Drilling 1-11/16” hole 14” deep

[Martin w]

I need to accurately drill 250 1-11/16” diameter holes 14 inches deep in the end of composite 4x4 posts for a local attraction.
I have done a prototype but I can only drill 11” deep. That’s the flute length f the drill.
My question is. I have a two flute spade bit but no insert. If I bought the proper size spade insert, would it cut composite pvc? It’s about $90 bucks. Normally these inserts are for harder materials .Or should I just buy an extra length twist drill. About $350 dollars.Or should I cut my drill and add 3” to the middle near the Morse Taper. I have done this before with good results. The only thing is it fits perfectly now and if I cut and weld it back together and have any runout , the hole will be too sloppy.
The material drills like butter. So there isn’t much stress on the drill.
I have a smaller longer drill that will work, but I would need to bore to size with a boring bar. This is too time consuming.
Unless someone has an idea. I have 24” of quill travel on my boring mill but my existing drill will only drill 11” deep. I’m thinking just buy a new drill…
Martin

 

[quitereal]

How about a forstner plus extension?

https://a.co/d/4cCp5GM

 

[Martin w]

How about a forstner plus extension?

https://a.co/d/4cCp5GM

Thank you. I tried a Forstner and it drills too slow.it does work though. The twist drill drills the best so far..

 

[whydontu]

Why not just use the appropriate morse extension? Turn down the drill shank so there’s chip clearance at the end of the flutes.

https://www.amazon.ca/Extension-Morse-Taper-Drill-Sleeve/dp/B08RZ3D6Q8/ref=sr_1_7?crid=1V5TBO53M7GVX&dib=eyJ2IjoiMSJ9.XRhgyiJ7nm1Eip1SuRhgYe2-BSanTZtsrjIyFarw83U0rziTNie5hF5AMc-dWODPFmuGtPS0Xa5aohiPOOIFaf03GE9CWm4vIKSst-8vf9lEVXN1AvAkY2ask2cWxjCfkZARf91V-Un14OGgNuBF9SVHzJOufklieF-bxcYgy2nl-f23GHHUH5F040T6KyiuIOAzcizEtq7PfiR7q7KqEpjLVWB6Ot_-fJPD6X-M9Qvc3Hvkz54ChhSU5yBlOWbYfYfTJJZDrA0ynK2tCpB1u0ucPT9sZcyWRK60rsVwxwNkgVeMiG1vWv2WqYOOj5zdx-za1n9CNyxjWLHn2b4rLBRwqM2xKLt0G_N75BLOvBOMC8kYQvoAx_zzuSkSXHo2C3FDyCGfwJdbsiey5l9LtERzMt96Hf6HL62myDAEpMQ0gGTkdTogTXFsSSx9mDVQ.-0AozVTrPl68sOaFpF7Wzo_sc6PK0VKS159PA-wuV-A&dib_tag=se&keywords=morse+extension&qid=1741231671&sprefix=morse+extension%2Caps%2C158&sr=8-7

 

[justin1]

I need to accurately drill 250 1-11/16” diameter holes 14 inches deep in the end of composite 4x4 posts for a local attraction.
I have done a prototype but I can only drill 11” deep.

My buddy drilled out a hole 30" deep 2 inches wide with drill bits with extensions then we made custom deep hole boring head to finish hole out to tomato paste can size. So I think using a small extension would probly work fine for what your doing and if it's good quality should be pretty accurate and rigid if it's Morse tape extension.

 

[Susquatch]

I have used spade bits with hex extensions and they work ok - especially if you drill up instead of down.

However, I personally like those big drills they use to drill logs for big wooden pins in log construction. You can drill in any direction and the drilled hole stays straight for very long distances - even through knots.

https://a.co/d/8NiR4DU

 

[Martin w]

Thanks for the replies. All great ideas. Whydontu , I will have to try and find a MT5 to MT5 that is fairly reasonable or even used. Graingers is $368.00 I may as well buy the drill at this point. There has to be a Canadian supplier that has one cheaper. I will research, Thank you
Susquatch, I have never seen an auger bit larger than 1-1/2" diameter. I will have to research this. Thank you

Martin

 

[Dan Dubeau]

I would have recommended Irwin speed bore bits with an extension, but I can't find them in 1 11/16" size....I will admit that I first read it as 1 1/16 due to coffee deficiency.....Couldn't find that size either lol.

With 250 to do, there's enough there to justify making or modifying a tool. If you spliced in an extension, use tenons to better your chances of maintaining concentricity. Might give you a fighting chance. Alternatively you might be able to grind/turn down the mt5 taper to mt4, and then make an extension. The mt4 being smaller will allow for room for an extension smaller than the holes dia, and not kill the drill for future use. Or you could do the same and turn it into a straight shank. Making an extension would be easier, but effectively buries the drill with this project. A big drill like that isn't cheap, and I'm thinking like a home shopper on a budget. If there's $$ in this project, just burn it and charge for it .

In any case, that last 3" will be annoying with all the short pecking to clear chips. Doesn't sound like fun, but at least with 250 you'll get into a good rhythm and develop a system by the end.... lol. Turning the shank down behind the flutes it a good suggestion. I've done it before on silver and demming drills. Just be carefull you don't go too deep without a full clear, as chips can pack and bind up behind the drill and then you're in for a fun time.....Not sure how that composite stuff is at chip welding, so be carefull you don't entomb the drill....

