Using annular cutters in a milling machine

[Bill PhinnParticipant @billphinn90025]

I know that some members use annular cutters in their milling machines for drilling largish holes.

What is the best way of holding the 3/4″ Weldon shanks these typically have? A side-lock endmill holder?

Would ER collets or direct collets be out of the question? I ask because from what I’ve seen it looks like annular cutters have more than one flat on their shanks, which may make holding them in ER or direct collets less than ideal.

[Nigel Graham 2Participant @nigelgraham2]

By annular cutters, are these hole saws? I sometimes use those for roughing out holes, and they typically have hexagonal shanks for holding in drill-chucks.

[noel shelleyParticipant @noelshelley55608]

I think we are talking about Rota Broaches, with a 3/4″ shank and 2 flats at 90* apart ? They cut beautifully DO NOT over speed them and use a good cutting fluid. A holder to fit what ever machine you have should be easy to make. Cutting on many teeth at once I fancy the torque is fairly high ? The centre is spring loaded. I’m surprised that more people on here don’t use them. It is vital that the work is clamped – holding by hand is not a good idea. Normally used in a Mag drill and sizes to 50mm or more are available, smallest I have is 11mm ! They come in 2 lengths 25mm and 50mm.  I can sketch the holder I have though I have not tried an ER32 collet. Noel.

[JasonBModerator @jasonb]

I would have thought a blank end arbor bored and with two grub screws was the most secure as I don’t think you can get weldon type side lock in 3/4″ on MT3 or R8

[DiogenesParticipant @diogenes]

Edit; Hadn’t seen Jason’s reply before I posted mine..

+1

Morse and R8 holders are available to buy, possibly other styles too, by now.

The ‘proper’ holder is like a sidelock endmill holder but with two locking screws disposed at 90* to grip matching flats on the standard (nominally) 3/4″ broach shank.

..the locking screws & flats are substantial – M10, maybe? something of that order..

Within the body of the ‘standard’ morse holder is a spring loaded plunger that supports a ‘pilot’ pin to aid in locating the hole centre and allows it to retract during cutting.

I’ve used one on the mill for two years, as I use the DRO or other methods to locate the hole I’ve never bothered with the pins. I’ve never had a core stick, and in any case there’s still the pin hole through the shank from which to push it out.

Not sure whether the R8 versions have a pin or not – I assume they must have provision for a drawbar? ?instead?

I think one could easily make an adaptor from a substantial blank arbor if the central plunger assembly was omitted..

They are far & away the quickest & cleanest way to poke large ‘acceptably-finished-and-fairly-accurate’ holes through steel, I found them transformative – knocking ‘inch-plus’ holes through even thicker steel can be a chore, they do take much of the tedium out of it.

 

[Martin ConnellyParticipant @martinconnelly55370]

I use a Ø19 ER32 collet and have had no problems. I also have an MT2 to ER32 collet holder for use in my lathe tailstock. I made some Al alloy bearing carriers for someone last week and after cutting off two 32mm thick blanks the first operation was to use a 50mm Rotabroach style cutter from both sides to take out a large plug that can be kept for further use. The final bore was Ø56 for a retaining lip and Ø62 for the bearings so a lot of wasteful (time and material) drilling and boring if you  don’t remove a big plug first.

You need plenty of torque for the bigger cutters so back gear on the lathe and low gear or low speed pulleys on the mill. Not sure all electronically speed controlled motors will have the needed torque.

Martin C

[Pete RimmerParticipant @peterimmer30576]

I used to use them in a 3/4″ R8 collet on my old milling machine. They don’t only make great hole saws but they also make fairly dandy face mills if you only take a small skim. Easy to sharpen too.

[noel shelleyParticipant @noelshelley55608]

The main purpose of the centre pin is to be able to centre the hole on the marked spot – it will pick up a dot punch mark easily ! Unless you have clever electronics and XY control it is much simpler to let the pin drop in the dot mark and your there ! It is very difficult to see or centre a broach without it – I have tried !

In he context of torque/ power needed My mag drill at 1100 watts is geared well down but is limited to 28mm ! A lathe or mill with 750w or less even geared well down may grunt and a machine with a VFD would need to be used with great caution.  Noel.

[Bill PhinnParticipant @billphinn90025]

Many thanks to everyone for your replies.

Yes, annular cutters are what are typically used in mag drills. Nigel is correct, however, in that a hole saw (usually for wood), like a core drill (usually for masonry), is still in a sense an annular cutter, since annular just means ring shaped.

Apparently, as Diogenes mentions, Accusize do R8 and MT2 (and 3?) sidelock arbors specifically for 3/4″ shank annular cutters. They have two socket set screws at 90 degrees to each other.  They’re a bit pricey though.

Noel, you mention being willing to show me a sketch of your shop-made holder. I’d be interested to see it. I would need an R8 one, though, so making that would be beyond me. I seem to remember seeing a video of MrPete222 making one with an MT2 mount. And then I think a viewer gifted him an R8 one as well.

Jason, do I read you correctly? Are you saying there is such a thing available as an R8 blank arbor that could be bored into a 3/4″ sidelock holder?

[noel shelleyParticipant @noelshelley55608]

Hi Bill, It may be a few days, it’s at my workshop in town. I will measure and draw it up and post as a jpeg if the forum will let me. Noel.

[JasonBModerator @jasonb]

Bill, I’m sure I have seen blank R8 with a larger head at the moment all that is coming up are ones with 1 1/8″  heads which is a bit on the small side to get any decent grub screw thread in.

