R8

[ARROW]

Hi
I would like to buy a new Drill Mill machine, which I am doing mostly drilling and back up milling. All ready have a 3mt Drill Mill.
My question is R8 collets chuck set, can they be use with drill bits and R8 x ER40 is 26mm the biggest size available.:)

Thanks Ross

[neksmerj]

Hi Ross,

According to the CTC Tools web site, 26mm is the biggest collet to suit the ER40 chuck.

Imperial it's 1"

A collet set from 2mm to 26mm, 24 pieces, is about $87 plus postage.
That's about $3.63 per collet, a bargain if they are concentric.

I just purchased an ER32 chuck and collet set, but can't vouch for their accuracy as yet.

Ken

[Dave J]

Gloster tooling have their own collets made up for the ER40 to go up to 30mm. A collet is fine for holding a drill bit.

Dave

[Woodlee]

Yeah ,but where do you get a 30mm straight shank drill? or even a 26mm straight shank drill for that matter ?

Kev.

[Dave J]

I agree Kev.
I took it as 2 questions, one as what is the max size they would hold and the other can they be used to hold a drill bit.

Dave

[ARROW]

Thank you Ken and Dave
I think Kev got a point there.

Which do you think is better R8 or 3MT

Great Forum, Thanks again Ross

[Dave J]

R8 is said to be better over the MT3

Dave

[ARROW]

Dave
Thank you

Cheers Ross :)

[Woodlee]

I'm not keen on r8 spindle bores , I have used machines with this set up many times in the past .The R8 is a proprietary spindle design of the Bridgeport company and was / is prominent in thier machines.
1. The r8 has a key or pin in the spindle bore which is supposed to mate with the slot machined on the arbour of the tool holder ,in my experience these pins seem to get mashed or broken off or lost within the first year or so of the machines life in the workshop.
2. the short taper on the arbour does not offer much support to the tool holder due to it's short bearing surface ,and coupled with the missing drive pin ,I have seen on a few occasions where the r8 arbour has spun in the spindle causing some grief.
Personally for a home machine I prefer the MT3 ,it has more contact bearing surface area than the bearing surface of the r8 and is supported by the spindle for its total length ,which when the draw bar it tightened it is a firm fit into the spindle.
The MT3 needs less torque to keep it in the spindle .
MT3 is mostly easy to get and you can use MT adapters for smaller MT tooling , larger sized drills most always come with MT tapers,unless you opt for reduced parallel shanks and use a Jacobs chuck or dedicated drill holders.

These are just observations and opinions which I have formed over many years in the machining trade.

Kev.

[ARROW]

Thank you Kev.

Regards Ross :)

[franco]

Ross,

If I had a mill drill with a 3MT spindle (which I have) and was doing mostly drilling with a bit of back-up milling, and if I was going to buy another one (which I'm not), I would stick with the 3MT so the existing tooling from the older mill could be used in the new one.

Another point is that many home shop sized lathes have an 3MT tailstock, and either a 3MT headstock spindle or a bush to allow a 3MT centre to be used in the headstock spindle. If you already have a lathe in this class or intend to buy one in the future, some items of mill tooling can also be used in the lathe if they have a 3MT arbor. For example a boring head held in the tailstock ram and fitted with a ball centre instead of a boring bar makes a fair substitute for a taper attachment, and a collet chuck with a 3MT arbor can be used in the lathe headstock spindle to hold small workpieces more accurately than the average 3 jaw chuck. Drill chucks with 3MT arbors are, of course, also interchangable between the two machines.

Frank.

[ARROW]

Thank you Frank, that's some good ideas.

Cheers Ross