Incorrectly tapped hole

[krw]

I recently bought a lathe. Part of the promotion was an LED light. I just received the light. Wanting to mount it on the headstock, I found the holes in the headstock are incorrectly tapped. The mounting location on the tailstock are correct. I really don't want it on the tailstock.

The incorrect holes are drilled/tapped M3.5x.35mm. They should be M4x.70. M3.5X.35 is a "standard" M3.5 fine thread but these things are unicorns. I haven't found them anywhere, including Amazon, Grainger, Bolt Depot, and Fastenal.

I've sent the manufacturer an email but have heard nothing. I sent one with pictures of the problem but it bounced (images are rather large, so understandable). I resent it without the pictures. Anyway.

1) How to correct? a) The difference in diameter is less than the thread depth so retapping to M4x.70 doesn't seem to be an option. b) An M5 screw doesn't fit through the lamp holes. c) M3.5x.35 is a "standard" M3.5 Fine thread but they're unicorns. I've checked Amazon, Grainger, Bolt Depot, and Fastenal. No joy. d) The bracket is cast iron and also holds the spindle copying fixture and is quite complicated. Copying it wouldn't be a simple matter.

2) How the hell does this happen? Aren't these things made with CNC tools? Both the drill and tap were loaded wrong? As far as I know there aren't isn't any other M3.5 hardware on the lathe.

I'm not really optimistic that the manufacturer is going to answer anytime soon. Two months after I bought the lathe I called to find out where the promotional lamp kit was. I got no answer. The customer support number on the paperwork had been disconnected. Another number on the web site had a message that the phonemail inbox was full. I don't remember how I finally got a message through but a week or two later I got a call from Woodcraft corporate office (I bought the lathe at a local store). Maybe I'll get another call from Woodcraft in a couple of weeks. This wasn't a cheap tool. Not happy but amazed at how this could happen.

[Bill]

People with small metal lathes "live for" problems like this. You could go to hobby-machinist.com and see if their "resources" may direct you to a bolt source. I feel reasonably confident that someone there can point you to the right source (do a search first)--though you are likely to get "Grainger pricing". If for any reason you are not successful, someone may possibly even be willing to make some for you. There are some very kind people there just as there are some very kind people here. I'm sorry I don't own a metal lathe (but maybe someday). I hope this is helpful.

- Bill

[Sonny]

Have you looked at McMaster-Carr website? Left menu - select what you're looking for, see what they have.

Sonny

[Bob La Londe]

A quick check shows a 3.5 hole will give you 53% thread form for an M4 thread. 75 would be better in cast iiron or aluminum, but 53% will hold just fine if you don't act like a wanker with a spanner. Knock yourself out and drill and retap it. Problem solved.

[Joe Gwinn]

Or, drill and tap for a M4 helicoil.

Joe Gwinn

[krw]

Yeah, I looked there too. They really are unicorns.

[krw]

Now there's an idea! Thanks. I'll find some as a backup.

[krw]

I don't care much about "Grainger" pricing (though IME they're really bad). I only need four screws.

[Bill]

Don't write-off hobby-machinist.com too fast. I know someone there (who I have never met in real life) who I feel quite confident is up to this task. He works around real machinists by day. There is also a "big brother" website for hobby-machinist, I forget the name offhand, but it is not hard to find. If you can provide a specification for exactly what you want (and it sounds like you are close to that already), then someone can will surely be able to make it. An amateur may be willing to do it cheap. To a machinist, a specification is like a contract, and it shows that you don't want to waste his or her time.

[Bob La Londe]

I don't care for Grainger as a company, but sometimes if they are the only one who has what I need I have to swallow my pride, dignity, and self respect. No I don't. If they are the only one who has a screw I need I'll make one instead.

P.S. Zoro is Grainger.

Usually McMaster Carr has screw and bolt needs covered. Sometimes I also check Bolt Depot.

I didn't check to see if they have the thread pitch you need, but they do have a lot of M3.5 machine screws. Ok... the common pitch for M3.5 is .600. M3 has a commmon pitch of .350

[krw]

I don't have any metal working tools and I'm really not much interested. Welding might be some fun but I can't play in that sandbox.

I needed 50 1/2 x 3-1/3" carriage bolts, nuts, and washers earlier this year. Bolt Depot was less than half the cost of McMaster and Grainger was simply on drugs.

Yeah, the .35 thread is the standard "fine" thread but no one seems to use it. "Standard" my foot.

[krw]

I'll give them a chance to make it right but my email to their customer service was bounced again today. I meant to call this afternoon but got busy doing something else.

[Bill]

If you find one that's too long, you could always cut it off, and touch up the threads as necessary.

[Brian Welch]

Little trick, of which I'm sure most of you are aware, thread a nut on before cutting/shortening the fastener. Removing the nut afterwards helps straighten/correct any threads slightly damaged during the cutting process...

[DerbyDad03]

He hasn't even found the bolts yet. Now you've got him looking for nuts too! ;-)

[krw]

I don't even need the nuts.

[Bill]

Have you tried to reach out to any machinists yet?

[Brian Welch]

Iffn you're going to consider cutting a bolt that's too long, a nut would be cheap insurance. Just a friendly suggestion... Best...

[krw]

Not yet. Trying the manufacturer again. I shouldn't have to go through this.

[krw]

If I could find a screw, perhaps I could find a nut to go along with it. ;-)