ray,
What about making a micro boring bar. They are ground entirely out of a piece of HSS. I used to make them all the time and of course they have all disappeared over time so I can't even get you a pic but I did read an article on how to make them properly. If you are interested I could locate the article for you.

Phil

[AndrewOC]

C'mon Ray!
forge em like they should be!
;)
AndrewOC

[RayG]

Hi Phil,

I've been googling for micro boring bar, but haven't come up with anything, I could grind a cutter from hss with a long tapered shank.. it's going to have to be less than 1/4" wide at the tip..

Do you have a picture?

Michael,
Thanks for the tip, I know where there is a heat treatment furnace... :) I might be able to find some O1 too I think.. :rolleyes:

What's the oval shape about, is that for the cutter relief? I was thinking of just turning a couple of step drills with staggered steps, so I'd drill the small diameter with a normal twist drill, then run the first step drill. Then the second step drill with offset steps, then a tapered reamer to finish.

Hi Jeckyl&Hide
The idea of grinding a taper on a standard 1/2" drill is appealing too, that would give me the twist for chip removal, only problem I see is that the tool would be cutting on edges the full length of the taper, might be a bit tricky.

As Andrew says the traditional method is forging... :)

Regards
Ray

[Bryan]

The idea of grinding a taper on a standard 1/2" drill is appealing too, that would give me the twist for chip removal, only problem I see is that the tool would be cutting on edges the full length of the taper, might be a bit tricky.


That's what the MT drill bits that I saw pics of did, but they had notches. Looked like a cross between a drill and a roughing reamer. Will try and find the thread. I believe the consensus was you would need a decent machine to run them.

Edit: Here's the thread: Learn something new every day. - The Home Shop Machinist (http://bbs.homeshopmachinist.net/showthread.php?t=52251)

[Ropetangler]

As my experience in machining is zilch, this idea may be completely impractical, but if so I will learn something from the more experienced contributors when they explain the reasons why.
How would a D bit go, and if a goer, would you hog out most of the material by drilling to set depths with a series of conventional drills first, and then clean up with the D bit or would you drill the whole way with the D bit?
I envisage turning the D bit in silver steel to the required taper and then grinding the cutting part down to within 5 or 10 thou of centre height, adding some clearance angles on the end before heating and quenching in water to harden the bit.
I imagine that it would be best to rough out the tapered section with a series of twist drills, and it maybe an idea to have a short pilot section on the end of the D bit which was a close fit in the smallest drilled hole section, so that the D bit had support on the far end. I'm may be over complicating matters here, but what do others think?
Finally, as this is(I think) my first posting since our Scraping School with Phil and Marco, I would just like to say hi to all of you that I met, and to express my thanks to all who helped organise the event, the catering staff and of course our host /tutors, Phil and Marco for an outstanding weekend. I really enjoyed meeting you all, and hope to catch up again before too long.
Regards,
Rob.

[Anorak Bob]

Not my handiwork Ray but I can't imagine grinding your own micro bar would present you with a problem. Search for Micro100. They often appear on US Ebay.

BT

ps. just found this - http://www.ebay.com/itm/Tapered-Cutter-Taper-Ball-End-Mill-Tool-5-DEGREE-ANGLE-1-2-shank-SOLID-CARBIDE-/120857941416?pt=LH_DefaultDomain_0&hash=item1c23b1d5a8

[Woodlee]

Machine a tapered D bit from 01 silver steel and harden it ,I made one to make the tapered holes for my dial indicator clamps worked ok .
Might take a bit of nutting out for a blind hole though .

I have some micro boring bars I"ve ground from 3/8" and 1/2 " HSS also , just takes a bit of time and paitience .

Kev.

[Michael G]

Yes, the offsetting is just to get some side relief

198540

Michael

[Steamwhisperer]

Hi Ray
Bobs photos are what I am talking about. Issue 168 of Model Engineers Workshop shows how to make them. If you can't get a copy I can post out it out to you.

Phil
http://img.tapatalk.com/79d6625a-1595-3b1e.jpg

[PDW]

Get an MT1 or 2 reamer, put it on the T&C grinder and re-grind the taper to what you need.

What, you don't have a T&C grinder? Perfect reason for buying another machine.....

PDW

[morrisman]

You can grind little boring bars out of square HSS . I've managed to bore out holes as small as 10mm with this tool . Only light cuts are possible as it will flex. But with patience , anything is possible.

Mike

[Abratool]

You can grind little boring bars out of square HSS . I've managed to bore out holes as small as 10mm with this tool . Only light cuts are possible as it will flex. But with patience , anything is possible.

Mike
Same here, Ive got a few of these, & they work well.
I use an off hand grinder to make these with an 8" dia by 1/2" grinding wheel in grade 46 (Coarse) its actually a 38A 46 K ( white Alox fairly soft bond) A J bond or H bond would even act softer & possibly cut cooler & faster.:2tsup:
On the other end of the grinder I have a white Alox grade 60 wheel in 8"' by 1"' for general drill & HSS toolbit sharpening.
regards
Bruce

[Dave J]

Hi Ray,
I take it this is for timber handles, if so what about drilling a small hole down it first, then make up a tapered spade bit with the sides sharpened as well with back rake. Instead of a point like spade bits have, just make it a round pilot so it follows the drilled hole. As long as everything was held firmly I couldn't see why it wouldn't work.

If you found it to be a bit hard in the tool, you could always drill the hole with a larger drill so far down to relieve it a bit, but I don't think you would have any problems.

Dave

[RayG]

Hi Dave,

I made a plastic cast of the inside of the Lie Nielsen socket chisels, to be able to measure the taper more accurately and they drill a pilot hole the same diameter as the small end of the taper, not sure how they machine the rest but either step drills then reamers, or maybe a tapered drill like the one BT linked to. Or a reground morse taper drill like PDW suggested

I think the step drill will be quicker and more consistent than a boring bar. Phil, I had a look for MEW168 but last one i've got is 160 :)

Thanks Michael G, Kev, Mike, Rob, Bryan, BT, Phil, Dave, Bruce and everyone, for all the suggestions. I've got enough good ideas to be able to try a few different things.

Welcome back Rob, :2tsup: I hope you had a good trip.

Regards
Ray