[Martin ConnellyParticipant @martinconnelly55370]

Today’s parts. I am making a couple of rings for a friend, 2 in 6mm mild steel and 2 in 5mm stainless. They need boring out to Ø74 so the first thing to do on the supplied material is to cut out a Ø50 hole with a broaching cutter. Cycle time for this was about 4 minutes. 106rpm (back gear). Roebuck RB7 cutting compound brushed onto the surface for initial cutting then just keep the pressure on until through. The cutter was held in a Ø19 ER32 collet in the lathe’s MT2 tailstock and hand fed.

Martin C

[Bill PhinnParticipant @billphinn90025]

Thanks for the information, Martin.

I’ve got 3/4” as well as 19mm ER32 collets, so when I get an annular cutter or two I’ll be trying them out on the mill. I can’t use them in the lathe yet because my ER32 chuck is R8 not MT, and I haven’t made an MT arbor.

[Alistair Robertson 1Participant @alistairrobertson1]

When I worked with an agricultural machinery company we used a 76mm Roto-Broach to machine holes through both sides of a 150mm x 150mm box section with a 12mm wall.  The components at up to 12 foot long were clamped in a simple jig and the holes were about 200mm apart. The Roto-Broaches were able to cut about 1600 holes (Through both sides!) before they were resharpened.  Around 1000 components were made for each season. The use of Roto-Broaches cut the cost of the operation by about 40% and only one Broach was broken in about 15 years!

 

[Bill PhinnParticipant @billphinn90025]

On the subject of appropriate rpm for annular cutters, in the following video (at 4m.48s.) Adam Savage, using what looks like a 2″ cutter, says “you don’t want to go too fast..so I’m going down to like 900rpm and may go even slower”.

I accept that he’s cutting non-ferrous material, but isn’t 900 rpm rather faster than these are typically run in mag drills, and faster than you’d want to run a 2″ annular cutter on a mill?

[JasonBModerator @jasonb]

140m/min Vc is not unusual for an HSS cutter in aluminium but is towards the upper limit which is what 900rpm on a 2″ cutter would give. Rigid machine with belt driven varispeed head will have the guts and rigidity to take those sort of cuts. Mini-mill may want a rethink.

Steel you may want to be 25-30m/min Vc so 160-190rpm

[noel shelleyParticipant @noelshelley55608]

900rpm way to fast 300 would be more like it ! Noel.

[JasonB]

On JasonB Said:

I would have thought a blank end arbor bored and with two grub screws was the most secure as I don’t think you can get weldon type side lock in 3/4″ on MT3 or R8

I don’t have anything R8, but would one of these be suitable; Gloster Tooling

 

Bill

[Mark RandParticipant @markrand96270]

• my Rotabroach drill runs at a fixed speed of 600rpm.
• I use Rotabroach cutters in the mill in a 3/4″ ER32 collet. Note that the shanks don’t extend for the full depth of the collet. I use a ‘mushroom’ with a reduced stalk and a 3/4″ head that is put behind the cutter’s shank to ensure that the collet closes parallel.

[Bill PhinnParticipant @billphinn90025]

Thanks for the further replies.

Bill, Gloster Tooling don’t currently have a 3/4″ sidelock endmill holder.

The problem with these R8 endmill holders (and I have a few in various sizes) is that the set screw position doesn’t always correspond with how far you want or need to insert the shank of your cutting tool, i.e. where the flat on it is. I’ve got a 1/4″ endmill holder, bought recently, and the set screw is way too far up the body of the arbor and way too big (M12!). I’ve not yet got round to drilling and tapping for a set screw in a more sensible location. Hopefully the steel won’t be too hard.

There’s a chance the set screw on a 3/4″ endmill holder like the one in Gloster Tooling’s catalogue will be in the right place for one of the flats on an annular cutter, but given the shortness of annular cutter shanks there’s a higher chance, I’d say, that the set screw position will be wrong.

EtA: Thanks for the information, Mark.

 

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, I’ve used hole saws in the lathe tailstock to cut large holes, my last time was to cut a slice off a short length of 80mm diameter BMS, to a thickness of about 16mm. This was achieved by cutting a groove, using a parting tool, to a depth of the 38mm hole saw I was using, to end up with a spigot on the remaining piece.

This saved making a lot of swarf and gave me a large thick washer that was hiding in there.

The other piece was then finished to size, and the spigot threaded to take a screw on three jaw chuck for my mini lathe.

Regards Nick.

[Martin ConnellyParticipant @martinconnelly55370]

The use of high RPM with a broaching cutter on a lathe is that the chuck will fling swarf far and wide. I could possibly run a Ø50 cutter in mild steel at 600 RPM but then there would be a need to keep backing off to break the swarf and clear it before continuing. I don’t think it would be much faster than using a slow rpm with the occasional stop for swarf clearance. On a mill or using a mag base drill with a vertical spindle and no large chuck and workpiece spinning around this would not be such an issue.

Martin C

[noel shelleyParticipant @noelshelley55608]

To Bill Et al ! I have sketched up the rota broach holder ! Send me a PM with an Email address and I will send you a description and a picture of the sketch. Noel

[Bill PhinnParticipant @billphinn90025]

Hi Noel,

I’ve tried three times to send you a pm, but the forum software is not recognising “noel shelley”, “@noelshelley55608“, or “noelshelley55608” as a forum member.

It keeps coming back with the message: “Your message was not sent. Please enter a username or Friend’s name.”

 

[JasonBModerator @jasonb]

Just worked oK for me Bill. Have another go incase it was just a temporary glitch. You should be able to click noel shelley above the blank avatar and that brings up his profile, click the “private message” box and the username will come up automatically highlighted yellow. Don’t enter anyone else in the box next to it, just come down and enter subject and down again for text

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