Drilling 30mm hole through 10mm plate

[Stephen H]

Hi everyone. What's the best method for drilling a 30mm hole through a 10mm thick piece of 250mmx200mm steel?

While researching the problem I discovered the existence of step drills (https://mcjing.com.au/searchresult.aspx?keyword=multi-cut%20step%20drill) (and there's one that goes to 30mm!), but I suspect they're only for sheet metal.

What do you guys think? Would a step drill work, or is there a better way?

(Difficulty level: Cheapo Bunnings bench drill)


Stephen.

[RayG]

Good quality hole saw, lubricant, and correct speed. How many do you have to do?

Ray

[Oldneweng]

Step drills are intended for sheet metal only.

I will not say your task is impossible, but I would suggest it is pretty close. I think it would be very difficult and expensive. The only option as far as I know would be a core drill. I don't think your drill press would have enough power to do this job.

It would be cheaper and easier to get somebody with the proper equipment to do it. The other option is to drill a circle of small holes then file to size.

Dean

[simonl]

Use a hole saw with very light feed. Withdawl regularly to remove swarf and liberal lubrication. I recently drilled a 32mm hole in medium carbon steel 30mm thick. Just took some time.

Simon

Sent from my GT-I9195T using Tapatalk

[PDW]

Hi everyone. What's the best method for drilling a 30mm hole through a 10mm thick piece of 250mmx200mm steel?

While researching the problem I discovered the existence of step drills (https://mcjing.com.au/searchresult.aspx?keyword=multi-cut%20step%20drill) (and there's one that goes to 30mm!), but I suspect they're only for sheet metal.

What do you guys think? Would a step drill work, or is there a better way?

(Difficulty level: Cheapo Bunnings bench drill)


Stephen.

How close to 30mm do you need?

Simplest solution for you is probably to bring the piece of plate to me down the Channel or find an engineering shop up town. My Arboga drill could do it in one pass but I don't think I have a 30mm drill bit. 1.25" maybe.

Doing it on a Bunnings drill press - not going to work. Even if you buy all the bits that drill press won't go slow enough or have enough torque to get the job done.

As Ray said, good quality hole saw is your other best option. Lots of lubrication. Slow speed.

PDW

PDW

[LordBug]

Build a nice little dam around the hole with blu-tak or similar and fill it with lubricant.

[variant22]

Hole saws can get really nasty. Experimenting a few weeks ago I had one release my Jacobs Taper on two different chucks. Slow speed is absolutely key (as the others mentioned). I drilled (using a Sutton reduced shank drill) some 24mm holes a few weeks back in mild steel to a depth of 80mm. Was not bad at all with coolant and running a slow speed. The chips came out beautifully. The key is the speed and coolant.. I then used a boring head to take the hole out to the finish diameter. I know you are limited to a drill press, but a hole saw will give you a nasty and likely oversize hole. You could possibly investigate a Rotabroach drill/cutter but I have no experience with them. Some swear by them for larger diameter holes.

My vote is for you to take it to PDW..

305956

Edit: The more I think about it I am not sure a Bunnings drill press will have the torque needed to turn a large reduced shank drill. Hole saw may well be the only option..

[Ropetangler]

What Variant22 said, go meet PDW, with a suitable drill bit. That could be expensive, check eBay et al and a bit made by a reputable manufacturer, even if old and in need of sharpening could be much better than some no name drills made from who knows what, but new in a box. Pete knows how to sharpen drills!
Rob.

[tanii51]

another alternative but they have gotten a bit expensive since i bought mine http://www.practool.com/super-drill.html

[oohsam]

That super drill looks awesome......

[jhovel]

The 'superdrill' is exactly what I was going to suggest. I've nearly worn mine out...
hey should not be that difficult to make.
I think on the strength of this thread, I'll take measurements tonight and make a sketch. I think everyone should have at least one size of these.
They are actually a two-step piloted adjustable boring bar, not a drill at all. They work extremely well in a drill press.
Until later on - right here.

[Abratool]

The 'superdrill' is exactly what I was going to suggest. I've nearly worn mine out...
hey should not be that difficult to make.
I think on the strength of this thread, I'll take measurements tonight and make a sketch. I think everyone should have at least one size of these.
They are actually a two-step piloted adjustable boring bar, not a drill at all. They work extremely well in a drill press.
Until later on - right here.

