Gun Drill Adaptation.

[niall Y]

Nor sure that this is the appropriate forum, though in its normal context, this sort of drill is used for metal working. I, however , have one I wish to use for,wood, so will be swapping out the coolant for compressed air.

I need to get a compressed air line onto the end of this drill. And am open to any suggestions as to how to do this. Hammond and Co, do sell an adaptor that fits into the Morse taper of the lathes tailstock, which in turn mates with the particular driver on the non-business end of the drill.

This particular option isn't open to me as the distance between centres on my lathe would have to be in the region of 1metre to accommodate the workpiece and the drill at commencement of the cut. So, I am going to have to use it hand held,

The obvious solution would be to enlarge the hole in the driver and fit in a 1/4" Bsp connector,but the driver is hardened steel. And I am not sure I can safely anneal it enough to drill out and tap a thread.

Any advice, or other suggestions would be welcomed

Niall


THE DRIVER IN QUESTION WHICH IS 25mm IN DIAMETER

 

[ChaiLatte]

Can you go larger than the 25mm diameter with any part of the connection?

Find some nominal 1" bore rubber hose and jubilee clip it onto the steel part.

You could buy a brass BSP connector with an inside diameter >25mm and JB Weld it on.

A more refined solution would be to turn the ID of the brass piece to 25.1mm and use loctite. This has the advantage that you can heat it up to denature the loctite in the future if the part needs removing.

If you cannot increase the OD of the part, loctite something into the hole in the hardened piece. Sure, it may restrict the airflow a little, but probably not enough to cause a problem.

 

[niall Y]

Can you go larger than the 25mm diameter with any part of the connection?

Find some nominal 1" bore rubber hose and jubilee clip it onto the steel part.

You could buy a brass BSP connector with an inside diameter >25mm and JB Weld it on.

A more refined solution would be to turn the ID of the brass piece to 25.1mm and use loctite. This has the advantage that you can heat it up to denature the loctite in the future if the part needs removing.

If you cannot increase the OD of the part, loctite something into the hole in the hardened piece. Sure, it may restrict the airflow a little, but probably not enough to cause a problem.

Thanks for the reply,
Yes, I can have it larger than the 25mm at least to something I could comfortably hold in my hand. There is an American turner demonstrating using a gun drill who has an anodised aluminium handle attached to his with a hose line fixed to the end.

I haven't seen anything equivalent for sale in this country. These I believe mate with the particular driver design that allows them to clip into position. I believe mine has the European Standard fixing system.

I am already toying with your last suggestion, which in my case would to be to use a 1/8" BSP airline connector into the end of the driver, either epoxied directly in position or into a threaded sleeve that itself can, in turn be epoxied in position.. To this end I am waiting delivery of a fitting I can experiment with.

I feel it would be better to have some form of handle - wood,metal, or plastic - that I could fasten on and remove more conveniently other than having to use heat to break a bond. - as with Loctite, or standard Araldite. Though, at the moment I can't envisage how to do this.

I have considered using some rubber hose to cobble together a fitting, but I think Jubilee connectors in this context might be a bit of a no, no, as they might damage ones hands if the drill catches and starts revolving

 

[ChaiLatte]

I feel it would be better to have some form of handle - wood,metal, or plastic - that I could fasten on...

The end of the piece in the photo seems to have a flat milled on it. A grubscrew could secure a handle to that.

You could incorporate an O-ring into the handle to provide an air seal (that may also need PTFE tape on the grubscrew to stop it leaking).

A wooden handle with a threaded insert for the grubscrew would look quite classy as you could carve some hand grips in it after it is turned (saturate the BSP threads with superglue to strengthen them).

 

[niall Y]

The end of the piece in the photo seems to have a flat milled on it. A grubscrew could secure a handle to that.

You could incorporate an O-ring into the handle to provide an air seal (that may also need PTFE tape on the grubscrew to stop it leaking).

A wooden handle with a threaded insert for the grubscrew would look quite classy as you could carve some hand grips in it after it is turned (saturate the BSP threads with superglue to strengthen them).

View attachment 196272

You must have been shadowing my thoughts. I have come up with a similar design but putting the grub-screw at a slight angle to hit the machined flat at right angles. I've been looking at using aluminium rod to form the handle, with a silicone washer to help make a seal at the base between the bit and handle. If it is needed their might even be scope to screw a 3mm thick stainless steel washer ( with a slot cut out of it to accommodate the shaft) over the front of the handle.

If I aim to use 45mm stock there should be ample room to get a fix.

 

[Richard Evans]

I have used gun drills for many years to drill African blackwood for bagpipe making. I use a home made attachement. It's a piece of delrin bored to accept the drill with an fitting to attach the air line. It's pretty ramshackle but it works. It's just hand held. The retaining nut arrangement is some kind of plumbing fitting, a pretty poor system but it works. You could fit an O ring, I just accept a small amount of leakage.

