Drilling very long holes

[WindyParticipant @windy30762]

Am wondering what would be the best way to drill a 6mm hole 350mm long in a spindle of en24t.

Could possibly go up to 8mm diameter hole but prefer 6mm.

I would normally braze a drill onto some rod to extend it and maybe drill from both ends to meet in the middle.

With the length involved am worried about the drill wandering off centre.

A push rod has to go down this long hole.

What would be the best way to do this please.

[WindyParticipant @windy30762]

Drilling very long holes

[Rik ShawParticipant @rikshaw]

Not cheap but this should do the job if drilled from both ends. Alternatively, I have seen precision tubing that would be a better bet. Depending on the OD of your spindle you may / may not have to turn down the OD.

Rik

https://www.ebay.co.uk/itm/6mm-Gun-Drill-Carbide-Tipped-16mm-Shank-6mm-x-180mm-x-230mm-SVIK-428-9-06-GS26/264651957407?hash=item3d9e7c649f:g:nUcAAOSwxaNeSuht

 

 

Edited By Rik Shaw on 12/06/2020 00:44:11

[HopperParticipant @hopper]

Yes gunsmithing is definitely the place to look for such long thin holes. The US forums are more oriented that way and msy have more info on tricks of the trade.

[pgk pgkParticipant @pgkpgk17461]

Joe Pieczynski produced a vid on deep hole drilling recently Link

pgk

[Ady1Participant @ady1]

Just did a 200mm x 5mm one a week or two ago in 40mm steel

Came in from each end and it was slightly out for a push rod so will have to ream the middle

Take your time and use good drills and plenty of lube and lots of clearing out, swarf is your enemy

You can HEAR and feel by hand if a long drill is going on the wander, you can also test them by eye before drilling since the point and shaft should be rock steady when it spins and you should be able to spin the inserted drill with your fingers with minimal resistance

I used a 6mm mill to flatten the spindle face, then a 7mm long spot for a good start, then a good normal size, then a good extended drill

Will hunt for a long 5mm file to ream gently

Always a bit twitchy when that eureka moment is coming, even if you know its gone well

350 mm is a lot, lol

GL

Edited By Ady1 on 12/06/2020 07:30:42

[Ady1Participant @ady1]

on that video at 24,50 the chap is using some sort of D cutter made of round hss or silver steel which would give you a fabulously straight start to a long hole

A good metal will make things much much easier to drill, all my stuff is scrap-crap like building site rebar

Edited By Ady1 on 12/06/2020 07:44:18

[not done it yetParticipant @notdoneityet]

Unless there are overwhelming reasons for this, why not simply braze (or other) locating ends on a piece of suitable thin-walled pipe?

[old martParticipant @oldmart]

It is possible to buy thick walled steel tube, which might be cheaper than the cost of tools to drill a deep hole.

If you do your own drilling, then get quality new drills and drill both ends with a jobber, then switch to long series. If that is not enough, then think of attaching the jobber to an extension for the last bit. You might benefit from drilling 1/4" which will give a bit of leeway in the event of a mismatch. The whole job will take some time as you will have to clear the swarf every 6mm or so.

Edited By old mart on 12/06/2020 13:28:01

[Oily RagParticipant @oilyrag]

Did a similar deep hole drilling by using a carbide 'de Frise' cutter mounted onto a silver steel shank. The shank was milled to allow for a drain gulley to get the swarf out from the work area and the cutter was modified to extend the flat out to meet the shank gulley, We silver soldered the de Frise cutter into the SS shank but ground the cutter to give a spigot location to ensure concentricity. The de Frise cutter had a coolant delivery hole in it and this then had to be extended to join up with a delivery system in the shank! So we needed to drill a deep hole in the tool that was going to drill a deep hole! Hang on this is getting silly…… Right lets put a gulley on the shank opposite the drain gulley and feed the coolant down that. We then had to make a collar to feed the coolant into the tool and this was relatively easy to achieve and worked really well. I may have some pictures of the job – it was pretty straight forward to do this tooling. I was fortunate that I happened to have a de Frise cutter of the right size available.

The deep hole was 8mm dia x 450mm deep,

[WindyParticipant @windy30762]

Oily Rag

I like your way can you tell me what a de Frise cutter looks like went on the web but could just find ordinary cutters

[Oily RagParticipant @oilyrag]

Just as a scraper is a single 'tooth' file so a de Frise cutter is a single tooth straight fluted reamer but is also a 'D' bit cutter as well.

I served my apprenticeship at Alfred Herbert Machine Tools in the 1960's and when we wanted to cut an accurate slot we always used a de Frise cutter – spiral multi flute cutters always twisted and cut slots oversize if a cut was taken in both directions – the de Frise cutter overcame that problem. The spiral slot drills and end mills have come on a long way in the last 50 odd years.

I have a few de Frise cutters in the proverbial tin somewhere – I'll dig one out and photograph it for you. For the hassle I think the gun drill which Rik linked to on fleabay would definitely be the way to go.

[colin vercoeParticipant @colinvercoe57719]

You could use a Gun drill bit, not really a depth limit with these bits, at the firm I used to work we drilled 10mm dia 700mm deep in stainless steel plate with cutting oil fed down through the bit this was in one cut without retracting the bit as the chips are ejected along the flute of the drill bit by the coolant . You can also use compressed air with misted coolant as a cutting medium again the compressed air ejects the chips along the flute of the drill bit and also cools and lubricates the cutting area, again very good results try Sterling Gun Drills, or Mollart Gun Drills, if they are still going

[JohnFParticipant @johnf59703]

Windy does it have to be EN25T ? if not consider seamless hydraulic tubing easily available in various bore and wall thickness sizes. I have use this material to extend honing tools up to 35" long.

John

Edited By JohnF on 13/06/2020 12:32:30

[JohnFParticipant @johnf59703]

Posted by JohnF on 13/06/2020 12:22:26:

Windy does it have to be EN25T ? if not consider seamless hydraulic tubing easily available in various bore and wall thickness sizes. I have use this material to extend honing tools up to 35" long.

John

Edited By JohnF on 13/06/2020 12:32:30

Just had a look at what I used and it was 5/8" OD 5/16" bore so you would need to look whats available and if it suits you.

[Bo’sunParticipant @bosun58570]

Good afternoon Windy,

If EN24t isn't critical, it might be worth trying thses guys.

**LINK**

[WindyParticipant @windy30762]

This spindle has a lot of torque to contend with the largest diameter on it is 48mm going down to 35mm with various tapers and threads on it.

Gun drilling had been mentioned to me will probably make a tool up.

One of my ME club members gave a talk on his gun making and the barrel boring and rifling was discussed many of his tools he made himself.

I just remembered I had on disc and my PC 2 volumes of the Modern Gunsmith with other copies of pre-war gun making books.

True hand skills being shown such an interesting read for a do-it-yourself tinkerer.

Thanks for the advice it's always welcome.

 

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