hole size for tight fit

[pgrbffParticipant @pgrbff]

I need to drill a hole through a bar that will be a tight fit on a 6mm motor shaft. Will a 6mm shaft go into a 6mm hole drilled on the lathe? The shaft will be secured using a grub screw.

[pgrbffParticipant @pgrbff]

[JasonBModerator @jasonb]

Boring would be best using a small boring bar, reaming next option down, then plunging with a slot drill and finally at the bottom of the list drilling.

 

Have you actually checked the shaft, it may be a nominal 6.00mm but actuallly measure a bit less.

 

J

[pgrbffParticipant @pgrbff]

I dont have it yet. will wait and see. Hope boring bar not too expensive!

Thanks

[Clive HartlandParticipant @clivehartland94829]

At the size of 6mm then a reamered hole is fine. The grubscrews (two) should be placed at 90 degrees apart.

If cone point then dimple the shaft.

This is the way its done on the Theodolites I work on.

 

Clive

[pgrbffParticipant @pgrbff]

Can I use a hand reamer on the lathe? Or is it better to remove the item and hand ream after drilling?

[Gordon WParticipant @gordonw]

Check the motor shaft dia. first. If it is 6mm, drill 5.5mm, then 6mm, should be good enough for your use. You don’t need a good reamed finish, just an accurate hole.

[adyParticipant @ady]

I’ve read that if you stone the “wings” at the outer cutting edges of a drill tip this desharpens and stops the flutes “opening out” as drilling progresses, and gives a more accurate hole.

 

I’ve only needed to try it seriously once and it made the drill a tight fit as it drilled the hole, so oil is definitely recommended, even for a short hole.

 

[PatParticipant @pat]

Simply use a hand reamer having pre drilled the hole under size. Use the tapered portion of the reamer to slowly open up the hole trying the fit on the motor shaft as you go. Stop when the motor shaft just enters the hole being reamed being careful to ignore and radius on the end of the motor shaft. The small taper on the hole should ensure a nice press fit.

 

Use the hand reamer not a machine one in the lathe tail stock chuck is ok but turn the work by hand not under power as you only want to remove a smidgen of metal. I would use ‘Locktite’ or similar rather than grub screws unless removal at some future date is envisaged. as this will not add extra out of balance to the motor shaft.

 

Do not use a taper reamer as these are designed for use with matching taper pins not to bring the hole to a dead size. Check the motor shaft size against the reamer’s designated size as the motor shaft may already be under size to suit stock pulleys etc.

 

Regards – Pat

 

PS a boring bar for a 6mm hole is very delicate. 

Edited By Pat on 04/08/2011 10:34:10

[pgrbffParticipant @pgrbff]

The only other question is a general one on brands and quality. I’m not sure I’m allowed to ask but as these tools will probably only be used once, I don’t often need to do any machining but have a lathe and mill at my disposal, I would prefer not to spend a fortune. Are brands like Festo, Guhring and Dormer, which I have often seen, good enough quality for what I need to do?

I would normally buy the best I can afford, but when it’s only going to be used once it can get very expesive.

[David Clark 13Participant @davidclark13]

Guhring is top quality.

Dormer is ok, I once broke a dormer tap and using a carbide drill to remove the tap, it drilled like it was butter.

Not familiar with Festo.

regards David

 

[Phil PParticipant @philp]

I think he may mean “Presto”

 

Phil

[pgrbffParticipant @pgrbff]

I do, I mean Presto, Festo are woodwoking. Presto any good? Better or worse than Dormer?

[Roderick JenkinsParticipant @roderickjenkins93242]

As an amateur I would regard Presto and Dormer as premium brands. For the tasks mentioned in this thread, the lower cost imported tools as sold by the advertisers on this web site will, I am sure, be perfectly satisfactory.

 

Rod

[David Clark 13Participant @davidclark13]

Presto used to be ok.

Not used them for 30+ years.

regards David

 

[HasBeanParticipant @hasbean]

Try Here , always found them very helpfull (usual disclaimer etc)

 

Paul

[pgrbffParticipant @pgrbff]

Thank you all for your help.

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