These "Super drills make good sense, They seem to be a simple but good alternative for drilling large holes.
regards
Bruce
ps Like Joe mentioned should be easy to make.

[Stephen H]

Wow, some great advice.

I'm thinking my Bunnings cheapo bench drill isn't going to like a hole saw, so it look to me that my choice comes down to having someone else do it (thanks PWD - and to answer your question 1.25" would work fine), or investing $99 in one of those suspiciously magical Superdrills.

I gather from the Superdrill website that 1/2hp at 300RPM is preferred, but my Bunnings cheapo seems to be just under half HP at 0.47, and minimum RPM is 580. Anyone think that's close enough?

My preference is to do it myself (oh, and accumulate another tool in the process...), but I'm not going to be stupid about it - if I've got to take it to a shop, then so be it.

[BobL]

Wow, some great advice.

I'm thinking my Bunnings cheapo bench drill isn't going to like a hole saw, so it look to me that my choice comes down to having someone else do it (thanks PWD - and to answer your question 1.25" would work fine), or investing $99 in one of those suspiciously magical Superdrills.

I gather from the Superdrill website that 1/2hp at 300RPM is preferred, but my Bunnings cheapo seems to be just under half HP at 0.47, and minimum RPM is 580. Anyone think that's close enough?

HP wise that is OK but I personally think 300 RPM is a bit fast, (I would use 200) but that is just . At 600 RPM wise you might just end up blunting the cutters..

[jhovel]

Here it is - as close as I can make it to mine.
The Hex shaft is a mod - based on the shocking wear on mine. Cutting bigger holes is a struggle for a 1/2" chuck to hold this thing. I you can, make it hex. My original tool is mild steel. A better tool steel one would last longer. Case hardening would be even better.

I'm going to have a go at making a new one as well now. I intend to drill the two tool steel holes 6.35dia and then make a crude broach out of some 6.35 square tool steel (turning one end to 6.35 in a 4-jaw chuck and turning a taper from there to maybe 10mm from the other end. Then use my T&G grinder to make some teeth on all 4 sides along the taper). Then push the broach through the hole in my little press with cutting fluid.

By the way, I think the bottom cutter would be better at 4.8 or 5mm square - I have had the grub screw let go because the thread is a bit too short. Both cutters should be HSS.

In use, you drill a 12.7mm hole on the drill press, then swap for this tool and adjust the stick-out of the bottom cutter to the required radius between 12.7 and 25.4. If a bigger hole is required, then set to 12.7 radius and bore through. Then adjust top cutter to required radius.
Put moly grease on the piloting section and use cutting fluid for the cutter. Feed slowly. When you get a continuously curling swarf coming out of the hole, you have hit the 'sweet spot'.

The kit was/is available with bushes/spacers for larger holes still, but in my view the drive spindle diameter is too small for holes over 50mm and a 1/2" drill press not powerful enough.
If you find this useful for bigger sizes, make a bigger one for your mill!

[PDW]

Wow, some great advice.

I'm thinking my Bunnings cheapo bench drill isn't going to like a hole saw, so it look to me that my choice comes down to having someone else do it (thanks PWD - and to answer your question 1.25" would work fine), or investing $99 in one of those suspiciously magical Superdrills.

I gather from the Superdrill website that 1/2hp at 300RPM is preferred, but my Bunnings cheapo seems to be just under half HP at 0.47, and minimum RPM is 580. Anyone think that's close enough?


No, it's way too fast. Your drill press lacks rigidity and power, to put it politely. I wouldn't run a cutter at that diameter faster than 200 rpm in my Bridgeport mill.

Those superdrills are basically a single edge cutter with a pilot; I have a couple around here somewhere that I made 30 years ago. They do work well so are a good way to go, but you need to have the speed correct or all you'll do is burn the edge off and/or get absolutely massive chatter - this is why you need a nice fitting pilot hole as well. There's a good chance you'll pull the chuck loose from the drill press spindle if it starts chattering at speed because the cutting force is not axial to the spindle and any side load on a Morse taper is problematic.

