Model Engine Maker

Help! => Mistakes, muckups, and dangerous behaviour => Topic started by: Roger B on June 23, 2019, 08:07:50 PM

Title: Boring hole with a keyway
Post by: Roger B on June 23, 2019, 08:07:50 PM

I have some rescued imperial bevel gears I want to use for a differential. They are currently 3/8" bore and I want to open them out to 10mm. One has a 3mm keyway cut in it. Will I get away with boring to 9.8mm and then reaming or should I put something in the keyway to stop the reamer being deflected?

Title: Re: Boring hole with a keyway
Post by: Jasonb on June 23, 2019, 08:09:28 PM

I'd just pop it in the lathe and bore to size.

Title: Re: Boring hole with a keyway
Post by: b.lindsey on June 23, 2019, 08:15:21 PM

Agree with Jason here. Lights cuts also as you near the final desired bore as well.

Bill

Title: Re: Boring hole with a keyway
Post by: Vixen on June 23, 2019, 09:17:07 PM

Just don't spoil the bored hole by trying a straight flute reamer. It will pick up on the keyway and produce a washboard finish. A fast spiral reamer or three /four flute end mill may work better.

Mike

Title: Re: Boring hole with a keyway
Post by: Ramon Wilson on June 23, 2019, 10:04:18 PM

I'm with Jason and Bill here Roger definitely bore them  :ThumbsUp:

As Mike says you could make a real mess of the bore if you ream it (and, in all probability the reamer too :o)

Tug

Title: Re: Boring hole with a keyway
Post by: derekwarner on June 24, 2019, 12:23:42 AM

Just going backwards Roger.....both HSS or carbide will be prone to chip or breakage in such small sizing overcoming each contact/smash with the tool pressure against or into the open the  area of the keyway, then against the parent material

If they are currently 0.375" or 9.52 mm, is it possible to machine the shaft/s to suit the existing bore/s?

It seems wanting to increase the bore from 9.52 mm to 10 mm is clearly not a power transmission requirement

Derek

Title: Re: Boring hole with a keyway
Post by: Art K on June 24, 2019, 01:57:24 AM

Roger,
I'm with Bill and Jason on this you shouldn't have trouble with the interrupted cut & if you still need the/a keyway you can probably resize that as well.
Art

Title: Re: Boring hole with a keyway
Post by: Roger B on June 24, 2019, 08:43:25 AM

Thank you all for your inputs  :ThumbsUp:  :ThumbsUp:

I will probably just try boring to size with a HSS tool. My 10mm reamers are all quite shalow angle. The other 3 without keyways will be bored and reamed. Staying with 3/8" would mean buying a 3/8" reamer for the spider (not normally available here). As it is a 3mm keyway I can use my 3mm broach to correct the depth if need be (it already looks too deep).

Title: Re: Boring hole with a keyway
Post by: Roger B on June 24, 2019, 06:39:34 PM

Successfully bored  :)  :) I used the broach guide as a gauge (~9.98mm) and ended up with 10.02mm (as measured with a Vernier calliper). The keyway needed to be deepened by 4 teeth on the broach.

Title: Re: Boring hole with a keyway
Post by: Vixen on June 24, 2019, 07:17:27 PM

Nice one Roger :ThumbsUp: :ThumbsUp: :ThumbsUp:

Mike

Title: Re: Boring hole with a keyway
Post by: Ramon Wilson on June 24, 2019, 10:44:05 PM

Easy-Peasy eh? Roger  :D

Good result  :ThumbsUp: :ThumbsUp:

Tug

Title: Re: Boring hole with a keyway
Post by: b.lindsey on June 25, 2019, 02:29:29 PM

Well done Roger  :ThumbsUp:

Bill

Title: Re: Boring hole with a keyway
Post by: Jo on June 25, 2019, 02:46:56 PM

 8)

Jo