Elmer's 43 "Build" Questions

[crueby]

Drilling alone will tend to give a slightly non-round hole, but as you say if a bearing will be there, that should be okay. If you have a boring head, drilling a size down and finishing with the boring head is another option in cases like that. For making bearings, I usually turn the on the lathe, drilling small and boring out with a small boring bar to size, that guarantees that the hole is concentric with the outside of the bearing, and is round.
 

[Bear]

Thanks, crueby. I like the boring head idea; however, I don't have one, but have been meaning to get one  ; looking at the Taig or Sherline. I will definitely be doing the bearing on the lathe.

[Bear]

How about I use a 3/8" end mill instead of a drill? I would think, correct me if wrong, that the end mill would be more accurate than a drill. Maybe I would want to start with a 1/4" drill then end mill?? 

[crueby]

Big risk of chatter that way, enlarging the hole. Can work with a very rigid machine, risky with smaller machines. Better to drill smaller and go up one drill size at a time, especially if you have numbered and fractional drills.

[Bear]

Thank's. I think I will just proceed with the incremental drill sizes like you say.

[crueby]

Its the kind of thing that is worth experimenting with if you have any scrap bits of the plate. Great way to learn alternative methods and figure out speeds and feed rates. There are almost always multiple ways to do any shaping.


When plunge cutting with end mills, check to see if it is a center cutting cutter, some don't have cutting edges right to the middle of the end, so would need a pilot hole.


 

[Bear]

Good points, crueby. I did look at Jim's build thread for the same engine, and he used a reamer for this 3/8" hole.  I will check prices on the 3/8" reamers. Thank's again.

[Jasonb]

If you can drill it 1/64 down then a 3/8" milling cutter will take no more off than a reamer so should be minimal risk of chatter, just run slowly. really depends if you have a 1/64th increment drill set.

[Flyboy Jim]

Good points, crueby. I did look at Jim's build thread for the same engine, and he used a reamer for this 3/8" hole.  I will check prices on the 3/8" reamers. Thank's again.

My thought on tool purchases is that if I need something once...........I'm going to need it again in the future. 

Jim

[Bear]

Thank's, Jason and Jim. I will check my drill inventory, and I did check the price on a reamer; not as bad as I thought it would be.

[Bear]

Good news  . I ordered the 3/8" reamer from Little Machine Shop at a very good price. By the way, the customer service there is excellent. If history repeats itself, I should have it in 2 days.

In the meantime, I may do some lathe work for the enngine so as to not mess with my mill set-up.

[Bear]

Should be receiving my 3/8" reamer any minute now. Problem is that I don't have the right size drill if I want 2% left. Calls for a 9.25mm drill that I ordered but is not scheduled to arrive until next week. The strange part that is related to the question I am about to pose is that if I do a 3% hole, the measurement is .36375". Online charts I have looked at show this dimension; but also show a drill size of 23/64" (which I do have). The 23/64" decimal size is only .3594", which is about 4%.

Can anyone tell me whether 4% is okay for aluminum? I thought I read  that holes should be pre-drilled for reamers for 2% to 3% material left.

What would you do? Wait for the 9.25mm drill or proceed with the 23/64" drill  ?

[Admiral_dk]

I have never really seen any metric drill bits with 0.05 mm. 'resolution' 

The common as muck ones are in 0.5 mm. steps and the finer steps are 0.1 mm. wich I would think would be close enough for Rock'n'Roll 

[Kim]

I've frequently used drills that are 1/64th larger than the reamer as a starting hole.  It may not be ideal, but it has worked for me.  I'd say you'll have no trouble with that in either aluminum or brass.

Others please feel free to correct me if you disagree.
Kim

[Jo]

Should be receiving my 3/8" reamer any minute now. Problem is that I don't have the right size drill if I want 2% left. Calls for a 9.25mm drill that I ordered but is not scheduled to arrive until next week. ...

What would you do? Wait for the 9.25mm drill or proceed with the 23/64" drill  ?

Use the 23/64th drill.

I was unaware of the 2% rule  I just use a drill that is undersized by a bit. So for a 4.76mm reamer (3/16"  )  I would use a 4.5mm drill  and for a 3.18 (1/8th ) I would use a 3mm . So they equate to even bigger percentage wise than your 23/64th drill. Most of the larger imperial stuff I just use the next 64th size smaller than the reamer.

And run the reamer slower than the drill - a lot slower.

Jo