Is it OK to ream 10.5mm into a 10mm hole?

[student123]

Ok guys, having ditched my first try, I'm having another another novice attempt to build a small oscillator.
Preparing to drill a piece of ali 1" square x 2" long for the cylinder bore.
I'm told it's 'machine grade' ali. I intend to drill all the way through & later cap then cylinder end. Using a Taig lathe. I dont have a long enough boring bar to bore through.

I do have my one & only chucking reamer, which is 10.5mm, so that'll be the bore. I couldnt find a 2/5" drill bit to pre drill, so the new plan is to drill a hole with a 10mm bit and then use a needle file to increase the bore to say 10.25 mm ,before using the reamer.

Or... can I dispense with the filing, drill the 10mm hole , then just use the 10.5 mm reamer straight away?

Any alternative strategies welcome.

Mike

 

[Blogwitch]

Mike,

It is a little much to expect to remove that amount of material, but what the heck, if that is all you have available, the chucking reamer should have a fair cutting taper on the end, and if you take your time, it should easily cope. I personally would use plenty of lube, either parafin (kerosene) or WD40 and just take it very steady.

Don't try to open the hole out other than with a drill, as a reamer will follow the hole, and if you hand cut, it just might not be good enough for the reamer to follow correctly.

You are going thru what we all had to, it is called the learning process, and even if you have a failure, even that will teach you something, even if it is 'don't do it that way again'. Eventually you will get less failures and more successes, that is when you start to really enjoy yourself.

Good luck.

Bogs

 

[steamer]

Mike,

An alternative to your approach would be to make a boring bar. That way you can straighten up the hole after drilling but before reaming

Doing the correct way now will save work and aggravation later when fitting the piston as the hole will be straight and there will be much less binding on your crankshaft......flat, square and parallel have as much to do with a good running engine as size does........

Anyway, that's what I would do....good luck to you! stop back if you want some help

Dave

 

[jirik92]

I think 0.5mm is too much for reamer. I usually drill hole about 0.2mm smaller then reamer.

 

[Deanofid]

Student, there are no regular drill sizes in 2/5". 13/32" is a standard drill bit size, though, and will probably do to get you close to 10.5 mm. Then you can ream it.

Otherwise, do what John Bogs says. It's a bit too much of a cut for that reamer, but it should do it in aluminum.

 

[student123]

Thanks guys.
I had priced up a 13/32 bit, it was £10 at my local toolstore, which seemed expensive for a one-off use. I've now checked online & can see them for £2 + postage. So I'll just buy one.
Dave, appreciate the suggestion, I just have this paronoia that in aweek fom now I would be posting a 'can't make a boring bar problem', to get a reply "well Mike , to get round that difficulty, you need to make a ..." !
The 'flat, square and parallel' is good advice & is taken on board.

I've been wrestling with milling today, hit problems, so haven't drilled the cylinder bore yet. Have successfully done my first fly cutting.

Mike

 

[steamer]

No worries Mike. As Bogs has stated...it will work....I am just concerned it will end up following a non straight hole.....that's about all drills can be counted on doing is make a hole....just sometimes it's not where you want it.

I have attached a photo for you.

A boring bar I made to make a .354-10 acme thread for a cross slide feed screw.

The bar came from a mechanical adding machine...the screw is 4-40.

The bit is in a close fitting drilled hole. The bit if mounted perpendicular to the bar and consists of broken center drill. ( You keep all your broken bits right?)

I reground the end to a threading tool, but it could also be easily modified into a small boring tool.....the starting hole was 1/4"....the bar is .187" diameter.

If that helps great....either way I wish you the best...good luck to you!

Sincerely,

Dave
http://i164.photobucket.com/albums/u27/mcandrew1894/P1010117.jpg

 

[kf2qd]

10.5 mm = 0.413"
10 mm = 0.393"

that 0.020" difference and I typically drill 1/64 or 0.015 smaller that the reamer size. It is a little tighter but not out of line.

 

[justlesh]

I agree, not out of line at all, If you were to be working with a hole much smaller it might be too much. Just work slowly and clean out often, ream a little, back it out, clean reamer and hole, go a little more. My point is the flutes will load up quicker and that is the potiential problem. Hope this helps
Les Holt