3/5 of an inch forstner bit?

[mike4244]

If it was just a couple, I might do that, but I have 56 sewing machines and several of them would be better in portable boxes when looking for a new home.

I have also thought of making a router jig that clamps to the box and use that to enlarge the hole, but if I can find or make a forstner type bit I think I will be better off not going through several steps to make the same hole.

I suppose the other option since I have several, is to program my CNC to do it.

Duke

Duke ,I did not realize how many holes you need to bore. Mc Master Carr has a .06 reamer that you use after boring an undersize hole.
The teamer is expensive , $70.00 without shipping. Might be worth it for you. Other wise have a machinist make a D bit for you.
Easy enough job for a home shop machinist. Do a search for D- bit and you will see how it looks. The D-bit is used like a reamer but has no flutes. 
Since .6 is close to 5/8" you may need to have the chuck end turned down to 1/2" or 3/8" . 
After boring  the hole with an undersize Forstner bit the D-bit bores the exact size. You may have to peck bore as the bit has no flutes. Experiment some , the closer the hole is to final size the easier it is to ream.
mike

[JDuke]

My initial thought would be an adjustable auger (do vintage, the new ones stink), but that wouldn't leave a perfectly flat bottom.

I did come across this however, https://toolstoday.com/carbide-tipped-ad..._s_jv9-9Ke

I may look at this if grinding a forstner bit to size doesn’t give good results.

Thank you for the idea, I didn’t know those bits existed.

[JDuke]

Duke ,I did not realize how many holes you need to bore. Mc Master Carr has a .06 reamer that you use after boring an undersize hole.
The teamer is expensive , $70.00 without shipping. Might be worth it for you. Other wise have a machinist make a D bit for you.
Easy enough job for a home shop machinist. Do a search for D- bit and you will see how it looks. The D-bit is used like a reamer but has no flutes. 
Since .6 is close to 5/8" you may need to have the chuck end turned down to 1/2" or 3/8" . 
After boring  the hole with an undersize Forstner bit the D-bit bores the exact size. You may have to peck bore as the bit has no flutes. Experiment some , the closer the hole is to final size the easier it is to ream.
mike

The D bit looks like a decent option if grinding a forstner bit down doesn’t work as well as I want.

I have a mill and lathe, and my son heat treats the knives that he makes, so we could probably make a D bit if we need to.

[JDuke]

End mills are available in 29/64 which is about .001 oversize.   Should work well in a drill press, mill or CNC.

Hadn’t thought of an end mill, Ill have to dig through my drawer of end mills and see if I have one just to test that idea out.

[JDuke]

By my calculation 19/32 is a little closer to the 3/5 or 0.6 inch that I am looking for.

With 19/32 being 0.59375 inches so about 7 thousandths under the 0.6 that I need.  I am willing to bet my drill press has enough run out to make that close enough to 0.6 for government work.

I am still going to grind a forstner bit down to see how it works, but I will keep the 19/32 end mill as a way to clean up the holes if the forstner bit isn’t satisfactory.

Thank you 

Duke

[kencombs]

By my calculation 19/32 is a little closer to the 3/5 or 0.6 inch that I am looking for.

With 19/32 being 0.59375 inches so about 7 thousandths under the 0.6 that I need.  I am willing to bet my drill press has enough run out to make that close enough to 0.6 for government work.

I am still going to grind a forstner bit down to see how it works, but I will keep the 19/32 end mill as a way to clean up the holes if the forstner bit isn’t satisfactory.

Thank you 

Duke

Your size may be correct.   I didn't calculate, just looked at the end mill size table at Mcmaster.com.  My go to place for odd stuff and info.

[museumguy]

Would this work? https://gavantools.com/products/15-2mm-d...GWtLwAOVKN

[Cabinet Monkey]

Duke ,I did not realize how many holes you need to bore. Mc Master Carr has a .06 reamer that you use after boring an undersize hole.
The teamer is expensive , $70.00 without shipping. Might be worth it for you. Other wise have a machinist make a D bit for you.
Easy enough job for a home shop machinist. Do a search for D- bit and you will see how it looks. The D-bit is used like a reamer but has no flutes. 

I may look at this if grinding a forstner bit to size doesn’t give good results.

The D bit looks like a decent option if grinding a forstner bit down doesn’t work as well as I want.
I have a mill and lathe, and my son heat treats the knives that he makes, so we could probably make a D bit if we need to.

Hadn’t thought of an end mill, Ill have to dig through my drawer of end mills and see if I have one just to test that idea out.

By my calculation 19/32 is a little closer to the 3/5 or 0.6 inch that I am looking for.
With 19/32 being 0.59375 inches so about 7 thousandths under the 0.6 that I need.  I am willing to bet my drill press has enough run out to make that close enough to 0.6 for government work.
I am still going to grind a forstner bit down to see how it works, but I will keep the 19/32 end mill as a way to clean up the holes if the forstner bit isn’t satisfactory.

Your size may be correct.   I didn't calculate, just looked at the end mill size table at Mcmaster.com.  My go to place for odd stuff and info.

why don't you just contact Vortex for a quote and get EXACTLY what you want/need  



think you you'll find it's not as expensive as you fear and I know it'll be faster and more accurate than any of these suggestions strewn about here

[JDuke]

The time for mental gymnastics was done.

I have metal working equipment for a reason, so I picked up a cheap air powered die grinder that easily chucked up on the QCTP of my metal lathe and ground a 16mm carbide forstner bit down to just a few thousandths more than the desired 0.60 inch mark.

Chucked up in my drill press the hole it drilled is a nice snug fit.

Perfect for what I need.

Thank you for all the suggestions.

Duke