 

[niall Y]

I have used gun drills for many years to drill African blackwood for bagpipe making. I use a home made attachement. It's a piece of delrin bored to accept the drill with an fitting to attach the air line. It's pretty ramshackle but it works. It's just hand held. The retaining nut arrangement is some kind of plumbing fitting, a pretty poor system but it works. You could fit an O ring, I just accept a small amount of leakage.

I like it, It looks to be a smaller gauge all round than the size I am dealing with. I'm intrigued by the plumbing fitting at the end, I assume the driver slips into this and is held by tightening the outside nut.
How have you attached the fitting itself to the Delrin handle?

 

[Tris]

Interested to know what the advantages of a gun drill are over a lamp auger (shell bit type)?

Just making up a vacuum chuck and found delrin takes a thread very well, a bit of PTFE tape and there's no leakage

 

[niall Y]

Interested to know what the advantages of a gun drill are over a lamp auger (shell bit type)?

I've not used them before, so when I get up and running this will be a first for me. @Richard Evans is probably better placed to speak of the advantages.

I only purchased one because I need to drill holes of a specific diameter - in my case 14mm. With standard long hole borers one is restricted to the usual 8mm, though I do have a less common 12mm one , that was given to me by a friend, This can be really hard going especially in timbers like African Blackwood, and I find I have to use the 8mm one first, to make things easier.

 

[ChaiLatte]

I'm intrigued by the plumbing fitting at the end

It would be one of these:

https://www.valvestubesfittings.com/shop/product/brass-compression-male-iron-straight-adaptor/

As your drill shank is 25mm, an option might be something similar but meant for MDPE pipe (blue water pipe) as that does come in 25mm diameter.

This one will compress onto 25mm diameter at the big end, and taking off the nut at the small end will give you a 1/2" BSP male thread.

https://ondemandsupplies.co.uk/25mm-mdpe-to-15mm-compression-reducing-coupling/

The difficulty might be that the olive, once compressed, will want to stay on the metal part.

 

[Richard Evans]

I like it, It looks to be a smaller gauge all round than the size I am dealing with. I'm intrigued by the plumbing fitting at the end, I assume the driver slips into this and is held by tightening the outside nut.
How have you attached the fitting itself to the Delrin handle?

The plumbing fitting was araldited on. This came loose so I bored a hole in the fitting and pt a self tapping screw through and into the delrin Horrible! In another post you mention a 14mm bore- You will probably need a more robust fixture for this. My maximum bore is 9mm and that is on the limit for hand held as far as I'm concerned.

 

[Richard Evans]

Interested to know what the advantages of a gun drill are over a lamp auger (shell bit type)?

Just making up a vacuum chuck and found delrin takes a thread very well, a bit of PTFE tape and there's no leakage

A gun drill gives a dead straight polished bore, it acts as both drill and reamer. And the compressed air expels the chips so I can drill for example 4mm diam 30mm deep in a single pass, very quickly..

 

[niall Y]

Following on from my queries I thought folk might be interested in seeing the end result. And, many thanks to all those who helped with the design

The body is Maple, drilled so far down at 25mm diameter, to take the gun drill, with a further 8mm hole to channel the compressed air in from the end. The hose fitting was set into this with JD weld in a counterbored hole. An adapted stainless steel washer holds the drill firmly in place against a silicone washer at the base of the hole by means of 3 Allen screws. These engage in brass, cross dowels , set into the sides of the wooden handle.
The yellow dimple on the top contains a brass, threaded insert that allows for a 6mm grub screw to engage in the machined flat on the drill to stop it revolving. The other hose fittings in the photo allow for switching off the air supply.

And yes, it does seem to work - with no air leaking after I attach the air-line.
I've not tried it out in earnest yet, as I have been under a workshop ban for the last fortnight, owing to cataract surgery.

 

[ChaiLatte]

The yellow dimple on the top contains a brass, threaded insert that allows for a 6mm grub screw

Could I make a minor observation on this please?

It might pay you to file down the grubscrew so its head does not project above the surface of the yellow recess.

My thinking is that if it ever slips in your hand and spins, there is less chance of laceration with a flush head to the grubscrew.

 

[niall Y]

Could I make a minor observation on this please?

It might pay you to file down the grubscrew so its head does not project above the surface of the yellow recess.

My thinking is that if it ever slips in your hand and spins, there is less chance of laceration with a flush head to the grubscrew.

Well spotted that man... In fact, I already have some shorter ones on order, as this screw at 12mm long is obviously too big. What it did have going for it though, was that it was in my stash and to hand.