Hole How-To

D

Damn Yankee

H-M Supporter - Diamond Member
H-M Lifetime Diamond Member
Joined
Nov 30, 2022
Messages
105
Hi All, Hope I have the right forum...

I have both hands tied behind my back and need help. I purchased a mill and committed on the Precision Mathews of The Hobby-Machinist to document a novel way of implementing an auto Z-Axis feed which would include Plunge Milling (dependent on material hardness). Though I don't own a PM mill, I have a Weiss VML25-D - a kissing cousin with only slight differences so the project is relevant to both mills. My problems are:
  • The mill is a tabletop, 1 HP variable speed, so any hard/thick material is a challenge
  • It is the only machine shop tool I own (wish I had a lathe)
  • The hole diameter to material thickness ratio is heavy-duty
  • I am a Newb - think one project (successfully completed)
Then challenge is to create a 1.75" hole in the center of two 4" x4" x .5" aluminum flats and a 2.9" x .125" relief, concentric with the 1.75" hole in one of the flats (motor locator). With a lathe and 4-jaw chuck, even I could do this in say 1/2 hour - again, not an option. I do however have an 8" rotary table...

So, I ask for the 1.75" center hole in .5" aluminum:
  • Hole saw?
  • Spade bit?
  • Rotary table and end mill?
And for the .125" relief:
  • Rotary table and end mill?
  • I can think of no other option :(
Though I did not mention it, between the 4 x 4 plates sits a piece of 4 x 4 tubing. I would like to ease (radius) the corners along its length. Is the RT my only option and how do I clamp it???

Thanks for the ideas!

John
 
First, I'm going to assume you don't have a boring head, which would be the obvious way to do this in a mill.

My second choice would be rotab and endmill. You could cut the 1.75" hole a lot of ways, but that's just going to make your rotab setup more difficult and since you're going to have to do it for the relief cut might as well use the same setup. The only other option I can think of is some sort of trepanning tool.

The rotab is a good option for rounding corners as well, particularly if the radius you want allows you to drill the center of rotation in what will be waste material from your hole (in which case I would round corners first). If you can clamp a scrap plate to your rotab, you can install two reference surfaces at right angles right where they need to be to index your material for cutting the radii. Much easier that trying to knock something into alignment.

GsT
 
Make yourself a boring bar. Get a piece of round stock as big as that will fit in one of your holders. drill a hole near the end and file to fit a piece of HSS. Clamp with a set screw from the end. Grind a cutting edge on your HSS .
On your piece drill a hole as big as you safely can. Start making light passes with your newly made boring tool and extending your cutting tool until you have the size hole desired. Clear as mud ?


Martin
 
RT and EM is your best bet. As to clamping, can you supply a picture of the part so to be totally clear. Need to see if you got room to rotate part 360.

Because this is a light duty mill, taking the bulk of the material with a hole saw might be worthwhile.

For rounding the corner on a long lenght, there are chamfering end mills made for this task.

<edit> just seen post 3. This will work but lack of rigidity will be a big problem. Keep eveything as short and tight as you can.
 
Last edited:
Karl_T said:
RT and EM is your best bet. As to clamping, can you supply a picture of the part so to be totally clear. Need to see if you got room to rotate part 360.

Because this is a light duty mill, taking the bulk of the material with a hole saw might be worthwhile.

For rounding the corner on a long lenght, there are chamfering end mills made for this task.

<edit> just seen post 3. This will work but lack of rigidity will be a big problem. Keep eveything as short and tight as you can.
Click to expand...
The work that requires boring is 4" x 4" x 1/2" thick. I have an 8" table with 4 T-slots. I was thinking using step blocks and end clamps to hold it down. Sound reasonable? I guess I should get some 123 blocks to support it or is there a better solution?
 
If you want, go to the trouble of making stand off blocks. Start with say 1"x1" bar by the width of your table plus a bit more. Drill and counter sink several spots for an allen head bolt to fit your T nuts. Bolt them down and do a skin cut on the top of them so they are all EXACTLY the same height.

now you got very useful blocks for all your future projects. No big deal if you got to mill into them.

I have used these and milled pockets for oddball shaped parts.

PS. I made special T nuts to use 3/8 bolts for these. The bolt is smaller and takes less space that way.
 
Go buy a metal cutting hole saw.

Just under finish size.

Go as slow as mill will go with lots of oil.

That will get the Haledon an a slugger reuse.

Boring bar to finish size.

Sent from my SM-G781V using Tapatalk
 
tq60 said:
Go buy a metal cutting hole saw.

Just under finish size.

Go as slow as mill will go with lots of oil.

That will get the Haledon an a slugger reuse.

Boring bar to finish size.

Sent from my SM-G781V using Tapatalk
Click to expand...
This was the approach I thought - and have to buy nothing. The thought of once again using a hole saw in metal made me ask for alternatives. I have a love/hate relationship with hole saws (mostly hate). I still have to make the nearly 4" relief which will require the rotary table. Would drilling a hole and then milling the 1.75" out of the center be easier?
 
Karl_T said:
If you want, go to the trouble of making stand off blocks. Start with say 1"x1" bar by the width of your table plus a bit more. Drill and counter sink several spots for an allen head bolt to fit your T nuts. Bolt them down and do a skin cut on the top of them so they are all EXACTLY the same height.

now you got very useful blocks for all your future projects. No big deal if you got to mill into them.

I have used these and milled pockets for oddball shaped parts.

PS. I made special T nuts to use 3/8 bolts for these. The bolt is smaller and takes less space that way.
Click to expand...
Thanks for the idea... An EZ and inexpensive solution to space.
 
You must log in or register to reply here.
Back
Top