580 rpm is also far too fast to run a hole saw into steel IMO and as has been observed, they cut a bad hole, oversized and rough. I've been thinking on making an adaptor for the slugger type trepanning bits for bigger holes but - it's low down on the long job list.

PDW

[DSEL74]

According to the website, Super Drill:

Because the cutters are made from 8% cobalt and the SUPER Drill body is hardened to internationally recognised hardness measure, 60 Rockwell, the SUPER Drill and its cutters is built strong to tackle your toughest drilling.

[BobL]

Joe, Thanks very much for the drawing, a couple of questions if I may.

I assume the diameter of the thickest shaft is 25mm?

I assume the cutters/holes are at some sort of angle from the centre line of the shaft?

As I can already drill 25 mm holes, I might make one that starts at 25mm

[PDW]

Joe, Thanks very much for the drawing, a couple of questions if I may.

I assume the diameter of the thickest shaft is 25mm?

I assume the cutters/holes are at some sort of angle from the centre line of the shaft?


From memory, 2 to 5 deg off of 90 deg so the outer tip cuts first. Could probably grind this angle into the tool bit. The ones I've used leave a little disk as they go through, the don't cut from the pilot hole out.

PDW

[DSEL74]

I see they also have a morse taper version. if your going to make your own wouldn't this be a better option? Knock the chuck out and fit the cutter directly into the spindle. Removes any error from the chuck or risk of damage to the chuck??

[RayG]

I like that super drill idea, it's been on the project list for ages, never makes it to the top however... Thanks Joe for posting it.... (BTW your monitor is ready)

Back to the original problem, I've had to drill a number of 25mm holes in 6mm steel over the last few weeks, part of a sliding gate project. I used a hole saw in an old AEG hand drill on low speed.. no trouble at all...

So, I think if the OP has a half way decent hand drill with 1/2" capacity chuck and a low speed range, forget the Bunnings drill press and do it by hand. Go half way and flip over, will make it a little easier for chips to clear.

While I was drilling the 25 mm holes in the posts, Josh used the mill and a boring bar to drill the 20 mm diameter holes in the 10mm base plates.. I got the easy job. :)

Ray

[Karl Robbers]

Superdrills are an awesome tool.
300RPM should be fine for a 30mm hole. Work on the rule of 1000RPM for a 10mm hole, 500 for 20mm and so forth. I reckon your cheap bunnings drill press will drop enough speed when you start cutting to not overheat the cutter, make sure you use a good cutting lubricant though.

[Stephen H]

I'm not clear on the difference between drilling and boring. Is it that the boring scrapes whereas drilling cuts?

[Michael G]

Both drilling and boring cut, but drilling cuts material away from the bottom of the hole and boring cuts material away from the side of the hole. (Normally you have to drill a hole before you can bore)

Michael

[RayG]

What Michael said, plus a boring bar is a single point cutter, and is used in a boring head that allows the diameter to adjusted very accurately. So when you want a nice clean hole of fairly accurate dimensions, you use a boring bar.

Boring is done on the lathe as well as a milling machine, when used on a lathe, you don't need the boring head, the lathe cross-slide allows to to move the boring bar to adjust the diameter of the hole.

Slow motion boring video...


https://www.youtube.com/watch?v=l_t8nqlLhH0


Then the next much more advanced stage is a boring and facing head... for that topic, I'll hand you back to Michael...

Ray

PS... Bored yet.. :)

[Big Shed]

I have only ever used a boring head/boring bar for enlarging the ID of a hole.

Question, is it possible to cut the OD of a circle by turning the cutting point of the boring bar inwards?

Say I have milled a 100mm square piece of 12mm thick steel flat and I want to have a 4 mm high x 90mm diameter circle on top, could you use the boring head/boring for this as described above?

[argeng]

Hi Gang,

I have had one of these for probably 15years, I had a good chat to the maker, from what I recall they are hardened, but depending on how much use that may not be necessary. The cutting bits are dead easy to sharpen and flipping them you can do holes in timber, upto 3" I think.
there was also a nifty tool for doing hose clamps out of stainless wire, always meant to make one but it ended up on the must do one day list.
Cheers
Bruce



Here it is - as close as I can make it to mine.
The Hex shaft is a mod - based on the shocking wear on mine. Cutting bigger holes is a struggle for a 1/2" chuck to hold this thing. I you can, make it hex. My original tool is mild steel. A better tool steel one would last longer. Case hardening would be even better.

