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Drilling large holes

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Mike Poole16/01/2017 17:38:35
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3676 forum posts
82 photos

Most hobby mills run out of headroom if it is desired to mount a large drill. I have been toying with the idea of buying or making an adaptor to use Rotabroach style cutters, being a treppaning type operation less power is required and the cutters are available in short lengths and large diameters. Has anyone tried this? Did it work? What does the panel think?

Mike

image.jpeg

David Colwill16/01/2017 17:43:57
782 forum posts
40 photos

This is on my to do list. I have seen several people on youtube use them to great effect. I am just waiting to happen across the cutters at the right price.

Regards.

David.

David Colwill16/01/2017 17:45:13
782 forum posts
40 photos

I should also say that I would want to use them on the lathe as well.

David.

Peter Spink16/01/2017 17:47:56
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126 forum posts
48 photos

Bought one to cut some 28mm holes in 4mm brass. Only slight problem is the size of the shank which is too big for any of my collets. Used a small three jaw chuck instead with no issues and cut lovely clean holes.

Peter

Bikepete16/01/2017 17:53:21
250 forum posts
34 photos

Use them often, held in an ER32 collet. Bigger ones are usually available fairly cheap at a local autojumble.

clogs16/01/2017 18:01:38
630 forum posts
12 photos

Hi all,

I use them all the time in my Colch/Student 6" and both my mill's......I also use a mag drill machine quite often........

I use the R8/er32 collet holder in the mill and the correct mag drill bit holder in the tail stock, MT3 (I think)....

Works a treat, just use a slow speed (RPM) and plenty of cutting fluid.......

Clogs........

Dan Carter16/01/2017 18:07:40
81 forum posts
8 photos
I started using them on my X2 whose motor was too puny for big holes - they work really well. I made a holder including a sprung pilot pin for hole location. My new Mill is r8 and has dro, so can use 3/4 inch collet directly and hole location mostly not an issue.

The smaller ones are pretty cheap on Amazon, and msc had them on special offer last month so worth keeping an eye on.
Mike Poole16/01/2017 18:21:46
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3676 forum posts
82 photos

Thanks chaps, that seems like a positive endorsement, I will sort out an R8 adaptor for the mill and a morse 2 for the lathe. I think a rotation stop will be prudent with MT2 on the lathe, I imagine a larger cutter will need quite a bit of torque and MT2 is not used for drills over 22mm. Will give it a go!

Mike

Tim Stevens16/01/2017 18:30:44
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1779 forum posts
1 photos

I have had success with holes saws from the usual E source. Not the 'traditional' wavy saw tooth versions from builder's merchants. There are two types - one with a ring of ground teeth, and the others with a few carbide tipped teeth. For aluminium or brass sheet up to about 4mm, round holes and smooth. Also handy for generating spheres.

Cheers, Tim

Spurry16/01/2017 18:50:24
227 forum posts
72 photos

Only problem I have found is that you have to be very diligent with clearing the chips away, unless on thin material. They work well.

Pete

Mark C16/01/2017 19:07:11
707 forum posts
1 photos

As Tim, I have used conventional "builders" hole saws (the better quality ones) and have hacked my way through 12mm steel plate at 100mm diameter! You do need to use cutting fluid and keep the swarf cleared or it blocks the gullets and they stop cutting

Mark

not done it yet16/01/2017 19:13:11
7517 forum posts
20 photos

I bought a 'practool' years ago. It has done me sterling service over the years. Up to 40mm is no problem, apart from setting a specific size accurately.

http://www.practool.com/super-drill.html

Robin King16/01/2017 19:29:26
137 forum posts
1 photos

Peter Rawlinson's article in MEW Sept/Oct 1996 gave a useful intro to their use. I've since picked up a few from a local steelwork fabricator but haven't had a chance to use them yet. They stock a wide range of them in their stores shop so I'm hoping to get a few more.

Martin 10016/01/2017 20:14:29
287 forum posts
6 photos

I first used holesaws in the lathe in the mid 80's to cut 2 inch diameter holes in circa 3/4" steel followed by a boring operation. Mainly using the off the shelf yellow starrett holesaws as they were freely available.

I have some rotabroaches dating from I'd guess the late 1970's from 1/4" up to about 3/4" but they are still unused sat in a drawer in the toolchest.

Robbo16/01/2017 23:17:27
1504 forum posts
142 photos

Have used Rotabroach cutters for years, having made an arbour for them, including the pilot. After having bought one on ebay for a pittance, out of curiosity. Soon bought several more. Excellent hole cutters.

Carry on Mike.

Peter Spink16/01/2017 23:24:32
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126 forum posts
48 photos
Posted by Robbo on 16/01/2017 23:17:27:

Have used Rotabroach cutters for years, having made an arbour for them, including the pilot. After having bought one on ebay for a pittance, out of curiosity. Soon bought several more. Excellent hole cutters.

Carry on Mike.

Having only ever bought one so far, is the shank size standard over a range of sizes?

i.e. if I make an arbour for the one I've got, will it be useful in future?

Peter

John Reese17/01/2017 02:52:10
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1071 forum posts
Posted by Peter Spink on 16/01/2017 23:24:32:
Posted by Robbo on 16/01/2017 23:17:27:

Have used Rotabroach cutters for years, having made an arbour for them, including the pilot. After having bought one on ebay for a pittance, out of curiosity. Soon bought several more. Excellent hole cutters.

Carry on Mike.

Having only ever bought one so far, is the shank size standard over a range of sizes?

i.e. if I make an arbour for the one I've got, will it be useful in future?

Peter

All sizes have a 3/4" shank.

BW17/01/2017 05:43:28
249 forum posts
40 photos
Posted by Tim Stevens on 16/01/2017 18:30:44:

Also handy for generating spheres.

Cheers, Tim

Am guessing that its similar to the sphere generation by boring bar ?

ttps://www.youtube.com/watch?v=BJtxfI_LKio

Bill

Tim Stevens17/01/2017 08:54:19
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1779 forum posts
1 photos

I cannot say what Bill Wood is guessing, but I guess that he is right. The advantages are that you get several teeth rather than one, and that carbide is an off-the-shelf option for difficult materials. The disadvantage of a fixed cutting radius is not so serious in practice, and is hardly relevant when you look at the range of diameters available at very modest cost.

Here is a random example with tool diameters from 16mm to 50mm and prices from about £4 to under £7:
**LINK**

Cheers, Tim

Spurry20/01/2017 13:31:28
227 forum posts
72 photos

Rotabroach adapter 20mm

Just found an old picture I had taken last year. Fits a 20mm R8 collet.

Pete

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