Gamet GMT Automatic Boring Head Question

[HollowpointParticipant @hollowpoint]

Hi guys

I recently acquired a GMT boring head at a price I couldn’t refuse. It’s a lovely thing but the arbor is morse taper 2 and my mill is R8 so I would like to replace it. Does anyone know if the arbor should just screw off? It certainly looks like the head and arbor are two separate parts, but holding it in my vice (with rubber padded jaws) and trying to unscrew it by hand didn’t work. I want to be certain before I apply any more force!

Thanks in advance.

 

[DC31kParticipant @dc31k]

A quick search on the internet reveals the following. How is it that I can find it, but you cannot?

GMT automatic boring head

https://www.practicalmachinist.com/forum/threads/enco-gamet-boring-facing-head-manual.226381/

https://owwm.org/viewtopic.php?f=77&t=93335&hilit=boring+head

https://app.box.com/s/779cj5fy15 – this is the manual, which shows an exploded view.

[HollowpointParticipant @hollowpoint]

We all have different levels of ability. Perhaps you’re just better than me. 🤷🏼‍♂️

A more knowledgeable person wouldn’t have had to search the internet.

Thanks.

[Pete.Participant @pete-2]

Did you manage to get the arbor off?

I bought one of these a few years ago,  not dirt cheap though as it’s on an int30 arbor and got bid up to around £200, but worth it imo as the new price for even far eastern copies is 3 or 4 times that.

Are you making an arbor or found a replacement?

[HollowpointParticipant @hollowpoint]

I was gonna purchase an R8 soft arbor to make my own, but I spent about 3 hours this afternoon trying to get it off with no luck! 😔

I can actually see that the arbor is indeed threaded now, and that their is a grub screw that locks the thread. I think that the old oil has dried and is now acting a bit like glue. My biggest problem though, is that I can’t hold the morse taper arbor without it slipping. I don’t want to damage it either.

[Robert Atkinson 2Participant @robertatkinson2]

One thing to remember when comparing search results is that most search engines tailor their response based on your search history. Even the same term on the same engine can give different results. Location and even the type of device can also make a difference.

Robert.

[Hollowpoint]

On Hollowpoint Said:

I was gonna purchase an R8 soft arbor to make my own, but I spent about 3 hours this afternoon trying to get it off with no luck! 😔

I can actually see that the arbor is indeed threaded now, and that their is a grub screw that locks the thread. I think that the old oil has dried and is now acting a bit like glue. My biggest problem though, is that I can’t hold the morse taper arbor without it slipping. I don’t want to damage it either.

Can you get an old MT-2 to MT-3 adaptor sleeve and use that to protect the arbour when un-screwing it?

Robert.

[Clive FosterParticipant @clivefoster55965]

For a similar situation I found a parallel sleeve with MT taper inside for very little money which worked well when held in the vice between two Vee blocks. That was drilled right through so I could run a bolt into the drawbar thread on the arbour I needed to shift. So everything was very secure. Presumably old stock capstan tooling.

Mrs Google says that similar items with a tang slot are fairly readily available for £10 – £15 (ish) new – new.

Clive

 

[Pete.Participant @pete-2]

I took a look at mine earlier as the auto feed never worked and after not being able to loosen the arbor I just left it but this thread sparked my interest in trying to sort it out.

After dismantling it I noticed a small spring at the base of the pawl missing,  about 5mm diameter maybe 15~20mm long, pushing the pawl up manually it worked while rotating although I did come across something I’m not sure about.

[Pete.Participant @pete-2]

If you dismantle the body, it gives you a flat side so you can hold it pretty securely in the vice, luckily I’ve got a large set of pliers wrench which fit across the flats of the cut outs for the drive dogs on the arbor.

After removing all the screws the side the body is held on by two dowls,  if you hold a pin punch where sliding ways are (bottom photo) and gently tap it by hand a little each side slowly that comes off pretty easily.

One thing that puzzled me was the ‘ramp’ turning the Allen screw on the knurled part raises and lowers the ramp turning the auto feed on and off from what I understand,  but directly opposite there another fixed pin holding the opposite ramp up permanently and seemed to make the auto feed work whether the feed on/off screw opposite was adjusted with the ramp up or down? Is yours like this?

[HollowpointParticipant @hollowpoint]

Yes it’s the same. I believe that the pin with the hole is for use with a long tommy bar which rests against the column of your mill, so you don’t have to hold it.

The “on off screw” isn’t actually on and off. It’s 2 feed rates. On mine the first position is 1 click per revolution (0.05) and position two is 2 clicks per revolution (0.1).

So the ramp in the permanent up position must be 1 click and then adjusting the screw lifts the second ramp to give 2 clicks.

Hope that makes sense.

[HollowpointParticipant @hollowpoint]

While it’s appart, could you measure the thread for me please? Just the length from the end to the shoulder will do.

I want to know if the soft arbor chronos sells has enough “meat” at the end.

[Pete.Participant @pete-2]

Ye sure I’ll check the length later.

I did wonder about that but thanks for confirming the ramp switch just changes it from one pawl movement per rotation to two, before I took the arbor off I looked in and wondered if it’d been crashed and jammed one ramp up or something,  I’m glad it hasn’t been.

[Pete.Participant @pete-2]

[HollowpointParticipant @hollowpoint]

Perfect! Thank you. Much appreciated. 🙂👍

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