I'm going to have a go at making a new one as well now. I intend to drill the two tool steel holes 6.35dia and then make a crude broach out of some 6.35 square tool steel (turning one end to 6.35 in a 4-jaw chuck and turning a taper from there to maybe 10mm from the other end. Then use my T&G grinder to make some teeth on all 4 sides along the taper). Then push the broach through the hole in my little press with cutting fluid.

By the way, I think the bottom cutter would be better at 4.8 or 5mm square - I have had the grub screw let go because the thread is a bit too short. Both cutters should be HSS.

In use, you drill a 12.7mm hole on the drill press, then swap for this tool and adjust the stick-out of the bottom cutter to the required radius between 12.7 and 25.4. If a bigger hole is required, then set to 12.7 radius and bore through. Then adjust top cutter to required radius.
Put moly grease on the piloting section and use cutting fluid for the cutter. Feed slowly. When you get a continuously curling swarf coming out of the hole, you have hit the 'sweet spot'.

The kit was/is available with bushes/spacers for larger holes still, but in my view the drive spindle diameter is too small for holes over 50mm and a 1/2" drill press not powerful enough.
If you find this useful for bigger sizes, make a bigger one for your mill!

[RayG]

I have only ever used a boring head/boring bar for enlarging the ID of a hole.

Question, is it possible to cut the OD of a circle by turning the cutting point of the boring bar inwards?

Say I have milled a 100mm square piece of 12mm thick steel flat and I want to have a 4 mm high x 90mm diameter circle on top, could you use the boring head/boring for this as described above?


I've never thought of doing it that way? Normally you would use a rotary table and just normal end-mill. Another way would be to mount it up in a 4 jaw chuck in the lathe. I won't mention CNC.. ( just did.. )

One problem that using a boring bar to do that job is that it would be an interrupted cut, on a large diameter that's going to cause problems with the boring head flexing and carrying on. Apart from those sort of problems I guess it might work?

Ray

[Michael G]

Question, is it possible to cut the OD of a circle by turning the cutting point of the boring bar inwards?

Say I have milled a 100mm square piece of 12mm thick steel flat and I want to have a 4 mm high x 90mm diameter circle on top, could you use the boring head/boring for this as described above?

Certainly can - you just need to make sure that the tip is facing the right way so that it will cut

Michael

[Big Shed]

I've never thought of doing it that way? Normally you would use a rotary table and just normal end-mill. Another way would be to mount it up in a 4 jaw chuck in the lathe. I won't mention CNC.. ( just did.. )

One problem that using a boring bar to do that job is that it would be an interrupted cut, on a large diameter that's going to cause problems with the boring head flexing and carrying on. Apart from those sort of problems I guess it might work?

Ray

Yes, I have done it like that (both ways), I was just curious whether it could be done with the boring head/bar.

In the (hypothetical) case above it would only be an interrupted cut for maybe 1 or 2 revolutions, after that it would be uninterrupted.


Certainly can - you just need to make sure that the tip is facing the right way so that it will cut

Michael

Yeah, that would help!

[SurfinNev]

Not sure if these will do 10mm but you could always flip it over and do from both sides.

http://www.ebay.com.au/itm/Tungsten-Carbide-Hole-Saw-20mm-Australian-Warranty-/261406077225

He has other sizes besides the 20mm in this listing.

Nev.

[variant22]

Question, is it possible to cut the OD of a circle by turning the cutting point of the boring bar inwards?

Yes. It works remarkably well. You have to turn the cutting point inwards as you mentioned, but also run the spindle in reverse. Today I cut down a 50mm piece of solid medium carbon steel to 38mm using that technique. I do not have a lathe, so this is my go-to option for turning down the OD of stock. I have a rotary table, but there is something rather soothing about using the boring head and the rotary table is darn heavy! Just have to keep an eye to make sure the boring head does not come undone, as running in reverse can unwind the thread (which incidentally it has done more than once!). I turned the boss (to a perfect 20.00mm) on the following part which is 1045 BMS using the reverse boring method.