Reading back to your post again, just buying an insert for the spade drill might be the best path forward here. I'm sure it'll cut fine, but if it drills big or not very good you could drill them all with the twist for fit down to 11", then use the spade to finish off the bottom as it might clear chips much better. $90 seems like a cheap way to buy time here. Even if the spade drill might drill big you could shove it down while it's off, then drill and retract off again, and it won't waller out your hole and fit. The soft material won't care, or wreck the insert on the way in/out. I don't think the spade would drill oversize though, but something to keep in mind. Having to handle them all twice is sometimes a quicker way to process parts in stages vs tool changing. It's annoying though.

 

[Dan Dubeau]

Just did a quick marketplace search and this guy has a 1 11/16 drill for $50. Not far from you either. It's a short one, but you could turn down the shank behind the flutes for clearance, turn a straight shank to 3/4, and braze/silver solder on a 1" od extension that provides lots of side clearance for chip evac. Drill with your current drill down to 11", then toss this guy in and finish the rest to depth. This might be the cheapest/quickest way forward.
https://www.facebook.com/marketplace/item/2582018481996779/?ref=search&referral_code=null&referral_story_type=post&tracking=browse_serp:dd4c93bc-68be-469c-8f7e-26adea7ceb0c


Edit: I was all geared up to go out in the shop, now I've grabbed another coffee and am browsing marketplace again.....I might have a problem.....

 

[Susquatch]

Also look at Freud Diablo, Irwin Speed Drills, or any 1-11/16 auger with a hex drive. Then get a hex extension to make it 14" or more.

https://a.co/d/0qnHbqN

I've used these to drill through layered beams for wiring and water lines and they work really well.

And position the work so you have to drill up into it to improve chip clearing by gravity. They sell them with 3 & 4 flutes which might make smaller chips - I don't know.....

Any chance you can re-engineer the job?

Who really needs a 14" long hole in wood?

Why not a more common 1-1/2? etc etc.

 

[Martin w]

Why not a more common 1-1/2? etc etc

They are bolting a stainless flange to the concrete with this 1-11-16” sleeve that slides over and is keyed from the side to prevent turning or removal. These parts are already made. They came to me because their maintenance staff knew I had a mill big enough to drill this deep.
Martin

 

[Martin w]

Just did a quick marketplace search and this guy has a 1 11/16 drill for $50. Not far from you either. It's a short one, but you could turn down the shank behind the flutes for clearance, turn a straight shank to 3/4, and braze/silver solder on a 1" od extension that provides lots of side clearance for chip evac. Drill with your current drill down to 11", then toss this guy in and finish the rest to depth. This might be the cheapest/quickest way forward.
https://www.facebook.com/marketplace/item/2582018481996779/?ref=search&referral_code=null&referral_story_type=post&tracking=browse_serp:dd4c93bc-68be-469c-8f7e-26adea7ceb0c
View attachment 61004

Edit: I was all geared up to go out in the shop, now I've grabbed another coffee and am browsing marketplace again.....I might have a problem.....

I can use the high speed spindle instead because it is #4 MT but most drills this big are MT5.
I saw those drills the other day. I have drills here the same. At this point and to make it easier. They have offered just to buy the longer drill. KBC has them for around $300.00 but I am trying to use a Canadian distributor. KBC has stores in Canada so it’s not the end of the world I guess. Just trying to do my part with Canada
Martin

 

[Dan Dubeau]

That's a nice easy solution. Hopefully it's easy drilling from here on out. Sometimes buying the (seemingly) expensive tool turns out to be the cheapest option in the end. The game is different when it's my home shop tied to my wallet, vs at work with somebody else's.....

 

[Martin w]

Having to handle them all twice is sometimes a quicker way to process parts in stages vs tool changing. It's annoying though.

Thanks for all your ideas. Very much appreciated. Yeah I would like to just clamp to the table and angle plate and drill and be done. These things probably weigh 25 pounds each.
I just found out a little bit of play is good as they are using PL Premium when they install, so that will let the glue flow easier
Martin

 

[Dan Dubeau]

Ya, a little bit of play is probably appreciated both for the adhesive to work properly, and to allow for some alignment in assembly. It's always hard to turn off machinist brain when doing construction projects sometimes

 

[CWret]

Or should I cut my drill and add 3” to the middle near the Morse Taper. I have done this before with good results. The only thing is it fits perfectly now and if I cut and weld it back together and have any runout , the hole will be too sloppy.

I’d go with the cut / extend / weld.

Have a look at how I welded threaded rod to a motor shaft and corrected runout to an acceptable amount. I just posted this thread:


PS:
OOOOPS - sorry guys - I didn't want to copy the whole thread and have it appear here. I was only intending to insert a link, but the most of it is attached - well the pictures anyhow. The text didn't come along for the ride. So to see the story go to my "Fixes and Repairs" thread. Maybe a smart guy would tell me how to do that or what I did wrong?

Thread 'Adding (welding) threaded rod to a splined motor shaft'

Thursday at 10:10 AM

Here’s an old motor that is now a buffer/polisher. Threaded rod was welded to the splined shaft to secure a buffer disc or wire wheel.

In pic below, the threaded rod extension is clamped on and aligned by using a piece of angle:

The indicator is set up on a bushing to check runout. A weight was hung from the bushing set screw threaded hole so that the bushing did not rotate with the shaft.


Weld access was improved by using bushings as spacers:


After welding, shaft runout was 0.035” at the end of the 8” long threaded...

• CWret

• 

 

[mbond]

That's a good clamping method for welding