306083

[jhovel]

I double checked this afternoon in preparation for a new and improved 'superdrill' type boring bar: the small cutting tool is in fact 3/16" (4.8mm) square, not 1/4"; the set screw for it comes in from the bottom down the centreline, not from the side and the main body is 1" (25,4mm) as already noted by BobL.

306107

The idea of a Morse taper shank instead of a round or hex drive end is excellent. To that end I cut the very worn drive of mine today and drilled and bored the large body to suit a No2 Morse taper I had doing nothing and pressed it in with a little Loktite. I'll cross drill it tomorrow and press in a hardened pin to make sure and try that.

I think I'll make the new one with Morse taper and just a 24mm body in one piece (like others here, I have a 24mm drill and my drill presses will drive that).

[Stephen H]

Not sure if these will do 10mm but you could always flip it over and do from both sides.

http://www.ebay.com.au/itm/Tungsten-Carbide-Hole-Saw-20mm-Australian-Warranty-/261406077225

He has other sizes besides the 20mm in this listing.

Nev.

That's interesting - the videos seem quite compelling, like cutting through butter. Key selling points are no need for cutting fluid and only 10kg down-force needed.

From the perspective of my cheapo bench drill, I'm thinking that the low down-force will be quite useful. Also, I'm assuming my drill's too-high RPM might decrease a fair wack under load.

My only concern is that the website says 5mm is max thickness, but the videos are cutting ~10mm.

I'm tempted to give it a go as they have a 30mm for $20.

[Anorak Bob]

Yes. It works remarkably well. You have to turn the cutting point inwards as you mentioned, but also run the spindle in reverse. Today I cut down a 50mm piece of solid medium carbon steel to 38mm using that technique. I do not have a lathe, so this is my go-to option for turning down the OD of stock. I have a rotary table, but there is something rather soothing about using the boring head and the rotary table is darn heavy! Just have to keep an eye to make sure the boring head does not come undone, as running in reverse can unwind the thread (which incidentally it has done more than once!). I turned the boss (to a perfect 20.00mm) on the following part which is 1045 BMS using the reverse boring method.

306083

Or use a left hand tool. My whizzo boring and facing head's arbor will unscrew itself if run in reverse. Photo 2 shows a left hand set up, the only thing left about it is the orientation of the square cutter. Looks simple enough.

306114

[Stustoys]

That's interesting - the videos seem quite compelling, like cutting through butter. Key selling points are no need for cutting fluid and only 10kg down-force needed.
To put it nicely I'd say that video is showing "best case".(whats the "coolant" he is using? WD40? makes for great pictures:D)
Having said that, for $20 if it gets you out of a corner its worth a shot.

Stuart

[Ropetangler]

Thanks everyone for your contributions to this thread, it has been most interesting. I have a couple of questions though or points I would like to have clarified. The commercial version leaves a small disc as it cuts through, which implies either a cutting tool sharpened so that it is lower on the outer tip when viewed as illustrated in Joes drawing of the tool, or alternatively the broached square hole for the cutter tilts down so that the cutter cuts the outside edge lower than the rest, without special grinding to achieve that result. I just wonder which way it has been done.
The other question I have is also concerning the broached square holes. On your sketch Joe, they both appear to be centred on the axis of the boring bar, but I would have thought that they should have been offset, so that the cutting edge of the cutter was on a radial centre line if that makes sense. That would mean that the 4.8mm cutter would be offset 2.4mm so that its cutting edge was on centre. I may just be imagining problems that aren't there, and making the whole process more difficult than need be, but would appreciate the groups thoughts on this. Thanks,
Rob

[Stustoys]

The other question I have is also concerning the broached square holes. On your sketch Joe, they both appear to be centred on the axis of the boring bar, but I would have thought that they should have been offset,
I dont see that it matters where the cutting edge is V the center of the boring bar. It may even be a good thing to be off centre as the end corner of the cutter could be negative rake(well at least "not positive"), the cutting edge would also be a little longer, though how much these things matter I dont know.
I've been wrong before though :D

Stuart

[Ropetangler]

I've been wrong before though :D

Stuart

You and me both Stu, at least once or twice.:U

[RayG]

I'm tempted to give it a go as they have a 30mm for $20.

That's cheap.. usually you'd pay 3 times that just for a decent arbor, and then still have to buy the holesaw itself.

Ray

[jhovel]

Sorry I didn't address the question of angled square holes: they are at right angles to the axis in mine and other I have seen. And they are centred, not offset. Clearance angles are ground front, bottom and periphery of the cutters.
Used my now Morse taper equipped one today: much more rigid and works like a charm. I also tried it in an existing hole, boring it a couple of mm bigger in diameter on the drill press. Not something I would have attempted chuck-mounted. Work piece clamped of course. No problem!

[Ropetangler]

Thanks Joe, it looks like I would have over engineered it, although with the holes tweaked a bit, the cutters may be simpler to get and maintain the correct geometry. For the time we would spend resharpening cutters though in the hobbyist workshop, possibly not worth the extra bother.
Rob

[DSEL74]

So who put their hand up to make batch???? I'm sure someone did :wink:

[variant22]

Or use a left hand tool. My whizzo boring and facing head's arbor will unscrew itself if run in reverse. Photo 2 shows a left hand set up, the only thing left about it is the orientation of the square cutter. Looks simple enough.

Ahh, Anorak Bob. Nice boring head. The idea is sound and looks relatively straight forward to make.

That being said, of all the boring heads you could post, you had to post a Kaiser. I was actually going to post a "Call out to Anorak Bob" thread (given you are a prolific and capable machinist) a few weeks back with a challenge to make a "poor mans" Big Kaiser - yep the digital boring head! http://youtu.be/ZReeMReAi8s?t=18s

I am desperate to make one of these. I have been trying to think of how to do the DRO part. I am thinking about buying a digital micrometer and tearing it down and trying to retrofit the screw mechanism into the boring head screw. The only issue is the cheap ones worthy of wrecking all have huge LCD's! Ugh!

I might have to create a new thread dedicated to it..

[Ropetangler]

Ahh, Anorak Bob. Nice boring head. The idea is sound and looks relatively straight forward to make.

That being said, of all the boring heads you could post, you had to post a Kaiser. I was actually going to post a "Call out to Anorak Bob" thread (given you are a prolific and capable machinist) a few weeks back with a challenge to make a "poor mans" Big Kaiser - yep the digital boring head! http://youtu.be/ZReeMReAi8s?t=18s

Mmmm... Very nice boring head, but I doubt that they make one to suit a Hercus mill or even BTs big Schaublin 13! Keep us posted with pics if you make your version of it though, it will be a mighty nice acquisition when you pull it off, assuming you find suitable donor parts,
Rob

[Michael G]

That being said, of all the boring heads you could post, you had to post a Kaiser.

Well yes - he only has one.

Michael

[Ueee]

You could fit a standard caliper screen on something the size of my UPA5-S6, but then you would never be able to use it in your mill, you'd have to send it to one of us with a big mill......like me:D

Ew

[SurfinNev]

Just remembered I have the BORDO brand in the TCT hole saws. I have the 25, 28, 30, 32mm. All unused so far so don't know how they perform. Mine have a capacity of 25mm. Instructions say remove ejector spring for holes deeper than 13mm so just be aware of that.

Nev.

[Anorak Bob]

Well yes - he only has one.

Michael

Out done by Michael himself who possesses a Wohlhaupter, a Kaiser and a Tree. As for a digital boring head, way over my head. Why, I'm struggling to make a bloody arbor for my Kaiser!:no:

BT

[Michael G]

Out done by Michael himself who possesses a Wohlhaupter, a Kaiser and a Tree.

Only the Tree and Wohlhaupter at the moment Bob - for a number of reasons the Kaiser is now with Peter (PDW). However, they are cool little things so if you ever spot a Metric Kaiser with a SK40 taper at a sensible price do let me know. Gummed up with missing parts no problem!

Michael

[Anorak Bob]

Only the Tree and Wohlhaupter at the moment Bob - for a number of reasons the Kaiser is now with Peter (PDW). However, they are cool little things so if you ever spot a Metric Kaiser with a SK40 taper at a sensible price do let me know. Gummed up with missing parts no problem!

Michael

Just like this one hey Michael? Latter model than ours and this sold for 53 EUR more than mine.

http://www.ebay.de/itm/KAISER-Plan-und-Ausdrekopf-SK40-Aufnahme-wechselbar-/281254264463?ru=http%3A%2F%2Fwww.ebay.de%2Fsch%2Fi.html%3F_sacat%3D0%26_from%3DR40%26_nkw%3D281254264463%26_rdc%3D1&nma=true&si=m4d%252BZLTruLo32mlwOLSzWZNBIDs%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557

BT

[Stephen H]

Just remembered I have the BORDO brand in the TCT hole saws. I have the 25, 28, 30, 32mm. All unused so far so don't know how they perform. Mine have a capacity of 25mm. Instructions say remove ejector spring for holes deeper than 13mm so just be aware of that.

Nev.

Do the instructions refer to a recommended RPM for the 30mm cut?

[Gavin Newman]

Do the instructions refer to a recommended RPM for the 30mm cut?

According to Starret and RUKO (http://www.automationdirect.com/static/specs/holesawcutspeeds.pdf), around 300 RPM.

I've also found that with thicker plate it helps to start the cut and once the kerf is established, drill a number of small diameter holes through the plate in the kerf - some of the swarf leaves the cuts through those holes and the saw doesn't jam.

[RayG]

Here's a simple demo..

40 year old AEG 2 speed drill, 25mm sutton hole saw, Rocol cutting fluid, 10mm thick flat bar.

Drilled a bit over half way, then flipped over and finished from the other side.. total time less than 5 minutes.

306381306382

Ray

[SurfinNev]

Do the instructions refer to a recommended RPM for the 30mm cut?

Instructions say 500-1600 RPM. That I assume, just covers a range of materials. Nothing specific.

Nev.

[Ben Dono]

[QUOTE=jhovel;1752801]Here it is

Thanks mate! I was in a bind today so in knocked up a simpler version. I needed about 21.7mm holes in 3mm RHS. I used a step drill up to 3/4 ( I don't know why people bag step drills, I have been using the same one for years and it still punches holes in 10mm). And followed up with a Ben Super drill!

I did not bother making it fancy. I just drilled a hole (next imperial size up from 9mm) and used a grub screw from the bottom to secure the 1/4" hss. It held strong enough. When I make some more I will grind up a broach from 1/4 hss and drill an 8.5mm hole. It should pass through easily enough and give enough of a key to help setting the dept of cut.

Could you get rid of one of the relief angles in the cutter by drilling the hole a few degrees off perpendicular? Anyone got a thought on that?

[jhovel]

Hi Ben,
the original cutters hat came with mine only had a relief angle at the bottom, parallel to the cutter bottom - maybe 5 deg. t also has a positive cutting angle - maybe 15 deg. The outside face of the cutter is ground to have a tiny relief at the smallest possible diameter - which means the curve has a slightly smaller radius than the small hole, but a little offset. It also means the bigger the hoe the bigger the relief.
In use, it peels off swarf which is the full size of the cut in width, just very thin. I have never tried it in brass or aluminium, but suspect it won't work well at all.

[mike48]

Boring Cutter for Drill Press.

The wealth of info in this thread intrigued me to the point of making a prototype simple cutter like Ben has mentioned.
I needed something to make 24mm dia holes in 12mm mild steel plate.

I used a 1/2 inch UNF by 6 inch Grade 8 bolt as the shank, cut down to 100mm clear length, and a piece of quality 3/16 HSS square tooling as the cutter.

Drilled a 6mm hole at 90 deg across the bolt shank 15mm from the bottom face.
Drilled a 3.8mm dia hole into the bottom, approx 3mm offset from centre, and at approx 10 deg off vertical, and tapped 3/16 BSW, so as to position the end face of a 1/2 inch long grub screw in the middle of the cross hole. The grub screw offset hole axis is at 90 deg to the cross hole, when looking at the bottom of the shank.
The grub screw end face was ground flat.

The cutter has 10 deg bottom relief, the cutter face is at 6 deg, and the end relief is 15 deg. The top two corners of the cutter have been slightly ground, so as to more snugly fit wedged into the round hole by the grubscrew. (The cutting angle is relatively small, because I was cautious about grab and feed control in my drill press).

Works like a treat, peeling off steel shavings like butter, after you find the feed sweet spot.
Use cutting fluid for shank lubrication as well as cutting.
How did I ever exist without one of these?
Thank you everyone.

cheerio, mike

308744